Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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June 2, 2016
Giant Temporal Intradiploic Arachnoid Cyst
- Background:
- Intradiploic arachnoid cyst is a rare entity. The exact origin is unclear.
- Some reported cases have clear traumatic history, and the cyst is thought to represent a variant of the “growing fracture” characteristically seen in children.
- These lesions may also be called intradiploic pseudomeningoceles or intraosseous leptomeningeal cysts.
- In other cases, when there is no history of trauma and when a small round dural opening is identified, a congenital origin is favored.
- Clinical Presentation:
- Long-standing lesion presenting with symptoms of pain and/or bulging
- There may be history of trauma.
- Negative workup for metastasis or multiple myeloma
- Key Diagnostic Features:
- Cystic intraosseous cranial lesion following CSF density on CT and CSF signal intensity on MRI
- Absence of restricted diffusion or contrast enhancement
- Possible associated signs of remote trauma
- Differential Diagnoses of lytic lesions of the skull include:
- Multiple myeloma
- Eosinophilic granuloma
- Metastatic carcinoma
- Epidermoid cyst
- Hemangioma
- Paget disease
- Treatment:
- If symptomatic (pain or cosmetic defect), the treatment is surgical, with excision of the cyst, repair of the dural defect, and bony reconstruction.
- This patient had an irregular dural defect in continuity with the subarachnoid space, working as a unidirectional valve (see intraoperative images). Once repaired, the patient’s symptoms resolved, and the cyst did not recur.
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