Otology & Neurotology 26:1204–1207 Ó 2005, Otology & Neurotology, Inc.
Inner Ear Decompression Sickness and Mal de Debarquement *Dror Tal, *Liran Domachevsky, *Ronen Bar, *Yochai Adir, and †Avi Shupak *Motion Sickness and Human Performance Laboratory, Israel Naval Medical Institute, IDF Medical Corps, and †Department of Otolaryngology–Head and Neck Surgery, Carmel Medical Center and the Otoneurology Unit, Lin Medical Center, Haifa, Israel
Objective: To present a case series of vestibular symptoms appearing after combined sailing and diving activity, and to discuss the differential diagnosis and the workup algorithm. Study Design: Case series. Setting: Tertiary referral center. Patients: Three patients aged 25 to 31 years suffering from unsteadiness and movement sensations after sailing and scuba diving. Interventions: Neurotologic evaluation and recompression therapy in a hyperbaric chamber. Main Outcome Measures: The increasing popularity of marine sports and leisure activities has resulted in the exposure of a growing number of people to unique abnormalities not encountered under terrestrial conditions. The otolaryngologist who is involved in the care of these patients is required to
diagnose and treat diving-related sinus and ear injuries such as barotrauma and decompression sickness, and also to be familiar with sailing-related disorientation syndromes such as seasickness and mal de debarquement. Treatment modalities for the various abnormalities differ significantly, and early commencement of treatment is often crucial for a successful outcome. Conclusion: Whenever doubt exists, recompression treatment must be instituted as soon as possible because of the potential for severe sequelae if the patient is left untreated, and because the risks involved in this therapy are minimal. Key Words: Barotrauma—Decompression sickness—Hyperbaric oxygen—Inner ear—Mal de debarquement—Seasickness—Vestibular function tests. Otol Neurotol 26:1204–1207, 2005.
The attractiveness of combined diving and sailing activities, and the inaccessibility of some of the world’s most beautiful and undamaged diving sites via land, have recently increased the popularity of scuba (selfcontained underwater breathing apparatus) diving sailing trips. Unfortunately, participants in this leisure activity are potentially exposed to both the vestibular insults of diving (1) and sensory mismatch situations that might lead to the syndrome of mal de debarquement (sickness of disembarkment) (2). We describe three female divers who suffered four events of unsteadiness and a sensation of movement that appeared on disembarking after 2 to 6 days of intensive diving. The differential diagnosis is discussed and a workup algorithm is proposed focusing on the identification of injuries that require immediate therapy.
CASE REPORTS Case 1 A 31-year-old woman complained of a sensation of movement, unsteadiness, and fullness of the right ear that appeared after 4 days of intensive compressed-air scuba diving during a boat trip in the Red Sea. The symptoms appeared 5 hours after her last dive immediately on disembarking from the boat and resembled the ship motion sensation she had experienced during the sea voyage. The patient reported significant seasickness while at sea that was self-treated by dimenhydrinate. A review of the diving log revealed repeated violations of the required decompression stops, as recommended by the U.S. Navy diving manual (3) in 8 of the 10 dives the patient had performed. Her medical history was unremarkable. Physical examination 24 hours after disembarking was significant for posture abnormalities, as reflected by the Fukuda stepping test and an inability to perform tandem walking. Audiometry and tympanometry were normal. The patient was treated in the hyperbaric chamber by hyperbaric oxygenation (HBO2) according to U.S. Navy Treatment Table 6 (3)
Address correspondence and reprint requests to Avi Shupak, M.D., Motion Sickness and Human Performance Laboratory, Israel Naval Medical Institute, P.O. Box 8040, 31 080 Haifa, Israel; E-mail:
[email protected] Drs. Tal and Domachevsky contributed equally to the study.
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INNER EAR DECOMPRESSION SICKNESS 26 hours after the symptoms first appeared. She did not report any symptomatic improvement on completion of the recompression treatment, and the physical examination revealed similar findings. In a follow-up examination conducted 12 hours later, the right ear fullness had resolved but the patient still complained of giddiness despite a completely normal otoneurologic examination. Electronystagmography (ENG) and the Sinusoidal Harmonic Acceleration test showed no vestibular derangement. The patient reported resolution of her sensation of movement after a further 3 days. The main differential diagnosis in this case included mal de debarquement (MD) and vestibular decompression sickness. The inappropriate decompression stops, ear fullness, and positive findings on posture testing warranted recompression treatment. A delayed response to HBO2 treatment is frequently observed in divinginduced vestibular insults and may be explained by continuous irritation of the end organs secondary to ischemia and labyrinthine membranous tears (4). Case 2 A 26-year-old woman complained of rocking and swaying that appeared after 2 days of scuba diving during a boat trip. She had suffered from seasickness aboard the boat but took no medication. Violation of the required decompression stops during the ascent phase of the dive was found in four of the six dives the patient had performed. Physical examination 18 hours after symptoms appeared showed no pathologic findings. Audiometry documented a previously known bilateral sensorineural hearing loss of 40 dB at 3 to 4 kHz. Tympanometry and ENG were normal. The patient reported spontaneous resolution of her symptoms after 2 days. Despite the omitted decompression, the otoneurologic evaluation was negative for any new cochleovestibular damage. Valid treatment options for omitted decompression include short HBO2 treatment or normobaric 100% oxygen breathing when the patient presents soon after the dive, or watchful waiting for late presentation (5). The lack of objective findings on physical examination and laboratory evaluation, the known association between MD and seasickness (2), and the complete and spontaneous recovery, all favored a final diagnosis of MD. Case 3 A 25-year-old woman complained of unsteadiness and a swinging sensation that first appeared 90 minutes after disembarking from a 6-day diving safari, 3 hours after her last dive. The patient presented at our institute 4 days later when she began to notice memory deficiency and an inability to concentrate during her work as a lawyer. An inappropriate decompression schedule was identified for the last 2 of the 11 dives the patient had performed. She had no symptoms of seasickness while at sea, and her medical history was unremarkable. Physical examination, audiometry, tympanometry, ENG, and the Sinusoidal
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Harmonic Acceleration test were all within normal limits. Computerized cognitive function tests showed a decrement in short-term memory and prolonged reaction time. The patient was treated by HBO2 at 2.5 atm absolute for 90 minutes, with no significant improvement on completion. The symptoms and the cognitive insult resolved spontaneously 2 days later. The same patient was involved in a similar incident 8 months later. On this occasion, she suffered from movement sensation, unsteadiness, headache, nausea, and diarrhea that appeared 3 hours after landing and 4 hours after her last dive. Omitted decompression was found in the last two of the six dives the patient had performed. Complete physical examination 6 hours after the symptoms appeared was normal. The patient was treated in another medical center according to U.S. Navy Recompression Table 5 (3), but no improvement in her symptoms was noted. A follow-up examination conducted 4 days later at our institute showed inability to perform closed-eyes tandem walking. Audiometry showed normal hearing. Cognitive tests revealed decreased spatial orientation. The patient received an additional HBO2 treatment at 2.5 atm absolute for 90 minutes, with no significant improvement. She reported complete resolution of her symptoms 1 week later. The association of repeated omitted decompression with cognitive derangement and disequilibrium suggested a diagnosis of cerebral and vestibular decompression sickness. The recurrence of these symptoms despite only a minor violation of the required decompression stops suggests the possibility of a right-to-left shunt, with cerebral air emboli secondary to a patent foramen ovale (6,7). Clinical benefits of HBO2 for decompression sickness might be anticipated even days after symptoms first appear. The current approach is for such treatment to be given up to 1 week after the onset of symptoms (8).
DISCUSSION Exposure to nonterrestrial conditions during scuba diving and sailing represents a potential risk to the inner ear organs and sense of orientation. Whereas divingrelated inner ear injuries are potentially irreversible unless promptly diagnosed and treated, postdive vestibular symptoms might also result from MD, which requires only conservative treatment. The otolaryngologist, who may face the challenge of reaching the correct diagnosis and administrating the required treatment, should familiarize him- or herself with the differential diagnosis and main diagnostic clues of these clinical entities. MD is the sensation of swaying, swinging, unsteadiness, and disequilibrium that appears in some individuals on returning to land, mostly after exposure to motion on a boat or in an airplane. MD differs from motion sickness and seasickness in that, during the period of motion, subjects are predominantly symptom Otology & Neurotology, Vol. 26, No. 6, 2005
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free (9). Despite significant symptoms on leaving the motion environment, no signs of vestibular end-organ or central pathway abnormality can be found (10). In most cases, complete resolution takes place after minutes to days (2). In a small number of patients, the symptoms may last for months to years and are largely refractory to treatment (9). It has been suggested that the reasons for increased susceptibility to MD are delayed readaptation to the stable environment and hormonal interactions with the vestibular system (11). A sensation of unsteadiness after diving might be related to inner ear barotrauma or inner ear decompression sickness, although most divers will suffer from rotary vertigo, nausea, vomiting, and severe disequilibrium immediately after the insult, and some will report hearing loss and tinnitus (4). Inner ear barotrauma is often associated with middle ear pressure equalization difficulties. Unsuccessful forceful attempts at middle ear clearing cause an increase in intracranial pressure. This will then be transmitted to the inner ear through the vestibular and cochlear aqueducts, causing stress rupture of the labyrinth and window membranes (5). The pathophysiology of decompression sickness involves the formation and growth of inert gas bubbles within fluids and tissues. This takes place whenever there is a rapid drop in ambient pressure to a level lower than that required to keep the inert gas in solution. Inner ear decompression sickness is caused by gas bubbles within otic fluids and microvessels (12). The obstruction of microvessels, mainly the venous microcirculation in the stria vascularis, spiral ligament, and semicircular canals, leads to hemorrhage and protein exudates in the cochlea and to irritation of the semicircular canal endosteum that may eventually develop into fibroosseous labyrinthitis (13). Whenever the illusion of movement appears after a dive cruise, the physician must make a differential diagnosis that takes into account all possible sources of
TABLE 1.
unsteadiness related to sailing and diving. The main possible diagnoses are detailed in Table 1. Despite the differences in presentation and in the physical and laboratory findings, an accurate diagnosis cannot always be reached because of overlapping signs and symptoms (1). The physician may therefore be unable reach a clear-cut diagnosis, so that any decision regarding treatment and the mode of therapy to be used must be made on the basis of a workup algorithm that takes into account the most probable diagnosis, the need for immediate treatment, and the possible risks and side effects of the suggested treatment. The Most Probable Diagnosis To elucidate the most probable diagnosis, the physician should carefully consider the dive profile, which includes the maximal dive depth, the time the diver spent at that depth (bottom time), and whether the required decompression stops to avoid liberation of free gas from the tissues were carried out during the ascent from the dive (3). Severe injury may occur even despite meticulous adherence to decompression tables, in the presence of risk factors that may enhance the accumulation of inert gases in tissues or slow their release (5). These include obesity, poor physical fitness, low water temperature, a high level of physical activity during the dive, alcohol consumption, elevated arterial carbon dioxide pressure, the presence of a patent foramen ovale, advanced age, female gender, and repeated dives. Other factors that should be taken into account include existing risks for inner ear barotrauma, the time at which symptoms appeared in relation to the dive profile, the presence of associated symptoms of decompression sickness, and ear clearing difficulties. A thorough physical examination is required, with special emphasis on neurologic and otolaryngologic tests, to guide the physician to the most probable diagnosis. The physician’s decision as to the appropriate treatment should be
Differential diagnosis of sailing and diving-related illusory motion sensations
Diagnosis
History
Mal de debarquement
Symptoms appear on or soon after disembarkation; highly associated with seasickness; more prevalent in female subjects Symptoms mostly appear during descent on a dive; middle ear pressure equalization difficulties with forceful attempts at ear clearing
Unsteadiness, disequilibrium, rocking, swaying
None
None
Vertigo, nausea, vomiting, ataxia, tinnitus, hearing loss, sensation of fullness in the affected ear
Otoscopic findings of middle ear barotrauma, nystagmus, posture abnormalities
Occurs during ascent or postdive; other decompression sickness symptoms coexist; associated with violation of decompression tables and breathing helium-oxygen mixtures
Vertigo, nausea, vomiting, ataxia, tinnitus, hearing loss, sensation of fullness in the affected ear
Nystagmus, posture abnormalities, normal otoscopy
Vestibular testing (ENG, SHA) indicating vestibular end-organ insult; audiometry reveals sensorineural or mixed hearing loss Vestibular testing (ENG, SHA) indicating vestibular end-organ insult; audiometry reveals sensorineural hearing loss
Inner ear barotrauma
Inner ear decompression sickness
Symptoms
ENG, electronystagmography; SHA, Sinusoidal Harmonic Acceleration (test). Otology & Neurotology, Vol. 26, No. 6, 2005
Signs
Laboratory findings
INNER EAR DECOMPRESSION SICKNESS based mainly on the dive history, as detailed above, and the findings on physical examination. Treatment Urgency Whereas inner ear barotrauma and MD may be treated conservatively (1,9), decompression sickness requires immediate treatment by HBO2 to avoid severe sequelae (4,5). Time-consuming laboratory and imaging investigations, although of paramount importance for completion of the diagnostic workup, should be deferred until after the main recompression treatment if there is a reasonable clinical suspicion of decompression illness. Side Effects and Risks of Treatment The main side effects of hyperbaric oxygen therapy are barotrauma of the middle ear and paranasal sinuses, and cerebral and pulmonary oxygen toxicity. These are usually avoided in the vast majority of cases by careful adherence to treatment profiles designed specifically to prevent them. However, in the case of an inaccurate diagnosis, the treatment of inner ear barotrauma with hyperbaric oxygen would be extremely harmful, because it might extend the insult to the inner ear. Therefore, in the event of any doubt regarding a diagnosis of inner ear barotrauma versus inner ear decompression sickness, or whenever both conditions are present, it is advisable to administer hyperbaric oxygen after paracentesis or the insertion of ventilation tubes (1). CONCLUSION This case series represents an interesting dilemma regarding the differential diagnosis of MD and divingrelated insults. Physicians will face this conflict more frequently in the future because of the increased popularity of scuba diving sailing trips. We believe that whenever doubt exists, recompression treatment must be instituted as soon as possible because of the potential for
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severe sequelae if the patient is left untreated, and because the risks involved in this therapy are minimal.
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