Congenital malformations of the inner ear: histologic findings in five temporal bones.

The histopathologic findings in five temporal bones from three patients with congenital malformation of the inner ear are described. The external contour of the cochlea was deformed in two temporal bones, while the internal architecture was abnormal in all five temporal bones. Intracochlear abnormalities included defects in the interscalar septum, deficiencies in the modiolus, and a paucity of neural elements. Spiral ganglion cell populations varied, but were substantially diminished in all five temporal bones. Enlargement of the vestibule and semicircular canals (lateral and posterior) was seen in two temporal bones. A large vestibular aqueduct and saccular hydrops were found in one temporal bone each. An attempt was made to relate the histologic patterns of deformity to the proposed clinical classification of inner ear malformations. Radiographic abnormality of the cochlea would have been detectable in two bones (incomplete partition pattern), while two other bones would have appeared as vestibule-semicircular canal syndromes. One bone would have been radiographically normal.