Letter to the Editor

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To the Editor:

Bo et al¹ studied cognitive testing before and a mean of 44.4 months after carotid endarterectomy (CEA) in 103 consecutive patients. They reported greater cognitive decline in symptomatic patients undergoing left internal carotid artery (LICA) operation compared with other groups having CEA. In their discussion, they state “our results suggest that patients with LICA disease might benefit in the prevention of cognitive decline from endarterectomy before the occurrence of cerebrovascular ischemic symptoms.”

The study has some methodologic flaws that may render that suggestion specious. The authors do not report any postoperative complications. From the large clinical trials, we know that after CEA, symptomatic stroke plus death rates will vary from just under 2% for asymptomatic patients to about 6% for symptomatic patients.², ³ Considering the small number of patients in each subgroup analyzed in this report, the difference of one or two postoperative strokes could account for the difference in results between symptomatic and asymptomatic patients with LICA.

A greater methodologic problem is the failure to do immediate postoperative imaging and cognitive testing. Owens et al⁴ assessed postendarterectomy cognitive function by performing imaging and cognitive testing after CEA. Even with the older, less sensitive imaging modalities used in that trial, they discovered a surprising number of asymptomatic infarcts in the distribution of the operated vessel. It is possible that patients in this trial had clinically asymptomatic infarcts in the distribution of the operated vessel.

If we assume a higher rate of asymptomatic postoperative infarcts in the symptomatic patients compared with the asymptomatic patients in this trial, this could explain the greater degree of abnormality in the symptomatic patients at follow-up testing. If we assume the cognitive testing done in this study is more sensitive to dominant hemisphere lesions compared with nondominant, this would explain the patients with LICA having greater abnormality on postoperative cognitive testing.

Based on the data presented in this article, one might conclude that operating on symptomatic LICA has a causative association with cognitive decline. Rather than changing our practice to recommend a lower threshold for recommending CEA on asymptomatic left carotid stenosis, based on these results, perhaps we should be raising the threshold for recommending CEA for patients with symptomatic LICA stenosis. For these patients, CEA might decrease the risk of future stroke but increase the risk for cognitive decline. After reviewing these data, I will be even more cautious about recommending CEA for patients with LICA stenosis in the 50% to 69% range that will derive only a modest potential benefit from the procedure.

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References 

1. Bo M , Massaaia M , Speme S , et al.   Cognitive function after carotid endarterectomy (Greater risk of decline in symptomatic patients with left internal carotid artery disease) . J Stroke Cerebrovasc Dis . 2005;14:221–228
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2. Executive Committee for Asymptomatic Carotid Atherosclerosis Study Group (ACAS) . Endarterectomy for asymptomatic carotid artery stenosis . JAMA . 1995;273:1421–1428
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3. Barnett HJM , Taylor DW , Eliasziw M , et al.  NASCET Collaborators   Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis . N Engl J Med . 1998;339:1415–1425
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4. Owens M , Pressman M , Edwards AE , et al.   The effect of small infarcts and carotid endartectomy on postoperative psychological test performance . J Surg Res . 1980;28:209–216
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