Pathology of temporal bones following head injuries: the macro and microscopic effects on the inner ear

Abstract

A study on 41 human temporal bones involved in fatal trauma to the head was conducted over a 7 year period. Six normal bones were used as controls; twenty two were involved in a motor vehicle accident and thirteen were involved in a fall from a height. All temporal bones were subjected to CT scan and later were micro sliced in 2 mm slices. All micro slices had plain roentgenograms, flat-bed scanning on both sides and were observed under the dissecting microscope for gross pathology. The effects of head injury in relation to the three regions of the ear, namely the outer, middle and inner ear and the effects of fractures and other pathologies on the temporal bone structures were studied. It was sometimes possible to identify lesions not detected by roentgenograms and flat-bed scanning only by dissecting microscopy. Bone densitometry studies were conducted on all the temporal bone microslices. The results were expressed as Hounsfield units. It was shown that the otic capsule had a high Hounsfield value, was not age or gender-related and offered good protection to the auditory and vestibular organs. From the study it was shown that most fractures were of the oblique and mixed types and not true longitudinal or transverse fractures. CT scans by themselves are only sufficient to detect gross fractures of the temporal bones. Gross observations showed intact bones but further examination especially after microscopic examination of the micro slices showed fractures not detected by routine roentgenograms. We have described a new plane of sectioning which enhances our understanding and which is more clinically relevant in this new era of multi-planar scanning. In the second part of the study the findings of a study of twenty-four cases that were admitted to ITV and were investigated audiologically and followed up over a four year period are presented. It was found that hearing loss became permanent after the first year post trauma while tinnitus, vestibular and facial complications improved over time.