Development of an Evidence Based Referral Protocol for Early Diagnosis of Vestibular Schwannomas

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2008-09-03

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The purpose of this investigation was to identify the presenting symptoms and testing outcomes that were most suggestive of a potential vestibular schwannoma and to propose an audiological referral protocol for MRIs. To that end, a retrospective chart review was conducted to examine radiologic, audiometric, and case history information from patients at Walter Reed Army Medical Center who were referred to the Department of Radiology to rule out retrocochlear pathology. Charts of 628 patients were reviewed from their electronic medical records, although the final patient sample was 328 patients who had complete audiologic data. Analyses were conducted to compare the unaffected and affected ears of the positive MRI group to the better and poorer ears of the negative MRI group. Results were significant between the affected ear of the positive group and the poorer ear of the negative group for pure tone thresholds, speech discrimination scores, and acoustic reflex thresholds. Significant differences between the groups were not generally seen for the comparison of the unaffected ear to the better ear, with the exception of acoustic reflex thresholds. The interaural difference between ears was significant between the two groups for pure tone thresholds and speech discrimination scores; however, the difference was not significant for acoustic reflex thresholds. For all significant differences between the groups, the positive MRI group evidenced poorer audiological results. Additionally, three symptoms/outcomes that led to the patients' referral were significantly different between the two groups: unilateral tinnitus, asymmetrical word recognition, and positive rollover in speech recognition scores. Logistic regression was applied to the audiological tests and symptoms to determine the most predictive set of variables that differentiated between the patients with a positive and negative MRI. The most predictive model yielded a sensitivity of 81.25% and a specificity of 82.59% when applied to the current patient sample. The audiological profile identified may be useful for clinicians in deciding whether their patient should be referred for an MRI to rule out the presence of a vestibular schwannoma.

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