Otologic considerations of blast injury

[Features of otosurgery in children after blast injuries]

An explosion is a process that rapidly releases a huge amount of energy in the form of heat, kinetic energy, and high-pressure shock waves. Since the organ of hearing is most susceptible to pressure changes, damage to the sound-conducting or sound-receiving systems is inevitable in case of an explosive injury. This article examines the mechanism of formation of explosive injuries of the middle and inner ear in children and adolescents, the features of diagnosis and tactics of surgical reconstructive treatment of explosive ear injuries based on the data available in the scientific literature and their own experience.

Acute High Level Noise Exposure Can Cause Physiological Dysfunction in Macaque Monkeys: Insight on the Medical Protection for Special Working Environmental Personnel

The high level noise caused by intense acoustic weapons and blasting is a common source of acute acoustic trauma faced by some special environmental personnel. Studies have shown that high level noise can cause auditory and non-auditory effects. However, there are few reports on the biological effects, especially the non-auditory effects of acute high level noise exposure in simulated special working environments, and the great differences between experimental animals and human beings make it difficult to extrapolate from research conclusions. In this study, macaque monkeys were used to detect the effects of acute high level noise exposure on hearing, cognition, and cardiovascular function. Auditory brainstem response, auditory P300, and electrocardiogram (ECG) of macaque monkeys were measured. Results showed that acute high level noise exposure caused permanent hearing threshold shifts; partial hearing loss which couldn’t recover to normal levels in the detection period; pathological changes in T wave and QRS complexes; and large fluctuations in cognitive ability after exposure, which finally recovered to normal. These alterations may be a combination of effects caused by stress-induced neuroendocrine dysfunction and mechanical damage of auditory organs. To elaborate the exact mechanism, further studies are still needed. Meanwhile, positive measures should be taken to reduce the incidence of acute high level noise injury.

Blast Exposure Causes Long-Term Degeneration of Neuronal Cytoskeletal Elements in the Cochlear Nucleus: A Potential Mechanism for Chronic Auditory Dysfunctions

Blast-induced auditory dysfunctions including tinnitus are the most prevalent disabilities in service members returning from recent combat operations. Most of the previous studies were focused on the effect of blast exposure on the peripheral auditory system and not much on the central auditory signal-processing regions in the brain. In the current study, we have exposed rats to single and tightly coupled repeated blasts and examined the degeneration of neuronal cytoskeletal elements using silver staining in the central auditory signal-processing regions in the brain at 24 h, 14 days, 1 month, 6 months, and 1 year. The brain regions evaluated include cochlear nucleus, lateral lemniscus, inferior colliculus, medial geniculate nucleus, and auditory cortex. The results obtained indicated that a significant increase in degeneration of neuronal cytoskeletal elements was observed only in the left and right cochlear nucleus. A significant increase in degeneration of neuronal cytoskeletal elements was observed in the cochlear nucleus at 24 h and persisted through 1 year, suggesting acute and chronic neuronal degeneration after blast exposure. No statistically significant differences were observed between single and repeated blasts. The localized degeneration of neuronal cytoskeletal elements in the cochlear nucleus suggests that the damage could be caused by transmission of blast shockwaves/noise through the ear canal and that use of suitable ear protection devices can protect against acute and chronic central auditory signal processing defects including tinnitus after blast exposure.

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.

Aural Blast Injury/Acoustic Trauma and Hearing Loss

Hearing is a critical sense to military performance. The ability to detect, identify, and localize sounds, the ability to maintain spatial awareness on the battlefield and the awareness to control one's own noise production can be vital to troop's stealth, survivability, and lethality. Hazardous noise is an environmental public health threat encountered in training at war, and in many off-duty activities. The risk to hearing and the resultant damage from any of these hazardous exposures is generally invisible, insidious and cumulative. Regardless of the source of injury, hearing loss degrades the sensor that integrates Service Members with their environment, provides for unity of effort, and ensures command and control.Acoustic trauma-induced hear loss and tinnitus are the two most prevalent disabilities in veterans, with over 765,000 cases in the Gulf War era alone. To counter this threat, it is necessary to push for early identification and early intervention through a trusted surveillance system. Success will require advocacy, education, and encouragement of self-reporting for evaluation following symptomatic noise exposures. This Clinical Practice Guideline (CPG) is a step to ensure the hearing health, readiness, protection, and care of Service Members. This will in turn optimize troop performance and minimize injury risk and mishap.

Autonomic responses to blast overpressure can be elicited by exclusively exposing the ear in rats

Blast overpressure has become an increasing cause of brain injuries in both military and civilian populations. Though blast's direct effects on the cochlea and vestibular organs are active areas of study, little attention has been given to the ear's contribution to the overall spectrum of blast injury. Acute autonomic responses to blast exposure, including bradycardia and hypotension, can cause hypoxia and contribute to blast-induced neurotrauma. Existing literature suggests that these autonomic responses are elicited through blast impacting the thorax and lungs. We hypothesize that the unprotected ear also provides a vulnerable locus for blast to cause autonomic responses. We designed a blast generator that delivers controlled overpressure waves into the ear canal without impacting surrounding tissues in order to study the ear's specific contribution to blast injury. Anesthetized adult rats' left ears were exposed to a single blast wave ranging from 0 to 110 PSI (0-758 kPa). Blast exposed rats exhibited decreased heart rates and blood pressures with increased blast intensity, similar to results gathered using shock tubes and whole-body exposure in the literature. While rats exposed to blasts below 50 PSI (345 kPa) exhibited increased respiratory rate with increased blast intensity, some rats exposed to blasts higher than 50 PSI (345 kPa) stopped breathing immediately and ultimately died. These autonomic responses were significantly reduced in vagally denervated rats, again similar to whole-body exposure literature. These results support the hypothesis that the unprotected ear contributes to the autonomic responses to blast.

A New Triage Support Tool in Case of Explosion

Deafness frequently observed in explosion victims, currently following terrorist attack, is a barrier to communication between victims and first responders. This may result in a delay in the initial triage and evacuation. In such situations, Paris Fire Brigade (Paris, France) proposes the use of assistance cards to help conscious, but deafened patients at the site of an attack where there may be numerous victims. Yavari-Sartakhti O , Briche F , Jost D , Michaud N , Bignand M , Tourtier JP . A new triage support tool in case of explosion. Prehosp Disaster Med. 2018;33(2):213-214.

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.

Ear trauma

Understanding basic ear anatomy and function allows an examiner to quickly and accurately identify at-risk structures in patients with head and ear trauma. External ear trauma (ie, hematoma or laceration) should be promptly treated with appropriate injury-specific techniques. Tympanic membrane injuries have multiple mechanisms and can often be conservatively treated. Temporal bone fractures are a common cause of ear trauma and can be life threatening. Facial nerve injuries and hearing loss can occur in ear trauma.

Explosions and human health: the long-term effects of blast injury

The immediate patterns of injury from explosions are well documented, from both military and civil experience. However, few studies have focused on less immediately apparent health consequences and latent effects of explosions in survivors, emergency responders and the surrounding community. This review aimed to analyze the risks to health following an explosion in a civil setting. A comprehensive review of the open literature was conducted, and data on 10 relevant military, civilian and industrial events were collected. Events were selected according to availability of published studies and involvement of large numbers of people injured. In addition, structured interviews with experts in the field were conducted, and existing national guidelines reviewed. The review revealed significant and potentially long-term health implications affecting various body systems and psychological well-being following exposure to an explosion. An awareness of the short- and long-term health effects of explosions is essential in screening for blast injuries, and identifying latent pathologies that could otherwise be overlooked in stressful situations with other visually distracting injuries and, often, mass casualties. Such knowledge would guide responsible medical staff in implementing early appropriate interventions to reduce the burden of long-term sequelae. Effective planning and response strategies would ensure accessibility of appropriate health care resources and evidence-based information in the aftermath of an explosion.

A forensic investigation into the etiology of bat mortality at a wind farm: barotrauma or traumatic injury?

Migrating bats have increased mortality near moving turbine blades at wind farms. The authors evaluated competing hypotheses of barotrauma and traumatic injury to determine the cause. They first examined the utility of lungs from salvaged bat carcasses for histopathologic diagnosis of barotrauma and studied laboratory mice as a model system. Postmortem time, environmental temperature, and freezing of carcasses all affected the development of vascular congestion, hemorrhage, and edema. These common tissue artifacts mimicked the diagnostic criteria of pulmonary barotrauma; therefore, lung tissues from salvaged bats should not be used for barotrauma diagnosis. The authors next compared wind farm (WF) bats to building collision (BC) bats collected near downtown Chicago buildings. WF bats had an increased incidence in fracture cases and specific bone fractures and had more external lacerations than BC bats. WF bats had additional features of traumatic injury, including diaphragmatic hernia, subcutaneous hemorrhage, and bone marrow emboli. In summary, 73% (190 of 262) of WF bats had lesions consistent with traumatic injury. The authors then examined for ruptured tympana, a sensitive marker of barotrauma in humans. BC bats had only 1 case (2%, 1 of 42), but this was attributed to concurrent cranial fractures, whereas WF bats had a 20% (16 of 81) incidence. When cases with concurrent traumatic injury were excluded, this yielded a small fraction (6%, 5 of 81) of WF bats with lesions possibly consistent with barotrauma etiology. Forensic pathology examination of the data strongly suggests that traumatic injury is the major cause of bat mortality at wind farms and, at best, barotrauma is a minor etiology.