Premotor and Motor Brain Cortex Responses to Transcranial Magnetic Stimulation in Hemiparetic Patients Assessed by Motor Threshold

Objective: To assess the excitability and the function of premotor and primary motor brain cortex by determination of the motor threshold (MT) of gaining arms and legs motor responses using transcranial magnetic stimulation (TMS). Material and methods: The study was performed in 10 patients with residual hemiparesis after ischemic stroke. A comparison have been made of MT for muscle contraction in the sound and paretic arm and leg by TMS at Cz, C-3, or C-4 and CF1 or CF2 of the normal or damaged hemisphere (combined with facilitation by light muscle contraction in four limbs). Results: In primary motor cortex involvement the responses have been lacking or elicited by higher intensity. In some patients the normal reactivity to TMS in the four limbs at the same time, when stimulating premotor cortex (CF1, CF2) was disturbed. The stimulation over the healthy hemisphere premotor cortex shows on the contrary an increased projection over the ipsilateral paretic limbs, more to the leg and proximal muscles in arm. Discussion: The application of TMS offers a possibility to test the primary motor, and the premotor cortex responses in patients with post-stroke hemiparesis. The new method of MT comparement in four limbs is a functional test, giving information for the status, and respectively the prognosis of such patients as far as the premotor area is involved in mass movements, synergies, and in pathology - in releasing phenomena, like spasticity, clonus and pathologic static synergy and gate of Wernicke-Mann type.