SSEP Monitoring in Aneurysm Surgery

Tony Abraham, Thomas (2008) SSEP Monitoring in Aneurysm Surgery. Masters thesis, Christian Medical College, Vellore.

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Abstract

INTRODUCTION AND OBJECTIVES : This study evaluated the usefulness of somatosensory evoked potentials (SSEPs) for the monitoring of perfusion of a selected arterial territory during temporary arterial occlusion. Peroperative changes in amplitude of SSEPs were correlated with postoperative neurological function. METHODS : This was a prospective study of 47 patients who underwent clipping of anterior circulation aneurysms utilizing SSEPs for neurophysiological monitoring. Statistical analysis was done for 46 procedures where a temporary clip was applied for proximal control before application of the permanent clip. Decrease in amplitude of evoked potentials by 50% or more was considered a ‘significant change’. The motor status of a patient both pre and postoperatively was compared and correlated with intraoperative changes in amplitude. A ‘significant change’ in amplitude which did not revert to it’s baseline value was considered a positive test and a patient with a new postoperative deficit was considered a positive end point. RESULTS : Nine of the 46 procedures (19.5%) monitored with SSEPs had a significant decrease in amplitude after application of a temporary clip. In all cases, the amplitude reverted back to baseline value after removal of the clip. Three patients had new post operative motor deficits. Of these, two patients had a significant change in amplitude. The calculated specificity was 100% and negative predictive value was 94%. There was a greater proportion of MCA aneurysms (30.7%) that showed a significant change in amplitude compared to ACA (16.6%) and posterior communicating artery aneurysms (16.7%). The prevalance of significant change (out of the total number of clip applications) was greater in middle cerebral artery aneurysms (27.3%) compared to anterior cerebral artery (4.25%). There was no significant difference in the prevalence between ACA aneurysms with or without collateral supply from the opposite side (4.3% and 5% respectively). The average time taken for recovery to baseline following a decrease in amplitude was more than twice as long in ACA aneurysms without collateral supply ( 9 minutes ) than those with collateral supply (4 minutes). Intraoperative rupture of aneurysm was found to be associated with a higher average decrease in amplitude (61.5%) and prevalence of SSEP change (45.5%) than any other subgroup. CONCLUSIONS : SSEP monitoring during intracerebral aneurysm surgery has a high negative predictive value and specificity. Absence of a ‘significant change’ in amplitude during surgery is a good predictor of favourable outcome. Middle cerebral artery aneurysms show a greater propensity to produce ischaemia following temporary clip application compared to other arterial territories.

Item Type: Thesis (Masters)
Uncontrolled Keywords: SSEP-somatosensory evoked potentials, Monitoring, Aneurysm Surgery.
Subjects: MEDICAL > Neuro Surgery
Depositing User: Kambaraman B
Date Deposited: 02 Jan 2018 17:53
Last Modified: 02 Jan 2018 17:53
URI: http://repository-tnmgrmu.ac.in/id/eprint/5129

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