Anterior interosseous nerve and multifocal motor neuropathy.

We report the case of a 47-year-old woman with a left anterior interosseous nerve palsy. Surgical release of the anterior interosseous nerve was initially proposed, but electrodiagnostic evaluation demonstrated that the neuropathy was due not to compression or to neuralgic amyotrophy but to a proximal conduction block. At that time, the conduction block could be defined only by indirect electrodiagnostic criteria. A multifocal motor neuropathy with persistent conduction block was subsequently diagnosed, and the patient was treated with intravenous immunoglobulins. The efficacy of this treatment and the subsequent disclosure of conduction block in the right posterior interosseous and peroneal nerves definitively confirmed the multifocal motor neuropathy.