El buceo recreativo y la otorrinolaringología: ¿qué sabemos y deberíamos saber? / Recreational diving and otolaryngology: what do we know and should we know?

El buceo recreativo es una práctica cada vez más popular en la población mundial, sin embargo, no está exenta de riesgos. A medida que transcurre una inmersión, el buzo es susceptible a una serie de cambios de presión que afectan las distintas cavidades que contienen aire dentro del cuerpo humano, tales como el oído, cavidades paranasales y los pulmones. Existe un gran espectro de patologías asociadas al buceo, explicándose la mayoría de ellas por el barotrauma asociado, cuya gravedad depende de la magnitud del daño asociado, pudiendo presentar desde manifestaciones a nivel local, así como también a nivel sistémico. Las patologías otológicas suelen ser las más frecuentes y el principal motivo de consulta en este tipo de pacientes. Sin embargo, las afecciones otoneurológicas, rinosinusales, de vía aérea y sistémicas pueden ser comunes dependiendo de cada perfil de buceo. Actualmente no existen recomendaciones locales sobre esta práctica, por lo que el conocimiento de la fisiología, fisiopatología y el tratamiento de las patologías otorrinolaringológicas asociadas deben ser conocidas a medida que este deporte se vuelve cada vez más popular. Se realizó una revisión de la literatura sobre las distintas afecciones otorrinolaringológicas con el fin de sistematizarlas y elaborar recomendaciones para establecer una práctica segura.

Recreational diving is an increasingly popular practice in the world; however, it is not without risks. As a dive progresses, the diver is susceptible to a series of pressure changes that affect the air-containing cavities, such as the ear, paranasal cavities, and lungs. There is a large spectrum of pathologies associated with diving, most of them being explained by associated barotrauma, the severity of which depends on the magnitude of the associated damage, could present local manifestations, as well as at systemic level. Otological pathologies are usually the most frequent and the main reason for consultation in this type of patients, however, otoneurological, rhinosinusal, airway and systemic conditions can be common depending on each diving profile. Currently there are no local recommendations on this practice, therefore, knowledge of the physiology, pathophysiology and treatment of associated otorhinolaryngological pathologies should be known as this sport becomes increasingly popular. A review of the literature on the different ear, nose and throat conditions was carried out in order to systematize them and develop recommendations to establish a safe practice.

The effect of total compression time and rate (slope) of compression on the incidence of symptomatic Eustachian tube dysfunction and middle ear barotrauma: a Phase II prospective study.

Eustachian tube dysfunction (ETD) and middle ear barotrauma (MEB) are common reported complications during hyperbaric oxygen treatment. Our Phase I study data was the first to demonstrate a statistically significant decrease in the occurrence of symptomatic ETD and MEB. The Phase I Trial suggested the total time interval and rate (slope) of compression (ROC) may be a determining factor in ETD and MEB. This Phase II study investigates an optimal rate of compression to reduce ETD and MEB when considering each multiplace treatment (with multiple patients) as the unit of observation as a group, rather than for each individual patient. Data were collected prospectively on 1,244 group patient-treatment exposures, collectively including 5,072 individual patient-treatment/exposures. We randomly assigned patient-treatment group exposures to four different time interval and rate (slope) of compression. These compression rates and slopes were identical to those used in the Phase I trial. All patients experiencing symptoms of MEB requiring compression stops were evaluated post treatment for the presence of ETD and MEB using the O'Neill Grading System (OGS) for ETD. Data were analyzed using the IBM-SPSS statistical software program. A statistically significant decrease in the number of compression holds was observed in the 15-minute compression schedule, correlating to the results observed in the Phase I trial. The 15-minute linear compression profile continues to demonstrate the decreased need for patient symptomatic compression stops (as in the Phase I trial) using a USN TT9 during elective hyperbaric oxygen treatments in a Class A multiplace hyperbaric chamber. Trial Registration: ClinicalTrials.gov Identifier: NCT04776967.

Prevention of middle ear barotrauma with oxymetazoline/fluticasone treatment.

Middle ear barotrauma (MEB) is a common complication of hyperbaric oxygen (HBO2) therapy. It has been reported in more than 40% of HBO2 treatments and can interrupt the sequence of HBO2. MEB may lead to pain, tympanic membrane rupture, and even hearing loss. The aim of this study was to determine if pretreatment with intranasal fluticasone and oxymetazoline affected the incidence of MEB. We conducted a retrospective chart review of subjects undergoing HBO2 at our institution between February 1, 2014, and May 31, 2019. Subjects in the fluticasone/oxymetazoline (FOT) treatment group used intranasal fluticasone 50 mcg two times per day and oxymetazoline 0.05% one spray two times per day beginning 48 hours prior to initial HBO2. Oxymetazoline was discontinued after four days. Fluticasone was continued for the duration of HBO2 therapy. A total of 154 unique subjects underwent 5,683 HBO2 treatments: 39 unique subjects in the FOT group underwent 1,501 HBO2; 115 unique subjects in the nFOT (no oxymetazoline or fluticasone treatment) group underwent 4,182 HBO2 treatments. The incidence of MEB was 15.4% in the FOT group and 16.2% in the nFOT group. This was not a statistically significant difference (OR = 0.77; p = 0.636). Treatment pressure, age over 65 years, male sex, and BMI were not associated with a difference in MEB incidence. In summary, pretreatment with intranasal oxymetazoline and fluticasone in patients undergoing HBO2 did not significantly reduce MEB. More investigation with larger numbers of participants and prospective studies could further clarify this issue.

Effect of self-acupressure on middle ear barotrauma associated with hyperbaric oxygen therapy: A nonrandomized clinical trial.

BACKGROUND: In hyperbaric oxygen therapy (HBOT), a patient is exposed to pure oxygen in a chamber. While HBOT is a long-standing and well-established treatment for a wide variety of medical conditions, one of the main complications is middle ear barotrauma (MEB), which can lead to complaints of ear discomfort, stuffiness or fullness in the ear, and difficulties in equalizing ear pressure. The aim of this study is to evaluate the efficacy of self-acupressure in preventing and reducing the degree of MEB associated with HBOT. METHODS: This is a prospective nonrandomized controlled study. A sample of 152 participants will be assigned to 2 groups in a 1:1 ratio. The participants in the control group will receive conventional Valsalva and Toynbee maneuvers, while those in the experimental group will be given additional self-acupressure therapy. The acupoints used will be TE17 (Yifeng), TE21 (Ermen), SI19 (Tinggong), and GB2 (Tinghui). The Modified Teed Classification, symptoms of MEB, and overall ear discomfort levels will be assessed. Data will be analyzed using the Chi-Squared test or t test. OBJECTIVES: This study aims to evaluate the efficacy of self-acupressure for preventing and reducing the degree of MEB associated with HBOT. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04311437. Registered on 17 March, 2020.

An unusual case of ear mould impression material as a foreign body in the middle ear: case report.

BACKGROUND: The occurrence of retained ear mould impression material is rare and can lead to complications. The current case report describes one such complication, where the silicone impression material used to take the impression of the ear canal flowed into the middle ear through the pre-existing tympanic membrane perforation. Five days later, the patient presented with worsened hearing and blood-tinged discharge from the ear. Ear microscopy revealed a greenish foreign body in the middle ear. CASE REPORT: The foreign body was removed by tympanotomy and the perforation repaired using a temporalis fascia graft. A hearing aid was prescribed after ensuring that the perforation had healed. CONCLUSION: It is essential that the audiologist perform a basic otological examination before prescribing a hearing aid and preparing an ear mould. A clinical approach algorithm for audiologists, for prior to taking an impression, is suggested.

Eustachian tube function test as a predictor of middle ear barotrauma.

BACKGROUND: Most of the cases of middle ear barotrauma in divers are due to the impassability of the Eustachian tube. The aim of our study is to compare the results of tympanometry and Valsalva part of Eustachian Tube Function test (ЕТF-test) with the ability of divers to compensate for the change in ambient pressure in a hyperbaric chamber. MATERIAL AND METHODS: The study included 35 professional divers undergoing annual medical examination. For all subjects is measured first intratympanal pressure at rest, then after the maneuver of Valsalva with impedancemeter. Then a barofunction test (BFT) was performed to assess the diving fitness and the passability of the Eustachian tubes. It consists of divers compressing and decompressing in a hyperbaric chamber to a pressure of 2.2 ATA for 1 minute. Based on results from previous studies we are using a 20 DaPa cutoff point on the ETF test to predict Eustachian tube passability and a successful barofunction test. RESULTS: In the current study 24 divers have ETF test results higher than 20 DaPa. 3 divers have ETF test values lower than 20 DaPa in both ears, but none of them displayed difficulties in the BFT. 8 divers have ETF values lower than 20 DaPa in one ear and higher than 20 DaPa in the other. 7 of the last group displayed difficulties with the BFT in the ear with poor ETF result. CONCLUSIONS: We consider that the ETF test can be used to assess diving fitness as a screening method before performing a BFT, as values above 20 DaPa guarantee Eustachian tube function sufficient for diving activities. Values of 20 DaPa and less are not a definite predictor of the BFT results. The results of the ETF test can also be used in the usual work of an otorhinolaryngologist to evaluate Eustachian function in cases of unilateral disease of middle ear.

Middle-ear barotrauma after hyperbaric oxygen therapy: a five-year retrospective analysis on 2,610 patients.

Introduction: Hyperbaric oxygen (HBO2) therapy is the use of oxygen or gas mixtures at a pressure above atmospheric pressure for therapeutic purposes. This treatment is used in numerous pathological processes. Its main side effect is middle ear barotrauma (MEB), which represents a great concern for iatrogenic HBO2 therapy. The aim of this work is to describe this adverse event in order to highlight clinical elements that can contribute to its prevention and management. Methods: We conducted a five-year retrospective study from January 2013 to December 2017, where 2,610 patients were selected, in the Hyperbaric Medicine Centre, Sainte- Marguerite Hospital of Marseille, France. Results: 262 patients experienced MEB after HBO2, representing a prevalence of 10.04% and incidence of 0.587%. Their average age was 55 ± 19 years. Women were more affected than men. We have not highlighted a seasonality to this condition. Risk factors were: age older than 55 years, female gender, ear, nose and throat history (cancer, radiotherapy, infections or allergies, malformations or benign tumors), general history (smoking, obstructive breathing disorders, thyroid disorders and obesity), HBO2-approved indications of sudden deafness and delayed wound healing, and altered tympanic mobility on initial examination. Although the benign stages of Haines-Harris classification were the most encountered in our study, MEB was responsible for premature discontinuation of HBO2. Conclusion: MEB is a common condition responsible for many premature discontinuations of HBO2. Its origin is multifactorial, associating non-modifiable and modifiable factors. Better management of this affection will further contribute to making HBO2 a low-risk treatment.

Evaluation of a Model of Long-Term Middle Ear Catheterization for Repeat Infusion Administration and Cochlear Hair Cell Injury in Guinea Pigs.

Middle ear administration has numerous applications, including antibiotherapy and gene therapy, and is increasingly used to target the auditory and vestibular systems. In animal studies, investigating repeated exposure that mimics clinical dosing regimens has remained a challenge due to the lack of suitable models. Intratympanic injections are not suitable for long-term studies due to the increased risk related to tympanic membrane rupture or scarring and repeat anesthesia events. Surgical models of middle ear catheterization previously used have not been reliable for longer than 4 weeks, resulted in elevated stress levels, and have been associated with significant changes related to the surgery and/or the presence of the catheter such as local trauma and inflammatory and degenerative processes. These complications cause decreased hearing/deafness and greatly diminish the value and accuracy of ototoxicity studies. We describe here a procedure that permits repeat dosing into the middle ear of guinea pigs and can be used to produce a model of aminoglycoside-induced hair cell injury. The innocuity of the procedures and the efficacy of the ototoxicity model were confirmed using auditory brain stem response assessment, histopathological evaluation, and cytocochleograms. Procedure-related changes were limited to minimal inflammation in the middle ear.

Electrical Injury Causing Facial Nerve Palsy in a Toddler.

Although electrical injuries are one of the common injuries encountered in clinical practice, low voltage electrical injuries presenting as focal neurological deficits are rare. We report the case of a 3-year-old boy who presented with right facial palsy and hemotympanum after electrical injury.

Recurrent Middle Ear Barotrauma in Student Pilots.

INTRODUCTION: The present study evaluated the efficacy of the nine-step inflation-deflation tympanometric test for predicting recurrence of middle ear barotrauma.METHODS: Student pilots who were diagnosed with middle ear barotrauma from October 2010 to April 2011 were enrolled. The grade of barotrauma was assigned using Teed's classification. All subjects underwent tympanometry and nine-step inflation-deflation testing at first visit and after improvement. Recurrence was monitored for 2 wk after they resumed flight. The relationships among the recurrence of middle ear barotrauma, the grade and duration of disease, and tympanometric and nine-step test results were evaluated.RESULTS: There were 35 cases enrolled. According to Teed's classification, 16 cases were Grade 0 (45.7%) and 11 cases were Grade I (31.4%). Grade III was shown in seven cases (20.0%) and one subject was Grade IV (2.9%). The mean duration of illness was 5.9 d. In the initial 9-step tests, 29 subjects (85.3%) failed to pass the entire test. On follow-up tests, eight cases (22.9%) failed. Seven pilots (20.0%) showed recurrent middle ear barotrauma after resumed flight. All of the cases with recurrence failed the follow-up nine-step tests. The nine-step test showed high sensitivity and specificity values for predicting recurrence. A clear correlation was observed between recurrence and nine-step test results.DISCUSSION: The nine-step inflation-deflation test provides useful information about Eustachian tube function. The nine-step test can be useful to reduce the risk of recurrence of middle ear barotrauma in pilots.Sohn JH. Recurrent middle ear barotrauma in student pilots. Aerosp Med Hum Perform. 2019; 90(8):681-687.

Bone conduction hearing in the Guinea pig and the effect of artificially induced middle ear lesions.

Although human bone conduction (BC) hearing is well investigated, there is a lack of information about BC hearing in most other species. In humans, the amount of conductive loss is estimated as the difference between the air conduction (AC) and BC thresholds. Similar estimations for animals are difficult since in most species, the normal BC hearing thresholds have not been established. In the current study, the normal BC thresholds in the frequency range between 2 kHz and 20 kHz are investigated for the Guinea pig. Also, the effect of a middle ear lesion, here modelled by severing the ossicles (ossicular discontinuity) and gluing the ossicles to the bone (otosclerosis), is investigated for both AC and BC. The hearing thresholds in the Guinea pigs were estimated by a regression of the amplitude of the compound action potential (CAP) with stimulation level and was found robust and gave a high resolution of the threshold level. The reference for the BC thresholds was the cochlear promontory bone velocity. This reference enables comparison of BC hearing in animals, both intra and inter species, which is independent on the vibrator and stimulation position. The vibration was measured in three orthogonal directions where the dominating vibration directions was in line with the stimulation direction, here the ventral direction. The BC thresholds lay between -10 and 3 dB re 1 µm/s. The slopes of CAP growth function were similar for AC and BC at low and high frequencies, but slightly lower for BC than AC at frequencies between 8 and 16 kHz. This was attributed to differences in the stimulus levels used for the slope estimation and not a real difference in CAP slopes between the stimulation modalities. Two kinds of middle ear lesions, ossicular discontinuity and stapes glued to the surrounding bone, gave threshold shifts of between 23 and 53 dB for AC while it was below 16 dB when the stimulation was by BC. Statistically different threshold shifts between the two types of lesions were found where the AC threshold shifts for a glued stapes at 2 and 4 kHz were 9-18 dB greater than for a severed ossicular chain, and the BC threshold shifts for a glued stapes at 4 and 12 kHz were 8-9 dB greater than for a severed ossicular chain.

The effect of compression rate and slope on the incidence of symptomatic Eustachian tube dysfunction leading to middle ear barotrauma: a Phase I prospective study.

Introduction: Symptomatic Eustachian tube dysfunction (ETD) and middle ear barotrauma (MEB) are the most common reported complications during hyperbaric oxygen (HBO2) treatment. There is no standardized rate of compression (ROC) reported to decrease the incidence rates of ETD and MEB during hyperbaric treatments. Few studies actually demonstrate that the ROC decreases the incidence of ETD or MEB. Methods: Our study was designed to determine an optimal hyperbaric chamber compression rate that might reduce the incidence of symptomatic ETD leading to MEB during the compression phase of treatment in a multiplace hyperbaric chamber. Data was collected prospectively over 2,807 elective patient treatments compressed using a U.S. Navy Treatment Table 9 (USN TT9) with a modified ROC. ROC was assigned using two variables, time (10 vs.15 minutes) and slope (linear vs. non-linear compression). Patients were exposed to all four compression schedules in a consecutive daily fashion. We recorded any patient requiring a stop during initial compression due to ear discomfort. Anyone requiring a stop was evaluated post treatment for MEB. Findings were compared to our standard 10-minute linear ROC. Evaluation of the tympanic membrane was accomplished using video otoscopy. Barotrauma when present was classified using both the Teed and O'Neill grading systems. Data was analyzed using basic statistical methods. Results: When comparing four different rates of compression during an elective USN TT9 in a multiplace (Class A) chamber there is a decreased incidence for symptomatic ETD when using a 15-minute linear compression schedule (p-value ⟨0.05). Conclusion: Using a 15-minute linear compression schedule is associated with less symptomatic ETD and less MEB when performing an elective 45 fsw (USN TT9) hyperbaric treatment in a Class A chamber. Asymptomatic ETD and MEB were not considered in this study.

Middle ear barotrauma during hyperbaric oxygen therapy; a review of occurrences in 5,962 patients.

Hyperbaric-associated middle ear barotrauma (MEB) is one of the most common side effects of the exposure to hyperbaric oxygen (HBO2) therapy. This retrospective observational study of 5,962 patients undergoing longterm therapy for chronic conditions took place at the local Diving and Hyperbaric Medicine Unit (DHMU) in Villafranca-Verona (Italy), a DHMU that administers, in multiplace chambers, more than 20,000 HBO2 treatments per year. The study was designed to weight and analyze both the incidence and severity of MEBs at the facility. Thanks to a systematic recording method over eight years, 2003-2010, we observed 549 MEBs (9.2% of all HBO2 treatments). The majority of them were female patients older than 50. MEBs observed were usually of minor complexity, with minimal otoscopic changes (69.03% of our occurrences were registered as Wallace-Teed Grade 1). MEBs were registered in 20.3% of those patients already suffering from difficulties in equalizing ear pressure, and/or presenting ear pain during the initial compression phase (descent) of the hyperbaric treatment. Inflammatory diseases of the upper respiratory tract, with special attention to rhinitis, appear to be a condition capable of predisposing patients in developing MEB. MEB did lead to the suspension of therapy for 89 patients in our case series. This was 16.2% of all the MEBs registered, or 1.49% of all patients who underwent HBO2 at the facility in the considered time lapse.

Methods for preventing middle ear barotrauma in computer-controlled pressurization of monoplace hyperbaric chambers.

Middle ear barotrauma (MEB), one of the side effects of hyperbaric oxygen (HBO2) therapy, sometimes cannot be directly diagnosed during the therapy itself. Instead, its incidence and degree are judged based on subjective statements made by patients when in conversation with medical staff regarding how they feel. To prevent MEB in practice, it is proposed that the tympanic membrane evaluation system and automatic control chamber developed in a previous study be applied as part of a prevention algorithm [16]. The proposed algorithm, which determines and equalizes the unbalanced pressure of a subject based on their tympanic admittance, was evaluated in conjunction with conventional HBO2 therapy in an experiment involving 100 subjects. Among the 50 subjects in the control group who received HBO2 therapy 16 subjects experienced MEB. In contrast, the experimental group of 50 subjects were treated with a hyperbaric chamber protocol incorporating the automatic control system and proposed algorithm. At the conclusion of the treatment, no subjects exhibited middle ear barotrauma. In the case of the control group, while the target pressure was achieved, middle ear barotrauma still occurred. However, in the case of the experimental group, the pressure inside the chamber was adjusted as per the algorithm, which allowed the target pressure for every subject to be achieved without experiencing MEB. When a particular subject was unable to perform any pressure equalization method such as swallowing or the Valsalva maneuver, the chamber was not pressurized based on the tympanic admittance and thus no MEB occurred.

Dual-laser measurement and finite element modeling of human tympanic membrane motion under blast exposure.

Hearing damage is one of most prevalent injuries in military personnel and civilians exposed to a blast. However, the mechanism of how the blast overpressure interacts with the tympanic membrane (TM) and impairs the peripheral auditory system still remains unclear. A 3D finite element (FE) model of the human ear has been developed to predict the blast overpressure transmission through the ear (Leckness et al., 2018), but the model needs to be further validated in TM response to blast pressure. This paper reports the first-ever approach using two laser Doppler vibrometers (LDVs) to measure the motion of the TM when the ear was exposed to a blast. Five fresh human temporal bones were used in this study with a pressure sensor inserted near the TM to measure the pressure reaching the TM (P1). The temporal bone was mounted in a "head block" and exposed to blast at the overpressure around 35 kPa measured at the entrance of the ear canal (P0). The movements of the TM at the umbo and the "head block" were measured simultaneously by two LDVs and the exact motion of the TM was determined by subtracting the head block motion from the TM data. Results include that the maximum TM velocity was 12.62 ±â€¯3.63 m/s (mean ±â€¯SD) and the displacement was 0.78 ±â€¯0.26 mm. The peak-to-peak displacement normalized by the P0 pressure was 22.9 ±â€¯6.6 µm/kPa. The frequency domain analysis indicated that the spectrum peaks were located at frequencies below 3 kHz. The TM motion was then compared with that calculated from the FE model of the human ear with the measured P0 pressure wave applied at the ear canal entrance. The FE model-derived TM displacement under blast overpressure was consistent with the experimental results. This study provides a new methodology to determine the behavior of the middle ear in response to blast overpressure. The experimental data are critical for validating the FE model of the human ear for blast wave transduction and understanding the TM damage induced by blast exposure.

The effects of different packing materials on healing and hearing after trauma to middle ear mucosa, an experimental study in rats.

PURPOSE: To compare the performance of Spongostan, Otopore, Spongostan soaked with dexamethasone and Spongostan soaked with Hyaluronic acid (HA) as middle ear packing material after mucosal trauma. METHODS: Twenty rats were divided into 4 groups. In control group (group 1), the middle ear cavities of animals were bilaterally packed with Spongostan; in group 2, with Otopore; in group 3, with Spongostan soaked with dexamethasone; and in group 4, with Spongostan soaked with HA. Auditory brainstem responses (ABRs) were performed preoperatively and 1 and 6 weeks postoperatively. Histological analyses were performed to evaluate the inflammatory reaction and wound healing in the middle ear cavity. RESULTS: ABR recordings demonstrate that threshold level changes from baseline were minor in Otopore and Spongostan soaked with dexamethasone packed ears. Threshold levels were higher in the Spongostan and Spongostan soaked with HA packed ears compared with both Otopore and Spongostan soaked with dexamethasone packed ears. Histological analyses showed that Spongostan caused inflammation more intense than Otopore and Spongostan soaked with dexamethasone. Residual material at postoperative week 6, new bone formation and adhesion were common in the Spongostan group compared with other groups. Fibrosis was more common in Spongostan group compared with other groups but the difference was not significant. CONCLUSION: Otopore appears to be safe and effective for use in otologic surgery. The inflammation, adhesion and new bone formation decreased when Spongostan was used with steroid or HA, when compared to Spongostan alone.

Temporal bone trauma effects on auditory anatomical structures in mastoid obliteration.

PURPOSE: The risk of temporal bone fractures in head trauma is not negligible, as injuries also depend on the resistance and integrity of head structures. The capacity of mastoid cells to absorb part of the impact kinetic energy of the temporal bone is diminished after open cavity mastoidectomy, even if the surgical procedure is followed by mastoid obliteration. The aim of our study was to evaluate the severity of lesions in auditory anatomical structures after a lateral impact on cadaveric temporal bones in which open cavity mastoidectomy followed by mastoid obliteration was performed, compared to cadaveric temporal bones with preserved mastoids. METHODS: The study was carried out on 20 cadaveric temporal bones, which were randomly assigned to two groups. In the study group, open cavity mastoidectomy followed by mastoid obliteration with heterologous materials was performed. All temporal bones were impacted laterally under the same conditions. Temporal bone fractures were evaluated by CT scan. RESULTS: External auditory canal fractures were six times more seen in the study group. Tympanic bone fractures were present in 80% of the samples in the study group and 10% in the control group (p = .005). Middle ear fractures were found in 70% of the samples in the study group and 10% in the control group (p = .02). Otic capsule violating fractures of the temporal bone were present only in the study group. CONCLUSIONS: Mastoid obliteration with heterologous materials after open cavity mastoidectomy increases the risk of fracture, with the involvement of auditory anatomical structures.

An Integrative Model Accounting for the Symptom Cluster Triggered After an Acoustic Shock.

Acoustic shocks and traumas sometimes result in a cluster of debilitating symptoms, including tinnitus, hyperacusis, ear fullness and tension, dizziness, and pain in and outside the ear. The mechanisms underlying this large variety of symptoms remain elusive. In this article, we elaborate on the hypothesis that the tensor tympani muscle (TTM), the trigeminal nerve (TGN), and the trigeminal cervical complex (TCC) play a central role in generating these symptoms. We argue that TTM overuse (due to the acoustic shock), TTM overload (due to muscle tension), and ultimately, TTM injury (due to hypoxia and "energy crisis") lead to inflammation, thereby activating the TGN, TCC, and cortex. The TCC is a crossroad structure integrating sensory inputs coming from the head-neck complex (including the middle ear) and projecting back to it. The multimodal integration of the TCC may then account for referred pain outside the ear when the middle ear is inflamed and activates the TGN. We believe that our model proposes a synthetic and explanatory framework to explain the phenomena occurring postacoustic shock and potentially also after other nonauditory causes. Indeed, due to the bidirectional properties of the TCC, musculoskeletal disorders in the region of the head-neck complex, including neck injury due to whiplash or temporomandibular disorders, may impact the middle ear, thereby leading to otic symptoms. This previously unavailable model type is experimentally testable and must be taken as a starting point for identifying the mechanisms responsible for this particular subtype of tinnitus and its associated symptoms.