Prediction of the post-comatose motor function by motor evoked potentials obtained in the acute phase of traumatic and non-traumatic coma.

OBJECTIVE: To define the value of electrically elicited motor evoked potentials (MEP), obtained during the initial phase of the coma, for correct prediction of the post-coma motor status. METHODS: Fifty-two patients were investigated by MEP within 72 hours after onset of the coma. It was the aim to correlate the MEP findings to the motor function two months after coma onset. RESULTS: Three patients with normal MEP showed no post-coma motor deficit. In 21 patients, a bilateral, symmetric prolongation of the central motor conduction time (CMCT) was registered. Eighteen of these 21 patients (86%) showed a normal post-coma motor status. In 28 patients, unilaterally absent evoked potential, or unilaterally prolonged CMCT, or bilaterally prolonged CMCT with significant difference in each hemisphere were observed. A post-coma contralateral paresis was found in 25 of these 28 patients (89%). That paresis was functionally important in 15 patients (54%) and functionally unimportant in 13 patients (46%). CONCLUSION: We identified certain MEP patterns (unilateral extinction of the evoked potential, unilateral, bilateral prolongation of the CMCT with significant "side" difference), which indicated a pyramidal tract lesion and a post-coma motor deficit with an accuracy of 89%. This refers to the motor results, which may not be the final post-coma motor results which are usually assessed six months after the coma onset. The MEP changes did not allow one to predict the severity of the paresis. The accuracy of prediction of a motor deficit increased from the MEP finding of unilaterally prolonged CMCT to the MEP finding of unilateral extinction of the potential. The most common finding, bilateral central motor slowing without significant "side" difference, did not indicate a post-coma paresis in 86%, leading to the assumption, that bilateral, symmetrical prolongation of the CMCT was not caused by lesions of the descending motor pathways, but by the drugs administered for treating the comatose patient. In conclusion, MEP allows one to predict the presence of a post-coma motor deficit with a high degree of accuracy already in the initial phase of coma, but MEP fails to predict the severity of that deficit.