Two Cases of Delayed Post-radiation Lower Cranial Nerve Palsies

ABSTRACT

Radiation-induced lower cranial neuropathy shows a clinical presentation similar to tumor recurrence or amyotrophic lateral sclerosis. We experienced two patients with bulbar palsies several years after radiotherapy for nasopharyngeal cancer. Brain magnetic resonance imaging showed no evidence of tumor recurrence. Electrophysiologic studies demonstrated mild denervation changes and myokymic discharges in muscles innervated by cranial nerves. Bulbar palsies progressed for 1 year then became stable. We emphasize the importance of myokymic discharges in the differential diagnosis of radiation-induced cranial neuropathy as radiation plexopathies.