Dr Robert Pu
House Officer, Southern DHB, Dunedin, NZ
Robert is a PGY3 House Officer at Dunedin Hospital, New Zealand.
Screening for Vestibular Schwannoma – Audit of Southern District Health Board (SDHB) MRI Activity
This review of SDHB Vestibular Schwannoma (VS) screening, focussed on audiometry to assess appropriateness of MRI requests. The aim being to optimise case selection and reduce unnecessary imaging.
A retrospective audit of MRIs for possible VS in patients with asymmetric sensorineural hearing loss (SNHL) at Dunedin and Southland hospital from Jan 2014 – Apr 2019. The VS screening guidelines against which this data was assessed are currently used in NZ or recommended by comparative analysis and expert opinion. VS detection rate, sensitivity and specificity for each was calculated.
1280 patients had an MRI. 613 were excluded: inaccessible audiogram (509), known VS (78), or other indication, such as cholesteatoma, Bells palsy, headache (26). Of the 667 included, indications were: asymmetric SNHL (586), unilateral tinnitus (42), other indications (39). All VS detected (22) were in the asymmetric SNHL group.
Frequencies 0.5/1/2/4/8kHz were more reliably recorded. Frequencies 0.25/3/6kHz were not reliably recorded with paired measurements. Consequently, there were only sufficient numbers to reliably assess guidelines using frequencies 0.5/1/2/4/8kHz. VS detection rate ranged between 3.8-7.5%. Many audiograms (23.6-54.8%) did not conform to guidelines. Sensitivity ranged from 0.81-1.00, and specificity from 0.24-0.56.
Not all patients scanned meet current guidelines. The NZSOHNS guideline may not be the optimal choice. The optimal guideline for SDHB is probably ≥10dB between ears averaging 1/2/4/8kHz which had a sensitivity of 1.00, and specificity of 0.24 with a detection rate of 4.8%.