Surgery of basal ganglia, thalamic, and brainstem arteriovenous malformations

Surgical management of arteriovenous malformations (AVMs) of the basal ganglia, thalamus, and brainstem poses significant challenges that distinguish these lesions from more superficial AVMs. While convexity or cerebellar AVMs are approached with simple craniotomies that widely expose the nidus for safe, perpendicular dissection of margins, the deep location of basal ganglia, thalamic, and brainstem AVMs requires more elaborate surgical approaches. Such approaches provide limited exposure that often requires more tangential dissection of the AVM margins. In addition, the location of these deep AVMs within eloquent tissue and their supply by critical perforators adds to the surgical challenges. Consequently, neurosurgeons often favor stereotactic radiosurgery or observation over surgical resection for these lesions. However, AVMs of the basal ganglia, thalamus, and brainstem have more aggressive natural histories than other AVMs and, therefore, warrant intervention. Annual hemorrhage rates have been reported to be as high as 10-34% [1-3], with associated hemiparesis rates up to 85% [1] and mortality rates as high as 63% [4]. These lesions also have increased risks associated with radiosurgical management because the basal ganglia, thalamus, and brainstem are exquisitely sensitive to radiation side-effects and hemorrhage during the latency period [5-10]. Finally, radiosurgical obliteration rates with deep-seated AVMs are lower than in other locations [6,11]. For these reasons, experienced neurosurgeons have challenged the belief that AVMs of the basal ganglia, thalamus, and brainstem are inoperable [12]. As discussed here, with careful patient selection and a firm understanding of the relevant anatomy, microsurgical resection of basal ganglia, thalamic, and brainstem AVMs can be a safe and definitive treatment. Basal ganglia and thalamic arteriovenous malformations The basal ganglia and thalamus originate from the deep core of the cerebrum where the telencephalon and diencephalon fuse during embryological development. This complex region has been variably described as the insular block, central area, and central core, among other names. Surgically, it is most informative to divide this region into the basal ganglia, thalamus, and insula.