Object: The authors conducted a study to determine the factors associated with right-sided language dominance in patients with cerebrovascular malformations.
Methods: Twenty-two patients with either arteriovenous malformations (AVMs [15 cases]) or cavernous malformations (7 cases) underwent functional MR (fMR) imaging studies of language function; a 3.0-T head-only unit was used. Lateralization indices were calculated separately for Broca and Wernicke areas. Lesion size, Spetzler-Martin grade, and the distance between the lesion and anatomically defined language cortex were calculated for each patient.
Results: Right-sided language dominance occurred in 5 patients, all of whom had AVMs within 10 mm of canonical language areas. Three patients had right-sided language dominance in the Wernicke area alone whereas 2 had right-sided language dominance in both Broca and Wernicke areas. Wada testing and intraoperative electrocortical stimulation were performed as clinically indicated to corroborate fMR imaging findings.
Conclusions: The primary factor associated with right-sided language dominance was the AVM being within 10 mm of anatomically defined language areas. The lesion size and the Spetzler-Martin grade were not significant factors. Anomalous fMR imaging laterality was typically confined to the language area proximate to the lesion, with the distal language area remaining in the left hemisphere dominant. This study emphasizes the need to map each case individually in patients with left perisylvian AVMs. Assumptions about eloquent cortex based on anatomical landmarks (a key component of Spetzler-Martin grading) may have to be reconsidered.