Evaluation of cerebral hemodynamic status in patients with unilateral symptomatic carotid artery stenosis during motor tasks, through use of transcranial Doppler sonography

ABSTRACT Background: Carotid artery stenosis increases cerebral ischemic event risk through changing different cerebral hemodynamic parameters. Objective: To investigate how cerebral hemodynamics in the M1 segment of middle cerebral artery change in patients with carotid artery stenosis, after motor tasks using transcranial Doppler sonography (TCD). Methods: Thirty-two healthy subjects and 30 patients with unilateral symptomatic carotid artery stenosis were recruited. The patient population was divided into three groups according to the degree of stenosis (group 1: ≥50 to 69%, group 2: 70 to 89% and group 3: ≥90 to 99%). TCD was used to measure the pulsatility index (PI) and cerebral vasomotor reactivity (CVR). Results: In the patient group, significant differences for symptomatic side PI values (p=0.01) and mean CVR increases (p=0.05) were observed, compared with the healthy controls. However, the difference was not statistically significant for asymptomatic side PI values and mean CVR increases. The results from the intergroup comparison showed significantly higher percentages of symptomatic and asymptomatic side CVR increases in group 1, compared with groups 2 and 3 (p=0.001 and p=0.002, respectively). Conclusions: Our study showed that cerebral autoregulation and hemodynamic mechanisms are impaired in patients with carotid artery stenosis. Furthermore, the impairment of PI and CVR tends to get worse with increasing degrees of stenosis. In addition, this study demonstrated that assessment of these two hemodynamic parameters in clinical practice might be helpful for monitoring the progress of carotid artery stenosis.

Safety and Clinical Effects of Switching From Intravenous to Oral Nimodipine Administration in Aneurysmal Subarachnoid Hemorrhage

Objective: Several guidelines recommend oral administration of nimodipine as vasospasm prophylaxis after aneurysmal subarachnoid hemorrhage (SAH). However, in clinical practice, the drug is administered orally and intravenously (i.v.), depending on clinical conditions and local treatment regimens. We have therefore investigated the safety and clinical effects of switching from i.v. to oral nimodipine therapy.Methods: Patients with aneurysmal SAH between January 2014 and April 2018 and initial i.v. nimodipine therapy, which was subsequently switched to oral administration, were included in this retrospective study. Transcranial Doppler sonography (TCD) of the vessels of the anterior circulation was performed daily. The occurrence of vasospasm and infarction during the overall course of the treatment was recorded. Statistical level of significance was set to p < 0.05.Results: A total of 133 patients (mean age 55.8 years, 65% female) initially received nimodipine i.v. after aneurysmal SAH, which was subsequently switched to oral administration after a mean of 12 days. There were no significant increases in mean flow velocities on TCD after the switch from i.v. to oral nimodipine administration regarding the anterior cerebral artery. For the middle cerebral artery, an increase from 62.36 to 71.78 cm/sec could only be detected in the subgroup of patients with infarction. There was no clustering of complicating events such as new-onset vasospasm or infarction during or after the switch.Conclusions: Our results do not point to any safety concerns when switching nimodipine from initial i.v. to oral administration. Switching was neither associated with clinically relevant increases in TCD velocities nor other relevant adverse events.

Value of Cardiac Cine MRI in Comparison to Contrast Transcranial Doppler Sonography for Patent Foramen Ovale Assessment in Patients with Cerebral Disorders

Purpose: To investigate the clinical feasibility of diagnosing and classifying patent foramen ovale (PFO) in patients with cerebral disorders by cardiac cine MRI (CCMRI) without contrast.Materials and Methods: Forty-four patients (24 males and 20 females; mean age, 41.3 years; range, 21–64 years) with cerebral disorders underwent contrast transcranial Doppler sonography (cTCD) and non-enhanced CCMRI examinations between October 2019 and March 2020. CCMRI was performed with a 3.0T magnetic resonance (MR) scanner using the OBL FIESTA CINE 4CH sequence. The scanning direction was perpendicular to the interatrial septum (IAS). The obtained MR images were analyzed by AW station 4.4. Pseudo-color coding was performed based on the different phases. The blood shunt condition was observed and recorded, noting the PFO length and width and whether it was complicated by IAS aneurysm or secondary septum thickening.Results: Thirty-nine of the 44 patients with cerebral disorders were confirmed to have right-to-left shunt by cTCD, and 37 of them were diagnosed with PFO by CCMRI. Two of the five remaining patients were also diagnosed with PFO by CCMRI. Compared with cTCD as a standard, CCMRI assessment resulted in the following: sensitivity, 94.9%; specificity, 60.0%; accuracy, 90.9%; positive predictive value, 94.9%; negative predictive value, 60.0%; area under the curve, 0.774. Using pseudo-color coding, a right-to-left color jet was observed in 34 patients, and a two-way shunt was found in five. IAS aneurysm and secondary septum thickening were found in five and three patients (11.4% and 6.8%), respectively. The maximum PFO diameters ranged from 1.7 to 16.8 mm, and the mean diameter was 5.4 ± 3.4 mm.Conclusion: The noninvasive CCMRI without contrast proved an excellent method for PFO identification, evaluation, and classification, with high sensibility (92.85%) and concordance (90.9%) compared to cTCD.

Effects of GV14 Acupuncture on Cerebral Blood Flow Velocity in the Basilar and Middle Cerebral Arteries and CO2 Reactivity during Hypercapnia in Normal Individuals

The Governing Vessel 14 (GV14) (Dazhui) is one of the acupuncture points referred to as “seven acupoints for stroke.” Nevertheless, there is a scarcity of research on the effects of acupuncture treatment at GV14. This study investigated the effects of acupuncture at GV14 on cerebral blood flow (CBF), especially that in the basilar artery (BA) and the middle cerebral arteries (MCA). Sixteen healthy men aged 20 to 29 years were enrolled in this study. CBF velocity and cerebrovascular reactivity (CVR) were measured using transcranial Doppler sonography (TCD). The following were assessed: closed circuit rebreathing- (CCR-) induced carbon dioxide (CO2) reactivity, modified blood flow velocity at 40 mmHg (CV40) on BA and MCAs, blood pressure (BP), and heart rate (HR). Observed results were obtained after comparison with the baseline evaluation. Statistically significant elevations in CO2 reactivity were recorded in the BA (3.28 to 4.70, p < 0.001 ) and MCAs (right: 3.81 to 5.25, p = 0.001 ; left: 3.84 to 5.12, p = 0.005 ) after acupuncture at GV14. The CV40 increased statistically significantly only in the BA (45.49 to 50.41, p = 0.003 ). No change was observed in BP (106.83 to 107.08 (mmHg), p = 0.335 ) and HR (77 to 75 (bpm), p = 0.431 ). Acupuncture at GV14 improved CBF velocity. These results could be explained by the regulation of endothelium-dependent vessel dilation effected by acupuncture. This trial is registered with Korean Clinical Trial Registry (http://cris.nih.go.kr; registration number: KCT0004787).

Cerebral lateralisation of first and second languages in bilinguals assessed using functional transcranial Doppler ultrasound

Background: Lateralised language processing is a well-established finding in monolinguals. In bilinguals, studies using fMRI have typically found substantial regional overlap between the two languages, though results may be influenced by factors such as proficiency, age of acquisition and exposure to the second language. Few studies have focused specifically on individual differences in brain lateralisation, and those that have suggested reduced lateralisation may characterise representation of the second language (L2) in some bilingual individuals. Methods: In Study 1, we used functional transcranial Doppler sonography (FTCD) to measure cerebral lateralisation in both languages in high proficiency bilinguals who varied in age of acquisition (AoA) of L2. They had German (N = 14) or French (N = 10) as their first language (L1) and English as their second language. FTCD was used to measure task-dependent blood flow velocity changes in the left and right middle cerebral arteries during phonological word generation cued by single letters. Language history measures and handedness were assessed through self-report. Study 2 followed a similar format with 25 Japanese (L1) /English (L2) bilinguals, with proficiency in their second language ranging from basic to advanced, using phonological and semantic word generation tasks with overt speech production. Results: In Study 1, participants were significantly left lateralised for both L1 and L2, with a high correlation (r = .70) in the size of laterality indices for L1 and L2. In Study 2, again there was good agreement between LIs for the two languages (r = .77 for both word generation tasks). There was no evidence in either study of an effect of age of acquisition, though the sample sizes were too small to detect any but large effects. Conclusion: In proficient bilinguals, there is strong concordance for cerebral lateralisation of first and second language as assessed by a verbal fluency task.

Extended neuromonitoring in aortic arch surgery

Background Aortic arch repair for aortic dissection is still associated with a high mortality rate. Providing adequate means of neuromonitoring to guide cerebral hemodynamics is advantageous, especially during selective anterior cerebral perfusion (SACP). Objective We aimed to investigate an easy multimodal neuromonitoring set-up consisting of processed electroencephalography (EEG), near infrared spectroscopy (NIRS), and transcranial doppler sonography (TCD). Material and methods We collected intraoperative data from six patients undergoing surgery for aortic dissection. In addition to standard hemodynamic monitoring, patients underwent continuous bilateral NIRS, processed EEG with bispectral index (BIS), and intermittent transcranial doppler sonography of the medial cerebral artery (MCA) with a standard B‑mode ultrasound device. Doppler measurements were taken bilaterally before cardiopulmonary bypass (CPB), during CPB, and during SACP at regular intervals. Results Of the patients four survived without neurological deficits while two suffered fatal outcomes. Of the survivors two suffered from transient postoperative delirium. Multimodal monitoring led to a change in CPB flow or cannula repositioning in three patients. Left-sided mean flow velocities of the MCA decreased during SACP, as did BIS values. Conclusion Monitoring consisting of BIS, NIRS, and TCD may have an impact on hemodynamic management in aortic arch operations.

Increased cognitive workload evokes greater neurovascular coupling responses in healthy young adults

Understanding how the brain allocates resources to match the demands of active neurons under physiological conditions is critically important. Increased metabolic demands of active brain regions are matched with hemodynamic responses known as neurovascular coupling (NVC). Several methods that allow noninvasive assessment of brain activity in humans detect NVC and early detection of NVC impairment may serve as an early marker of cognitive impairment. Therefore, non-invasive NVC assessments may serve as a valuable tool to detect early signs of cognitive impairment and dementia. Working memory tasks are routinely employed in the evaluation of cognitive task-evoked NVC responses. However, recent attempts that utilized functional near-infrared spectroscopy (fNIRS) or transcranial Doppler sonography (TCD) while using a similar working memory paradigm did not provide convincing evidence for the correlation of the hemodynamic variables measured by these two methods. In the current study, we aimed to compare fNIRS and TCD in their performance of differentiating NVC responses evoked by different levels of working memory workload during the same working memory task used as cognitive stimulation. Fourteen healthy young individuals were recruited for this study and performed an n-back cognitive test during TCD and fNIRS monitoring. During TCD monitoring, the middle cerebral artery (MCA) flow was bilaterally increased during the task associated with greater cognitive effort. fNIRS also detected significantly increased activation during a more challenging task in the left dorsolateral prefrontal cortex (DLPFC), and in addition, widespread activation of the medial prefrontal cortex (mPFC) was also revealed. Robust changes in prefrontal cortex hemodynamics may explain the profound change in MCA blood flow during the same cognitive task. Overall, our data support our hypothesis that both TCD and fNIRS methods can discriminate NVC evoked by higher demand tasks compared to baseline or lower demand tasks.