Parameters of magnetic stimulation of the brain and somatosensory evoked potentials in the prediction of recovery of motor functions after ischemic stroke

Abstract

Objective: to estimate the significance of parameters of transcranial magnetic stimulation (TMS) of the brain and somatosensory evoked potentials (SSEPs) in the prediction of recovery of motor functions after ischemic stroke. Patients and methods. The study enrolled 63 patients (29 women and 34 men aged 41-5 years) in the acutest period of middle cerebral artery (MCA) basin infarct with evolving hemiplegia. In the first 5 days after stroke, TMS was performed in the projection of the motor cortex of the involved hemisphere, by recording a motor evoked response (MER) from m. tibialis anterior and m. pollicis brevis in hemiplegia; and SSEPs were recorded when stimulating n. medianus and n. tibialis in hemiplegia. The outcomes were assessed a year after stroke: muscle strength on a scale from 0 to 5 e and the Rivermead mobility index were studied. Results. A year later, there was either partial or full recovery of active lower and upper limb movements in 73.3 and 58.2%, respectively. With good and poor motor outcomes, the parameters of MCA rather than SSEPs differed significantly. The optimal threshold amplitude for MER from the lower and upper limbs was 0.25 and 0.3 mW, respectively; the time of central motor conduction was 22 and 19 msec for the lower and upper limbs, respectively. At the same time, TMS findings were insufficient for predicting a patient's mobility. The prognosis was determined by the data of TMS and the results of SSEPs: the best outcomes in movement recovery were noted when the prognosis was positive according to the data of TMS in combination with the preserved parameters of SSEPs in the study of cortical projections of the lower limb. Conclusion. It is expedient to perform TMS to estimate the probability of muscle strength recovery. The SSEPs method cannot determine the prognosis of muscle strength recovery; however, its results are of importance for estimating the promises of recovering a patient's mobility. Therefore, comprehensive neurophysiological examination is warranted.