The influence of middle ear pressure changes on the primary vestibular neurons in guinea pigs

Tympanostomy tube placement for pressure-sensitive vertigo

Objective

To evaluate tympanostomy tube placement in patients with pressure-sensitive vertigo.

Methods

Retrospective case series.

Results

Six patients with pressure-sensitive vertigo reported resolution of their vertigo and other vestibular symptoms after placement of the tympanostomy tubes. All recurrences of symptoms were due to either extrusion or plugging of the tubes. All patients fulfilled the criteria for vestibular migraine. None of the patients had superior canal dehiscence on imaging or precedent event that triggered the problem, and all had a negative fistula test.

Conclusion

Tympanostomy tube placement should be considered in selected patients with vertigo exacerbated by seemingly small changes in atmospheric pressure (e.g., just prior to thunderstorms, air travel, or travel to the mountains). By eliminating the capability of the tympanic membrane to sense changes in pressure with a tube, patients with pressure-induced vertigo (in the absence of perilymph fistula or superior canal dehiscence) may have relief of their symptoms.

Level of Evidence IV

SCUBA Medicine for otolaryngologists: Part I. Diving into SCUBA physiology and injury prevention

OBJECTIVES

Introduce pertinent self-contained underwater breathing apparatus (SCUBA) physiology and corresponding terminology. Appreciate the scope of diving and related otolaryngological injury. Illustrate pathophysiologic mechanisms for diving injuries. Summarize strategies for ear, paranasal sinus, and lung barotrauma prevention, including medical optimization and autoinsufflation techniques.

METHODS

We conducted a review of the available medical and diving literature in English, German, Spanish, Italian Turkish, and French to determine the degree of evidence or lack thereof behind recommendations for treating SCUBA divers. The databases of PubMed, Ovid Medline, and the Cochrane library, as well available textbooks, were queried for relevant data.

RESULTS

Divers are subjected to large pressure gradients within the first few meters of descent. This can lead to gas embolism formation as well as barotrauma secondary to gas expansion/compression in potential closed spaces such as the middle ear, paranasal sinuses, and lungs. Physicians can minimize the risk of injury by counseling patients regarding proper equalization and descent/ascent techniques, and optimizing sinonasal and eustachian tube function. The use of decongestants is controversial.

CONCLUSIONS

Diving is an increasingly popular sport with predominantly otolaryngologic manifestations of injury and disease. Treating SCUBA divers requires a firm understanding of how physiology is altered underwater. This review presents the relevant background information using illustrations to understand the environmental forces acting on divers and how to prevent injury. Laryngoscope, 130:52-58, 2020.

Lowering barometric pressure induces neuronal activation in the superior vestibular nucleus in mice

Weather changes accompanied by decreases in barometric pressure are suggested to trigger meteoropathy, i.e., weather-related pain. We previously reported that neuropathic pain-related behavior in rats is aggravated by lowering barometric pressure, and that this effect is abolished by inner ear lesions. These results suggest that mechanisms that increase vestibular neuronal activity may parallel those that contribute to meteoropathy generation. However, it remains unknown whether changes in barometric pressure activate vestibular neuronal activity. To address this issue, we used expression of c-Fos protein as a marker for neural activation. Male and female mice were placed in a climatic chamber, and the barometric pressure was lowered by 40 hPa, from 1013 hPa, for 50 min (LP stimulation). The total number of c-Fos-positive cells in the vestibular nuclei was counted bilaterally after LP stimulation. We also video-recorded mouse behaviors and calculated the total activity score during the LP stimulation. LP stimulation resulted in significant c-Fos expression in the superior vestibular nucleus (SuVe) of male and female mice. There was no effect of LP stimulation on the total activity score. These data show that distinct neurons in the SuVe respond to LP stimulation. Similar mechanisms may contribute to the generation of meteoropathy in humans.

Alternobaric vertigo--really a hazard?

OBJECTIVE

To determine the prevalence of alternobaric vertigo (AV) in sport divers and to find out whether AV led to dangerous situations underwater. Furthermore, to examine whether objective neurootologic tests are associated with the manifestation of AV.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Sixty-three sport divers with an average diving experience of 10 years and 650 dives were questioned regarding their medical and diving history and the manifestation of vertigo during diving.

METHODS

Microscopic otoscopy, tympanometry, stapedius reflexes, hearing threshold for air and bone conduction, caloric video-oculography including analysis of the slow-phase velocity of the nystagmus, acoustic brain stem responses, and magnetic resonance imaging were performed to find possible differences between divers with and without AV.

RESULTS

We found 17 divers with AV (27%). There was no significant difference in all measured parameters apart from sex and history of middle ear equalization difficulty in divers with AV. Ten (59%) of 17 female divers and 7 (15%) of 46 male divers experienced AV, representing a significant sex difference (p < 0.001). Correlation with our divers' outpatient clinic revealed that female divers had a significantly higher incidence of middle ear equalization disorders which could be an explanation for the predominance of female divers with symptoms of AV. None of the divers reported any dangerous or life-threatening situations following AV. Whether AV leads to dangerous situations underwater remains unclear, but this hypothesis is not supported by our data.

CONCLUSION

Alternobaric vertigo is a common finding in divers. In our study group, female divers had a four-time higher risk to suffer AV. Our data do not support the thesis that AV is a life-threatening condition.

Cochlear aqueduct flow resistance depends on round window membrane position in guinea pigs

The resistance for fluid flow of the cochlear aqueduct was measured in guinea pigs for different positions of the round window membrane. These different positions were obtained by applying different constant pressures to the middle ear cavity. Fluid flow through the aqueduct was induced by small pressure steps superimposed on these constant pressures. It was found that the resistance for fluid flow through the aqueduct depended on the round window position but not on flow direction. The results can be explained by special fibrous structures that connect the round window with the entrance of the aqueduct. It was also found that the equilibrium inner ear pressure depends on middle ear pressure, indicating that the aqueduct does not connect the inner ear with a cavity with constant pressure.

Middle ear pressure in patients with dizziness

The middle ear pressure was analyzed in 112 patients with dizziness. In 37 patients with Meniere's disease, the middle ear pressure on the low-pressure side was significantly lower, the middle ear pressure difference (between the high and low sides) was significantly larger, and the maximum compliance on the low-compliance side was significantly lower than in normal volunteers. The middle ear pressure difference was significantly larger during periods of dizziness or recurrent dizziness than at the time of remission. In patients with Meniere's disease, a middle ear pressure difference of more than 50 decapascals was significantly more common among those with abnormal blood gas levels than among those with normal blood gas levels. In 27 patients with cervical vertigo and 15 patients with vertebrobasilar insufficiency, the middle ear pressure difference was also significantly larger than in normal volunteers. These results suggest that the middle ear pressure difference might be closely related to dizziness in Meniere's disease and less closely related in cervical vertigo or vertebrobasilar insufficiency. The middle ear pressure difference might also be related to abnormal blood gas levels in patients with dizziness.

Inhibition of experimentally induced endolymphatic hydrops by middle ear ventilation

The tympanic membrane was perforated (n = 19) or a tube was inserted into the middle ear through the wall of the tympanic bulla (n = 6) immediately after blockage of the endolymphatic duct in guinea pigs. Total cochlear endolymph volume and volumes in each cochlear turn were determined from serial sections of the temporal bones and volume changes were analyzed statistically by comparison with hydropic controls without treatment (n = 12). Results showed that both middle ear ventilation procedures significantly reduced the subsequent development of endolymphatic hydrops. This inhibition of hydrops was presumed to be due to pressure release into the middle ear and/or improved oxygenation of the middle and inner ears. Findings suggest the possible merit of a tympanostomy as a treatment for Meniere's disease in carefully selected patients refractory to medical management.

Alternobaric and hyperbaric oxygen therapy in the immediate and long-term treatment of Menière's disease

Forty-five patients suffering from Menière's disease were submitted to pressure chamber therapy: 20 with constant pressure (2.2 ATA, hyperbaric treatment) and 25 with continuous variations in pressure levels (from 1.7 to 2.2 ATA, alternobaric treatment). Oxygenation therapy consisted of one session per day lasting 90 minutes for 15 days during the acute attacks followed by five consecutive sessions per month during a follow-up of two years. For a control group we used 18 patients treated with 10 per cent intravenous glycerol during the acute episode and 8 mg tid of betahistine thereafter. We compared hearing loss, vertigo and tinnitus in the three groups 15 days after starting treatment and at the end of the follow-up, according to the criteria suggested by the 1995 Committee on Hearing and Equilibrium. We found no statistically significant differences in recovery from the cochlear-vestibular symptoms in the three groups at the end of the first 15 days of therapy, whereas hyperbaric and, in particular, alternobaric treatment permitted a significant control of the principal attacks of vertigo during the follow-up period. Hearing loss also showed a more significant and more persistent improvement in the patients treated with alternobaric oxygenation compared to the patients in the other two groups.

The influence of vestibular and cochlear aqueducts on vestibular response to middle ear pressure changes in guinea pigs

The responses of primary vestibular neurons and perilymphatic pressure changes to middle ear pressure were investigated in guinea pigs with obstructed vestibular or cochlear aqueduct (closed VA or closed CA group) in order to clarify the influence of VA and CA on pressure-induced vestibular response. Although the neural response rates and the amount of perilymphatic pressure change in the closed VA group resembled those in the control group, these values in the closed CA group were higher than in the control group. Patency of the CA had a more significant effect on the vestibular response to middle ear pressure change than patency of the VA.