Vestibular and Audiometric Consequences of Blast Injury to the Ear

Leveraging Technology for Vestibular Assessment and Rehabilitation in the Operational Environment: A Scoping Review

INTRODUCTION

The vestibular system, essential for gaze and postural stability, can be damaged by threats on the battlefield. Technology can aid in vestibular assessment and rehabilitation; however, not all devices are conducive to the delivery of healthcare in an austere setting. This scoping review aimed to examine the literature for technologies that can be utilized for vestibular assessment and rehabilitation in operational environments.

MATERIALS AND METHODS

A comprehensive search of PubMed was performed. Articles were included if they related to central or peripheral vestibular disorders, addressed assessment or rehabilitation, leveraged technology, and were written in English. Articles were excluded if they discussed health conditions other than vestibular disorders, focused on devices or techniques not conducive to the operational environment, or were written in a language other than English.

RESULTS

Our search strategy yielded 32 articles: 8 articles met our inclusion and exclusion criteria whereas the other 24 articles were rejected.

DISCUSSION

There is untapped potential for leveraging technology for vestibular assessment and rehabilitation in the operational environment. Few studies were found in the peer-reviewed literature that described the application of technology to improve the identification of central and/or peripheral vestibular system impairments; triage of acutely injured patients; diagnosis; delivery and monitoring of rehabilitation; and determination of readiness for return to duty.

CONCLUSIONS

This scoping review highlighted technology for vestibular assessment and rehabilitation feasible for use in an austere setting. Such technology may be leveraged for prevention; monitoring exposure to mechanisms of injury; vestibular-ocular motor evaluation; assessment, treatment, and monitoring of rehabilitation progress; and return-to-duty determination after vestibular injury.

FUTURE DIRECTIONS

The future of vestibular assessment and rehabilitation may be shaped by austere manufacturing and 3D printing; artificial intelligence; drug delivery in combination with vestibular implantation; organ-on-chip and organoids; cell and gene therapy; and bioprinting.

Vestibular and balance function in veterans with chronic dizziness associated with mild traumatic brain injury and blast exposure

The purpose of this study was to examine vestibular and balance function in individuals with chronic dizziness associated with mTBI/blast. A prospective case-control study design was used to examine ocular motor, vestibular function, and postural stability in veterans with symptoms of dizziness and/or imbalance following an mTBI or blast exposure (n = 77) and a healthy control group (n = 32). Significant group differences were observed for saccadic accuracy, VOR gain during slow harmonic acceleration at 0.01 Hz, cervical vestibular evoked myogenic potentials asymmetry ratio, composite equilibrium score on the sensory organization test, total Dynamic Gait Index score, and gait. The frequency of test abnormalities in participants with mTBI/blast ranged from 0 to 70% across vestibular, ocular motor, and balance/gait testing, with the most frequent abnormalities occurring on tests of balance and gait function. Seventy-two percent of the mTBI/blast participants had abnormal findings on one or more of the balance and gait tests. Vestibular test abnormalities occurred in ~34% of the individuals with chronic dizziness and mTBI/blast, and abnormalities occurred more frequently for measures of otolith organ function (25% for cVEMP and 18% for oVEMP) than for measures of hSCC function (8% for SHA and 6% for caloric test). Abnormal ocular motor function occurred in 18% of the mTBI/blast group. These findings support the need for comprehensive vestibular and balance assessment in individuals with dizziness following mTBI/blast-related injury.

Protective Headgear Attenuates Forces on the Inner Table and Pressure in the Brain Parenchyma During Blast and Impact: An Experimental Study Using a Simulant-Based Surrogate Model of the Human Head

Military personnel sustain head and brain injuries as a result of ballistic, blast, and blunt impact threats. Combat helmets are meant to protect the heads of these personnel during injury events. Studies show peak kinematics and kinetics are attenuated using protective headgear during impacts; however, there is limited experimental biomechanical literature that examines whether or not helmets mitigate peak mechanics delivered to the head and brain during blast. While the mechanical links between blast and brain injury are not universally agreed upon, one hypothesis is that blast energy can be transmitted through the head and into the brain. These transmissions can lead to rapid skull flexure and elevated pressures in the cranial vault, and, therefore, may be relevant in determining injury likelihood. Therefore, it could be argued that assessing a helmet for the ability to mitigate mechanics may be an appropriate paradigm for assessing the potential protective benefits of helmets against blast. In this work, we use a surrogate model of the head and brain to assess whether or not helmets and eye protection can alter mechanical measures during both head-level face-on blast and high forehead blunt impact events. Measurements near the forehead suggest head protection can attenuate brain parenchyma pressures by as much as 49% during blast and 52% during impact, and forces on the inner table of the skull by as much as 80% during blast and 84% during impact, relative to an unprotected head.

Risks of Ear Complaints of Passengers and Drivers While Trains Are Passing Through Tunnels at High Speed: A Numerical Simulation and Experimental Study

Ear complaints induced by interior pressure transients are common experiences for passengers and crew members when high-speed trains are passing through tunnels. However, approaches to assessing the risks of the pressure-related aural discomfort have not been reported until recently. The objective of this study was to evaluate the hazards of interior pressure transients of high-speed train on human ears combining the effects of operation speed and seal index. Moving model tests were conducted to obtain the pressure transients when the model train runs in the tunnel. The recorded data were transformed into the interior pressures by empirical formula. Furthermore, the aural sensations were divided into four levels hierarchically and the range for each level was derived by logistic regression analysis method and represented by three biomechanical metrics. Furthermore, a human middle ear finite element (FE) model was used to simulate its dynamics under the interior pressures. The results indicate that lifting operation speed from 250 km/h to 350 km/h in tunnel will prolong the duration of ear complaints by more than two times whereas improving the seal index from 4 s to 12 s will reduce the incidences of the onset of tinnitus and hearing loss by more than ten times. In addition, the duration of aural comfort shortens from the head car to the tail car against the running direction. It is desirable that enhancing the seal index improve the aural sensations of the passengers and crew members considering the lifting operation speed of high-speed train.

Vestibular Test Patterns in the NICoE Intensive Outpatient Program Patient Population

The National Intrepid Center of Excellence (NICoE), on the campus of Walter Reed National Military Medical Center, was developed to help improve the lives of active duty service members (SMs) with traumatic brain injury (TBI) and comorbid behavioral health (BH) conditions. During the NICoE intensive outpatient program, SM who have all been identified as having some degree of TBI, undergo extensive interdisciplinary evaluations, including comprehensive vestibular assessment. These SMs sometimes present with vestibular symptoms ranging from lightheadedness to vertigo associated with the dual TBI/BH diagnoses, and vestibular testing results reported elsewhere have varied among this population. The study's purpose was to collate the vestibular test results obtained from a sample of the NICoE patients to determine if specific tests have a tendency to be abnormal in these SMs. Results indicate that oculomotor tests, particularly pursuit and saccade, were most often abnormal. The vertical subtests of the pursuit and saccade tests were abnormal more frequently than the horizontal subtests, suggesting that the vertical subtests should be utilized when evaluating the TBI population. Overall, oculomotor tests of vertical pursuit and saccades, as well as tests of central vestibular function, appear useful for detecting neurologic changes in active duty SMs with chronic symptoms after TBI.

Computerized dynamic posturography for evaluating dizziness in patients with scarred orbital content

Our objective was to assess the capability of computerized dynamic posturography (CDP) to evaluate dizziness in blind patients who lack corneoretinal potential. We performed a retrospective analysis of 2 young blind subjects with intraorbital scarring who complained of dizziness and underwent CDP. Tests were carried out at our center for balance disorders using the NeuroCom's EquiTest System version 4.0. CDP demonstrated vestibular dysfunction and revealed it to be severe. We conclude that CDP can serve as a potentially reliable tool for assessing dizziness in blind patients who have no corneoretinal potential.

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.

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.

Traumatic brain injury and vestibular pathology as a comorbidity after blast exposure

Blasts or explosions are the most common mechanisms of injury in modern warfare. Traumatic brain injury (TBI) is a frequent consequence of exposure to such attacks. Although the management of orthopedic, integumentary, neurocognitive, and neurobehavioral sequelae in survivors of blasts has been described in the literature, less attention has been paid to the physical therapist examination and care of people with dizziness and blast-induced TBI (BITBI). Dizziness is a common clinical finding in people with BITBI; however, many US military service members who have been exposed to blasts and who are returning from Iraq and Afghanistan also complain of vertigo, gaze instability, motion intolerance, and other symptoms consistent with peripheral vestibular pathology. To date, few studies have addressed such "vestibular" complaints in service members injured by blasts. Given the demonstrated efficacy of treating the signs and symptoms associated with vestibular pathology, vestibular rehabilitation may have important implications for the successful care of service members who have been injured by blasts and who are complaining of vertigo or other symptoms consistent with vestibular pathology. In addition, there is a great need to build consensus on the clinical best practices for the assessment and management of BITBI and blast-related dizziness. The purpose of this review is to summarize the findings of clinicians and scientists conducting research on the effects of blasts with the aims of defining the scope of the problem, describing and characterizing the effects of blasts, reviewing relevant patients' characteristics and sensorimotor deficits associated with BITBI, and suggesting clinical best practices for the rehabilitation of BITBI and blast-related dizziness.

Ear abuse in school children

Ear abuse in school children is common in low socio-economic strata and is often associated a long-term morbidity in our country. This paper presents a study of 250 such children with discussion. Incidence of ear abuse with long term learning deficit was found to be 18.4%.

Acoustic biast trauma

In this study 26 cases of blast injury to ear were studied. Both ears were affected in 9 cases and therefore the number of ears studied being 35. The audiological findings along with the treatment and a followup of 2 years is presented.We found that mixed deafness was commonest and the sensorineural element of the hearing loss started recovering before conductive element, but recovery slowed down later on and was incomplete in most cases. Approximation of torn fragments of tympanic membrane improved its healing. Vertigo lasting for 1-7 days was present in 46.15% of cases. Only one patient had perilymph fistula which was repaired.

Extended high-frequency audiometry in traumatic tympanic membrane perforations

Air- and bone-conduction audiometry in the frequency ranges 0.125-18 kHz and 0.25-16 kHz respectively were performed in 38 patients with unilateral traumatic tympanic membrane perforation. Sensorineural threshold elevation was found in 16 ears. In nine of these this was permanent and in four restricted to the frequency range > 8 kHz. Both sensorineural threshold elevation and tinnitus (n = 16) diminished with time. A temporary, mean 5 dB, bone-conduction threshold elevation > or = 8 kHz was seen in 26 ears before spontaneous tympanic membrane closure. Closure resulted in a 7-20 dB improvement of air-conduction thresholds in the 0.125-18 kHz range, somewhat less in the upper than in the lower frequencies. A 3 dB mean final conductive hearing loss > 8 kHz was found in these 26 ears approximately 5 months after injury, probably due to scars in the pars tensa at the site of the former perforations. Thirty-seven of 38 perforations had healed at final follow-up examination.

Vestibular findings associated with chronic noise induced hearing impairment

Histological and functional derangements of the vestibular system have been reported in laboratory animals exposed to high levels of noise. However, clinical series describe contradictory results with regard to vestibular disturbances in industrial workers and military personnel suffering from noise induced hearing loss (NIHL). The purpose of the present study was to evaluate vestibular function in a group of subjects with documented NIHL, employing electronystagmography (ENG) and the smooth harmonic acceleration (SHA) test. Subjects were 22 men suffering from NIHL and 21 matched controls. Significantly lower vestibulo-ocular reflex gain (p = 0.05), and a tendency towards decreased caloric responses were found in the study group. No differences in the incidence of vertigo symptoms, spontaneous, positional and positioning nystagmus, directional preponderance and canal paresis in the ENG, or the SHA test phase and asymmetry parameters were observed between the groups. These results demonstrated a symmetrical centrally compensated decrease in the vestibular end organ response which is associated with the symmetrical hearing loss measured in the study group. Statistically significant correlations were found between the average hearing loss, the decrement in the average vestibulo-ocular reflex gain (p = 0.01), and ENG caloric lateralization (p = 0.02). These correlations might indicate a single mechanism for both cochlear and vestibular noise-induced injury. The results imply subclinical, well compensated malfunction of the vestibular system associated with NIHL.