Page 865 - Problem-Based Feline Medicine

39 – THE CAT WITH TREMOR OR TWITCHING 857

canals may be clues to the traumatic etiology, however, cells physiologically or mechanically, resulting in cel-
some animals that are uncoordinated may fall and lular dysfunction, and hence, clinical signs. Examples
injure themselves secondarily. include gangliosidosis, sphingomyelinosis, globoid
cell leukodystrophy and mannosidosis.
Diagnosis
The diagnosis of trauma is usually straightforward
Clinical signs
when the trauma is witnessed.
Clinical signs usually begin between 3–12 months of
In some instances, animals are presented with an acute
age.
onset of neurological signs and an unknown history,
examining for external signs of trauma such as lacera- Cerebellar disease usually results in a coarse tremor
tions or skull fractures is important. that worsens (increases in frequency or amplitude)
when the animal moves in a goal-oriented fashion
Evaluating the retinas and external ear canals for acute
(intention tremor).
hemorrhage may also provide clues to the diagnosis.
Other signs of cerebellar disease that accompany cere-
Advanced imaging studies such as CT or MR imaging
bellar tremor include ataxia (incoordination; swaying
are useful, primarily for determining structural damage
from side to side), dysmetria (“goose-stepping”; over-
to the brain.
flexing of the limbs when walking), menace deficits
(with normal vision and pupillary light reflexes), head
DEGENERATIVE CEREBELLAR DISEASES tilt, and nystagmus (combination quickly followed by
slow movement of the eyes).
Classical signs
Clinical signs of the hereditary cerebellar degeneration
● Signs usually begin or are present in cats described in Japan in cats begin around 7–8 weeks of
less than 1 year of age. age and include head tremor along with ataxia, dysme-
● Signs usually are slowly progressive or tria, and intention tremor.
remain unchanged.
Cerebellar degeneration with neuroaxonal dystrophy
● Signs include coarse tremor, hypermetria,
in domestic tricolored cats results in head tremors
ataxia, intention tremor and menace
and shaking. Clinical signs begin at 5–6 weeks of age
deficits.
and progress to ataxia and hypermetria. Affected kit-
tens have a lilac color that darkens with age.
See main reference on pages 934 and 935 for details
(The Cat With Ataxia Without Weakness). In cats with sphingomyelinosis (Niemann–Pick type C
disease) clinical signs begin early in life (< 6 months)
and progress to ataxia and hypermetria, absent men-
Pathogenesis
ace responses, and occasionally positional nystagmus.
Cerebellar degeneration is usually an inherited disease. Death usually occurs by 8–10 months of age.
A hereditary cerebellar degeneration has been Niemann-Pick type A disease occurs in Siamese and
described in Japan in cats. An autosomal recessive Balinese cats. Head tremor, head bobbing and dysme-
mode of inheritance was presumed. tria begin at 3–4 months of age. Clinical signs progress
to ataxia and paresis, worse in the pelvic limbs.
Cerebellar degeneration with neuroaxonal dystro-
phy has been reported in domestic tricolored cats. This
is inherited as an autosomal-recessive trait.
Diagnosis
Storage diseases result from inherited (or less com-
Antemortem testing for these diseases often results in
monly, acquired) intracellular metabolic derangements
negative or normal findings.
that result in abnormal metabolism of cellular products.
Cellular products accumulate and afferent neuronal Routine laboratory investigations are normal.