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, since meninges are not involved.
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.
Typically seen as a hypoattenuating lesion (isodense to CSF) enlarging the sacral thecal sac, which may displace the nerve roots.
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
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
- 1. Turgut M, Akyüz O, Unsal A. Occult intrasacral meningocele: case report and review of the literature. Zentralbl. Neurochir. 2007;68 (1): 34-7. doi:10.1055/s-2007-968169 - Pubmed citation
- 2. Franco GM, Lopes H, Pires LA et-al. [Occult intrasacral meningocele: case report]. Arq Neuropsiquiatr. 2001;59 (3-B): 817-20. Arq Neuropsiquiatr (link) - Pubmed citation
- 3. Okada T, Imae S, Igarashi S et-al. Occult intrasacral meningocele associated with spina bifida: a case report. Surg Neurol. 1996;46 (2): 147-9. Surg Neurol (link) - Pubmed citation
- 4. Doi H, Toyoda I, Matsumoto K et-al. Occult intrasacral meningocele with tethered cord--case report. Neurol. Med. Chir. (Tokyo). 1995;35 (5): 321-4. Neurol. Med. Chir. (Tokyo) (link) - Pubmed citation
- 5. Vogelsang H. [Intrasacral meningoceles]. Rontgenblatter. 1985;38 (3): 67-71. - Pubmed citation
- 6. Doty JR, Thomson J, Simonds G et-al. Occult intrasacral meningocele: clinical and radiographic diagnosis. Neurosurgery. 1989;24 (4): 616-25. - Pubmed citation