Painless foot drop: an atypical etiology of a common presentation

Weakness of the dorsiflexor muscles of the foot is a relatively common presentation. In most cases, the etiology involves a peripheral injury to the common peroneal nerve. These patients usually present with lower motor neuron findings on evaluation. In contrast, if upper motor neuron findings were present a central lesion should be suspected and appropriate imaging studies are performed. We describe a patient with painless foot drop and lower motor findings on examination that was diagnosed with multiple sclerosis. This case demonstrates that multiple sclerosis can masquerade as a peripheral process in some patients.