1. Registration of MEPs is a highly sensitive and highly specific method for diagnosing corticospinal tract dysfunction in patients with intramedullary tumors of the cervical spinal cord. The sensitivity and specificity of MEPs recorded from the upper limbs are higher than those from the lower limb muscles. 2. The sensitivity of MEPs in patients with extramedullary intradural tumors was 0%, the diagnostic effectiveness of MEPs amounted to 86% from the upper limb muscles and 93% from the lower limb muscles. 3. When the MEP amplitude in patients with extra- and intramedullary tumors of the cervical spinal cord decreases, a change in the surgion's approach may reduce or completely eliminate surgically-induced damage to the spinal cord.