"Dirty coagulation" technique as an alternative to microclips for control of bleeding from deep feeders during brain arteriovenous malformation surgery

The Nightmare of AVM Surgery: Early Rupture of the Venous Drainage-Lessons from Personal Experience and a Review of the Literature

We describe the case of a 72-year-old man who presented with signs of increased intracranial pressure, right-sided motor deficit, and repeated episodes of epilepsy due to a left frontal arteriovenous malformation (AVM) with a large superficial draining vein. Despite great efforts to protect the vein from the start, it ruptured shortly after we removed the bone flap. This required rigorous hemorrhage control, which in turn led to profuse bleeding from the nidus throughout the process of the dissection and coagulation of the arterial feeders. The postoperative course was initially uneventful; however, the patient declined neurologically and became unresponsive on the second day after surgery. Emergent CT revealed a significant hematoma occupying the space where the AVM nidus had been resected. The patient was taken back to the OR for emergency evacuation of the hematoma. Despite these efforts, the neurological status remained poor, and the patient was transferred to a territorial hospital after spending 3 weeks in the ICU.An early rupture of the venous drainage represents a dreaded complication of AVM surgery, which can compromise the intervention before the start of the definite resection. We discuss our experience of and strategy for preventing and managing the intraoperative venous rupture of AVMs by describing our seven rules of "Don't." We also provide a brief overview of the relevant literature.

Can angiogenesis be reliably determined on digital subtraction angiography in cerebral arteriovenous malformations?

BACKGROUND

Angiogenesis and nascent blood vessel formation is thought to be important in cerebral arteriovenous malformation (cAVM) development and maintenance, of which little is known. Digital subtraction angiogram (DSA) features of angiogenesis in cAVMs are poorly described and the aim of this study was to describe the frequency of angiogenesis in patients who had a DSA showing a cAVM. We also sought to evaluate the intra- and inter-observer agreement of a diagnosis of angiogenesis and explore which angioarchitectural features were associated with angiogenesis.

METHOD

Patients that underwent a DSA were identified from the database of referred cAVM patients at the Manchester Centre for Clinical Neurosciences. Data were collected from 100 patients (102 cAVMs). cAVM angioarchitecture, including the presence of angiogenesis, was described after reviewing cAVM patient angiograms. The association of angioarchitectural features with angiogenesis was determined using univariate analysis. Ten cases were distributed amongst two other observers for reporting (inter-observer agreement). Twenty cases (including the previous 10) were reported twice by the first author, after a six-month interval (intra-observer agreement).

RESULTS

Angiogenesis was observed in 39 cAVMs (38.2%), with 12 having a complete border (11.8%). Most intra-observer agreement was strong (ranging from κ = 1 to 0.2), but inter-observer agreement was moderate (κ = 1 to -0.316). There was a significant association between angiogenesis and venous reflux (OR 2.52 [95% CI = 1.08-5.88]), venous congestion (OR 4.47 [95% CI = .671-2.52]), arterial ectasia (OR 16.6 [95% CI = 4.65-59.6]), and artery: vein ratio (4.28 [95% CI = .956-19.15]).

CONCLUSION

We have demonstrated perinidal angiogenesis can be visualised on angiograms with moderate reliability, and that it may be related to angioarchitectural characteristics associated with venous hypertension.

A new model of electrosurgical tissue damage for neurosurgery simulation

BACKGROUND

Bipolar hemostasis electrocoagulation is a fundamental procedure in neurosurgery. A precise electrocoagulation model is essential to enable realistic visual feedback in virtual neurosurgical simulation. However, existing models lack an accurate description of the heat damage and irreversible tissue deformation caused by electrocoagulation, thus diminishing the visual realism. This work focuses on the electrocoagulation model for neurosurgery simulation.

METHOD

In this paper, a position-based dynamics (PBD) model with a bioheat transfer and damage prediction (BHTDP) method is developed for simulating the deformation of brain tissue caused by electrocoagulation. The presented BTHDP method uses the Arrhenius equation to predict thermal damage of brain tissue. A deformation model with energy and thermal damage constraints is developed to characterize soft tissue deformation during heat absorption before and after thermal injury. Visual effect of damaged brain tissue is re-rendered.

RESULT

To evaluate the accuracy of the proposed method, numerical simulations were conducted and compared with commercial finite element software. The maximum normalized error of the proposed model for predicting midpoint temperature is 10.3 % and the maximum error for predicting the thermal damage is 5.4 %. The contraction effects of heat-exposed anisotropic tissues are also simulated. The results indicate that the presented electrocoagulation model provides stable and realistic visual effects, making it applicable for simulating the electrocoagulation process in virtual neurosurgery.

Principles and strategies for step-by-step AVM excision

Arteriovenous malformations (AVMs) are some of the most challenging surgical entities. Like any challenging surgical procedure, AVM surgery is a series of basic but fundamental steps, each with its own nuances. Despite a myriad of published material regarding AVMs, there are few succinct illustrated summaries of these steps with an accompanying elucidation of the most common pitfalls. This paper provides a step-by-step description and illustration of the basic surgical principles of AVM microsurgical resection, focusing on the main key points and addressing the critical issues that surround this surgery. Deep anatomical knowledge and presurgical planning of these basic steps, combined with good contingency management skills, are paramount for an effective and safe AVM surgery.

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.

Complications in AVM Surgery

In AVM surgery perioperative complications can arise and can have serious perioperative consequences. Surgically related complications in AVM treatment, in many cases, can be avoided by paying attention to details:1. Careful selection of the patient: - addressing a patient with eloquent AVM to Gamma Knife treatment - preoperative treatment with selective embolization of the accessible deep feeders - preoperative gamma knife or embolize those patient with an over-expressed venous pattern2. Meticulous coagulation of deep medullary feeders: - Using dirty coagulation - Using dry non-stick coagulation - Using micro clips - Using laser - Reaching the choroidal vessel in the ventricle when possible - Avoiding occlusive coagulation with hemostatic agents3. Check and avoiding any residual of the AVM4. Keep the patient under pressure control during postoperative periodFulfilling these steps contributes to reduce complications in this difficult surgery, leading to a safer treatment that compares favorably with natural history of brain arteriovenous malformations.

S-shaped distal access catheter supported microcatheter navigation into the lenticulostriate artery feeders of brain arteriovenous malformations

BACKGROUND

Although the embolization of lenticulostriate artery feeders is often warranted in the treatment of brain arteriovenous malformations, it is technically challenging due to steep and repeated angulations. Here, we describe our novel technique of navigating a flow-guided microcatheter into lenticulostriate artery feeders using the strong support provided by an S-shaped distal access catheter.

METHODS

We reviewed our retrospective cohort of brain arteriovenous malformations, in which lenticulostriate artery feeders were attempted to embolize.

RESULT

During the study period, endovascular embolization was performed in 25 arteriovenous malformations cases. Of these, eight lenticulostriate artery feeders were present in six cases (24%). In two cases, lenticulostriate artery feeder catheterization was avoided from the beginning due to the small diameters of the feeders. After all, microcatheter navigation for lenticulostriate artery feeders were attempted in four cases with six lenticulostriate artery feeders. In all the six feeders, the S-shaped distal access catheter was successful in supporting the microcatheter to advance distally to the lenticulostriate artery feeders, even if other approaches were unsuccessful. Of the six catheterized lenticulostriate artery feeders, four were embolized. Symptomatic infarction in the lenticulostriate artery territory and mild vasospasm occurred in two cases each, but they did not result in permanent neurological deficits.

CONCLUSION

Although some potential complications need to be considered, the S-shaped distal access catheter technique appears to be an effective alternative approach to gaining access to difficult feeders of arteriovenous malformations.