Neurological Conditions

By | 2011-11-25

Contents

Afghan myelopathy

A progressive disease of the white matter of the spinal cord. Symptoms include pelvic limb ataxia and paresis progressing to thoracic limb involvement, tetraplegia and eventually death from respiratory paralysis.

Ambylopia and quadriplegia

This is a lethal inherited condition of Irish Setters. Puppies are unable to walk and progression to visual impairment, nystagmus and seizures occurs.

Arachnoid cysts

Arachnoid cysts are a rare cause of focal spinal cord compression in young dogs. Neurological deficits depend on the site of the lesion.

Atlantoaxial subluxation

This is seen primarily in young dogs of Toy breeds which present with neck pain and neurological deficits in all four limbs due to cervical spinal cord compression. A variety of congenital defects including a lack of or hypoplasia of the dens and shortening of the axis lead to instability of the atlantoaxial articulation. The condition may also be acquired in any breed as a result of fracture of the dens or damage to the ligamentous support. (See also Odontoid process dysplasia under Musculoskeletal conditions.)

Birman cat distal polyneuropathy

A degenerative polyneuropathy which results in hypermetria in all limbs, progressive pelvic limb ataxia and a tendency to fall. The condition is believed to be hereditary.

Cerebellar degeneration

Cerebellar cells can undergo premature aging, degeneration and death (termed abiotrophy) leading to signs of cerebellar dysfunction (intention tremor, ataxia, hypermetria and menace deficits). In most cases the condition is believed to be hereditary.

Cerebellar malformation

Congenital malformations of the cerebellum include hypoplasia and aplasia of the whole or part of the cerebellum. Some may have a genetic basis, others result from a teratogen. Clinical signs are seen as soon as the animal becomes mobile and are non-progressive. They include hypermetria, head tremor and a wide-based stance. There is no treatment, but animals may make suitable pets if not severely affected.

Cervical vertebral malformation (wobbler syndrome)

This is a developmental malformation and malarticulation of the caudal cervical vertebrae seen in large- and giant-breed dogs, particularly the Dobermann and Great Dane. Clinical signs result from spinal cord compression and include neck pain and gait abnormalities (e.g. ataxia and paresis) which are worse in the pelvic limbs.

Congenital deafness

This has been observed in numerous breeds (especially Dalmatians and blue-eyed white cats) and usually results from a partial or complete failure of development of the organ of Corti.

Congenital vestibular disease

Young animals may present with signs of peripheral vestibular dysfunction including head tilt, circling, and falling. Nystagmus is not a common feature of the congenital condition. There is no treatment, symptoms may improve with time as the animal compensates.

Vestibular disease may also be acquired secondarily to a variety of causes including middle-ear infections in breeds predisposed to ear disease. An idiopathic form may be seen in older dogs.

Dalmatian leukodystrophy

This rarely reported progressive neurological condition results in visual deficits and progressive weakness. On gross pathology there is atrophy of the brain, lateral ventricle dilation and cavitation of the white matter of the cerebral hemispheres.

Dancing Dobermann disease

This is believed to be a neuromuscular disease of the gastrocnemius muscle, the underlying cause is not known. It has only been reported in Dobermann Pinschers and affected dogs initially flex one pelvic limb whilst standing. As progression occurs to involve the other pelvic limb the dog is seen to alternately flex and extend each pelvic limb in a dancing motion.

Degenerative myelopathy

A degenerative disease primarily seen in German Shepherd Dogs over five years of age. Diffuse degeneration of the white matter of the thora-columbar spinal cord results in progressive pelvic limb ataxia, paresis and loss of conscious proprioception. The cause in unknown.

Demyelinating myelopathy of Miniature Poodles

A rare, possibly inherited condition characterised by diffuse spinal cord demyelination. Pelvic limb paresis progresses to paraplegia and tetraplegia. Spinal reflexes are hyperactive.

Dermoid sinus

A dermoid sinus is a developmental defect arising from the incomplete separation of the skin and neural tube. It may be found midline in the cervical, cranial thoracic or sacrococcygeal regions. In cases where the sinus communicates with the dura mater, neurological signs may be seen. The condition is most commonly found in the Rhodesian Ridgeback and is believed to be hereditary in this breed.

Discospondylitis

Infection of the intervertebral disc with osteomyelitis of adjoining vertebral bodies. Infection occurs secondarily to spinal surgery, foreign body migration or septic emboli from the skin, urinary/genital tract, or from a concurrent endocarditis. Clinical signs may include pyrexia, anorexia, spinal pain and paresis.

Distal symmetrical polyneuropathy

This distal polyneuropathy has been reported in young adult Great Danes and other large breeds of dog. Symptoms include pelvic limb paresis that progresses to tetraparesis, and atrophy of limb and head muscles. There is no treatment.

Eosinophilic meningoencephalitis

This condition has been reported in six male dogs, three of which were Golden Retrievers. Cerebrospinal fluid analysis demonstrated pleo-cytosis with an eosinophil percentage of 21-98%. There was a concurrent peripheral blood eosinophilia in four of the cases. Symptoms included behavioural abnormalities and seizures.

Episodic falling

Seen in Cavalier King Charles Spaniels in the UK. During exercise, a bounding hind-limb gait develops. This progresses to a bunny-hop with arched spine, and eventually collapse often with the thoracic limbs crossed over the back of the head. There is no loss of consciousness and recovery is rapid. Some improvement may be seen with diazepam. The cause is unknown.

Giant axonal neuropathy

This is a rare inherited neuropathy of German Shepherd Dogs. The cause is unknown. Distal nerves in the pelvic limbs and long tracts of the central nervous system are affected first, giving rise to paresis, loss of spinal reflexes and pain perception in the pelvic limbs. Megaoesophagus and loss of bark occur later. There is no treatment.

Glycogenosis (glycogen storage disease)

A group of rare diseases resulting from a deficiency of one or more enzymes involved in glycogen degradation or synthesis. Glycogen accumulates in a variety of tissues including the central nervous system, muscle and liver resulting in clinical signs including seizures and muscular weakness.

Granulomatous meningoencephalitis

This is an inflammatory condition of unknown cause. The disease may be focal or diffuse and may affect any part of the central nervous system, leading to a wide range of clinical signs including seizures, ataxia, nystagmus and visual deficits. The disease is usually chronic and progressive. Small-breed dogs are most commonly affected with Poodles representing about 30% of diagnosed cases.

Hemivertebrae

Hemivertebrae are congenitally malformed vertebrae most commonly seen at the level of thoracic vertebrae 7-9. Neurological signs, e.g. pelvic limb ataxia, paresis, faecal and urinary incontinence, may result from spinal cord compression.

Hereditary ataxia

Progressive ataxia results from degeneration of the white matter of the cervical and thoracic spinal cord in young Smooth-haired Fox Terriers and Jack Russell Terriers.

Hound ataxia

A degenerative myelopathy seen in Foxhounds and Beagles in the UK. Degenerative changes are most severe in the mid-thoracic spinal cord but may extend to involve the brainstem, caudal cerebellar peduncles or sciatic nerve. Signs include pelvic limb weakness and ataxia. Muscle atrophy and loss of spinal reflexes is not seen. The cause is unknown but a link has been suggested to an all-tripe diet.

Hydrocephalus

Hydrocephalus occurs where there is dilation of all or part of the ventricular system of the brain, and may be congenital or acquired (usually secondary to neoplasia or inflammatory disease). Symptoms include a domed cranium, seizures and altered mental status.

Hyperaesthesia syndromes

Increased sensitivity to tactile and painful stimulation may result in self-mutilation which varies in severity from rippling of the skin when touched or excessive licking to auto-amputation. Some cases are due to underlying neuropathies or are forms of seizure; however, in others no underlying cause is identified. Treatments tried include phenobarbitone, megoestrol acetate and prednisolone. Success has been variable.

Hyperlipidaemia

Hyperlipidaemia (high blood lipid levels) is a familial condition of Miniature Schnauzers and cats which is believed to be associated with a reduced activity of lipoprotein lipase resulting in defective lipid metabolism. Affected animals may experience seizures as well as abdominal distress and pancreatitis.

Hyperoxaluria

A condition seen in Domestic Short Hair cats in which young cats develop acute renal failure and neurological disease. Signs include anorexia, depression, enlarged painful kidneys, weakness, reduced spinal reflexes and poor response to pain. Oxalate crystals are found deposited in the kidney tubules, and swellings of the proximal axons of the ventral horn cells are found in the spinal cord on post-mortem. There is no treatment and the condition carries a grave prognosis.

Hypertrophic neuropathy

An inherited neuropathy reported in the Tibetan Mastiff which results in generalized weakness, hyporeflexia and dysphonia from seven to ten weeks of age. There is no treatment and the prognosis is guarded.

Hypoglycaemia

Hypoglycaemia is a common metabolic cause of seizures. It may result from a variety of causes including insulinoma, hypoadrenocorticism, severe liver disease and sepsis. Young dogs of Toy breeds may develop hypoglycaemia easily when stressed, fed an inadequate diet or affected by gastrointestinal disease. Hunting dogs which are not fed on the morning of a hunt may also be predisposed to hypoglycaemia as a result of physical exertion.

Hypomyelination

Hypomyelination of the central nervous system has been seen in several breeds of dog and is known to be hereditary in some cases. Signs usually start at a few weeks of age with generalized body tremors which worsen with excitement. Hypomyelination of the peripheral nervous system has been seen in two Golden Retriever litter-mates with pelvic limb weakness and depressed spinal reflexes.

Idiopathic facial paralysis

Paralysis of the facial nerve results in drooping of the lip, paralysis of the eyelids and impaired ear movement on the affected side. Acute onset facial paralysis may occur in adult dogs without evidence of an underlying cause.

Intervertebral disc disease

Degeneration of the intervertebral discs resulting in extrusion or protrusion of the nucleus pulposus may result in spinal cord compression and pain/paresis. Nuclear extrusion occurs early in chondrodystrophoid breeds, e.g. Pekingese, Dachschunds, Beagles, Welsh Corgis, French Bulldogs, some Spaniels and Basset Hounds giving rise to signs in younger dogs.

Leukoencephalomyelopathy of Rottweilers

This is believed to be an inherited condition. Degeneration of the myelin of the spinal cord, brainstem, cerebellum and sometimes optic tracts results in ataxia, tetraparesis and loss of conscious proprioception, with increased spinal reflexes and muscle tone. Vision is usually unaffected. The condition progresses over 6-12 months.

Lissencephaly

A developmental anomaly where the cerebral cortex has reduced or absent gyri or sulci resulting in a smooth appearance. Clinical signs are usually seen from a few months of age and may include behavioural abnormalities, lack of training, aggressive behaviour, visual deficits and seizures.

Lumbosacral stenosis

Stenosis (narrowing) of the lumbosacral vertebral canal and/or intervertebral foramina causes compression of the lumbosacral nerve roots. Clinical signs may include pain on palpation of the area, pelvic limb paresis or lameness, tail paralysis, hypotonia of the anal sphincter and bladder atonicity (‘lumbosacral syndrome’). It is most commonly seen in adult German Shepherd Dogs.

Lysosomal storage diseases

These rare diseases result from a failure of normal metabolic processes due to a deficiency of an enzyme within the lysosomes of neuronal tissues. As a result, substrate accumulates, causing cellular dysfunction and eventually death. One of a variety of lysosomal enzymes may be affected. Symptoms usually occur before one year of age and may include ataxia, tremors, seizures, dementia and blindness. Most lysosomal storage diseases are believed to be inherited as an autosomal recessive trait.

Meningitis and polyarteritis

This is a vasculitis of meningeal arteries which results in clinical signs of recurrent fever, anorexia and cervical rigidity. In some cases paresis or tetraparesis may be seen. An immune-mediated aetiology has been suggested and some cases may respond to high-dose, long-term prednisolone treatment.

Meningoencephalocoele

A lethal malformation where part of the brain and meninges is herniated through a defect in the skull.

Multisystem neuronal degeneration

A slowly progressive degenerative disease of young Cocker Spaniels. Diffuse neuronal loss throughout the subcortical, brainstem and cerebellar nuclei results in symptoms including loss of recognition of the owner, apathy, hyperactivity, hypersexuality and aggression.

Muscle cramping

An inherited disorder of Scottish Terriers. Affected dogs are normal at rest but exercise may provoke muscle spasms which in its mildest form appear as pelvic limb stiffness. Severe attacks cause rigidity of all muscles including facial muscles causing the dog to fall over into a tightly curled ball. Consciousness is maintained and the animal makes a spontaneous recovery. The cause is unknown but it is believed to be a disorder of central nervous system neurotransmitters. A similar condition has been reported in Dalmatians and Norwich Terriers.

Myasthenia gravis

Decreased numbers of acetylcholine receptors on the post-synaptic muscle membrane leads to defective neuromuscular transmission. The disease can be congenital or acquired. Clinical signs in dogs include muscle weakness on exercise which improves with rest, and megaoesophagus. The onset may be chronic or acute and the condition can be generalised or focal. Signs in cats include drooling, ventroflexion of the neck, regurgitation, weakness and lameness.

Narcolepsy/cataplexy

Narcolepsy is characterised by excessive sleepiness at inappropriate times, whilst cataplexy is acute flaccid paralysis from which the animal makes a complete recovery after a few seconds to several minutes. In dogs, cataplexy seems to be the more prominent and is often associated with excitement, e.g. eating or playing.

Neuroaxonal dystrophy

A degenerative central nervous system disorder of unknown cause, seen primarily in Rottweilers. Pathological findings include swellings of the distal axons within the central nervous system and cerebellar atrophy. Symptoms include ataxia, hypermetria and intention tremors which may be slowly progressive over several years.

Partial seizures

Partial seizures result from a focal discharge from the brain. The appearance of the seizure varies with the location of the discharge but may include fly-biting, star-gazing, tail-chasing or self-mutilating behaviour.

Polyradiculoneuritis

This is an inflammatory condition affecting multiple nerve roots resulting in pelvic limb weakness which rapidly progresses to quadriplegia. An idiopathic form may be seen in any breed, however the condition has been seen following raccoon bites in hunting breeds such as the Coonhound. An immunological reaction to raccoon saliva may be the underlying cause in these cases.

Primary brain tumours

Primary brain tumours are derived from tissues of the nervous system including nerve cells, glial cells, meninges and neuroepithelial cells. They are generally solitary and most cases will present with signs of a space-occupying lesion in the brain, the specific signs varying with the location. Meningiomas and gliomas are the most common primary brain tumours in dogs. Meningiomas are the most common primary brain tumours in the cat and may be single or multiple in this species.

Progressive axonopathy

See Sensory neuropathy.

Pug encephalitis

A rare, necrotising meningoencephalitis of unknown aetiology seen in Pugs. Symptoms are often acute in onset and include seizures, depression, head-pressing, circling, blindness with normal pupillary reflexes and opisthotonus. The condition is progressive and there is no treatment. Most cases are euthanased.

Pyogranulomatous meningoencephalomyelitis

An acute, rapidly progressive disease of unknown cause seen in mature Pointers. Mononuclear and polymorphonuclear inflammatory infiltrates are found throughout the central nervous system but especially in the cervical spinal cord and lower brainstem. Dogs suffer from cervical rigidity, ataxia and sometimes seizures. The prognosis is poor. A temporary remission in response to antibiotics may be seen.

Rottweiler distal sensorimotor polyneuropathy

A polyneuropathy of Rottweilers resulting in paraparesis progressing to tetraparesis, reduced spinal reflexes, hypotonia and neurogenic atrophy of limb muscles. The condition progresses over twelve months.

Sacrocaudal dysgenesis

Congenital malformation of the sacrococcygeal spinal cord and vertebral column which results in locomotor problems in the hind legs and faecal and urinary incontinence.

Sensory neuropathy

Sensory neuropathies have been seen in a number of breeds. In Pointers signs of self-mutilation associated with loss of pain sensation predominate, whereas in Dachshunds loss of proprioception and ataxia may be seen. In Boxers the condition is termed progressive axonopathy and is characterised by pelvic limb hyporeflexia, hypotonia and proprioceptive loss.

Shaker dog disease

This condition has been most commonly observed in dogs with white hair coats, particularly Maltese and West Highland White Terriers. Dogs develop a fine whole-body tremor which may worsen with excitement and stress. Other signs may include nystagmus, menace deficits, proprioceptive deficits and seizures. There may be an underlying mild lymphocytic encephalitis and affected animals are usually responsive to immunosupressive doses of corticosteroids with benzodiazepines.

Spina bifida

This is a developmental defect resulting from the failure of the two halves of the dorsal spinous processes to fuse, most commonly in the lumbar spine. Protrusion of the spinal cord or meninges may result in symptoms including pelvic limb ataxia, paresis and urinary or faecal incontinence. If no protrusion occurs the condition is termed ‘spina bifida occulta’.

Spinal dysraphism

This is a congenital malformation of the spinal cord resulting in a wide-based stance and bunny-hopping gait of the hind-limbs. It may be associated with hemivertebrae or spina bifida. The condition is non-progressive.

Spinal muscular atrophy

This is a condition where premature degeneration of various neuronal cell populations of the brainstem and ventral horn of the spinal cord result in generalised weakness which may progress to muscular atrophy and tetraparesis/plegia.

Spongiform degeneration

Spongiform degenerations are rare disorders resulting in vacuolation of the brain and spinal cord which may result in a wide variety of neurological signs.

Springer Spaniel rage syndrome

Seen in young adult Springer Spaniels which become aggressive to people including their owners. No intracranial lesion has been found to explain this behaviour.

True epilepsy

Recurrent seizures caused by functional disorders of the brain. The high incidence in certain breeds of dog suggests an inherited basis.