MRI surveilance protocol for vestibular schwannoma in South africa
South Africa has no universally accepted surveillance protocol for sporadic (non-NF2) vestibular schwannoma in the wait-and-scan (observation) group of patients (1,2,3). Patients must be informed about the frequency of follow-up magnetic resonance imaging (MRI) appointments to prevent confusion, misunderstanding, and anxiety and to safeguard the patient against the growth of the vestibular schwannoma that may impact their life (10).
The protocol determining MRI frequency should consider patient safety and cost, as using gadolinium contrast agents in MRI scans can pose potential long-term health risks (4, 8). The unique economic and healthcare challenges in South Africa may require a tailored approach to MRI surveillance protocols, making it necessary to carefully select from the three internationally published protocols (5,6,7). After reviewing the available options, we recommend adopting a specific magnetic resonance surveillance protocol for vestibular schwannoma in South Africa.
An intrameatal tumour is confined to the internal aduditory canal (meatus). An extrameatal tumour is a intrameatal tumour that extends beyond the the internal auditory meatus or a purely extrameatal tumour (9). Growth is defined as 3 mm or more in any dimension (7).
We have decided that the protocol suggested by Shapey and co-workers of the King’s College Hospital NHS Foundation Trust, UK, is the most appropriate for South Africa (5).
A few basic points on MRI requests
- Follow the surveillance protocol meticulously.
- Inform the rooms of Dr Hofmeyr if there is a problem with obtaining an MRI.
- If any new or altered symptoms arise in the follow-up period, contact Dr Hofmeyr’s rooms or visit the general practitioner.
- If possible, utilise the same imaging facility.
- Ask the radiologist to transfer the images to DR Hofmeyr’s rooms or the facility of the referring physician and supply a disc with the images to the patient.
- Gadolinium must be administered unless otherwise specified.
- The radiologist should report possible growth, looking at all the previous MRI images.
- Measurements in mm should be given for length, width, and height.
- The radiologist should measure the intrameatal and extrameatal components separately and document them as such.
- According to international standards, growth is defined as an increase in size of 3 mm or more in any of the three measurements or more than 20% in the volume , of the extrameatal component.
- Comparative measurements for previous MRIs should be documented, as well as a comment on how the latest MRI compare with the first MRI.
- The radiologist should comment on any cystic changes in the tumour and compare it with the previous MRI.