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Schwannomatosis is characterized by multiple non-intradermal schwannomas with patients often presenting with a painful mass in their extremities. In this syndrome malignant transformation of schwannomas is rare in spite of their large size at presentation. Non-invasive measures of assessing the biological behavior of plexiform neurofibromas in neurofibromatosis type 1 such as positron emission tomography (PET), CT scanning and MRI are well characterized but little information has been published on the use of PET imaging in schwannomatosis. We report a unique clinical presentation portraying the use of PET imaging in schwannomatosis. A 27-year-old woman presented with multiple, rapidly growing, large and painful schwannomas confirmed to be related to a constitutional mutation in the SMARCB1 complex. Whole body PET/MRI revealed numerous PET-avid tumors suggestive of malignant peripheral nerve sheath tumors. Surgery was performed on multiple tumors and none of them had histologic evidence of malignant transformation. Overall, PET imaging may not be a reliable predictor of malignant transformation in schwannomatosis, tempering enthusiasm for surgical interventions for tumors not producing significant clinical signs or symptoms.

We describe the case of a 42-year-old female presenting with subarachnoid haemorrhage from a posterior inferior cerebellar artery (PICA) aneurysm rupture on intracranial digital subtraction angiography (DSA). One year postoperatively, the patient was followed with CT angiography and was reported to show a de novo aneurysm at the bifurcation of the left inferior cerebellar artery (ICA). Subsequent DSA revealed an aberrant vein crossing over the ICA bifurcation on mask phase images. This is the first reported case of a such a reason for a ‘false positive’ on CT angiography (CTA). The case demonstrates that although CTA has a reported high specificity, careful interpretation of multiple views is required to diagnose intracranial aneurysms when compared to the ‘gold’ standard of CTA.

This patient has the hallmark of neurofibromatosis type 2 (NF2)–bilateral vestibular schwannomas (VS) – as well as multiple intracranial meningiomas. At the second operation, two tumours were found adjacent to each other on the left side. The caudal aspect of the left VS was removed followed by complete removal of the adjacent tentorial lesion-a meningioma. Subsequent further removal the left VS was limited by decreased amplitude of the brainstem evoked auditory response (BEAR). Resection was limited due to the need to retain hearing on the sole hearing side. Postoperatively, she recovered well and the left sided hearing was preserved. She had a left facial palsy immediately postoperatively, which improved to normal within one month. Histopathological examination demonstrated a VS on the right (MIB–1 labeling index 6%). On the left, the VS had a MIB–1 labeling index of 10%, which may explain its rapid growth. The other lesion was confirmed to be a meningioma (MIB–1 labeling index 5%). NF2 is an autosomal dominant inherited disorder. The responsible gene is located on chromosome 22q12. The diagnostic criteria for NF2 are