Page 1196 - Problem-Based Feline Medicine

1188 PART 15 CAT WITH EYE PROBLEMS

detachment and optic neuritis. Cats with CNS signs after cardiac arrest. The visual cortex is the most sen-
may show seizures, ataxia and/or depression. sitive area of the brain to hypoxia. Hypoxia of the
visual cortex can result in cortical blindness.
Uveitis with hypopyon and keratic precipitates is a
● Hypotension associated with acepromazine, espe-
common presenting sign.
cially intravenous administration, and high doses of
Affected cats often show other signs that may include isoflurane, or other anesthetic agents, and mask
one or all of the following: chronic nasal discharge delivery of anesthetic agents (which combines high
with swollen bridge of the nose or polyp-like mass pro- doses of inhalant agents and poor airway mainte-
truding from nostril, skin lesions, swollen lymph nodes, nance), all exacerbate anesthesia-associated hypoxia.
anorexia and weight loss. Ketamine also increases cerebral oxygen demand
and has been associated with cortical blindness.
Treatment of the ocular disease may alleviate signs,
● Cortical blindness associated with anesthesia is evi-
only to be followed by blindness with or without CNS
dent once the cat wakes up. Other neurological
signs such as seizure and ataxia.
signs may be evident such as paresis, ataxia, pro-
prioceptive deficits, circling and seizures.
Diagnosis
● Typically, there is blindness with dilated pupils,
CSF tap may confirm the presence of typical yeast-like and normal to slow pupillary light reflexes.
organisms visible either directly, or found on culture.
In feline ischemic encephalopathy typically there is a
Serology may support the diagnosis. peracute onset of unilateral forebrain signs (mental
depression and confusion, compulsive circling, hemi-
ISCHEMIC ENCEPHALOPATHY paresis and ataxia) and rarely, severe cluster seizures or
status epilepticus. Vision defects including loss of
Classical signs menace response may be present. Blindness does not
occur unless the infarction involves both hemispheres,
● Young adult to middle-aged cats.
which is uncommon.
● Sudden-onset blindness.
● Normal, slow or absent papillary light
reflexes. Diagnosis
● Seizures, ataxia and/or motor defects.
A tentative diagnosis is based on clinical signs of a
sudden onset of neurological problems in an adult
See the main reference on page 800 (The Cat With
cat unassociated with anesthesia (feline ischemic
Seizures, Circling and/or Changed Behavior).
encephalopathy), or on recovery from anesthesia.
Clinical signs CT scan or MRI using dyes may help to localize and
diagnose the problem, if feline ischemic encephalopa-
Ischemic encephalopathy can result from several dis-
thy is suspected. A CSF tap may show red blood cells,
ease processes including embolism (feline ischemic
or hemosiderin in more chronic cases.
encephalopathy), and hypotension, which is usually
associated with anesthesia.
Feline ischemic encephalopathy is a syndrome more FELINE INFECTIOUS PERITONITIS
common in young adult to middle-aged cats. The VIRUS (FIP)
pathogenesis is unknown, but is thought to be an asso-
ciated embolic event resulting in cerebral ischemia. Classical signs
● In contrast, cerebrovascular accidents resulting in
● Typically, young cats 6–12 months of age.
hemorrhage into the brain, are rare in cats, and
● Central blindness with normal PLR or
older animals are more at risk, especially if hyper-
anisocoria.
tensive from renal failure or hyperthyroidism.
● Central vestibular and cerebellar signs.
Ischemic encephalopathy may also occur as a compli-
cation of anesthesia, particularly in cats resuscitated See the main reference on page 372 (The Pyrexic Cat).