Inherited nervous system disorders

Cervical vertebral instability (Wobbler syndrome)

roblib — Tue, 27 Apr 2010 19:36:01 +0000

What is ... ?:

In cervical vertebral instability, there is compression of the spinal cord in the neck (cervical) region. There are seven vertebrae in the neck which surround and protect the spinal cord. Movement between these bones allows normal movement of the neck. With this condition, there are abnormalities in the structure of the vertebrae, of the ligaments that connect them, and/or of the disks between them. The reasons for these abnormalities are not clear; inheritance is a factor, and overfeeding in rapidly-growing large breed dogs is also thought to play a role.
The result is instability between adjacent vertebrae, narrowing (stenosis) of the spinal canal, and pressure on the spinal cord. The consequences of compression of the spinal cord in the neck region are weakness and incoordination in all 4 legs - hence the name "wobbler".

How is ... inherited?:

Unknown. It has been suggested to be autosomal recessive in the Great Dane, Doberman pinscher, and borzoi.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

The main signs with this disease are weakness and incoordination (ataxia); these signs begin insidiously and worsen slowly over several months. It may look like your dog doesn't know where his or her feet are. This will be most obvious when s/he is rising from lying down, or negotiating a turn or stairs. Over time, your dog may develop a stiff, high-stepping, exaggerated gait that gradually worsens.

The signs are bilateral and symmetrical (meaning they occur equally on both sides). All 4 legs are eventually affected, with the hind legs affected first, and more severely. Sometimes there is a sudden change for the worse as a result of minor trauma. Doberman pinschers often experience severe neck pain (as a result of disk herniation- see intervertebral disk disease) and may develop rigid front legs.
This is a chronic, progressive disease (ie. it gets worse with time). Without treatment, your dog's condition will gradually deteriorate. With therapy (either medical management or surgery) the prospect for recovery remains guarded.

How is ... diagnosed?:

Your veterinarian will suspect this disease if your large-breed dog displays the characteristic clinical signs: slowly progressive, bilateral, symmetrical hind leg weakness and ataxia. The front legs are affected after the hind legs, and usually less severely. Your dog’s neck may be painful, and may be held flexed slightly downward. Plain x-rays are taken to show structural abnormalities in the vertebrae, but myelography is necessary to determine if there is spinal cord compression. In order to do a myelogram, your dog is anesthetized, dye is injected into the spinal canal, and x-rays are taken which will show the exact location(s) of spinal cord compression. This information is essential in considering treatment options, especially if surgical repair is to be attempted. Other imaging techniques, such as CT scans and MRI, may also be used. Your veterinarian may refer you to a veterinary referral centre for these specialized radiographic techniques, and for potential surgery.

How is ... treated?:

The type of treatment chosen for this condition will depend on a number of factors, including the severity and duration of your dog’s signs, and the extent of spinal cord compression apparent on radiography. The goals of medical management are to minimize neck movement (through confinement and use of a neck brace) and use anti-inflammatory medications to prevent further damage to the spinal cord. Medical management may be effective for weeks to years, although it does not address the underlying problem of spinal cord compression. A variety ofsurgical techniques have been developed (and more are being developed) which attempt to both alleviate the spinal cord compression and stabilize the vertebrae. Surgery is not without risk, including a variety of potentially severe postoperative complications. Ultimately, the prospects for recovery depend on a number of factors, including duration and severity of clinical signs, and whether the spinal cord is compressed at a single site or at multiple sites.

Because of the requirement for both specialized radiographic and surgical techniques in treating this condition, your veterinarian may provide initial neck stabilization and anti-inflammatory therapy for your dog, and then refer you to a veterinary referral centre for further treatment.

For the veterinarian:

The two most commonly affected breeds have characteristic lesions; older Doberman pinschers frequently show ventral spinal cord compression, while young Great Danes show dorsal spinal cord compression. Lesions are more common at the more caudal cervical segments (C5-6 and C6-7). Underlying systemic or metabolic diseases may also be present. "Traction" myelograms can be used to demonstrate the dynamic component of this disease (instability between vertebrae). Forced extension of the neck may exacerbate spinal cord compression.

Breeding advice:

Although the exact mechanism of inheritance is not known, dogs with cervical vertebral instability should not be bred. (Unfortunately, because this condition often has a later onset, dogs may be bred before any problems appear). It is best to avoid breeding their parents or siblings as well, who are considered potential carriers of the trait.

The best ways to avoid this condition in a large breed dog are to inquire before purchase if there is any family history of vertebral instability, to refrain from providing mineral supplements to the diet, and to feed several small meals daily (rather than ad libitum feeding).
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

LeCouteur RA, Child G. 1995. Diseases of the spinal cord. In EJ Ettinger and EC Feldman (eds) Textbook of Veterinary Internal Medicine, p. 629-696. WB Saunders Co, Toronto.

Cerebellar abiotrophy(ataxia)

roblib — Thu, 29 Apr 2010 15:37:40 +0000

What is ... ?:

The cerebellum is the part of the brain that regulates the control and coordination of movement. In this condition, cells in the cerebellum mature normally before birth, but then deteriorate prematurely causing clinical signs associated with poor coordination and lack of balance. The Purkinje cells are the cells in the cerebellum which are primarily involved; cells in other areas of the brain may also be affected.

How is ... inherited?:

Inheritance is autosomal recessive. The defective gene has been identified and causes a defect in glutamate metabolism. (For more information, see cerebellar abiotrophy Online Mendelian Inheritance in Animals (OMIA). Faculty of Veterinary Science, University of Sydney. 2011.

What does ... mean to your dog & you?:

Because the cerebellum regulates the control and coordination of voluntary movement, the clinical signs of cerebellar dysfunction may include poor balance, a wide-based stance (feet planted far apart), stiff or high-stepping gait, apparent lack of awareness of where the feet are (standing or walking with a foot knuckled over), and head or body tremors. Signs may appear at birth or later (as listed below) and worsen either quickly or slowly. Affected dogs may become unable to climb stairs or stand without support. They have normal mental alertness.
Where other regions of the brain are also affected, you may see signs such as behaviour change (loss of house training, aggression), confusion, blindness, and seizures.
Neonatal cerebellar abiotrophy (rare) - Affected cells start to degenerate before birth, so that signs of cerebellar dysfunction are present at birth or when the pup first walks - Beagle, samoyed
Early onset(birth to ~6 weeks): Airedale terrier, beagle, collie (rough), coton de tulear, Finnish harrier, Jack Russell terrier, Irish setter, miniature poodle, Rhodesian ridgeback, and samoyed.
Onset at 6 weeks to 6 month: Australian kelpie, Bernese mountain dog, border collie, bull mastiff, coton de tulear, Gordon setter, Kerry blue terrier, and Labrador retriever.
Later onset: Brittany spaniel, Gordon setter, old English sheepdog. Clinical signs progress slowly (months to years).

How is ... diagnosed?:

Typically, pups are normal at birth and then begin to develop signs consistent with cerebellar disease (as listed above) at varying ages, depending upon the breed. The diagnosis is based on the clinical signs, breed, and age of onset. Your veterinarian will also do tests to rule out other conditions that can cause similar signs. It is important to differentiate this disorder from cerebellar hypoplasia, which is a non-progressive disorder (ie., does not worsen over time).

How is ... treated?:

There is no treatment for this condition. Dogs do not recover from this disorder and usually at some point (which varies with the rate of progressive deterioration), euthanasia becomes the best option.

For the veterinarian:

Routine diagnostic tests are normal with this condition and a definitive diagnosis can only be made by brain biopsy or on post-mortem. However, generally with this condition, the cerebellum appears grossly normal. Histopathologic abnormalities are often minimal and do not seem to correlate with the severity of cerebellar signs.

Breeding advice:

Affected dogs, their parents (carriers of the trait), and their siblings (50% chance of being a carrier) should not be bred.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Bailey KS. Cerebellar Abiotrophy. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:186-187.
Coates JR. Weeble, Wobble, Roly, Poly: A Study of Cerebellar Disease. Proc. ACVIM Forum, 1996:684-687. This reference provides a comprehensive breed list, with associated clinical and pathologic findings.
Sargan DR. IDID - Inherited diseases in dogs:web-based information for canine inherited disease genetics. Mamm Genome. 2004 Jun;15(6):503-506.

Cerebellar hypoplasia

roblib — Thu, 29 Apr 2010 15:57:15 +0000

What is ... ?:

The cerebellum is the part of the brain that regulates the control and coordination of movement. In this condition, the cells of the cerebellum do not mature normally before birth - this causes clinical signs related to poor balance and incoordination. It is most common in kittens that have been exposed to panleukopenia virus ( also called feline distemper) in utero. It is less common in dogs, where it may be related to in utero parvovirus infection. Some cases are believed to be inherited.

How is ... inherited?:

Autosomal recessive. This disorder is rare. There are sporadic reports of this disorder in breeds other than those listed below.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

The cerebellum is the part of the brain that regulates the control and coordination of voluntary movement. The clinical signs of cerebellar dysfunction in affected puppies range from mild to severe, and may include poor balance, a wide-based stance (feet planted far apart), stiff or high-stepping gait, apparent lack of awareness of where the feet are (standing or walking with a foot knuckled over), and head or body tremors. Affected pups have normal mental alertness. In this condition, in contrast to cerebellar abiotrophy, signs of cerebellar dysfunction are evident at birth or by 2 weeks thereafter, and do not get worse as the pup ages. Other than the abnormalities in balance and coordination, the animal's general health is unaffected.

How is ... diagnosed?:

The clinical signs (relating to uncoordinated movement and lack of balance) are evident as soon as the pups are walking and are suggestive of a cerebellar disorder. Your veterinarian will do tests to rule out other conditions that can cause similar signs.

How is ... treated?:

There is no treatment for this condition. Affected dogs will not get any worse (or better) and, especially where the signs are mild, may be able to lead a relatively normal life, particularly if owners can adjust their expectations to the dog's limitations.

For the veterinarian:

Intention tremor (of both head and limbs) is common. The tremors worsen with stress or excitement and subside when the dog is at rest. Diagnosis is based on the clinical signs, lack of progression, and lack of significant findings on other diagnostic tests.

Breeding advice:

Affected dogs, their parents and their siblings should not be used for breeding.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Jones B, Shiel R. Neurologic disorders. In: Shaer M, ed. Clinical Medicine of the Dog and Cat. London, UK:Manson, 2010: 644.

Coates, J.R. 1996. Weeble, wobble, roly, poly: a study of cerebellar disease. ACVIM-Proceedings of the 14th Annual Vet. Med. Forum. pp 684-687. This reference provides a comprehensive breed list, with associated clinical and pathologic findings.

Deafness

roblib — Thu, 29 Apr 2010 16:17:09 +0000

What is ... ?:

Inherited deafness in one or both ears occurs due to the degeneration of sensory inner ear structures (sensorineural deafness) within a few weeks of birth. This occurs in many breeds and is especially common in the dalmatian.

In most breeds, the trait for deafness is tied to the genetics of coat colour, particularly in breeds with the merle or piebald gene. There is an increased risk of deafness in dogs with white, spotted, merle, or dappled hair coats.

How is ... inherited?:

In most breeds, inherited deafness is associated with white colouration of the skin and hair, which in turn is linked to the piebald and/or merle genes. In breeds with merle coat colours (eg. collie, harlequin Great Dane), there is incomplete dominance with incomplete penetrance. In some such breeds the percentage of affected (ie. deaf) dogs is very high (eg. Norwegian dunkerhound). Inheritance of deafness in breeds with a white or peibald coat colour (eg. Dalmatian, bull terrier) is less-well understood. The prevalence of deafness in Dalmatians (bilateral or unilateral) is as high as 30%. [For detailed information on genetic expression, deafness, and coat colour, see Strain 2011 below.]

The complexities of inheritance in association with coat colour make breeding decisions very difficult. Dogs with normal hearing in both ears can produce bilaterally deaf puppies, and vice versa. Dogs with deafness in 1 ear can have pups that are deaf in both ears or neither. Statistically however, deaf parents are more likely to produce deaf pups. Dogs with more white in their coats and with blue eyes are more likely to be deaf, and to produce deaf pups.

In the Doberman pinscher, inheritance is autosomal recessive with no association with coat colour.

What does ... mean to your dog & you?:

Pups lose their hearing a few to several weeks after birth. Signs of bilateral deafness may include aggressive play because the deaf pup does not hear cries of pain from littermates, and having to be jostled to waken. Unilateral deafness is much harder to spot.

If your dog is deaf in only 1 ear, you will likely not even be aware of it. In training sessions, you may notice that your dog responds better to hand signals than verbal cues.
One-sided deafness is generally not a problem, except in some working dogs for whom localization of sound is important. However it is much more difficult for bilaterally deaf dogs to lead a normal life, and breeders will generally opt for euthanasia of these pups.

How is ... diagnosed?:

If you suspect your dog is deaf, your veterinarian will recommend the BAER (Brainstem Auditory-Evoked Response) test since hearing loss can be very difficult to evaluate by clinical examination (ie. behavioural response to sounds). The BAER test is a painless and reliable means of detecting hearing loss in one or both ears, that is available at veterinary schools and referral centres. It can be used in puppies of 5 weeks of age on. Older pups and adult dogs may need to be sedated for the test.

Dogs in breeds with a high incidence of deafness should be tested by the BAER test before being used for breeding, and pups should be tested before being sold. Hearing loss, if present, is complete - that is the dog either has normal hearing, or is totally deaf in 1 or both ears.

How is ... treated?:

Deafness can not be cured or treated, but dogs can generally accommodate very well, particularly if only deaf in 1 ear. They should not be bred.

Because dogs that are deaf in both ears startle easily, are difficult to train, and are prone to accidents, they are usually euthanized as pups. As an alternative, an owner may train the dog to respond to hand signals or other visual cues, always restrain him/her on a leash or in a fenced yard, and be alert to the possibility of the dog biting someone if startled.

Breeding advice:

Controlled breeding can reduce deafness. Any dalmatian to be used for breeding should be checked by the BAER test. Pre-breeding BAER screening should also be used in other breeds where congenital deafness is a problem. Bear in mind that dogs who are deaf in 1 ear appear to function normally, but they should not be used for breeding as this contributes to the perpetuation of this disease.

Well-defined and publicized screening programmes and registries of dogs used for breeding will help to reduce the incidence of deafness. The Institute for Genetic Disease Control (GDC) maintains an open registry for deafness, for all breeds. There is a lower incidence of deafness in dalmatians in Norway and the UK, likely due to selection by breeders against blue eyes. It is laudable that dalmatian breed clubs, particularly in the UK, have supported research aimed at reducing deafness through assistance with funding and data collection.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Sargan DR. Deafness. In IDID - Inherited diseases in dogs:web-based information for canine inherited disease genetics. 2002-2011. Mamm Genome. 2004 Jun;15(6):503-6. Search this database for more detailed information on inheritance patterns and association with coat colour in particular breeds.

Strain GM. Whitenoise: Pigment-associated deafness. Vet J 2011;188:247-249, and Deafness in Dogs and Cats

Webb AA, Cullen CL. Coat color and coat color pattern-related neurologic and neuro-ophthalmic diseases. Can Vet J 2010;51(6): 653–657.

Webb AA. Deafness. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:276-77.

Becker SC. 1997. Living with a Deaf Dog: A Book of Advice, Facts and Experiences about Canine Deafness. Cincinnati. Susan Cope Becker.

Degenerative myelopathy

roblib — Thu, 29 Apr 2010 16:42:14 +0000

What is ... ?:

This disorder affects dogs 5 years of age or older. There is a slowly progressive loss of coordination in the hind limbs, with increasing weakness. This occurs because of deterioration of structures in the spinal cord that are responsible for conduction of nerve impulses (specifically the loss of myelin and degeneration of axons in the white matter). Although the changes may be found anywhere in the spinal cord, they are most severe in the lower back (thoracolumbar) region.

The cause of these changes is not known. There is evidence that an inappropriate immune response (to a neural antigen) may be involved.

How is ... inherited?:

The mode of inheritance has been identified as autosomal recessive in several breeds and a mutation has been identified that is reponsible for the development of DM (see more information below). A relatively high proportion of German shepherds, boxers, and Pembroke Welsh corgis have the predisposing mutation but it is also not uncommon in several other large and medium breeds.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

The condition is seen in dogs 5 years of age or older. The changes develop slowly and may initially be blamed on hip dysplasia. The first signs are weakness and lack of coordination in the hind limbs; these signs are more apparent when the dog is walking on a smooth surface. One side may be more severely affected than the other. The condition does not appear to be painful, and dogs retain the ability to control urination and defecation, although as they become progressively weaker they will be unable to move to an appropriate spot or assume the necessary posture.

These signs gradually worsen until the dog is unable to walk, usually several months to a year after the neurologic problems are first noticed.

How is ... diagnosed?:

There are several conditions that can cause this kind of weakness in the hind end in middle-aged medium to large breed dogs. Your veterinarian will do a thorough neurologic exam and x-rays on your dog to rule out other causes.

How is ... treated?:

Although there is no specific treatment for this condition, supportive care can generally be provided for several months.Your veterinarian will suggest ways to help you adjust to your dog's gradually increasing limitations, and to recognize the point at which euthanasia becomes the best option. This is usually within a year of the initial diagnosis, when your dog is no longer able to walk.

Some believe that treatment with a combination of increased exercise, vitamin supplementation and aminocaproic acid may slow the progression of this disease (further information in Coates below), but there have been no controlled studies that prove or disprove efficacy.

For the veterinarian:

Rule-outs include diskospondylitis, myelitis, intervertebral disc protrusion, and spinal neoplasia. Abnormalities on neurologic examination are consistent with an upper motor neuron lesion in the T3-L3 region, and include decreased proprioception and placing reactions in the hind limbs, normal to exaggerated patellar and hind limb withdrawal reflexes, normal anal sphincter tone, and sometimes crossed extensor reflexes in the pelvic limbs. Occasionally patellar reflexes are depressed or absent in one or even both legs, but this is an afferent rather than an LMN lesion.

Breeding advice:

Because clinical signs don't develop until well after sexual maturity, it has been difficult to avoid using dogs for breeding which may pass on the condition. There is now a DNA test that can identify dogs that are normal, dogs that are carriers (one copy of the mutated gene), and dogs that are very likely to develop the condition in later life (2 copies of the mutated gene). Breeders of dogs in which this condition is a concern are strongly encouraged to test their potential breeding stock for the DM mutation.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Coates JR. Degenerateive myelopahy. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:279-80.

Degenerative myelopathy testing -information on identification of a mutation responsible for the development of DM

Sargan DR. Deafness. In IDID - Inherited diseases in dogs:web-based information for canine inherited disease genetics. 2002-2011. Mamm Genome. 2004 Jun;15(6):503-6. Search this database for more detailed information on inheritance patterns, mutations, and DNA testing in a particular breed.

Globoid cell leukodystrophy (galactocerebrosidosis)

roblib — Thu, 29 Apr 2010 16:48:42 +0000

What is ... ?:

This is a storage disease, one of a relatively rare, but devastating, group of disorders in which there is a deficiency of a particular enzyme necessary for normal metabolic processes within the body. The result is an accumulation in cells ("storage") of whatever product the enzyme normally acts upon. Typically, animals with a storage disease are normal at birth, fail to grow as rapidly as littermates and, at a consistent age, develop progressive signs of a disorder of the nervous system which will ultimately be fatal.

In globoid cell leukodystrophy (GCL), the lack of the enzyme ß-galactocerebrosidase results in an accumulation of galactocerebroside, a component of myelin. This disrupts the cells that normally produce myelin, a fatty substance that coats nerve cells, serves as an electrical insulator and is crucial to the normal conduction of nerve impulses. The progressive loss of myelin in the white matter tracts of the nervous system (brain, spinal cord and/or peripheral nerves) causes a variety of clinical signs such as lack of coordination, tremors, and weakness.

This is a similar condition to Krabbe's disease in people.

How is ... inherited?:

This is a rare disorder that is seen most often in the Cairn and West Highland white terriers, in which it is inherited as an autosomal recessive trait. It is also autosomal recessive in the miniature poodle, Irish setter and Australian kelpie. The mode of inheritance is unknown in other breeds.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Puppies affected with GCL are normal at birth but grow more slowly than their littermates, and begin to to show signs of incoordination by 3 to 6 months. You may see tremors, a stiff gait, weakness, poor balance (falling to one side, stumbling), changes in behaviour or attitude, and vision changes.

The disease is rapidly progressive and is invariably fatal. Affected dogs generally die or are euthanized by about 12 months.

How is ... diagnosed?:

Your veterinarian will do a thorough neurologic exam on your dog. Diagnostic tests for other conditions that might cause your dog's signs will show no abnormalities. As the disease progresses, magnetic resonance imaging (if available) will show diffuse disease in the white matter. There is a DNA test available through HealthGene that will identiify normal, carrier (heterozygous) and affected Cairn terriers and Westies. A DNA test is also available in some other breeds. See the Orthopedic Foundation of America's currently available tests for more information.

How is ... treated?:

Unfortunately there is no treatment for this condition. Your veterinarian will help you decide when your dog's condition has deteriorated to the point where euthanasia is the best option.

For the veterinarian:

Initially there is an ascending ataxia and paraparesis, starting in the hind end, with or without cerebellar signs. There is a steady progression to paralysis +/- convulsions.

An enzyme assay is available for galactocerebrosidase activity, which will show significantly decreased enzyme activity in affected animals (homozygous) and about 50% of normal activity in carriers (heterozygous), compared with homozygous normal dogs. A biopsy of affected peripheral nerves will show segmental demyelination and perivascular "globoid cells" (large foamy macrophages containing myelin debris).

Breeding advice:

Affected animals and their parents (who are carriers of the defective gene) should not be bred. There is a DNA test available through HealthGene that will identiify normal, carrier (heterozygous) and affected Cairn terriers and Westies. A DNA test is also available in some other breeds. See the Orthopedic Foundation of America's currently available tests for more information.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Coates JR, O'Brien DP. Inherited peripheral neuropathies in dogs and cats. Vet Clin North Am Small Anim Pract 2004; 34:1361-1401.
Packer RA. Storage diseases. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:1041-1043.

Hypo-/dysmyelinogenesis ("shaking pup")

roblib — Thu, 29 Apr 2010 17:15:55 +0000

What is ... ?:

Myelin is a fatty substance that coats nerve cells. It serves as an electrical insulator and speeds the conduction of nerve impulses. The formation of myelin begins mid-way through pregnancy and continues for a short period after birth.

In this disorder, there is a lack of ("hypo"), or abnormal ("dys") myelination, primarily in the spinal cord but also in parts of the brain. Most affected is the general proprioceptive system, which is important for the coordination of body movements and positioning. In Golden retrievers, the hypomyelination is in the peripheral nervous system, leading to weakness, poor balance and muscle atrophy, but without tremors.

The condition is most severe in the springer spaniel. In other breeds, puppies often gradually improve, perhaps because of continued slow myelination of cells after birth.

How is ... inherited?:

The condition is an x-linked trait in the springer spaniel ("shaking pup"). In some other breeds it is believed to be autosomal recessive.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Because the proprioceptive system is most affected, pups with this condition have problems with balance, coordination, and positioning. They have a wide-based stance, and appear clumsy (but without weakness). Pups may have what is described as a rocking horse gait. There are pronounced tremors of the head and legs, which are stronger when the pup is excited or moves, and subside at rest or during sleep. Affected pups are normally alert and responsive to their surroundings. Because it is the peripheral nerve myelin that is reduced in Golden retrievers, there is weakness, poor balance and muscle atrophy, but without tremors.

Signs are first noticed after birth or when the pups first walks. In breeds other than the springer spaniel, the clinical signs slowly disappear so that dogs are normal by 12-18 months.

Because the trait is sex-linked in the springer spaniel, males are most severely affected. By about 2 weeks of age, affected male pups develop a severe tremor of the body, head and legs that decreases during rest and worsens with excitement. They are unable to stand, walk, or eat and generally do not survive unless intensively hand-reared. The disorder is generally fatal by 3 to 6 months of age. Females will be carriers of the trait and may show mild signs as puppies that disappear by 4 to 6 weeks of age.

How is ... diagnosed?:

There are other conditions, primarily affecting the cerebellum, that cause similar signs in newborn puppies. Your veterinarian will do tests to rule out other possible causes.

How is ... treated?:

There is no treatment, but affected puppies (other than springer spaniels) tend to improve over time, often to complete recovery by 12 - 18 months of age.

For the veterinarian:

Primarily proprioceptive fibers are affected, so clinical signs resemble cerebellar disease. In neonates this condition is easily confused with cerebellar hypoplasia. Diagnosis is based on the clinical signs, gradual improvement (except in the springer spaniel), and lack of significant findings on other diagnostic tests.

Breeding advice:

The mother of any affected springer spaniel pup is a carrier and should not be used again for breeding. Breeding of his sisters should also be avoided as they have a 1 in 2 chance of being a carrier, and passing this severe disorder to any male offspring.

In other breeds, affected animals (even if recovered to normalcy), their parents (carriers of the trait) and siblings (suspect carriers) should not be bred.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Cuddon, P.A., Duncan, I.D. 1992. The canine myelin mutants - clinical, electrophysiological, MRI, and pathological studies. ACVIM- Proceedings of the 10th Annual Vet. Med. Forum. pp 757-759.

Sargan DR. Deafness. In IDID - Inherited diseases in dogs:web-based information for canine inherited disease genetics. 2002-2011. Mamm Genome. 2004 Jun;15(6):503-6. Search this database for more detailed information on inheritance patterns and mutations in specific breeds.

Hydrocephalus

roblib — Thu, 29 Apr 2010 17:37:53 +0000

What is ... ?:

With hydrocephalus there is an abnormal build-up of cerebrospinal fluid (CSF) in cavities in the brain (the ventricles). This results in increased pressure on the brain, which causes the clinical signs seen with this condition.

Hydrocephalus can be congenital (i.e., the animal is born with the condition) or acquired, in which case the condition is acquired later in life due to some disease process that blocks normal drainage of the CSF. The congenital form, discussed here, is seen most often in brachycephalic (dogs with a shortened head) and toy breeds.

How is ... inherited?:

The mode of inheritance is unknown, but there is a predisposition to this condition in the breeds listed below.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Puppies with severe hydrocephalus often die at a very early age due to pressure from the increased fluid in the brain. In other less severely affected pups, the signs gradually become apparent over the first few months of life, and in some mild cases the condition is only diagnosed later in life.
The types of signs seen with this condition include lack of thriftiness (smaller than littermates, slow to grow), a domed skull (which gradually becomes more pronounced), abnormal movement behaviour (e.g., restlessness, aimless walking), problems with vision, and seizures. These pups are very slow to learn - it may be extremely difficult to housetrain them for example, or they may lose their housetraining.

Generally the signs gradually worsen, although by 2 years of age they may stabilize. To minimize brain damage, the condition must be recognized and appropriate treatment begun early. However, affected animals will likely always be slow and have a limited ability to learn.

How is ... diagnosed?:

Hydrocephalus can be difficult to diagnose. Your veterinarian will consider the combination of physical, behavioural and neurological abnormalities in your dog. The diagnosis can be confirmed by MRI or CT scanning, or by ultrasonography in some cases.

How is ... treated?:

There are various drugs that may be used to decrease cerebrospinal fluid production. Treatment often needs to be repeated, although some dogs will stabilize by about 2 years of age. If no improvement is seen within a few weeks of beginning medical treatment, your veterinarian may suggest surgical implantation of a shunt to drain the CSF.

Affected dogs are susceptible to other medical problems and may have a poor tolerance to various drugs. Antiepileptic drugs may be used for control of seizures.

Depending on the severity of the clinical signs, and recognizing the ongoing medical problems these dogs may face, your veterinarian will likely discuss with you humane euthanasia as another option for your pup.

For the veterinarian:

Ultrasonography can be performed through an open fontanelle to confirm ventricular enlargement. An open fontanelle is not diagnostic per se of hydrocephalus, as it may occur in a normal healthy dog.

Some hydrocephalic dogs have a bilateral divergent strabismus ("setting sun sign").

Breeding advice:

Affected animals should not be bred. Even though little is known about the heritability of this condition, it is also preferable to avoid breeding dogs who are unaffected but have a familial history of hydrocephalus.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Ackerman, L. 1999. The Genetic Condition: A Guide to Health Problems in Purebred Dogs. pp 135-136. AAHA Press. Lakewood, Colorado.

Coates JR. Hydrodephalus. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:534-535.

Idiopathic epilepsy

roblib — Fri, 30 Apr 2010 16:36:58 +0000

What is ... ?:

Seizures are the result of a disturbance in the electrical activity of brain cells. They can occur for a variety of reasons, in any breed of dog. Idiopathic epilepsy is the term used for recurrent seizures where no underlying disease process can be identified as the cause.

Inherited idiopathic epilepsy is genetically transmitted in some breeds of dogs. Seizures typically begin between 1 and 3 years of age. Before or after this age, the seizures are more likely caused by an active disease process, such as infection, trauma, a metabolic disorder, or a tumour.

How is ... inherited?:

Idiopathic epilepsy has been reported in nearly all breeds. However there is an increased risk and evidence for an inherited basis in the breeds listed below. The mode of inheritance is generally unknown, and appears to vary between breeds. In some breeds, it appears that more than 1 gene is involved.

What does ... mean to your dog & you?:

The effects of a seizure depend on the part of the brain involved. Typically there is a change in behaviour (eg. confusion, fear, rage), consciousness (the animal may or may not lose consciousness), motor activity (rigid or jerky muscle spasms, or paddling), and autonomic activity (salivation, urination, and defecation). Changes in sensory function may lead to pawing at the face, tail chasing, or biting at part of the body or the air.

Seizures may be partial or generalized, and mild or severe (grand mal). A dog experiencing a mild generalized seizure might be confused, show weakness and some muscle tremors, and look to the owner for reassurance. A dog in a grand mal seizure will be unconscious, with rigid or jerking limbs, and involuntary salivation, urination, and defecation.
Seizures vary in frequency as well, from very occasional to almost constant. Status epilepticus is a series of seizures in rapid succession, or 1 continuous seizure. This is a medical emergency which requires immediate veterinary attention.
It is common for a dog to show a change in behaviour such as hiding or attention-seeking for hours or even days before a seizure (called the prodrome or aura). Abnormal behaviour associated with fatigue, depression, hunger, thirst, or hyperactivity may last for days afterward (post-ictal phase).

How is ... diagnosed?:

You may not recognize that what has occurred in your dog is a seizure (especially if mild), and your dog will likely be back to normal by the time you see your veterinarian (except in the case of status epilepticus). Thus your description of the abnormal activity you observed is very important.

In order to determine if seizures are due to an underlying disease or are a result of idiopathic inherited epilepsy, your veterinarian will consider the age and breed of your dog and the changes you observed, do various diagnostic tests to rule out other possible causes, and ask questions such as whether your dog may have been exposed to any toxins or possibly received a head injury.

The sudden onset of frequent seizures usually indicates an active brain disease, whereas otherwise normal animals that have a few seizures a year likely have idiopathic epilepsy.

How is ... treated?:

Treatment depends on factors such as the severity and frequency of the seizures. A dog that experiences the occasional mild seizure probably needs no treatment other than watchfulness on the part of the owner. Grand mal seizures or status epilepticus, at the other extreme, require emergency medical treatment to sedate or anesthetize the dog, and to prevent the brain damage associated with prolonged seizure activity.

Once your veterinarian has determined that your dog has idiopathic epilepsy (ie. no specific cause that can be treated), s/he will likely recommend regular medication to control seizures if they occur more than once a month or in clusters, or if your dog has experienced a grand mal seizure. Phenobarbital is the drug most commonly used and it is safe, effective and inexpensive. Your veterinarian will work with you to determine the lowest effective dose for your dog. You will be asked to keep careful track of any seizures as well as all drugs given. Blood levels of phenobarbital should be measured periodically, as well as indicators of liver and kidney function. With this monitoring, most dogs with idiopathic epilepsy can lead a normal life. Dosages may need to be adjusted if there is a change in seizure frequency or severity, or if medication is given for another reason. If seizures were initially readily controlled and none has occurred for 6 to 9 months, your veterinarian may very gradually reduce the dosage, and even try discontinuing the use of anticonvulsants.

Phenobarbital is not always effective and there are other anticonvulsants that can be tried. Acupuncture is another alternative which may be effective as a first line of treatment, or when use of anticonvulsants fails to control the seizures. A veterinarian specializing in acupuncture should be consulted.

Breeding advice:

Dogs that have experienced seizures, and their parents and siblings, should not be used for breeding.

The Institute for Genetic Disease Control in Animals http://www.vetmed.ucdavis.edu/gdc/gdc.html maintains an open research database for idiopathic epilepsy in the Irish setter, Labrador retriever, and Bernese mountain dog. The Keeshond Club in Britain has operated a genetic counselling programme for keeshonds since 1989. The American Belgian Tervueren Club has also participated in a programme to gain information to reduce the incidence of epilepsy in this breed.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Institute for Genetic Disease Control in Animals: http://www.vetmed.ucdavis.edu/gdc/gdc.html
Hall, S.J.G., Wallace, M.E. 1996. Canine epilepsy: a genetic counselling programme for keeshonds. Veterinary Record. 138: 358-360.
Chrisman, C.L. 1995. Seizures. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, pp. 152-156. W.B. Saunders Co., Toronto.
Parent, J. 1996. Signalment and seizure pattern in the diagnosis and treatment of recurrent seizures. ACVIM-Proceedings of the 14th Annual Vet. med. Forum. p. 326-327.

Intervertebral disk disease

roblib — Fri, 30 Apr 2010 16:41:45 +0000

What is ... ?:

Anatomy of the vertebral column and spinal cord: The vertebral column, or backbone, is made up of a series of small bones, the vertebrae. These bones surround and protect the spinal cord, the large collection of nerves through which information is transmitted between the body and brain. The spinal cord must be intact and undamaged in order to feel sensations (including touch and pain), and for normal movement of the body and limbs. The individual vertebrae are separated by intervertebral disks. These soft tissue structures allow for normal movement between the vertebrae, and also act as shock absorbers. The structure of these disks is important in understanding this disease. Each disk is composed of an outer layer, which is fibrous, and an inner portion, which is a jelly-like mass. The outer fibrous layer (called the annulus fibrosus) acts to contain the inner jelly-like portion (the nucleus pulposus) and prevent it from bulging outwards.

Intervertebral disk disease (IVDD) occurs when the jelly-like inner layer protrudes, or herniates, into the vertebral canal and presses on the spinal cord. Compression of the spinal cord may be minimal (causing mild back or neck pain) to severe (causing paralysis, loss of sensation, and lack of bladder and bowel control) and may be irreversible.
Problems are most commonly seen in the thoracolumbar (lower back) region of the spine, and are also seen in the cervical (neck) region. IVDD is seldom a concern in the thoracic (upper back) region, because extra ligaments connect the ribs and help to reinforce the annulus fibrosus.
Type I IVDD primarily occurs in chondrodystrophoid (or chondrodysplastic) breeds such as the bassett hound, dachshund and corgi. These dogs were bred to have short, thick legs, and although this is normal for the breed, it is basically the result of abnormal development of cartilage. The intervertebral disks in these dogs gradually become more like cartilage than fibrous tissue; this increases the risk of rupture of the annulus fibrosus and herniation of the nucleus pulposus into the vertebral canal, causing IVDD. Disk herniation in these dogs occurs at a relatively young age (3 to 6 years), commonly occurs at several sites in the back, and causes intense pain.
Fibrous degeneration of disks (without calcification) occurs in older dogs of all breeds, but generally only causes problems in large-breed dogs. This is Type II IVDD; protrusion of disk material (without complete rupture of the annular layer as in Type I) usually only occurs at 1 disk and the clinical signs (pain, weakness or paralysis) generally develop more slowly and are less severe than with Type I IVDD.
With occasional exceptions, the Doberman pinsher is the only nonchondrodysplastic large breed dog to be affected by Type I IVDD, commonly in the neck region (cervical vertebral instability, or Wobbler's).

How is ... inherited?:

Unknown.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

The clinical signs vary, depending on whether there is type I or II IVDD, where in the spine the herniation occurs, and the extent of the protrusion of disk material into the spinal canal. Signs with type I generally develop more quickly (over hours or even minutes) and are more severe. Depending on the location and extent of the pressure on the spinal cord, there may be pain in the neck region, lack of pain sensation in the limbs, and weakness or paralysis in any or all limbs. This is a very serious disease, which may result in permanent hindlimb paralysis and incontinence if left untreated. While confinement may help initially in some cases, surgery is often required to relieve pressure on the spinal cord. The outcome will depend on a number of factors (including the severity of clinical signs, whether pain perception is still present, and length of time between the onset of clinical signs and surgery, to name a few). While surgery may restore the animal to normal function, it is not always successful.

With type II IVDD, clinical signs usually develop slowly over months. Again there may be pain, and weakness or paralysis in any or all limbs.

How is ... diagnosed?:

Your veterinarian will strongly suspect spinal cord compression due to intervertebral disk disease if your chondrodystrophoid-breed dog presents with neck or back pain, +/- hindlimb weakness or paralysis. Your dog may also become incontinent. Your veterinarian will examine your dog, and perform a neurologic exam to test your dog’s reflexes and the function of nerves. The absence or in some cases, heightening, of reflexes will help to determine where the pressure on the spinal cord is occurring. Plain x-rays of the vertebral column are taken of suspect areas, to locate abnormalities of the vertebrae or mineralization of the intervertebral discs. A specialized radiographic technique called myelography is necessary to pinpoint the areas of spinal cord compression, if surgical repair is being considered. In order to do a myelogram, your dog is anesthetized, dye is injected into the spinal canal, and x-rays are taken which will show the exact location(s) of spinal cord compression. A spinal tap, also performed under general anesthesia, is done to obtain a sample of cerebrospinal fluid and rule out other causes of your dog's spinal cord disease. Your veterinarian may refer you to a veterinary referral centre for these specialized radiographic techniques, and for possible surgery.

How is ... treated?:

Treatment depends on several factors, including the extent and duration of clinical signs, and the findings on neurologic and radiographic examination.Surgery is the only way to remove disc material which is compressing the spinal cord, but surgery is not necessarily the first treatment of choice. Medical treatment may be successful when there is only mild to moderate pain, and no weakness or paralysis. Medical, or conservative, treatment consists of anti-inflammatory medication in combination with strict cage rest (your dog will be confined to a cage, and let out only to urinate and defecate while on a leash). If your dog's condition worsens, or there is no sign of improvement within a week or so, surgical treatment should be considered.

Surgery will be recommended, and will be necessary, if your dog shows more severe neurologic signs, or if your dog has repeated episodes of pain and muscle weakness. Where there is paralysis and loss of deep pain sensation, surgery to remove the pressure on the spinal cord should be performed within 24 hours, or there is likely to be permanent nerve damage.
The prognosis (prospect for recovery) after surgery ranges from fair to good, depending on factors such as the severity of clinical signs before surgery, the rapidity with which the signs developed, and the length of the interval between the onset of problems and surgery. Where there has been paralysis and loss of deep pain perception for more than 24 hours, surgery is not likely to result in improvement.
Once your veterinarian has examined your dog, s/he will discuss treatment options with you. If surgery appears to be the best option, s/he will likely discuss with you referral to an appropriate surgical facility, because of the specialized radiographic and surgical techniques required. With either surgical or medical treatment, intensive nursing care will be required.

For the veterinarian:

Although signs with type I IVDD usually progress more rapidly, this is not always the case. Also, there may be periods of improvement and subsequent deterioration over weeks or months (perhaps due to extrusion of small amounts of disk material over time). Neurologic deficits depend on the location of the injury. The main clinical sign with type I cervical spine disk disease is pain; less commonly there are proprioceptive deficits and tetraparesis or tetraplegia. Signs with type I thoracolumbar disease are generally more severe, and range from abdominal or back pain, to complete paraplegia and lack of deep pain perception.

Clinical signs with type II disease generally progress more slowly; paraparesis or tetraparesis are the most common findings. As with type I disease, deficits may be asymmetric.

Breeding advice:

It is difficult to make breeding recommendations because, although the condition is common in some breeds, a mode of inheritance has not been determined. It is best to avoid breeding affected animals, and to carefully scrutinize their close relatives before including them in a breeding programme.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

LeCouteur RA, Child G. 1995. Diseases of the spinal cord. In EJ Ettinger and EC Feldman (eds) Textbook of Veterinary Internal Medicine, p. 629-696. WB Saunders Co., Toronto.
Bennett D, May C. 1995. Joint diseases of dogs and cats. In EJ Ettinger and EC Feldman (eds) Textbook of Veterinary Internal Medicine, p. 2032-2077. WB Saunders Co., Toronto.

Stigen O, Christensen K. 1996. Calcification of intervertebral discs in the dachshund: an estimation of heritability. ACTA Veterinaria Scandinavica 34(3): 357-361.

Laryngeal paralysis

roblib — Fri, 30 Apr 2010 16:55:43 +0000

What is ... ?:

In this disorder, there is some loss of function in the laryngeal muscles that normally open the larynx when an animal breathes in. This is caused by degeneration of certain nerves involved in normal breathing. The result is airway obstruction, to varying degrees, causing loud and labored respiration.

In the Dalmatian, this condition is part of a more widespread condition of the nervous system called laryngeal paralysis-polyneuropathy complex.
In the inherited form, signs are usually seen before 6 months of age. Laryngeal paralysis due to other causes is also seen in older dogs of other breeds.

How is ... inherited?:

In the Bouvier and the Siberian husky, inheritance is autosomal dominant. In the Dalmatian it is autosomal recessive.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Signs of this disorder are usually seen by 2 to 6 months of age and are often first noticed, or become worse, in hot weather. Affected dogs have difficulty breathing, and may collapse, especially with exercise. Your dog's breathing will be noisy, with coughing or gagging when eating, and you may notice that the gums are greyish rather than pink.

As part of the laryngeal paralysis-polyneuropathy complex, affected Dalmatians commonly have megaesophagus, which is a chronic dilation (expansion) of the esophagus that occurs due to loss of normal muscle tone and function, so that swallowing can not occur normally. Affected dogs regurgitate undigested food after meals, and may develop aspiration pneumonia due to inhalation of food particles or other foreign matter.

How is ... diagnosed?:

Your veterinarian will suspect a problem of airway obstruction based on what you describe and on your dog's breathing pattern. Laryngoscopy (looking down your dog's throat with a light) will confirm laryngeal paralysis as the cause.

How is ... treated?:

Initial treatment is aimed at calming your dog and lessoning repiratory distress. Depending on the severity of the obstruction, this may require mild sedation, administration of oxygen, and low doses of corticosteroids to reduce swelling. Rarely, with very severe breathing problems, a veterinarian may need to put a tube into a dog's trachea (an emergency tracheostomy).

Once your veterinarian has assessed your dog, s/he will discuss with you management of this condition. In mild cases, all that may be required is avoidance of stress, especially associated with exercise and heat, and occasional medical treatment as above for episodes of respiratory distress. Where the condition is more severe, your veterinarian may suggest surgery to tie back the muscles and enlarge the opening of the larnyx.
Unfortunately the outlook is guarded to poor for Dalmatians with laryngeal paralysis-polyneuropathy complex. Most die or are euthanized within a few months of diagnosis, due to aspiration pneumonia.

For the veterinarian:

Laryngeal function can best be assessed when the dog is very lightly anesthetized. On inspiration one or both vocal folds will not abduct normally, and the glottis will collapse. Electromyography can be used to test the function of the laryngeal muscles.

Other neurologic signs in Dalmatians with laryngeal paralysis-polyneuropathy complex may appear before, at the same time as, or after the development of signs relating to respiratory distress. Signs of neurologic dysfunction may include hyporeflexia, proprioceptive deficits, hypermetria, and paresis. Megaesophagus is common in these dogs.

Breeding advice:

Affected dogs should not be bred. In the Bouvier and husky, where inheritance is autosomal dominant, close relatives should be carefully evaluated for signs of this problem before being used for breeding.

Due to the autosomal recessive mode of inheritance in the Dalmatian and possibly the bull terrier, breeding of the parents (carriers of the disorder) and siblings (suspect carriers) should be avoided.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Braund KG. 1995. Peripheral nerve disorders. In EJ Ettinger and EC Feldman(eds.) Textbook of Veterinary Internal Medicine, p. 701-726. WB Saunders Co., Toronto.

Braund KG. 1995. Laryngeal paralysis-polyneuropathy complex in young dalmatian dogs. In JD Bonagura and RW Kirk(eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice p. 1136-1140. WB Saunders Co., Toronto.

Bjorling DE. 1995. Laryngeal paralysis. In JD Bonagura and RW Kirk(eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 901-901. WB Saunders Co., Toronto.

Leukodystrophies

roblib — Fri, 30 Apr 2010 17:01:29 +0000

What is ... ?:

In these rare conditions, there is gradual or rapid loss of myelin in the white matter tracts in the nervous system (brain and/or spinal cord). Myelin, a fatty substance that coats nerve cells, serves as an electrical insulator and is crucial to the normal conduction of nerve impulses.

Dogs affected by leukodystrophies show a loss of coordination (ataxia) reflected by difficulty in maintaining their balance, an irregular gait which may also be exaggerated (eg. high-stepping), and a progressive weakness. The conditions vary between breeds (depending on the specific changes in the white matter), and the differences are described below.

Some related terms and specific leukodystrophies are Afghan myelomalacia, Dalmatian leukodystrophy, degenerative myelopathy, fibrinoid leukodystrophy/ Alexander's disease, hereditary ataxia, hound ataxia, Labrador retriever central axonopathy, miniature poodle demyelinating myelopathy, myelomalacia, Rottweiler leukodystrophy, spongiform leukodystrophy.

How is ... inherited?:

Dalmatian leukodystrophy, Rottweiler leukodystrophy, hereditary ataxia, Labrador retriever central axonopathy, and Afghan myelomalacia are believed to be autosomal recessive.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Rottweiler leukodystrophy/ Leukoencephalomyelopathy: Affected dogs begin to lose muscle coordination (develop ataxia), somewhere between 11/2 to 4 years of age. They may also have an exaggerated gait. The condition worsens over 6 to 12 months until the dog is unable to rise.

Dalmatian leukodystrophy: Clinical signs of this disorder begin at 3 to 6 months of age, and include difficulties with vision, poor coordination, and weakness.
Miniature poodle leukodystrophy/ Demyelinating myelopathy: Signs of weakness begin at 2 to 4 months of age and rapidly worsen to paralysis.
Hereditary ataxia (progressive ataxia): This is seen in smooth-haired fox terriers and Jack Russell terriers. A gradual loss of coordination begins by 2 to 6 months of age, and progresses to the point where the dog is unable to walk. These dogs have what is called intention tremor - that is the tremor worsens with effort (to move toward something for example) and subsides when the dog is at rest.
Hound ataxia:This condition (seen in beagles, fox hounds, and harrier hounds) begins at 2 to 7 years of age with poor coordination in the hind limbs, which gradually worsens over the next 18 months or so. There is some evidence that this problem is due to environmental causes rather than of a hereditary nature.
Labrador retriever central axonopathy: Signs are evident by 4 to 6 weeks of age, and include lack of coordination, weakness and an exaggerated gait. By 5 months of age, affected pups are unable to walk.
Afghan myelomalacia (hereditary myelopathy of Afghan hounds): Signs of weakness and incoordination develop in affected dogs by 3 to 13 months of age and progress rapidly.
Spongiform leukodystrophy: Clinical signs start as early as 2 weeks of age and include tremors, lack of coordination and an exaggerated gait. This condition has been reported in Labrador retrievers, samoyeds, and silky terriers.
Fibrinoid leukodystrophy/ Alexander's disease: This very rare condition has been reported in Labrador retrievers and Bernese mountain dogs. Signs associated with loss of myelin appear by 6 to 9 months of age.

How is ... diagnosed?:

These conditions are rare. Your veterinarian will base the diagnosis on the clinical signs, a detailed neurological examination, and lack of abnormalities on other diagnostic tests. The specific changes in the nervous system can only be confirmed by examination after death (post-mortem examination).

How is ... treated?:

Unfortunately there is no treatment for these disorders. Your veterinarian will help you decide when your dog's condition has deteriorated to the point where euthanasia is the best option.

For the veterinarian:

Clinical signs reflect progressive demyelination in white matter tracts, which may be in the cerebrum, cerebellum, brainstem, cranial nerves,and/or spinal cord, depending on the specific condition in the affected breed. Generally there is ataxia and upper motor neuron para/tetraparesis which progresses to para/tetraplegia.

Breeding advice:

Except in the rottweiler, the signs of these conditions are apparent before breeding age. Of course affected dogs should not be used for breeding; breeding of parents and siblings (suspect carriers) should be avoided as well.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Ackerman, L. 1999. The Genetic Condition: A Guide to Health Problems in Purebred Dogs. pp 137-138. AAHA Press. Lakewood, Colorado.

LeCouteur, R.A., Child, G. 1995. Diseases of the spinal cord. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, p. 629-696. W.B. Saunders Co., Toronto.

Lissencephaly

roblib — Fri, 30 Apr 2010 17:05:06 +0000

What is ... ?:

In this condition there is abnormal development of the nerve cells in the brain before birth. Pups with lissencephaly develop seizures, visual deficits (blindness) and unusual behaviours.

How is ... inherited?:

unknown.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

The signs that are seen with this rare condition become evident shortly after birth. There are behavioural abnormalities (which can be severe), and the pups develop seizures and are blind.

How is ... diagnosed?:

Your veterinarian may suspect this condition based on the clinical signs and absence of abnormalities on routine diagnostic tests. The diagnosis can be confirmed by MRI (magnetic resonance imaging) or on post-mortem.

How is ... treated?:

There is no treatment.

For the veterinarian:

The gyri and sulci do not form normally, and so the brain surface is nearly smooth.

Breeding advice:

Affected animals should not be bred. Although little is known about the inheritance of this rare but devastating condition, it is best to avoid breeding parents or siblings of affected pups.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Fenner, W.R. 1995. Diseases of the brain. In S.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, pp. 578-629. W.B. Saunders Co., Toronto.

Lysosomal storage diseases

roblib — Fri, 30 Apr 2010 17:26:53 +0000

What is ... ?:

The lysosomal storage diseases include ceroid lipofuscinosis, fucosidosis, glucocerebrosidosis, glycogen storage disease type III, GM1 gangliosidosis, GM2 gangliosidosis, mucopolysaccharidosis I, sphingomyelinosis. In these disorders, there is a deficiency of a particular enzyme necessary for normal metabolic processes within the body. The result is an accumulation in cells ("storage") of whatever product the enzyme normally acts upon. Cells become swollen and incapable of normal function. Although these conditions can affect many different body systems, most often the clinical signs relate to abnormalities in the nervous system. Typically, animals with a storage disease are normal at birth, fail to grow as rapidly as littermates, and at a consistent age, develop progressive signs of a nervous disorder which will ultimately prove fatal.

These disorders are generally rare. Because of similar diseases in people however, these conditions are better studied than many other, more common, inherited disorders in dogs.

Abnormality	Breeds affected (RARE)	Special tests	Clinical features
Ceroid lipofuscinosis (Batten disease)	many breeds - Australian cattle dog, border collie, chihuahua, cocker spaniel, dalmatian, wire-haired dachshund, English setter, Tibetan terrier	none, diagnosis confirmed on post-mortem	signs usually start around 1 to 2 years of age, vary between breeds (see resources below), may include diminished eyesight, abnormal behaviour, incoordination, seizures
Fucosidosis	English springer spaniel	measure enzyme levels	signs by 6 to 12 months, include slow learning, anxiety and behaviour changes, which gradually progress over the next 18 months or so, to severe incoordination, dementia, visual problems
Glucocerebrosidosis (Gaucher's disease)	Australian silky terrier	measure enzyme levels	signs by 4 to 8 months, include incoordination, tremors, hyperactivity, stiff gait
Glycogen storage disease type III (Cori's disease)	Akita, German shepherd	measure enzyme levels	signs by 6 to 12 weeks, muscle tremors, incoordination, hypoglycemia (low blood sugar), seizures, death by 8 months
GM1 gangliosidosis	Portuguese water dog, English springer spaniel	measure enzyme levels	signs by 2 to 4 months, include vision problems, lethargy, difficulty in walking, death occurs by 8 months.
GM2 gangliosidosis (type B - Tay-Sachs disease, type O - Sandhoff's disease)	German short-haired pointer (rare)	measure enzyme levels	signs by 6 to 9 months, include visual problems, abnormal behavior, incoordination, stiff gait
Mucopolysaccharidosis I	Plott hound (rare)	measure enzyme levels	signs often develop later, in adulthood; this is a connective tissue disorder and signs include musculoskeletal abnormalities, and heart disease due to thickened valves.
Sphingomyelinosis (Niemann-Pick disease)	very rare	measure enzyme levels	signs by 2 to 5 months, include incoordination, exaggerated gait, dullness

For the veterinarian: More detailed information on the pathophysiology of these conditions, the specific molecular defects, and the clinical differences between breeds is available in the resources listed below. The first also describes diagnostic tests available and pending.

Meningitis

roblib — Fri, 30 Apr 2010 17:42:17 +0000

What is ... ?:

Meningitis means inflammation of the meninges, which are the membranes that line the brain and spinal cord. Most cases of meningitis are due to bacterial or viral infection. Some forms occur in specific breeds however, and are believed to have an inherited basis. This may be because of a genetically determined abnormality of the immune system.

Beagle pain syndrome, Bernese mountain dog aseptic meningitis, pug meningoencephalitis are types of meningitis.

Abnormality	Breeds affected	Clinical features
beagle pain syndrome	beagle	seen at 5 to 10 months of age; fever, depression, intense neck pain (dogs stand with their head and neck stiff and extended, and are reluctant to move); signs wax and wane
aseptic meningitis	Bernese mountain dog	3 to 12 months; fever, neck pain, stilted gait; signs may wax and wane
necrotizing meningo- encephalitis (pug encephalitis)	pug, Maltese terrier	signs develop between 6 months and 7 years, and include seizures (which increase in severity), change in attitude, neck pain and rigidity, circling, and/or blindness

How is ... inherited?:

unknown.

What breeds are affected by ... ?:

How is ... diagnosed?:

Your veterinarian will do blood tests and take a sample of cerebrospinal fluid ( a spinal tap) to determine the cause of your dog's illness. A spinal tap, which is done under general anesthetic, will help to determine whether there is an infectious cause (septic meningitis) - an important factor in the decision about treatment.

How is ... treated?:

Both beagle pain syndrome and Bernese mountain dog aseptic meningitis are treated with high doses of corticosteroids, which are gradually tapered to a low dose every second day. If 6 months goes by without problems on the low dose, your veterinarian may suggest that you try stopping the treatment. This works well in some dogs; others will have to be on a low dose for life.

Unfortunately there is no treatment that is effective for pug encephalitis. Seizures become progressively more difficult to control, and the abnormalities between seizures become worse. Most affected dogs are euthanized or die within a few weeks to a few months of the disorder first appearing.

For the veterinarian:

With bacterial meningitis, there is also fever, muscle rigidity and neck pain. However the signs are more severe and progress more rapidly than with aseptic meningitis. Signs such as bradycardia, DIC, shock and hypotension are much more often seen with bacterial meningitis. With both conditions, there is pleocytosis and elevated protein in the CSF.

beagle pain syndrome: CBC - nonregenerative anemia and leukocytosis with neutrophilia; CSF tap shows a neutrophilic pleocytosis with mild to moderate increase in protein
Bernese mountain dog aseptic meningitis: CBC - neutrophilia; CSF - neutrophilic pleocytosis and elevated protein
pug encephalitis: CBC - no abnormalities; CSF - leukocytosis (mostly small lymphocytes) and elevated protein. Clinically, seizures predominate, with abnormalities in gait, posture and behaviour persisting between seizures, and cortical blindness. In the more slowly progressive form, dogs may initially be neurologically normal between seizures.

Breeding advice:

Affected animals should not be used for breeding. Although little is known about the inheritance of these conditions, it is best to also avoid breeding parents or siblings of affected pups.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Ackerman, L. 1999. The Genetic Condition: A Guide to Health Problems in Purebred Dogs. pp 138-139. AAHA Press. Lakewood, Colorado.

Meric, S.M. 1992. Breed-specific meningitis in dogs. In J.D. Bonoguara and R.W. Kirk (eds) Kirk's Current Veterinary Therapy XI Small Animal Practice. pp. 1007-1009. W.B. Saunders Co., Toronto.