Seizures must be refractory to medical therapy. Patients should have monotherapy trials with major drugs (i.e., carbamazepine, phenytoin, phenobarbital or mysoline, and valproic acid). If these are ineffective or cause intolerable side effects, combination therapy should be tried. Blood testing should be done to ensure an adequate amount of the drug is getting into the body. The drug should be escalated until seizures are controlled or unacceptable side effects are encountered. An adequate period of medical therapy is impossible to define precisely. It depends on seizure frequency (more seizures allow the physician to assess efficacy in a shorter period), severity and whether there are side effects. In most cases where medical therapy is considered to have failed, seizures have been refractory for at least two years.
Seizures must have a significant adverse effect on the child's life. There is no absolute number of seizures or clinical features that defines intractability. Impairment of consciousness during the waking state is often the critical factor. However, frequent nocturnal convulsions that leave the child lethargic and cognitively impaired the next day are also not acceptable, and would mandate a more aggressive treatment plan. Frequent simple partial seizures that do not cause unconsciousness but disrupt memory function or cause prominent hallucinations and adverse symptoms should be considered for surgical treatment. On the other hand, daytime complex partial seizures in a retarded, institutionalized child may not have a significant adverse effect on the patient's life.
There are no absolute age limits for this surgery.
Patients with chronic psychosis and mental retardation are usually not considered.
Chronic psychosis is not significantly improved by epilepsy surgery. Although the seizures may cease, the patient will remain incapacitated by mental disabilities. Mental retardation (full-scale IQ of less than 70) indicates diffuse cerebral dysfunction; these children may (1) suffer additional cognitive impairment from surgery, (2) have difficulty cooperating with the extensive pre-surgical evaluation, and (3) have persistent seizures after the procedure. Surgery for mentally retarded children should be considered only for those who suffer frequent, severe falls in association with seizures.
The seizure disorder must be partial.
Careful history from the patient and from witnesses, in combination with neurologic examination and routine electroencephalography (EEG), will almost always distinguish between partial and primary generalized seizures. In a few cases uncertainty may remain; here video-EEG monitoring is usually diagnostic. Patients with unilateral temporal lobe seizure foci have the best surgical outcome, while those with extratemporal foci do less well.
In summary, children with partial seizures that cannot be controlled medically and that disrupt their lives should be considered for surgical treatment.
Patients must undergo an extensive pre-surgical evaluation to localize definitely the focus from which the seizures arise. In addition, localization of cerebral function must be performed to identify areas that are critical to cognitive, motor and sensory functions.