Optimizing therapy of seizures in patients with brain tumors.

The mechanism of epilepsy in brain tumor patients is probably multifactorial, and its incidence depends on tumor type and location. Refractory epilepsy is common in patients with structural brain lesions, and a role for multidrug-resistance proteins has been suggested. The medical treatment of epilepsy in brain tumor patients has mainly been studied retrospectively, and the optimal management of seizures with antiepileptic drugs (AEDs) is unclear. Enzyme-inducing anticonvulsants are generally not recommended because they can lead to insufficient serum levels of concomitantly administered chemotherapeutic drugs. Although valproic acid is an enzyme inhibitor and may therefore lead to toxic levels of simultaneously administered chemotherapeutic agents, this does not appear to be a major problem in patients with brain tumors. Preliminary observations of add-on treatment with the AEDs levetiracetam or gabapentin suggest that these non-enzyme-inducing AEDs can be useful for control of seizures in patients with brain tumors. Conversely, prophylactic use of AEDs in brain tumor patients is generally not recommended.