Normal perfusion pressure breakthrough syndrome in giant arteriovenous malformations

Intraoperative Monitoring Cerebral Blood Flow During the Treatment of Brain Arteriovenous Malformations in Hybrid Operating Room by Laser Speckle Contrast Imaging

Background

Hemodynamic changes caused by hybrid surgery for brain arteriovenous malformations (bAVM) are usually related to long-term lesions from "blood stealing". There are currently no viable low-cost, noninvasive procedures for assessing cerebral perfusion in the operating room. This study aims to investigate the use of intraoperative laser speckle contrast image (LSCI) software in AVM surgery.

Methods

In Zhongnan Hospital of Wuhan University, 14 patients who underwent surgery with LSCI were collected. To analyze the hemodynamic features of AVM and the influence on the peripheral cortex of AVM embolization and resection, we assessed the transit time between feeding arteries and drainage veins by intraoperative digital subtraction angiography (DSA). Meanwhile, LSCI was performed at pre-embolization, post-embolization, and after complete resection of bAVM.

Results

In this study, the transit time of bAVM before and after embolization was compared, the transit time before embolization was significantly shorter than that after embolization (p < 0.05). We also got good visualization of relative CBF, in addition, to flow imaging in the cortical vasculature round bAVM with LSCI. The flux of post-surgery was significantly higher than pre-embolization (p < 0.01).

Conclusion

Hemodynamic variable assessment plays an important role in the resection of AVM in the hybrid operative room and LSCI can be used to visualize and evaluate cortical cerebral blood flow to detect pathological hyperperfusion in real-time with a good spatial-temporal resolution in a sensitive and continuous, non-invasive mode.

Surgical options in ICH including decompressive craniectomy

Intracerebral haemorrhage (ICH) accounts for 15 to 20% of strokes. The condition carries a higher morbidity and mortality than occlusive stroke. Despite considerable research effort, no therapeutic modality either medical or surgical has emerged with clear evidence of benefit other than in rare aneurysmal cases. Intracerebral haemorrhages can be divided into those that arise from pre-existing macroscopic vascular lesions - so called "ictohaemorrhagic lesions", and those that do not; the latter being the commoner. Most of the research that has been done on the benefits of surgery has been in this latter group. Trial data available to date precludes a major benefit from surgical evacuation in a large proportion of cases however there are hypotheses of benefit still under investigation, specifically superficial lobar ICH treated by open surgical evacuation, deeper ICH treated with minimally invasive surgical techniques, and decompressive craniectomy. When an ICH arises from an ictohaemorrhagic lesion, therapy has two goals: to treat the effects of the acute haemorrhage and to prevent a recurrence. Three modalities are available for treating lesions to prevent recurrence: stereotactic radiosurgery, endovascular embolisation, and open surgical resection. As with ICH without an underlying lesion there is no evidence to support surgical removal of the haemorrhage in most cases. An important exception is ICHs arising from intracranial aneurysms where there is good evidence to support evacuation of the haematoma as well as repair of the aneurysm.

Is stagnating flow in former feeding arteries an indication of cerebral hypoperfusion after resection of arteriovenous malformations?

OBJECT

The authors' goal in this study was to challenge the proposed mechanism of the occlusive hyperemia theory, in which it is asserted that stagnating flow in the former feeding arteries of cerebral arteriovenous malformations (AVMs) leads to parenchymal hypoperfusion or ischemia, from which postoperative edema and hemorrhage originate.

METHODS

Cortical oxygen saturation (SaO2) was measured in 52 patients by using microspectrophotometry in areas adjacent to AVMs before and after resection. The appearance of the former feeding arteries was categorized as normal (Group A); moderately stagnating (Group B); and excessively stagnating (Group C) on postoperative angiographic fast-film series. Patients and SaO2 values were pooled accordingly and compared using analysis of variance and Duncan tests (p < 0.05). Angiographic stagnation times in former feeding arteries were correlated in a linear regression/correlation analysis with SaO2 data (p < 0.05). All values are given as the mean +/- standard deviation. The average median postoperative SaO2 in Group C (15 patients) was significantly higher than in Groups B (17 patients) and A (20 patients) (Group C, 75.2 +/- 8.5; Group B, 67.5 +/- 10.8; Group A, 67.1 +/- 12 %SaO2), as was the average postoperative increase in SaO2 (Group C. 25.9 +/- 14.9; Group B, 14.6 +/- 14; Group A, 11.1 +/- 14 %SaO2). Angiographically confirmed stagnation times were also significantly longer in Group C than in Group B (Group C, 5.6 +/- 2.5; Group B, 1.3 +/- 0.6 seconds). A significant correlation/regression analysis showed a clear trend toward higher postoperative SaO2 levels with increasing stagnation time.

CONCLUSIONS

Stagnating flow in former feeding arteries does not cause cortical ischemia, but its presence on angiographic studies is usually indicative of hyperperfusion in the surrounding brain tissue after AVM resection. In the context of the pathophysiology of AVMs extrapolations made from angiographically visible shunt flow to blood flow in the surrounding brain tissue must be regarded with caution.

Strategic embolisation for successful resection of a large cerebral arteriovenous malformation

The risks accompanied by the treatment of cerebral arteriovenous malformation (AVM) are still cumulative despite recent progress in available treatment options. Pre-operative embolisation is one such option, however, it seldom makes the surgical resection difficult. The excessive embolised nidus makes the surgical resection difficult because it cannot be compressed during the resection surgery and embolised nidus as a 'glue ball' with marginal hypervascular territory is most difficult to remove. The aim of pre-operative embolisation for successful surgical resection is to put glue into the marginal part of the nidus so as to make a cleavage between the surrounding normal tissues. Remaining feedings via the dilatated leptomeningeal anastomoses from surrounding normal cortical arteries do not interfere with the resection and can be eliminated easily by coagulating the pia matter around the nidus. Strategic planning with regard to the systemic course of treatment, including the manner of resection, is important for effective pre-operative embolisation.

Management of residual dysplastic vessels after cerebral arteriovenous malformation resection: implications for postoperative angiography

OBJECTIVE

The verification of surgical resection of cerebral arteriovenous malformations (AVMs) relies on angiography. Abnormal vasculature often is identified after removal of the AVM. Differentiation of dysplastic feeding vessels that resemble the neovascularity of moyamoya disease, as distinct from residual AVM, is crucial for preserving critical brain areas. We review a large experience with immediate postoperative angiography after AVM resection and discuss the implications for management of abnormal dysplastic vessels discovered after AVM resection.

METHODS

Beginning in 1992, 86 consecutive patients with AVMs underwent operations by standard protocol for immediate postoperative angiography under the same general anesthetic. Angiographic interpretation dictated admission to the intensive care unit or return to the operating room for further resection.

RESULTS

In 78 patients, the angiogram revealed complete resection. Two patients were returned to the operating room, one for residual malformation with an early draining vein, and one for resection of residual dysplastic vessels. There was one postoperative hemorrhage in a patient whose postoperative angiogram was falsely negative for AVM. Six patients with residual dysplastic vessels mimicking residual AVM, but without an early draining vein, were managed conservatively. Delayed follow-up angiography demonstrated spontaneous involution of these abnormal vessels in all of these patients.

CONCLUSION

Residual dysplastic feeding vessels resembling the neovascularity of moyamoya disease but not associated with an early draining vein do not necessarily represent residual malformation after AVM resection. The abnormal vessels will proceed to complete spontaneous resolution. Given the difficulty of interpreting intraoperative angiography, immediate postoperative angiography may be a viable alternative after AVM resection.