Multifocal Motor Neuropathy With Cranial Nerve Involvement and Vocal Cord Paralysis: A Case Report

Multifocal motor neuropathy (MMN) is a progressive, multifocal weakness, which typically begins and predominates in the upper extremities with the absence of a sensory deficit and a hallmark electrophysiologic finding of conduction block. We describe a case of an adult male with MMN who developed both cranial nerve involvement and vocal cord paralysis. The patient presented with left shoulder weakness without sensory loss followed by hoarseness of voice and later developed tongue deviation and wasting of the left sternocleidomastoid and left trapezius muscle. Laryngeal electromyography (EMG) showed findings evident for a focal mononeuropathy involving the left recurrent laryngeal nerve. EMG and nerve conduction studies (EMG NCV) of the upper extremities showed evidence for a multifocal mainly motor neuropathy involving the left spinal accessory and hypoglossal nerves, combined with the presence of median and ulnar proximal conduction blocks bilaterally. Given the clinical presentation and electrophysiologic findings of conduction block, the patient was managed as a case of MMN and received the standard treatment with Intravenous Immunoglobulin (IVIg). Upon follow-up, there was an improvement in symptoms and no recurrence of motor weakness and hoarseness of voice. There are a few case reports about MMN but none with multiple lower cranial nerve involvement.