Insights into elevated distortion product otoacoustic emissions in sickle cell disease: Comparisons of hydroxyurea-treated and non-treated young children

Dysfunction of the auditory system in sickle cell anaemia: a systematic review with meta-analysis

OBJECTIVES

To describe the occurrence of both peripheral and central auditory system dysfunction in sickle cell anaemia (SCA) patients and discuss the different mechanisms hypothesised to be responsible for these alterations.

METHODS

An electronic search was conducted using PubMed Central^® (MEDLINE), LILACS^® and Scopus^® databases. This systematic review was performed in accordance with the PRISMA statement. Original observational studies that utilised audiological tests for auditory system evaluations in SCA were included.

RESULTS

A total of 183 records were found in the databases searched. Twenty-one of these studies met the inclusion criteria. Pooled prevalence of sensorineural hearing loss (SNHL) was 20.5% (CI: 10.3-33%). Retrocochlear involvement was detected with the auditory brainstem response, which assesses integrity of the cochlea, 8th cranial nerve and brainstem structures. In addition, the increase in otoacoustic emission amplitudes in SCA patients indicates changes in cochlear micromechanics and precedes the expression of a detectable cochlear pathology.

CONCLUSION

The prevalence of the SNHL is higher than in the general population. Dysfunction of the auditory system may be present in SCA patients, with the most probable mechanism being the presence of circulatory disturbances resulting from the chronic inflammatory state of the disease.

The emergence and prevalence of hearing loss in children with homozygous sickle cell disease

OBJECTIVES

Many children with sickle cell disease (SCD) experience the effect of cochlear insult due to hemolytic anemia and vaso-occlusion that accompanies the disease. As a result, hearing sensitivity eventually decreases. The purpose of this study was to investigate the emergence of hearing loss and the prevalence of such in children with homozygous SCD.

METHODS

A large pediatric database was utilized to gather audiometric outcomes in children with homozygous SCD. Children were identified by primary diagnosis ICD codes. Demographic and audiometric data was drawn to determine presence, type, degree, and laterality of hearing loss. Hearing loss was defined as an elevated audiometric threshold >15 dB HL for pure tone air conduction audiometry or >20 dB HL minimal response level for sound-field testing.

RESULTS

One hundred and twenty-eight children were identified. The prevalence of hearing loss ranged from 28.8% to 50.8% depending on the calculation method (i.e., individual vs. ear specific prevalence and any elevated threshold vs. a three-frequency pure tone average). Conductive hearing loss and bilateral loss were most prevalent. The degree of hearing loss ranged from slight to profound. The mean age of identification of sensorineural hearing loss was 9.6 years.

CONCLUSION

The prevalence of hearing loss in children with homozygous SCD is higher than in normal children. Regular hearing assessments of children with SCD is warranted and should be advocated in early infancy and as part of their ongoing care.

Hidden hearing loss in children and adolescents with sickle cell anemia

OBJECTIVE

To evaluate the auditory system for hidden hearing loss (HHL) and its association with clinical variables and endothelial dysfunction (ED) in children and adolescents with sickle cell anemia (SCA).

METHODS

Participants included 37 patients with stable SCA and 44 healthy controls (HC group) (aged 6-18 years) with hearing thresholds ≤ 20 dB (dB) were evaluated for pure tone audiometry, tympanometry, acoustic reflex, otoacoustic emission, and auditory evoked potentials. Laboratory analysis of the lipid profile, and C-reactive protein levels and endothelial function using ultrasonographic imaging of the brachial artery to assess flow-mediated dilation were performed.

RESULTS

The SCA group presented with a higher rate of increased contralateral acoustic reflex thresholds, compared to those in the HC group at all frequencies and in both ears (p < 0.05). There were significant differences in the brainstem auditory evoked potentials between the SCA and HC groups. In the SCA group, the waves III and V latencies were increased (p = 0.006 and 0.004 respectively), and the I-III and I-V interpeak intervals were longer (p = 0.015 and 0.018 respectively) than those in the HC group. There was no association between the audiological measures and clinical and metabolic variables and sickle cell anemia complications including endothelial function and therapy.

CONCLUSION

In conclusion, our findings suggest that damage in the auditory system in SCA patients can be present involving retrocochlear structures, causing functional deficits without deterioration of auditory sensitivity.