Presently, gadolinium enhanced magnetic resonance imaging is the ‘gold standard’ for investigating acoustic neuroma. There are often ‘incidental’ findings that may or may not be significant. In this study of 109 scans, the authors noted an uptake of 0.9% for acoustic neuroma and there were seven patients with vascular loops, an incidence of 6.4%. Twenty-eight scans (25.7%) demonstrated old ischaemic and degenerative changes and nine patients (8.3%) had paranasal sinus disease. Interesting incidental findings were a deep lobe parotid tumour, an empty sella turcica and demyelinating changes. The MRI modality continues to have a low uptake rate, the best reported being 4%. It is contended that patients with vascular loops touching the VIIIth nerve should be referred to a neurosurgeon. It is also important to inform the patient’s general practitioners of ischaemic white matter changes because these patients may have an increased risk of stroke and dementia. One of the patients had demyelinating features in absence of any clinical findings, which comprises ‘radiologically isolated syndrome’, a term used by Okuda in 2009. Studies have shown that in 50% of these patients without clinical symptoms, the demyelination progresses radiologically with time and 30% develop multiple sclerosis. Referral should therefore be made to a neurologist. When considering cost effectiveness of MRI, the limitations of contrast enhanced CT and ABR should be put in the right perspective. Also, pathologies involving the higher auditory pathways should be duly considered. The need for formulating a local algorithm in conjunction with radiology colleagues for managing incidental findings has been stated.
Associated findings in MRI used for detecting acoustic neuroma
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