The authors performed the posterior tibial somatosensory evoked potentials (PTSEP) on 37 patients who had typical symptoms and signs of thoracic myelopathy to evaluate the value of the PTSEP in diagnosing ad differentiating among the thoracic
lesions.
The result showed the abnormal PTSEP features which were suggestive of thoracic myelopathy in 33 of 37(89.2%). The most frequent abnormalities were the prolonged central conduction (59.5%), which were either the only one (40.6%)or combined with
poor
wave formation (18.9%). The second commonabnormal PTSEP findings were the decreased P1 amlitude relative to TN1 amplitude with having normal value of TN1-P1 interwave latecies (29.7%). When e divided those 37 subjects into the demyelinating
(N=18),
the
prolonged TN1-P1 interwave latencies were more prominent in the demyelinating (68.4%) than in the non-demyelinating group (50.0%). In contrast, the only relative reduction of P1 amplitude with normal central conduction was more marked in the
non-demyelinating (38.9%) than in the demyelinating group (21.1%). However, both of them did ot show statistical significances (p<0.254, p<0.235, respectively).
The PTSEP methods were found super8ior to spine MRI in sensitivity in the demyelinating group, as the PTSEP revealerd abnormal findings in 12 subjects with normal spine MRI. But in the non-demyelinating group, theere was o significant difference
of
sensitivity or specificity between the PTSEP and the spine MRI.
Therefor it os concluded that the PTSEP studies would be helpful in diagnosing the thoracic lesions, especially in patients with the demyelinating lesions. However, those parammters of the proonged central conduction (TN1-P1) or the relative
amplitude
reduction of cortical patentials (P1) were not singificant in differentiating the deemyelinating from the non-demyelinating lesions.
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