[Perilymphatic fistula]. / Perilymfatisk fistel.

BACKGROUND: Perilymphatic fistula is leakage of perilymph from the inner ear to the middle ear. The perilymph surrounds the endolymphatic system in the inner ear (cochlea and the vestibular apparatus) and is most likely a cerebrospinal fluid filtrate. Leakage can occur through the fenestra vestibuli (the oval window), the fenestra cochleae (the round window), or pathological openings in the otic capsule. The cause of perilymphatic fistula can be trauma (barotrauma, head trauma, whiplash injury, iatrogenic trauma during ear surgery or ear syringing), chronic otitis media with cholesteatoma, congenital malformations or idiopathic. MATERIAL AND METHODS: We present 15 patients operated at Haukeland University Hospital from 1980 to 1997. RESULTS: Symptoms and signs are not very consistent, but dizziness and hearing loss are usual. The fistula test has low sensitivity and specificity, and otomicroscopy is not diagnostic. Imaging techniques with CT and MRI are seldom helpful unless in cases of inner ear abnormalities. Surgical exploration of the middle ear can be diagnostic, but even then it may in some cases be difficult to determine if a perilymphatic fistula is present. INTERPRETATION: The treatment of suspected perilymphatic fistula is primarily bed rest with elevated head, and avoidance of straining to facilitate spontaneous closure of a possible fistula. If the symptoms continue, or get worse, surgical exploration is indicated. The results are good regarding dizziness, but more uncertain as far as hearing improvement is concerned. Hearing improvement seems to be negatively correlated with the length of the delay before the fistula is closed.

Static stabilometry and repeated testing in a normal population.

BACKGROUND: The purpose of the present study was to see if there is a learning effect of repeated static stabilometric testing, using a protocol suitable for testing postural control in narrow spaces, like hypo- and hyperbaric chambers. HYPOTHESIS: Static stabilometry testing under normobaric conditions is objective and reproducible. With repeated testing, a learning effect may be observed. METHODS: Four groups of healthy individuals were tested ten times under the same four acoustically and visually standardized and normobaric normoxic test conditions on a static balance platform. First, the subjects were asked to stand on a bare platform with the eyes open, thereafter with the eyes closed. This was repeated with a foam rubber mat placed on top of the balance platform. The time interval between the first and the last test sequence was 11 (10-13) days for the test subjects in group I (n = 22), 17 d for group II (n = 13), 31(28-36) days for group III (n = 15) and 115 (49-193) days for group IV (n = 10). RESULTS: Static stabilometry tests in a normal population are objective and reproducible. With repeated tests, a learning effect was observed. The learning effect was largest when standing on a foam rubber mat with eyes closed and when the time intervals between the tests were shortest. There was no difference in sway pattern or learning ability between tall and short test subjects, between subjects with heavy and light body weight or between the sexes.

Effects of hypobaric hypoxia on postural control.

BACKGROUND: While the effects of accelerative forces on the vestibular system have been thoroughly investigated, the effects of hypobaric conditions on the postural system have attracted less attention. The purpose of the study was to investigate if postural control is affected by hypobaric hypoxia. HYPOTHESIS: Moderate hypobaric hypoxia may reduce postural control. METHODS: Subjective and multiple objective measurements of postural control with open and closed eyes were made in 16 military aircrew standing on a static balance platform before, during, and after exposure to an altitude chamber training profile with a maximum altitude of 25,000 ft. RESULTS: No subjective dizziness and no clinical unsteadiness were noted. However, significant changes in body sway were found at the balance platform during hypobaric exposure at 18,000, 14,000 and 8000 ft compared with the baseline registrations. The relative increase in sway movements was greater in the eyes open condition compared with the eyes closed condition, and significant for movements in the anteroposterior plane but not in the lateral plane. Most sway parameters returned to pre-exposure values on return to ground level. CONCLUSIONS: Acute hypobaric hypoxia, corresponding to the tested altitudes, influenced postural control primarily in the anteroposterior plane with eyes open. This is in agreement with other studies showing that vision is the first of the special senses to be altered by lack of oxygen.

[Chaos theory and otoneurologic diagnosis]. / Kaosteori i otonevrologisk diagnostikk.

Current interpretation of signals obtained from ENG (electronystagmography) of patients suffering from vertigo is based on methods developed before computers became standard laboratory equipment. New signal processing methods, based on the use of fast computers, can increase our knowledge of the mechanisms involved in the regulation of the vestibular system. Preliminary results suggests that new analyzing tools from the field of chaos theory may yield information of clinical relevance. At present this would appear to be a promising approach to research in this field.

Balance testing in saturation diving.

UNLABELLED: The literature is sparse and equivocal concerning the possible influence of hyperbaric exposure on postural control and the vestibular system. HYPOTHESIS: Deep heliox diving may influence postural control and the vestibular system. METHOD: Multiple objective measurements of postural control were made in four divers by means of a static balance platform before, during and after an onshore experimental saturation heliox chamber dive of 32 d duration. Saturation pressure was 4.6 MPa, corresponding to a depth of 450 m of seawater (msw). Downward excursions to 470 msw were also performed. Clinical ENT and otoneurological examination, including bithermal caloric vestibular testing with electronystagmography (ENG) was performed before and after the dive. RESULTS: Reduced postural control was detected by the balance platform test in all four divers from approximately 200 msw and deeper. Body sway showed a distinct increase during compression, reaching a maximum value during the bottom phase. The Romberg index was not suitable for describing shifts in postural stability. All sway parameters returned to pre-dive values after surfacing. Immediately post-dive, most caloric responses were reduced, compared to the pre-dive results. CONCLUSION: We conclude that deep heliox diving influences postural control and the vestibular system. Computerized stabilometry is a convenient and sensitive method of monitoring postural control during saturation diving. The path length of the center of pressure (COP) seems to be suitable as a monitoring parameter.

[The Norwegian Antarctic expedition 1989-1990--medical contingency, work and research]. / Den norske antarktisekspedisjonen 1989-90--medisinsk beredskap, arbeid og forskning.

Antarctica is the world's coldest, driest, highest and most windy continent. The ice may reach a thickness of nearly five km, and the greater part of the world's fresh water is bound in this ice cap. The lowest temperature ever measured is -90 degrees C. The weather during this summer expedition was pleasant, and the temperature seldom fell below -30 degrees C. The 35 persons in the land party included two physicians and one nurse. No serious injury or disease occurred. The participants seemed experience an increase in lean body weight and loss of fat during five weeks in tents. Extensive data were collected for medical-psychological projects on immunology, adaptation to cold, exhaustion from cold and stress. Some results have been published in separate reports.

Vestibular problems in diving and in space.

On firm ground our sense of balance is supplied by super abundant input from several sensoric sources. In other environments insufficient or conflicting input may cause vestibular problems. In diving, vertigo may be caused by a variety of influences, like sensory deprivation, optokinetic illusion, asymmetric vestibular stimulation, inner ear barotrauma, decompression sickness, breathing gas toxicity, high pressure neurological syndrome, sea sickness and intense noise. During space flight some of the mentioned mechanisms may contribute to vestibular problems, although space motion sickness being the main cause of concern in this connection.

Hearing deterioration in professional divers: an epidemiologic study.

Hearing acuity was measured in 116 professional divers. After approximately 6 yr they were retested. At most frequencies, the divers had higher hearing thresholds than otologically normal subjects at the same age, both at the first and at the final examination. The divers' hearing deteriorated faster than that of the otologically normal subjects. The young divers' hearing thresholds were lower than in unscreened nondivers at comparable age, but the gap closed gradually with increasing age. Accordingly, the divers' hearing deteriorated faster than that of unscreened nondivers. Some of the divers had suffered permanent hearing loss from acute barotrauma. Considering the regular noise exposure during commercial diving, this must have contributed significantly to the observed hearing deterioration.

Functional capacity of neutrophil granulocytes in deep-sea divers.

Neutrophil granulocytes (PMN) are main defenders against invading microbes. We evaluated the adaptive response of PMN from divers exposed for weeks to high total and oxygen pressures. Under these conditions PMN could be primed to give a heightened respiratory burst upon stimulation with the bacterial peptide analogue, formyl-methionyl-leucyl-phenylalanine (FMLP): blood PMN sampled both shortly after operational saturation dives offshore and during an onshore test-dive gave larger responses than control pre- or post-dive PMN from the same subjects and PMN from laboratory personnel. The assays used measured oxygen consumption, intracellular H2O2 availability, and chemiluminescence. The submaximal responses provoked by the non-metabolizable diacylglycerol analogue phorbol myristate acetate (PMA) were less and less often increased. Such enhanced PMN responsiveness may possibly decrease resistance to skin and other infections that are encountered in divers, if PMN thereby failed to localize correctly to inflamed tissues.

Immediate neurological effects of diving to a depth of 360 metres.

Eighteen divers performed a simulated dive to a depth of 360 metres of seawater breathing a mixture of helium and oxygen. Clinical neurological examinations and neurophysiological tests were performed before and after the dives. Two divers had mild ataxic signs and changed electronystagmography after the dive, and one had impaired vibration sense in one lower extremity. Abnormal EEGs with slow waves and sharp potentials, seen primarily in the temporal regions, occurred in 2 divers. No changes were found in the magnetic resonance imaging brain scans. The divers with evidence of previous central nervous system injury, or a history of unconsciousness or previous decompression sickness seemed more likely to develop neurological signs after these deep dives. This study shows that deep diving may induce immediate neurological changes. We recommend that future deep divers have a neurological examination and 2 separate EEGs included in their medical examinations.

Alternobaric vertigo in professional divers.

The present investigation was part of a project performed to detect possible effects of diving on the cochleovestibular system. A group of 194 professional divers were interviewed, examined otologically, and their hearing was tested audiometrically. Caloric vestibular tests were performed in 48 subjects. The interview reviewed age, diving experience, previous ear disease or injury, head trauma, noise exposure during diving and during spare-time activities, eye color, tobacco habits, and the occurrence of vertigo during diving. Useful information regarding vertigo was obtained from 193. Of the 76 (39%) who had experienced vertigo, 64 (33%) were classified as alternobaric vertigo (AV), a type of vertigo caused by asymmetric middle ear pressure. A stepwise multiple logistic regression analysis was performed to detect variables contributing to the presence of AV. Variables having a statistically significant association with AV were previous barotrauma of the ear (P less than 0.05) and noise exposure during diving (less than 0.05). AV was most frequently encountered when diving during a common cold. In this sample of divers, AV did not lead to any serious or critical situations.

Facial baroparesis: a review.

If impaired eustachian tube function causes an overpressure to remain in the middle ear after ascent in diving or aviation in a subject with a defect in the wall of the facial canal, an ischemic neurapraxia of the seventh cranial nerve may occur. This type of facial palsy is designated facial baroparesis, baroparesis facialis, or alternobaric facial palsy. If the middle ear pressure is asymmetric the subject may also have alternobaric vertigo. A causative relationship between middle ear overpressure and facial palsy is supported by the palsy's rapid onset following a reduction in ambient pressure and by its quick disappearance after either an increase in ambient pressure or release of the middle ear overpressure. Transient compression-induced ischemic neurapraxia of the facial nerve is also demonstrated in animal experiments. A similar palsy, ischemic neurapraxia of the fifth cranial nerve due to compression in the maxillary sinus, has been reported in divers. Although it is under-reported, facial baroparesis occurs infrequently, with 23 subjects mentioned in the available literature. Nevertheless, it is important to be aware of its existence, because misdiagnosis as type II DCS or air embolism results in unnecessarily long recompression treatments and pointless delay of resumption of diving. In the worst case, a misdiagnosis might cause a diving license to be revoked.