Page 817 - Problem-Based Feline Medicine

36 – THE CAT WITH SEIZURES, CIRCLING AND/OR CHANGED BEHAVIOR 809

Clinical signs Recurrences may occur if the underlying cause per-
sists (e.g. hypertension). The lesion localization is how-
Peracute onset of non-progressive and rapidly
ever likely to be different from one event to another.
regressive focal cerebral signs, including seizures
alone or with other signs. Post-ischemic gliosis may result in epilepsy.
● Slight deterioration may occur over the first 24
hours as a result of edema or increased intracranial HYPOGLYCEMIA**
pressure before the condition improves. A rapidly
progressive course is expected with septic and
Classical signs
metastatic embolization.
● Mental alteration, weakness, ataxia, visual
loss.
Diagnosis
● Seizures.
Diagnosis is based on a clinical course suggestive of
a vascular event, that is, a peracute, onset of signs that PATHOGENESIS
improve rapidly.
Because blood glucose is the primary energy source for
Neurological signs and deficits are attributable to
the CNS, hypoglycemia causes diffuse CNS dysfunc-
a focal CNS lesion. Multifocal lesions are however pos-
tion. The nature and severity of the neurological signs
sible, for example, hemorrhage due to coagulation dis-
depend on the rate of blood glucose decrease, level of
orders or thrombocytopenia, or multiple metastasis.
glucose attained and duration of hypoglycemia.
Evidence of historical, clinical, laboratory and imaging
Severe and symptomatic hypoglycemia is rare in cats
findings related to the underlying cause such as poly-
except as a result of insulin over-dosage in diabetic
cythemia, hypertensive retinal changes, hyperthy-
cats. Rarely reported causes include insulin-secreting
roidism, abdominal tumor increase the index of
tumors, other tumors secreting insulin-like growth fac-
suspicion when neurological findings are consistent
tor (IGF), sepsis and terminal hepatic disease.
with a vascular accident.
Differential diagnosis Clinical signs
The classical form of the feline ischemic encephalopa- Signs may be episodic or persistent and include men-
thy is a cerebrovascular accident that occurs in young tation abnormalities (e.g. depression, confusion, stu-
adult to middle-aged healthy cats. por), weakness, ataxia, central visual impairment and
generalized seizures. Nervousness, muscle fascicula-
Acutely decompensated brain tumor as occurs fol-
tions and tremors may also occur.
lowing spontaneous hemorrhage, or tentorial herniation
● Seizures more often occur when there is a sudden
may appear clinically similar.
and marked decrease in the glucose concentration,
and are usually preceded by other more subtle signs
Treatment
of hypoglycemia such as confusion and weakness.
Treatment is specific if the cause is known and treatable.
Severe and sustained hypoglycemia may cause diffuse
Supportive and symptomatic therapy is indicated to cerebral anoxic injuries resulting in stupor-coma,
control secondary brain edema and increased intracra- decerebrate rigidity and miotic pupils. This may
nial pressure (see Feline ischemic encephalopathy, progress to irreversible damage (cortical necrosis) and
page 805 and Head trauma, page 818). permanent neurological sequela including blindness
and secondary epilepsy.
Prognosis
Diagnosis
The prognosis depends on the severity of the neuro-
logical signs and the underlying cause and whether it is Serum glucose concentration is usually < 2.2 mmol/L
treatable or not. (40 mg/dl).