History and symptoms

The initial investigation should begin with a comprehensive history, including not only auditory symptomatology but also a proper description of the mechanism of injury. It is important to determine the nature of the head trauma, whether it was caused by direct impact, sudden or rapid acceleration and deceleration, penetrating injury or blast injury, and whether there have been prior episodes of head trauma. Additionally, prior otologic symptoms, general medical and surgical history, and any other relevant information that may help to elucidate the diagnosis of the auditory dysfunction should be inquired.

In terms of symptomatology, complaints of patients with labyrinthine concussion are nonspecific and may include new onset of unilateral or bilateral hearing loss, aural fullness, tinnitus, and hyperacusis following head trauma. These symptoms might also occur in conjunction with vestibular dysfunction. Additionally, hearing loss related to labyrinthine concussion may not be permanent as some level of recovery has been already reported in prior clinical and experimental studies. .

Physical examination and evaluation

The physical examination generally includes otoscopy, which may be useful to assess other potential causes of hearing loss such as cerumen impaction, middle ear effusion, or tympanic membrane perforation. Additionally, a fistula test may be performed in the setting of vestibular symptomatology, as traumatic perilymphatic fistula should be considered in the differential diagnosis. Tunning forks can be also used for the assessment of hearing loss, in which a Weber test in a patient with unilateral sensorineural hearing loss will lateralize sound toward the unaffected side, and Rinne test should be positive unless significant hearing loss to the tested ear exists.

Objective audiometric testing may demonstrate variable severity of sensorineural hearing loss depending on the extent of neurosensory injury. Clinical and experimental studies have suggested that hearing loss due to labyrinthine concussion is typically more severe in high frequencies, in particular the range from 3 to 8 KHz, resembling an acoustic trauma. ^{, ,} This finding is thought to be a result from perilymph and endolymph vibrating waves generated by the concussive trauma associated to an inherent fragility in the upper region of the basal turn, or to physical properties of the impulse.

Radiologic assessment

In the evaluation of a patient with sensorineural hearing loss following head trauma, a high-resolution computed tomography (HRCT) is the initial imaging modality recommended to check for fractures through the temporal bone involving the otic capsule, or pneumolabyrinth that may suggest a perilymphatic fistula. In the setting of a negative HRCT study, diagnosis of labyrinthine concussion is more likely. A complementary magnetic resonance imaging (MRI) may be also obtained to look for intralabyrinthine hemorrhage and cranial nerves integrity. If intralabyrinthine bleeding occurs as a result of concussion, high signal intensity in the inner ear may be seen on T1-weighted and fluid-attenuated inversion-recovery (FLAIR) imaging. ^,