Electromyography and neurography in 158 cases of cephalic and limb Herpes Zoster and statistical analysis of their relations with clinical findings [Elettromiografia e neurografia in 158 casi consecutivi di Herpes Zoster cefalico e degli arti e analisi statistica delle relazioni con i dati clinici]

Objective and setting: To quantify electromyographic and neurographic changes and correlate them with the clinical data of a consecutive, non select, series of outpatients with herpes zoster (HZ). Design: Prospective study of case series. Patients: 158 cases of herpes zoster of head and limbs: 88 women, 70 men, mean age 64 years. Methods: Blink reflex (BR) and electromyography, motor and sensory nerve conduction velocities of nerves and muscles of the myotomes corresponding to affected dermatomes. Results: Postherpetic neuralgia (PHN), segmental zoster paresis (SZP) and polyneuropathy were found in 31%, 19% and 2.5% of cases. Absence of reduction of sensory action potential amplitudes, BR areas and compound muscle action potential amplitudes were found in 60%, 32% and 18% of cases. Sensory and motor conduction velocities, and motor and BR latencies were nearly always normal or only slightly slowed. Electromyographic signs of denervation were found in 36% of cases. Electrophysiological alterations were correlated among themselves, with age, with presence of SZP and with absence of antiviral therapy. The extension of the skin manifestations was the only variable predictive of disappearance or improvement of PHN. Conclusions: Sensory axonal neuropathy, often associated with similar involvement of the motor system, can be demonstrated by classical electrophysiological methods in HZ. The severity of damage to the motor fibres was found to be related to damage to sensory fibres, but no relation was found between peripheral axon damage and PHN. Motor damage may be to the ventral roots, plexus or peripheral nerve. The probability of complications and the severity of axonal damage of peripheral fibres increased with age of patients. Appropriate antiviral therapy was found to reduce risk of SZP and severity of damage to the peripheral nervous system. The reduced extension of skin manifestations was the only factor found to have a positive influence on outcome of PHN.