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Year : 2014  |  Volume : 16  |  Issue : 73  |  Page : 422--426

Stapedial reflex and recruitment: What is the relationship with tinnitus?

Fernando Laffitte Fernandes, Alexandre Caixeta Guimarães, Guilherme Machado de Carvalho, Raquel Mezzalira, Guita Stoler, Jorge Rizzato Paschoal 
 Department of Otolaryngology Head and Neck, University of Campinas, Campinas, Brazil

Correspondence Address:
Dr. Fernando Laffitte Fernandes
126, Campinas, SP, Street Tess´┐Żlia Vieira de Carvalho, P.O. Box - 13083-887


Tinnitus is characterized by an auditory perception of sound, with no stimuli from the external environment. Tinnitus is an increasingly significant complaint, affecting 10-17% of the world population. As a symptom, it should always be considered with pathology in the auditory system. Our study aims to assess the relationship of this symptom with the presence of a stapedial reflex and the phenomenon of recruitment. Medical records of patients complaining of subjective tinnitus during their first consultation in the Outpatient Clinic of the Unicamp Teaching Hospital, in Brazil, between 2011 and 2012 were analyzed. We carried out a study with 65 non-randomized tinnitus individuals using questionnaires, clinical and audiological evaluations. The visual analogue scale was used to characterize the degree of disturbance caused by tinnitus. Statistical tests were performed using the IBM SPSS Statistics 19. No association was found between tinnitus and the presence of acoustic reflex or phenomenon of recruitment. We concluded that there is no relationship between tinnitus, the phenomenon of recruitment or the presence of an acoustic reflex.

How to cite this article:
Fernandes FL, Guimarães AC, de Carvalho GM, Mezzalira R, Stoler G, Paschoal JR. Stapedial reflex and recruitment: What is the relationship with tinnitus?.Noise Health 2014;16:422-426

How to cite this URL:
Fernandes FL, Guimarães AC, de Carvalho GM, Mezzalira R, Stoler G, Paschoal JR. Stapedial reflex and recruitment: What is the relationship with tinnitus?. Noise Health [serial online] 2014 [cited 2023 Jun 2 ];16:422-426
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Tinnitus is defined as the perception of sound by an individual in the absence of an external source. [1],[2] It causes a negative impact on quality of life and can interfere with concentration, sleep, social activities and even emotional stability. [1],[3],[4],[5] It is a complex symptom and often associated with other otoneurologic complaints such as hearing loss, dizziness and hyperacusis. [2]

The causes of tinnitus are varied. The current understanding of tinnitus and associated brain functions is based on multiple theories and hypotheses. [6] Studies from Roberts et al. shows that many auditory structures, such as the dorsal cochlear nucleus, the inferior colliculus and the primary and secondary auditory cortex, as nonauditory structures including the hippocampus, amygdala and cingulate gyrus are associated with tinnitus. Affected neurons by different mechanisms (acoustic trauma, noise-induced hearing loss) begin to respond preferentially to inputs from their unaffected neighbors via horizontal (lateral) connections on their apical dendrites in the tonotopic map. Once their output remains intact, the lateral stimuli is heard in terms of their original cochleotopic tuning as the tinnitus percept. Nonauditory regions may also play a more direct role in the generation of the tinnitus percept and distress behavior caused by tinnitus. The distress behavior is present in many patients with tinnitus. Areas associated with emotion and attention, such as limbic and prefrontal areas are to be involved with this mechanism. perception. Recent evidence attributes chronic tinnitus to the failure of a noise cancellation system mediated by subcallosal structures. In the undamaged brain, this area is responsible for preventing the perception of unwanted sounds. As we can see, multiple areas of the nonauditory system are involved in tinnitus phisiopatology, but current studies do not converge on a consensus regarding the precise role of nonauditory centers in tinnitus. [7] Another accepted theory is that the source of tinnitus stems from an initial dyssynchrony in pre- or post-synaptic neuronal transmission within the peripheral or central nervous system, at cortical or subcortical level. This dyssynchronous transmission interferes with processes involved in maintaining homeostasis for brain, acting as a stimulus that expresses the auditory system dysfunction. This dyssynchrony is expressed in the cerebral cortex and is modulated by various cortical functions [6],[8],[9] It has been hypothesized that medial olivocochlear pathways, which may originate from the primary auditory cortex and ends in outer hair cells, would be able to contribute to the mechanisms that generate tinnitus. [3] These same pathways are involved in mediating the acoustic reflex, which is an involuntary contraction of the stapedial muscle in the middle ear in response to sound stimuli and has also been also related to auditory processing. [10],[11],[12] Therefore, reflex measurement has been shown to be an important resource for the evaluation of efferent auditory pathways. [13],[14]

The response of the acoustic reflex threshold is located between 70 and 100 dB above the hearing threshold, with values equal to or below 60 considered as recruitment and above as no response. [12] Recruitment is as an abnormally-rapid growth in loudness when sound intensity is increased in damaged ears. [15]

There are different methods of evaluating the bothersome effect of tinnitus, from numerical scales to visual analogue scales (VAS), with the VAS the most widely used, as, for example, in Vermeire studies. [16] In a single-blind, randomized, placebo-controlled study of Adamchic et al., authors evaluated the psychometric properties of patient-reported VAS for measuring subjectively perceived tinnitus loudness and annoyance. VAS either for loudness or annoyance showed good test-retest reliability of 0.8 and 0.79, respectively, being considered valid and effective measurements for capturing reductions in tinnitus severity in patients with chronic tinnitus. [17]

Several studies, such as Goldstein and Shulman [15] Bläsing et al., [18] and Guimarães et al., [19] have attempted to establish a relationship between tinnitus and hyperacusis in general, by specific questionnaires. The relationship between these two phenomena is often studied in the literature. However, studies are lacking in the literature concerning the relationship between tinnitus and the recruitment phenomenon and tinnitus and the presence of an acoustic reflex.

The present study aims to establish whether there is a correlation between tinnitus disturbance and the presence of acoustic reflex and recruitment. Much is known about the cochlear physiology, recruitment and the behavior of acoustic reflexes. It can be noted in many patients who have cochlear diseases the presence of tinnitus and even changes in the before mentioned situations. There is a lack of articles in the literature to correlate the annoyance caused by tinnitus and changes in acoustic reflexes and recruitment. We believe that more information and research on such situations can help shed some light on the pathophysiology of tinnitus and help new ventures on the treatment of tinnitus.


Medical records of all patients with tinnitus during their first consultation in the Outpatient Clinic of the Unicamp Teaching Hospital, in Brazil, between 2011 and 2012, were analyzed.

All patients answered a questionnaire [Figure 1] and underwent clinical and audiological evaluations at the time of consultation. The questionnaire aimed to characterize the type, degree of disturbance and the presence of unilateral or bilateral tinnitus. The clinical evaluation included a neurological and ENT examination, and the audiological evaluation which consisted of pure tone audiometry, testing the following frequencies: 250, 500, 1000, 2000, 4000, 6000 and 8000 Hz, speech audiometry and impedance audiometry. The stapedial reflex was measured at frequencies of 500, 1000, 2000, 3000 and 4000 Hz in both ears by an audiologist.{Figure 1}

All patients with tinnitus were included. The majority of patients had long term tinnitus (more than 1 year). The study excluded patients with objective tinnitus, the presence of infectious disease in the middle or external ear under treatment, and incomplete questionnaires. The degree of the tinnitus-related disturbance was evaluated by an ENT doctor during the first appointment according to the VAS (values set between 0 and 10, with zero being no disturbance caused by tinnitus and 10 being maximum disturbance.)

The presence of hyperacusis was defined based on the anamnesis of the patients. No tests were performed, such as loudness discomfort level (LDL), as in other review articles on the subject. [20],[21],[22],[23]

Statistical analyses were conducted with commercially available software IBM SPSS Statistics 19 (Statistical Package for Social Services, Chicago, IL, USA). We compared the degree of tinnitus in the presence or absence of the acoustic reflex, the degree of tinnitus in the presence or absence of the recruitment phenomenon, as well as investigated the association of the presence of hyperacusis with the presence of recruitment for all studied frequencies. Mann-Whitney test was used for all analysis and P < 0.05 was considered significant.

The study was approved by the Research Ethics Committee in our institution.


Sixty-five patients with tinnitus took part in the study. Regarding the hearing levels, 65% of patients showed lowering of hearing thresholds restricted to the frequencies starting from 3.000 Hz. 25% of patients had lower hearing thresholds in all tested frequencies and 10% of patients had normal hearing bilaterally. Regarding patients with hearing loss, the average thresholds at frequencies of 3, 4 kHz and 6 kHz was 36.98 dB, and the average of 500, 1000 and 2000 Hz thresholds was 18.75 dB [Table 1]. Among the 65 patients studied, 41 (63%) were female and 24 (37%) were male. The mean age was 56.5 years for females (minimum: 25 years; maximum: 77 years) and 53.6 years for males (minimum: 41 years; maximum: 74 years). The VAS tinnitus showed an average score of seven (minimum: 3, maximum: 10). Females had a mean score of 7.15 (minimum: 4 and maximum: 10) and males had a mean score of 6.75 (minimum: 3, maximum: 10). The number of patients with bilateral tinnitus was 49 (75.4%); tinnitus in right ear, eight (12.3%); and tinnitus in the left ear, eight (12.3%). The average VAS score for patients with bilateral tinnitus was seven (minimum: 3, maximum: 10); tinnitus in right ear, average of 7.25 (minimum 5 and maximum 9); and left ear, average of seven (minimum: 4, maximum: 10). Of the 65 patients, the acoustic reflex was present in 54 (83%) patients, with the recruitment phenomenon present in 24 (44%) of those 54 patients.{Table 1}

There was neither a significant association between the degree of discomfort of tinnitus evaluated by VAS and the presence of reflexes nor between the degree of discomfort of tinnitus evaluated by VAS and the presence of recruitment for all studied frequencies [Table 2] and [Table 3]. There was no significant association between the degree of discomfort of tinnitus and the presence of the recruitment phenomenon and between the presence of hyperacusis and recruitment presence in any of the studied frequencies [Table 4] and [Table 5]. The statistical analysis took into account the presence of tinnitus in each ear, being considered N = 57 (49 with bilateral tinnitus and 8 with unilateral tinnitus in the right or left ear). There was a trend, but no statistically significant value, of a greater degree of discomfort due to tinnitus in patients who had a stapedial reflex present, compared with the group with absent acoustic reflexes for frequencies of 500, 1000 and 2000 Hz in the right ear, with P = 0.12, 0.11 and 0.06, respectively.{Table 2}{Table 3}{Table 4}{Table 5}


The stapedius muscle plays an important role in the physiology of hearing. Its function can be assessed using the impedance audiometry, where its reflex is measured. For the acoustic reflex to be intact, it is necessary that the middle ear and the afferent and efferent pathways are intact and working. Several pathologies of the middle and inner ear, as well as other otoneurological disorders and systemic diseases, may alter the physiology of the stapedius muscle and its reflex. The relationship of the stapedial reflex and tinnitus is still not well established and lacks data in the literature. However, it is known that the measure of stapedial reflex can cause acoustic trauma because of high volume levels involved, thus triggering the symptom of tinnitus; however, the inverse relationship does not yet have reliable data. [24],[25]

Tinnitus affects between 10% and 17% of the world population, [26] factors determining the degree of tinnitus disturbance have been studied, but there is no consensus. Female sex, older age, binaural or persistent tinnitus and coexistence of other symptoms such as hyperacusis and hearing loss appear to increase the feeling of discomfort and lead to greater impairment in quality of life. [21],[27]

The relationship of tinnitus with the recruitment phenomenon or presence of the acoustic reflex is not yet established, and there are no descriptions in the literature about it. Studies, such as Lena Blasing's [18] and Rene Dauman's, [20] correlate tinnitus with hypersensitivity to sound based on the hyperacusis phenomenon, but not recruitment.

In our study, patients with hyperacusis were also established by specific questionnaire, using a VAS if the hyperacusis was present. Six patients had the hyperacusis, and there was no statistically significant relationship between this phenomenon and the recruitment phenomenon.

Further data collection is required to increase power of statistical analysis and assess the sensitivity of the measurements. Furthermore, research is needed to ascertain whether there is a relation between tinnitus, the presence of acoustic reflex and recruitment.

Limitations of this study are mainly derived from retrospective methodology. This type of analysis is limited to data acquisition, limits the amount of data limits the analysis and related statistics. The power of completion of information should always be ponderas in accordance with the methodology set.

We had difficulties in obtaining data from all patients and therefore exclude a large amount of subjects for the study, who did not complete all the inclusion criteria previously established. In retrospective assessment is difficult to identify clinical details such as tinnitus ranging, as the case of Meniere's. This situation could be a bias, bias that the patient could be with a more or less intense buzz at the time of their clinical evaluation, and this finding was not established.

It should always be also remembered that tinnitus is very psychological, and this could be another bias of our study. The anamnesis (patient's complaint) was used to define hyperacusis, and any tests were performed to determine this clinical condition. There are some tests, like LDL, that some authors used in their evaluation protocols in patients with tinnitus and hyperacusis. It must emphasize that hyperacusis defined by LDL may show different results than the present study. [20],[21],[22],[23]

The findings of this study (no association between tinnitus and the recruitment phenomenon or presence of acoustic reflex. There was also no association between the recruitment phenomenon with hyperacusis complaints) are important because they show the medical experts who deal with tinnitus that these changes assessed by audiometry should not be of great importance in the evaluation of these patients. We also emphasize that further investigations should not be guided by theories of pathologies involving changes such physiological phenomena.

We believe VAS was satisfactory in this study to assess our goals, but to get a dipper into more details about the psychological status and relations of tinnitus with the limbic system, such as distress, other methods should be considered for finding better outcomes in future works.


We concluded that there is no association between tinnitus and the recruitment phenomenon or the presence of acoustic reflex. There was also no association between the recruitment phenomenon with hyperacusis complaints.


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