5. Henriksson A, Kam-Hansen S, Link H. IgM, IgA and I& pro- ducing cells in cerebrospinal fluid and peripheral blood in rnulti- ple sclerosis. Clin Exp Immunol 1985;62:176-184

6. Strandberg-Pedersen N, Kam-Hansen S, Link H, Mavra M. Specificity of immunoglobulins synthesized within the central nervous system in neurosyphilis. Acta Pathol Microbiol Immunol

7. Oxelius V, Rorsman H, burell A-B. Immunoglobulins of cere- brospinal fluid in syphilis. Br J Vener Dis 1969;45:121-125

Sand [C] 1982;90:97-104

The Value of Intraoperative Monitoring During Carotid Endarterectomy: A Comment John Davenport, MD

It was surprising to find the article by Cho and colleagues on electroencephalographic (EEG) monitoring during carotid endarterectomy [l) published in the Annals. This report is similar to many appearing in the surgical literature in the past ten years, in that while the authors may be justifiably pleased with the trend in operative morbidity after the institution of this procedure, the data presented do not support their con- clusion that the monitoring was directly, or perhaps even indirectly, responsible for the improvement. Although three factors are cited to account for the apparent benefits of EEG- selective shunting-“more accurate prediction of marked cerebral ischemia . . . ,” the “subsequent reduction of the frequency of apparently unnecessary shunts,” and “improved technical results when adequate cerebral perfusion and func- tion has been maintained during surgery”-these are all only restatements of the rationale for the procedure and not con- clusions based on assessment of the cases presented.

Only one of the 10 patients in the entire series who suf- fered neurological morbidity did so during the operation itself, and might therefore have benefited from EEG infor- mation had the procedure been performed. Even this specu- lation is weakened by the fact that this patient was consid- ered high risk and temporarily shunted but suffered “marked intraoperative hypotension” (timing unstated), which doubt- less contributed to, if not entirely determined, his unfortu- nate outcome. All 9 other patients sustained ischemic events at least a day into the postoperative period, and thus the events are quite unlikely to have been related to either clamp-induced ischemia or shunt-related embolic events. Moreover, all of the EEG-monitored patients with these complications had neither electrographic changes nor shunts placed.

Most thoughtful surgeons would likely agree that meticu- lous surgical technique is the major determinant of low oper- ative morbidity, and that perhaps “the more favorable neurological outcome may be attributed primarily [emphasis added] to the performance of unhurried and uncomplicated endarterectomies in the higher-risk, selectively unshunted

[emphasis added] patients” [ 11. This reasoning would logi- cally require that the authors’ unmonitored cohort under- went relatively anxious and therefore possibly rushed proce- dures, which led indirectly to late embolic complications. If it is true that there are few, if any, false negative intraoperative EEGs [2) when careful technical procedures are followed [37, then the predictive value of a normal EEG may be more powerful than that of an abnormal one. This still leaves unre- solved the appropriately controversial question of whether temporary shunts, placed on whatever indication, are more risky than beneficial 147.

Until the predictive value of EEG or any other decision- making technology is firmly established by scientific con- trolled trial-which of necessity would require not shunting patients with EEG changes-its continued “routine use in carotid artery surgery” appears to be not only unjustified, but very likely unethical as well IS].

EEG Lboratov V A Medical Center Minneapolis, MN 5541 7

References 1. Cho I, SrnuJlens SN, Streletz LJ, et al. The value of intraoperative

EEG monitoring during carotid endarterectorny. Ann Neurol

2. Sundt TM, Sharbrough FW, Piepgras DG, et al. Correlation of cerebral blood flow and electroencephalographic changes during carotid endarterectomy. Mayo Clin Proc 1981;56:533-543

3. Chiappa KH, Burke SR, Young RR. Results of electroencepha- lographic monitoring during 367 carotid endarterectomies: use of a dedicated minicomputer. Stroke 1979;10:381-388

4. Blume WT, Ferguson GG, McNeill DK. Significance of EEG changes at carotid endarterectomy. Stroke 1986;17:891-897

5 . Gilbert JP, McPeek B, Mosteller F. Statistics and ethics in surgery and anesthesia. Science 1977;198:684-689

1986;20:508-512

I ntraoperative Monitoring During Carotid Endarterectomy Dennis E. Wilkins, M D

Cho and colleagues 113 address the value of electroencepha- lographic (EEG) monitoring during operations on symptom- atic carotid arteries. Their report, in my view, warrants criti- cism on a number of grounds.

First, the possible mechanism(s) of the reported vascular events is inadequately discussed; the pathophysiology may be quite irrelevant to the presence or absence of EEG moni- toring and vascular shunting. For example: “The timing of perioperative stroke is consistent with the emerging litera- ture supporting the arterial wound site as a source of sig- nificant postoperative thrombus andlor embolus formation” [2]. In fact, of the 8 vascular events recorded during Cho and co-workers’ nonmonitored surgery, 6 transient ischemic at- tacks were noted in the “early postoperative days.” The seventh event, an ultimately fatal stroke, was associated with

Annals of Neurology Vol 22 N o 2 August 1987 283