Segmental Zoster Paresis of the Unilateral Lower Extremity With Neuritis MRI Findings: A Case Report and Literature Review

Herpes zoster (HZ) is a common clinical condition caused by the reactivation of the latent varicella-zoster virus (VZV). Neurological complications after HZ have been described, including a rare condition of segmental zoster paresis (SZP), which results in unilateral motor impairment in the extremities. Only two cases of HZ patients with radiculopathy and MRI findings of neuritis have been reported. We present a 62-year-old male with a HZ rash in the right calf and low back pain radiating to the right leg accompanied by a right leg great toe weakness for one week. Neurological examination revealed 4/5 dorsiflexion of the right great toe. Also, the patient's rash was distributed on the L5 dermatome. The lumbar MRI showed a contrast enhancement of the right L5 nerve root with enlargement diagnosed as neuritis. The patient was treated with valacyclovir. The neuromotor deficit and the cutaneous rash started to improve on the third day of treatment. This case emphasizes the necessity of considering SZP in the differential diagnosis of elderly patients presenting with muscle weakness in the lower extremity with or without a rash. MRI evaluations of HZ patients with radiculopathy may include contrast-enhanced sequences.