Clinical Research Of Hearing Impairment Caused By Trauma Of Ear And Mild Closed Head Injury

Objective: Trauma have became a notable problem of medicine and society which risks to human'life and health in recent years. Deafness caused by trauma as a kind of acquired deafness is often involved in a dispute. So the diagnose and appreciation appear more important. However studies about the degree and features of hearing impairment after injury and auditory dysfunction after injury without tympanic membrane perforation, temporal bone fracture and skull bone fracture were less. So, we analyzed statistic results about the degree of hearing loss after injury. The test battery comprised pure tone audiometry(PTA), acoustic immittance(AT), auditory brainstem response(ABR), 40Hz auditory event related potential(40Hz AERP), and distortion evoked otoacoustic emission(DPOAE). We analyzed the degree and features of hearing impairment caused by trauma of ear with tympanic membrane perforation and mild closed head injury without tympanic membrane perforation. We investigated the generation and influence of internal ear trauma (concussion of labyrinth) to hearing loss after injury. These would be some theoretical foundations for the clinical diagnosis and medicolegal identification.Methods: During clinical practice, 245 cases of patients in total (265 injured ears) were selected, accompanied by ear trauma with tympanic membrane perforation or mild closed head injury without tympanic membrane perforation. After injury, these patients had many main clinical manifestations: auditory dysfunction, tinnitus, tightly closed felling of ear, vertigo, nausea, vomiting and so on. 154 cases of patients (157 injured ears) were injured by trauma of ear. Among these cases, 110 cases were male.44 cases were female. Their ages were from 15 to 55 years old (average age: 29.73 years). Their visiting times were from 1 hour to more than 3 months after injury (45 ears: within 1day; 46 ears: 1~3 days; 48 ears: 3~14 days; 18 ears: more than 14 days). 91 cases of patients (108 injured ears) were injured by mild closed head injury. Among these cases, 66 cases were male. 25 cases were female. Their ages were from 15 to 55 years old (average age: 31.92 years). Their visiting times were from 4 hours to more than 1 year after injury (21 ears: within 3 days; 36 ears: 3~14 days; 19 ears: 14 days~3 months; 15 ears: more than 3 months). Detailed case histories were recorded and otolaryngological examinations were carried out, followed by a series of audiologic testing, including pure tone audiometry, acoustic immittance, ABR, and 40Hz AERP. Head or temporal bone CT scanning within 48 hours and neurology examinations showed no abnormal changes. 35 volenteers aged from 18~52 years old (25 male, 10 female, average age: 30.31 years) with normal hearing were selected as normal control. Any subject had a history without noise exposure, applying ototoxic drug, familial inheritance of deafness, and otological and nervous system disease. The malingering hearing loss had been excluded by analysing audiologic testing results. Results of different audiologic testing at different visiting time after injured had been studied to investigate hearing impairment.Statistical treatment: All data was processed by statistical software SPSS13.0 and denoted by (x_±s). Significance level was p<0.05. Statistical methods were nonparametric test, two independent-samples T test,χ2 analysis, and one-way ANOVA.Results:1 Obvious hearing impairments were observed in both groups. Average hearing thresholds were significantly higer than that of the controls. The distributional of hearing impairment in the two groups had statistical significance.2 90.45% of injured ears caused by trauma of ear had the result of PTA in agreement with ABR. The average thresholds (PTA) of these ears were no more than 60 dB for 93.66% of the injured ears. And 6.34% of these ears had severe or extremely severe hearing loss. Of these ears, 66.90% of these ears were conductive deafness, while 23.24% of these ears were mixed deafness or sensorineural deafness. Threshold values at different frequencies of PTA were no more than 25 dB for 9.86% of these ears. Average threshold of PTA, auditory threshold of ABR and 40Hz AERP had statistical significance between visiting group at different time and normal control. The average threshold of the last visiting group was minimum, which had no statistically significance. There was statistical significance among different frequencies for the first group especially at 0.125 kHz. Other visiting groups had no statistical significance at different frequencies. Compare the every latency period of wave and interpeak latency of injury group with the normal control group. Every latency period of wave had extended obviously. There were significant deviations, but interpeak latency ofⅠ-Ⅴwave.3 84.26% of injured ears caused by mild closed head injury had the result of PTA in agreement with ABR. The average thresholds (PTA) of these ears were no more than 60 dB for 70.33% of the injured ears. And 29.67% of these ears had severe or extremely severe hearing loss. Of these ears, 74.72% of these ears were sensorineural deafness, while 25.28% of these ears were mixed deafness or conductive deafness. Average threshold of PTA, auditory threshold of ABR and 40Hz AERP had statistical significance between visiting group at different time and normal control. The average threshold of the last visiting group was minimum, which had no statistical significance. There was statistical significance among different frequencies for visiting group except the last group, especially at 4 kHz and 8 kHz. Hearing impairment at 4 kHz was the most severe for DPOAE. The positivity rate of ABR and 40Hz AERP were 88.89% and 98.15%, respectively. The threshold of ABR was higher than that of 40Hz AERP. Compare the every latency period of wave and interpeak latency of injury group with the normal control group. Every latency period of wave had extended obviously. There were significant deviations, but interpeak latency ofⅠ-Ⅲwave. 18 cases were conducted follow-up and further consultation at 1, 3, and 6 months after injury. The audibility thresholds of PTA were improved, especially at low frequency (0.25 kHz and 0.5 kHz). The threshold of 40Hz AERP was obviously lower than that of ABR.Conclusions: 1 Most of the patients suffering from ear trauma with tympanic membrane perforation had slight to mid-range conduction deafness. Results of PTA showed that the hearing loss at 0.125 kHz was most obvious and serious. The average thresholds of PTA, ABR, and 40Hz AERP of the last visiting group (>14days group) were minimum, which had no statistical significance. Hearing loss for a part of injured ears was serious and would cause mixed deafness or sensorineural deafness. Combining with ABR, 40Hz AERP, and clinical symptom, we would consider that there was injury not only in the middle ear, but also in the inner ear in some degree.2 Most of the patients suffering mild closed head injury had slight to mid-range sensorineural hearing loss, while merely minority had severe hearing loss or mixed hearing loss. There would be functioning impairment of brainstem. Hearing loss was obviously detected in the high-frequency range (especially at 4 kHz) combining with different hearing tests. Auditory function was observed to be improved after 6 months since injury, especially at low frequency range (0.25 kHz and 0.5 kHz). Combining with clinical symptom and auxiliary examination, labyrinth concussion of the inner ear was considered to play an important for the injured mechanism of inner ear.3 Accurate evaluation and reasonable identification of the degree of hearing loss after injury need detailed case histories and clinical, radiological, and audiological assessments. On the one hand, clinician or appraiser should understand the features of different audiology tests to complete each other on insufficiency of audiology detection. On the other hand, we should grasp the mental status of subjects and get their cooperation. Besides, we should take the rule of variations of hearing loss into consideration and grasp reasonable identification time. Finally, we should make an objective and reasonable clinical diagnosis or medicolegal identification.