|Year : 2020 | Volume
| Issue : 4 | Page : 229-234
Alternobaric vertigo – An uncommon medical hazard
Santosh Kumar Swain, Satyabrata Acharya
Department of Otorhinolaryngology, IMS and SUM Hospital, Siksha “O” Anusandhan University, Bhubaneswar, Odisha, India
|Date of Submission||09-Apr-2020|
|Date of Decision||21-Jul-2020|
|Date of Acceptance||17-Sep-2020|
|Date of Web Publication||5-Jan-2021|
Santosh Kumar Swain
Professor, Department of Otorhinolaryngology, IMS and SUM Hospital, K8, Kalinga Nagar, Bhubaneswar, Odisha 751 003
Source of Support: None, Conflict of Interest: None
Alternobaric vertigo (AV) is a type of barotrauma of the middle ear which occurs if the asymmetric middle ear pressure in both sides. If pressure differential exceeds a threshold, asymmetric stimulation of the labyrinth will occur, leading to vertigo, called as AV. The classical presentations is transient vertigo which appear sudden onset during the time of diving or flying, typically when ascends or when a Valsalva manoeuvre is performed. Other symptoms associated with AV are nausea, vomiting, disorientation and generalised malaise. If the descent or ascent is reversed immediately, vertigo suddenly disappears or may cause sudden spatial disorientation which may lead to catastrophic outcome. AV is often overlooked but this mishap should not be ignored as it may lead to fatal accident. The patient should be properly counselled for aetiology and nature of AV and its potential risks including aspiration and death. This review article focuses on the prevalence, etiopathology, clinical presentations and current management of the AV amongst underwater divers and aviators. This article will surely increase awareness amongst the clinicians and people those are practicing underwater diving or in aviation and help them to resolve this problem to a great extent.
Keywords: Alternobaric vertigo, eustachian tube dysfunction, middle ear barotrauma
|How to cite this article:|
Swain SK, Acharya S. Alternobaric vertigo – An uncommon medical hazard. J Clin Sci Res 2020;9:229-34
| Introduction|| |
Alternobaric vertigo (AV) is a sensation of giddiness or vertigo occurred with stimulation of the peripheral vestibular system induced with asymmetric pressure of the middle ear cavity through the oval and round window membrane. It is a type of vertigo because of the alternating (alterno) pressure (baric) changes, which is seen without any effects on the cochlea/hearing apparatus. The AV was first described by Claes Lundgren in 1965 who documented it as a diving hazard. He also described AV in Swedish Air Force pilots. AV is a benign clinical entity which often affects the persons those travel in environment with altered ambient pressure such as aviation or diving. It occurs by direct result of insufficient or incomplete equalisation, typically when moving from high pressure area to low pressure area. The factors which increase the chance of the AV are upper respiratory tract infections or dysfunction of the eustachian tube. The patient of the AV usually presents with mild vertigo and it transitory in nature which lasts for few minutes along with nausea and vomiting. It usually resolves with technique of equalisation to restore similar pressures between two sides middle ear. A Valsalva manoeuvre should be done during diving or flying, when the asymmetric eustachian tube dysfunction which may cause precipitation of this AV. Person with mild-to-moderate infections of the upper airway should be denied from the high performance flight training or diving. Underwater diving and high altitude flying are becoming a popular nowadays; however, research regarding the fatal complication such as AV very minimal. Hence, they should have knowledge regarding outcome of the underwater diving of skydiving on the auditory or labyrinthine system.
| Methods of Literature Search|| |
Research articles regarding AV were searched through a multiple systemic approach. First, we conducted an online search of the Scopus, PubMed and Medline database with the AV, middle ear barotrauma and hazard of divers and aviators. The abstracts of the published articles were found by this search method and other manuscripts identified manually from citations. This article reviews the details of AV patients along with its important medical problems. This review article shows a baseline from where further prospective studies for AV could be designed and helps as a spur for further research in this medical hazard.
| Prevalence|| |
AV is often unreported because of no ill effects occurred or sometimes patient unable to report due to a panicking condition. One study reported that 27% of the reported cases of AV were related with diving. A study found shows AV in 14% of cases those have finished monitored dives. One study from the Portuguese Air Force pilots reported a prevalence of 29% of AV, possibly an outcome of modern high performance aircrafts. The affected percentage is somewhat higher than documented in earlier studies. The previous studies were done long back and the higher prevalence in this study may be due to higher performance capabilities of modern capabilities. AV was documented in aviators and pilots but more in divers. AV has also been found in animal model by inducing pressure difference between both middle ears of guinea pigs. There has been dramatic increase of number of scuba divers almost with over 9 million certified in the United States in 2015 and around 100,000 new divers per year. Nowadays, scuba diving or sky diving is considered as a recreational activity, but it has several hazards over body even death. Majority of the diving complications are found in the head and neck region. Out of these approximately 65% affect external, middle and inner ear. The most common aetiology for vertigo amongst scuba divers is AV. The incidence of AV within scuba divers is approximately 17%.
| Pathophysiology|| |
The middle ear space is a six walled bony cavity which connect to outside through eustachian tube. It becomes a closed cavity when there will be collapse or obstruction of the eustachian tube. In case of changing altitudes during diving or aviation, it becomes problem. This problem often happens if one end of the eustachian tube is functionally closed [Figure 1] at a different ambient pressure in comparison to another side. Once the volume of the air inside the closed middle ear cavity expands or contracts during ascent or descent, there will be pressure differentials across the middle ear space and the tympanic membrane, as well as inner ear middle ear interfaces which exacerbate with expansion or contraction of the middle ear cavity. If the pressure differential persists between right and left middle ears, there becomes a difference of perception across either vestibular system which presents symptomatically as vertigo. Increase positive pressure of 100–200 mmHg is needed to stimulate the vestibular systems. The study indicated a pressure differential of around 50 cm water between the middle ear cavities when the vertiginous symptom develops.
|Figure 1: (a) Normal functioning eustachian tube in middle ear cleft and (b) showing dysfunction of the eustachian tube in middle ear cleft (red arrow)|
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Dr Charles Bluestones published a patient of AV at ground level due to chronic Toynbee phenomenon in 2012. Bluestone documented the etiopathogenesis of the otitis media in such patient may be associate to abnormal anatomy of eustachian tube. That case was also showing abnormal vestibular function and dysfunction of eustachian tube. To believe Toynbee phenomenon, the surgical treatment was done to replace the blocked grommet with a patent one. Bilateral reduction of the inferior turbinate and adenoidectomy was done to relieve nose block. After surgery, function of eustachian tube became defective; however, vestibular functions come to normal and vertigo relieved. Hence, Bluestone concluded, nose block and Toynbee phenomenon may be associated amongst patients those have vertiginous symptom. The assessment of function of the eustachian tube is an important part to make differential diagnosis in patients with normal tympanic membrane in the absence of middle ear infections but with presence of symptomatology related to eustachian tube dysfunctions such as otalgia, aural pooping, fluctuating hearing loss, tinnitus and vertigo. This suggests that eustachian tube dysfunction must be ruled out before doing vestibular function assessment.
In diving, there are two mechanisms which explain about inner barotrauma followed by AV. These two ways for explanations are explosive and impulsive. When diver descends, the tympanic membrane will be pressed medially as the pressure increases in external auditory canal. This will lead to pressure at the stapes and transmitted to inner ear through oval window. This transmitted pressure at the oval window cause bulging of the round window membrane [Figure 2]. If pressure difference is of more than 90 mmHg (12kPa), the eustachian tube will 'lock' closed which prevent successful Valsalva. Once the diver unable to equalise the pressure by attempting Valsalva, then diver may repeat with forceful Valsalva manoeuvre which increase the intracranial pressure. This transmitted pressure passes through the perilymphatic duct to the cochlea, again increase the pressure in the cochlea, which can cause rupture of the round window membrane or annular ligament. Hence, this rupture by increase in perilymphatic fluid pressure is called as explosive? rupture, whereas the rupture in case of decreased perilymphatic fluid pressure is called as impulsive rupture. This is seen with sudden increase in pressure at the middle ear cavity by forceful Valsalva which is successful in opening of the eustachian tube. If sudden increase of middle ear pressure, the tympanic membrane expands outwards this also pulls the ear ossicles with it. This can lead to tear of the oval or round window. It also causes rupture of the Reissner's or Basilar membrane. Only little pressure differentials are needed to rupture the membranes causing to mixing the perilymph and endolymph.
|Figure 2: Diagram showing pathophysiology of the alternobaric vertigo (yellow arrow-tympanic membrane, red arrow-outward bulged round window membrane and green arrow eustachian tube and black arrow-flow of endolymph)|
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The aggravating factors for AV other than dysfunction of the eustachian tube are previous barotrauma, cold water diving, noise exposure during diving, history of middle ear infections, history of AV and female sex. Superior semicircular canal dehiscence syndrome (SCDS) is an uncommon disorder which occurs due to dehiscence of or temporal bone fracture overlying the superior semicircular canal. Patient with SCDS, diving or flying can manifests in vertigo and vertical torsional eye movements caused by increased pressure of the middle ear in middle ear barotrauma.
Continuous positive airway pressure (CPAP) is a treatment option for obstructive sleep apnoea. CPAP increase the air pressure in the middle ear which does not equalise the outside air pressure, leading to symptoms of the AV. Sudden increase of the middle ear pressure in CPAP can cause excessive movement of the stapes at the oval window area leading to the vestibular stimulations.
| Clinical Presentations|| |
AV is the most common cause for transient vertigo during diving or aviation which typically happens at the time of ascent. AV is 4 times common amongst female than males. As the failure of expanding air in the middle ear cavity to exit through eustachian tube, the raised middle ear pressure on ascent, pushes the tympanic membrane outwards and also compresses the footplate of the stapes into the vestibule of the labyrinth. This leads to a transient sensation of vertigo, disorientation, nausea and vomiting. The vertigo often lasts for several minutes. If vertigo of diver occurs at depth, it can be hazardous. There is sensation of spinning in the direction of the ear with the higher pressure in the middle ear space. The patient also complains tinnitus and occasionally hearing loss. Ear, nose and throat should be properly examined. A patient of vertigo, tinnitus and hearing impairment may be thought as Meniere's disease but when treated with catheterisation of eustachian tube and administration of an air douche, ameliorate the symptomatology. It is an classical type of eustachian tube dysfunction and should be ruled out when considering the Meniere's disease. The tympanic membrane is often retracted and occasionally congested. The patient shows horizontal nystagmus. The quick phase of the nystagmus presents the greatest amplitude and frequency when the eye ball is moved away from the side of disease. Cerebellar tests such as dysdiadochokinesis, past pointing and gait are usually within normal limits. AV may lead to life-threatening situations amongst divers or pilots. Acute transient vertigo may be hazardous to person concerned. A diver in murky water or in darkness receives a little or no visual or any proprioceptive information and so dependent on information from the labyrinthine system. Hence, AV will be dangerous to divers and so eustachian dysfunction or upper respiratory tract infections should be ruled out from the diver before diving or during fitness to dive examination whether a diver will develop into AV or not. Patient with AV often has normal hearing but in some cases present with mild conductive hearing loss. Hearing loss is almost reversible in AV. Severe vertigo is a serious situation which create a grave menace to the diver. AV is often associated with nausea, vomiting and disorientations. During diving, vomiting is usually fatal, particularly if diver with exhausted air supply. Transient vertigo during diving has high risk for disorientation, accidental regulator dislodgement, damage to scuba apparatus and asphyxiation. A study provides detail clinical profile of the AV where incidence, prevalence and distributions are documented.
| Diagnosis|| |
Accurate history taking and clinical examinations help to get accurate diagnosis. In patients of AV, microscopic or oto-endoscopic examination of the ear does not reveal any signs of acute inflammation of the outer ear canal or tympanic membranes. The audiological evaluation is usually done by the pure tone audiometry and tympanometry. Pure tone audiometry will help to assess the hearing level of the patient with middle ear barotrauma. Pure tone audiometry usually shows normal hearing but in some cases present with mild conductive hearing loss. Hearing loss is almost reversible in AV and tympanometry shows type-C tympanogram. Eustachian function test can be done by sonotubometry. The vestibular system can be assessed using caloric video-oculography with analysis of spontaneous and slow phase velocity of the nystagmus. The retrocochlear injury can be assessed by auditory brainstem response. Vestibular function test is easily done by cold caloric test. Videonystagmography or electronystagmography can be used to better localise the exact site of pathology for vertigo. It can be done in hospital setting for better assessment of the severity of the vestibular symptom such as vertigo.
Cervical vestibular-evoked myogenic potential (cVEMP) may be helpful for diagnosis of the AV. VEMP testing is increasing in present days for the diagnosis of the several vestibular pathologies. The response of the VEMP is obtained through the measurement of the stimuli of the sternocleidomastoid muscle from a auditory stimuli. The response of the VEMP is considered as reflection of the vestibulospinal projections towards the neck which provides information regarding the saccule and inferior vestibular nerve. The cVEMP shows a peak-to-peak amplitude difference in two sides with larger peak-to-peak amplitude in affected ear. Diagnostic nasal endoscopic examination confirms the pathology of the nasal cavity and nasopharynx. The nasopharyngeal end of the eustachian tube is better assessed by the endoscopic examination. Sometimes, adenoid hypertrophy obstructs the eustachian tube opening. MRI of the brain is helpful to find the brain lesions at the central vestibular system i.e., brainstem, vestibulocochlear nerve and cerebellum. High-resolution computed tomography is helpful to rule out SCDS and labyrinthine fistula.
AV should be differentiated from certain clinical conditions which confer risk of vertigo or disequilibrium [Table 1]. These clinical entities include Meniere's disease, benign paroxysmal positional vertigo and vertebrogenic dizziness and central diseases. Eustachian tube dysfunction has long been thought as an important cause for hearing loss and tinnitus and vertigo., Hence, patients who show such clinical symptoms should be subjected to a therapeutic test of inflation of the eustachian tube as a first step during through clinical investigations. Divers or aviators should undergo proper evaluation of their eustachian tube function and vestibular system before diving or air flight. Accurate evaluation is required if they have to get proper treatment. If we will not diagnose early, it may lead to serious consequence like perilymph fistula.
| Treatment|| |
The treatment of choice for AV is re-establishing the pressure equilibrium amongst both side middle ears. This is can be done by simple methods such as Valsalva or Toynbee manoeuvre. The transient AV is prevented by adequate self-equalization of the middle ear pressure. AV needs urgent consultation with otolaryngologists and treatment which include application of nasal decongestants such as oxymetazoline and pseudoephedrine, topical and systemic antihistamines, analgesics and antibiotics such as amoxicillin with clavulanic acid. In case of AV, the diver should avoid ascending or descending and control his/her position under the water. At this place, the diver should try to do pressure equalization and expect to feel a gradual resolution of the clinical features. If a diver is able to manage the transient vertigo and pause his/her ascent or descent until their vertigo subsides, then the risks to the diver will be reduced. In severe case of pressure difference, the patient may suffer with ruptured tympanic membrane which may require several weeks to heal. In severe cases, the patient may need surgery such as tympanoplasty. The patient should be treated medically by antihistamines, nasal decongestants and topical nasal steroids for making eustachian tube patent or functional. If the patient of AV is not benefited by medical treatment he/she can be advised for surgery such as myringotomy and grommet insertion. The grommet helps to equalize the middle ear pressure with outside environment and helps to? relieve symptoms. Eustachian tube dilation (ETD) may be advised in case of recurrent or progressive AV. ETD makes eustachian tube patent and functional. The preventive measures should be done such as increased awareness especially amongst pilots and divers and compulsory routine check-up for eustachian tube dysfunction which help to resolve this problem.
| Preventive Measures|| |
Although AV is found amongst divers and pilots, it still an uncommon topic amongst common people. Hence, there should be adequate awareness required about this medical hazard and its sequela. This medical problem is associated in professional liker diver and pilot found in medical literature as a worldwide concern. Training and education are the only methods to make the people aware and prevent this fatal medical problem. Medical examination should be done particularly assessment of eustachian tube function and labyrinthine function before diving or aviation. Prevent the persons with eustachian tube dysfunctions for activities such as diving and flying, so it will prevent AV, perforation of the tympanic membrane, sometimes bleeding from ear and more fatal asphyxia and death. The preventive methods such as increasing awareness amongst professionals by detailed leaflets or poster available at otolaryngology or audiology clinics, flying school and diving centres could be mush helpful. There should also be more research on this uncommon medical hazard and surveys should be done in otolaryngology clinic for tracing the number of visits by divers and pilots for eustachian dysfunction and AV.
AV is a common aetiology for pressure-related vertigo amongst divers and airline pilots. The prognosis of the AV is essentially benign. However, its deleterious effect on divers or aviators during diving or flight, so all possible steps should be taken care for avoiding such hazardous situation. Recreational scuba divers must undergo medical examination for eustachian tube function test and hearing assessment in light of the failure to adequately equalize the middle ear pressure which may result in certain otological hazards such AV. Diving or aviation should be avoided when the person is suffering from upper respiratory tract infections or common cold. The use of nasal decongestants and antihistamines should be advised in cases where pressure equalization is difficult despite the absence of recent upper airway infections. Great care should be done to keep pressure equilibrium with ambient pressure change and avoid unnecessary speedy ascent and descents.
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[Figure 1], [Figure 2]