Cerebellar Hypoplasia

History. An 11-week-old female barn kitten is brought to your clinic for examination. The owner states that this kitten and several others in the litter have been uncoordinated since they began to walk.

Clinical Examination. Physical examination abnormal­ities are limited to the nervous system. The kitten is bright, alert, and responsive and seems to be of normal size for her age. All cranial nerve and spinal segmental reflexes and intersegmental responses are within normal limits. There is no atrophy. The kitten is uncoordinated (ataxic) when she moves and tends to raise her front paws higher than normal when walking (“goose stepping” hypermetria). She holds her paws far apart when walking. There are coarse, rhythmic movements of her head and proximal antigravity muscles that are absent at rest and severe when she is attempting a precise movement, such as getting her head to a food dish (intention tremor). Her complete blood count and serum chemistry results are within normal limits.

Comment. This kitten demonstrates classic signs of cere­bellar disease. The cerebellum constantly compares the intended movement with the actual movement and, when these are not the same, makes the appropriate adjustments. When the cerebellum cannot do this, movement disorders characterized by wide-based gaits, ataxia, dysmetria, asynergia, and inten­tion tremor occur. These movement disorders are worse with precise movement and nearly absent at rest.

This kitten’s clinical signs are likely caused by cerebellar hypoplasia, in which the cerebellum never developed com­pletely in utero. The in utero infection of feline panleukopenia virus results in destruction of the actively dividing gran­ule cells (neurons), with an underdevelopment (hypo­plasia) of the granular cell layer of the cerebellum. Purkinje cells may also be affected. Barn cats are often not vac­cinated for this disease, and often several kittens in a litter are affected.

Treatment. There is no treatment for cerebellar hypoplasia caused by such in utero viral infection. It is not a progressive disease, and if affected kittens are kept in a fairly safe environment, they can have a normal life span.