This is a retrospective review of 15 patients with orbital schwannomas comparing the radiological characteristics, in particular the signal intensity on MRI with the histological sub-types of the tumours. Five patients had MRI imaging alone, three had CT alone and seven had both modalities. Initial diagnoses included schwannoma, dermoid cyst, lymphangioma, cavernous haemangioma, solitary fibrous tumour, epidermal cyst and optic nerve meningioma. Tumours were distributed throughout the orbit with three extending intracranially, and had round to fusiform configurations. No patient had sensory dysfunction. T1 imaging was performed in 11 patients, 10 showed an overall low intensity signal which was heterogeneous in seven. T2 imaging was done in 10, of which nine had an overall high intensity signal, which was heterogeneous in eight. Tumour cavities were present in 11, 10 of which were multiloculated. Antoni A pattern areas on histology (tightly packed Schwann cells with nuclear palisading) were associated with high intensity on gadolinium-enhanced T1 images, and hypointensity on T2. Antoni B areas (loosely packed Schwann cells) were associated with hypointensity on gadolinium-enhanced T1 and hyperintensity on T2. The authors comment that because of the histological variation the radiological appearance can also be wide-ranging. This is further complicated by degenerative changes including calcification, cavity formation and haemorrhage. This is an interesting study made possible by the en-bloc excision of the schwannomas. It is limited by small numbers and the fact that not all patients underwent the same imaging. 

Orbital schwannoma: radiographic and histopathologic correlation in 15 cases.
Pointdujour-Lim R, Lally SE, Shields JA, et al.
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James Hsuan

Aintree University Hospital, Liverpool, UK.

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