Document Detail

Observations on intraoperative somatosensory evoked potential (SEP) monitoring in the semi-sitting position.
MedLine Citation:
PMID:  12464339     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Former case reports suggest that monitoring of median nerve somatosensory evoked potentials (M-SEP) is unreliable in patients operated in the semi-sitting position due to the occurrence of evoked potential changes unrelated to neurological damage. This study was designed to analyze these changes in greater detail and confirm that these changes are not caused by neurological damage. METHODS: M-SEP monitoring findings of 50 patients with surgery in the semi-sitting position were analyzed and compared with a group of 50 patients who underwent surgery in the supine position. M-SEP amplitudes and latencies at distinct steps of the monitoring procedure were used for further analysis. In 10 of the 50 semi-sitting patients, M-SEP were recorded additionally after surgery with the anesthetized patient in the supine position. RESULTS: Significant M-SEP changes occurred in the semi-sitting patients only. An amplitude loss of greater than 50% on at least one side was observed in 24 patients. The magnitude and the time course of the amplitude loss was considerably variable. A complete loss of the evoked potential was not observed in any case. In all 10 patients, M-SEP recovered completely when recorded in the supine position. CONCLUSIONS: In about half of the patients with M-SEP monitoring in the semi-sitting position, a significant amplitude loss occurs which is unrelated to neurological damage and presumably caused by subdural gas collections. There is no characteristic pattern of M-SEP changes which enables a differentiation of these 'artificial' alterations from true events. The only appropriate criterion to indicate an impending neurological damage in these patients seems to be a complete loss of the M-SEP potential.
Helmut Wiedemayer; Heike Schaefer; W Armbruster; M Miller; Dietmar Stolke
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology     Volume:  113     ISSN:  1388-2457     ISO Abbreviation:  Clin Neurophysiol     Publication Date:  2002 Dec 
Date Detail:
Created Date:  2002-12-04     Completed Date:  2003-02-11     Revised Date:  2008-09-10    
Medline Journal Info:
Nlm Unique ID:  100883319     Medline TA:  Clin Neurophysiol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  1993-7     Citation Subset:  IM    
Department of Neurosurgery, University of Essen Medical School, Hufelandstr. 5545122, Essen, Germany.
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MeSH Terms
Analysis of Variance
Child, Preschool
Confidence Intervals
Evoked Potentials, Somatosensory / physiology*
Middle Aged
Monitoring, Intraoperative / methods*
Observation / methods*
Posture / physiology*

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