The cerebellum is the portion of the brain responsible for the control
of motion. When a puppy or kitten is born with an underdeveloped cerebellum,
the condition is known as congenital cerebellar hypoplasia. There are infectious
causes of this condition in both cats (panleukopenia infection prior to
birth) and dogs (herpes virus infection prior to birth). Improper development
of the cerebellum may occur due to injury, poisoning or just from an accident
in development in the uterus. It is generally possible to see signs of
this condition almost as soon as the puppy or kitten is born. Affected
animals have tremors and unusual jerky movements or may fall down when
they try to move. The symptoms do not get worse as they age. As the kitten
or puppy grows it will learn to compensate for its condition but there
are usually lifelong signs of a decreased ability to coordinate movement.
Almost all dogs and cats with congenital cerebellar hypoplasia can live
happily as pets with a little special care to compensate for their disabilities.
This condition can be confused with cerebellar abiotrophy, a different
disorder in dogs in which the puppy has a normal cerebellum at birth but
it gradually dies. Signs of disease identical to cerebellar hypoplasia
occur but the timing is different. Puppies with this condition seem normal
at birth but usually start to show signs of problems after they are 2 months
or more of age.