(Stroke. 1999;30:895.)
© 1999 American Heart Association, Inc.
Letters to the Editor |
No Absolutes in Neuromonitoring for Carotid Endarterectomy
Department of Neurological Surgery, Presbyterian University Hospital, University of Pittsburgh, Pittsburgh, Pennsylvania
Key Words: evoked potentials • somatosensory intraoperative
monitoring
To the Editor:
I have some concerns about the recently published study by Beese et al.1 While I applaud the number of patients they studied, they misled the readers regarding the reliability of somatosensory evoked potentials (SEP) for carotid endarterectomies. I question the validity of their data because of their description of sensor location, inadequate data presentation, and conclusions that are not warranted by their results. I also disagree with some of the points raised in their discussion.
To their credit, the authors addressed some of these concerns, but inadequately, I believe. My 5-year experience with near-infrared spectroscopy (NIRS), the NIRO 500, and the INVOS 3100A and 4100 convinces me that the INVOS accurately measures brain hemoglobin oxygenation even in pathological states. Understanding what is being measured and how best to apply it in its many potential and untested uses is the challenge before us.
First, the authors tacitly imply that SEP monitoring is 100% sensitive and specific by stating that the avalidity of SEP has been established. In fact, previous studies involving 200 to 500 patients report sensitivity of 60% to 100% and specificity of 94% to 100%.2 3 4 No neuromonitoring technique monitors the entire brain. SEP monitors the somatosensory strip over the postcentral gyrus. The middle cerebral artery feeds most of the cerebral cortex and is most likely to be affected by carotid clamping. Frontal placement of the sensor monitors part of the ACA and MCA arterial distributions.
The authors also chose the aloss of SEP, where the N20