Congenital Cerebellar Disorders in Dogs and Cats
Cerebellar Hypoplasia in Dogs and Cats
Cerebellar hypoplasia occurs in kittens after in utero infection with feline panleukopenia virus. The condition is nonprogressive, and affected cats can be suitable pets. Unlike cerebellar abiotrophy, cerebellar hypoplasia is not degenerative.
Diagnosis of cerebellar hypoplasia in cats can be obtained antemortem using MRI. Concomitant hydrocephalus or hydranencephaly can also occur. Cerebellar hypoplasia has also been reported in Chow Chows and occurs in association with lissencephaly in Irish Setters and Wire Fox Terriers.
Selective hypoplasia of the cerebellar vermis also occurs in dogs, and when combined with hydrocephalus and cystlike dilatation of the fourth ventricle, the condition has been termed Dandy-Walker syndrome, which might have a familial basis. An autosomal recessive deletion mutation in the very low density lipoprotein receptor (VLDLR) gene in Eurasier dogs has been identified.
The cerebellar vermis can be partially or completely absent in cases of cerebellar hypoplasia.
Clinical signs are typical of a cerebellar disorder and include tremors, ataxia, and hypermetria. Occasionally, signs of head tilt and circling are also present.
Toy Fox Terriers are predisposed to the Dandy-Walker form.
Caudal Occipital Malformation Syndrome in Dogs
Caudal occipital malformation syndrome (COMS, or Chiari-like malformation) and subsequent syringohydromyelia has been commonly reported in Cavalier King Charles Spaniels, American Brussels Griffons, and less commonly, other small-breed dogs. Genomewide associations have not yet identified a specific genetic mutation, but candidate genes are being evaluated.
COMS is comparable to the Chiari type I malformation described in humans and includes congenital malformation of the occipital bone, resulting in a crowded caudal fossa and cerebellar herniation at the foramen magnum (see ). The subsequent disruption of CSF flow causes fluid to accumulate within the dorsal aspect of the spinal cord (syringomyelia), central canal (hydromyelia), or both (syringohydromyelia).
Courtesy of Dr. Rebecca Packer.
Approximately 25–70% of Cavalier King Charles Spaniels with caudal occipital malformation identifiable on MRI are subclinical, increasing in prevalence with age (1).
Although the malformation is present at birth, clinical signs of COMS often do not appear until later in life. Clinical signs vary but commonly include paresthesias (eg, face rubbing, phantom scratching of the back of the head), ataxia, and weakness from the syringomyelia, hydromyelia, or syringohydromyelia.
Diagnosis of COMS is based on MRI scanning of the brain and the entire spinal cord, because syringohydromyelia can appear anywhere throughout the spinal cord and is not necessarily continuous.
Medical management of COMS is often not curative; however, it may be attempted with gabapentin (10 mg/kg, PO, every 8 hours as needed, indefinitely) (2) or pregabalin (5 mg/kg or 13–19 mg/kg, PO, every 12 hours as needed, indefinitely) (2, 3) for paresthesias; with omeprazole (0.7 mg/kg, PO, every 24 hours as needed, indefinitely) (4) to decrease CSF production; and with other analgesics to manage pain.
Surgical decompression via caudal occipital craniectomy is preferred as definitive treatment; however, recurrence rates of 25–47% have been reported after surgery (5).
Inherited Cerebellar Disorders in Dogs and Cats
Cerebellar Abiotrophies in Dogs
Unlike cerebellar hypoplasia, cerebellar abiotrophy in dogs is most often an inherited degenerative disease. Cerebellar abiotrophies have been described in a number of dog breeds.
In Samoyeds and Beagles, clinical signs are apparent at the onset of ambulation; in Australian Kelpies, rough-coated collies, Border Collies, and Kerry Blue Terriers, clinical signs occur in puppies at 4–16 weeks old; in Brittany spaniels, Old English Sheepdogs, and Gordon Setters, clinical signs appear in young or mature adults.
Autosomal recessive mutations have been identified in several breeds, including the Vizsla (SNX14 mutation) and the Finnish Hound (SEL1L mutation).
Clinical signs of cerebellar atrophies include progressive cerebellar ataxia, intention tremor, hypermetria, and possible loss of menace response due to cerebellar involvement. Postural reactions remain normal, as with any pure cerebellar disease; however, affected animals might show incoordination when placing paws.
Clinical signs of cerebellar abiotrophies can be differentiated from those of cerebellar hypoplasia by the mode of onset: hypoplasia is present since birth (apparent at the time of ambulation) and nonprogressive; animals with abiotrophies are born normal and develop clinical signs after onset of the condition. These two conditions can look similar on the basis of gross pathological lesions (see ); however, the differences in development versus degeneration are evident histopathologically.
Courtesy of Dr. Rebecca Packer.
Pearls & Pitfalls
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Neuraxonal Dystrophy in Dogs and Cats
Neuraxonal dystrophy is described in both cats and dogs; however, it occurs primarily in Rottweilers (via autosomal recessive inheritance of a mutation in the VPS11 gene in Rottweilers, and in the PLA2G6 gene in Papillons). In Rottweilers, the age of onset is between 3 and 24 months, and the disorder progresses slowly over several years.
Clinical signs of neuraxonal dystrophy include cerebellar dysfunction and dysmetria in all four limbs, but with preservation of normal conscious proprioception, which should distinguish this disorder from leukoencephalomyelopathy and from advanced motor neuron disease in the same breed. Collies in Australia and New Zealand develop similar clinical signs at 2–4 months old.
Neuraxonal dystrophy has an early onset also in Papillons and Chihuahuas, as well as in cats (autosomal recessive in domestic tricolored cats).
Axonal spheroids, often in specific regions of the brain and spinal cord, are the characteristic pathological finding of neuraxonal dystrophy.
Bandera's Neonatal Ataxia in Coton de Tulear Dogs
Bandera's neonatal ataxia (Bandera's syndrome) is an autosomal recessive cerebellar ataxia identified in the Coton de Tulear dog breed. It manifests as cerebellar ataxia from the time of birth.
The disorder is nonprogressive; however, affected animals are never able to walk. The cerebellum is anatomically normal, and clinical signs result from a mutation that affects neurotransmitter function.
A DNA test is available for this disease in the Coton de Tulear.
Congenital Hypomyelination in Dogs and Cats
Congenital hypomyelination is a familial or inherited disorder that occurs in Springer Spaniels, Chow Chows, Weimaraners (for which a mutation in the FNIP2 gene has been identified), and Bernese Mountain Dogs.
Usually, clinical signs (generalized tremor) develop at approximately 2–8 weeks of age. The disorder is rare in cats.
In Chow Chows, Weimaraners, and Bernese Mountain Dogs, this disorder is often termed "dysmyelination" because the clinical signs of whole body tremor usually resolve spontaneously with time.
Diagnosis of congenital hypomyelination can be confirmed using MRI.
Also see Myelin Disorders.
Key Points
In some cerebellar disorders (eg, cerebellar hypoplasia), clinical signs are present at birth; other disorders develop within weeks (eg, congenital hypomyelination) to even as much as years later (eg, Chiari-like malformation).
MRI has enabled more accurate and specific antemortem diagnosis of congenital and inherited malformations in small animal medicine.
Rottweilers are prone to several inherited neurological disorders, including neuraxonal dystrophy that affects the cerebellum.
For More Information
MacKillop E. Magnetic resonance imaging of intracranial malformations in dogs and cats. Vet Radiol Ultrasound. 2011;52(s1):S42-S51.
Loughin CA. Chiari-like malformation. Vet Clin North Am Small Anim Pract. 2016;46(2):231-242.
Dewey CW, Da Costa RC, eds. Practical Guide to Canine and Feline Neurology. 3rd ed. Wiley Blackwell; 2016.
Also see pet owner content regarding brain, spinal cord, and nerve disorders of dogs and cats.
References
Parker JE, Knowler SP, Rudsbridge C, Noorman E, Jeffery ND. Prevalence of asymptomatic syringomyelia in Cavalier King Charles spaniels. Vet Rec. 2011;168(25):667. doi:10.1136/vr.d1726
Moore SA. Managing neuropathic pain in dogs. Front Vet Sci. 2016;3:12. doi:10.3389/fvets.2016.00012
Thoefner MS, Skovgaard LT, McEvoy FJ, Berendt M, Bjerrum OJ. Pregabalin alleviates clinical signs of syringomyelia-related central neuropathic pain in Cavalier King Charles Spaniel dogs: a randomized controlled trial. Vet Anaesth Analg. 2020;47(2):238-248. doi:10.1016/j.vaa.2019.09.007
Thomas WB. Hydrocephalus in dogs and cats. Vet Clin North Am Small Animal Pract. 2010;40(1):143-159. doi:10.1016/j.cvsm.2009.09.008
Dewey CW, da Costa RC. Practical Guide to Canine and Feline Neurology. 3rd ed. Wiley Blackwell; 2016.
