Arachnoid granulations (arachnoid granulations), the cerebral arachnoid membrane forms many villi-like protrusions near the superior sagittal sinus formed by the dura mater, which protrude into the dural sinus, called arachnoid granules. Role: An important component of the cerebrospinal fluid circulation, cerebrospinal fluid seeps through these granulations into the dural sinuses and back into the veins. Arachnoid granules are clinically asymptomatic and in some cases require craniotomy when they manifest as osteolytic. The number, size, and depth often vary with age and sex; they are rare in children and appear gradually with age, and are more common in males than females in the same year. X-ray/CT line: Variable, granular translucent shadow with sharp and uneven edges, about 0.5-1.0 cm in diameter, mostly distributed on both sides of the frontoparietal sagittal suture, rarely exceeding 4.0 cm unexpectedly in the midline, usually more symmetrical. Semi-circular, or shallow arc-shaped, a few can be chisel-like bone defect changes, the depth can reach the plate barrier or even reach the outer plate. The border is well defined and a sclerotic ring is visible around it. MR manifestation: Arachnoid granules in the proximal lateral trap of the superior sagittal sinus appear as a limited bony defect in the anterior parietal area, next to the midline; the defect area has the same signal as cerebrospinal fluid, with long T1 and T2 signals; the boundary is clear, the edge is smooth, and it is connected to the subarachnoid space; the defect opening is common in the intracranial plate, often not crossing the plate barrier and the outer plate; there is no soft tissue mass shadow and no occupying effect in the surrounding area; there is no enhancement on the enhancement scan.