Nathalie Stroobant

Transcranial Doppler Ultrasonography Monitoring of Cerebral Hemodynamics During Performance of Cognitive Tasks: A Review

The examination of blood flow velocity (BFV) changes during the performance of mental tasks is one of the applications of transcranial Doppler (TCD) ultrasonography. The purpose of this review is to summarize the results of the functional TCD literature, to investigate the effects of methodological differences between studies, and to provide guidelines for future research. It is concluded that larger series of more homogeneous groups concerning age and handedness, and stricter criteria for subject selection and laboratory setting are required. The implication of quantitative and qualitative performance measures and psychological parameters (motivation, anxiety, and task anticipation) could also yield important information. We recommend future agreement upon a more standardized methodology. TCD promises to be a useful tool to provide further insight into the cerebral organization and temporal reactivity of the human brain.

Lateralization of Cerebral Blood Flow Velocity Changes During Cognitive Tasks A Simultaneous Bilateral Transcranial Doppler Study

BACKGROUND AND PURPOSE Transcranial Doppler ultrasonography (TCD) permits the assessment of cognitively induced cerebral blood flow velocity (BFV) changes. We sought to investigate the lateralization of BFV acceleration induced by a variety of cognitive tasks and to determine the influence of age, gender, IQ, and quality of the performance on the relative BFV changes. METHODS Simultaneous bilateral TCD monitoring of BFV in the middle cerebral arteries (MCAs) was performed in 90 normal right-handed volunteers during 13 verbal and visuospatial tasks and their preceding rest periods. RESULTS All tasks induced a significant bilateral BFV increase in the MCAs compared with the preceding rest periods. Five verbal tasks showed a significant left-hemispheric BFV acceleration. Linguistic tasks that required active or creative processing of the verbal stimuli, such as sentence construction or word fluency, elicited the most asymmetric response. Five visuospatial tasks revealed a significant right-hemispheric BFV shift. Paradigms that combined visuospatial attention and visuomotor manipulation showed the most lateralized acceleration. Older volunteers (aged >50 years) showed higher relative BFV changes, but lateralization was not influenced by age. Gender, IQ, and performance quality did not reveal significant effects on BFV change. CONCLUSIONS Bilateral TCD is a noninvasive technique that has the potential to connect the particular change in flow pattern of the MCA distribution with selective cognitive activity and thus offers specific functional information of scientific and clinical value.

Depression, Anxiety, and Neuropsychological Performance in Coronary Artery Bypass Graft Patients: A Follow-Up Study

BACKGROUND Undergoing coronary-artery bypass surgery (CABG) remains a significant life-event, with an important psycho-emotional impact on patients and their families. OBJECTIVE The authors examined the incidence and course of depression and anxiety in CABG patients before and after surgery. METHOD The long-term relationship between mood disorders and neuropsychological deficits was studied 1 day before and 6 days (N=53), 6 months (N=37), and 3-5 years (N=43) after the procedure. RESULTS Before surgery, one-third of the patients showed mild-to-moderate cognitive-affective symptoms of depression. After surgery, one-fourth still showed elevated depression scores, whereas anxiety was significantly decreased at all post-operative time-points. Patients with higher pre-operative symptoms of depression showed sustained feelings of depression after surgery. Visuomotor performance was most affected by mood. CONCLUSION Data indicated that patients with preoperative moderate cognitive-affective depression could be at risk for sustained feelings of depression even up to 5 years after surgery.

Short-term and long-term neurocognitive outcome in on-pump versus off-pump CABG.

OBJECTIVE Neuropsychological dysfunctions are considered to be important complications of coronary artery bypass graft surgery (CABG). We examined the frequency of neuropsychological abnormalities occurring in patients undergoing CABG with (on-pump) and without (off-pump) cardiopulmonary bypass. METHODS Neuropsychological assessment with seven cognitive tasks was performed one day before, 6-7 days after (n=49) and 6 months after (n=35) surgery. The subgroup undergoing on-pump surgery (n=30 at 7 days and n=22 at 6 months) was demographically comparable to the off-pump subgroup. The on-pump group included more multiple vessel disease. RESULTS Repeated measures multivariate analysis of variance (using surgical group as a between-subjects factor) on the group data revealed no significant differences neither immediately after surgery nor at 6 months after surgery, compared with the preoperative performance. There were no significant differences between the on-pump and off-pump groups in post-operative neuropsychological performance soon after surgery. A significant difference was found between the two groups 6 months after surgery, with more favorable results for the off-pump group. Individual comparisons revealed that 59% of the patients of both groups undergoing CABG showed evidence of cognitive impairment soon after surgery. In 11% of the patients (all on-pump), the cognitive sequelae persisted at follow-up. CONCLUSION This study showed no short-term difference between the on-pump and off-pump CABG groups. The long-term cognitive outcome revealed more favorable results for the off-pump group. Although a preference to operate multiple vessel disease with classical cardiopulmonary bypass (CPB) has to be considered, the present study shows evidence for a different pattern of early decline and late recovery of cognitive functions in patients undergoing CABG with and without CPB.

Variation in brain lateralization during various language tasks: a functional transcranial Doppler study.

Language dominance has repeatedly been demonstrated by means of functional transcranial Doppler (fTCD) ultrasonography. However, one strongly lateralizing paradigm might be an overestimation of overall language lateralization. We hypothesized that significant differences between hemodynamic patterns could be shown by using multiple language functions (such as productive and receptive tasks). Particularly, we expected more left-hemispheric activity in frontal and productive tasks and we expected less clear left-hemispheric activity in temporal regions and receptive tasks. Thirty healthy volunteers were included in the study. The lateralization index (LI) was measured with transcranial Doppler ultrasonography for each subject during four language tasks: a cued word generation task (WF), a sentence construction task (SENT), a reading task (READ), and a semantic decision task (SEMANT). Left-hemispheric dominance was found in 90%, 80%, 73.3% and 66.7% of the subjects for respectively WF, SENT, READ and SEMANT. A repeated measures analysis of variance revealed significant differences in LIs between the different language tasks (p<.01). Our results showed that productive and syntactic tasks (WF and SENT) lateralize stronger than receptive tasks (READ and SEMANT). The use of a variety of language tasks in the determination of language lateralization therefore appears to be essential in providing a more comprehensive view of language functioning.

Neuropsychological functioning 3—5 years after coronary artery bypass grafting: does the pump make a difference? §

OBJECTIVE Neurocognitive sequelae after coronary artery bypass grafting (CABG) are frequently reported. The present study investigated the possible difference between on- and off-pump CABG patients in a long-term perspective. METHODS We administered seven standardized neuropsychological tests 1 day before, 6 days after, 6 months after and 3-5 years after CABG. We measured intra-operative high intensity transient signals (HITS) as a reflection of embolic load by transcranial Doppler ultrasonography. RESULTS Of the 74 patients originally recruited, 54 of the patients (73%) (mean age 59 years+/-7.5 years) completed the neuropsychological battery. Cognitive decline was defined as 20% decline on two or more tests. Three to 5 years after the operation, 30% of the patients showed neurocognitive problems in domains of non-verbal immediate memory and attention, speed for visual search, visual attention and mental flexibility. Neither difference in frequency of cognitive dysfunction nor a difference in evolution over the 5 year time period between on- and off-pump patients was observed. No significant predictors for cognitive decline were found. CONCLUSIONS Three to 5 years after the CABG surgery no difference in neurocognitive deficits is found between on- and off-pump CABG patients, indicating that the extracorporeal circulation (ECC) may not be the main cause of late neuropsychological decline.

Test-retest reliability of functional transcranial Doppler ultrasonography

The present study evaluates the reproducibility of lateralised blood flow velocity (BFV) changes measured with transcranial Doppler (TCD) ultrasonography during various cognitive paradigms. A total of 20 right-handed volunteers were confronted twice with 13 verbal and visuospatial tasks, with a time interval of 23 to 71 days. No statistically significant differences were found between the lateralisation indices (left BFV change minus right BFV change) on the first and second examinations. Lateralisation indices of eight tasks showed a significant test-retest reliability (r = 0.61 to 0.83). The reproducibility of cognitively induced lateralised BFV changes appears to be task-dependent. The possible influence from technical, physiological, and psychological factors is discussed. We conclude that functional neuroimaging studies based on blood flow data should preferably select cognitive paradigms that demonstrated sufficient test-retest reliability.

Role of patient-specific virtual reality rehearsal in carotid artery stenting

Recent advances in simulation science permit patient‐specific rehearsal of endovascular stenting procedures. This study aimed to evaluate how effectively real interventions are replicated by patient‐specific rehearsal technology, and to assess its value as a preparatory tool for the interventionalist and the operating team.

Between-task habituation in functional transcranial Doppler ultrasonography

We investigated the variability of absolute blood flow velocity (BFV) and task-induced BFV change over consecutive cognitive tasks and compared two methods of baseline determination that are used to calculate relative BFV changes. Bilateral transcranial Doppler ultrasonography recordings of BFV in the middle cerebral arteries was performed in 90 right-handed volunteers during 13 cognitive tasks and their preceding rest periods. Both absolute BFV and elicited BFV changes between rest and activation significantly decreased over successive tasks. Instead of calculating an averaged baseline value, our results suggest that the rest phase immediately preceding the activation phase should be selected for baseline measurement. The between-task habituation effect could be due to a fading of attentional resources during the sustained and demanding performance.

Pre-existing cognitive impairment in candidates for cardiac surgery: an overview

Until now, little attention has been paid to the preoperative status of the patient awaiting cardiac surgery when investigating the effects of cardiac surgery on cognition. However, there is growing evidence that pre-bypass patients show poorer cognitive function than healthy subjects. This article reviews existing published evidence of poor cognitive function in pre-bypass patients by describing patient characteristics, providing an inventory of affected neurocognitive domains, discussing adequate control groups and proposing potential aetiological mechanisms of neuropsychological dysfunctioning. It is concluded that there is a growing need for future research into this important topic on cognitive dysfunctioning in candidates for coronary artery bypass grafting surgery.