COLUMBUS, OHIO – The primary goal of carotid artery revascularization is to prevent stroke, heart attack or death, but carotid artery stenting and carotid endarterectomy may also cause changes in cognitive skills, according Raghu Motaganahalli, MD, of the Indiana University, Indianapolis.
“What about cognitive dysfunction as a result of carotid artery stenting (CAS) or carotid endarterectomy (CEA)?” Dr. Motaganahalli asked at the annual meeting of the Midwestern Vascular Surgical Society. “I think this is real, that there’s some truth to the matter. The question is how much and what domains of cognitive functions are affected?”
“Cerebrovascular hemodynamics status plays a role in cognitive function, but we need a better understanding of cerebrovascular hemodynamic failure and either improvement or decline of cognitive function after CAS or CEA,” he said.
A review of published trials shows that 10%-20% of patients who have either CAS or CEA have some degree of cognitive dysfunction as early as a day after the procedure. “It’s not a small number, compared to stoke, risk of myocardial infarction and death,” he said.
Some series have reported up to 40% of patients showed some cognitive dysfunction, and post–carotid endarterectomy cognitive dysfunction has been associated with early death, Dr. Motaganahalli said.
Cognitive dysfunction manifests in various forms, ranging from level of consciousness and memory to mood and ability to make calculations. Although the Mini-Mental State Examination Global Cognitive Assessment tool provides a method for evaluating cognitive function, “There is no uniformly accepted neurocognition test,” Dr. Motaganahalli said. That explains the wide variability of findings among published studies.
Vascular surgeons take a somewhat casual approach to their patients’ cognitive abilities after carotid revascularization, Dr. Motaganahalli said. “We don’t evaluate their memory and their cognitive functions on post-op day one; we just look to see whether they have neurologic dysfunction up front and that they’re capable of going home after that.”
But predicting in advance which patients are predisposed to cognitive decline after the procedures is difficult, he said. He cited a systematic review of 32 studies published between 1990-2007 that showed variable results (Stroke. 2008;39:3116-27): 11 studies during 1990-2005 suggested cognition actually improved after CEA; 9 studies during 1994-2006 suggested the opposite; 4 trials during 1992-2005 suggested no change in cognition after CEA; 5 studies during 2003-2007 showed improvement in cognition after CAS; and 3 trials comparing CAS and CEA and cognition found no differences in how the two procedures affect cognition.
Dr. Motaganahalli also cited a systematic review of 37 studies, 18 of which examined CEA, 12 CAS and seven compared CEA and CAS, found that either cognitive improvement or impairment for CEA and CAS separately were 10–15% of patients (Cerebrovasc Dis Extra. 2014;4:132-48).
“We have 69 papers that looked at cognitive function alone, but unfortunately, we don’t know whether cognitive function really improved based on this data set,” he said. “None of them are making the argument so clearly that there is cognitive improvement after revascularization.”
The variability in study findings can be due to differences in methodologies, the types of psychometric tests used, statistical analyses and the timing of cognitive assessments, Dr. Motaganahalli said.
Cognitive impairment after stroke caused by carotid disease is better understood than is cognitive impairment in the absence of a major stroke, Dr. Motaganahalli said.
“The mechanisms of how carotid disease can cause the cognitive impairment are threefold: It could be microembolism and hypoperfusion, which together can cause white matter disease and thereby some cognitive dysfunction in the long term,” he said (Neuroimaging Clin N Am. 2007 Aug;17:313-24).
Functional neurons may be a biomarker of cognitive outcome, he said. Hypoperfusion of functional neurons may lead to hypofunctional neurons, which can increase cerebral blood flow and cerebral metabolic rate for oxygen (CMRO2), and thus improve cognition. However, when additional variables are introduced to the hypofunctional neurons – such as microembolism, white matter disease, and prolonged hypoperfusion – that can lead to neuronal infarction that, while increasing cerebral blood flow, causes no change in CMRO2 and, thus, no cognitive improvement. The interval between hypofunctional neurons and neuronal infarction “is the time to do the revascularization, as long as you can demonstrate that there may be some truth to matter that it influences cognition,” Dr. Motaganahalli said.
While vascular surgeons may not be able to predict who will have cognitive decline after carotid interventions, “There are some pointers for possibly picking those patients who may benefit,” Dr. Motaganahalli said.
That choice of patients revolves around recognizing that chronic ischemia induces and increases the severity of cognitive dysfunction. Therefore, incorporating the pathophysiology of chronic ischemia into the algorithm for carotid artery disease may provide an opportunity to extend the goals of carotid artery revascularization to include preventing or reversing cognitive decline, he said.
Dr. Motaganahalli disclosed he is a consultant to Silk Road Medical.