ABNORMAL SENSORY NERVE-CONDUCTION IN MULTIFOCAL DEMYELINATING NEUROPATHY WITH PERSISTENT CONDUCTION BLOCK

Two patients exhibited chronic, slightly asymmetric weakness and wasti ng with fasciculations of the upper limb and hand muscles. Motor nerve conduction studies showed features of multifocal conduction block in nerve segments other than those usually involved in entrapment syndrom es. The F wave was markedly delayed in the median and ulnar nerves. Tr anscranial cortical and cervical root magnetic stimulation showed bila terally delayed thenar responses with normal central conduction time. Needle electromyography demonstrated a chronic denervation pattern wit h large polyphasic motor units in several muscles of the upper limbs. Sensory symptoms were mild and limited to paresthesias in the fingerti ps. Sensory nerve conduction velocity and sensory nerve action potenti al amplitudes were normal in elbow-to-wrist and wrist-to-finger segmen ts of the median and ulnar nerves, but there was a delayed cortical re sponse and unrecognizable Erb's point and cervical responses in the so matosensory evoked potentials to median nerve electrical stimulation. Electrophysiologic examination was normal in most nerves of the lower limbs. These two patients, meeting clinical and electrophysiologic cri teria of multifocal neuropathy with conduction block, demonstrate that sensory fibers may also be involved in this syndrome.