Giant arachnoid granulation

Case contributed by Ammar Haouimi
Diagnosis almost certain

Presentation

Chronic headaches

Patient Data

Age: 15 years
Gender: Female
mri

The MRI sequences demonstrate;

  • low lying cerebellar tonsils in keeping with Chiari I malformation
  • rounded well-defined lesion (13 mm) within the posterior aspect of the superior sagittal sinus (SSS) of low signal on T1 and FLAIR, high signalon T2 with no enhancement on the postcontrast sequence. The MRV (2D-TOF) shows a focal filling defect of the SSS at the same level. Note small intrinsic vessels crossing this lesion on the postcontrast sequence which represents displaced cortical veins or channels.

A small pineal cyst (12 mm) is noted (incidental finding)

Case Discussion

MRI features of a giant arachnoid granulation (incidental finding) in a patient with a Chiari I malformation.

Giant arachnoid granulation within the superior sagittal sinus which is a normal finding and should not be mistaken for a dural venous thrombosis. Intrinsic vessels within giant arachnoid granulations are described in the literature and appear to be displaced cortical veins or channels 1.

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