Abstract
Purpose
To compare the incidence and nature of ‘neurophysiological events’ identified, post hoc, by a consultant neurophysiologist with those identified intra-operatively by clinical physiologists, before and after intervention(s).
Methods
The IOM wave-recordings, event-logs and reports of all spinal deformity cases conducted by a team of clinical physiologists from April to June 2009 (Group 1) were reviewed retrospectively by the same, experienced clinical neurophysiologist, (MG).
Interventions were then agreed. The first was to alter the IOM report document to drop down menus. The second was to arrange a series of teaching sessions for the clinical physiologists on a variety of aspects of IOM. Finally during these teaching sessions recent cases were brought to review in an informal setting to discuss.
Following implementation of the interventions a further review from April to June 2010 (Group 2) was carried out in the same manner.
The clinical physiologists did not know the time periods over which the review would be taking place.
Results
From April to June 2009 (Group 1) thirty two patients were studied and from April to June 2010 (Group 2) thirty four patients were studies.
Group 1
Twenty seven of these had been monitored using ‘multimodal’ IOM consisting of cortical (CSEP) and spinal (SSEP) somatosensory evoked potentials and motor (MEP/CMAP) evoked potentials. Two patients were inappropriate for MEP recording and two were monitored using epidural SSEP recording.
During 10 operations (31%) the surgeons were notified of an ‘intra-operative neurological event’ judged by the clinical neurophysiologist as potentially requiring a surgical response.
When the results were audited, only 2 (6%) of these ‘events’ were considered by the consultant clinical neurophysiologist to represent ‘true positive’ intra-operative neurophysiological findings.
Group 2
Twenty six of these had been monitored using ‘multimodal’ IOM consisting of cortical (CSEP) and spinal (SSEP) somatosensory evoked potentials and motor (MEP/CMAP) evoked potentials. Four patients were inappropriate for MEP recording and had a combination of SSEP and CSEP. The remainder had IOM with unimodal. No epidural IOM was used during this period.
During 4 operations (12%) the surgeons were notified of an ‘intra-operative neurological event’ judged by the clinical neurophysiologist as potentially requiring a surgical response.
Post-operative examination of all the patients in both groups revealed that no ‘false negative’ conclusions had been reached.
Conclusion
In this series clinical physiologists were found to alert the surgeons 5 times more frequently than was likely to have been the case with an experienced consultant clinical neurophysiologist (31% and 6% respectively). However the increased reporting of intra-operative events did not result in any alteration of the ultimate surgical strategy in any operation although tactical changes were sometimes necessary during the operation in order to test the reversibility of the flagged event.
The implementation of two simple interventions resulted in the clinical physiologists alerting the surgeons only 1/3 of that previously (12%) of cases.
The log indicated that on all occasions appropriate surgical action had been taken with no residual neurological deficit.
This study, owing to its size, cannot answer the key question of safety. Further work to estimate the statistical power required of such a study is being sought. In the interim proving a track record of successful cases provides evidence of efficacy.
Ethics Approval: None.
Interest Statement: None.
