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Hearing Impairment and Traumatic Brain Injury among Soldiers: Special Considerations for the Audiologist

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The increased use of explosive devices and mines in warfare and excessive noise of weapons has created an unprecedented amount of auditory dysfunction among soldiers. Blast-related injuries may damage the auditory processing and/or balance centers resulting in hearing loss, dizziness, tinnitus, and/or central auditory processing disorders. Some also lead to traumatic brain injury (TBI), postconcussive syndrome (PCS), and/or posttraumatic stress disorder. Some PCS symptoms such as dizziness, loss of balance, hearing difficulty, and noise sensitivity also can signify auditory or vestibular dysfunction and should not be obscured with the PCS package. This article provides information about the mechanisms of blast injury with emphasis on auditory dysfunction and TBI. Audiologists must be prepared to identify those at risk for TBI or mental health problems and adapt audiologic clinical practices to this population. An interdisciplinary comprehensive evaluation of peripheral, central, and vestibular components of the auditory system should be employed in patients with TBI to ensure that auditory dysfunction is accurately diagnosed and that appropriate rehabilitation can be performed.
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... Although many patients fully recover from mTBI, also known as concussion, within a few weeks to months, estimates indicate that between 27% and 50% of patients experience chronic neurological issues such as headaches, poor concentration and memory, and sensory disturbances (Ryan & Warden, 2003;Lannsjö et al. 2009;Hiploylee et al. 2017;Voormolen et al. 2018). In the auditory domain, the subjective complaints of these patients often include sensitivity to noise (Callahan et al. 2018;Callahan & Storzbach 2019), greater difficulty understanding speech in noise backgrounds and reverberation, and problems with recalling spoken information and attending to long conversations with those with multiple speaking partners, even when hearing thresholds remain within clinically normal limits (Myers et al. 2009;Remenschneider et al. 2014;Saunders et al. 2015;Brungart et al. 2016;Bressler et al. 2017;Gallun et al. 2017). However, objective measures that corroborate these subjective auditory symptoms are presently lacking. ...
... Given the complex and widespread nature of damage to auditory and supra-auditory structures following blast exposure, it is not surprising that chronic auditory symptoms may result (Myers et al. 2009;Gallun et al. 2017). In fact, some evidence suggests that blast-related TBIs may be more likely to effect auditory function compared to other TBI etiologies (Tun et al. 2009;Oleksiak et al. 2012), and that blast exposure may lead to chronic auditory disturbances even in the absence of an official TBI diagnosis Gallun et al. 2016;Hickman et al. 2018). ...
... The latter is particularly true in the case of blast-exposed Veterans who may be less likely to report mTBI symptoms in theater, and thus less likely to receive a TBI diagnosis (Magnuson & Ling 2018). Though most research to date on the auditory effects of blast exposure has focused on peripheral consequences, specifically conductive and sensorineural hearing loss (Pratt et al. 1985;Fausti et al. 2009;Cho et al. 2013;Remenschneider et al. 2014), many VA audiologists have reported increases in the number of recently enrolled Veterans seeking help for auditory problems despite normal peripheral hearing sensitivity, many of whom report having sustained blast exposure during their military service (Myers et al. 2009;Brungart et al. 2016;. Available research on the chronic central auditory consequences of blast exposure indicates that several processing domains may be affected including behaviorally measured deficits in auditory pattern recognition , temporal resolution (Gallun et al. 2016), spatial localization especially in complex listening environments (Brungart et al. 2016;Kubli et al. 2018), and poor understanding of degraded speech including speech signals presented with competing sounds (Dennis 2009;Saunders et al. 2015), at rapid speaking rates and in reverberation (Brungart et al. 2016;Papesh et al. 2019). ...
Article
Objectives: Veterans who have been exposed to high-intensity blast waves frequently report persistent auditory difficulties such as problems with speech-in-noise (SIN) understanding, even when hearing sensitivity remains normal. However, these subjective reports have proven challenging to corroborate objectively. Here, we sought to determine whether use of complex stimuli and challenging signal contrasts in auditory evoked potential (AEP) paradigms rather than traditional use of simple stimuli and easy signal contrasts improved the ability of these measures to (1) distinguish between blast-exposed Veterans with auditory complaints and neurologically normal control participants, and (2) predict behavioral measures of SIN perception. Design: A total of 33 adults (aged 19-56 years) took part in this study, including 17 Veterans exposed to high-intensity blast waves within the past 10 years and 16 neurologically normal control participants matched for age and hearing status with the Veteran participants. All participants completed the following test measures: (1) a questionnaire probing perceived hearing abilities; (2) behavioral measures of SIN understanding including the BKB-SIN, the AzBio presented in 0 and +5 dB signal to noise ratios (SNRs), and a word-level consonant-vowel-consonant test presented at +5 dB SNR; and (3) electrophysiological tasks involving oddball paradigms in response to simple tones (500 Hz standard, 1000 Hz deviant) and complex speech syllables (/ba/ standard, /da/ deviant) presented in quiet and in four-talker speech babble at a SNR of +5 dB. Results: Blast-exposed Veterans reported significantly greater auditory difficulties compared to control participants. Behavioral performance on tests of SIN perception was generally, but not significantly, poorer among the groups. Latencies of P3 responses to tone signals were significantly longer among blast-exposed participants compared to control participants regardless of background condition, though responses to speech signals were similar across groups. For cortical AEPs, no significant interactions were found between group membership and either stimulus type or background. P3 amplitudes measured in response to signals in background babble accounted for 30.9% of the variance in subjective auditory reports. Behavioral SIN performance was best predicted by a combination of N1 and P2 responses to signals in quiet which accounted for 69.6% and 57.4% of the variance on the AzBio at 0 dB SNR and the BKB-SIN, respectively. Conclusions: Although blast-exposed participants reported far more auditory difficulties compared to controls, use of complex stimuli and challenging signal contrasts in cortical and cognitive AEP measures failed to reveal larger group differences than responses to simple stimuli and easy signal contrasts. Despite this, only P3 responses to signals presented in background babble were predictive of subjective auditory complaints. In contrast, cortical N1 and P2 responses were predictive of behavioral SIN performance but not subjective auditory complaints, and use of challenging background babble generally did not improve performance predictions. These results suggest that challenging stimulus protocols are more likely to tap into perceived auditory deficits, but may not be beneficial for predicting performance on clinical measures of SIN understanding. Finally, these results should be interpreted with caution since blast-exposed participants did not perform significantly poorer on tests of SIN perception.
... The potential for tinnitus and mental health status to reinforce one another in powerful and negative ways was obvious to patients and an interest of researchers for several decades [6][7][8][9][10][11][12]. Studies relating traumatic exposures to tinnitus suggested that memories and traumarelated hyperarousal conspired to exacerbate not only tinnitus distress but related sound tolerance issues [7,10,13,14]. Traumatic onset was specified by Kreuzer et al. [15] as exacerbating tinnitus "burden". ...
... The links between exposures and subsequent symptoms were apparent centuries ago [19]. Given the likelihood that violent exposures include high sound pressure levels, head trauma, and toxins in the environment, there would be a strong possibility that sensory disorders related to hearing would result from exposures that might cause PTSD [14,22]. Here, we consider the consequences of tinnitus playing the part of an aversive auditory event and memory derived from trauma. ...
Article
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Events linked to post-traumatic stress disorder (PTSD) influence psychological and physical health through the generation, exacerbation, and maintenance of symptoms such as anxiety, hyperarousal, and avoidance. Depending upon circumstance, traumatic events may also contribute to the onset of tinnitus, post-traumatic headache, and memory problems. PTSD should be considered a psychological injury, andwhile tinnitus is a symptom, its onset and sound quality may be connected in memory to the injury, thereby evincingthe capacity to exacerbate the trauma’s effects. The myriad attributes, psychological and mechanistic, shared by tinnitus and PTSD offer tinnitus investigators the opportunity to draw from the rich and long-practiced strategies implemented for trauma counseling. Mechanisms and interventions understood through the lens of traumatic exposures may inform the clinical management of tinnitus disorder, and future studies may assess the effect of PTSD intervention on co-occurring conditions. This brief summary considered literature from both the hearing and trauma disciplines, with the goal of reviewing mechanisms shared between tinnitus and PTSD, as well as clinical reports supporting mutual reinforcement of both their symptoms and the effects of therapeutic approaches.
... Biomechanical factors during blast injury might induce differential effects on the hand and whisker networks of the cerebellum that are defined by different ascending pathways. This is supported by studies indicating a higher sensitivity of the vestibular nucleus to shock-wave induced blast injuries in humans and rats [46][47][48] , although we cannot confirm a similar effect since we did not include behavioral tests to verify balance and coordination deficits in our experimental animals. Nevertheless, it is possible that an adjacent structure to the vestibular fibers, the trigeminal tract, may also have a higher sensitivity to the blast-waves. ...
Article
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Understanding the mechanisms underlying traumatic neural injury and the sequelae of events in the acute phase is important for deciding on the best window of therapeutic intervention. We hypothesized that evoked potentials (EP) recorded from the cerebellar cortex can detect mild levels of neural trauma and provide a qualitative assessment tool for progression of cerebellar injury in time. The cerebellar local field potentials evoked by a mechanical tap on the hand and collected with chronically implanted micro-ECoG arrays on the rat cerebellar cortex demonstrated substantial changes both in amplitude and timing as a result of blast-wave induced injury. The results revealed that the largest EP changes occurred within the first day of injury, and partial recoveries were observed from day-1 to day-3, followed by a period of gradual improvements (day-7 to day-14). The mossy fiber (MF) and climbing fiber (CF) mediated components of the EPs were affected differentially. The behavioral tests (ladder rung walking) and immunohistological analysis (calbindin and caspase-3) did not reveal any detectable changes at these blast pressures that are typically considered as mild (100-130 kPa). The results demonstrate the sensitivity of the electrophysiological method and its use as a tool to monitor the progression of cerebellar injuries in longitudinal animal studies.
... [9][10][11] The most common auditory complaints among these veterans include increased sensitivity to noise, poor speech understanding in the setting of competing background noise, difficulty understanding rapid speech, problems understanding speech on the telephone, difficulty following conversations among groups of people, poor recall of auditory information, and auditory fatigue. 5,6,9,[12][13][14][15][16] Hearing problems often persist in spite of normal pure-tone hearing sensitivity, suggesting a central rather than peripheral locus of dysfunction. This assumption is corroborated by recent work showing that between 20% and 40% of veterans exposed to high-intensity blasts demonstrate abnormal performance on behavioral and electrophysiological assessments of the central auditory system. ...
Article
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Many military Service Members and Veterans who have been exposed to high-intensity blast waves suffer from traumatic brain injury (TBI), resulting in chronic auditory deficits despite normal hearing sensitivity. The current study sought to examine the neurological cause of this chronic dysfunction by testing the hypothesis that blast exposure leads to impaired filtering of sensory information at brainstem and early cortical levels. Groups of blast-exposed and non-blast-exposed participants completed self-report measures of auditory and neurobehavioral status, auditory perceptual tasks involving degraded and competing speech stimuli, and physiological measures of sensory gating, including prepulse inhibition and habituation of the acoustic startle reflex and electrophysiological assessment of a paired-click sensory gating paradigm. Blast-exposed participants showed significantly reduced habituation to acoustic startle stimuli and impaired filtering of redundant sensory information at the level the auditory cortex. Multiple linear regression analyses revealed that poorer sensory gating at the cortical level was primarily influenced by a diagnosis of TBI, while reduced habituation was primarily influenced by a diagnosis of posttraumatic stress disorder. A statistical model was created including cortical sensory gating and habituation to acoustic startle, which strongly predicted performance on a degraded speech task. These results support the hypothesis that blast exposure impairs central auditory processing via impairment of neural mechanisms underlying habituation and sensory gating.
... Secondary damage may occur due to ischemia and a cytotoxic cascade leading to cell deoxygenation and eventual death [36]. Injuries to the olfactory, oculomotor, optic, and acoustic nerves resulting from direct contact with the skull are also common [37]. ...
Article
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Purpose of review: This review investigates the relationship between sensory sensitivity and traumatic brain injury (TBI), and the role sensory sensitivity plays in chronic disability. Recent findings: TBI is a significant cause of disability with a range of physical, cognitive, and mental health consequences. Sensory sensitivities (e.g., noise and light) are among the most frequently reported, yet least outwardly recognizable symptoms following TBI. Clinicians and scientists alike have yet to identify consistent nomenclature for defining noise and light sensitivity, making it difficult to accurately and reliably assess their influence. Noise and light sensitivity can profoundly affect critical aspects of independent function including communication, productivity, socialization, cognition, sleep, and mental health. Research examining the prevalence of sensory sensitivity and evidence for the association of sensory sensitivity with TBI is inconclusive. Evidence-based interventions for sensory sensitivity, particularly following TBI, are lacking.
Article
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Introducción: En el año 2002 un artefacto explosivo improvisado estalló sobre la población civil afrocolombiana refugiada en una iglesia y generó una masacre. Los sobrevivientes presentaron importantes afectaciones en la salud, sin un estudio completo hasta la fecha. Objetivo: Establecer el perfil de salud auditiva en la comunidad de sobrevivientes a la masacre de Bojayá, Chocó. Métodos: A partir de evaluaciones clínicas audiológicas con anamnesis, otoscopia, audiometría, logoaudiometría e impedanciometría en 61 personas supervivientes, se efectuó un estudio descriptivo incluyendo variables sociodemográficas, factores de riesgo, signos y síntomas auditivos, y diagnósticos audiológicos. Resultados: Un 72,13 % de los participantes fueron mujeres. Además de la exposición al estallido de artefacto explosivo improvisado, que les afectó tanto en recinto cerrado (78,69 %), como en exteriores adyacentes (3,28 %) o ubicaciones más distantes; los principales factores de riesgo auditivo encontrados fueron la infección de oído previa (26,87 %). Un 70,49 % sufría de tinnitus y 14,75 % de vértigo. El 81,97 % de sobrevivientes (n = 50) presentaron alteraciones en su audición, sin estudio previo. Un 81 % de quienes se encontraron con algún grado de hipoacusia, reportaban el antecedente de exposición al estallido dentro del espacio cerrado de la iglesia. Conclusiones: El perfil de salud auditiva de la comunidad de sobrevivientes a la masacre de Bojayá, Chocó, se caracterizó por la presencia de dificultades auditivas, tinnitus, otalgia, vértigo, antecedentes de trauma acústico y perforaciones timpánicas. El principal diagnóstico encontrado fue hipoacusia conductiva bilateral.
Article
Objective: To examine the association between hearing impairment and cognitive function after traumatic brain injury (TBI). Setting: A total of 18 level I trauma centers throughout the United States in the Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) study. Participants: From February 2014 to June 2018, a total of 2697 participants with TBI were enrolled in TRACK-TBI. Key eligibility criteria included external force trauma to the head, presentation to a participating level I trauma center, and receipt of a clinically indicated head computed tomographic (CT) scan within 24 hours of injury. A total of 1267 participants were evaluated in the study, with 216 participants with hearing impairment and 1051 participants without hearing impairment. Those with missing or unknown hearing status or cognitive assessment were excluded from analysis. Design: Prospective, observational cohort study. Main measures: Hearing impairment at 2 weeks post-TBI was based on self-report. Participants who indicated worse hearing in one or both ears were defined as having hearing impairment, whereas those who denied worse hearing in either ear were defined as not having hearing impairment and served as the reference group. Cognitive outcomes at 6 months post-TBI included executive functioning and processing speed, as measured by the Trail Making Test (TMT) B/A and the Wechsler Adult Intelligence Scale, Fourth Edition, Processing Speed Index subscale (WAIS-IV PSI), respectively. Results: TBI-related hearing impairment had a small but significantly greater TMT B/A ratio than without TBI-related hearing impairment: mean difference (B) = 0.25; 95% CI, 0.07 to 0.43; P = .005. No significant mean differences on WAIS-IV PSI scores were found between participants with and without TBI-related hearing impairment: B = 0.36; 95% CI, -2.07 to 2.60; P = .825. Conclusion: We conclude that TBI-related hearing impairment at 6 months postinjury was significantly associated with worse executive functioning but not cognitive processing speed.
Research
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Salud auditiva en víctimas afrocolombianas del conflicto armado, sobrevivientes de artefacto explosivo improvisado Hearing health in Afro-Colombian victims of the armed conflict, survivors of improvised explosive device Daisy Mariana Moreno-Martínez1* https://orcid.org/0000-0003-1753-1230 Zulma Consuelo Urrego-Mendoza1 https://orcid.org/0000-0003-1732-4725 1Universidad Nacional de Colombia, Facultad de Medicina, Grupo de Investigación en Violencia y Salud. Bogotá, Colombia. *Autor para la correspondencia. Correo electrónico: dammorenoma@unal.edu.co RESUMEN Introducción: En el año 2002 un artefacto explosivo improvisado estalló sobre la población civil afrocolombiana refugiada en una iglesia y generó una masacre. Los sobrevivientes presentaron importantes afectaciones en la salud, sin un estudio completo hasta la fecha. Objetivo: Establecer el perfil de salud auditiva en la comunidad de sobrevivientes a la masacre de Bojayá, Chocó. Métodos: A partir de evaluaciones clínicas audiológicas con anamnesis, otoscopia, audiometría, logoaudiometría e impedanciometría en 61 personas supervivientes, se efectuó un estudio descriptivo incluyendo variables sociodemográficas, factores de riesgo, signos y síntomas auditivos, y diagnósticos audiológicos. Resultados: Un 72,13 % de los participantes fueron mujeres. Además de la exposición al estallido de artefacto explosivo improvisado, que les afectó tanto en recinto cerrado (78,69 %), como en exteriores adyacentes (3,28 %) o ubicaciones más distantes; los principales factores de riesgo auditivo encontrados fueron la infección de oído previa (26,87 %). Un 70,49 % sufría de tinnitus y 14,75 % de vértigo. El 81,97 % de sobrevivientes (n = 50) presentaron alteraciones en su audición, sin estudio previo. Un 81 % de quienes se encontraron con algún grado de hipoacusia, reportaban el antecedente de exposición al estallido dentro del espacio cerrado de la iglesia. Conclusiones: El perfil de salud auditiva de la comunidad de sobrevivientes a la masacre de Bojayá, Chocó, se caracterizó por la presencia de dificultades auditivas, tinnitus, otalgia, vértigo, antecedentes de trauma acústico y perforaciones timpánicas. El principal diagnóstico encontrado fue hipoacusia conductiva bilateral. Palabras clave: traumatismos por explosión; conflictos armados; pérdida auditiva; grupo de ascendencia continental africana; audiología. ABSTRACT Introduction: In 2002 an improvised explosive device exploded over a church with Afro-Colombian civilians sheltering there, generating a massacre. The survivors presented important health problems without a complete study to date. Objective: To establish the hearing health profile in the community of survivors of the "Bojayá Massacre", Chocó. Methods: Based on clinical audiological evaluations with anamnesis, otoscopy, audiometry, speech audiometry and impedance in 61 survivors, a descriptive study was carried out including sociodemographic variables, risk factors, auditory signs and symptoms, and audiological diagnoses. Results: 72,13 % of the participants were women. In addition to exposure to the explosion of an improvised explosive device, which affected indoors (78, 69 %), and in adjacent outdoors (3,28 %) or more distant locations, the main auditory risk factors found were previous infection of ears (26,87 %). 70,49 % suffered from tinnitus and 14,75 % from vertigo. 81,97 % of survivors (n=50) presented alterations in their hearing, without previous study. 81 % of those who encountered some degree of hearing loss reported a history of exposure to the blast within the closed space of the church. Conclusions: The hearing health profile of the community of survivors of the Bojayá massacre, Chocó, was characterized by the presence of hearing difficulties, tinnitus, earache, vertigo, a history of acoustic trauma, and tympanic perforations. The main diagnosis found was bilateral conductive hearing loss. Keywords: explosion injuries; armed conflict; hearing loss; african continental ancestry group; audiology.
Article
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Purpose A growing body of evidence suggests that military service members and military veterans are at risk for deficits in central auditory processing. Risk factors include exposure to blast, neurotrauma, hazardous noise, and ototoxicants. We overview these risk factors and comorbidities, address implications for clinical assessment and care of central auditory processing deficits in service members and veterans, and specify knowledge gaps that warrant research. Method We reviewed the literature to identify studies of risk factors, assessment, and care of central auditory processing deficits in service members and veterans. We also assessed the current state of the science for knowledge gaps that warrant additional study. This literature review describes key findings relating to military risk factors and clinical considerations for the assessment and care of those exposed. Conclusions Central auditory processing deficits are associated with exposure to known military risk factors. Research is needed to characterize mechanisms, sources of variance, and differential diagnosis in this population. Existing best practices do not explicitly consider confounds faced by military personnel. Assessment and rehabilitation strategies that account for these challenges are needed. Finally, investment is critical to ensure that Veterans Affairs and Department of Defense clinical staff are informed, trained, and equipped to implement effective patient care.
Conference Paper
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Este estudio descriptivo tiene el objeto de establecer el perfil de salud auditiva en la comunidad de víctimas del conflicto armado sobrevivientes a la llamada “Masacre de Bojayá” y se desarrolla en el marco del posacuerdo vivido en Colombia actualmente y a raíz de las secuelas evidenciadas en la población del municipio de Bojayá, Chocó tras los actos de violencia sucedidos en el año 2002, más específicamente la explosión de un cilindro bomba que concluyó en la muerte, desplazamiento y victimización la mayoría de población, junto a graves afectaciones de salud física y mental, entre ellas la pérdida auditiva y factores concomitantes a dicha dificultad.
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High‐frequency (8 to 20 kHz) hearing sensitivity was compared in thirty‐six, 20 to 29‐year‐old military veterans with histories of steady‐state or impulsive noise exposure. Threshold shifts were prominent for the steady‐state noise subjects from 13 to 20 kHz. Mean thresholds from 8 through 12 kHz were maximally 20 dB poorer than a sample of young adult normals. Audiometric configurations for this group were generally smooth and symmetrical above 8000 Hz. For the impulsive noise group, substantial shifts in sensitivity were seen from 2 to 20 kHz and the high‐frequency audiometric configurations were often jagged and/or asymmetrical. The variability of subjects in this group was greater than that seen in the steady‐state noise exposed sample. Several case studies are presented to illustrate these characteristics. Measurement of auditory sensitivity from 8 to 20 kHz extends the mapping of basal cochlear function, providing information which often is not predictable from conventional audiometric measurement. This additional information provides for more comprehensive inter‐ and intra‐subject comparison of the degree and extent of threshold changes present.
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Describes mild traumatic brain injury (TBI) as a traumatically induced physiological disruption of brain function manifested by at least one of the following: (1) any period of loss of consciousness, (2) any loss of memory for events immediately before or after the accident, (3) any alteration in mental state at the time of the accident, and (4) focal neurological deficit(s) that may or may not be transient. Severity of injury in mild TBI does not exceed the following: (1) loss of consciousness of 30 min or less, (2) after 30 min, an initial Glasgow Coma Scale of 13-25, and (3) posttraumatic amnesia not greater than 24 hrs. (PsycINFO Database Record (c) 2006 APA, all rights reserved)