Temporal bone studies in anencephaly.

The principal anatomical and histological features of the temporal bones of three anencephalics are described, one a twin-headed monster, with four temporal bones. These may be summarized as follows: Malformation of ossicles. Mondini type malformation of the cochlea. Occasionally cochlear hydrops or collapse of Reissner's membrane, following apparently on its rupture. Distension of the vestibular labyrinth and oedema of the perilymphatic spaces and membranes. Rupture of the saccular wall with 'sealing off' and repair of the tears and gaps by coagulated lymph material. Fibrous obliteration of the internal auditory meatus containing scanty nerves and neurones. Geniculate ganglion and facial nerve present and appear to be normally developed. The neuro-epithelial structures were well developed despite the total or partial absence of the central nervous system. The temporal bones of anencephalics offer an excellent source of comparative anatomy for the study of the pathology of Menière's disease and sensorineural lesions.