Extra- and intra-axial brain stem auditory disorders.

Auditory symptoms of brain stem disorder depend on the nature of the lesion. This study compared auditory test results in 28 patients with extra-axial, 11 patients with intra-axial, and 6 patients with combined extra-axial and intra-axial brain stem disorders. Patients with extra-axial lesions usually demonstrated (1) sensitivity loss, (2) marked adaptation on Békésy audiometry, (3) impairment in PBmax scores, and (4) auditory symptoms on the ear ipsilateral to the radiographic abnormality. Patients with intra-axial brain stem lesions usually showed (1) slight, if any, sensitivity loss, (2) normal Békésy audiograms, (3) relatively good PBmax scores, and (4) suditory symptoms on both ears or on the ear contralateral to the radiographic disorders. In the patients with combined extra-axial and intra-axial disorders, auditory findings varied in relation to the extent of extra-axial involvement.