Distortion product otoacoustic emissions in diabetics with normal hearing

Study of auditory pathways in type 1 diabetes mellitus through brainstem auditory evoked potentials and contralateral acoustic reflex

PURPOSE

To investigate the functionalities of the neural pathways through the auditory evoked potentials of the brainstem and the contralateral stapedial acoustic reflexes in normal-hearing individuals with type 1 diabetes mellitus, in order to detect possible alterations in the central auditory pathways.

METHODS

This is a cross-sectional study with a comparison group and a convenience sample, consisting of 32 individuals with type 1 diabetes mellitus and 20 controls without the disease. All subjects had hearing thresholds within normal limits and type A tympanometric curves. The acoustic reflex arc and brainstem auditory potentials were investigated. Statistical analyses were performed using the SPSS 17.0. The Chi-square test, Student´s t-test, and Multiple linear regression were used.

RESULTS

The auditory thresholds of the acoustic reflex were statistically lower in the group with the disease at frequencies of 0.5 kHz and 1.0 kHz in the left ear (p=0.01 and p=0.01, respectively). The absolute latencies III and V of the auditory potentials of the brainstem in the right ear and V in the left ear were increased in subjects with type 1 diabetes mellitus (p=0.03, p=0.02 and p=0.03, respectively).

CONCLUSION

The findings suggest that subjects with type 1 diabetes mellitus are more likely to present alterations in the central auditory pathways, even with auditory thresholds within normal limits.

Interpreting auditory brainstem evoked responses and distortion product otoacoustic emissions in diabetic patients with normal hearing

OBJECTIVE

Hearing impairment is a reported late complication of diabetes mellitus (DM). Previous studies have suggested that microangiopathic complications may cause cochlear nerve function deterioration. We evaluated the auditory brainstem evoked responses (ABRs) and distortion product otoacoustic emission (DPOAE) results according to the presence of DM in subjects with normal hearing.

METHODS

A cross-sectional comparative study was conducted from January 2016 to January 2018. Auditory function tests including ABR and DPOAE were performed for outpatients complaining of unilateral tinnitus. All of analyses were conducted in ears without tinnitus on contralateral side of tinnitus ears. We included subjects showing hearing thresholds within 25 dB at 0.5, 1k, 2k, and 4k on pure tone audiometry. 45 ears in patients with type 2 diabetes mellitus and 85 ears in non-diabetic patients were finally enrolled in our study.

RESULTS

Diabetic subjects showed significantly more prolonged absolute peak latencies (I, III, V) and inter-peak latencies (I-V, III-V) than non-diabetic subjects. However, there was no significant difference in the inter-peak latency (I-III) between these two groups. Diabetic subjects also showed significantly lower amplitudes at f2 frequencies of 1001, 1200, 1587, 4004, 5042, and 6348 Hz than non-diabetic subjects. Additionally, the prevalence of a DPOAE response, defined as 3 dB above the noise floor, was significantly lower in diabetic subjects than that in non-diabetic subjects.

CONCLUSION

Diabetic patients with normal hearing can still have abnormal ABR and DPOAE results due to diabetic neuroangiopathy. ABR and DPOAE assessments can help in detecting subclinical auditory dysfunction, which precedes the manifestation of hearing impairment in diabetic patients.

Early detection of hearing impairment in patients with diabetes mellitus with otoacoustic emission. A systematic review and meta-analysis

CONCLUSIONS

The distortion product otoacoustic emission (DPOAE) amplitudes in diabetics were significantly lower than those in controls when pure tone audiometry (PTA) was within normal limits, implying cochlear function impairment in the early stage of diabetes mellitus. Retrocochlear damage was suggested by elongated wave latencies and the wave interval of auditory brainstem response (ABR) in diabetics.

OBJECTIVES

This study aimed to systematically analyze the application of DPOAE in evaluation of the hearing function of diabetics.

DATA SOURCES AND REVIEW METHODS

Eligible articles were identified through searches of nine different electronic databases. Two investigators reviewed the original articles independently, with pre-defined inclusion and exclusion criteria. Meta-analyses were conducted by using Metan module.

RESULTS

There were seven articles eligible for the analysis. PTA thresholds were within normal limits in all diabetics at low-middle frequencies. The mean DPOAE amplitudes of diabetics were significantly lower than those of controls. The standardized mean difference (SMD) (95% CI) was -0.49 (-0.70, -0.27), -0.46 (-0.63, -0.30), and -0.60 (-0.77, -0.43) at 1, 2, and 4 kHz, respectively. The latencies of waves I, III, and V in diabetes were significantly longer than those of controls (0.43 (0.23, 0.64), 0.54 (0.33, 0.75), and 0.56 (0.35, 0.77), respectively). The wave interval I-V was significantly longer in diabetics (p < .001, 0.47 [0.24, 0.70]).

Role of oxidative stress in hearing impairment in patients with type two diabetes mellitus

OBJECTIVE

Although many clinical investigations have found a relationship between hearing loss and diabetes mellitus, the pathophysiology of this effect remains controversial. To date, the mechanisms of hearing loss in diabetic patients have been explained in terms of microangiopathy, neuropathy and encephalopathy. However, many reports indicate that some diabetic complications are associated with oxidative stress related to the diabetes itself. In the present study, we hypothesised that oxidative stress may be a cause of hearing loss in diabetic patients.

METHODS

The study group comprised non-insulin dependent diabetic patients with no signs of microangiopathy or peripheral neuropathy. The control group comprised sex-, age- and body weight matched, non-diabetic subjects. Auditory function was evaluated using pure tone audiometry and tympanometry. Subjects with normal hearing and sensorineural hearing loss were included in the study, whereas subjects with conductive hearing loss were excluded. Both the study group (n = 63) and the control group (n = 37) were divided into subgroups based on the presence and absence of hearing loss. Oxidative stress was evaluated by measuring serum indicators of protein oxidation and lipid peroxidation, serum levels of nitric oxide and various non-enzymatic antioxidants, and the activity of various enzymatic antioxidants.

RESULTS

The non-insulin dependent diabetic patients had significantly higher serum levels of protein oxidation products, nitric oxide, enzymatic antioxidant activity (i.e. glutathione peroxidase and superoxide dismutase), compared with the control group (p < 0.05). When we compared the groups in relation to the presence of hearing loss, the nitric oxide level was significantly increased in the diabetic group with good hearing, compared with diabetic patients with hearing loss (p = 0.014). In the diabetic group, a clear, negative correlation was observed between serum levels of nitric oxide and vitamins C and E, and hearing impairment (r = -0.395, r = -0.318, r = -0.500, respectively). There was also a positive correlation between serum vitamin C concentrations and hearing levels in the control group (r = 0.417).

CONCLUSION

These results suggest that oxidative stress may play an important role in hearing impairment in diabetic patients. In this process, increased protein oxidation appears to be more important than lipid peroxidation. Nitric oxide may have a protective effect on hearing, as may some nonenzymatic antioxidants such as vitamin C and E.