Herpes zoster with motor involvement: discordance between the distribution of skin rash and localization of peripheral nervous system dysfunction.

Herpes zoster viral infection (shingles) frequently appears in the thoracic dermatomes with no detectable weakness. We describe three patients who exhibited classic symptoms of herpes zoster infection of the upper limb with various neuropathic findings, including multiple mononeuropathies, radiculopathy, and brachial plexopathy. The distribution of weakness and electrodiagnostic findings was not limited to the involved dermatomes. Furthermore, the electrodiagnostic studies in one patient show evidence of acquired demyelination; hence, the infectious process may include the axon and/or the myelin sheath of the peripheral nerves. In the upper limb, we suggest that a mismatch between the distribution of the vesicular herpetic rash and weakness, as corroborated by the clinical examination and the electrodiagnostic studies, may occur.