Clinical and physiological significance of abnormally prolonged central motor conduction time in HAM/TSP

We measured the central motor conduction time (CMCT), central sensory condu ction time (CSCT), F wave and mean F wave/M wave amplitude ratio in patient s with HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) and controls. CMCTs in upper (U) and lower (L) limbs were significantly pro longed in HAM/TSP. L-CSCT was significantly prolonged in HAM/TSP, but U-CSC T in HAM/TSP and controls were not significantly different. CMCT and CSCT w ere significantly correlated in HAM/TSP. U-CMCT, but not L-CMCT, correlated with the clinical severity of HAM/TSP. Although F wave conduction velocity and its occurrence were normal in HAM/TSP, U- and L-mean F wave/M wave amp litude ratio tended to be higher in HAM/TSP, and the L-mean F wave/M wave a mplitude ratio was significantly correlated with the L- and thoracic CMCT. These findings demonstrate that the prolongation of CMCT sensitively reflec ts the extension of the lesions and the distribution to the anterior horn c ells in HAM/TSP. (C) 2001 Elsevier Science B.V. All rights reserved.