Statistical observations on hearing and equilibrium disturbance were made in 245 patients who had suffered from head and neck injuries but no temporal bone fractures, and complained of vertigo. The results were as follows; 1. Percentage of the cases of objective hearing loss on audiograms (58%) was higher than those complained of subjective hearing loss (31%). 2. Bilateral and contralateral hearing losses to the injured side were much more frequently observed than ipsilateral ones. 3. More than half of the cases showed a hearing loss of high tones on audiogram. C5-dip and flat pattern were also observed in the rest of the cases. 4. In the cases with an objective hearing loss, abnormal findings in equilibrium tests were more frequently found than in the cases without hearing loss. 5. In the cases suspected of central disturbance in equilibrium examinations, severer hearing loss and higher percentage of bilateral hearing loss and high tone loss were observed than in that of peripheral disturbance.
We made electrocochleographical examinations on 11 cases of hearing loss due to head trauma. These cases were tested with the trans-tympanic technique using 0.5, 1, 2, 4, 8kHz tone pip as acoustic stimuli. Electrocochleographical audiograms consisted of 0.5μV level of CM and AP responses were obtained. The AP wave form was also investigated, and an aural reflex was tested. Temporal summating effect of conditioned tone, which reduced CM amplitude evoked by 0.5kHz tone pip (test tone), by the aural reflex, was observed. Cases of brain stem lesion revealed an abnormal pattern of temporal summating envelope. We reviewed 11 cases of deafness caused by head trauma, and dissociation of CM and AP responses observed on the electrocochleographical audiograms, abnormal AP wave form and abnormal pattern of the temporal summating envelope by the aural reflex, and the auditory lesion of these cases were discussed. The results were as follows: 1) Labyrinthine damage... 4 cases 2) First auditory neuron disorder... 4 cases 3) Brain stem lesion... 3 cases
Relation of pure tone auditory threshold to BSR and AP threshold was studied in 72 cases of head and neck injury with auditory disturbance. A difinite corelation was found between pure tone hearing threshold and BSR threshold in most of patients of head and neck injury. Amplitude of BSR delivered from the side of the patient's head received craniotomy decreased in 4 cases of 7 cases. There were significant differences on the amplitude of BSR waves and the appearance of the Ist to V th waves between the right and left ear. Topographic recording of BSR was attempted in the cases of central nervous disorder. BSR was topographically delivered from 10-16 points on the scalp according to the international 10-20 electrodes system. On the topographic recording of the BSR, there was a clear difference on the ampulitude of IV-V waves of BSR between cases of central nervous disorder and normal hearing adults. Measurement of BSR and AP on the posttraumatic syndrome will provide a worthwhile information for the diagnosis of hearing disturbance and central nervous disorder.
A common type of head trauma in man was simulated in guinea pigs by delivering them a head blow with the pendulum device. The effects of the direction and intensity of the head blow and the effects of the lapse of time after the head blow on the development of hearing loss were studied. The electrical responses from the inferior collicurus and from the round window to acoustic stimuli were measured. The elevation in threshold of the evoked responses from the inferior colliculus in the presence of normal cochlear potentials in the animals suggests that the site of lesions is central to the cochlea. Biomechanics of the development of damages in the central auditory pathway secondary to a head blow was discussed further.
Relation between head injury and acoustic lesion was analyzed systematically in 1, 447 head injury cases which were examined by extensive hearing and tinnitus tests. In this report, the relation between the existence and extent of bleeding from the ear, bleeding from the nose, a bloody spinal fluid, unconsciousness, abnormal tympanic membrane and the nature and range of tinnitus was studied. And the following results were obtained. In general, the continuous and high pitched tinnitus existed in whom the extent of head injury was thought to be slight showing no bleeding from the ear, no bleeding from the nose, no bloody spinal fluid, no unconsciousness and no abnormal tympanic membrane. Therefore the results opposed to a medical common sense.
A battery of audiological tests for sensori-neural disorders was performed on 235 cases with posttraumatic complaints of the head and neck. The type IV of Békésy audiometry was found most frequently in patients who were unconscious soon after the accident. A poor speech discrimination in spite of normal hearing for pure tone was found in some cases who had a bruise on the right temporal region. By analyzing the data from the subjects on whom re-examination was performed, it was known that retrocochlear disorders were often found in patients who revealed a higher pure tone hearing threshold in the second test than the first audiometry. Many cases with unilateral tinnitus showed positive recruitment. Signs of the retrocóchlear leison were also commonly found in patients with unilateral tinnitus rather than in those with bilateral tinnitus.
The Audiometric findings and the mechanism of traumatic injury due to head trauma to the hearing organ are described and discussed exclusively in cases in whom the locations of head injury were far from the hearing organ. Interruption of the ossicular chain was found by impedence audiometry in cases of head collision happened in a slow speed, for example falling on road. Hair cell damage was found more severely in the ear opposite to head trauma in which collision was made by a small heavy piece with a high speed than in the other ear. This mechanism is here called “contre coup” and discussed dynamically. Central deafness due to the temporal lesion is detected in the ear opposite to the side of the head trauma with a temporal bone fracture and brain damage.