CASE 4965 Published on 10.08.2006

Cystic Trigeminal Schwannoma

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Katti AR, Aw Yeang H, Das K

Patient

54 years, female

Clinical History
Reduced hearing in left ear for 9 months, odd sensations affecting right Trigeminal V2 distribution intermittently.
Imaging Findings
MRI of the cranium was performed with the following sequences: axial, coronal, sagittal planes with T1, T2 spin-echo sequences, FLAIR axial and post-gadolinium T1 spin-echo sequences. There is a dumbbell shaped 5 x 2cm lesion which is extending from the right side of the cerebello-pontine angle into the right Meckel's cave and markedly indenting the pons. The lesion is hypo intense to the brain on T1-weighted images and hyper intense on T2-weighted images suggesting its cystic nature. Post gadolinium images show rim enhancement. CT scan performed to look for bony detail demonstrates rim enhancement with a biloculated cystic lesion in the right side of brainstem with some erosion of the petrous ridge and the medial sphenoid on the right suggestive of pressure erosion. This patient underwent stereotactic aspiration of the cyst followed by fractionated radiotherapy. The cystic lesion refilled on follow-up imaging and further had craniectomy and drainage of multicystic lesion.
Discussion
Schwannomas are benign encapsulated nerve sheath tumour composed of differentiated schwann cells arising from all myelinated cranial nerves (exceptions: olfactory and optic nerves). Trigeminal schwannomas constitute 5% of all intracranial neuromas. (90% arise from vestibular portion of 8th cranial nerve). The tumours of the trigeminal nerve may be seen along the course of the nerve, involving its pontine cisternal segment, gasserian ganglion within Meckel's cave, and the cavernous sinus. Four distinct types of trigeminal schwannomas have been categorized. The four categories include those confined to the cavernous sinus, those located within Meckel’s cave, those located within the cerebellopontine angle, and those that involve both the posterior and middle cranial fossa. The tumor in this case fits into the last category where it is a giant trigeminal schwannoma involving both the posterior and middle cranial fossa. They show erosion of petrous tip, enlargement of contiguous fissures, foramina and canals. They can distort the ipsilateral quadrigeminal cistern with anterior displacement of temporal horn. On MRI the tumours are usually well demarcated with almost isointense signal intensity characteristics with cortical grey matter, and they enhance uniformly following contrast administration. However as in above case they can show cystic nature of the tumour with rim enhancement. Trigeminal schwannomas are more likely to contain cystic areas than Vestibular ("acoustic") schwannomas. They may also reveal heterogeneous signal intensity and contrast enhancement characteristics, depending on the necrosis and haemorrhage. Differential diagnosis should include meningioma, lymphoma, vascular lesions and paraganglioma.
Differential Diagnosis List
Cystic Trigeminal Schwannoma
Final Diagnosis
Cystic Trigeminal Schwannoma
Case information
URL: https://www.eurorad.org/case/4965
DOI: 10.1594/EURORAD/CASE.4965
ISSN: 1563-4086