Tympanic membrane perforation and hearing loss from blast overpressure in Operation Enduring Freedom and Operation Iraqi Freedom wounded

Using Body-worn Accelerometers to Detect Physiological Changes During Periods of Blast Overpressure Exposure

Repetitive exposure to non-concussive blast expo-sure may result in sub-clinical neurological symptoms. These changes may be reflected in the neural control gait and balance. In this study, we collected body-worn accelerometry data on individuals who were exposed to repetitive blast overpressures as part of their occupation. Accelerometry features were gener-ated within periods of low-movement and gait. These features were the eigenvalues of high-dimensional correlation matrices, which were constructed with time-delay embedding at multiple delay scales. When focusing on the gait windows, there were significant correlations of the changes in features with the cumulative dose of blast exposure. When focusing on the low-movement frames, the correlation with exposure were lower than that of the gait frames and statistically insignificant. In a cross-validated model, the overpressure exposure was predicted from gait features alone. The model was statistically significant and yielded an RMSE of 1.27 dB. With continued development, the model may be used to assess the physiological effects of repetitive blast exposure and guide training procedures to minimize impact on the individual.

Estimated Prevalence of Functional Hearing Difficulties in Blast-Exposed Service Members With Normal to Near-Normal-Hearing Thresholds

OBJECTIVES

Over the past decade, U.S. Department of Defense and Veterans Affairs audiologists have reported large numbers of relatively young adult patients who have normal to near-normal audiometric thresholds but who report difficulty understanding speech in noisy environments. Many of these service members also reported having experienced exposure to explosive blasts as part of their military service. Recent studies suggest that some blast-exposed patients with normal to near-normal-hearing thresholds not only have an awareness of increased hearing difficulties, but also poor performance on various auditory tasks (sound source localization, speech recognition in noise, binaural integration, gap detection in noise, etc.). The purpose of this study was to determine the prevalence of functional hearing and communication deficits (FHCD) among healthy Active-Duty service men and women with normal to near-normal audiometric thresholds.

DESIGN

To estimate the prevalence of such FHCD in the overall military population, performance of roughly 3400 Active-Duty service members with hearing thresholds mostly within the normal range were measured on 4 hearing tests and a brief 6-question survey to assess FHCD. Subjects were subdivided into 6 groups depending on the severity of the blast exposure (3 levels: none, far away, or close enough to feel heat or pressure) and hearing thresholds (2 levels: audiometric thresholds of 20 dB HL or better, slight elevation in 1 or more thresholds between 500 and 4000 Hz in either ear).

RESULTS

While the probability of having hearing difficulty was low (≈4.2%) for the overall population tested, that probability increased by 2 to 3 times if the service member was blast-exposed from a close distance or had slightly elevated hearing thresholds (>20 dB HL). Service members having both blast exposure and mildly elevated hearing thresholds exhibited up to 4 times higher risk for performing abnormally on auditory tasks and more than 5 times higher risk for reporting abnormally low ratings on the subjective questionnaire, compared with service members with no history of blast exposure and audiometric thresholds ≤20 dB HL. Blast-exposed listeners were roughly 2.5 times more likely to experience subjective or objective hearing deficits than those with no-blast history.

CONCLUSIONS

These elevated rates of abnormal performance suggest that roughly 33.6% of Active-Duty service members (or approximately 423,000) with normal to near-normal-hearing thresholds (i.e., H1 profile) are at some risk for FHCD, and about 5.7% (approximately 72,000) are at high risk, but are currently untested and undetected within the current fitness-for-duty standards. Service members identified as "at risk" for FHCD according to the metrics used in the present study, in spite of their excellent hearing thresholds, require further testing to determine whether they have sustained damage to peripheral and early-stage auditory processing (bottom-up processing), damage to cognitive processes for speech (top-down processing), or both. Understanding the extent of damage due to noise and blast exposures and the balance between bottom-up processing deficits and top-down deficits will likely lead to better therapeutic strategies.

Longitudinal auditory pathophysiology following mild blast-induced trauma

Blast-induced hearing difficulties affect thousands of veterans and civilians. The long-term impact of even a mild blast exposure on the central auditory system is hypothesized to contribute to lasting behavioral complaints associated with mild blast traumatic brain injury (bTBI). Although recovery from mild blast has been studied separately over brief or long time windows, few, if any, studies have investigated recovery longitudinally over short-term and longer-term (months) time windows. Specifically, many peripheral measures of auditory function either recover or exhibit subclinical deficits, masking deficits in processing complex, real-world stimuli that may recover differently. Thus, examining the acute time course and pattern of neurophysiological impairment using appropriate stimuli is critical to better understanding and intervening in bTBI-induced auditory system impairments. Here, we compared auditory brainstem response, middle-latency auditory-evoked potentials, and envelope following responses. Stimuli were clicks, tone pips, amplitude-modulated tones in quiet and in noise, and speech-like stimuli (iterated rippled noise pitch contours) in adult male rats subjected to mild blast and sham exposure over the course of 2 mo. We found that blast animals demonstrated drastic threshold increases and auditory transmission deficits immediately after blast exposure, followed by substantial recovery during the window of 7-14 days postblast, although with some deficits remaining even after 2 mo. Challenging conditions and speech-like stimuli can better elucidate mild bTBI-induced auditory deficit during this period. Our results suggest multiphasic recovery and therefore potentially different time windows for treatment, and deficits can be best observed using a small battery of sound stimuli.NEW & NOTEWORTHY Few studies on blast-induced hearing deficits go beyond simple sounds and sparsely track postexposure. Therefore, the recovery arc for potential therapies and real-world listening is poorly understood. Evidence suggested multiple recovery phases over 2 mo postexposure. Hearing thresholds largely recovered within 14 days and partially explained recovery. However, midlatency responses, responses to amplitude modulation in noise, and speech-like pitch sweeps exhibited extended changes, implying persistent central auditory deficits and the importance of subclinical threshold shifts.

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.

Paper Patching Versus Watchful Waiting of Traumatic Tympanic Membrane Perforations: A Meta-Analysis

OBJECTIVES/HYPOTHESIS

The aim of the study was to investigate the healing rates, the restoration of hearing, and the time for complete healing of paper patching versus watchful waiting for traumatic tympanic membrane perforations (TTMPs).

STUDY DESIGN

Systematic review with meta analysis.

METHODS

Publications were selected by a search on "PubMed," "Embase," and "Web of Science." A meta-analysis of risk ratios for paper patching (intervention arm) and watchful waiting (control arm) was performed.

RESULTS

Five studies describing 393 TTMPs were included in the quantitative meta-analysis. TTMP healing rates ranged between 84.2% and 95.2% in the intervention arm and between 76.7% and 84.8% in the control arm. The pooled risk ratio of healed TTMPs was significantly higher in the intervention arm than in the control arm (risk ratio: 1.12, 95% confidence interval: 1.04-1.21).

CONCLUSIONS

TTMPs have high healing potential with and without intervention. The healing rate of paper patching was superior to that of watchful waiting alone.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:2091-2097, 2021.

An insight to tympanic membrane perforation pressure through morphometry: A cadaver study

INTRODUCTION

A cadaveric experimental investigation aimed to show the rupture pressure of the tympanic membrane (TM) for otologists to evaluate its tensile strength.

METHODS

Twenty adult ears in 10 fresh frozen whole cadaveric heads (four males, six females) mean age 72.8 (SD 13.8) years (range 40-86) were studied. The tensile strength of the TM was evaluated with bursting pressure of the membrane. The dimensions of the membranes and perforations were measured with digital imaging software.

RESULTS

The mean bursting pressure of the TM was 97.71 (SD 36.20) kPa. The mean area, vertical and horizontal diameters of the TM were 57.46 (16.23) mm², 9.54 (1.27) mm, 7.99 (1.08) mm respectively. The mean area, length and width of the perforations were 0.55 (0.25) mm², 1.37 (0.50) mm, and 0.52 (0.22) mm, respectively. Comparisons of TM dimension, bursting pressure, and perforation size by laterality and gender showed no significant differences. The bursting pressure did not correlate (positively or negatively) with the TM or perforation sizes.

CONCLUSIONS

The TM can rupture during activities such as freediving or scuba diving, potentially leading to serious problems including brain injuries. Studying such events via cadaveric studies and data from case studies is of fundamental importance. The minimum experimental bursting pressures might better be taken into consideration rather than average values as the danger threshold for prevention of TM damage (and complications thereof) by barotrauma.

Comparison of fetal and adult tympanic membrane sizes: a cadaveric study

OBJECTIVE

The work aimed to compare fetal and adult tympanic membrane (TM) sizes for understanding dimensional development from intrauterine life to adulthood.

METHODS

Fifty-six temporal bones (18 fetuses, 10 elderly adults, half male and half female in each group) were included in this study. Using a digital image software, the TM height, width and area were measured.

RESULTS

The mean area, height and width of the TM in adults were found as 58.84 ± 22.01 mm2, 9.06 ± 1.33 mm, and 8.10 ± 1.43 mm, respectively. Moreover, the mean area, height and width of the TM in fetuses were measured as 47.62 ± 12.57 mm2, 8.22 ± 1.12 mm, and 7.25 ± 1.15 mm, respectively. The TM dimensions were increasing in fetuses between 20-32 weeks of gestation. However, the TM dimension was statistically similar at the 7th month, the 8th month and adult periods. The TM height was greater than its width in fetuses and adults.

CONCLUSION

The calculated regression equations of the TM parameters in fetuses may be used to estimate its size. The TM size did not change from the 7th gestational month, and thus the membrane reached adult diameter in fetal life. The TM height and width showed a very wide range; therefore, we thought that the 12 mm (the height) × 10 mm (the width) graft might be ideal dimension during the repair of the TM perforations.

[Spontaneous course of traumatic tympanic membrane perforations]

BACKGROUND

Traumatic eardrum perforation is a common presentation in otorhinolaryngologic practices and emergency clinics. A consistent management strategy (active intervention vs. watchful waiting) is, however, still lacking.

OBJECTIVE

In the following study, the outcome of watchful waiting is analyzed and presented.

MATERIALS AND METHODS

A collective of 272 patients presenting at two different specialist ENT practices within days of traumatic tympanic membrane perforation from June 2002 to March 2019 were analyzed. Treatment was non-surgical, with prospective monitoring. Whereas antibiotics were not given at all in one practice, they were given only upon signs of infection in the other practice. The outcome was evaluated retrospectively on the basis of patient files.

RESULTS

The collective consisted of 185 males and 87 females. Mean age was 30 years (range: 7 months to 82 years). The perforations were most commonly located in the upper anterior and lower posterior quadrants. According to Griffin grading, the size was grade I in 97%. The three most common causes were impact to the ear, barotrauma, and foreign bodies. Under a watchful waiting regimen, 95% of the patients presenting for follow-up checks showed complete closure.

CONCLUSION

Watchful waiting can be assessed as appropriate in traumatic eardrum perforation, provided otorhinolaryngologic follow-up is ensured. An exception is blast injury, which is now much less common in Central Europe, as this is associated with a risk of secondary cholesteatomas. In these rare cases, active treatment with surgical exploration of the middle ear including relining the perforation is indicated.

Prevalence of Tinnitus and Association with Self-Rated Health among Military Personnel Injured on Combat Deployment

INTRODUCTION

Tinnitus is an auditory problem frequently reported by military personnel and is currently responsible for 1 billion dollars annually in disability compensation. Recent military conflicts in Iraq and Afghanistan saw high levels of combat exposure coupled with a surge in blast weaponry, both of which can adversely affect hearing. The present study explored the prevalence of tinnitus and the association with self-rated health among military personnel injured during combat deployment.

MATERIALS AND METHODS

A total of 1,026 U.S. military personnel who sustained an injury during operations (592 battle blast, 73 battle nonblast, 361 nonbattle) in Iraq were identified from clinical records. Post-Deployment Health Assessments administered at two separate points in time were used to identify self-reported tinnitus symptoms and self-rated health within 1 year of injury.

RESULTS

Those with a battle blast injury had the highest prevalence of tinnitus with 19.1% and 31.3% on the first and second health assessments, respectively. In a multivariate model adjusting for combat exposure, concussion, posttraumatic stress disorder, and other covariates, tinnitus was associated with lower self-rated health for both the first (odds ratio [OR] = 3.31, 95% confidence interval [CI] = 2.07-5.30, P < 0.001) and second assessments (OR = 2.52, 95% CI = 1.76-3.61, P < 0.001).

CONCLUSIONS

Tinnitus is a common source of impairment among military personnel injured during combat deployment and is associated with poorer self-rated health. Future research should determine whether timing of assessment is linked to symptom recognition or reporting, and what interventions are best suited for ameliorating the negative impact of tinnitus.

The Development of a Tympanic Membrane Model and Probabilistic Dose-Response Risk Assessment of Rupture Because of Blast

INTRODUCTION

There is no dose-response model available for the assessment of the risk of tympanic membrane rupture (TMR), commonly known as eardrum rupture, from exposures to blast from nonlethal flashbangs, which can occur concurrently with temporary threshold shift. Therefore, the objective of this work was to develop a fast-running, lumped parameter model of the tympanic membrane (TM) with probabilistic dose-dependent prediction of injury risk.

MATERIALS AND METHODS

The lumped parameter model was first benchmarked with a finite element model of the middle ear. To develop the dose-response curves, TMR data from a historic cadaver study were utilized. From these data, the binary probability response was constructed and logistic regression was applied to generate the respective dose-response curves at moderate and severe eardrum rupture severity.

RESULTS

Hosmer-Lemeshow statistical and receiver operation characteristic analyses showed that maximum stored TM energy was the overall best dose metric or injury correlate when compared with total work and peak TM pressure.

CONCLUSIONS

Dose-response curves are needed for probabilistic risk assessments of unintended effects like TMR. For increased functionality, the lumped parameter model was packaged as a software library that predicts eardrum rupture for a given blast loading condition.

Blast-induced tinnitus: Animal models

Blast-induced tinnitus is a prevalent problem among military personnel and veterans, as blast-related trauma damages the vulnerable microstructures within the cochlea, impacts auditory and non-auditory brain structures, and causes tinnitus and other disorders. Thus far, there is no effective treatment of blast-induced tinnitus due to an incomplete understanding of its underlying mechanisms, necessitating development of reliable animal models. This article focuses on recent animal studies using behavioral, electrophysiological, imaging, and pharmacological tools. The mechanisms underlying blast-induced tinnitus are largely similar to those underlying noise-induced tinnitus: increased spontaneous firing rates, bursting, and neurosynchrony, Mn++ accumulation, and elevated excitatory synaptic transmission. The differences mainly lie in the data variability and time course. Noise trauma-induced tinnitus mainly originates from direct peripheral deafferentation at the cochlea, and its etiology subsequently develops along the ascending auditory pathways. Blast trauma-induced tinnitus, on the other hand, results from simultaneous impact on both the peripheral and central auditory systems, and the resultant maladaptive neuroplasticity may also be related to the additional traumatic brain injury. Consequently, the neural correlates of blast-induced tinnitus have different time courses and less uniform manifestations of its neural correlates.

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.

Effects of tympanic membrane perforation on middle ear transmission in gerbil

Perforations of the tympanic membrane (TM) alter its structural and mechanical properties, thus resulting in a deterioration of sound transmission through the middle ear (ME), which presents itself clinically as a conductive hearing loss (CHL). The resulting CHL is proposed to be due to the loss of the pressure difference across the TM between the outer ear canal space and the ME cavity, a hypothesis which has been tested with both theoretical and experimental approaches. In the past, direct experimental observations had been either from the ME input (umbo) or the output of the stapes, and were focused mainly on the low frequency region. However, there was little documentation providing a thorough picture of the influence of systematically increasing sizes of TM perforations on ME sound transmission from the input (i.e., pressure at the TM or motion of the umbo) to the output (pressure produced by the motion of the stapes). Our study explored ME transmission in gerbil under conditions of a normal, intact TM followed by the placement of mechanically-induced TM perforations ranging from miniscule to complete removal of the pars tensa, leaving the other parts of ME intact. Testing up to 50 kHz, variations of ME transmission were characterized in simultaneously measured tone induced pressure responses at the TM (P_TM), pressure responses in the scala vestibuli next to the stapes (P_SV), and velocity measurements of the umbo (V_umbo), as well as by detailed descriptions of sound transmission from the TM to the stapes, i.e., the umbo transfer function (TF), the transfer of the sound stimulus along the ossicular chain as found from the ratio of cochlear pressure to umbo motion, and ME pressure gain (MEPG). Our results suggested that increasing the size of TM perforations led to a reduction in MEPG, which appeared to be primarily due to the reduction in the effective/initial mechanical drive to the umbo, with a relatively smaller decrease of sound transfer along the ossicular chain. Expansion of the perforation more than 25% appeared to drastically reduce sound transmission through the ME, especially for the higher frequencies.

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.

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.

Differences in postinjury auditory system pathophysiology after mild blast and nonblast acute acoustic trauma

Hearing difficulties are the most commonly reported disabilities among veterans. Blast exposures during explosive events likely play a role, given their propensity to directly damage both peripheral (PAS) and central auditory system (CAS) components. Postblast PAS pathophysiology has been well documented in both clinical case reports and laboratory investigations. In contrast, blast-induced CAS dysfunction remains understudied but has been hypothesized to contribute to an array of common veteran behavioral complaints, including learning, memory, communication, and emotional regulation. This investigation compared the effects of acute blast and nonblast acoustic impulse trauma in adult male Sprague-Dawley rats. An array of audiometric tests were utilized, including distortion product otoacoustic emissions (DPOAE), auditory brain stem responses (ABR), middle latency responses (MLR), and envelope following responses (EFRs). Generally, more severe and persistent postinjury central auditory processing (CAP) deficits were observed in blast-exposed animals throughout the auditory neuraxis, spanning from the cochlea to the cortex. DPOAE and ABR results captured cochlear and auditory nerve/brain stem deficits, respectively. EFRs demonstrated temporal processing impairments suggestive of functional damage to regions in the auditory brain stem and the inferior colliculus. MLRs captured thalamocortical transmission and cortical activation impairments. Taken together, the results suggest blast-induced CAS dysfunction may play a complementary pathophysiological role to maladaptive neuroplasticity of PAS origin. Even mild blasts can produce lasting hearing impairments that can be assessed with noninvasive electrophysiology, allowing these measurements to serve as simple, effective diagnostics.NEW & NOTEWORTHY Blasts exposures often produce hearing difficulties. Although cochlear damage typically occurs, the downstream effects on central auditory processing are less clear. Moreover, outcomes were compared between individuals exposed to the blast pressure wave vs. those who experienced the blast noise without the pressure wave. It was found that a single blast exposure produced changes at all stages of the ascending auditory path at least 4 wk postblast, whereas blast noise alone produced largely transient changes.

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.

A critical literature review on primary blast thorax injury and their outcomes

Since World War II, researchers have been interested in exploring the injury mechanisms involved in primary blast on the thorax by using animal model surrogates. These studies were mostly concerned with the finding of the lung injury threshold, the relationship between the physical components of the air blast wave, and the biological response. Studies have also been conducted to investigate the effect of repeated blast exposures on the injury outcome threshold. This has led to several injury criteria, such as the Bowen curves based on pressure history's characteristics or the Axelsson Chest Wall Velocity Predictor that used measurement from the mammals' chest wall. This article aims at doing a critical literature review of this specific topic.

Analysis of Effect of Eggshell Membrane Patching for Moderate-to-Large Traumatic Tympanic Membrane Perforation

Background and Objectives

To evaluate the effect of eggshell membrane (ESM) patching for tympanic membrane (TM) perforation, and to investigate correlations between healing time and age, gender, patching time, perforation size, and perforation location.

Subjects and Methods

One hundred and seventy-five patients diagnosed with traumatic TM perforation at the Department of Otorhinolaryngology-Head and Neck Surgery, Korea University Ansan Hospital, between January 2008 and October 2013. Patients were divided into two groups, according to perforation edge approximation or ESM patching treatment. Healing time was compared between the group that received perforation edge approximation and the group that received ESM patching. Perforation grade, age, onset, and location were also compared between the two groups.

Results

ESM patching significantly improved healing time compared to spontaneous healing, especially in patients with moderate or large traumatic TM perforations (≥grade II). However, patient age, gender, perforation location, and especially timing of procedure, did not significantly affect healing time.

Conclusions

ESM patching can be a good treatment choice to promote tympanic membrane healing in large traumatic TM perforations.

Characterization of the nonlinear elastic behavior of chinchilla tympanic membrane using micro-fringe projection

The mechanical properties of an intact, full tympanic membrane (TM) inside the bulla of a fresh chinchilla were measured under quasi-static pressure from -1.0 kPa to 1.0 kPa applied on the TM lateral side. Images of the fringes projected onto the TM were acquired by a digital camera connected to a surgical microscope and analyzed using a phase-shift method to reconstruct the surface topography. The relationship between the applied pressure and the resulting volume displacement was determined and analyzed using a finite element model implementing a hyperelastic 2(nd)-order Ogden model. Through an inverse method, the best-fit model parameters for the TM were determined to allow the simulation results to agree with the experimental data. The nonlinear stress-strain relationship for the TM of a chinchilla was determined up to an equibiaxial tensile strain of 31% experienced by the TM in the experiments. The average Young's modulus of the chinchilla TM from ten bullas was determined as approximately 19 MPa.

Utility of basic fibroblast growth factor in the repair of blast-induced total or near-total tympanic membrane perforations: A pilot study

OBJECTIVE

A pilot study was performed to investigate the utility of basic fibroblast growth factor (bFGF) in the repair of blast-induced total or near-total tympanic membrane perforations (TMPs).

STUDY DESIGN

Prospective clinical study.

SETTING

Tertiary university hospital.

SUBJECTS AND METHODS

Patients who fulfilled the inclusion criteria were treated with 0.10-0.15 mL of bFGF solution applied directly to total or near-total TMPs once daily until the perforations closed or for a maximum of 6 months. The treatment response was monitored via serial otoendoscopy, and audiometric outcomes were evaluated.

RESULTS

Complete TMP closure was achieved in 16 of 17 patients with a blast-induced total or near-total TMP. The mean closure time was 28.4 ± 10.9 days. The improvement in hearing from pre- to post-treatment was statistically significant. There were no complications or adverse outcomes.

CONCLUSIONS

The direct application of bFGF to blast-induced total or near-total TMPs is a promising, minimally invasive alternative to conventional tympanoplasty, with a comparable success rate. As reported in the literature, the closure rate was higher than achieved with spontaneous healing. There was no effect of the inverted edge on healing outcome. The use of bFGF in this setting has immediate therapeutic applications for military personnel with blast-induced TMPs who are stationed in isolated, remote environments.

Hearing loss associated with US military combat deployment

The objective of this study was to define the risk of hearing loss among US military members in relation to their deployment experiences. Data were drawn from the Millennium Cohort Study. Self-reported data and objective military service data were used to assess exposures and outcomes. Among all 48,540 participants, 7.5% self-reported new-onset hearing loss. Self-reported hearing loss showed moderate to substantial agreement (k = 0.57-0.69) with objective audiometric measures. New-onset hearing loss was associated with combat deployment (adjusted odds ratio [AOR] = 1.63, 95% confidence interval [CI] = 1.49-1.77), as well as male sex and older age. Among deployers, new-onset hearing loss was also associated with proximity to improvised explosive devices (AOR = 2.10, 95% CI = 1.62-2.73) and with experiencing a combat-related head injury (AOR = 6.88, 95% CI = 3.77-12.54). These findings have implications for health care and disability planning, as well as for prevention programs.

Otoscope fogging: examination finding for perforated tympanic membrane

The author reports a recently recognised physical examination finding, otoscope fogging, for perforated tympanic membrane. Otoscope fogging is defined as condensation forming in the view field of the otoscope while inspecting the ear. In the setting of occult perforation secondary to the inability to visualise the entire tympanic membrane, otoscope fogging may provide the clinician with valuable information since medical management may differ if perforation is present.

Healing outcomes of large (>50%) traumatic membrane perforations with inverted edges following no intervention, edge approximation and fibroblast growth factor application; a sequential allocation, three-armed trial

OBJECTIVE

The goal of this study was to evaluate the effects of perforation edge approximation and direct application of basic fibroblast growth factor (bFGF) each alone on the healing of large traumatic tympanic membrane perforations with inverted edges in humans.

STUDY DESIGN

Prospective, sequential allocation, three-armed, controlled clinical study.

SETTING

University-affiliated teaching hospital.

PARTICIPANTS

Fifty-eight patients with large traumatic tympanic membrane perforations (i.e. affecting >50% of the surface area) with inverted edges were recruited. They were sequentially allocated to three groups: no intervention (n = 18), edge approximation alone (n = 20) and direct application of bFGF (n = 20). Otoscopy were performed before the treatment and at follow-up visits.

MAIN OUTCOME MEASURES

The closure rate, closure time and rate of otorrhoea.

RESULTS

Application of bFGF yielded a significantly higher average rate of perforation closure (100%) than edge approximation (60%) and no intervention (56%) (P < 0.05). It also significantly shortened the average closure time (12.4 ± 3.6 days) as compared to edge approximation (46.3 ± 8.7 days) and no intervention control (48.2 ± 5.3 days) (P < 0.05). Purulent otorrhoea was observed in none of the three groups.

CONCLUSION

Edge approximation of inverted edges has little benefit in improving the healing outcome of large traumatic tympanic membrane perforations and thus is not an ideal treatment option for large traumatic tympanic membrane perforations. Application of bFGF materially improves the closure rate of large traumatic tympanic membrane perforations and significantly shortens the closure time.

Impact of basic fibroblast growth factor on healing of tympanic membrane perforations due to direct penetrating trauma: a prospective non-blinded/controlled study

OBJECTIVE

To investigate the effect of direct application of basic fibroblast growth factor (bFGF) on healing of tympanic membrane perforations due to direct traumatic penetration through the external auditory canal.

DESIGN

A prospective non-blinded controlled study.

SETTING

University-affiliated teaching hospital.

PARTICIPANTS

In total, 104 patients with small [<25%] penetrating perforations were recruited. They were alternatively allocated to two groups: Control (spontaneous healing, n = 51) and FGF treatment (direct application of bFGF drops in the clinic and repeated daily by the patient, n = 53).

OUTCOMES

Perforation closure rate and time and hearing gain were recorded and compared between the two groups. Information on earache, dizziness and facial paralysis was also collected.

RESULTS

In total, 93 (89%) patients were finally analysed. The closure rate at 3 m of the perforations in the control spontaneous healing and bFGF treatment groups were 77% and 100%, respectively; the difference was statistically significant (P = 0.01). The average closure time was 43.1 ± 2.5 days (range, 17-57 days) for control patients, which was significantly longer (P < 0.01) than that for the bFGF-treated patients (12.6 ± 1.2 days; range, 3-21 days). The mean hearing improvement at 3 m was not significantly different between the FGF treatment and control groups (1.7 ± 2.4 dB vs 11.5 ± 1.9 dB, P > 0.05). No significant difference was observed in earache, dizziness and facial paralysis between two groups.

CONCLUSIONS

Direct application of bFGF may offer an effective topical management of penetrating traumatic tympanic membrane perforations, particularly for small-sized perforations.

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.

Healing large traumatic eardrum perforations in humans using fibroblast growth factor applied directly or via gelfoam

OBJECTIVE

The goal of this study was to evaluate the effects of conservative treatment and fibroblast growth factor (FGF) applied directly or via Gelfoam on the healing of large traumatic tympanic membrane perforations (TMPs) in humans.

STUDY DESIGN

Prospective, randomized, controlled trial.

METHODS

A randomized prospective analysis was performed between February 2009 and January 2011 for the treatment of traumatic TMPs in humans that affected greater than 50% of the TM. The closure rate, closure time, hearing gain, and rate of otorrhea were compared among the direct application of FGF, FGF via Gelfoam, and conservative treatment.

RESULTS

A total of 94 patients were analyzed. The closure rates of large perforations in the direct FGF application, FGF via Gelfoam, and observation groups were 100%, 97%, and 55%, respectively. FGF-treated groups had significantly improved closure rates compared with the observation group (p < 0.05). However, the closure rate did not differ significantly between patients who received FGF only and those who received FGF via Gelfoam (p > 0.05). FGF-treated groups showed shorter mean closure times compared with the observation group (p < 0.05). However, the closure time did not differ significantly between FGF-treated groups (p > 0.05).All perforations were closed within 2 weeks, regardless of the presence of curled edges in the FGF-treated groups.

Ear trauma in orlu, Nigeria: a five-year review

To review the presentation, types and aetiology of ear trauma and various factors affecting ear trauma in our patients over a 5 year period. All patients treated for ear trauma over a 5 year period were studied using their clinical records. Data extracted were analysed using SPSS version 11 software. The results were presented in simple descriptive and tabular forms. Forty-one patients, 18(43.90%) males and 23(56.10%) females were studied, ages 12-43 years, average 26.3 + 5 years. Blows/Slaps (65.85%) from assault was the commonest aetiology while bleeding from the ear (73.17%), hearing loss (70.73%) and tympanic membrane perforation (68.29%) were the most frequent presentations. Ear trauma is common and mostly affects the tympanic membrane. Sudden increase in canal pressure from blows/slaps was the major mechanism of injury. Management outcome was good except for few late presenters with compilations.

Amelioration of acute sequelae of blast induced mild traumatic brain injury by N-acetyl cysteine: a double-blind, placebo controlled study

Background

Mild traumatic brain injury (mTBI) secondary to blast exposure is the most common battlefield injury in Southwest Asia. There has been little prospective work in the combat setting to test the efficacy of new countermeasures. The goal of this study was to compare the efficacy of N-acetyl cysteine (NAC) versus placebo on the symptoms associated with blast exposure mTBI in a combat setting.

Methods

This study was a randomized double blind, placebo-controlled study that was conducted on active duty service members at a forward deployed field hospital in Iraq. All symptomatic U.S. service members who were exposed to significant ordnance blast and who met the criteria for mTBI were offered participation in the study and 81 individuals agreed to participate. Individuals underwent a baseline evaluation and then were randomly assigned to receive either N-acetyl cysteine (NAC) or placebo for seven days. Each subject was re-evaluated at 3 and 7 days. Outcome measures were the presence of the following sequelae of mTBI: dizziness, hearing loss, headache, memory loss, sleep disturbances, and neurocognitive dysfunction. The resolution of these symptoms seven days after the blast exposure was the main outcome measure in this study. Logistic regression on the outcome of ‘no day 7 symptoms’ indicated that NAC treatment was significantly better than placebo (OR = 3.6, p = 0.006). Secondary analysis revealed subjects receiving NAC within 24 hours of blast had an 86% chance of symptom resolution with no reported side effects versus 42% for those seen early who received placebo.

Conclusion

This study, conducted in an active theatre of war, demonstrates that NAC, a safe pharmaceutical countermeasure, has beneficial effects on the severity and resolution of sequelae of blast induced mTBI. This is the first demonstration of an effective short term countermeasure for mTBI. Further work on long term outcomes and the potential use of NAC in civilian mTBI is warranted.

Trial Registration

ClinicalTrials.gov NCT00822263

Injuries from combat explosions in Iraq: injury type, location, and severity

INTRODUCTION

Explosions have caused a greater percentage of injuries in Iraq and Afghanistan than in any other large-scale conflict. Improvements in body armour and field medical care have improved survival and changed the injury profile of service personnel. This study's objective was to determine the nature, body region, and severity of injuries caused by an explosion episode in male service personnel.

MATERIALS AND METHODS

A descriptive analysis was conducted of 4623 combat explosion episodes in Iraq between March 2004 and December 2007. The Barell matrix was used to describe the nature and body regions of injuries due to a combat explosion.

RESULTS

A total of 17,637 International Classification of Diseases, Ninth Revision (ICD-9) codes were assigned to the 4623 explosion episodes, with an average of 3.8 ICD-9 codes per episode. The most frequent single injury type was a mild traumatic brain injury (TBI; 10.8%). Other frequent injuries were open wounds in the lower extremity (8.8%) and open wounds of the face (8.2%), which includes tympanic membrane rupture. The extremities were the body regions most often injured (41.3%), followed by head and neck (37.4%) and torso (8.8%).

CONCLUSION

The results of this study support previous observations of TBI as a pre-eminent injury of the wars in Iraq and Afghanistan, with mild TBI as the most common single injury in this large cohort of explosion episodes. The extremities had the highest frequency of injuries for any one body region. The majority of the explosion episodes resulted in more than one injury, and the variety of injuries across nearly every body region and injury type suggests a complex nature of explosion injuries. Understanding the constellation of injuries commonly caused by explosions will assist in the mitigation, treatment, and rehabilitation of the effects of these injuries.

Traumatic tympanic membrane perforations: a study of etiology and factors affecting outcome

OBJECTIVE

The purposes of this study were to determine the factors involved in the spontaneous healing and to profile the various etiologies of traumatic tympanic membrane (TM) perforation.

METHODS

A retrospective review was performed on 729 cases of traumatic TM perforation diagnosed in the emergency department and outpatient clinic from January 2007 to March 2011.

RESULTS

A total 641 patients with traumatic TM perforations were enrolled in the study. The group consisted of 320 male and 321 female patients with a mean age of 33.6 years (3-79 years). The types of trauma included compression injury (554 patients), blast injury (55 patients), and instrumental injury (32 patients). The causes of conflict by a slap or a fist were spouse or lover (52%), parents and sibling (3%), school teachers (4%), schoolmate (12%), state police and prisoner (7%), and blow against the ear during street fight (22%). Of the 641, 137 were lost during follow-up; of the remaining 504, perforations closed spontaneously in 451 (89%), within a mean of 27.4 days. Wet perforations with bloody or watery discharge significantly improved the healing rate (P < .01) and shortened the average perforation closure time (P < .01), as compared with dry perforations. Although the perforation that involved malleus or umbo damage did not significantly affect the healing rate (P > .05), a significantly prolonged closure time (41.6 vs 23.8 days) was observed as compared with no damage. However, the curled edges did not also affect the outcome of spontaneous healing; the healing rate was 91% and 88% (P > .05), and the average closure time was 28.1 and 26.7 days (P > .05), respectively, for with and without curler edges. By perforation size, the overall healing rate was 92% and 54% (P < .01), and the average closure time was 22.8 and 47.3 days (P < .01), respectively, for small and larger perforations. Moreover, 7 patients had neomembrane formation on follow-up, 2 developed cholesteatoma, 1 developed tympanosclerosis, and 1 developed facial paralysis.

CONCLUSION

In our experience, domestic violence and street fight were the most common causes of the traumatic TM perforation. Traumatic TM perforations have excellent prognosis. However, preexisting tympanosclerosis and the perforation that involved malleus or umbo damage could lengthen the healing time of perforation, Wet perforations with bloody or watery discharge accelerate the healing, but the curled edges did not affect the outcome of spontaneous healing.

Wartime spine injuries: understanding the improvised explosive device and biophysics of blast trauma

The improvised explosive device (IED) has been the most significant threat by terrorists worldwide. Blast trauma has produced a wide pattern of combat spinal column injuries not commonly experienced in the civilian community. Unfortunately, explosion-related injuries have also become a widespread reality of civilian life throughout the world, and civilian medical providers who are involved in emergency trauma care must be prepared to manage casualties from terrorist attacks using high-energy explosive devices. Treatment decisions for complex spine injuries after blast trauma require special planning, taking into consideration many different factors and the complicated multiple organ system injuries not normally experienced at most civilian trauma centers. Therefore, an understanding about the effects of blast trauma by spine surgeons in the community has become imperative, as the battlefield has been brought closer to home in many countries through domestic terrorism and mass casualty situations, with the lines blurred between military and civilian trauma. We set out to provide the spine surgeon with a brief overview on the use of IEDs for terrorism and the current conflicts in Iraq and Afghanistan and also a perspective on the biophysics of blast trauma.

A randomised controlled trial comparing spontaneous healing, gelfoam patching and edge-approximation plus gelfoam patching in traumatic tympanic membrane perforation with inverted or everted edges

OBJECTIVE

To compare the outcome of patients with dry traumatic tympanic membrane perforation after spontaneous healing and gelfoam patching with or without perforation edge approximation.

DESIGN

Prospective clinical study.

SETTING

University-affiliated teaching hospital.

PARTICIPANTS

Ninety-one patients with acute dry traumatic tympanic membrane perforation inverted or everted edges were recruited. They were randomly allocated to three groups: spontaneous healing (n=31), gelfoam patching (n=30) and edge-approximation plus gelfoam patching (n=30). Otoscopy and tympanometry were performed before the treatment and at follow-up visits.

MAIN OUTCOME MEASURES

  Healing rate, healing time, ear infection rate and morphological changes during healing process.

RESULTS

The overall healing rate was 85% in the spontaneous healing group, lower than that in the two gelfoam patching groups (97%), but the difference failed to reach a statistical significance (P>0.05). The average healing time was 30 ± 10.1 days in the spontaneous healing group, significantly longer (P<0.01) than that in the other two groups (16 ± 5.6 and 18 ± 4.7 days, respectively). Middle ear infection rate did not differ significantly (7%, 3% and 3%, respectively). Spontaneous healing resulted in formation of scabs at the perforation edges, which was effectively prevented by gelfoam patching.

CONCLUSIONS

Gelfoam patching may facilitate healing of traumatically perforated tympanic membrane. Approximation of folded perforation edges is not necessary in gelfoam patching.

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.

Blast injuries

Health-care providers are increasingly faced with the possibility of needing to care for people injured in explosions, but can often, however, feel undertrained for the unique aspects of the patient's presentation and management. Although most blast-related injuries (eg, fragmentation injuries from improvised explosive devices and standard military explosives) can be managed in a similar manner to typical penetrating or blunt traumatic injuries, injuries caused by the blast pressure wave itself cannot. The blast pressure wave exerts forces mainly at air-tissue interfaces within the body, and the pulmonary, gastrointestinal, and auditory systems are at greatest risk. Arterial air emboli arising from severe pulmonary injury can cause ischaemic complications-especially in the brain, heart, and intestinal tract. Attributable, in part, to the scene chaos that undoubtedly exists, poor triage and missed diagnosis of blast injuries are substantial concerns because injuries can be subtle or their presentation can be delayed. Management of these injuries can be a challenge, compounded by potentially conflicting treatment goals. This Seminar aims to provide a thorough overview of these unique primary blast injuries and their management.