Disclosures: James Devanney, DO: No financial relationships or conflicts of interest

Case Diagnosis: Lumbar Zoster Paresis

Case Description or Program Description: A 71-year-old female awoke with radiating left lower limb pain after falling at home the night prior. In the Emergency Room, she was given a knee immobilizer. Within one week, she developed a left foot drop, requiring a walker for ambulation. Eight days later, an L5 dermatomal rash was discovered upon removal of knee immobilizer. MRI lumbar spine showed multi-level mild-moderate neuroforaminal stenoses. At the time of an electrodiagnostic study 4 months later, her pain had subsided; proximal strength had returned. Anterior leg and dorsal foot paresthesia and foot drop persisted. Exam (left) revealed diminished sensation distally, areflexia at the patella and Achilles, and distal L5 myotomal weakness.

Setting: Outpatient EMG

Assessment/Results: Electrodiagnosis demonstrated decreased motor unit recruitment through the L5 myotome, with active denervation distally and reinnervation proximally. The left superficial peroneal sensory nerve action potential (SNAP) showed low amplitude. Findings supported zoster paresis: an early chronic, active left L5 lesion with extraspinal extension to the dorsal root ganglion, with ongoing, successful reinnervation. Prognosis for functional recovery was felt to be good.

Discussion (relevance): A precedent mechanical event can mask nonstructural causes of radiculopathy, which should be considered in the setting of pain and neurological deficit that outweigh the proposed trauma or imaging abnormality. Additionally, this case raises the question of whether zoster paresis, thought to arise via contiguous spread of inflammation from the dorsal root ganglion, may give rise to electrodiagnostic pattern of radiculopathy with ganglionic or post-ganglionic involvement (abnormal relevant SNAPs). Awareness of this potential electrodiagnostic pattern could lead to improvement in diagnosis, prognostication, and treatment of non-structural radiculopathy.

Conclusions: Zoster paresis can present with myotomal weakness and EMG abnormalities, dermatomal pain and rash, and possible dermatomal SNAP abnormalities. It can mimic structural radiculopathy. Awareness of this clinical and electrophysiologic pattern can improve diagnostic and prognostic accuracy.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/lumbar-zoster-paresis-a-case-report/