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Home > Vascular Annual Meeting > keyhani_analysis_motor

Analysis of Motor and Somatosensory Evoked Potentials During Thoracic and Thoracoabodminal Aortic Aneurysm Repair

Kourosh Keyhani, Paul Achouh, Charles C. Miller, III, Ali Azizzadeh, Sheila M. Coogan, Anthony L. Estrera, Adel Irani, Tara Wegryn, Hazim J. Safi.
University of Texas Medical School Houston, Houston, Texas.
 
OBJECTIVES: Use of evoked potential monitoring of neurological function during thoracic and thoracoabdominal aortic surgery is common. Some groups use somatosensory evoked potentials (SSEP), while others use motor evoked potentials (MEP). The purpose of the study was to evaluate the intraoperative use of SSEP and MEP during thoracoabdominal repair.

METHODS: We conducted paired SSEP and MEP monitoring to assess agreement between the methods and their ability to predict neurological outcome in 176 consecutive patients. Change was classified as no change, reversible change, or irreversible change intraoperatively. Agreement between the methods was computed using Cohen’s Kappa statistic, and sensitivity, specificity and positive and negative predictive values were computed for each method on immediate and delayed neurologic deficit.

RESULTS: Immediate neurologic deficit occurred in 4/176 (2.3%) of cases. For any change (reversible plus irreversible), agreement between MEP and SSEP was relatively low, (Kappa 0.61), despite being highly statistically significant (p<0.001). MEP tended to overestimate SSEP for this measure, demonstrating a 53% false positive rate, compared to a 36% false positive rate for SSEP. With irreversible change, agreement between the methods was 100% (Kappa 1.0, p<0.0001). Only irreversible change was significantly associated with neurologic outcome (OR 11.1, p<0.02), but sensitivity and positive predictive values were very low (25 and 17%, respectively). Reversible changes were not significantly associated with immediate neurologic deficit. Negative predictive values for all negative evoked potential findings were high (>98%) for immediate deficit. No evoked potential variables were associated with delayed deficit.

CONCLUSIONS: Somatosensory and motor evoked potential monitoring were well correlated only when intraoperative changes were irreversible. Irreversible changes were significantly associated with immediate neurologic deficit, and the findings were identical for SSEP and MEP in this variable, indicating that the more complex MEP measures do not add further information to that obtained from SSEPs. Normal SSEP and MEP findings had a strong negative predictive value, indicating that patients without signal loss are unlikely to awake with neurologic deficit.

AUTHOR DISCLOSURES: K. Keyhani, None; P. Achouh, None; C.C. Miller, None; A. Azizzadeh, None; S.M. Coogan, None; A.L. Estrera, None; A. Irani, None; T. Wegryn, None; H.J. Safi, None.