Effect of cranial irradiation on seizure frequency in adults with low-grade astrocytoma and medically intractable epilepsy.

We report the effect of cranial irradiation on seizure frequency in five adults with unresected (biopsy-proven) cerebral hemisphere low-grade astrocytoma and medically intractable epilepsy. Seizures were refractory to standard antiepileptic drugs for 7 months to 27 years. Treatment with 5,400 cGy to 6,120 cGy focal radiation reduced seizure frequency by more than 90% in three patients (one of whom became seizure-free) and by more than 75% (but less than 90%) in one patient. One patient had no response. Brain CT or MRI showed a partial tumor response to radiation in three of the four patients with reduced seizure frequency. In three patients, the reduced seizure frequency continued to the most recent follow-up of 1 to 1.5 years. In the patient who became seizure-free, seizures recurred at 8.2 years and were associated with tumor progression. Irradiation can reduce seizure frequency in some patients with unresected cerebral hemisphere low-grade astrocytoma and medically intractable epilepsy.