Successful neurosurgery to remove tumours around the base of the skull, such as a vestibular schwannoma, depends on achieving maximal tumour removal whilst preserving crucial neurological functions such as facial movement, and maintaining quality of life.

Current techniques to direct surgery are based on the surgeon's expertise and knowledge of the relevant anatomy, supplemented by the use of electrical recording and stimulation of the facial nerve. However, it is often very difficult to visualise the nerve during surgery and facial nerve paralysis remains a potentially devastating complication of surgery.

Advanced imaging methods may be used to visualise important neural connections in the brain and computer-assisted processing can generate tumour maps from MRI and ultrasound scans. This study aims to utilise these technologies to develop a 3D navigation system for skull base surgery.

This study aims to develop a system that will combine MRI and intraoperative ultrasound imaging to enhance the surgeon's view of the tumour, facial nerve and other surrounding critical structures during surgery. This information will be made available in the navigation system in the operating room so that operations are more precise resulting in better tumour removal rates and fewer complications.

The system will be assessed during the treatment of 20 patients with vestibular schwannoma at the National Hospital for Neurology and Neurosurgery. This feasibility study will validate the different parts of the new system and help us design a future research study to determine its effectiveness in improving patient care.

This project will result in safer and more effective neurosurgery, with potential consequent financial savings for the NHS and the UK, in addition to marked improvements in the quality of life of patients and reduced dependency upon others.

Inclusion Criteria:

• Adult patients aged 18-85 years
• Patients with a vestibular schwannoma who are scheduled for surgery
• Patients willing and able to provide written informed consent

Exclusion Criteria:

• Patients aged under 18 years of age or older than 85 years
• Previous, treated posterior fossa brain tumour(s)
• Previous ear or facial surgery on ipsilateral side of tumour
• Neurofibromatosis Type II
• Participation in other clinical trials
• Any contraindication for MR imaging
• Any contraindication for MR contrast agent administration
• Any contraindication for CT imaging
• Pregnancy or breast feeding

Adult patients aged 18 - 85 years with a vestibular schwannoma who are scheduled for surgery and able to provide written informed consent.