Otopathologic Changes in the Inner Ear Following Head Injury Without Temporal Bone Fracture

Background: Auditory and vestibular dysfunction following temporal bone (TB) fracture may result from direct transection of the middle and inner ear. The pathophysiology of hearing loss due to head injury without TB fracture, however, is not well understood and few reports describe otopathologic findings of such cases.

Objective: Herein, we investigate the otopathologic findings in patients who sustained a head injury without evidence of a TB fracture.

Methods: Subjects from the National Temporal Bone Registry with a history of head injury without TB fractures were included and analyzed by light microscopy. The peripheral auditory pathway was evaluated to determine counts of spiral ganglion neurons (SGN), hair cells (HC), and pillar cells, health of stria vascularis and the presence or absence of endolymphatic hydrops. The vestibular system was evaluated to determine counts of Scarpa ganglion cells (ScGC) and vestibular hair cells and presence or absence of vestibular hydrops and obstruction of the endolymphatic duct. Specimens were compared to historical age-matched controls.

Results: All cases (n=6 TB) showed pathologic changes of the inner ear. TBs showed an average SGN count that was 65%(range: 43%-84%) of that in controls. Two of the six (33%) cases had severe loss of HC and pillar cells along the length of the cochlea, and four of the six (67%) cases demonstrated moderate-severe loss at the basal turns of the cochleae. In the vestibular system, the average ScGC count was 46%(range 44-60%) of that in historical age-matched controls, and three of six (50%) cases showed degeneration of HC and/or dendrites of vestibular-end organs. Additional findings include cochlear and/or vestibular hydrops in three of the six (50%)TBs.

Conclusions: Patients with a history of head injury without TB fracture demonstrate inner ear pathology. Findings may shed light on mechanisms on under-recognized auditory and vestibular pathology.