Assessment of ophthalmic artery collateral pathway in the hemispheric cerebral hemodynamics in patients with severe unilateral carotid stenosis

ASNM and ASN joint guidelines for transcranial Doppler ultrasonic monitoring: An update

Today, it seems prudent to reconsider how ultrasound technology can be used for providing intraoperative neurophysiologic monitoring that will result in better patient outcomes and decreased length and cost of hospitalization. An extensive and rapidly growing literature suggests that the essential hemodynamic information provided by transcranial Doppler (TCD) ultrasonography neuromonitoring (TCDNM) would provide effective monitoring modality for improving outcomes after different types of vascular, neurosurgical, orthopedic, cardiovascular, and cardiothoracic surgeries and some endovascular interventional or diagnostic procedures, like cardiac catheterization or cerebral angiography. Understanding, avoiding, and preventing peri- or postoperative complications, including neurological deficits following abovementioned surgeries, endovascular intervention, or diagnostic procedures, represents an area of great public and economic benefit for society, especially considering the aging population. The American Society of Neurophysiologic Monitoring and American Society of Neuroimaging Guidelines Committees formed a joint task force and developed updated guidelines to assist in the use of TCDNM in the surgical and intensive care settings. Specifically, these guidelines define (1) the objectives of TCD monitoring; (2) the responsibilities and behaviors of the neurosonographer during monitoring; (3) instrumentation and acquisition parameters; (4) safety considerations; (5) contemporary rationale for TCDNM; (6) TCDNM perspectives; and (7) major recommendations.

Influence of collateral circulation on cerebral blood flow and frontal lobe cognitive function in patients with severe internal carotid artery stenosis

BACKGROUND

This study aimed to investigate the cerebral blood flow (CBF) and frontal lobe cognitive function in severe internal carotid artery (ICA) stenosis patients with different types of collateral circulation.

METHODS

One hundred twenty-six patients with severe unilateral ICA stenosis were enrolled. Digital subtraction angiography (DSA) was performed to recruit patients with one of three common types of collateral circulation: anterior communicating artery (AcoA), posterior communicating artery (PcoA) and ophthalmic artery (OA). The hemodynamic parameters of the middle cerebral artery (MCA) were measured using transcranial Doppler (TCD), and the individual frontal lobe cognitive attention functions were evaluated using Word Fluency Test, Trail-Making Test (TMT), Digit Span, and Stroop Color Word Test (SCWT). The correlation between hemodynamic changes and the scores of all tasks was analyzed.

RESULTS

On the side of arterial stenosis, the CBF velocities were highest in AcoA group and lowest in the OA group. All patients performed worse in TMT and Digit Span than the matched normal controls. The AcoA group exhibited a lower pulsatility index (PI) and a longer response time in the Stroop task, but had a higher accuracy rate in the Stroop task and higher scores in Word Fluency Test than the PcoA and OA groups. In all the three groups, PI was positively correlated with the accuracy rate for Stroop interference effects.

CONCLUSIONS

Our findings suggested that the frontal lobe cognitive function of patients with ICA was impaired, and AcoA collaterals may be beneficial for selective attention functions, whereas OA collaterals may be associated with impairment of selective attention functions. Additionally, a high PI may be an indicator for identifying impaired selective attention in patients with severe ICA stenosis.

Leptomeningeal Collaterals Strongly Correlate with Reduced Cerebrovascular Reactivity Measured by Acetazolamide-challenged Single-photon Emission Computed Tomography Using a Stereotactic Extraction Estimation Analysis in Patients with Unilateral Internal Carotid Artery Stenosis

Objective To assess the correlation between the angiographic appearance of cerebral collateral pathways or the degree of internal carotid artery stenosis (ICAS) and reduced cerebrovascular reactivity (CVR) estimated by single-photon emission computed tomography (SPECT) image analysis in patients with unilateral ICAS. Methods A retrospective analysis was performed in 42 patients with unilateral ICAS who underwent cerebral angiography and acetazolamide-challenged SPECT of the brain. Cerebral blood flow quantitation was performed using the quantitative SPECT/dual-table autoradiography method. The CVR in the middle cerebral artery (MCA) territory was evaluated using the stereotactic extraction estimation based on the Japanese extracranial-intracranial bypass trial (SEE-JET) program and classified as reduced (<18.4%) or non-reduced (≥18.4%). Angiographic collateralization was classified as circle of Willis (type 1), extracranial-intracranial (type 2), and leptomeningeal (type 3). The degree of ICAS was defined as severe (≥70% stenosis) or non-severe (<70%). Results Eight patients showed reduced CVR, including 6 (46%) of 13 with type 3 collaterals and 2 (7%) of 29 without type 3 collaterals (p=0.006). In contrast, type 1 and type 2 collaterals and severe ICAS were not significantly associated with reduced CVR. Conclusion In patients with unilateral ICAS, leptomeningeal collaterals are strongly correlated with reduced CVR in the MCA territory, which presumably increases the risk of cerebral hyperperfusion after carotid artery stenting (CAS). Therefore, these findings may be clinically applicable to the perioperative management of CAS.

Usefulness of transcranial Doppler ultrasound in evaluating cervical-cranial collateral circulations

Transcranial Doppler (TCD) ultrasound is a noninvasive, safe and cost-effective bedside test for evaluating cerebrovascular circulation in real time. It has been rapidly evolving from a simple noninvasive diagnostic tool to an imaging model with a broad spectrum of clinical applications. TCD can show the spectral flow waveforms, blood flow direction, velocities and intensity in the intracerebral vessels, adding physiologic information to other imaging models. TCD can also detect collateral channels through the anterior communicating artery, posterior communicating arteries, reversed ophthalmic artery, leptomeningeal collaterals, reversed basilar artery and reversed vertebral artery caused by hemodynamically significant carotid or intracranial stenosis. This article gives a brief overview of its use in evaluation of collateral circulation in carotid and intracranial steno-occlusive disease.