A Electrodiagnostic Evalustion of Motor Neuron Involvement in Patients with Herpes Zoster

Kim, Jae Wang; Kim, Kwang Joong; Lee, Chong Ju; Park, Jong Ho

Abstract

BACKGROUND: Traditionally, herpes zoster (HZ) has been known to be a recrudescence of a latent viral infection of sensory ganglia, with the spread of the virus along sensory nerves and a dermatomal cutaneous eruption. However, clinically detectable muscular wenkness often occurs in patients with HZ. Accordingly, segmental or non-segmental motor neuron involvement by HZ may occur in addition to the involvement of sensory ganglion.
OBJECTIVE
This study was conducted to estimate the frequency of motor neuron involvement in patients with HZ in Korea.
METHODS
Fifty six subjects with HZ were enrolled in this study which used a conventional needle EMG (electromyography) and motor nerve conduction velocity test. Studies were conducted a minimum of 2 weeks after the onset of the rash. EMG was performed on the ipsilateral paravertebral muscles at the dermatomial levels of the eruption and controlateral sides.
RESULTS
1. One or more abnormal EMG findings(fibrillation potential, positive waves, bursts of high frequency discharge, polyphasia, fasciculation) were found in 51.8% of HZ patients. 2. Among the subjects with motor involvement, thoracic dermatome was most frequently involved (58.6%). 3. Ipsilateral motor involvement was more common(72.5%) than controlateral involvement(27.5%) among the patients with abnormal EMG findings. 55.2% of patients showed non-segmental motor involvement and that the altered EMG findings were not confined to the segment invaded by the eruption. 4, There was no association between the presence of postherpetic neuralgia or severity of pain or initial allodynia and EMG changes.
CONCLUSION
Segmental or non-segmental motor neuron involvement by HZ may not be uncommon in Korea. HZ seems to cause widespread motor nerve changes, albeit usually subclinical alterations in the motor system, easily identifiable on EMG.