Most of the 0.5% to 2% of the population with
epilepsy will achieve seizure control with antiepileptic drugs.
However, approximately 16% of children with new-onset epilepsy
may become medically refractory or may have an epilepsy syndrome
for which medical treatment is known to be ineffective.1 These
children should be evaluated at a comprehensive pediatric epilepsy
surgery program to evaluate their candidacy for epilepsy surgery,
because just over half of them may be surgical candidates. The evaluation to
determine candidacy requires accurate classification of a child’s
seizures and epilepsy, knowledge of the natural history of the child’s
condition, detailed information about past epilepsy treatments,
and data acquisition to localize seizures, including video-electroencephalography (EEG)
monitoring, functional nuclear studies, and neuroimaging data. Because
many types of infantile and early childhood seizures are difficult to
classify and of uncertain prognosis, pediatric surgical experience
is greatest in older children and adolescents who have focal cerebral
lesions or mesial temporal sclerosis. Select infants and younger
children, however, may benefit from surgery, particularly when persistent
seizures may affect developmental progress, as in the catastrophic
There is no standardized definition of medical intractability.
In practice, it is often defined as the failure of an adequate trial
of at least 2 appropriate anticonvulsant medications, increased
to the limits of tolerability or expected efficacy. The appropriate
timing of when to consider surgical options is somewhat subjective.
In general, referral should be considered for medically intractable
epilepsy which is functionally disabling and impairs quality of
life. Children who may be optimal candidates include those with
focal epilepsy, limited involvement of eloquent cortical areas,
and a focal lesion.
Medically intractable epilepsy is associated with significant
morbidity and mortality, including decreased quality of life for
children and caregivers, frequent hospitalizations, anticonvulsant
adverse effects, and the low but significant risk of mortality from
seizures. Though the mechanisms are not fully understood, epilepsy
is associated with significant behavioral, psychiatric, and cognitive
comorbidity independent from the seizures.
In these children, therapeutic options are limited to further
anticonvulsant trials, the ketogenic diet, vagus nerve stimulation,
and epilepsy surgery. Emerging investigational techniques that may benefit
future patients include transcranial magnetic stimulation, neurosurgical
radiotherapy techniques, deep brain stimulation, and responsive
neurostimulation. Of these options, resective epilepsy surgery currently
offers the best chance of seizure freedom for optimal candidates.
Children differ from adults in terms of etiology of refractory
seizures. In adults, mesial temporal lobe epilepsy, frequently associated
with hippocampal sclerosis, accounts for most cases. In contrast, children
more often have extratemporal or multifocal seizure onset. Pediatric
etiologies of intractable epilepsy are diverse and include cortical
dysplasia, tuberous sclerosis, hypothalamic hamartoma syndrome,
Sturge-Weber syndrome, Rasmussen syndrome, infections, trauma, and developmental
The goal of the initial presurgical evaluation, also termed the
Phase I evaluation, is to characterize seizures and localize their
onset. No individual study is sufficient for determining epilepsy
surgery candidacy or for surgical planning. Rather, the data obtained ...