Cranial nerve involvement as presenting sign of multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is characterized by slowly progressive, predominantly distal, asymmetric limb weakness and partial conduction blocks (CB) of motor axons. Cranial nerve involvement and respiratory failure are uncommon. We report two patients who exhibited unilateral hypoglossal and abducens palsy as presenting signs. Other remarkable features were autonomic instability and respiratory failure due to bilateral phrenic nerve involvement. Treatment with intravenous (IV) immunoglobulin (Ig) resulted in an improvement. Patient 2, who showed IgM reactivity against ganglioside GM1, has been receiving maintenance therapy with IVIg for 7 years. We speculate that cranial weakness of our patients could be due to CB similar to those detected in the motor nerves of the extremities.