Auditory P300 in Subjects with Chronic Cerebellar Disease

who have sustained a temporal bone fracture. 2) Be able to compare the 2 main temporal bone fracture classification systems and their prognostic value in predicting the hearing outcome. METHOD: A retrospective study was conducted of all patients diagnosed with a temporal bone fracture (TBF) between January 1, 2004 and January 1, 2009. CT scans were reviewed by 2 neuroradiologists. Patients were excluded if younger than age 18 years, died during hospitalization, had incomplete radiologic or audiometric data, or had documentation of preexisting hearing loss or use of hearing aids. Fractures were classified by both the traditional classification system (e.g., longitudinal, transverse) and the otic capsule (OC) sparing/ involving classification. Post-injury audiograms were reviewed for the type and degree of hearing loss (HL). RESULTS: Of the 1,295 patients with a diagnosis of TBF, 51 met study criteria. The mean time interval between trauma and audiometric assessment was 32 days. Conductive or mixed HL was present in 50% of longitudinal, 50% of transverse, 56% of mixed and 14% of isolated mastoid/squamosal fractures. Of the OC involving fractures, 100% had profound HL (p 0.05). Of OC sparing fractures, 12 (26%) had CHL, 17 (37%) had SNHL, 12 (26%) had MHL, and 5 (11%) had normal hearing (p 0.05). CONCLUSION: While the OC involving vs. sparing classification system better predicted patients with profound SNHL, it was less effective than the traditional classification system in predicting other hearing outcomes. We advocate the importance of using both systems when fractures do not violate the otic capsule, for better correlation of hearing outcome.