Tinnitus as a warning for preventing vasovagal syncope

[Auditory phenomena as differential diagnostics to tinnitus]

INTRODUCTION

In the auditory system, subjective tinnitus is known as phantom perception. Humans also report illusionary misperceptions of real listening impressions and complex scene-like acoustic fantasies without external hearing stimulus. The exact pathophysiological relationships of the auditory phenomena are still unclear. Important comorbidities include hearing loss, brain disease and mental disorders.

METHODS

In a literature search in the PubMed database, publications were evaluated until March 2021 on the search terms tinnitus, palinacousis, pareidolia, synesthesia, aura, acoustic hallucination with regard to similarities and differences to subjective tinnitus.

RESULTS

Subjective tinnitus can occur together with other auditory phenomena in an individual. Diagnostically important is the relationship between hearing loss and tinnitus as well as between tinnitus and hearing loss in the corresponding frequency range. With hearing loss, other auditory phenomena may occur.

CONCLUSION

The occurrence of various auditory phenomena simultaneously in a person suggests an auditory perceptual continuum with common physiological processing structures. People with hearing loss should be asked about the various auditory phenomena. For all auditory phenomena, audiometric examination should be part of the diagnostic standard.

Primary vascular dysregulation syndrome: Possible implications for inner ear acute diseases?

Primary vascular dysregulation syndrome has been reported as a possible cause for different eye diseases. Signs or symptoms of this syndrome not only may consist in a series of ocular disorders, as they possibly concern or are associated to various systemic conditions; even the damage of another terminal sensory organ as the inner ear is reported among the possible associations. Herein, the analogies between eye and inner ear are outlined, analyzing the PVD profile that well corresponds to our widely described model of subject without organic cardiovascular impairment but prone to inner ear acute disturbances. Actually, in absence of a recognized cause the latter can be due to a systemic dysregulation like the described one concerning ocular disorders.

Inner ear symptoms: can we use them to approach cardiovascular diseases?

Sensory organs are programmed to detect external stimuli, and inform about possible threats. In general, they are characterized by a complex architecture, a highly energy-requiring function, a peripheral location and a vascular supply depending on a terminal circulation usually under systemic control. Their function may be highly sensitive to more general disorders primarily involving other organs or physiological systems. Consequently, the onset of transient or persistent symptoms of impairment of sensory organs might be the expression of abnormalities in the integrity of more general systems, especially in the elderly population. In the otologic area, despite the availability of evidence supporting the negative impact of some systemic conditions negatively affecting the local blood supply at the labyrinth level, the possibility that the inner ear can reveal the presence of sub-clinical, non-otologic disorders has never been the topic of a constructive investigation. The present review summarizes the preliminary available evidence suggesting a possible negative impact of early systemic hemodynamic changes on the function of the inner ear, as well as the possibility that some audiological symptoms may play some role in the early detection of cardiovascular diseases. In particular, we hypothesize that some cardiovascular diseases may cause an impairment in correct labyrinthine function as a result of a negative interaction between systemic hemodynamic changes, a reflex activation of the autonomic nervous system, and a local vascular response. A multidisciplinary approach to the interpretation of inner ear disorders may increase the possibility of an earlier recognition and understanding of systemic dysfunctions in clinical practice.

Sinusoidal galvanic vestibular stimulation (sGVS) induces a vasovagal response in the rat

Blood pressure (BP) and heart rate (HR) were studied in isoflurane-anesthetized Long-Evans rats during sinusoidal galvanic vestibular stimulation (sGVS) and sinusoidal oscillation in pitch to characterize vestibular influences on autonomic control of BP and HR. sGVS was delivered binaurally via Ag/AgCl needle electrodes inserted over the mastoids at stimulus frequencies 0.008-0.4 Hz. Two processes affecting BP and HR were induced by sGVS: 1) a transient drop in BP (≈15-20 mmHg) and HR (≈3 beat*s(-1)), followed by a slow recovery over 1-6 min; and 2) inhibitory modulations in BP (≈4.5 mmHg/g) and HR (≈0.15 beats*s(-1)/g) twice in each stimulus cycle. The BP and HR modulations were approximately in-phase with each other and were best evoked by low stimulus frequencies. A wavelet analysis indicated significant energies in BP and HR at scales related to twice and four times the stimulus frequency bands. BP and HR were also modulated by oscillation in pitch at frequencies 0.025-0.5 Hz. Sensitivities at 0.025 Hz were ≈4.5 mmHg/g (BP) and ≈0.17 beat*s(-1)/g (HR) for pitches of 20-90°. The tilt-induced BP and HR modulations were out-of-phase, but the frequencies at which responses were elicited by tilt and sGVS were the same. The results show that the sGVS-induced responses, which likely originate in the otolith organs, can exert a powerful inhibitory effect on both BP and HR at low frequencies. These responses have a striking resemblance to human vasovagal responses. Thus, sGVS-activated rats can potentially serve as a useful experimental model of the vasovagal response in humans.