Auditory brainstem response and magnetic resonance imaging for acoustic neuromas: costs by prevalence.
OBJECTIVE
To compare hypothetical costs for identification of acoustic tumors when using magnetic resonance imaging with gadolinium Gd 64 (MRI-(64)Gd) as a sole diagnostic test and when using auditory brainstem response (ABR) testing followed by MRI-( 64)Gd (ABR + MRI-(64)Gd) for those with positive ABR findings.


METHODS
Retrospective review of the medical records of 75 patients having surgically confirmed acoustic neuromas to categorize them into 3 subgroups relative to their risk of having a cerebellopontine angle tumor based on history, symptoms, and routine pure-tone and speech audiometric findings. Hypothetical costs associated with identification of patients with acoustic neuroma in each subgroup were calculated for MRI-(64)Gd alone and ABR + MRI-( 64)Gd. Auditory brainstem response sensitivity and specificity data for the 75 patients with acoustic neuroma and 75 patients without a tumor matched for hearing loss were applied to the hypothetical subgroups. Tumor size was considered also.


METHODS
Tertiary care center.


METHODS
Comparison of costs for MRI-(64)Gd and ABR + MRI-(64)Gd.


RESULTS
Fouteen patients with acoustic neuroma were assigned to the high-risk category (30% probability); 45 were in the intermediate-risk category (5% probability); and 16 were in the low-risk category (1% probability). Auditory brainstem response testing correctly identified 100% of the large tumors (>2.0 cm), 93% of the medium-sized tumors (1.1-2.0 cm), and 82% of the small tumors (<1.0 cm). The hypothetical costs for identifying 14 patients with acoustic neuroma among 47 patients in the high-risk category using MRI-(64)Gd would be $70,500; ABR + MRI-(64)Gd costs for the 13 patients identified by ABR would be $39,600. Hypothetically 900 patients would be tested to identify the 45 acoustic neuromas in the intermediate-risk category. Magnetic resonance imaging with (64)Gd screening would reach $1.35 million for this sample. Auditory brainstem response testing and MRI-(64)Gd would be $486,000, but 4 acoustic neuromas would be missed. For the low-risk subgroup MRI-6(4)Gd screening of 1600 patients to identify 16 acoustic neuromas would total $2.4 million; ABR + MRI-(64)Gd to identify 15 of them would be $787,500. In this sample of 75 acoustic neuromas, large tumors were more prevalent in the low-risk subgroup than in the high- or intermediate-risk subgroups.


CONCLUSIONS
Decisions regarding assessment of patients at risk for acoustic neuromas must be made on a case-by-case basis. Use of ABR + MRI-( 64)Gd allows considerable savings when patients are in the intermediate- or low-risk subgroups. New MRI and ABR testing techniques offer promise for reducing costs.
Mayo Arrowhead, Glendale, AZ 85308. robinette.martin@mayo.edu
M S
MS
Robinette
C D
CD
Bauch
W O
WO
Olsen
M J
MJ
Cevette
D002528:Cerebellar Neoplasms / Q000150:complications / Q000175:diagnosis; D002530:Cerebellopontine Angle / Q000473:pathology; D003362:Cost-Benefit Analysis; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000191:economics*; D009464:Neuroma, Acoustic / Q000150:complications / Q000175:diagnosis* / Q000191:economics*; D015995:Prevalence; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014012:Tinnitus / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology