Giant arachnoid granulation with a thrombosed dural arteriovenous fistula.

Arachnoid granulations are common incidentally detected small dural lesions which are usually asymptomatic and follow cerebrospinal fluid density/signal intensity on CT/MRI. Such lesions reaching a size of more than 1 cm are termed as giant arachnoid granulations (GAGs) which have been previously reported to cause venous hypertension and headaches. We report a case of GAG involving the proximal half of the superior sagittal sinus in a 45-year-old male patient which was associated with left temporal thrombosed dural arteriovenous fistula (AVF) whose thrombosed draining veins were seen converging towards the site of GAG. The patient presented with three episodes of generalised tonic-clonic seizures and improved with conservative treatment. No reports of such association of GAG with AVF is available in the literature, and we believe it could have occurred due to venous hypertension induced by GAG.