The set involves 23 consecutive patients evaluated by transcranial electrical stimulation with registration of motor evoked potentials (MEP) during a surgery. 15 patients underwent the surgery for the brain tumor, 6 patients for the spinal cord tumor, and 2 patients for thoracic discopathy. General anesthesia with combination of isofluran with suphentanyl was used in 19 cases, and continuous intravenous anaesthesia (TIVA) with a combination of propofol and suphentanil in 4 cases. The response was elicited from all patients with TIVA. In the group where general anesthesia with isofluran and opioid was used 3 patients demonstrated either significant overall decrease of amplitude or total loss of all motor responses. No other reason than the concentration of an anesthetic agent above 0.6 % was found. Based on these results TIVA is preferred as the optimal anesthesiologic regimen for monitoring MEPs. The motor response was succesfully registered in 19 cases. A changed MEP during the critical phase of surgery was recorded in 7 cases. Significant decrease of amplitude below 50 % was observed in 4 patients, and total loss of response appeared in 3 patients. Moderate (2 patients) or severe (1 patient) worsening of motor functions was revealed in these cases after surgery. 12 patients with normal MEPs during surgery were without a motor deficit after an operation. A mild motor deficit developed in 2 patiens with the amplitude decreased below 50 %, the other 2 cases showed the normal motor function.

        Key words: transcranial electrical stimulation, MEP, intraoperative monitoring, anesthesia