Blast injuries of the ear

[Features of otosurgery in children after blast injuries]

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

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.

Mechanisms and treatment of blast induced hearing loss

The main objective of this study is to provide an overview of the basic mechanisms of blast induced hearing loss and review pharmacological treatments or interventions that can reduce or inhibit blast induced hearing loss. The mechanisms of blast induced hearing loss have been studied in experimental animal models mimicking features of damage or injury seen in human. Blast induced hearing loss is characterized by perforation and rupture of the tympanic membrane, ossicular damage, basilar membrane damage, inner and outer hair cell loss, rupture of round window, changes in chemical components of cochlear fluid, vasospasm, ischemia, oxidative stress, excitotoxicity, hematoma, and hemorrhage in both animals and humans. These histopathological consequences of blast exposure can induce hearing loss, tinnitus, dizziness, and headache. The pharmacological approaches to block or inhibit some of the auditory pathological consequences caused by blast exposure have been developed with antioxidant drugs such as 2,4-disulfonyl α-phenyl tertiary butyl nitrone (HXY-059, now called HPN-07) and N-acetylcysteine (NAC). A combination of antioxidant drugs (HPN-07 and NAC) was administered to reduce blast induced cochlear damage and hearing loss. The combination of the antioxidant drugs can prevent or treat blast induced hearing loss by reducing damage to the mechanical and neural component of the auditory system. Although information of the underlying mechanisms and treatment of blast induced hearing loss are provided, further and deep research should be achieved due to the limited and controversial knowledge.

Otologic considerations of blast injury

The ear by design is exquisitely sensitive to barotrauma. As a result, it is typically the first organ affected in primary blast injury. The most common symptoms encountered include hearing loss, ringing, and drainage. In severe cases, the highest priority is appropriately directed toward diagnosis and treatment of life-threatening injuries; however, injury to the ear is missed frequently. With simple screening procedures, limited management, and appropriate otolaryngologic referral, acute and long-term morbidity can be averted for both critical and noncritical patients. The article provides an overview of blast mechanics and pathophysiology. It details various blast-related injuries to the external, middle, and inner ear. Standard of care assessment and management strategies are presented for acute and late otologic sequelae of the blast-injured patient.

Bomb blast injury: effect on middle and inner ear

OBJECTIVE

To study the symptomatology, clinical findings and the effects of blast injury on middle and inner ear in survivors of bomb blast. Settings City of Mumbai, India.

METHODS

The study group consisted of 52 patients exposed to the bomb blast that occurred on 25th August 2003.

RESULT AND ANALYSIS

The distance of the victim from the blast site has no major infiuence in producing effects on middle and inner ear in our study of the surviving individuals. Rupture of the tympanic membrane occurs due to the positive wave but both everted and inverted edges can be found in multiple perforations of the tympanic membrane.

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

BACKGROUND

Tympanic membrane perforation is the most common primary blast injury in the current conflicts and occurs in approximately one tenth of service members wounded by combat explosions. We wanted to determine the severity of perforation and its effect on hearing and combat readiness.

METHODS

This analysis is a retrospective study of US service members injured in combat explosions in Afghanistan or Iraq and treated at our institution between March 2003 and July 2006. Data captured included location and grade of perforation, symptoms, healing rates, audiogram results, need for hearing aids, and loss of eligibility for military service.

RESULTS

Of 436 explosion-wounded patients admitted to our facility, 65 (15%) patients had tympanic membrane perforation diagnosed by the otolaryngology service. A total of 97 tympanic membrane perforations occurred among 65 patients. The average surface area involved was 41% +/- 32% (right) and 35% +/- 34% (left). More than one third of perforations were grade 4. The most common locations were central and anterior-inferior. Most (83%) patients reported symptoms, most commonly diminished hearing (77%) and tinnitus (50%). Outcome data were available for 77% of perforations. Spontaneous healing occurred in 48%. The remainder (52%) had surgical intervention. The most common audiogram abnormality was mild high frequency hearing loss. Ultimately, three patients (5%) required hearing aids and one discharge from military service.

CONCLUSIONS

Tympanic membrane perforation occurs in 16% of explosion-injured patients. Most patients are symptomatic and many have large perforations requiring operative intervention. Long-term hearing loss is uncommon but does impact ability to continue military service.

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%.

Explosions and blast injuries

Powerful explosions have the potential to inflict many different types of injuries on victims, some of which may be initially occult. Flying debris and high winds commonly cause conventional blunt and penetrating trauma. Injuries caused by blast pressures alone result from complex interactions on living tissues. Interfaces between tissues of different densities or those between tissues and trapped air result in unique patterns of organ damage. These challenge out-of-hospital personnel, emergency physicians, and trauma surgeons to specifically seek evidence of these internal injuries in individuals with multiple trauma, adjust management considerations to avoid exacerbation of life-threatening problems caused by the blast wave itself, and ensure appropriate disposition of these patients in possible mass-casualty situations. Knowledge of the potential mechanisms of injury, early signs and symptoms, and natural courses of these problems will greatly aid the management of blast-injured patients.

Patterns of hearing loss in non-explosive blast injury of the ear

A prospective study of hearing loss in 120 cases with non-explosive blast injury of the ear, gathered over a six-year period, is presented. Thirty-three (27.5 per cent) patients had normal hearing, 57 (47.5 per cent) conductive hearing loss, 29 (24.2 per cent) mixed loss and one (0.8 per cent) had pure sensorineural loss. The severity of conductive hearing loss correlated with the size of the eardrum perforation; only a marginal difference was found between water and air pressure injuries, with respect to this type of hearing loss. Of all locations, perforations involving the posterior-inferior quadrant of the eardrum were associated with the largest air-bone gap. Audiometric assessment revealed that none of the patients suffered ossicular chain damage. Three patterns of sensorineural hearing loss were identified: a dip at a single frequency, two separate dips, and abnormality of bone conduction in several adjacent high frequencies. Involvement of several frequencies was associated with a more severe hearing loss than a dip in a single frequency. Healing of the perforation was always accompanied by closure of the air-bone gap, while the recovery of the sensorineural hearing loss was less favourable.

Impulse noise trauma during army weapon firing

A 100 infanty personnel firing modern weapons such as the Anti Tank Guided Missile, 106mm Recoiless Gun (RCL), 84mm Rocket Launcher (RL) and 81mm Mortar were studied for the effect of impulse noise on the ear and the evolution of the Temporary Threshold Shift (TTS), Recovery Time (RT) and Permanent Threshold Shift (PTS) was traced.

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.

Blast injury of the ear: an overview and guide to management

Blast injury is uncommon in many parts of the world but sporadic cases occur. The ear is particularly susceptible to damage and easily forgotten in patients with multiple injuries. The aim of this review article is to draw together the more important aspects of blast ear injury for those who are unfamiliar with it and to serve as a reminder of the problems to others. It covers the interactions of blast waves with the ear giving a summary of the mechanisms and types of injury. The management of blast-related injuries is discussed.

Blast injury of the auditory system: a review of the mechanisms and pathology

Blast injury of the auditory system is uncommon and our knowledge incomplete. This article reviews the literature to date giving an account of the interactions of blast waves with the ear, the mechanisms of injury, the pathology, the clinical features, and an outline of management principles.

Spontaneous healing of traumatic tympanic membrane perforations in man: a century of experience

Widespread controversy exists concerning the treatment of traumatic tympanic membrane perforations. To elucidate the issue, a reference value for the rate of spontaneous tympanic membrane closure in man, to which the healing rates following different techniques of early surgical repair should be compared, was established on the basis of a review of more than 500 texts covering a century's literature on the traumatically perforated tympanic membrane. The spontaneous healing rate appeared to be close to 80 (78.7 per cent) in 760 evaluable cases of traumatic tympanic membrane perforations of all sorts diagnosed within 14 days post injury. A relative, causal-related variation of spontaneous healing could be demonstrated, and a pathogenetic classification of direct traumatic tympanic membrane perforations into ruptures induced by air-pressure changes, heat or corrosives, solids, and water pressures, is of proved clinical value and may have medico-legal validity. There is an obvious need for clinically controlled studies on the spontaneous healing of all kinds of traumatic perforations of the tympanic membrane in humans, and important elements in the design of future studies are advocated.

Blast injuries of the ear as a result of the Peterborough lorry explosion: 22 March 1989

The incidence of blast trauma to the ears in significant numbers is relatively rare in peace time. This paper outlines the results and management of twenty patients injured as a result of the outside explosion of 800 kg of high explosives in Peterborough on 22 March 1989.

Damage of the auditory system associated with acute blast trauma

This paper reviews the results of several studies on the effects of blast wave exposure on the auditory system of the chinchilla, the pig, and the sheep. The chinchillas were exposed at peak sound pressure levels of approximately 160 dB under well-controlled laboratory conditions. A modified shock tube was used to generate the blast waves. The pigs and sheep were exposed under field conditions in an instrumented hard-walled enclosure. Blast trauma was induced by the impact of a single explosive projectile. The peak sound pressure levels varied between 178 and 209 dB. All animals were killed immediately following exposure, and their temporal bones were removed for fixation and histologic analysis using light microscopy and scanning electron microscopy. Middle ears were examined visually for damage to the conductive system. There were well-defined differences in susceptibility to acoustic trauma among species. However, common findings in each species were the acute mechanical fracture and separation of the organ of Corti from the basilar membrane, and tympanic membrane and ossicular failure.

Blast injury of the ear: historical perspective

Blast injury of the ear is rarely encountered by the practicing otolaryngologist. The recent world literature on this entity is reviewed. Symptoms, patterns of injury, and clinical course are highlighted and should form the basis of management under acute and chronic circumstances.

Auditory brainstem evoked potentials in blast injury

Blast injury typically consists of a mixed conductive and sensorineural hearing loss. The sensorineural component includes temporary as well as permanent threshold elevations. Auditory brainstem evoked potentials (ABEP) are sensitive to functional changes in various levels along the auditory pathway. ABEP were recorded from 37 survivors of blasts and latency measures were correlated with clinical findings. Prolongation of peak latencies was correlated with the conductive component of blast-induced hearing loss, as well as with the TTS component of the sensorineural impairment. No central effects of blast on the auditory system were detected. In addition to their objectivity, ABEP hold the promise of differentiating between the permanent and temporary effects of blast on hearing.

The ENT problems following the Birmingham bombings

The ENT problems following the Birmingham bombings of 1974 are presented. It is during the positive phase of bomb blast that the tympanic membrane ruptures. Spalling is a likely explanation for the mechanism of rupture of the tympanic membrane specially in large perforations. Tympanic membrane defects involving 80 per cent of the surface area of the drumhead or more persisted, whereas those involving less than 80 per cent healed with conservative treatment. The majority of perforations (81.4 per cent) healed spontaneously, with a three-layered membrane. A month should be allowed for the healing of every 10 per cent loss of the surface area of the drumhead. During surgical repair of persistent perforations, the malleus handle was found to be on a deeper plain than the long process of the incus. Tympanic membrane perforations did not protect the inner ear, the sensorineural deafness producing either a high tone or a flat loss. One in four of the victims seen in the hospital complained of deafness. A patient who suffered blast injuries to the lung also developed cord palsy.

Early repair of blast ruptures of the tympanic membrane

A method and results of early repair of blast rupture of the tympanic membrane in 24 selected cases, where flaps and/or free edges of the torn eardrum could be detected by examination with the operating microscope, are presented. By reversion of the flaps and approximation of the edges, the perforation was closed or significantly diminished. This ensured the healing of the tympanic membrane in all cases within days instead of months. No complications were noted during a subsequent two to three-years' follow-up. The improved hearing was stable.

Blast injury to sensory hairs: a study in the guinea pig using scanning electron microscopy

Guinea pigs were exposed to a blast (maximum 1.0 kg/cm2) of nitrous gas for 0.2 s through the external auditory canal. Then, they were either killed immediately, 1 day, 3 days, 1 week, 2 weeks, or 4 weeks after exposure to the blast. The morphological changes of the cochlear sensory hairs were examined by means of a scanning electron microscope. Changes in the sensory hairs of the animals exposed to the blast for 1 s were examined in the same manner. The results of these experiments show that sensory hairs of the basal and the second turns were damaged more markedly than those of the third and subsequent turns. Outer sensory hairs were damaged more than inner ones.