Blast injury of the ear by massive explosion: a review of 41 cases

A systematic review of otologic injuries sustained in civilian terrorist explosions

PURPOSE

Determine the prevalence of otological symptoms and tympanic membrane perforation, healing rates of tympanic membrane perforation with surgical and conservative management, and hearing function in civilian victims of terrorist explosions.

METHODS

A systematic review was conducted with searches on Medline, Embase, EMCare and CINAHL for publications between the 1st January 1945 and 26th May 2023. Studies with quantitative data addressing our aims were included. This review is registered with PROSPERO: CRD42020166768. Among 2611 studies screened, 18 studies comprising prospective and retrospective cohort studies were included.

RESULTS

The percentage of eardrums perforated in patients admitted to hospital, under ENT follow up and attending the emergency department is 69.0% (CI 55.5-80.5%), 38.7% (CI 19.0-63.0%, I2 0.715%) and 21.0% (CI 11.9-34.3%, I2 0.718%) respectively. Perforated eardrums heal spontaneously in 62.9% (CI 50.4-73.8%, I2 0.687%) of cases and in 88.8% (CI 75.9-96.3%, I2 0.500%) of cases after surgery. Common symptoms present within one month of bombings are tinnitus 84.7% (CI 70.0-92.9%, I2 0.506%), hearing loss 83.0% (CI 64.5-92.9%, I2 0.505%) and ear fullness 59.7% (CI 13.4-93.4%, I2 0.719). Symptomatic status between one and six months commonly include no symptoms 57.5% (CI 46.0-68.3%), hearing loss 35.4% (CI 21.8-51.8%, I2 0.673%) and tinnitus 15.6% (CI 4.9-40.0%, I2 0.500%). Within one month of bombings, the most common hearing abnormality is sensorineural hearing loss affecting 26.9% (CI 16.9-40.1%, I2 0.689%) of ears 43.5% (CI 33.4-54.2%, I2 0.500) of people.

CONCLUSION

Tympanic membrane perforation, subjective hearing loss, tinnitus, ear fullness and sensorineural hearing loss are common sequelae of civilian terrorist explosions.

Blast-Induced Central Auditory Neurodegeneration Affects Tinnitus Development Regardless of Peripheral Cochlear Damage

Blast exposure causes serious complications, the most common of which are ear-related symptoms such as hearing loss and tinnitus. The blast shock waves can cause neurodegeneration of the auditory pathway in the brainstem, as well as the cochlea, which is the primary receptor for hearing, leading to blast-induced tinnitus. However, it is still unclear which lesion is more dominant in triggering tinnitus, the peripheral cochlea or the brainstem lesion owing to the complex pathophysiology and the difficulty in objectively measuring tinnitus. Recently, gap detection tests have been developed and are potentially well-suited for determining the presence of tinnitus. In this study, we investigated whether the peripheral cochlea or the central nervous system has a dominant effect on the generation of tinnitus using a blast-exposed mouse model with or without earplugs, which prevent cochlear damage from a blast transmitted via the external auditory canal. The results showed that the earplug (+) group, in which the cochlea was neither physiologically nor histologically damaged, showed a similar extent of tinnitus behavior in a gap prepulse inhibition of acoustic startle reflex test as the earplug (-) group, in which the explosion caused a cochlear synaptic loss in the inner hair cells and demyelination of auditory neurons. In contrast, both excitatory synapses labeled with VGLUT-1 and inhibitory synapses labeled with GAD65 were reduced in the ventral cochlear nucleus, and demyelination in the medial nucleus of the trapezoid body was observed in both groups. These disruptions significantly correlated with the presence of tinnitus behavior regardless of cochlear damage. These results indicate that the lesion in the brainstem could be dominant to the cochlear lesion in the development of tinnitus following blast exposure.

[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.

Incidence and Epidemiology of Traumatic Tympanic Membrane Rupture: A National Trauma Data Bank Analysis

The incidence of traumatic tympanic membrane rupture (TTMR) has increased over recent decades. The association of certain external injury causes and bone fracture patterns with TTMR is anecdotal. It has been suggested that a diagnosis of TTMR may be missed during the acute trauma admission. The authors sought to evaluate the incidence of TTMR according to external injury cause and evaluate the association of skull fracture patterns with TTMR using a national trauma database. A cross-sectional analysis of trauma encounters was conducted using the National Trauma Data Bank (NTDB) from 2008 to 2015. Demographic and injury data were abstracted. Poisson regression was used to determine the incidence rate ratios of tympanic membrane rupture by external injury cause and logistic regression was used to estimate odds ratios (OR) of TTMR by skull fracture type. A total of 8214 patients were identified with TTMR during acute admission. The majority were on average 30 years old, 76% male, 71% White, had a mean Injury Severity Score of 14, and 42% were admitted to level I centers. The incidence rate ratio was only higher in lightning related injuries [5.262; 95% confidence interval (CI): 4.194-6.602] when using those caused by explosives as a reference. Basilar skull (OR: 12.95; 95% CI: 12.095-12.866) and cranial vault (OR: 2.938; 95% CI: 2.647-3.260) fractures were most associated with TTMR. The high incidence TTMR in association with certain external causes of injury and types of skull fractures should drive screening in the acute setting in order to increase detection and reduce morbidity from missed injuries.

[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.

Otologic Injuries Secondary to Explosive Attack

The frequency of injuries secondary to terrorist attack explosion is globally increasing. Like any other country, our country experienced multiple suicide bombings in recent years. Otologic injuries may be observed after these kinds of attacks. Considering otologic complaints are well known medical results of explosion attacks, routine otologic evaluation in the first examining hospital-even in case of no relevant complaint- is crucial for establishing causal relation in following forensic medicine evaluation. In this study, 33 cases from 6 suicide bomber attacks in 4 different incidents that happened in Turkey were evaluated for otologic injuries. Two out of three patients were not evaluated for otologic injuries in their first hospital visit. It was considered that 8 cases had a loss of hearing and 9 cases had tympanic membrane rupture secondary to the explosion. Complaints such as hearing loss and tinnitus very often after a bomb attack, we saw that 22 of 33 included patients did not have an ear nose, and throat examination at the time of the incident. In this kind of attack, there can be various life-threatening injuries and therefore relatively less important evaluations such as ENT examination can often be overlooked.

Traumatic brain injury induced by exposure to blast overpressure via ear canal

Exposure to explosive shockwave often leads to blast-induced traumatic brain injury in military and civilian populations. Unprotected ears are most often damaged following exposure to blasts. Although there is an association between tympanic membrane perforation and TBI in blast exposure victims, little is known about how and to what extent blast energy is transmitted to the central nervous system via the external ear canal. The present study investigated whether exposure to blasts directed through the ear canal causes brain injury in Long-Evans rats. Animals were exposed to a single blast (0-30 pounds per square inch (psi)) through the ear canal, and brain injury was evaluated by histological and behavioral outcomes at multiple time-points. Blast exposure not only caused tympanic membrane perforation but also produced substantial neuropathological changes in the brain, including increased expression of c-Fos, induction of a profound chronic neuroinflammatory response, and apoptosis of neurons. The blast-induced injury was not limited only to the brainstem most proximal to the source of the blast, but also affected the forebrain including the hippocampus, amygdala and the habenula, which are all involved in cognitive functions. Indeed, the animals exhibited long-term neurological deficits, including signs of anxiety in open field tests 2 months following blast exposure, and impaired learning and memory in an 8-arm maze 12 months following blast exposure. These results suggest that the unprotected ear canal provides a locus for blast waves to cause TBI. This study was approved by the Institutional Animal Care and Use Committee at the University of Mississippi Medical Center (Animal protocol# 0932E, approval date: September 30, 2016 and 0932F, approval date: September 27, 2019).

Multimorbidity and quality of life after blast-related injury among US military personnel: a cluster analysis of retrospective data

Background

Blast injury emerged as a primary source of morbidity among US military personnel during the recent conflicts in Iraq and Afghanistan, and led to an array of adverse health outcomes. Multimorbidity, or the presence of two or more medical conditions in an individual, can complicate treatment strategies. To date, there is minimal research on the impact of multimorbidity on long-term patient-reported outcomes. We aimed to define multimorbidity patterns in a population of blast-injured military personnel, and to examine these patterns in relation to long-term quality of life (QOL).

Methods

A total of 1972 US military personnel who sustained a blast-related injury during military operations in Iraq and Afghanistan were identified from clinical records. Electronic health databases were used to identify medical diagnoses within the first year postinjury, and QOL was measured with a web-based assessment. Hierarchical cluster analysis methods using Ward’s minimum variance were employed to identify clusters with related medical diagnosis categories. Duncan’s multiple range test was used to group clusters into domains by QOL.

Results

Five distinct clusters were identified and grouped into three QOL domains. The lowest QOL domain contained one cluster with a clinical triad reflecting musculoskeletal pain, concussion, and mental health morbidity. The middle QOL domain had two clusters, one with concussion/anxiety predominating and the other with polytrauma. The highest QOL domain had two clusters with little multimorbidity aside from musculoskeletal pain.

Conclusions

The present study described blast-related injury profiles with varying QOL levels that may indicate the need for integrated health services. Implications exist for current multidisciplinary care of wounded active duty and veteran service members, and future research should determine whether multimorbidity denotes distinct post-blast injury syndromes.

Assessment of hearing loss induced by tympanic membrane perforations under blast environment

PURPOSES

This study provides an approach to estimating tympanic membrane perforation-induced hearing loss (HL) using a human middle ear model.

METHODS

Sixty-one cases of tympanic membrane perforation originating from fireworks were reported from the Ear-Nose-Throat Department. The otoscope, audiometry data and diagnosis records were organized, and gender, age, etiology, perforation size and diseased ear side were classified as independent variables. A multinomial regression model was used to analyze the potential effects of the variables on HL. Meanwhile, a human middle ear model was implemented to calculate the ensued HL resulting from different perforation areas and sites. In addition, linear regression models were used to establish functions between perforation size and HL.

RESULTS

The audiometry data indicate that HL at high frequencies (f > 2 kHz) is much more profound than that at the speech frequency band (f < 1 kHz). Compared with mild HL (<15 dB), mediate HL (15-30 dB) was correlated with the perforation area (p < 0.05, 95% CI), while severe HL (>30 dB) was affected by both perforation size and age (p < 0.05, 95% CI). However, other factors, including gender and diseased ear side, do not show a statistically significant effect on HL. Furthermore, the Kruskal-Wallis test result reveals that HL at frequencies of 0.25 kHz ≤ f ≤ 8 kHz is strongly associated with the perforation size (p < 0.05, 95% CI).

CONCLUSIONS

It is conclusive that HL is positively proportional to the perforation size. However, HL is not correlated with the perforation site for small perforation areas of < 10% (p > 0.05, 95% CI).

CD28 Deficiency Ameliorates Blast Exposure-Induced Lung Inflammation, Oxidative Stress, Apoptosis, and T Cell Accumulation in the Lungs via the PI3K/Akt/FoxO1 Signaling Pathway

Although CD28 is associated with the expression of inflammatory mediators, apoptosis-related protein, immunosuppression, and tumorigenesis, the effects of CD28 deficiency on blast exposure-induced lung injury have not been investigated. In this study, we have explored the effects of CD28 on blast exposure-induced lung injury and studied its potential molecular mechanisms. A mouse model of blast exposure-induced acute lung injury was established. Sixty C57BL/6 wild-type (WT) and CD28 knockout (CD28^−/−) mice were randomly divided into control or model groups. Lung tissue samples were collected 24 h and 48 h after blast injury. Histopathological changes and the expressions of inflammatory-related proteins were detected by hematoxylin-eosin, immunohistochemistry, and immunofluorescence staining. Apoptosis and oxidative stress were evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and reactive oxygen species (ROS). Inflammation, apoptosis, oxidative stress, and related pathway protein expression were studied by western blotting. In addition, the levels of CD3 and CD28 proteins were measured by flow cytometry. In the current study, we found that CD28 deficiency significantly inhibited blast exposure-induced increases in the lung weight/body weight ratio and wet weight/dry weight ratio; decreased the infiltration of CD44⁺ leukocytes, CD163⁺ macrophages, and CD3⁺ T cells into the lungs; reduced the expressions of proinflammatory cytokines including IL-1β, TNF-α, and IL-6; and markedly increased IL-10 expression. CD28 deficiency also significantly attenuated blast exposure-induced ROS, MDA5, and IREα expressions; increased SOD-1 expression; lowered the number of apoptotic cells and Bax, Caspase-3, and active Caspase-8 expressions; and increased Bcl-2 expression. Additionally, CD28 deficiency significantly ameliorated blast exposure-induced increases of p-PI3K and p-Akt and ameliorated the decrease in the p-FoxO1 expression. Our results suggest that CD28 deficiency has a protective effect on blast exposure-induced lung injury, which might be associated with the PI3K/Akt/FoxO1 signaling pathway.

Analysis of cases managed by the otolaryngology service in the Chinese military peacekeeping level 2 medical treatment facility in Mali

OBJECTIVES

As part of the UN peacekeeping mission in Mali, the People's Republic of China have deployed a level 2 medical treatment facility (CHN L2). The aim of this study was to review the cases managed by the otolaryngology service within this facility.

METHODS

The medical records of all patients treated by the otolaryngology service at the CHN L2 from 1 March 2015 to 1 March 2018 were retrospectively assessed.

RESULTS

614/10189 (6%) of all cases seen in the hospital during this period were referred to the otolaryngology service. 7/614 cases required admission to hospital (1.14%) and 40/614 cases required surgery (6.51%). 3/40 cases requiring surgery (7.5%) were performed under general anaesthesia and 37 cases (92.5%) were under local anaesthesia. The most common surgical treatment was facial soft-tissue injury debridement and closure. Acute rhinosinusitis was the most common diagnosis, followed by acute pharyngitis and allergic rhinitis. Four patients required medical evacuation to a level 3 medical treatment facility.

CONCLUSIONS

Disease non-battle injury in the form of ear disease was the most common presentation. Maxillofacial soft-tissue injury was the most common cause of traumatic injury. There were limits that the service could provide in terms of medical equipment and consumables, necessitating increased training of otolaryngologists prior to deployment.

Primary Blast Brain Injury Mechanisms: Current Knowledge, Limitations, and Future Directions

Mild blast traumatic brain injury (bTBI) accounts for the majority of brain injury in United States service members and other military personnel worldwide. The mechanisms of primary blast brain injury continue to be disputed with little evidence to support one or a combination of theories. The main hypotheses addressed in this review are blast wave transmission through the skull orifices, direct cranial transmission, skull flexure dynamics, thoracic surge, acceleration, and cavitation. Each possible mechanism is discussed using available literature with the goal of focusing research efforts to address the limitations and challenges that exist in blast injury research. Multiple mechanisms may contribute to the pathology of bTBI and could be dependent on magnitudes and orientation to blast exposure. Further focused biomechanical investigation with cadaver, in vivo, and finite element models would advance our knowledge of bTBI mechanisms. In addition, this understanding could guide future research and contribute to the greater goal of developing relevant injury criteria and mandates to protect our soldiers on the battlefield.

Understanding blast-induced neurotrauma: how far have we come?

Blast injuries, including blast-induced neurotrauma (BINT), are caused by blast waves generated during an explosion. Accordingly, their history coincides with that of explosives. Hence, it is intriguing that, after more than 1000 years of using explosives, our understanding of the pathological consequences of blast and body/brain interactions is extremely limited. Postconflict recovery mechanisms seemingly include the suppression of painful experiences, such as explosive injuries. Unfortunately, ignoring the knowledge generated by previous generations of scientists retards research progress, leading to superfluous and repetitive studies. This article summarizes clinical and experimental findings published about blast injuries and BINT following the wars of the 20th and 21th centuries. Moreover, it offers a personal view on potential factors interfering with the progress of BINT research working toward providing better diagnosis, treatment and rehabilitation for military personnel affected by blast exposure.