Temporal lobe arteriovenous malformations: anatomical subtypes, surgical strategy, and outcomes

Abstract

Object Descriptions of temporal lobe arteriovenous malformations (AVMs) are inconsistent. To standardize reporting, the authors blended existing descriptions in the literature into an intuitive classification with 5 anatomical subtypes: lateral, medial, basal, sylvian, and ventricular. The authors’ surgical experience with temporal lobe AVMs was reviewed according to these subtypes. Methods Eighty-eight patients with temporal lobe AVMs were treated surgically. Results Lateral temporal lobe AVMs were the most common (58 AVMs, 66%). Thirteen AVMs (15%) were medial, 9 (10%) were basal, and 5 (6%) were sylvian. Ventricular AVMs were least common (3 AVMs, 3%). A temporal craniotomy based over the ear was used in 64%. Complete AVM resection was achieved in 82 patients (93%). Four patients (5%) died in the perioperative period (6 in all were lost to follow-up); 71 (87%) of the remaining 82 patients had good outcomes (modified Rankin Scale scores 0–2); and 68 (83%) were unchanged or improved after surgery. Conclusions Categorization of temporal AVMs into subtypes can assist with surgical planning and also standardize reporting. Lateral AVMs are the easiest to expose surgically, with circumferential access to feeding arteries and draining veins at the AVM margins. Basal AVMs require a subtemporal approach, often with some transcortical dissection through the inferior temporal gyrus. Medial AVMs are exposed tangentially with an orbitozygomatic craniotomy and transsylvian dissection of anterior choroidal artery and posterior cerebral artery feeders in the medial cisterns. Medial AVMs posterior to the cerebral peduncle require transcortical approaches through the temporooccipi tal gyrus. Sylvian AVMs require a wide sylvian fissure split and differentiation of normal arteries, terminal feeding arteries, and transit arteries. Ventricular AVMs require a transcortical approach through the inferior temporal gyrus that avoids the Meyer loop. Surgical results with temporal lobe AVMs are generally good, and classifying them does not offer any prediction of surgical risk.

Current surgical results with low-grade brain arteriovenous malformations

“…4,25 Surgical results have improved over time with: (1) the creation of grading systems to select patients likely to experience optimal outcomes; 5,11,18,19,43 (2) the development of instruments such as bipolar forceps and AVM microclips to coagulate or occlude feeding arteries effectively; (3) the recognition of AVM subtypes that help decipher AVM anatomy; 5,9,17,35,36 and (4) the refinement of surgical approaches, strategies, and dissection techniques that facilitate safe AVM resection. 4,11,13,18,25,44 This impressive evolution of AVM surgery is at odds with the finding of the ARUBA Trial 23 (A Randomized trial of Unruptured Brain AVMs) that medical management alone was superior to interventional therapy for the prevention of death or stroke in patients with unruptured AVMs followed for 33 months.…”

On apples, oranges, and ARUBA

“…However, such patients represent a large portion of those with unruptured AVMs in the community, thereby compromising the generalisability of the study's findings. Furthermore, as the different AVM treatment modalities have progressed considerably during the last two decades [5,8,11,21,23], the threshold for proposing a prophylactic treatment of AVMs considered to harbour a high risk of rupture has been lowered, despite the results of different studies regarding the rupture risk factors [4,6,8,9,20]. Consequently, the patients included in ARUBA had possibly low-risk AVMs with a more favourable natural history.…”

Morbidity after Hemorrhage in Children with Untreated Brain Arteriovenous Malformation

“…Most temporal lobe is not considered eloquent region and can even be surgically resected without significant neurological deficits [25]. In addition, most temporal AVM were on the lateral convexity and inferior base of temporal lobe [26], where the eloquent regions might not be involved. Moreover, language cortex reorganization occurred in more bAVMs involving the Wernicke area of the temporal lobe than those involving the Broca area of the frontal lobe [27].…”