CHICAGO — Carotid artery stenting appeared to improve cognitive function based on the results of what investigators said is the first study to look at perfusion and diffusion-weighted imaging before and after stenting.
“We found that stenting of the carotid artery significantly increased cognitive speed,” Dr. Iris Grunwald said at the Radiological Society of North America annual meeting. Studies of brain function following carotid endarterectomy have produced mixed results, and there is no consensus in the literature as to whether carotid intervention improves cognition.
Dr. Grunwald and her colleagues at the Saarland University Clinic in Homburg, performed carotid artery stenting on 29 patients. Mean age was 68 years and mean degree of stenosis was 90%. People were excluded from the study if they had paresis in the upper extremity, impairment in eyesight, and/or hemianopsia. Those with psychiatric disease or insufficient command of language also were excluded.
Stents were placed in the left carotid in 18 patients. All of the patients were asymptomatic and right handed. Therefore, speech-related functions were primarily left-brain functions in these patients, she explained.
Perfusion and diffusion-weighted magnetic resonance imaging was performed 24 hours before and 48 hours after intervention (see images). All patients were tested using the Mini-Mental State Examination (MMSE) and symbol digit test and subtests of the CERAD battery. Cognitive speed was assessed with the modified trail making test (ZVT) and the Stroop colored word test.
Findings from the Beck Depression Inventory showed that none of the patients suffered from depression. Mean improvements in cognitive speed ranged from 3% on the ZVT number connection test to almost 7% on the Stroop colored word test.
“Stenting of the internal carotid artery seems to improve functions that involve cognitive speed, regardless of the patient's age, the side of stenosis, or the degree of stenosis,” Dr. Grunwald said. “Some patients showed [more] improvement after stent placement than others. The higher the degree of stenosis, the more marked was the perfusion deficit.
Post-stenting perfusion increased in 17 of the 18 patients, though in 9 of them the increase was described as “slight.” Increased brain perfusion correlated with increased memory function but did not quite reach statistical significance.
“Perfusion of the brain may be what improves cognitive function,” Dr. Grunwald said in an interview. “If that's the case, other means may be taken to improve blood flow. For example, we are also doing studies with sildenafil, which can also improve blood perfusion in the brain and, it appears, improve cognitive functioning afterwards. Further studies with different time intervals and more refined testing are needed to confirm our findings.”
Perfusion and diffusion-weighted MRIs show impaired cerebral blood flow (red) in a carotid stenosis patient.
Carotid stent placement in the same patient restored cerebral blood flow to closer-to-normal (green) levels. Photos courtesy Dr. Iris Grunwald