Technology
operations are usually performed collaboratively with ENT and neurosurgery skull base surgeons.
Translabyrinthine or retrosigmoid approach
Depending on the configuration of the tumour, and surrounding structures, this may be most commonly performed via a ‘translabyrinthine’ approach. This method traverses the hearing and balance structures of the ear, or a ‘retrosigmoid’ approach performed alongside the brain’s balance organ, the ‘cerebellum’. There is also the option of ‘middle fossa’ approaches in selected circumstances.
Avoiding the facial nerve The crucial aspect of surgery is to safely remove enough tumour without damaging normal structures, such as the facial nerve. During surgery this nerve is monitored with an electrophysiological probe to ensure it is functioning normally. It is our practice to perform ‘facial nerve sparing’ surgery and where a portion of tumour is often deliberately left behind on the nerve to preserve its function. If this residual tumour grows subsequently, it can then be safely treated with radiosurgery in the future.
Meningiomas Meningiomas are benign tumours that grow from the lining of the brain known as the ‘meninges’. They grow slowly, also usually around 1-2 mm a year, and do not spread to other parts of the body. However, depending on where they grow, they can start to cause symptoms by pressing on the normal structures of the brain. In regions of the brain where there aren’t many important functions, they can grow very large before symptoms are experienced and a diagnosis is made. This is particularly true of tumours which
press on the frontal lobes of the brain as these cause more subtle problems, such as personality change or headaches only. Further back in the brain a tumour can cause a range of symptoms including weakness, visual or speech disturbance for example.
Treatment options for meningiomas The three main options for treating meningiomas are: 1) Conservative management with ongoing imaging.
2) Radiation treatments, including Gamma Knife radiosurgery.
3) Surgical removal or cytoreduction known as ‘debulking’.
The majority of tumours can be observed in the first instance with surveillance imaging. This period is important to determine the behaviour of the tumour and a six-monthly MRI scan is often appropriate. If new symptoms develop in the meantime, the MRI scan can be brought forward. The observational period allows time to fully characterise the tumour diagnosis so that the most appropriate treatment options are considered and decided upon. In these circumstances, if tumour growth is demonstrated at six months, a clear and quick decision on the best form of treatment can be made.
Summary Gamma Knife treatment has a long, proven history of success in treating tumours like these and it is widely considered a ‘gold standard’ of care for dealing with both benign and malignant brain tumours. It has been used as a treatment modality for small-medium sized vestibular schwannoma since the 1990s and has since become the first-line treatment approach. As an illustration, a 2014 research study by Boari et al,1 assessed the long-term clinical results following Gamma Knife treatment for a large cohort of vestibular schwannomas. It found that control of the tumour with GKRS
was achieved in 97.1% of the patients. In 82.7% of the patients, the tumour volume had decreased at the last follow-up, with a mean relative reduction of 34.1%. The rate of complications was very low, with most consisting of a transient worsening of preexisting symptoms. Patients who had vertigo, balance disorders, or facial or trigeminal impairment usually experienced complete, or at least significant symptom relief after treatment. In summary, the treatment of skull base tumours such as meningiomas and vestibular schwannomas is complex with many parallels between the two. Each patient and tumour must be assessed individually, and the range of
possible treatment options presented to allow an informed decision to be made for the particular circumstances. It’s important for patients to see an experienced multidisciplinary team that can provide all the available options so that treatment can be tailored appropriately.
Reference 1. Boari N, Bailo M, Gagliardi F, Franzin A, Gemma M, del Vecchio A, Bolognesi A, Picozzi P, Mortini P. Gamma Knife radiosurgery for vestibular schwannoma: clinical results at long-term follow-up in a series of 379 patients. J Neurosurg. 2014 Dec;121 Suppl:123-42. doi: 10.3171/2014.8.GKS141506. PMID: 25434946.
CSJ
About the author
Mr Patrick Grover is a renowned Consultant Neurosurgeon, practising privately for Amethyst Radiotherapy’s London Clinic at the Queen Square (Gamma Knife) Radiosurgery Centre, while also serving as the Cranial Neurosurgery Lead and Consultant Skull base Vascular Neurosurgeon at the National Hospital for Neurology and Neurosurgery (NHNN) for University College London Hospitals NHS Foundation Trust.
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Image provided courtesy of Elekta
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