Dermatomal sensory examinations have been done usually for the patients with thoracic spinal cord lesion because there is no optimal method of motor evaluation, clinically. And also it is difficult to define the level of the thoracic lesions, electrodiagnostically. Intercostal somatosensory evoked potentials (SEPs) are easy to elicit and can evaluate the focal lesion from the intercostal nerve to the cortex through the thoracic cord. The purpose of this study was to determine the clinical usefulness of intercostal SEPs in the thoracic cord lesions. Intercostal SEPs were achieved by the third(T3), fifth(T5), seventh(T7), and ninth(T9) intercostal nerve stimulation. We examined 20 healthy controls and 10 patients with thoracic spinal cord lesions. In controls, the mean P1 latencies were 22.98±1.56msec for the third intercostal SEPs (T3),24.57±1.73msec for the fifth intercostal SEPs (T5), 27.72±2.07msec for the seventh intercostal SEPs (T7), and 28.07±3.34msec for the ninth intercostal SEPs (T9). The mean N1 latencies for T3, T5, T7 and T9 were 30.84±1.63msec, 32.68±2.09msec, 33.65±1.98msec and 35.76±2.66msec, respectively. The P1 and N1 latencies were increased gradually from T3 to T9 segment one by one. The P1-N1 amplitudes in controls for T3, T5, T7 and T9 were 1.65±0.78uV, 1.30±0.57uV, 1.37±0.60uV and 1.39±0.59uV, respectively. The inconsistency of waveforms or no response at certain level was the most important finding in the patients with thoracic cord lesions. In conclusion, the intercostal SEPs study is a complementary examination to evaluate the thoracic cord lesions in addition to clinical and electromyographic examinations. But it can not be applied below T9 level because of the inherent anatomic limitations of the method. |