[Post-radiation brachial plexus disease. Clinical and neurophysiological study].

Nine patients who developed 11 brachial plexopathies after a radiation therapy for cancer have been studied. They clinically showed heterogeneity in the common criteria used to establish the differential diagnosis between post-radiation and tumoral brachial plexopathies (PRBP and TBP) and specially within the period free of symptoms from the end of radiation, and the presence and intensity of pain. Neurophysiological studies showed a diffused neurogenic lesion with muscular denervation associated to motor and sensory nerve conduction impairment on proximal segments of the arm. Somatosensory evoked potentials were frequently abnormal with absence of N9 potential in 6 out of 7 explored plexuses. The most characteristic findings were, however, the presence of fasciculation potentials and myokymic discharges in 73 per cent of cases, and the motor nerve conduction blocking with proximal -supraclavicular and cervical spine- stimulation in all of them. Both of these phenomena, when analyzed in the same neuromuscular territory, were highly correlated, supporting a probable causal relationship. The neurophysiological data may contribute to the proper differentiation between brachial plexopathies of radiation or tumoral origin. The also would permit to consider a similar physiopathological basis of PRBP with some other infrequent neuropathies where they have been described as relevant features.