Background Blast injuries in modern warfare are common, and the ear is often affected as it is an effective pressure transducer. This study aimed to evaluate military blast injuries of the ear.
Methods From May 2002 to October 2014, all patients referred to two military hospitals near Paris, France following exposure to massive explosions were analysed.
Results Among the 41 patients (82 ears), 36 of them reported tinnitus, 25 hearing loss, 14 earache and 8 vertigo. It was noted that 44% of the patients had tympanic membrane perforations and that this was bilateral in two-thirds of the cases. The hearing loss in 29% of the cases was pure sensorineural, in 55% it was mixed and in 15% it was a pure conductive hearing loss. There was no correlation between the impact of middle ear lesions and the severity of the inner ear injury. Three patients had a pharyngolaryngeal blast injury detected on the battlefield associated with blast lung injury, but only two of them had tympanic perforations. Nine tympanoplasty procedures were performed, of which 44% succeeded in sealing the perforation.
Conclusions Blast injuries of the ear are characterised by significant functional signs and are not correlated to otoscopic examinations. Sensorineural hearing loss is almost immediately final. When deciding on initial management, the status of the tympanic membrane does not provide any information about the risk of a primary blast injury of the lung; laryngeal nasofibroscopy seems a more relevant screening test.
- tympanic membrane perforation
- hearing loss
- inner ear
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Blast injuries of the ear are characterised by significant functional signs and are not correlated to otoscopic examinations.
Sensorineural hearing loss is almost immediately final.
The status of the tympanic membrane does not provide any information about the risk of primary blast injury of the lung; laryngeal nasofibroscopy is more useful.
Although hearing protection seems to be efficient, its implementation among French soldiers is very low.
Patients with persistent functional signs should be considered for complementary investigations in search of a perilymphatic fistula.
Blast injuries are common in the military setting (49%–63% depending on the series for war injuries).1 ,2 With the evolution of conflicts, including the emergence of improvised explosive devices (IEDs), the type of injuries encountered on operations has changed because of tactical combat casualty care and protective equipment for the trunk and skull, meaning that the relative incidence of head and neck injuries has increased. In the French Army, 13% of blast injuries in Afghanistan affected the ear.2 Primary blast injuries are related to the blast wave and particularly concern the tympanic membrane.3 Explosively propelled projectiles and fragments that strike patients cause secondary blast injuries; the blast wind generates tertiary injuries by the physical displacement of the body; and quaternary injuries encompass all other injuries such as burns, inhalation injuries and psychiatric problems.4 These risks justify an early and specialised management, and the North Atlantic Treaty Organization (NATO) now requires the presence of an ear, nose and throat surgeon for the management of these injuries at NATO Role 3.5 Soldiers wounded in the head and neck in combat are now supported by a specialist surgeon on the battlefield and subsequently are managed as patients in France.
The objective of this retrospective study was to describe the functional signs and the data from otoscopic and audiometric evaluation of blast injuries of the ear and to change the recommendations within the French Army in the light of the recent experience of military ENT surgeons engaged in war.
Materials and methods
This was a retrospective study of all patients who were referred with blast injuries of the ear to the Percy and Val de Grâce Military Training Hospitals (Clamart and Paris, France) from May 2002 to October 2014. Blast injuries of the ear are defined as trauma to the ear (external, middle and/or inner ear) resulting from exposure to an explosion. Massive explosions are defined as loads that are greater than 5 kg and also as the bombs used in terrorist attacks.6 The initial management of the injuries of patients in this study occurred on the site of the explosion and was then secondarily supported in France at the military hospitals.
Patients with underwater blast injuries, non-explosive blast injuries (slap, punch), isolated acoustic traumas, injuries resulting from minor explosions and patients who were killed in action were excluded from the study.7
The hospital ethics committee exempted this study from the need for consent because it only involved retrieving data from medical records (Scientific Committee for Clinical Trials of the Percy Hospital, February 2011).
The medical files were retrospectively examined, and the following data were analysed: age, gender, civilian or military status, the explosive device, whether hearing protection was worn or not, reported functional signs, ENT examination (including otoscopic examination), initial pure-tone audiometry and then at 1 and 3 months, initial emergency management, final treatment and eventual outcomes.
Statistical analysis was performed using SPSS/PC software V.10.0 (SPSS, USA). The Mann-Whitney U test was used to compare quantitative data, and Fisher's exact test was used to compare qualitative data. The differences were considered significant at p≤0.05.
From May 2002 to October 2014, 41 patients (82 ears) were included in the study (38 men; 27 soldiers) with a mean age of 34 years (range 20–57) at the time of injury. After the initial hospitalisation, 19 patients did not undergo any further follow-up and 10 did not undergo any follow-up beyond the assessment at 1 month after hospitalisation; 12 patients were followed for more than 3 months.
The French soldiers in our study had largely been wounded in action in Afghanistan (81%), and the majority of the civilian casualties resulted from the 2002 Karachi bus bombing in Pakistan (50%). Blast injuries of the ear were frequently related to terrorist attacks (95%), with the most common explosive device being IEDs (74%). Nine of our forty-one patients were the victims of suicide bombers.
The most frequently reported functional signs were tinnitus in 36 cases (88%), hearing loss in 25 (61%), earache (14; 34%) and vertigo (8; 20%); of the 22 patients who were followed for 1 month, 59% still reported tinnitus, and of the 12 patients who were followed for 3 months, 54% still reported tinnitus at 1 month and 62% still reported tinnitus at 3 months.
There were eight patients with vertigo initially, four of whom also had nystagmus and seven out of eight had a tympanic perforation; vertigo disappeared within 3 months in all but one patient, who initially presented with an irritative peripheral vestibular syndrome, from a stapes footplate fracture.
There were 36 perforated tympanic membranes (21 patients) among the 82 ears studied, which were bilateral in 14 patients, and 3 patients had multiple perforations (Figure 1). Three patients had a pharyngolaryngeal blast injury detected on the battlefield (petechiae of the soft palate, the anterior tonsillar pillar and the vocal cords) (Figure 2). These three patients each had an associated blast lung injury, but only two of them had tympanic perforations. Seven patients had widespread blast polytrauma, but three of them did not have tympanic perforations.
The initial postblast audiometric data showed that in 24 (29%) of the cases, there was pure sensorineural hearing loss, mixed hearing loss in 45 (55%), 12 cases (15%) of pure conductive hearing loss, and in one case, the patient had a complete loss of the ability to hear (cophosis) (Figure 3). There was no significant recovery of sensorineural hearing loss at 1 or 3 months. The audiometric results did not show significant differences between each patient's two ears, and when the tympanic membrane was perforated, there was no inner ear injury.
In this series, only 3/27 (11%) soldiers wounded in action wore hearing protection, none of whom had tympanic perforations, and their hearing loss was lower (but not significantly so) compared with the unprotected patients (Figure 4). The average age of the soldiers who were all wounded in action in Afghanistan by IEDs was 24 years. Just under half (46%) of the study patients underwent steroid therapy with an average dose of 1 mg/kg (prednisolone or methylprednisolone), with half of them receiving the steroids at the prehospital stage. In addition, 16 patients were given antibiotic prophylaxis and five patients received antibiotic eardrops (ofloxacin) for a purulent otorrhea.
Nine tympanoplasty procedures were performed in eight patients—none with ossicular lesions. The mean time between the explosion and surgery was 14.2 months (range 5–35 months). All patients initially underwent a type 1 tympanoplasty using an endaural approach, using a temporalis fascia graft in 6 and a tragal cartilage graft in 3 cases, with successful sealing of the perforation in 4/9 ears (44%). One patient had to undergo further surgery for an acquired cholesteatoma. Four ears (with initial subtotal perforations) out of the five residual perforations involved <10% of the tympanic membrane surface and underwent a second surgery that succeeded in sealing the perforation with an adipogenic graft (three cases) and a tragal cartilage graft (one case).
The population analysed in this study was predominantly male, which was expected given the characteristics of the study population, as the only 2.3% of the French Army are female;8 in addition, all the civilian casualties that resulted from the 2002 Karachi bus bombing in Pakistan were male.
Tinnitus, earache and vertigo are common following blast injury with a varying prevalence (Table 1).
In our series, as in the literature, tinnitus was an intense, acute tone that was enduring after the initial injury, and even increasing over the time,9 ,13 which explains why there are more patients complaining of tinnitus at 3 months than at 1 month in our series. More than half of the patients requiring hospitalisation for blast injuries also have post-traumatic stress disorder (PTSD),14 and there is a higher prevalence of tinnitus in patients with PTSD regardless of the source of the trauma,15 including in those without blast injuries of the ear. It is difficult to discern the aetiology of the tinnitus, as it is often multifactorial in these patients and can be based both on otological and psychological origins.
Regarding vertigo, patients most often report dizziness without an actual rotary component, and clinical examination does not systematically find any physical signs such as nystagmus.12 However, dizziness is the sign of an actual otoneurological dysfunction. Scherer et al 16 prospectively compared two groups of 12 American soldiers (asymptomatic and symptomatic) for dizziness. The patients with dizziness had greater unilateral vestibular weakness as examined via videonystagmography; however, in both groups, there was unexplained nystagmus that was caused by central vestibular dysfunction.17 Cases of vertigo such as these are often associated with head trauma linked to a secondary or tertiary blast injury and is therefore difficult to distinguish between an injury of the ear and a central injury. Unlike our series, the literature reports a tendency of this feeling of dizziness to be prolonged.17 ,18
The single patient that had cophosis presented with persistent vertigo, which evoked the diagnosis of perilymphatic fistula, which is an abnormal connection in one or both of the windows that separate the air-filled middle ear and the fluid-filled perilymphatic space of the inner ear; this small opening allows perilymph to leak into the middle ear. The functional symptoms of this disorder are variable, but positional vertigo and sensorineural hearing loss or even cophosis, as our patient had, suggest the diagnosis. Pneumolabyrinth, which is pathognomonic for perilymphatic fistula, is not always found on the CT scan. This diagnosis is difficult to determine, and complementary investigations must be repeated to obtain more sensitivity.19 ,20 Our patient had a stapes footplate fracture of the oval window, and his initial CT scan showed no pneumolabyrinth. It is not always clear which patients should undergo surgical exploration and when this should take place. There are few cases of perilymphatic fistula that are caused by blasts in the literature.21 Prisman et al 22 recommend a systematic exploration of patients with a persistent otoliquorrhea, a progressively worsening hearing loss or a persistent vertigo.
In our series, the three patients with pharyngolaryngeal blast injuries also had blast lung injuries, but only two of them had tympanic perforations (Figure 2). Similarly, seven of the patients had polytrauma, but only four of them had tympanic perforations. Presentations of blast injuries of the middle ear (tympanic membrane and ear ossicles) are highly variable from one series to another and depend on multiple factors. There is a correlation between the size of the perforations and the force of the explosions.5 ,22–25 The middle ear is typically the first organ affected by a blast, because it is the body's most sensitive pressure transducer,24 and it has long been viewed as an indicator of primary blast injuries and as a way to triage the blast injured in mass casualty situations.26 ,27 In this series though, otoscopic examination does not seem to be a reliable way to identify patients with blast lung injuries;28 ,29 in contrast, the presence of a laryngeal blast injury is an excellent predictor of a lung blast injury.30 ,31 However, in this series, there were only 3 cases of pharyngolaryngeal blast injuries versus 13 cases of lung blast injuries (Figure 2). The pharyngolaryngeal lesions usually disappear within 48 hours and are not significant once the patient is intubated because of injuries inherent in orotracheal intubation in an emergency setting.32 Thus, the diagnosis of a laryngeal blast injury must be established during the prehospital stage, and a laryngeal nasofibroscopy should be performed for any patient with a suspicion of blast injury,33 ,34 but this procedure is difficult for non-specialists to perform.
Over three-quarters of our patients had definitive sensorineural hearing loss, a finding comparable with that in the literature.13 However, in our series, the steroid therapy was only given in one out of two patients, and at the prehospital stage, only in one out of four, which made it difficult to assess the effectiveness of this treatment.
When the tympanic membrane was perforated, there was no additional inner ear injury, and there is no correlation between inner ear injury and the presence of a tympanic perforation.35 Early steroid therapy is recommended for all blast patients who do not have medical contraindications, but in practice, this is not the case.36 Military physicians are aware of the guidelines, but they also know that more than a quarter of penetrating war injuries become infected.37 ,38 The relationship between steroid treatment use and trauma-related infections in battlefield casualties is not clear. The few studies that have evaluated the risk of infection due to steroid use have all assessed small cohorts and have shown mixed results.39 ,40 In our series, otoscopic examinations greatly influenced the early initiation of steroid treatment. On one hand, a non-perforated tympanic membrane could be interpreted by the physician on the battlefield to indicate that the ear was not affected by the blast and that the patient would not benefit from treatment; conversely, a patient with a tympanic perforation, especially if associated with penetrating lesions, would not benefit from steroid treatment because of the increased risk of infection.
Only 3/27 soldiers who were wounded in action were wearing hearing protection; two were wearing foam earplugs as supplied by the French Army, and one patient was wearing non-linear earplugs. None of these three patients had tympanic perforations, and their hearing loss tended to be lower than that in patients who did not wear ear protection, although they were younger than the average age of the blast-injured patients. It is widely accepted that systematic hearing protection prevents acoustic trauma, and this idea is becoming more and more respected in the French Army,41–44 as they are also effective against damage to the middle and inner ear in cases involving blasts.45–47 As this protection is so effective, it is difficult to understand why hearing protection is not more commonly worn; one reason is that soldiers complain that having their ears occluded is detrimental to operations.44 ,48 Whether it is in terms of achieving the mission or with regard to ergonomic characteristics, the best method to date to protect hearing seems to be electronic active-volume hearing protections.49 Detection of the surrounding noise is effective with this type of hearing protection, but there is still a problem with noise localisation.49
One-third of patients underwent antibiotic prophylaxis, but only 12% underwent antibiotic eardrops for purulent otorrhea. There is consensus on the need for early antibiotic prophylaxis to prevent bacterial growth in the highly contaminated tissues that result from cases of trauma-related infections in battlefield casualties.50 However, there are little data in the literature regarding the role of topical antibiotic therapy. In rats, the combination of ciprofloxacin and dexamethasone improved tympanic membrane perforation healing.51
Concerning the management of tympanic membrane perforations, only 9/36 tympanic membranes did not heal spontaneously. This high rate of spontaneous healing was comparable with that in the literature, except for large perforations. Spontaneous healing is primarily dependent on the size of the perforation: no spontaneous closures have been found for perforations that encompass more than 80% of the tympanic surface.7 ,10 ,11 Therefore, tympanoplasty should be performed without delay on all total and subtotal tympanic membrane perforations, and small ruptures should be left to heal spontaneously, and only those small perforations that do not heal spontaneously within 3 months should undergo tympanoplasty.33 Blast wave positive pressure causes the entrance of epidermal debris and foreign objects into the middle ear and almost systematically reverses the edges of the perforation, which creates a major risk of post-traumatic cholesteatoma. Eversion of the edges should be achieved as early as possible and is associated with the establishment of a ‘patch’ that serves both as guardian and protector of the tympanic scarring of the middle ear.52 Lesions of the middle ear must therefore be followed closely by the ENT service.
Nine tympanoplasty procedures were performed more than 5 months after the blast injuries in perforations that included more than three-quarters of the tympanic surface. In only 4/9 ears were the perforations successfully sealed, but the residual perforations were small, and were subsequently successfully sealed with adipogenic grafts. Similarly, Poncet et al 6 reported a success rate of 25% for large perforations only. Conversely, Sudderth35 had a better success rate (86.9%), but their series included perforations of all sizes. Surgery was used in six cases of temporalis fascia graft and in three cases of tragal cartilage graft, with one and three successes, respectively (p>0.05). There is no significant difference in the technical success to achieve tympanic membrane perforation closure using either cartilage or fascia graft.34
Blast injuries of the ear are characterised by significant functional signs and are not correlated to otoscopic examinations, and the sensorineural hearing loss caused rarely returns.
Any patient exposed to a massive explosion has to be considered as injured by blast until proven otherwise, especially in consideration of the risk of blast lung injury. When deciding on initial management, including case of triage for mass casualties, the status of the tympanic membrane does not provide any information about the risk of primary blast injury of the lung; laryngeal nasofibroscopy seems more relevant.
Early steroid therapy is recommended for all patients’ blast injury of the ear without medical contraindication. Patients with persistent functional signs should be eligible for complementary investigations in search of a perilymphatic fistula.
Hearing protection is efficient in preventing these ear injuries, but its implementation among soldiers is very low, and efforts should be made to improve the usage of these aids. In the French Army, the deployment of ENT surgeons onto the battlefield has enabled management and detection of laryngeal blast injury in a way that is more similar to that performed in the civilian setting in France.
Contributors SBdR planned the study, drafted the article, submitted the study, and gave final approval of the version to be published and agreement to be accountable for all aspects of the work. AC planned the study and conducted the survey, did the acquisition of data, the analysis and interpretation of data, and gave final approval of the version to be published and agreement to be accountable for all aspects of the work. OM did the analysis and interpretation of data, drafted the article, and gave final approval of the version to be published and agreement to be accountable for all aspects of the work. QL and SM realised the literature review, did the acquisition of data, and gave final approval of the version to be published and agreement to be accountable for all aspects of the work. YP did the critical revision of the article for important intellectual content, and gave final approval of the version to be published and agreement to be accountable for all aspects of the work.
Disclaimer This article is based on the medical thesis of Dr Anna Crambert, which has been published commercially as ‘Blast auriculaires aerians par explosion’. The data have not previously been published as an academic paper.
Competing interests None declared.
Ethics approval Scientific Committee for Clinical Trials of the Percy Hospital, February 2011.
Provenance and peer review Not commissioned; externally peer reviewed.
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