Electrophysiological findings in patients who received radiation therapy over the brachial plexus: a magnetic stimulation study.

Clinical and electrophysiological findings of 47 asymptomatic females who received radiation therapy (RT) over their brachial plexus region are presented and compared with 8 radiation-induced brachial plexopathy (RBP) and 4 neoplastic brachial plexopathy (NBP) patients. In the asymptomatic group, abnormal findings were more frequent in patients whose post-RT period was longer than 1 year. Flexor carpi radialis H reflex was delayed or absent in 19 patients (52%) in this subgroup of asymptomatic cases, as compared to only 2 (18%) of the patients with post-RT periods of less than 1 year. Magnetic cervical nerve root stimulation was performed in 16 asymptomatic cases, with the conclusion that there was no significant difference between the irradiated and non-irradiated sides with regard to latencies, amplitudes and areas of the muscle responses. In spite of this, muscle response amplitudes and areas on both sides were significantly lower than those obtained from healthy controls. It was postulated that this finding resulted from hypoexcitability to magnetic stimulation produced by slight nerve root damage. Any part of the brachial plexus could be affected in RBP and NBP patients. Myokymic discharges were found at a high rate (87.5%) in RBP group. Cervical magnetic nerve root stimulation may have a diagnostic value in these patients in localizing the nerve lesion over the brachial plexus.