Age: Female
Sex: 80
Indication: Headache
Arachnoid Granulation
Mimicking Thrombus
Findings Relating to the Mimic
- Small rounded filling defect within the right transverse sinus, compatible with an arachnoid granulation.
Discussion
- Arachnoid granulations are common, with a prevalence of approximately 60%.
- They are protrusions of arachnoid through the dura mater, which allow CSF to extend from the subarachnoid space into the venous sinus or into the calvarium.
- They most commonly occur in the superior sagittal and transverse sinuses.
- On non-contrast head CT they are CSF density and on post-contrast imaging they appear as round, focal filling defect in the dural sinus. Usually they are small (<10mm), but occassionally can be “giant” (>10mm). If they involve the calvarium, they appear as a circumscribed lucent lesion.
- Usually these granulations are easy to differentiate from thrombosis given their round, well-circumscribed appearance and typical location.
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