Page 659 - Cote clinical veterinary advisor dogs and cats 4th

302 Epilepsy, Idiopathic

and sustained contraction of all muscles encephalitis, Neospora caninum, Toxoplasma • Daily antiseizure medication is not indicated
gondii, feline infectious peritonitis
(tonic phase) followed by rhythmic muscle • Neoplasia: primary or metastatic brain tumor in patients with a single seizure, seizures
VetBooks.ir ticatory muscles (clonic phase). Autonomic • Vascular lesions: infarct, hemorrhage intoxication), or isolated seizures separated
contractions, especially of the limbs and mas-
caused by a transient condition (e.g., acute
by a long period.
• Head injury
discharge (salivation, urination, defecation)
can also occur.
syncope, episodic movement disorders (e.g.,
• Also possible are milder, generalized, tonic- • Consider nonepileptic episodes such as • Daily antiseizure medication is indicated in
patients with more than one isolated seizure
clonic seizures in which consciousness is myoclonus), narcolepsy, exercise-induced per month, clusters of multiple seizures
maintained and focal seizures in which only weakness, vestibular dysfunction, and per day or status epilepticus, or a clear
part of the body is involved (e.g., fly-biting episodes of pain. pattern of increasing frequency or severity
movements). of seizures.
• The animal is normal during the interictal Initial Database
period (between seizures, after recovery), and • CBC: unremarkable; nucleated red blood Acute General Treatment
owners do not report evidence of ongoing cells and/or basophilic stippling suggest lead • To stop an active seizure: diazepam 0.5-1 mg/
neurologic deficits. toxicosis; acanthocytes suggest hepatic disease kg or midazolam 0.1-0.5 mg/kg IV to effect
as cause of seizures • If the seizure does not stop with three doses
PHYSICAL EXAM FINDINGS • Serum chemistry profile, urinalysis: unre- of diazepam, administer
• Normal unless examined immediately after markable. Can identify metabolic causes ○ Levetiracetam 20-60 mg/kg IV over several
a seizure, when temporary postictal deficits of seizures (e.g., hypoglycemia, hepatic minutes; if effective, repeat as needed
are possible, including generalized ataxia, encephalopathy, hypocalcemia, azotemia). (typically q 8-12h) or
abnormal behavior, and blindness Fasting hypercholesterolemia may suggest ○ Propofol 1-8 mg/kg IV to effect, followed
• Persistent neurologic deficits such as hemi- hypothyroidism and attendant central by continuous infusion at 0.1 mg/kg/min
paresis, abnormal behavior, or visual deficits nervous system effects if hyperlipidemia is titrated to effect
are inconsistent with idiopathic epilepsy and severe. Hyperglobulinemia in cats raises the • If the seizure stops with the above therapy
suggest an underlying structural brain lesion possibility of feline infectious peritonitis– but recurs soon after, options, include
(p. 1136). based encephalitis as the cause of seizures ○ Load with phenobarbital 12-24 mg/kg
• A fundic exam (p. 1137) may show uveal, rather than idiopathic epilepsy. slow IV, IM, or PO single dose, followed
retinal, or optic disk diseases associated with • Serum bile acids (preprandial and postpran- by maintenance doses of 2-3 mg/kg slow
an underlying cause of seizures. These include dial) IV, IM, or PO q 12h, or
optic neuritis, feline infectious peritonitis, ○ Substantial elevation of either or both ○ Diazepam or midazolam continuous-rate
toxoplasmosis/neosporosis, systemic mycoses, suggests hepatic encephalopathy (porto- infusion: 0.5-1 mg/kg/h in 2.5% dextrose
rickettsial diseases, systemic hypertension, systemic shunt, cirrhotic/fibrosing liver plus 0.45% saline. Titrate based on seizure
lymphoma, and metastatic neoplasia. disease, other). control and sedation.
○ Moderate elevations in bile acids may
Etiology and Pathophysiology occur soon after a seizure of any cause. Chronic Treatment
Theories include inborn abnormalities in In these cases, recheck bile acids 2-4 • Options for ongoing therapy in dogs include
neuronal excitability, neurotransmitter, and weeks later to see whether the abnormality phenobarbital, zonisamide, levetiracetam,
receptor function. persists. imepitoin, and bromide. Initial therapy in
• Pursue alternative cause of seizure, as cats is phenobarbital.
DIAGNOSIS appropriate (e.g., blood lead concentration ○ Phenobarbital
if potential exposure or basophilic stippling ■ Initial dose: 2-3 mg/kg PO q 12h
Diagnostic Overview of red cells). (dog, cat) subsequently adjusted based
• Idiopathic epilepsy is a clinical diagnosis on clinical effects and therapeutic
based on the typical age of onset, lack of Advanced or Confirmatory Testing monitoring
persistent neurologic deficits, and exclusion • Brain CT or MRI (p. 1132), and cerebro- ■ Steady-state serum concentrations are
of other potential causes of seizures based spinal fluid (CSF) analysis (pp. 1080 and reached about 10-14 days after starting
on diagnostic testing. 1323) are indicated in the following patients therapy or changing the dose.
• A presumptive diagnosis of idiopathic epilepsy presenting with seizures and no identifiable ■ Common side effects: polyuria/
may be made when the patient’s signalment systemic cause: onset < 6 months or > 6 polyphagia, sedation, ataxia
and history are consistent with epilepsy and years of age, persistent neurologic deficits, ○ Zonisamide 10 mg/kg PO q 12h (dog);
the physical and neurologic exam findings an initial onset of status epilepticus/cluster or 5-10 mg/kg PO q 24h (cat)
and initial database results are normal. In such seizures, and cats. Results of these tests are ■ Side effects include ataxia, sedation,
cases, further testing should be pursued if normal with idiopathic epilepsy. and inappetance.
there is deterioration in neurologic status or • Electroencephalography (EEG) may show ■ Hepatopathy and erythema multiforme
failure to respond to medication. seizure activity but is insensitive and non- are rare idiosyncratic adverse effects.
specific with respect to cause. ○ Levetiracetam
Differential Diagnosis ■ Immediate-release formulation: 20 mg/
• Metabolic disorders: hepatic encepha- TREATMENT kg PO q 8h (dog, cat)
lopathy (including portosystemic shunt), ■ Extended-release formulation: 30 mg/
hypoglycemia, polycythemia, hypocalcemia Treatment Overview kg PO q12h (dog). Do not crush or
• Toxins: lead, ethylene glycol, organophos- • Status epilepticus and cluster seizures require divide tablet.
phate, carbamate, metaldehyde emergent treatment because they can lead ■ Minimal side effects (ataxia)
• Brain malformations: hydrocephalus, lis- to life-threatening complications such as ○ Imepitoin (not currently available in North
sencephaly hyperthermia and brain damage; prolonged America)
• Inherited degenerative diseases such as seizures become progressively refractory to ■ 10 mg/kg PO q 12h (dog) initial
lysosomal storage diseases treatment. dose. Dosages may be increased after
• Encephalitis: immune-mediated encephalitis, • Long-term treatment with antiseizure drugs is 1 week in 50%-100% increments to a
distemper, tick-borne infections, fungal started if seizures are severe and/or frequent. maximum of 30 mg/kg q 12h.

www.ExpertConsult.com