Sudden bilateral deep hearing loss rarely occurs in children. It is estimated that it occurs in about 2% of cases of hearing impairment (1). The etiology of the sudden bilateral hearing loss is still not fully understood. The probable factors include vascular disorders of the inner ear, infections – mostly viral, trauma of the temporal bone, and, occurring more and more often, acoustic trauma (2). Noise is one of the most oppressive harmful environmental factors, and with the civilizational progress, noise exposure has been increasing. Excessive exposure may lead to health hazards (3).

Hearing impairment may be caused by a single exposure to noise or by a long-term exposure (4). Acute acoustic trauma is caused by a noise of a very high sound pressure level that usually exceeds the threshold of pain (120-140 dB). The effect of such stimulus is a sudden (temporary or permanent) sensorineural hearing impairment, often unilateral, sometimes accompanied by tinnitus. If the structures of outer and middle ear are simultaneously affected, the hearing impairment may have a mixed character (4).

The following types of noise causing acoustic trauma can be enumerated: pure tone sound, street and industrial noise, shooting noise, and explosion (5).

The degree of hearing loss depends on the intensity of the noise, the duration of exposure on a given day, as well as lifetime exposure, the frequency of the sound, the type of the noise (intermittent, continuous, pulse), age and sex of the patient, as well as individual ear sensitivity, which is difficult to define and is probably affected by some innate features of the middle and inner ear, determining, among others, the efficacy of sound conduction, as well as the blood supply and oxygenation of the cochlea (5, 6).

The most common type of the hearing loss is the sudden unilateral sensineural hearing loss in the high frequencies with accompanying tinnitus.

Children and adolescents are considered to be particularly vulnerable to noise-induced hearing loss (4).

The risk of sudden hearing loss in children is increased by, among others, available toys (whistles, trumpets, music toys, toy guns – ca. 100-135 dB) and fireworks explosions (ca. 145-160 dB) (7). However, the biggest threat is posed by discos (92-111 dB), rock music concerts (ca. 90 dB), listening to music (ca. 86 dB), motorsports (ca. 80 dB), and shooting sports (ca. 170 dB) (8, 9).

A nine-year-old girl was admitted on an emergency basis to the Department of Pediatric Laryngology of the Medical University of Warsaw because of bilateral mixed hearing loss. Approximately 6 weeks before the admission, the patient experienced an acoustic trauma in her school due to school bell ringing during school break. Since that time, she had experienced hearing impairment in her left ear, however, she had not told her parents about it. Therefore, she had not been examined by a pediatrician or a laryngologist, nor had she been referred to a hospital or received any treatment. It was only the occurrence of bilateral hearing impairment that prompted the girl’s parents to consult a laryngologist and to report to the hospital. The day before the admission, a minor viral infection of the upper respiratory tract occurred, accompanied by sudden hearing loss in the right ear. On admission in the emergency room, no findings in the general physical examination were observed – lymph nodes were not enlarged, normal vesicular sound was heard over the lungs, no arrhythmias were detected, abdominal organs were not enlarged, meningeal signs were negative. On admission to the Department of Pediatric Laryngology, the general condition of the patient was good. She did not report tinnitus or vertigo. Medical history collected from the mother included hearing loss since the day before – the girl had not been responding to commands and had been asking to repeat phrases. In the otoscopy, tympanic membranes were gray, pale, without signs of perforation, slightly drawn in the direction of the tympanic cavity, with a trace of exudate in the left tympanic cavity, without signs of acute inflammation in any of the ears. In the endoscopic examination, a minor adenoid hypertrophy was identified nasopharyngeal lumen was wide, pharyngeal openings of the auditory tubes were slightly swollen. In the hearing test: Weber was lateralized to the left ear, and in the Rinne test, the duration of air conduction was shorter than the bone conduction (Rinne negative). On tonal audiometry performed on an outpatient basis on admission, a bilateral mixed deep hearing impairment was detected (fig. 1). In the laboratory tests, no raised inflammatory markers were observed tab. 1. Due to the medical history and abnormal hearing examination, the girl was qualified for surgery on an emergency basis. In general anesthesia, explorative tympanotomy was performed and a normal ossicular chain was found, without damage to the joints and ossicles, no perilymph fistula of the inner ear was found. On the right side, the tympanic membrane was pulled into the epitympanum and overlayed the ossicular chain. On the left side. a trace amount of exudate was observed in the tympanic cavity, and the pathological secretion was removed. On both sides, 2 mg of Dexaven were administered into the tympanic cavity. Subsequently, bilateral tympanocentesis with tube insertion was performed. Conservative treatment included dexamethasone, vipocentin, piracetam, B vitamins, and xylometazoline. Due to the bilateral deep hearing loss and no signs of otitis media, it was decided to implement hyperbaric oxygen therapy. The hospitalization lasted 14 days. During the hospital stay, the patient felt well, no adverse effects of medication nor of the hyperbaric oxygen therapy were observed. The control tonal audiometry was performed after one day of treatment (fig. 2), and after 10 days of treatment (fig. 3), with satisfactory results.

After 15 sessions of hyperbaric oxygen therapy with good tolerability, with simultaneous pharmacological treatment, a complete recovery of hearing was achieved, and the treatment was completed with very good results. Auditory examination was repeated on the outpatient basis 2 weeks after the completion of the treatment (fig. 4).

Noise exposure is particularly high in industrialized and developing regions of the world (3, 10). The damaging effect of noise on inner ear is a result of micromechanical injury, metabolic disorders associated with oxidative stress, an excessive production of reactive oxygen species, an excessive production of glutamic acid in synaptic connections between the cells of the inner ear and afferent nerve fibers, circulatory disturbances in the stria vascularis of cochlear duct, and ionic disorders in body fluids (11-14). Although most publications on hearing impairment concern adults, the threat is not limited to people working in the industry. Recently, many clinical and epidemiological studies have indicated that children and adolescents are also in danger of an increasing exposure to noise (14, 15). The groups with particularly high risk include children treated in intensive care units, prematurely born and low-weight infants, children treated with ototoxic medications, persons that spend long time in a noisy environment, persons suffering from hearing impairment, tinnitus, hearing hypersensitivity, and persons who have positive family history of hearing impairment (10, 16). Noise may sometimes cause very serious hearing damage, often permanent, and hearing impairment has become an important social problem. It must be taken into account that extra auditory effects of noise may also occur, but are underdiagnosed due to their non-specificity. According to many authors, these effects include anxiety, irritability, fatigue, cognitive impairment and reduced intellectual ability, sleep disturbances (change of sleep phases, excessively light sleep, frequent awakenings), circulatory disorders (increased heart rate, heart palpitations, dyspnea, fatigue), disorders of the immune system, hormonal disorders, and changes in social behavior (17-20). In the case presented in this article, the girl had experienced acute acoustic trauma of the left ear caused by school bell ringing 6 weeks before the admission to the hospital. During this time, she had not reported a problem, and thus, had not been reported to a pediatrician or a laryngologist by her parents nor teachers and had not been treated. The day before the admission, an infection of the upper respiratory tract of the probably viral origin had occurred, leading to hearing loss on the right side. Only the occurrence of bilateral hearing loss had been noticed by the parents and the patient was admitted to the hospital. On tonal audiometry on the day of admission, bilateral mixed deep hearing impairment was diagnosed. The girl was qualified for bilateral explorative tympanostomy in order to examine the structures of the middle ear to diagnose the cause of the hearing loss. Due to the suspicion of impaired patency of the right auricular tube and slight exudate in the left tympanic cavity, tubes were inserted to ensure proper ventilation of the middle ear. The observed bilateral deep hearing loss was probably caused by the acute acoustic trauma caused by a school bell and perhaps also by the viral infection. The role of viral infections in children is frequently discussed in cases of sudden hearing loss, however, it is difficult to determine, as virology examinations are not frequently performed. It is believed that the most objective test would be the examination of the inner ear fluid, and that blood tests and cerebrospinal liquor may not be conclusive despite an infection (21).

Due to the noise exposition in the medical history and deep bilateral hearing loss, hyperbaric oxygen therapy (HBO) was also included in the treatment plan. Indications for HBO are based on the results of experimental studies and clinical trials on physiological, physical and biochemical effects of exposure to hyperbaric oxygen therapy (22). Hyperbaric oxygen therapy is defined by UHMS (Undersea and Hyperbaric Medical Society) as an intervention in which an individual breathes 100% oxygen intermittently while inside a hyperbaric chamber that is pressurized to greater than sea level pressure (1 atmosphere absolute, or ATA) (23). The therapeutical effects of hyperbaric oxygen therapy remain a subject of scientific debate and research. In literature, there are numerous reports of side effects of hyperbaric oxygen therapy, including impaired patency of pharyngotympanic tube, feeling of fullness in the middle ear, and exudative otitis media, which may require tube insertion in some cases (24). In addition, cases of myopia, seizures, tympanic membrane perforation, tinnitus, vertigo, and, in case of pregnant women, also fetal complications, are described in the literature (25). In the case presented in this article, no auricular complications have been observed, thanks to the bilateral tube insertion before the beginning of the hyperbaric oxygen therapy. It must be also taken into account that one-sided hearing impairment in children is often unnoticed by them and they may not report any problem for a long time. In the case presented in this paper, the patient had not visited a pediatrician or a laryngologist for 6 weeks after the trauma had occurred. Only the occurence of hearing impairment in the right ear and consequent bilateral hearing impairment prompted the parents of the child to seek help urgently. Often it is the long-term complications, such as school problems, attention deficits, concentration problems, requirement for frequent repetition, and repetition of words and phrases, that suggest the problem to the parents or teachers (26, 27). It must also be considered that the contact with a child may be limited, as the child may marginalize the problem or not be able to name the symptoms. Therefore, in the era of constantly increasing noise intensity, early education of both children and parents is of primary importance. Hearing impairment caused by noise results in many complications, not only associated with physical health, but also social, emotional, intellectual, and linguistic problems. The world has become a noisy place and a threat to all of us, including our children. Excessive noise level in schools related to the student’s activities during school breaks and during physical education lessons in the sports halls, as well as outside noises, not only cause hearing impairment, but may also negatively affect learning process, concentration, attention, speech perception and general health condition (28). According to the results of some studies, about 10-20% of all the teenagers and young adults under 18 years of age are at risk of hearing loss and tinnitus as a result of voluntary listening to loud music using personal CD and MP3 players, participating in mass events, such as music festivals, concerts, and discos (29-31). Hearing impairment has become a problem so serious that WHO (World Health Organization) has issued a report on the occurrence of the disorder in the world. According to this report, there are 360 million people with hearing impairment around the world, of which 32 million (9%) are children (32). Moreover, WHO notes that as many as 1.1 billion young people worldwide may be at risk of hearing loss (32).

It is therefore essential to continuously take effective, comprehensive actions, implement age-targeted educational programs for students of primary and secondary schools, as well as their parents and teachers, in order to familiarize them with potentially harmful noise sources in the environment.

1. Sudden bilateral hearing loss rarely occurs in children.

2. The noise of considerable intensity occurring in nurseries, kindergartens, and schools can cause hearing impairment.

3. The occurrence of sudden hearing loss may be preceded by the symptoms of an acute viral infection.

4. The consequences of hearing loss in children are difficult to predict. It is important to recognize the problem early, to introduce a proper diagnostic process and implement the treatment quickly, which is a key to the positive outcome.

5. Oxygen therapy and hyperbaric oxygen therapy have their indications and contraindications, and their use is associated with the possibility of complications.

6. Prophylaxis, aiming at reducing the impact of harmful environmental risk factors for acoustic trauma, is important.