Anticonvulsants and peripheral nerve function - Results of prospective monitoring in patients with newly diagnosed epilepsy

Background: Retrospective studies report that long-term use of anticonvulsa nts correlates with peripheral nerve dysfunction. However, these results ar e biased by different drug combinations, the use of toxic dosages, and the presence of other causes of polyneuropathy. Objective: To assess the risk of peripheral nerve impairment in patients kn own to be free from polyneuropathy who received anticonvulsants as monother apy at standard daily dosages. Design and Setting: This was a prospective observational study of outpatien ts seen at two hospital centres in Italy. Patients and Participants: 39 men and 42 women aged 13 to 67 years (mean 30 .5 years) with previously untreated epilepsy. Methods: Patients were given monotherapy with valproic acid (sodium valproa te) [n = 44] or carbamazepine (n = 37) at standard daily dosages to achieve normal plasma concentrations. Each patient was screened for existing polyn europathy or risk factors for polyneuropathy before inclusion; they were th en assessed for clinical and electrophysiological findings of polyneuropath y at entry and at 6, 12 and 24 months. Results: After 24 months of treatment only one patient had clinical signs o f polyneuropathy, and six patients had symptoms of polyneuropathy. The elec trophysiological values did not show significant changes or trends. Only on e patient had abnormal electrophysiological findings, which were only subcl inical, in all the follow-up examinations, and eight patients had abnormal values at two subsequent visits. No consistent patterns were found, and dat a were unaffected when the drugs were examined separately or when patients were grouped according to whether or not they had symptoms of polyneuropath y. Conclusions: Previously untreated young to middle-aged patients receiving m onotherapy with standard daily dosages of valproic acid or carbamazepine ar e not at risk of developing polyneuropathy within 24 months.