Early identification of refractory epilepsy.

Background: More than 30 percent of patients with epilepsy have inadequate control of seizures with drug therapy, but why this happens and whether it can be predicted are unknown. We studied the response to antiepileptic drug s in patients with newly diagnosed epilepsy to identify factors associated with subsequent poor control of seizures. Methods: We prospectively studied 525 patients (age, 9 to 93 years) who wer e given a diagnosis, treated, and followed up at a single center between 19 84 and 1997. Epilepsy was classified as idiopathic (with a presumed genetic basis), symptomatic (resulting from a structural abnormality), or cryptoge nic (resulting from an unknown underlying cause). Patients were considered to be seizure-free if they had not had any seizures for at least one year. Results: Among the 525 patients, 333 (63 percent) remained seizure-free dur ing antiepileptic-drug treatment or after treatment was stopped. The preval ence of persistent seizures was higher in patients with symptomatic or cryp togenic epilepsy than in those with idiopathic epilepsy (40 percent vs. 26 percent, P=0.004) and in patients who had had more than 20 seizures before starting treatment than in those who had had fewer (51 percent vs. 29 perce nt, P<0.001). The seizure-free rate was similar in patients who were treate d with a single established drug (67 percent) and patients who were treated with a single new drug (69 percent). Among 470 previously untreated patien ts, 222 (47 percent) became seizure-free during treatment with their first antiepileptic drug and 67 (14 percent) became seizure-free during treatment with a second or third drug. In 12 patients (3 percent) epilepsy was contr olled by treatment with two drugs. Among patients who had no response to th e first drug, the percentage who subsequently became seizure-free was small er (11 percent) when treatment failure was due to lack of efficacy than whe n it was due to intolerable side effects (41 percent) or an idiosyncratic r eaction (55 percent). Conclusions: Patients who have many seizures before therapy or who have an inadequate response to initial treatment with antiepileptic drugs are likel y to have refractory epilepsy. (N Engl J Med 2000;342:314-9.) (C) 2000, Mas sachusetts Medical Society.