Ear injuries sustained by British service personnel subjected to blast trauma

[Blast and explosion traumas-effects on the middle and inner ear based on the example of Bundeswehr foreign missions]

Despite all protective measures, blast and explosion traumas are a frequent pattern of injury in Bundeswehr missions abroad. Due to body protection measures, head injuries, particularly of the ears, are higher in number compared to injuries in other regions of the body. Perforations of the tympanic membrane are the most frequent lesions of the middle ear, acute sensorineural hearing loss is the most frequent lesion of the inner ear, often accompanied by tinnitus and dizziness. With a high spontaneous recovery rate, prompt specialist care for these injuries is provided according to medical standards comparable to those in the home country.

Long-Term Sensorineural Hearing Loss in Patients With Blast-Induced Tympanic Membrane Perforations

OBJECTIVE

To describe characteristics of sensorineural hearing loss (SNHL) in patients with blast-induced tympanic membrane (TM) perforations that required surgery.

DESIGN

A retrospective review of hearing outcomes in those who had tympanoplasty for combat blast-induced TM perforations. These were sequential cases from one military otolaryngologist from 2007 to 2012. A total of 87 patients were reviewed, and of those, 49 who had appropriate preinjury, preoperative, and long-term audiograms were included. Those with pre-existing hearing loss were excluded. Preinjury audiograms were used to assess how sensorineural thresholds changed in the ruptured ears, and in the contralateral ear in those with unilateral perforations.

RESULTS

The mean time from injury to the final postoperative audiogram was 522 days. In the ears with TM perforations, 70% had SNHLs of 10 dB or less (by bone conduction pure tone averages). Meanwhile, approximately 8% had threshold shifts >30 dB, averaging 50 dB. The strongest predictor of severe or profound hearing loss was ossicular discontinuity. Thresholds also correlated with bilateral injury and perforation size. In those with unilateral perforations, the SNHL was almost always larger on the side with the perforation. Those with SNHL often had a low-to-mid frequency threshold shift and, in general, audiograms that were flatter across frequencies than those of a typical population of military personnel with similar levels of overall hearing loss.

CONCLUSIONS

There is a bimodal distribution of hearing loss in those who experience a blast exposure severe enough to perforate at least one TM. Most ears recover close to their preinjury thresholds, but a minority experience much larger sensorineural threshold shifts. Blast exposed ears also tend to have a flatter audiogram than most service members with similar levels of hearing loss.

Management of tympanic membrane retractions: a systematic review

Importance

Tympanic membrane retraction (TMR) is a relatively common otological finding. However, no consensus on its management exists. We are looking especially for a treatment strategy in the military population who are unable to attend frequent follow-up visits, and who experience relatively more barotrauma at great heights and depths and easily suffer from otitis externa from less hygienic circumstances.

Objective

To assess and summarize the available evidence for the effectiveness of surgical interventions and watchful waiting policy in patients with a tympanic membrane retraction.

Evidence review

The protocol for this systematic review was published at Prospero (207859). PubMed, Embase, and the Cochrane Database of Systematic Reviews were systematically searched from inception up to September 2020 for published and unpublished studies. We included randomized trials and observational studies that investigated surgical interventions (tympanoplasty, ventilation tube insertion) and wait-and-see policy. The primary outcomes of this study were clinical remission of the tympanic membrane retraction, tympanic membrane perforations and cholesteatoma development.

Findings

In total, 27 studies were included, consisting of 1566 patients with TMRs. We included data from 2 randomized controlled trials (76 patients) and 25 observational studies (1490 patients). Seven studies (329 patients) investigated excision of the TMR with and without ventilation tube placement, 3 studies (207 patients) investigated the wait-and-see policy and 17 studies (1030 patients) investigated tympanoplasty for the treatment of TMRs.

Conclusions and relevance

This study provides all the studies that have been published on the surgical management and wait-and-policy for tympanic membrane retractions. No high level of evidence comparative studies has been performed. The evidence for the management of tympanic membrane retractions is heterogenous and depends on many factors such as the patient population, location and severity of the TMR and presence of other ear pathologies (e.g., perforation, risk of cholesteatoma and serous otitis media).

Supplementary Information

The online version contains supplementary material available at 10.1007/s00405-021-06719-3.

Dual-laser measurement of human stapes footplate motion under blast exposure

Hearing damage is one of the most frequently observed injuries in Service members and Veterans even though hearing protection devices (HPDs, e.g. earplugs) have been implemented to prevent blast-induced hearing loss. However, the formation and prevention mechanism of the blast-induced hearing damage remains unclear due to the difficulty for conducting biomechanical measurements in ears during blast exposure. Recently, an approach reported by Jiang et al. (2019) used two laser Doppler vibrometers (LDVs) to measure the motion of the tympanic membrane (TM) in human temporal bones during blast exposure. Using the dual laser setup, we further developed the technology to detect the movement of the stapes footplate (SFP) in ears with and without HPDs while under blast exposure. Eight fresh human cadaveric temporal bones (TBs) were involved in this study. The TB was mounted in a "head block" after performing a facial recess surgery to access the SFP, and a pressure sensor was inserted near the TM in the ear canal to measure the pressure reaching the TM (P1). The TB was exposed to a blast overpressure measuring around 7 psi or 48 kPa at the entrance of the ear canal (P0). Two LDVs were used to measure the vibrations of the SFP and TB (as a reference). The exact motion of the SFP was determined by subtracting the TB motion from the SFP data. Results included a measured peak-to-peak SFP displacement of 68.7 ± 31.6 μm (mean ± SD) from all eight TBs without HPDs. In five of the TBs, the insertion of a foam earplug reduced the SFP displacement from 48.3 ± 6.3 μm to 21.8 ± 10.4 μm. The time-frequency analysis of the SFP velocity signals indicated that most of the energy spectrum was concentrated at frequencies below 4 kHz within the first 2 ms after blast and the energy was reduced after the insertion of HPDs. This study describes a new methodology to quantitatively characterize the response of the middle ear and the energy entering the cochlea during blast exposure. The experimental data are critical for determining the injury of the peripheral auditory system and elucidating the damage formation and prevention mechanism in an ear exposed to blast.

Force and Sound Pressure Sensors Used for Modeling the Impact of the Firearm with a Suppressor

In this paper, a mathematical model for projectiles shooting in any direction based on sensors distributed stereoscopically is put forward. It is based on the characteristics of a shock wave around a supersonic projectile and acoustical localization. Wave equations for an acoustic monopole point source of a directed effect used for physical interpretation of pressure as an acoustic phenomenon. Simulation and measurements of novel versatile mechanical and acoustical damping system (silencer), which has both a muzzle break and silencer properties studied in this paper. The use of the proposed damping system can have great influence on the acoustic pressure field intensity from the shooter. A silencer regarded as an acoustic transducer and multi-holes waveguide with a chamber. Wave equations for an acoustic monopole point source of a directed effect used for the physical interpretation of pressure as an acoustic phenomenon. The numerical simulation results of the silencer with different configurations presented allow trends to be established. A measurement chain was used to compare the simulation results with the experimental ones. The modeling and experimental results showed an increase in silencer chamber volume results in a reduction of recorded pressure within the silencer chamber.

Blast-Induced Cholesteatomas After Spontaneous Tympanic Membrane Healing

OBJECTIVES

To characterize blast-induced cholesteatomas (BIC) in terms of symptoms, presentation, and location within the middle ear cleft (MEC).

DESIGN

A search for all English language articles in "MEDLINE" via "PubMed" and "Google Scholar" was conducted.

RESULTS

A total of 67 ears with BIC were included. Fifty-eight ears in which the traumatic perforation failed to spontaneously close were excluded, leaving seven case reports (eight patients, nine ears) for statistical analysis. Time between blast exposure to spontaneous tympanic membrane (TM) closure was 16 days to 10 months. Time between blast exposure and cholesteatoma diagnosis was 5 months to 4 years. The cholesteatomas were diagnosed due to symptoms in two ears, as asymptomatic finding on physical examination in one ear and as asymptomatic finding in axial imaging in three ears.

CONCLUSIONS

BICs can develop behind intact tympanic membrane or along with TM perforation. Based on the current review, when a TM perforation and spontaneous healing were documented, after blast exposure, MRI scan is an integral component of the follow-up. The optimal timing for MRI performance after blast exposure, is yet to be identified.

Impact of Blast Injury on Hearing in a Screened Male Military Population

Exposure to hazardous intensity levels of combat noise, such as blast, may compromise a person's ability to detect and recognize sounds and communicate effectively. There is little previous examination of the onset of hearing health outcomes following exposure to blast in representative samples of deployed US military personnel. Data from the prospective Blast-Related Auditory Injury Database were analyzed. We included only those participants with qualified hearing tests within a period of 12 months prior to, and following, injury (n = 1,574). After adjustment for relevant covariates and potential confounders, those who sustained a blast injury had significantly higher odds of postinjury hearing loss (odds ratio = 2.21; 95% confidence interval: 1.42, 3.44), low-frequency hearing loss (odds ratio = 1.95; 95% confidence interval: 1.01, 3.78), high-frequency hearing loss (odds ratio = 2.45; 95% confidence interval: 1.43, 4.20), and significant threshold shift compared with a group with non-blast-related injury. An estimated 49% of risk for hearing loss in these blast-injured, deployed military members could be attributed to the blast-related injury event. This study reinforced that it is imperative to identify at-risk populations for early intervention and prevention, as well as to consistently monitor the effects of blast injury on hearing outcomes.

Tympanoplasty following Blast Injury

Objectives

To assess outcomes following tympanoplasty for blast-induced tympanic membrane perforations in a military population.

Study Design

Case series with chart review.

Setting

Tertiary care medical centers.

Subjects and Methods

Military personnel (N = 254) undergoing tympanoplasty for blast-related tympanic membrane perforations sustained between April 2005 and July 2014 were identified from the Expeditionary Medical Encounter Database. Descriptive statistics were obtained regarding demographics, primary and revision surgery success rates, hearing status pre- and postsurgery, and frequency of ossicular reconstruction. Rates of successful perforation closure were assessed against perforation size and character (central vs marginal) and time to surgery. Rates and types of complications were additionally explored.

Results

There were a total of 352 operations among 254 subjects, with an 82.1% rate of successful closure following primary surgery. For successful primary tympanoplasty, the mean improvement in pure tone average was 11.7 ± 12.1 dB. Ossiculoplasty was performed in 9.1% (32 of 352) of cases. There was no significant relationship between successful perforation closure and perforation size, perforation character, or time between injury and surgery. Cholesteatoma complicated 4.3% (15 of 352) of cases. A significant relationship was identified between risk of cholesteatoma development and increasing perforation size and marginal perforations.

Conclusion

Tympanoplasty success rates for blast-induced tympanic membrane perforations are lower than for other common injury mechanisms. Due to appreciable rates of postoperative cholesteatoma development, close clinical surveillance is recommended.

Otologic assessment of blast and nonblast injury in returning Middle East-deployed service members

OBJECTIVES/HYPOTHESIS

To determine if tympanic membrane perforation offers any protection from inner ear damage and determine the incidence and pattern of otologic blast injury in military personnel returning from deployment.

STUDY DESIGN

Retrospective analysis of US service members injured in Operation Iraqi Freedom and Operation Enduring Freedom from October 2006 to October 2007.

METHODS

One-hundred ten blast-injured patients were compared to 54 nonblast-injured patients returning from deployment. Data captured included audiogram results, presence of tympanic membrane perforation, demographic data, location and nature of injury, loss of consciousness, sleep disturbance, confusion, and symptoms of headache, dizziness, memory loss, and tinnitus.

RESULTS

Of 110 blast-injured patients, 18 patients suffered tympanic membrane perforation (16%), of which nine patients suffered bilateral tympanic membrane perforation (8%). Blast patients suffered more hearing loss than controls as measured by pure-tone averages of varying speech reception frequencies and at 6,000 Hz. Of the blast patients who recorded an audiogram, nearly 24% suffered moderate to profound hearing loss. There was no statistically significant difference in hearing outcomes between blast-injured patients with tympanic membrane perforations and those without; however, when comparing patients with unilateral perforations with their contralateral ear, there was a difference in hearing thresholds at 6,000 Hz. There was a significantly increased risk of tinnitus, memory loss, headache, and dizziness between blast-injured patients compared to controls.

CONCLUSIONS

Due to its violent nature, blast exposure causes greater neuro-otological manifestations and deserves prompt otologic evaluation.

Adverse health consequences of the Iraq War

The adverse health consequences of the Iraq War (2003-11) were profound. We conclude that at least 116,903 Iraqi non-combatants and more than 4800 coalition military personnel died over the 8-year course. Many Iraqi civilians were injured or became ill because of damage to the health-supporting infrastructure of the country, and about 5 million were displaced. More than 31,000 US military personnel were injured and a substantial percentage of those deployed suffered post-traumatic stress disorder, traumatic brain injury, and other neuropsychological disorders and their concomitant psychosocial problems. Many family members of military personnel had psychological problems. Further review of the adverse health consequences of this war could help to minimise the adverse health consequences of, and help to prevent, future wars.

Blast-induced tinnitus and hearing loss in rats: behavioral and imaging assays

Abstract The current study used a rat model to investigate the underlying mechanisms of blast-induced tinnitus, hearing loss, and associated traumatic brain injury (TBI). Seven rats were used to evaluate behavioral evidence of tinnitus and hearing loss, and TBI using magnetic resonance imaging following a single 10-msec blast at 14 psi or 194 dB sound pressure level (SPL). The results demonstrated that the blast exposure induced early onset of tinnitus and central hearing impairment at a broad frequency range. The induced tinnitus and central hearing impairment tended to shift towards high frequencies over time. Hearing threshold measured with auditory brainstem responses also showed an immediate elevation followed by recovery on day 14, coinciding with behaviorally-measured results. Diffusion tensor magnetic resonance imaging results demonstrated significant damage and compensatory plastic changes to certain auditory brain regions, with the majority of changes occurring in the inferior colliculus and medial geniculate body. No significant microstructural changes found in the corpus callosum indicates that the currently adopted blast exposure mainly exerts effects through the auditory pathways rather than through direct impact onto the brain parenchyma. The results showed that this animal model is appropriate for investigation of the mechanisms underlying blast-induced tinnitus, hearing loss, and related TBI. Continued investigation along these lines will help identify pathology with injury/recovery patterns, aiding development of effective treatment strategies.

Adverse health consequences of US Government responses to the 2001 terrorist attacks

In response to the attacks on Sept 11, 2001 (9/11), and the related security concerns, the USA and its coalition partners began a war in Afghanistan and subsequently invaded Iraq. The wars caused many deaths of non-combatant civilians, further damaged the health-supporting infrastructure and the environment (already adversely affected by previous wars), forced many people to migrate, led to violations of human rights, and diverted resources away from important health needs. After 9/11 and the anthrax outbreak shortly afterwards, the USA and other countries have improved emergency preparedness and response capabilities, but these actions have often diverted attention and resources from more urgent health issues. The documentation and dissemination of information about the adverse health effects of these wars and about the diversion of resources could help to mitigate these consequences and prevent their recurrence.