Page 935 - Problem-Based Feline Medicine

43 – THE CAT WITH ATAXIA WITHOUT WEAKNESS 927

toxicosis may also result in ataxia in the early stages. Signs progress to paresis, depression,
tremors, seizures and decerebrate posture. Ivermectin toxicosis has resulted in generalized ataxia,
tremor, weakness, incoordination and miosis in a kitten. Griseofulvin therapy resulted in ataxia in
a 12-week-old kitten. Aminoglycosides, administered either systemically or topically, may cause
vestibular signs. Streptomycin and gentamicin have the most pronounced effects on the vestibular
receptors, while neomycin, kanamycin and amikacin preferentially damage auditory receptors.
Chlorhexidine solution used to clean the external ear may result in vestibular signs.

Diseases of the vestibular system include those affect-
INTRODUCTION
ing the central vestibular areas (developmental diseases,
hydrocephalus, storage disease, tumors, encephalitis
MECHANISM? and vascular-based diseases) and peripheral vestibular
areas (congenital vestibular disease, trauma, otitis
Ataxia is an abnormality of movement wherein the ani-
media/interna, idiopathic vestibular disease and
mal does not move in a straight line when walking but
tumors).
rather sways or falls, usually from side to side.
Diseases of the spinal cord include compressive, degen-
Ataxia indicates a problem with unconscious, sensory
erative, inflammatory, vascular, neoplastic, and congen-
proprioception.
ital diseases (see “The Cat With Limb Weakness”).
Lack of unconscious, sensory proprioceptive informa-
tion can also result in dysmetria, including hyperme- DISEASES CAUSING ATAXIA
tria (“goose-stepping”; overflexing of the limbs when WITHOUT WEAKNESS
walking) and hypometria (failure to flex and extend
the limb properly) resulting in a “stiff” appearance of
limb movement, and tremor. CEREBELLAR HYPOPLASIA***

Classical signs
WHERE?
● Signs are present from the early prenatal
Disease of the cerebellum, central controlling cen-
period.
ters for movement, or sensory pathways traveling ● Clinical signs usually remain unchanged or
from the spinal cord to the cerebellum are often
may improve during life.
affected. ● Coarse tremor that worsens when the cat
Disease of the vestibular system may also result in moves in a goal-oriented fashion (intention
ataxia and incoordination. tremor).
● Other signs include ataxia, hypermetria,
Diseases of the spinal cord can result in ataxia due to
menace deficits, head tilt and nystagmus.
involvement of the spinocerebellar pathways.

Pathogenesis
WHAT?
Cerebellar hypoplasia results from in utero or imme-
Diseases of the intracranial nervous system resulting in diately postnatal infection with the panleukopenia
ataxia often involve the cerebellum. virus (parvovirus).
These include cerebellar hypoplasia (panleukopenia Infection of the fetus may occur when a pregnant queen
virus infection), hydrocephalus, storage disease, is vaccinated with a modified-live panleukopenia
tumors, encephalitis and vascular-based diseases. virus vaccination.