P20-F Dynamics of MEP during corrective spinal surgery for idiophatic scoliosis

Abstract

The loss of transcranial motor evoked potentials (TcMEP) during spinal surgery is a great problem, because surgical team is required to adequately interpret the real-time changes in observed neuromonitoring and take a decision about further treatment policy. The purpose of this study is to determine the frequency of IOM events, the consideration of corrective actions, and patient outcomes during the surgical correction of Idiopathic scoliosis (IS). For that a total 150 cases of IOM surgery IS were retrospective analyzed. Patients were aged 5–43 years and underwent surgery between 2013 and 2017. The neurophysiology system for the surgeon “NIM-Eclipse system” (Medtronic) was used. MEP were registered on m.abdominis rectus, m.abdominis obliquus, m.vastus lateralis, m.tibialis anterior. Sixty-four (42.6%) cases were conducted on 200–250 V Tc power, MEP amplitudes were close to baseline and tended to increase to the interventions end. The IOM events were observed in 56 (37,3%) cases, when amplitudes were decreased more than 50% from baseline, but after increasing Tc power to 450–630 V the potentials returned to baseline. In 30 (20%) cases were observed loss MEP – in 24(80%) the potentials returned after washing the wound with a warm solution and rising arterial pressue; in 5 (16.6%) cases – after surgical correction actions; and 1 (3%) irreversible MEP loss case resulted lower paraplegia. The loss of MEP is a consequence of corrective maneuvers on the spine. It can be explained by long-term changes in the functioning of the spinal cord under conditions of its chronic compression, which leads to interruption of corticospinal conduction.