A LONGITUDINAL-STUDY OF MULTIMODAL EVOKED-POTENTIALS IN PATIENTS FOLLOWING RADIOTHERAPY FOR NASOPHARYNGEAL CARCINOMA

Radiation rhombencephalopathy and radiation myelopathy may occur in pa tients months or years after radiotherapy for malignancy of the head a nd neck. We obtained multimodal evoked potentials longitudinally in 26 patients with proven nasopharyngeal carcinoma. Recordings were made b efore radiotherapy and at 1 week, 3 months, 9 months, 15 months, and 2 4 months after radiotherapy. All absolute latencies of evoked response before and after radiation were within normal limits. However, the I- III interpeak latencies of brainstem auditory evoked potentials and th e onset latencies of motor evoked potentials in the whole group of pat ients at 15 months after radiation were significantly longer than thos e before radiotherapy, whereas the latencies at 24 months were not sig nificantly different. The N20 latencies of somatosensory evoked potent ials after radiotherapy were significantly prolonged at 3 months of fo llow-up; the prolongation then became normal. They indicate that a sub clinical reversible radiation-induced dysfunction may occur in the aud itory, sensory, and motor systems.