Sensory dysfunction in HTLV-I-associated myelopathy/tropical spastic paraparesis. A comprehensive neurophysiological study.

We performed a comprehensive clinical and neurophysiological evaluation of function of the large- and small-caliber afferent pathways in 29 patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Sensory symptoms, particularly cutaneous paresthesias, were present in 11 (37.9%) patients. On examination, a mild distal impairment of vibration and sense of position were found in 14 (48.2%) and 5 (17.2%) patients, respectively. Ten (34.4%) patients had distal tactile hypoesthesia and 7 (24.1%) presented pinprick hypoesthesia. Quantitative somatosensory thermotest showed cold hypoesthesia in 58.6% of patients. Nerve conduction studies and electromyography were normal. Tibial somatosensory evoked potentials were abnormal in 88.5% of patients. All of the sensory abnormalities found were restricted to sensations carried by myelinated (A-beta and A-delta) fibers. Unmyelinated C fibers mediating warm sensation and thermal pain appeared unimpaired. Our findings indicate that the sensory dysfunction in HAM/TSP patients is probably due to a lesion restricted to the central nervous system.