SHM Converge Scientific Abstract ePoster Gallery-Giant Arachnoid Granulations Mimicking Transverse Sinus Thrombosis

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Giant arachnoid granulations (GAGs) are benign protrusions into the dural venous sinuses, most often the transverse sinus, and can closely resemble transverse sinus thrombosis (TST) on imaging. Correct diagnosis is important because GAGs usually need no urgent treatment, while TST can be life-threatening and requires anticoagulation or more aggressive intervention.<br /><br />This case describes a 70-year-old woman with hypertension, hyperlipidemia, migraines, and recurrent headaches that worsened over one week. Initial CT head and chest X-ray were negative. MRI brain suggested a possible right cerebellar AVM, and CT venography showed an apparent filling defect in the right transverse/sigmoid sinus, raising concern for sinus thrombosis versus an extrinsic lesion such as an arachnoid granulation. However, MR venography showed patent venous sinuses, excluding thrombosis. A high-volume lumbar puncture revealed elevated opening pressure of 31 cm H2O and improved her headache. She was discharged on acetazolamide (Diamox) with neurology follow-up.<br /><br />The discussion explains that GAGs are composed of arachnoid tissue and CSF-containing spaces that project into venous sinuses and help return CSF to venous blood. They are commonly located near the transverse sinus. Imaging clues favoring GAGs over thrombosis include a focal, well-defined nodular defect rather than complete sinus occlusion. On MRI/MRV, GAGs typically appear as non-enhancing lesions with characteristic central features and preserved surrounding flow, whereas thrombus often shows clot signal changes and venous flow obstruction.<br /><br />The key message is that giant arachnoid granulations should always be considered when a focal sinus filling defect is seen, and MRI with contrast-enhanced MR venography is the best tool to distinguish them from true dural sinus thrombosis.

Asset Subtitle

Sara Hassan

Meta Tag

Author List Fahim Imtiaz, Sara Hassan

Category Clinical Vignettes

Concept Giant Arachnoid Granulation

Concept Transverse Sinus Thrombosis

Concept Filling Defect

Concept Magnetic Resonance Imaging

Concept Magnetic Resonance Venography

Distinguished Non-Finalist

Presenter Organization Ocean University Medical Center

Presenting Author Sara Hassan

Track Adult

Keywords

giant arachnoid granulations

transverse sinus thrombosis

dural venous sinuses

MR venography

CT venography

filling defect

intracranial hypertension

lumbar puncture

acetazolamide

imaging differential diagnosis

Giant Arachnoid Granulation

Transverse Sinus Thrombosis

Filling Defect

Magnetic Resonance Imaging

Magnetic Resonance Venography