Abstract
The purpose of this study was to compare and assess the ability of two different evoked potential (EP) modalities, median nerve somatosensory evoked potentials (SSEP) and brainstem auditory evoked potentials (BAEP) in monitoring for cerebral ischaemia and in predicting neurological outcome during posterior fossa aneurysm surgery. During 70 procedures, patients were monitored with both SSEP and BAEP Temporary occlusion of an artery was used in 52 patients and permanent occlusion in 21 patients. A change was defined as a greater than 50% decrease in amplitude and/or an increase in latency greater than 1 msec of the N20 (cortical waveform) for SSEP monitoring and of the fifth peak for BAEP monitoring. Neurological assessment of the patient was performed immediately on emergence, after 24 hr and at the time of discharge. In total, 14 patients had an SSEP change which predicted a neurological deficit in eight patients (57%). Ten patients had a change in BAEP; six had a neurological deficit (60%). Five patients had a change in both, two had a deficit (40%). The incidence of false negative results (a neurological deficit but no EP change) for both modalities was 20% (SSEP 47%, BAEP 60%). The incidence of false positive results (an EP change but no deficit) was 13% overall (SSEP 11%, BAEP 7%). All patients who had a permanent EP change developed a neurological deficit. We did not find a difference in the ability of SSEP compared with BAEP in predicting neurological deficits but, using both modalities, the incidence of false negative results was decreased. In conclusion, dual modality monitoring should be used whenever possible as neither modality alone was better than the other in detecting cerebral ischaemia and in predicting neurological deficits.
Résumé
Cette étude vise à évaluer et comparer la capacité de deux méthodes de mesure des potentiels évoqués (EP) pour le monitorage de l’ischémie cérébrale et pour la prédiction du pronostic neurologique pendant la chirurgie de la fosse postérieure: les potentiels évoqués somatosensoriels du nerf médian (SSEP) et les potentiels évoqués auditifs du tronc cérébral. Au cours de 70 interventions, on monitorise à la fois les SSEP et les BAEP. L’occlusion temporaire d’une artère est réalisée chez 52 patients et l’occlusion permanente chez 21 patients. Un changement est défini comme une baisse de l’amplitude de plus de 50% avec ou sans une augmentation de la latence de 1 msec de N20 (forme d’onde corticale) pour le moniteur de SSEP et du cinquième pic pour le moniteur de BAEP. Une évaluation neurologique est faite dès le réveil, après 24 h et au moment du congé. Au total, 14 patients ont montré des SSEP altérés qui ont permis la prédiction d’un déficit neurologique chez huit patients (57%). Dix patients ont montré des altérations de BAEP; six avaient un déficit neurologique (60%). Cinq patients avaient des altérations des deux; deux patients avaient un déficit (40%). L’incidence de faux négatifs (un de’ficit neurologique sans alteration dEP) pour les deux méthodes était de 13% (SSEP 11% BAEP 7%). Tous les patients avec un changement permanent de l’EP ont eu un déficit neurologique. Nous n’avons pas trouvé de différence entre la capacité des SSEP comparativement aux BAEP, pour la prédiction des déficits neurologiques, mais l’utilization concomitante des deux méthodes permet de diminuer l’incidence des faux négatifs. En conclusion, pour détecter l’ischémie cérébrale, comme une des méthodes seule est meilleure que l’autre, les deux méthodes devraient être associées lorsque possible.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Branston NM, Ladds A, Symon L, Wang AD. Comparison of the effects of ischaemia on early components of the somatosensory evoked potential in brainstem, thalamus, and cerebral cortex. J Cereb Blood Flow Metab 1984; 4: 68–81.
Meyer KL, Dempsey RJ, Roy MW, Donaldson DL. Somatosensory evoked potentials as a measure of experimental cerebral ischemia. J Neurosurg 1985; 62: 269–75.
Grundy BL. Intraoperative monitoring of sensory-evoked potentials. Anesthesiology 1983; 58: 72–87.
Little JR, Lesser RP, Luders H. Electrophysiological monitoring during basilar aneurysm operation. Neurosurgery 1987; 20: 421–7.
Friedman WA, Kaplan BL, Day AL, Sypert GW, Curran MT. Evoked potential monitoring during aneurysm operation: observations after fifty cases. Neurosurgery 1987; 20: 678–87.
Manninen PH, Lam AM, Nantau WE. Monitoring of somatosensory evoked potentials during temporary arterial occlusion in cerebral aneurysm surgery. J Neurosurg Anesthesiol 1990; 2: 97–104.
Schramm J, Koht A, Schmidt G, Pechstein U, Taniguchi M, Fahlbusch R. Surgical and electrophysiological observations during clipping of 134 aneurysms with evoked potential monitoring. Neurosurgery 1990; 26: 61–70.
Lam AM, Keane JF, Manninen PH. Monitoring of brainstem auditory evoked potentials during basilar artery occlusion in man. Br J Anaesth 1985; 57: 924–8.
Ljunggren B, Säveland H, Brandt L, K∘aaström, E, Rehncrona S, Nilsson PE. Temporary clipping during early operation for ruptured aneurysm: preliminary report. Neurosurgery 1983; 12: 525–30.
Jabre A, Symon L. Temporary vascular occlusion during aneurysm surgery. Surg Neurol 1987; 27: 47–63.
Lam AM. Monitoring neurological evoked responses.In: Barash PG (Ed.). The American Society of Anesthesiologists Refresher Course, J.B. Lippincott, 1989; 17: 175–92.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Manninen, P.H., Patterson, S., Lam, A.M. et al. Evoked potential monitoring during posterior fossa aneurysm surgery: a comparison of two modalities. Can J Anaesth 41, 92–97 (1994). https://doi.org/10.1007/BF03009798
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF03009798