Page 806 - Problem-Based Feline Medicine

798 PART 10 CAT WITH SIGNS OF NEUROLOGICAL DISEASE

continued

● Feline immunodeficiency virus encephalopathy (p 819)
Usually asymptomatic, but may cause subtle and non-specific behavioral changes such as depres-
sion, social withdrawal and roaming.

PROTOZOAL
● Toxoplasmosis** (p 815)
Focal or multifocal CNS signs are rare signs accompanying the more common systemic signs such
as fever, or dyspnea or ocular manifestations (anterior uveitis, chorioretinitis) of the disease.
FUNGAL
● Cryptococcosis** (p 812)
Cerebral signs such as depression, circling and ataxia are often accompanied by chronic nasal dis-
charge, cutaneous nodules or ulcers, or ocular signs including chorioretinitis, retinal detachment
and panophthalmitis.
IDIOPATHIC
● Idiopathic epilepsy* (p 816)
Rare in cats and occurs as recurrent generalized motor seizures starting with single seizures at sev-
eral week intervals in a young adult animal that has no other neurological signs or deficits.

TRAUMA
● Head trauma (p 806)
Peracute onset of cerebral signs such as confusion to dementia, pacing, circling or hemiparesis.
Immediate onset of seizures and/or post-traumatic epilepsy may occur.
TOXIC
● Intoxications** (p 812)
Typically present with signs of depression or stimulation of the CNS (depression, agitation),
together with autonomic system signs (miosis, hypersalivation) and neuromuscular signs (weak-
ness, muscle tremors). Occasionally, convulsive status epilepticus.

● In idiopathic epilepsy, no causes other than a genetic
INTRODUCTION
predisposition underlie the intrinsic neuronal distur-
bances.
MECHANISM? ● Extracranial causes of seizures (metabolic and
toxic) diffusely affect the brain.
Seizures are generated by paroxysmal excessive dis-
The clinical appearance of seizures varies a great deal,
charge of thalamocortical neurons which are rendered
depending on the origin and extent of spreading of the
focally or diffusely hyperexcitable by several mechanisms:
seizure discharge within the brain.
● Structural brain lesions, either active (e.g.
encephalitis, tumor) or inactive (e.g. glial scar), irritate Primary generalized seizures have a diffuse onset
the surrounding neurons and transform them into within both cerebral hemispheres.
transient or permanent epileptic foci; some areas of ● They manifest with a complete loss of consciousness
the brain are more likely to generate seizures (e.g. and generalized, symmetrical and usually violent
frontal and temporal lobes) than others (e.g. occip- tonic and/or clonic motor activity that results in com-
ital lobe). plete recumbency often with thrashing and limb pad-