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The efficacy of motor evoked potentials in fixed sagittal imbalance deformity correction surgery.
Spine (Phila Pa 1976). 2008 Jun 01; 33(13):E414-24.S

Abstract

STUDY DESIGN

Retrospective analysis of transcranial motor evoked potential (TcMEP) responses and clinical outcome.

OBJECTIVE

To determine the sensitivity and specificity of TcMEPs to detect and predict isolated nerve root injury in selected patients having complex lumbar spine surgery.

SUMMARY OF BACKGROUND DATA

The surgical correction of fixed sagittal plane deformity involves posterior-based osteotomies and significant changes in the length of and space for the neural elements. The role of transcranial motor-evoked potential (TcMEP) monitoring in osteotomies below the conus has not been established. The purpose of this paper is to describe the relationship between neural complications from surgery and intraoperative TcMEP changes.

METHODS

We retrospectively studied 35 consecutive patients in a single center treated with posterior-based osteotomies for the correction of fixed sagittal plane deformity. Transcranial motor-evoked potentials, free-running and evoked electromyography data were assessed for each case. Analysis includes description of the intraoperative changes observed, and a correlation of changes with postoperative clinical findings.

RESULTS

Thirty-five consecutive patients underwent surgery for fixed sagittal plane deformity with complete neuromonitoring data. Twenty-five patients (71%) had an episode of greater than 80% reduction in MEP amplitude to at least 1 muscle. Fifteen of 25 had improvement of TcMEPs after repositioning of the legs (1), additional surgical decompression (4), or volume and pharmacologic resuscitation (10). All 15 of these awoke with no detectable neurologic injury. Ten patients (29%) had reduced TcMEP signals that did not improve despite further decompression and manipulation of the osteotomy site. All 10 had a greater than 67% drop in TcMEPs for at least 1 muscle persisting at the end of the case, and all had a postoperative neurologic deficit. The TcMEP changes in patients who demonstrated nerve injury postoperatively were observed most often during osteotomy closure or sustained dural retraction. 9 patients had weakness involving the iliopsoas or quadriceps; 1 patient had isolated unilateral dorsiflexion weakness. Monitoring TcMEPs in multiple muscle groups was both highly sensitive and specific for predicting injury. Nine patients had recovered motor function completely by discharge, and all but 1 patient (grade 4/5) had a normal motor examination at 6-week follow-up.

CONCLUSION

The use of TcMEPs is sensitive and specific to change in neural function. No patients had a false negative test. The rate of neural deficits is consistent with previous literature, suggesting that TcMEP monitoring may not prevent neural injury. However, there were several cases in which intraoperative intervention resulted in recovery of TcMEPs, and none of these patients sustained any postoperative neural deficit. The severity of neural deficits in this series was minor and the duration was limited. TcMEPs may contribute to calling attention to the need for intraoperative corrections including widening decompressions, improving perfusion, and limiting deformity correction so that more severe neural compromise may be prevented.

Authors+Show Affiliations

Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143-0648, USA. lieberman@anesthesia.ucsf.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

18520928

Citation

Lieberman, Jeremy A., et al. "The Efficacy of Motor Evoked Potentials in Fixed Sagittal Imbalance Deformity Correction Surgery." Spine, vol. 33, no. 13, 2008, pp. E414-24.
Lieberman JA, Lyon R, Feiner J, et al. The efficacy of motor evoked potentials in fixed sagittal imbalance deformity correction surgery. Spine. 2008;33(13):E414-24.
Lieberman, J. A., Lyon, R., Feiner, J., Hu, S. S., & Berven, S. H. (2008). The efficacy of motor evoked potentials in fixed sagittal imbalance deformity correction surgery. Spine, 33(13), E414-24. https://doi.org/10.1097/BRS.0b013e318175c292
Lieberman JA, et al. The Efficacy of Motor Evoked Potentials in Fixed Sagittal Imbalance Deformity Correction Surgery. Spine. 2008 Jun 1;33(13):E414-24. PubMed PMID: 18520928.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The efficacy of motor evoked potentials in fixed sagittal imbalance deformity correction surgery. AU - Lieberman,Jeremy A, AU - Lyon,Russ, AU - Feiner,John, AU - Hu,Serena S, AU - Berven,Sigurd H, PY - 2008/6/4/pubmed PY - 2008/7/11/medline PY - 2008/6/4/entrez SP - E414 EP - 24 JF - Spine JO - Spine VL - 33 IS - 13 N2 - STUDY DESIGN: Retrospective analysis of transcranial motor evoked potential (TcMEP) responses and clinical outcome. OBJECTIVE: To determine the sensitivity and specificity of TcMEPs to detect and predict isolated nerve root injury in selected patients having complex lumbar spine surgery. SUMMARY OF BACKGROUND DATA: The surgical correction of fixed sagittal plane deformity involves posterior-based osteotomies and significant changes in the length of and space for the neural elements. The role of transcranial motor-evoked potential (TcMEP) monitoring in osteotomies below the conus has not been established. The purpose of this paper is to describe the relationship between neural complications from surgery and intraoperative TcMEP changes. METHODS: We retrospectively studied 35 consecutive patients in a single center treated with posterior-based osteotomies for the correction of fixed sagittal plane deformity. Transcranial motor-evoked potentials, free-running and evoked electromyography data were assessed for each case. Analysis includes description of the intraoperative changes observed, and a correlation of changes with postoperative clinical findings. RESULTS: Thirty-five consecutive patients underwent surgery for fixed sagittal plane deformity with complete neuromonitoring data. Twenty-five patients (71%) had an episode of greater than 80% reduction in MEP amplitude to at least 1 muscle. Fifteen of 25 had improvement of TcMEPs after repositioning of the legs (1), additional surgical decompression (4), or volume and pharmacologic resuscitation (10). All 15 of these awoke with no detectable neurologic injury. Ten patients (29%) had reduced TcMEP signals that did not improve despite further decompression and manipulation of the osteotomy site. All 10 had a greater than 67% drop in TcMEPs for at least 1 muscle persisting at the end of the case, and all had a postoperative neurologic deficit. The TcMEP changes in patients who demonstrated nerve injury postoperatively were observed most often during osteotomy closure or sustained dural retraction. 9 patients had weakness involving the iliopsoas or quadriceps; 1 patient had isolated unilateral dorsiflexion weakness. Monitoring TcMEPs in multiple muscle groups was both highly sensitive and specific for predicting injury. Nine patients had recovered motor function completely by discharge, and all but 1 patient (grade 4/5) had a normal motor examination at 6-week follow-up. CONCLUSION: The use of TcMEPs is sensitive and specific to change in neural function. No patients had a false negative test. The rate of neural deficits is consistent with previous literature, suggesting that TcMEP monitoring may not prevent neural injury. However, there were several cases in which intraoperative intervention resulted in recovery of TcMEPs, and none of these patients sustained any postoperative neural deficit. The severity of neural deficits in this series was minor and the duration was limited. TcMEPs may contribute to calling attention to the need for intraoperative corrections including widening decompressions, improving perfusion, and limiting deformity correction so that more severe neural compromise may be prevented. SN - 1528-1159 UR - https://www.unboundmedicine.com/medline/citation/18520928/The_efficacy_of_motor_evoked_potentials_in_fixed_sagittal_imbalance_deformity_correction_surgery_ L2 - http://dx.doi.org/10.1097/BRS.0b013e318175c292 DB - PRIME DP - Unbound Medicine ER -