[Identification of motor area by transcranial magnetic stimulation using an "eight-figure" coil in patients with...

In patients with motor paralysis, we tried to identify the functional motor area by transcranial magnetic stimulation using an "eight-figure" coil designed by Ueno. Motor evoked potentials (MEPs) were recorded in 7 patients from 50 to 64 years old, and in 5 normal volunteers 26 to 45 years old. They were stimulated at 49 points over an unilateral hand motor area, and at 21 points over a foot motor area, and surface MEPs were recorded on their contralateral thenar muscle and abductor hallucis brevis muscle. In normal volunteers, the optimal eddy current for stimulating the hand motor area was directed anteriorly parallel to the midline, and for stimulating the foot motor area, it was postero-laterally directed with an angle of 45 degrees towards the midline. MEPs could be induced at their muscle contractions during which their thumbs and middle fingers softly touched each other, and their halluxes slightly flexed. In five patients two kinds of amplitude mappings reconstructed from MEPs were obtained at rest or at muscle contraction. A line connecting these two peaks on an amplitude mapping was regarded as an "MEP-motor area". A geographical difference between the MEP-motor area and MRI-motor area (identified by an MRI surface image) was studied at muscle contraction and at rest. In normal subjects the sites of the MEP-motor area and of the MRI-motor area coincided, whereas, in patients with space-occupying lesions near the central sulcus, the MEP-motor areas were located 1 to 2cm posterior to MRI-motor areas.(ABSTRACT TRUNCATED AT 250 WORDS)