Prognostic significance of no recovery of motor evoked potentials and H-reflex in open thoracoabdominal aortic repair

Objective. To evaluate prognostic value of reversible and persistent intraoperative changes in somatosensory evoked potentials, motor evoked potentials and H-reflex for postoperative motor neurological deficit after open thoracoabdominal aortic replacement. Material and methods. A single-center prospective observational study included 59 patients who underwent open thoracoabdominal aortic replacement under intraoperative neurophysiological monitoring. Somatosensory evoked potentials were recorded in 58 patients (98.3%), motor evoked potentials in 54 (91.5%), and H-reflex in 24 (40.7%) patients. The primary endpoint was new postoperative motor neurological deficit. Diagnostic performance of any signal decrease and no recovery by the end of surgery was assessed. An exploratory analysis of surgical factors associated with persistent absent recovery of motor evoked potentials and/or H-reflex was also performed. Results. Postoperative spinal cord ischemia was detected in 4/59 patients (6.8%): 3 cases of monoparesis (5.1%) and 1 case of paraplegia (1.7%). Any evoked potential decrease had high sensitivity but low specificity. No recovery of somatosensory evoked potentials among patients with their decrease had 25.0% sensitivity and 95.1% specificity. No recovery of motor evoked potentials had 75.0% sensitivity and 71.4% specificity, no recovery of H-reflex — 100.0% sensitivity and 53.3% specificity. The combined criterion of no recovery of motor evoked potentials and/or H-reflex demonstrated 100.0% sensitivity, 70.6% specificity and 100.0% negative predictive value. In exploratory analysis of surgical factors, significant difference was found in the number of intraoperatively sutured thoracic intercostal arteries: 4 [3; 5] in the absent recovery group versus 6 [4; 8] in the recovery group (p=0.048). Conclusion. Persistent abnormalities remaining by the end of surgery have the greatest prognostic value rather than any intraoperative signal decrease. No recovery of motor evoked potentials and/or the H-reflex may be considered a clinically relevant risk factor for postoperative motor deficit.