Elsevier

World Neurosurgery

Volume 84, Issue 5, November 2015, Pages 1394-1401
World Neurosurgery

Original Article
Awake Craniotomy in Arteriovenous Malformation Surgery: The Usefulness of Cortical and Subcortical Mapping of Language Function in Selected Patients

https://doi.org/10.1016/j.wneu.2015.06.059Get rights and content

Objective

Awake craniotomy for removal of intra-axial lesions is a well-established procedure. Few studies, however, have investigated the usefulness of this approach for resection of arteriovenous malformations adjacent to eloquent language areas. We demonstrate our experience by using cortical stimulation mapping and report for the first time on the usefulness of subcortical stimulation with interrogation of language function during resection of arteriovenous malformations (AVMs) located near language zones.

Methods

Patients undergoing awake craniotomy for AVMs located in language zones and at least 5 mm away from the closest functional magnetic resonance imaging activation were analyzed. During surgery, cortical bipolar stimulation at 50 Hz, with an intensity of 2 mA, increased to a maximum of 10 mA was performed in the region around the AVM before claiming it negative for language function. In positive language site, the area was restimulated 3 times to confirm the functional deficit. The AVM resection was started based on cortical mapping findings. Further subcortical stimulation performed in concert with speech interrogation by the neuropsychologist continued at key points throughout the resection as feasible. The usefulness of cortical and subcortical stimulation in addition to patient outcomes was analyzed.

Results

Between March 2009 and September 2014, 42 brain AVM resections were performed. Four patients with left-sided language zone AVMs underwent awake craniotomy. The AVM locations were fronto-opercular in 2 patients and posterior temporal in 2. The AVM Spetzler-Martin grades were II (2 patients) and III (2 patients). In 1 patient, complete speech arrest was noticed during mapping of the peri-malformation zone, which was not breached during resection. In a second patient who initially demonstrated negative cortical mapping, a speech deficit was noticed during resection and subcortical stimulation. This guided the approach to protect and avoid the sensitive zone. This patient experienced mild postoperative expressive dysphasia that improved to normal within 6 weeks. Complete resection was achieved in all 4 patients. There were no other complications and no permanent neurological morbidity, resulting in good outcome in all 4 patients.

Conclusions

Language mapping, both cortical and subcortical during AVM resection, may be valuable in a very select group of AVMs in language zones. Defining safe margins and feedback to the surgeon may provide the highest chances of a surgical cure while minimizing the risk of incurring a language deficit.

Introduction

Safe microsurgical resection of arteriovenous malformations (AVMs) in eloquent areas of the dominant cerebral hemisphere can be challenging. Several landmark studies have indicated that most low-grade AVMs are best treated microsurgically, because the obliteration rate is very high with low morbidity 8, 9, 16, 24. In more contemporary AVM literature, there has been increasing evidence that the true surgical risks we quote may not be as straightforward as much of the historical literature has portrayed. Convincing evidence has demonstrated that AVMs in eloquent locations approaching 3 cm, and up to 6 cm actually, represent a group with greater surgical risks not fully appreciated in neurovascular practice 5, 11, 17, 24.

In this work, we describe our experience in 4 patients harboring AVMs very close to the language cortex. All patients underwent awake mapping and neuropsychological assessment to confirm resectability and inform the optimal surgical approach to the lesion. We also describe the use of subcortical stimulation with interrogation of language function throughout the process of microsurgical resection, which to our knowledge has not been reported before. On the basis of our experience and careful review of the literature, we believe there exists a subgroup of patients with AVMs near eloquent language cortex in which this approach should be considered.

Section snippets

Methods

Between March 2009 and September 2014, 42 patients with brain AVMs were operated on by the lead author (A.D.). A flow chart depicting the management of these patients is depicted in Figure 1. Four patients who harbored AVMs near critical speech areas in the left hemisphere were selected for wakeful resection. These 4 patient's demographics and the AVM characteristics are described in Table 1. Eloquent location was first identified anatomically on magnetic resonance imaging (MRI) and then

Results

Each of the 4 patients demonstrated some language activation on fMRI 5–10 mm from the AVM nidus. The AVM locations were frontal-opercular in 2 and posterior temporal in 2. The AVM Spetzler-Martin grade (SMG) was II (2 patients) and III (2 patients). Preoperative embolization was performed in one patient. Cortical or subcortical stimulation influenced the surgical approach in 2 of 4 cases. These interrogations did not result in a subtotal resection or abortion of the procedure in any case. In 1

Understanding of Surgical Risk and Eloquence

As the number of published series addressing surgical risk in AVM resection has grown, it is evident that the surgical risks for lower-grade AVMs have been underestimated. It has been demonstrated that resection of grades 1–2 in noneloquent areas resulted in adverse outcomes in 0.6% of the time and as high as 9.5% for AVMs in eloquent brain (17). Lawton et al. (11) proposed an expanded SMG scale separating the heterogeneous grade III into three distinct subgroups, (3−, 3, and 3+). In their

Conclusions

Certain anatomical features of AVMs and fMRI activation profiles may identify patients with SMG 2–3 AVMs in close proximity (5 mm or more) to eloquent language cortex where awake cortical mapping is a viable strategy to maximize safety of AVM resection. Furthermore, maintenance of a wakeful state during dissection and resection of the AVM may provide valuable information to the surgeon via stimulation of subcortical white matter. We believe this methodology is a reasonable and effective

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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