Abstract TP367: Functional preservation after microsurgical resection of eloquent AVMs is related to eloquence subtype

Introduction: There is limited literature to guide prognostication after resection of AVMs located in eloquent locations. The existing literature suffers from an over-reliance on gross measures of disability such as mRS which are less sensitive to non-motor deficits such as speech, sensory or visual deficits. In addition, all eloquent locations are frequently grouped together in common grading scales which reduces the clinical utility of such scales. This study is the first to provide granular outcomes data relating to each eloquence subtype in a large sample of this rare disease. Methods: Retrospective review of a prospectively maintained institutional database of AVMs was undertaken. Medical records and imaging were reviewed. Eloquence subtype was defined according to the potential neurological deficit corresponding to cortical or subcortical structures adjacent to the AVM (motor, sensory, visual, coordination, speech) Primary outcomes were focal neurological deficits and mRS at discharge, 6 months and 2 years postoperatively. Neurological deficits were defined as major, minor or intact at each timepoint (Table 1). Results: Of >1500 patients with AVMs in the database 815 patients have undergone one or more surgical resections. From 2000-2025, 274 patients underwent resection of AVMs in eloquent locations. 171 (62%) were ruptured. 40 patients (15%) were ≤18 years of age. 141 (51%) underwent preoperative embolization. 122 (45%) were neurologically intact preoperatively. Mean followup was 7.0±6.4 years. In patients who were intact preoperatively, 104 (85%) had a mRS of 0-2 at last followup. At last followup postoperatively 9 (7%) had a major deficit and 27 (22%) a minor deficit. Any deficits present at 2 years persisted. Eloquence subtype predicted persistent neurological deficits and mRS downgrade with speech, sensory and coordination deficits more likely to experience complete recovery of postoperative deficits (12/16, 64%) compared to visual (5/22, 23%), or brainstem deficits (1/6, 16%) (p<0.001, Table 2). Among patients with an unruptured AVM and a preoperative focal deficit, 4/9 (44%) experienced improvement or resolution of their preoperative deficit after surgical resection (1 speech, 3 visual). Conclusion: Functional preservation after AVM surgery is influenced by eloquence subtype. Preoperative focal deficit may be a novel indication for surgery.