Cognitive changes after carotid artery stenting
- 251 Downloads
We aimed to test changes in cognitive performance after carotid artery stenting (CAS).
Ten patients were neuropsychologically tested at least 24 h before and 48 h after CAS. To diminish thromboembolic events, we used a proximal protection device. The following neuropsychological tests were selected: The Mini Mental State Examination (MMSE), symbol digit test and subtests of the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery (verbal fluency, constructional practice, word list memory and delayed recall). Affective state was determined by the Beck Depression Score (BDS).
No patient suffered from depression (BDS <1) or dementia (MMSE 29.9±1.5). Nine of the ten patients (P=0.12) showed increased speed in the Number Connection Test (NCT) (corresponding to trail making test). Most patients showed better or similar results concerning delayed recall (P=0.31). No change was observed in the symbol digit test, word list memory, verbal fluency or constructional practice. Better results concerning NCT and delayed recall after carotid stenting might be due to improved brain perfusion.
After CAS, cognitive and memory performance seem to improve. Further studies with different time intervals and more refined testing, as well as perfusion-weighted imaging, are needed.
KeywordsCarotid Stent Cognitive changes Neuropsychological Diffusion-weighted imaging (DWI)
Stenting of the carotid artery as well as carotid endarterectomy (CEA) are widely used to treat carotid stenosis in symptomatic patients who have suffered a recent carotid territory transient ischemic attack (TIA) or minor complete stroke.
Patients and methods
The university’s Ethics Commission approved the study and all patients gave informed consent. To avoid influencing the test results, exclusion criteria were an upper extremity paresis, eyesight impairment, a hemianopsia or a history of psychiatric disease such as schizophrenia, depression or an organic psychosyndrome. Patients also had to show sufficient command of the language.
Ten right-handed patients with stenosis of the internal carotid artery (ICA) were tested. The mean age of the patients was 63.7 years ranging from 47 to 80 years (three female, seven male). In seven patients, stenosis was on the right side; in three patients, stenosis was on the left side. The mean degree of stenosis determined by angiography was 88%. Neuropsychological testing was conducted at least 24 h before and 48 h after stenting.
The neuropsychological test battery included the Number Connection Test (NCT) which corresponds to the trail making test. This is used for testing cognitive speed. Additionally, subtests of the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery such as verbal fluency, constructional practice, word list memory and delayed recall were tested. To avoid the effect of learning, parallel forms were used. This involved employing the identical procedure to measure a particular aspect of cognitive functioning, but with different items.
In order to determine the affective state, we included the Mini Mental Status Evaluation (MMSE) test to screen for dementia as well as the Beck Depression Score (BDS). All procedures were performed under local anesthesia and percutaneous transfemoral access. Patients were given standard anticoagulation of aspirin (100 mg per day) and clopidogrel (75 mg per day) for at least 3 days prior to the intervention. Low molecular weight heparin (LMWH) was injected subcutaneously prior to the intervention. In addition, patients received intravenous administration of 7000 IU heparin during the procedure. Both aspirin and clopidogrel were given for 6 weeks after the procedure; thereafter, patients remained on aspirin only (100 mg per day).
A proximal protection device was used during stenting. First, a reverse flow Parodi Anti-Embolism System (PAES; ArteriA Medical Science, San Francisco, Calif.) was placed with a 260-cm exchange wire in the external carotid artery and in the common carotid artery 3 cm below the carotid bifurcation. Flow reversal was achieved by inflating the balloons in the external and common carotid arteries. The stent was then placed. All patients tolerated the temporal occlusion of the common carotid artery. Diffusion-weighted imaging (DWI) was performed in all patients before and after stenting.
Statistical analysis was performed in Statistical Package for the Social Sciences (SPSS 12.0) using a non-parametric test (Spearman's rho). The Wilcoxon test was used to compare the results before and after stenting (related samples).
After stenting, there was no statistically significant improvement in motor function or word list memory. Furthermore, there was no apparent correlation between the side treated and the type or degree of improvement.
DWI revealed that no patient suffered from “silent” infarcts before the procedure. After stenting, new lesions were found in four of ten patients. In three patients, the lesions were in the vessel-dependent area. All patients were clinically asymptomatic.
Neuropsychological deficit may not be as apparent to the clinician as neurological deficit; however, it can disrupt an individual’s life. The effect of CEA upon cognitive function has been the subject of many studies, yet remains controversial. A comprehensive report of all studies before 1996 noted that in 16 of 28 studies (57%), the authors concluded that CEA led to improved cognitive test performance, while in 12 of 28 studies (43%) CEA was found either to lead to no beneficial effect (11 studies) or to a deterioration in cognition (1 study) . However, the studies differed on a number of methodological issues such as sample size (6–145), type of patients (demographic, mood and TIA or stroke), control group, the severity and side of the carotid stenosis, the range of cognitive tests used, the type of analysis used, and the time of assessment . The authors concluded that although most of the studies showed an improvement in verbal fluency and memory, it remained to be seen which group of patients benefited from CEA.
Further studies have shown a cognitive benefit of CEA [2, 3, 4]; on the other hand, some have shown no influence of CEA upon cognition [5, 6, 7]. Heyer et al.  examined 112 patients treated with CEA and found that approximately 80% showed a decline in one or more test scores, while 60% showed cognitive improvement at the first follow-up examination. Cognitive improvement in the treated patients was more obvious after 30 days. There are only a few studies in the literature concerning cognitive changes in patients treated with endovascular stent placement in the carotid artery [9, 10]. Moftakhar et al.  reported that 15 of 19 patients showed improved cognitive scores after stent placement.
In our study, neuropsychological improvement was seen after CAS. As we used parallel test forms, the effect of learning could be largely excluded. The cognitive changes that occurred primarily concerned cognitive speed, word fluency and delayed recall. In contrast to other studies , we did not see a change in motor performance. We found a relationship between the age of the patient, the initial score and the degree of improvement in cognitive scores. Older patients were more likely to show a marked cognitive improvement. Also, patients with low scores on the neuropsychological tests before treatment performed markedly better on the same tests after CAS, while patients with high scores before treatment did not show a similar degree of improvement. The cognitive improvement that was observed could have been due to rapid changes in the cerebral blood flow after CAS. A previous study has shown that stenoses of the carotid artery of 75% and 84% in diameter result in 40% and 60% reductions in cerebral blood flow, respectively .
In only a few studies has the degree of neuropsychological improvement after CEA been investigated in relation to alteration in cerebral blood flow [2, 4, 12]. Fearn et al.  reported an improvement with respect to attention in neuropsychological tests in patients with impaired cerebrovascular reserve. Interestingly, we found that the patient who improved most in regard to cognitive speed had a marked perfusion deficit on MRI without adequate autoregulation. Therefore, the better results might have been due to changes in cerebral blood flow. However, this is an observation in one single case, so further studies with perfusion-weighted imaging should be conducted.
In our study, cognitive improvement was obvious immediately after stenting. Protection devices were used to reduce the risk of cerebral microemboli during the procedure. DWI was performed in all patients before and after stenting to detect silent microembolic events that might be associated with cognitive impairment [13, 14]. No patient suffered from “silent” infarcts before the procedure. Therefore, we eliminated the possibility that the observed improvement was due to impaired function recovery from infarcts unrelated to carotid stenting.
Silent microembolic events during the procedure were not completely avoided. DWI revealed lesions in 40% of the treated patients. In three patients, the lesions were in the vessel-dependent area and were determined to be intervention-related. Following carotid angioplasty and stenting using a distal protection device, Gauvrit et al.  found new lesions on DWI in only 2 of 23 patients, one of whom had a new neurological deficit. Flach et al.  used both distal and proximal protection devices during the procedure. They identified new lesions on DWI after stenting in a much higher proportion of treated patients (9 of 21, 43%). Our results are in agreement with those of Flach et al. The significance of clinically silent embolization during carotid artery interventions has not yet been established, and microvascular obstructions are difficult to recognize [17, 18]. One can hypothesize that some lesions detected with DWI might cause neuropsychological changes. Although we detected lesions with DWI, neuropsychological improvement was still obvious. The exact significance of these lesions remains unclear.
Stenting of the ICA may offer more than a reduced risk of stroke, especially to patients with impaired perfusion. Further studies evaluating cerebral blood flow before and after stenting with different time windows and more refined neuropsychological tests are needed.
Conflict of interest statement
We declare that we have no conflict of interest.
- 8.Heyer EJ, Sharma R, Rampersad A, Winfree CJ, Mack WJ, Solomon RA, Todd GJ, McCormick PC, McMurtry JG, Quest DO, Stern Y, Lazar RM, Connolly ES (2002) A controlled prospective study of neuropsychological dysfunction following carotid endarterectomy. Arch Neurol 59(2):217–222PubMedCrossRefGoogle Scholar
- 17.Jacobs A, Neveling M, Horst M, Ghaemi J, Kessler J, Eichstaedt H, Rudolf J, Model P, Bönner H, de Vivie ER, Heiss WD (1998) Alterations of neuropsychological function and cerebral glucose metabolism after cardiac surgery are not related only to intraoperative microembolic events. Stroke 29:660–666PubMedGoogle Scholar