The patient was a 55-year-old man. He was well until eleven months earlier, when he noticed the onset of numbness in his right fingers. Over the next three months, the numbness spread up the right arm and involved the right leg, left arm and left leg in succession. Six months before admission, sensory impairment of the trunk appeared progressively. Mild diffuse muscle weakness occurred gradually. Swelling of the right lateral cervical lymph node was found just before admission. On neurological examination, sensory disturbance involving all modalities of sensation was recognized in the extremities and trunk. The sensory findings were asymmetric and predominant at the lower extremities and distal parts. A positive Romberg's sign and poor coordination was recognized. All the deep tendon reflexes were absent without pathological reflexes. Motor weakness, which was less severe than sensory findings, was present. There was no sphincter disturbance nor orthostatic hypotension. Routine laboratory findings were within normal limits. The protein level of cerebrospinal fluid was slightly increased. The electrophysiological studies and histological evaluation of the biopsied peroneal muscle and sural nerve showed degeneration and reduction of large myelinated fibers of sensory nerves with minimal motor nerve changes. Histological study also revealed the increase of regenerating fibers. Squamous cell carcinoma of epipharynx with metastasis of neck lymph nodes was found. Radiotherapy without chemotherapy resulted in a complete tumor remission and probably suppressed the progression of neurological disturbances. After two years from the onset, diffuse high intensity area was noted in the posterior spinal column on T2 weighted MRI.(ABSTRACT TRUNCATED AT 250 WORDS)