Cerebral hyperemia after arteriovenous malformation resection is related to "breakthrough" complications but not to feeding artery pressure. The Columbia University Arteriovenous Malformation Study Project

Controlled arterial hypotension during resection of cerebral arteriovenous malformations

Background

Resection of cerebral arteriovenous malformations (AVM) is technically demanding because of size, eloquent location or diffuse nidus. Controlled arterial hypotension (CAH) could facilitate haemostasis. We performed a study to characterize the duration and degree of CAH and to investigate its association with blood loss and outcome.

Methods

We retrospectively analysed intraoperative arterial blood pressure of 56 patients that underwent AVM-resection performed by the same neurosurgeon between 2003 and 2012. Degree of CAH, AVM size, grading and neurological outcome were studied. Patients were divided into two groups, depending on whether CAH was performed (hypotension group) or not (control group).

Results

The hypotension group consisted of 28 patients, which presented with riskier to treat AVMs and a higher Spetzler-Martin grading. CAH was achieved by application of urapidil, increasing anaesthetic depth or a combination thereof. Systolic and mean arterial blood pressure were lowered to 82 ± 7 and 57 ± 7 mmHg, respectively, for a median duration of 58 min [25% percentile: 26 min.; 75% percentile: 107 min]. In the hypotension group, duration of surgery (4.4 ± 1.3 h) was significantly (p <  0.001) longer, and median blood loss (500 ml) was significantly (p = 0.002) higher than in the control group (3.3 ± 0.9 h and 200 ml, respectively). No case fatalities occurred. CAH was associated with a higher amount of postoperative neurological deficits.

Conclusions

Whether CAH caused neurological deficits or prevented worse outcomes could be clarified by a prospective randomised study, which is regarded as ethically problematic in the context of bleeding. CAH should only be used after strict indication and should be applied as mild and short as possible.

Chinese Cerebrovascular Neurosurgery Society and Chinese Interventional & Hybrid Operation Society, of Chinese Stroke Association Clinical Practice Guidelines for Management of Brain Arteriovenous Malformations in Eloquent Areas

Aim: The aim of this guideline is to present current and comprehensive recommendations for the management of brain arteriovenous malformations (bAVMs) located in eloquent areas. Methods: An extended literature search on MEDLINE was performed between Jan 1970 and May 2020. Eloquence-related literature was further screened and interpreted in different subcategories of this guideline. The writing group discussed narrative text and recommendations through group meetings and online video conferences. Recommendations followed the Applying Classification of Recommendations and Level of Evidence proposed by the American Heart Association/American Stroke Association. Prerelease review of the draft guideline was performed by four expert peer reviewers and by the members of Chinese Stroke Association. Results: In total, 809 out of 2,493 publications were identified to be related to eloquent structure or neurological functions of bAVMs. Three-hundred and forty-one publications were comprehensively interpreted and cited by this guideline. Evidence-based guidelines were presented for the clinical evaluation and treatment of bAVMs with eloquence involved. Topics focused on neuroanatomy of activated eloquent structure, functional neuroimaging, neurological assessment, indication, and recommendations of different therapeutic managements. Fifty-nine recommendations were summarized, including 20 in Class I, 30 in Class IIa, 9 in Class IIb, and 2 in Class III. Conclusions: The management of eloquent bAVMs remains challenging. With the evolutionary understanding of eloquent areas, the guideline highlights the assessment of eloquent bAVMs, and a strategy for decision-making in the management of eloquent bAVMs.

Neuroprotective effect of indomethacin in normal perfusion pressure breakthrough phenomenon

Loss of cerebral autoregulation in normal perfusion pressure breakthrough (NPPB) phenomenon has been reported in other Central Nervous System diseases such as neonatal intraventricular haemorrhage. Several studies have demonstrated that low-dose indomethacin prevents this latter condition. A previous rat model was used to resemble NPPB phenomenon. Study animals were distributed in 4 groups that received 3 doses of indomethacin at different concentrations prior to fistula occlusion 60 days after its creation. Control animals received saline solution. Intracranial pressure (ICP) increased in all groups following fistula creation, whereas mean arterial pressure (MAP) and cerebral perfusion pressure (CPP) decreased as a manifestation of cerebral hypoperfusion and intracranial hypertension. The administration of indomethacin was associated with raised MAP and CPP, as well as decreased ICP. Sodium fluorescein extravasation was slight in study animals when comparing with control ones. Histological analysis evidenced diffuse ischaemic changes with signs of neuronal apoptosis in all brain layers in control animals. These findings were only focal and slight in study animals. The results suggest the usefulness of indomethacin to revert, at least partially, the haemodynamic effects of NPPB phenomenon in this experimental model, as well as to reduce BBB disruption and histological ischemia observed in absence of indomethacin.

Ascertaining the Value of Noninvasive Measures Obtained Using Color Duplex Ultrasound and Central Aortic Pressure Monitoring During the Management of Cerebral Arteriovenous Malformation Resection: Protocol for a Prospective, Case Control Pilot Study

BACKGROUND

Dramatic hemodynamic changes occur upon removal of an arteriovenous malformation of the brain (bAVM) with a number of potentially serious perioperative complications, such as intracranial hemorrhage and venous occlusive hypertensive syndrome. As these complications largely occur in the postoperative inpatient period, a rapid, repeatable noninvasive investigation to serially monitor relevant intracranial hemodynamics may be of benefit. Though, transcranial Doppler (TCD) and transcranial color duplex (TCCD) are techniques used and available to provide hemodynamic measurements postoperatively, the time course of hemodynamic sequences following bAVM resection remains uncertain.

OBJECTIVE

This is a prospective, case control pilot study conducted in participants having elective bAVM resection surgery.

METHODS

Each participant will undergo a preoperative color duplex ultrasound (CDU) of the bilateral extracranial carotid arteries, a CDU of the circle of Willis including the bAVM vessels, and a central aortic pressure measurement, repeated daily, postoperatively, for a 2-week period.

RESULTS

Patient accrual has commenced with anticipation of first results in 2018.

CONCLUSIONS

This protocol aims to strengthen the work of previous authors by providing documentation of the time course of hemodynamic changes following bAVM resection. The protocol is designed to determine whether noninvasive technology, including CDU imaging of the extracranial carotid and intracranial arteries in the form of TCCD along with central aortic pressure measurements, can determine whether there are any hemodynamically significant prognostic markers that may provide insight into the process of vessel remodeling, including insight into venous changes following bAVM resection.

Management of unbled brain arteriovenous malformation study

In a recent trial limited to arteriovenous malformations discovered not to have bled, medical management was superior to medical management plus intervention. The trial was halted after 226 randomizations and a mean follow-up of 3.3 years owing to a disparity favoring the medical arm. Eligible patients were selected as suitable for lesion eradication. The initial sample size of 800 and follow-up plans for a mean of 7 years were lowered and shortened, respectively, by the outcome data. An application for extended follow-up was given poor priority scores owing to estimations that the disparities in outcomes would not change significantly.

Normal perfusion pressure breakthrough theory: a reappraisal after 35 years

The intrinsic ability of the brain to maintain constant cerebral blood flow (CBF) is known as cerebral pressure autoregulation. This ability protects the brain against cerebral ischemia and hyperemia within a certain range of blood pressures. The normal perfusion pressure breakthrough (NPPB) theory described by Spetzler in 1978 was adopted to explain the edema and hemorrhage that sometimes occur after resection of brain arteriovenous malformations (AVMs). The underlying pathophysiology of edema and hemorrhage after AVM resection still remains controversial. Over the last three decades, advances in neuroimaging, CBF, and cerebral perfusion pressure (CPP) measurement have both favored and contradicted the NBBP theory. At the same time, other theories have been proposed, including the occlusive hyperemia theory. We believe that both theories are related and complementary and that they both explain changes in hemodynamics after AVM resection. The purpose of this work is to review the current status of the NBBP theory 35 years after its original description.

Revisiting normal perfusion pressure breakthrough in light of hemorrhage-induced vasospasm

Cerebral arteriovenous malformations (AVMs) have abnormally enlarged arteries and veins prone to spontaneous hemorrhage. Immediately following surgical excision of a cerebral AVM, even normal brain tissue surrounding the lesion is subject to hemorrhage, a phenomenon termed normal perfusion pressure breakthrough (NPPB) syndrome. According to this theory, arteries supplying cerebral AVMs become dilated and lose their capacity to dilate or constrict to autoregulate pressure. Acutely after removal of a cerebral AVM, excessive blood pressure in these arterial feeders can cause normal brain tissue to bleed. However, this theory remains controversial. We present a patient with a cerebral AVM that demonstrated cerebrovascular reactivity and argues against an assumption underlying the theory of NPPB syndrome.

Genetic considerations relevant to intracranial hemorrhage and brain arteriovenous malformations

Brain arteriovenous malformations (AVMs) cause intracranial hemorrhage (ICH), especially in young adults. Molecular characterization of lesional tissue provides evidence for involvement of both angiogenic and inflammatory pathways, but the pathogenesis remains obscure and medical therapy is lacking. Abnormal expression patterns have been observed for proteins related to angiogenesis (e.g., vascular endothelial growth factor, angiopoietin-2, matrix metalloproteinase-9), and inflammation (e.g., interleukin-6 [IL-6] and myeloperoxidase). Macrophage and neutrophil invasion have also been observed in the absence of prior ICH. Candidate gene association studies have identified a number of germline variants associated with clinical ICH course and AVM susceptibility. A single nucleotide polymorphism (SNP) in activin receptor-like kinase-1 (ALK-1) is associated with AVM susceptibility, and SNPs in IL-6, tumor necrosis factor-alpha (TNF-alpha), and apolipoprotein-E (APOE) are associated with AVM rupture. These observations suggest that even without a complete understanding of the determinants of AVM development, the recent discoveries of downstream derangements in vascular function and integrity may offer potential targets for therapy development. Further, biomarkers can now be established for assessing ICH risk. These data will generate hypotheses that can be tested mechanistically in model systems, including surrogate phenotypes, such as vascular dysplasia and/or models recapitulating the clinical syndrome of recurrent spontaneous ICH.

Arterial spin-labeling in routine clinical practice, part 3: hyperperfusion patterns

Arterial spin-labeled (ASL) perfusion imaging can be implemented successfully into a routine clinical neuroimaging protocol and can accurately demonstrate alterations in brain perfusion. We have observed patterns of focal, regional, and global hyperperfusion in a wide variety of disease processes. The causes of hyperperfusion at clinical ASL have not been previously characterized. Focal lesions such as brain tumors and vascular malformations with increased perfusion can be well depicted by ASL. More global causes of hyperperfusion, including postanoxia vasodilation and hypercapnia, may go undetected on conventional MR images, whereas the regional hyperperfusion, which may occur in reversible encephalopathies and luxury perfusion, has been consistently illustrated on ASL cerebral blood flow maps at our institution.

Characterization of the cerebral blood flow response to balloon deflation after temporary internal carotid artery test occlusion

The authors tested the hypothesis that cerebral blood flow (CBF) would increase after acute and relatively brief internal carotid artery (ICA) test occlusion, and examined the relationship of the postdeflation CBF to the development of neurologic symptoms. In 16 patients undergoing ICA test occlusion with deliberate hypotension, the authors measured intracarotid 133Xe CBF at baseline, occlusion, and deflation. Four patients developed neurologic symptoms during occlusion. As positive controls, 11 other patients received intracarotid verapamil or papaverine before deflation as part of another protocol. Balloon occlusion was 23.1 +/- 10.5 minutes (mean +/- standard deviation) in duration. At 1.3 +/- 1.6 minutes after balloon deflation, there was a trend (12 +/- 31%) for CBF to increase (48 +/- 9 mL/100 g/min versus 53 +/- 17 mL/100 g/min, P =.15), and a 16 +/- 27% decrease in cerebrovascular resistance (CVR; 2.1 +/- 0.6 mm Hg/100 g/min/mL versus 1.7 +/- 0.6 mm Hg/100 g/min/mL, P =.03) compared with baseline values. By comparison, patients who received a intracarotid dilator demonstrated a 53 +/- 55% increase in CBF (48 +/- 10 mL/100/min versus 70 +/- 23 mL/100 g/min, P = .007) and a 33 +/- 31% decrease in CVR (2.2 +/- 0.6 mm Hg/100 g/min/mL versus 1.4 +/- 0.6 mm Hg/100 g/min/mL, P = .0007) compared with baseline. Analysis of variance and regression analysis showed no other relationships between postocclusion CBF and balloon occlusion duration, distal internal carotid occlusion ("stump") pressure, or the development of neurologic symptoms. Acute, temporary interruption of ICA blood flow resulted in minimal postocclusive changes in cerebrovascular hemodynamics, even in those patients who developed neurologic symptoms during the period of test occlusion.

Anaesthesia for interventional neuroradiology

Neuroradiologists have extended their treatment modalities in the field of vascular neurosurgery. The rapidly emerging and re-engineered neuroradiological techniques confront the anaesthetist with an increasing number of patients with severe neurological disease. More of these patients will need general anaesthesia in order to facilitate the endovascular procedure, including catheter placement, deposition of embolic material, and improved imaging. Anaesthetists are challenged by additional anaesthesiological aspects previously not encountered in neuroanaesthesia. A safe anaesthetic management is based on a broad understanding of pathophysiological and technical issues that arise with the endovascular treatment of cerebral vasculopathy.