(Kiosk 2) Foot Drop Secondary to Herpes Zoster L5 Radiculitis: A Case Report

Case Diagnosis: 60-year-old male with sarcoidosis and recent incidence of herpes zoster presenting with left foot weakness.

Case Description or Program Description: The patient initially presented to the PCP with a painful erythematous vesicular rash in the L5 dermatomal distribution of the left leg and was prescribed valacyclovir and gabapentin for suspected herpes zoster. 2 weeks later, the patient reported continued pain and paresthesias along the distribution of the previous rash as well as new pain in the left buttock. At 6 weeks, the patient presented to a PM&R sports medicine clinic with worsening paresthesias and new onset weakness in the left foot. Physical exam revealed decreased sensation of the left great toe and lateral left foot with significantly decreased strength on left ankle dorsiflexion. Evaluation was concerning for common peroneal neuropathy versus L5 radiculopathy.

Setting: Outpatient Musculoskeletal/Sports Medicine Clinic

Assessment/Results: Diagnostic ultrasound of the left lower extremity was negative of masses compressing the common peroneal nerve at the fibular head. MRI of the lumbar spine was also negative for nerve root impingement or spinal stenosis. EMG was, however, notable for severe L5 radiculitis with the likely etiology being herpes zoster. On subsequent follow-up at 10 weeks, the patient reported improved sensation to light touch but continued left dorsiflexor weakness and left buttock pain.

Discussion (relevance): Segmental zoster paresis is a rare complication of herpes zoster that is associated with elderly and immunocompromised patients. It is characterized by motor weakness along the myotome congruent with the dermatomal distribution of the herpetic rash. Zoster paresis typically affects the face and upper extremities, seldomly affecting the lower extremities. Involvement of the L5 nerve root may present as paresthesias of the corresponding dermatome and weakness with ankle dorsiflexion.

Conclusions: Physicians should consider zoster paresis in their differential of spinal radiculopathy-like symptoms in patients with recent herpes zoster in the setting of negative imaging results.