Evaluation of thoracic myelopathy by transcranial magnetic stimulation.

It is sometimes difficult to determine the appropriate surgical site in patients with thoracic myelopathy with diffuse or multisegmental lesions. To solve this problem, a magnetic stimulation study was carried out. Seven patients with myelopathy and 10 healthy control subjects were examined. Transcranial magnetic stimulation was applied and the motor evoked potentials (MEPs) of the intercostal muscles were recorded. The MEP latencies for the two groups were then compared. In patients with thoracic myelopathy, the MEP latencies caudal to the lesion were more extended than those of the control subjects. This method could identify the levels at which myelopathy originates in patients with a radiologically visible lesion. This method has the potential to be used for deciding the surgical site at the level responsible for myelopathy in cases with multiple or diffused compression.