This patient has a known vestibular schwannoma, being treated with radiotherapy. Follow-up MRI was performed. Coronal gadolinium-enhanced MPRAGE shows a rounded tumour in the right cerebellopontine angle, with extension into the internal auditory meatus. The IAM is expanded. This is the ice-cream cone sign.

Some facts about vestibular schwannoma:
1. Most vestibular schwannomas have an intracanalicular component, however 20% are extracanalicular.
2. Significant signal heterogeneity with cystic or haemorrhagic areas is more typical of vestibular schwannoma than meningioma.
3. Bilateral vestibular schwannomas are diagnostic of neurofibromatosis type 2.
Reference: Dahnert W. Radiology Review Manual 5th edition. Lippincott, Williams & Wilkins 2003

Credit: Dr Laughlin Dawes