Management of Vestibular Schwannoma (Acoustic Neuroma) Research Study

Management of Vestibular Schwannomas and other Skull Base Tumours

The department has been running a prospective study of the management of Vestibular Schwannomas and other skull base tumours over the last 10 years. The following is an outline of the study. If you would like further information regarding the study please contact Dr Sean Flanagan, A/Prof Nigel Biggs or Dr Phillip Chang.

Background

A vestibular schwannoma is a benign tumour arising on the eight cranial nerve, the nerve of hearing and balance. Whilst this tumour is benign, its close proximity to vital neural structures can lead to serious complications, including death. The commonest presenting symptom is one of hearing loss, but disturbances in balance, as well as other sensory abnormalities are not uncommon. Diagnosis is usually confirmed on MRI or CT scan.

Vestibular schwannomas represent 80% of all CPA tumours. The other pathologies found here include meningiomas, facial schwannomas, epidermoids, lipomas, haemangiomas and metastatic lesions.
Traditionally the management of all these tumours was with intra-cranial micro-surgery. Current management options now include micro-surgery, stereotactic and conservative management, which involves serial imaging and clinical reassessment.1-3 Some patients then progress onto interventional therapy if they fail conservative management either related to progressive growth or progression of symptoms. A small proportion of patients will require revision surgery, surgery following radiotherapy and radiotherapy following surgery. Difficult management decisions surround the timing of intervention, the attempt to preserve function including hearing, and the patients co-morbid state.

The aim of this study is to accumulate a balanced set of data that will allow us to determine the optimal management paradigm.

Standard outcome measures have included hearing, facial function, vestibular or balance function, rates of CSF (brain fluid) leak and mortality figures. 4-7 8,9. In recent years there has been an increasing move toward assessing more holistic outcomes of management. This predominantly involves the use of well validated patient health surveys, or Quality of Life Surveys. 6,10-19.20-23
Up until this point in time our data base has collected information regarding patient demographics, tumour site, size, and operative details.
The aim of the study is to analyse outcomes of management and the use of quality of life questionnaires will provide us with additional, otherwise difficult to quantify consequences of the management and natural history of these tumours.

Participant eligibility

There are four non-randomised patient cohorts currently recognised.

1. Firstly the group of patients with vestibular schwannoma who following diagnosis were treated with surgery or radiotherapy.

2. The second group are those who were, and continue to be treated by observation.

3. The third group are those who during their period of conservative management failed this modality, necessitating surgical or radiotherapeutic intervention.

4. Those patients requiring additional treatment following surgery or radiotherapeutic treatment.

Recruitment and consent process

Patients diagnosed with a vestibular schwannomas (or other skull base tumours or lesions) are offered the opportunity of enrolling in the study. The management of vestibular schwannomas is a tertiary referral condition, and as such a significant number of patients have initially been diagnosed by another physician and then referred to one of the members of the St Vincent’s Department of Otolaryngology, Head and Neck and Skull Base Surgery

Eligible patients will be introduced to the study and given information regarding the study at their clinic appointment. The information provided to patients regarding the study will include; a cover letter with a Participant Information Sheet and Consent Form, the 5 study questionnaires and a symptom ‘summary sheet’ to complete.

Methodology

The data collected is patient name, date of birth, presenting symptoms and date of onset. This specifically includes: hearing calculated using a pure tone average and speech discrimination score in both ears, examination of vestibular function, facial nerve function reported using the House-Brackman scale, and the presence or otherwise of tinnitus, trigeminal symptoms and evidence of raised intracranial pressure. The initial doctor seen is recorded, and consequently the doctor overseeing their treatment if different. The size of the tumour as reported on an MRI scan, divided into its intracanalicular and cerebellopontine angle components is noted. Standard non-invasive vestibular tests are also employed. This includes Video Head Impulse Test or “VHIT”, vestibular evoked myogenic potential tests OVEMP and CVEMP, videooculography VOG and vestibulospinal tests of the balance pathways24-26. If clinically indicated caloric tests of vestibular function will be performed and recorded.

In terms of intra-operative data: the hospital at which surgery is performed, primary and secondary surgeon, approach used, total time, facial nerve function in recovery (House Brackman scale27), time spent in ICU, time in hospital, presence of post-operative complications. Follow-up data includes changes in the parameters already recorded.

From a radiotherapy perspective, the modality used, total dose given, number of fractions and presence of post-treatment complications. Follow-up data includes changes in the parameters already recorded.
5 quality of life instruments are part of an attempt to obtain global data of how a patient responds to the diagnosis and ongoing management of their tumour.
Historically the most widely used instruments have been the Glasgow Benefit Index GBI, and the SF-36, in addition to a number of self designed questionnaires. The GBI is purely designed as a post-interventional tool11,18 so is not appropriate for our study. The SF-36 is the other commonly used tool, but in previous studies two main weaknesses have developed. The first is the single administration, usually at an arbitrary period following intervention. For a condition with a long natural history, and especially in those patients managed conservatively, the change in QOL is far more important to measure. The second factor is it’s generality. The addition of two specific QOL instruments we propose will allow us to isolate the most important factors influencing the overall QOL.
The QOL instruments we are using are firstly the SF-36, a well validated general quality of life survey. The remaining instruments are the Hearing Handicap Inventory 14,28 , the Dizziness Handicap Inventory 29,30 and Tinnitus Handicap Inventory,31 all specific tools with close relevance to the disease process being studied. We also propose to use the PANQOL, (Penn State University Acoustic Neuroma Quality of life Survey) which is a disease specific validated survey. 21,32 Each questionnaire is expected to take less than five minutes to complete.
The timing of administration of these questionnaires is important in order to minimise bias. The questionnaires will be administered by direct post, in the first instance one month following initial diagnosis of a vestibular schwannoma. Follow-up administrations will on average each twelve months, independent to the treatment undergone. Previous use of the HHI and DHI has been isolated to patients treated with surgery, with an initial pre-operative assessment, followed by 3 or 6 months post-operatively. There have been no reports of their use in those managed conservatively. Similarly the SF-36 has only been used (in this setting) as a single administration. 17,19 .

Collection and storage of tumour samples

If patients should ever require surgery for their schwannoma or other skull base lesion, details regarding the type of surgery, how long the surgery took and their post operative course will also be collected as well as details about exact nature of schwannoma that was removed. Tumour samples will then be kept in the department of anatomical pathology and may be used for future research. Any future research conducted on tumour samples collected for this project will require separate Human Research Ethics Approval.

References

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