EVALUATION OF CENTRAL MOTOR CONDUCTION IN HYPOTHYROID AND HYPERTHYROID PATIENTS

Deficiency or excess of thyroid hormones is associated with central ne rvous system (CNS) disturbances. Although the CNS involvement either i n hypothyroidism or in hyperthyroidism have previously been shown on t he basis of visual, auditory and somatosensory evoked potentials studi es, less is known about the function of central motor pathways in both disorders. We studied the motor evoked potentials (MEPs) following th e magnetic stimulation of the motor cortex and spinal roots in 20 pati ents with hypothyroidism and in 19 patients with hyperthyroidism both before treatment and after they became euthyroid and compared with fin dings in 20 age-, sex- and height- matched control subjects. Disease d uration (expressed as time from diagnosis of diseases to the time of n eurological testing) is less than one month in both disorders. Central motor conduction time (CMCTJ was determined as the differences betwee n MEPs latencies after cortical and spinal stimulation. The mean CMCTs before treatment in hypothyroid patients (8.31 +/- 1.52 msec,) and in hyperthyroid patients (7.92 +/- 1.06 msec,) were significantly prolon ged as compared to those in normal controls (6.82 +/- 0.83 msec, p = 0 .002 and p = 0.004, respectively). Four of the 20 (20.0%) hypothyroid patients and 2 of 19 (10.5%) hyperthyroid patients had abnormal CMCT ( values exceeding mean + 2.5 SD of normal control); The mean CMCT value s in both groups were not significantly decreased after euthyroidism w as achieved, although a tendency of the decrease in CMCT was observed. Improvement of CMCT abnormalities was observed in 1 of 4 hypothyroid patients and in one of 2 patients with hyperthyroidism, who had CMCT a bnormalities before treatments, after they became euthyroid. No correl ation was found between CMCT and free T-3, free T-4, or TSH levels as well as the onset age, the severity of the diseases or the disease dur ation in both disorders. We conclude that abnormal CMCT could be docum ented in few patients in both disorders. However, these alterations co uld not be improved completely after restoration of euthyrodism. Thus, it remains to be determined if long-term treatment would completely i mprove CMCT abnormalities in both disorders. Since abnormal CMCT value s in both disorders were observed only in few patients, our results al so suggest that CMCT measurement does not have, at present time, a cli nical usefullness to assess the peripheral action of thyroid hormones. Thus, the data obtained need a more extensive evaluation. (C) 1996, E ditrice Kurtis