Presentation
Sacral dimple. No neurologic deficits.
Patient Data
6 mm anechoic cyst in the center of the sacral canal at the S2-3 level
There is an extradural cyst with CSF signal intensity in the sacral canal spanning the S1-3 levels, eccentric to the right, measuring 2.4 x 1.1 x 1.5 cm (SI x AP x TV) and causing smooth remodeling of adjacent bone.
Case Discussion
The findings of a cyst centrally in the sacral canal in a child is highly characteristic of an intrasacral meningocele. The differential includes Tarlov cyst, but arguing against this, no neural elements within the cyst are identified and the cyst does not extend laterally into the neural foramen. Most likely, the cyst arises as an arachnoid diverticulum from the end of the thecal sac, albeit the dural defect or stalk is not definitively seen in this case even on high-resolution T2-weighted images. As long as the patient is asymptomatic, no intervention is required. However, longitudinal imaging and clinical follow-up is advisable as surgery is indicated when there are progressive symptoms (usually pain) or growth of the cyst.
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