Amobarbital evaluation of neurobehavioral function prior to therapeutic occlusion of brain arteriovenous malformations: a new neuropsychological procedure

Endovascular advances for brain arteriovenous malformations

Arteriovenous malformations (AVMs) of the brain represent unique challenges for treating physicians. Although these lesions have traditionally been treated with surgical resection alone, advancements in endovascular and radiosurgical therapies have greatly expanded the treatment options for patients harboring brain AVMs. Perhaps no subspecialty within neurosurgery has seen as many advancements over a relatively short period of time as the endovascular field. A number of these endovascular innovations have been designed primarily for cerebral AVMs, and even those advancements that are not particular to AVMs have resulted in substantial changes to the way cerebral AVMs are treated. These advancements have enabled the embolization of cerebral AVMs to be performed either as a stand-alone treatment, or in conjunction with surgery or radiosurgery. Perhaps nothing has impacted the treatment of brain AVMs as substantially as the development of liquid embolics, most notably Onyx and n-butyl cyanoacrylate. However, of near-equal impact has been the innovations seen in the catheters that help deliver the liquid embolics to the AVMs. These developments include flow-directed catheters, balloon-tipped catheters, detachable-tipped catheters, and distal access catheters. This article aims to review some of the more substantial advancements in the endovascular treatment of brain AVMs and to discuss the literature surrounding the expanding indications for endovascular treatment of these lesions.

Temporary test occlusion of distal middle cerebral artery using GDC coil

The treatment of small distal intracranial aneurysms often requires parent vessel occlusion. However, this may be particularly challenging in patients in which the parent vessel serves eloquent brain. Superselective amytal testing is often conducted in these cases, but may prove unreliable or inconclusive. In order to more specifically assess the functional significance of the parent vessel in this patient with a distal left middle cerebral artery pseudoaneurysm who had failed superselective amytal testing, we used a Guglielmi Detachable coil to perform a temporary test occlusion. Testing was performed with the patient awake and examinable, and after no neurological changes were noted, the vessel was permanently occluded, successfully treating the aneurysm. To our knowledge, this is the first report to describe this unique method for assessing a parent vessel that previously had been thought to supply eloquent brain during amytal testing.

Neurologie des malformations artérioveineuses cérébrales

INTRODUCTION

Brain arteriovenous malformations (AVMs) constitute a neurovascular disorder that comes to clinical attention mainly in young adults in their mid thirties. Associated symptoms often require neurological treatment for symptomatic seizures (focal or generalized), headaches (episodic or chronic), progressive neurological deficits, or spontaneous AVM rupture leading to intracerebral, intraventricular, and/or subarachnoid hemorrhage.

STATE OF ART

Little data exist in the medical literature regarding the natural history risk of the disease and no controlled studies are available on the risk of invasive AVM treatment (endovascular, neurosurgery, radiotherapy).

PERSPECTIVES

This review focuses on all aspects of neurological brain AVM management and discusses possible predictors of the natural history risk as well as the benefit and risk of invasive treatment.

CONCLUSIONS

AVM patient management is ideally based on a trans-disciplinary approach via a neurovascular team of neurologists, neuroradiologists, neurosurgeons, and radiotherapists. A newly diagnosed AVM does not necessarily represent an a priori indication for interventional treatment. The decision in favor or against therapy mainly depends on clinical criteria (ruptured versus unruptured AVM, neurological exam, patient age and co-morbidity, etc.) and the angioarchitecture of the malformation. The ARUBA study is going to be the first randomized clinical trial comparing the risk of invasive treatment versus non-invasive management.

Neuropsychological function and brain arteriovenous malformations: redefining eloquence as a risk for treatment

Arteriovenous malformations (AVMs) of the brain, thought to begin during fetal development and undergo an unclear maturation process; most often do not become symptomatic until the patient reaches adulthood. Authors of recent prospective studies have suggested that relatively few patients present with neuropsychological abnormalities in the absence of hemorrhage. In general, neuropsychological evaluations in patients with AVMs have yielded mixed results with respect to localization of function, and the authors of most cognitive studies have not been able to demonstrate the nature and degree of impairment seen in acute ischemic stroke in comparable brain regions. Superselective Wada testing prior to therapeutic embolization, functional imaging studies, and intrasurgical cortical mapping have shown redistribution of language and memory to unpredictable regions. Developmental cognitive history in these patients indicates that most will have at least some background of learning problems during the school-age years with varying degrees of severity, reflecting a time when brain reorganization may be occurring. These data suggest that traditional assumptions about the eloquence of brain regions may not hold for patients with AVMs and that establishing treatment risk in the individual patient needs to be made on an empirical basis.

Interhemispheric transfer of language in patients with left frontal cerebral arteriovenous malformation

Cerebral arteriovenous malformations (AVMs) are frequently evaluated before therapeutic embolization by superselective injection of anesthetics into individual arterial branches so as to determine whether permanent occlusion would affect eloquent function. In Experiment 1, we used this adaptation of the Wada procedure to study three right-handed adult patients with left frontal cerebral AVMs by injecting vessels in Wernicke's and Broca's areas, respectively, and assessing language functions. The results showed that superselective testing in the inferior division of the left MCA in all three patients produced a dense Wernicke's aphasia. Injections into the left frontal regions, however, resulted in right paresis in all patients, but no language deficits including no loss of fluency. In Experiment 2, Patient 2 underwent fMRI activation for spontaneous word-list generation using multi-slice echo planar BOLD techniques at 1.5 Tesla. A voxel-by-voxel comparison of rest vs activation for each task was performed with a Z-score threshold of 2.5 SD for activated voxels. There was activation in the right hemisphere in the insula, frontal operculum pars opercularis, and inferior frontal gyrus, an area homologous to Broca's area in the left hemisphere. There was also activation in the left hemisphere in the Rolandic region, but language function was unaffected during Wada testing in this area. These data suggested that features of expressive language were no longer controlled by the left frontal lobe where the AVM was located, and provided new evidence for interhemispheric re-organization under conditions of chronic neurovascular disease.