Pleomorphic xanthoastrocytoma with dural involvement

Clinical History

A 13-month-old female infant is brought to consultation due to repeated spastic seizures during the 2 previous months, without loss of consciousness, which have progressively become more frequent, now occurring up to 5-6 times a day. The patient is initiated on anti-epileptic drugs and a cranial MRI is performed.

Imaging Findings

Initial MRI (figure 1) demonstrates a cystic lesion located in the left anterior temporal pole with slight T2/FLAIR hyperintensity of the adjacent parenchyma. No contrast enhancement is visible. The lesion is considered suggestive of a low-grade glioma or ganglioglioma.
The patient is followed with consecutive, yearly MRI scans, without significant change in between.

Follow-up MRI performed 4 years later (figure 2) identifies the same lesion, of similar size, but which now shows a large, intensely-enhancing extraaxial component in the adjacent skull-base with fine dural tail. This extraaxial component, which represents meningeal involvement is highly suggestive of pleomorphic xanthoastrocytoma.

The tumour is resected (left temporal lobectomy) and pathology confirms a pleomorphic xanthoastrocytoma with anaplastic characteristics and leptomeningeal infiltration.

Seizures are correctly controlled after surgery and anticonvulsant drugs withdrawn.

Discussion

A.-Background and Clinical Perspective
Pleomorphic xanthoastrocytoma (PXA) is a type of WHO grade II glial tumour. It is rare, comprising less than 1% of all brain tumours and affects mainly children and young adults [1, 2].

The tumour is supratentorial in up to 98% of cases and frequently involves cortex and meninges [2].

Seizures are the most common form of presentation, occurring in most cases. Other initial symptoms include headache, nausea and dizziness [3].

B.-Imaging Perspective
PXA are almost always situated supratentorially (>90%), most commonly in the temporal lobe (40-50%) followed by frontal and parietal lobes [3].

These tumours frequently have a cystic component isointense to CSF (50-60%), and are located in cerebral hemispheres with involvement of meninges. The solid component is usually hyperintense in T2 and FLAIR, enhances intensely and homogenously in CT and MRI, and may show diffusion restriction [1, 2, 4]. Reaction of the adjacent meninges forming a typical "dural tail" is fairly specific and may be a useful discriminating feature [4].

C.-Differential Diagnosis
- Ganglioglioma: Very similar appearance and location. It often calcifies and does not show dural reaction.
- Pilocytic astrocytoma: Most commonly infratentorial (especially in children).
- DNET: May calcify. Slow-growing lesion often abuts and remodels calvarium.
- Oligodendroglioma: Gross calcifications. Usually involves cortex (with signal change and thickening).
- Meningioangiomatosis: cortical/subcortical mass with gross calcification and enhancing meningovascular proliferation.

D.-Outcome
PXA is usually circumscribed and slow-growing. Surgery is the treatment of choice, and recurrence is uncommon with 70% survival at 10 years.

E.-Teaching Points
- Supratentorial (temporal) cyst with an intensely enhancing mural nodule.
- Child or young adult with long standing epilepsy, most common presentation
- Often difficult to differentiate from other cystic-nodular supratentorial lesions. Identification of an enhancing dural tail may be a key discriminating factor.

Differential Diagnosis List

Final Diagnosis

Pleomorphic xanthoastrocytoma with dural reaction.

URL:	https://www.eurorad.org/case/14216
DOI:	10.1594/EURORAD/CASE.14216
ISSN:	1563-4086