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Leptomeningeal cysts, also known as growing skull fractures, are an enlarging skull fracture that occurs near post-traumatic encephalomalacia. The term cyst is actually a misnomer, as it is not a cyst, but an extension of the encephalomalacia. Hence, it is usually seen a few months post-trauma.
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The majority occur in children <3 years. They complicate ~1% of skull fractures 4.
Children can present with 5:
The exact pathogenesis remains unclear 5 but it is thought they occur secondary to skull fractures causing dural tears allowing the leptomeninges and/or cerebral parenchyma to herniate into it 4. Pulsations from CSF erode the fracture margin, resulting in eventual expansion and non-union 6.
- round or oval lucency with smooth margins 4
CT scan is the modality of choice for the evaluation of leptomeningeal cyst. It consists of a lytic calvarial lesion with scalloped edges, in which encephalomalacia invaginates. The following features may also be present 4,5:
- extracranial brain herniation
- unilateral ventricular dilatation
- porencephalic cyst
- 1. Houra K, Beros V, Sajko T et-al. Traumatic leptomeningeal cyst in a 24-year-old man: case report. Neurosurgery. 2006;58 (1): E201. Pubmed citation
- 2. Kurosu A, Fujii T, Ono G. Post-traumatic leptomeningeal cyst mimicking a skull tumour in an adult. Br J Neurosurg. 2004;18 (1): 62-4. Pubmed citation
- 3. Nalls G, Lightfoot J, Lee A et-al. Leptomeningeal cyst: nonenhanced and enhanced computed tomography findings. Am J Emerg Med. 1990;8 (1): 34-5. Pubmed citation
- 4. Liu XS, You C, Lu M et-al. Growing skull fracture stages and treatment strategy. J Neurosurg Pediatr. 2012;9 (6): 670-5. doi:10.3171/2012.2.PEDS11538 - Pubmed citation
- 5. Arora AM, Puri SKM, Upreti LM. Brain Imaging: Case Review Series. Jaypee Brothers Medical Pub. (2011) ISBN:9350253895. Read it at Google Books - Find it at Amazon
- 6. Naidich TP, Castillo M, Cha S et-al. Imaging of the Brain,Expert Radiology Series,1. Saunders. (2012) ISBN:1416050094. Read it at Google Books - Find it at Amazon