sakrale extradurale Arachnoidalzyste
Occult intrasacral meningocele is a rare congenital lesion characterized by the presence of a cyst within the sacral thecal sac. It is an extradural sacral arachnoid cyst - Nabor type Ib meningeal cyst. It is not a true meningocele.
It is associated with spinal dysraphism, tethered cord syndrome and Tarlov cysts. It is usually a fortuitous finding on MRI in teenagers or the elderly, but very large cysts can be symptomatic. It is rarely diagnosed in children.
Radiographic features
CT
Typically seen as a hypoattenuating lesion (isodense to CSF) enlarging the sacral thecal sac, which may displace the nerve roots.
MRI
MRI is the best modality to evaluate an occult intrasacral meningocele. It consists of an extradural sacral arachnoid cyst, where signal characteristics are typically:
- T1: hypointense (follows CSF signal)
- T2: hyperintense (follows CSF signal)
- T1C+ (Gd): no enhancement
- DWI: hypointense, no restricted diffusion
Differential diagnosis
General imaging differential considerations include
- Tarlov cyst
- dorsal meningocele
- dural dysplasia
- caudal regression syndrome: only when the cyst is very large, but easily distinguishable on MRI
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Assoziationen und Differentialdiagnosen zu sakrale extradurale Arachnoidalzyste:
