Intrauterine exposure to Zika virus and hearing loss within the first few years of life: A systematic literature review

Background: Identification of the factors that could potentially lead to congenital hearing loss is of paramount importance, as early detection of congenital hearing loss and intervention could prevent developmental delays in speech, language development as well as childhood cognitive impairment. Hitherto, intrauterine exposure to Zika virus has emerged as a cause of various fetal malformations, including cases of congenital hearing loss. The aim of this systematic review is to investigate the association between intrauterine exposure to Zika virus and hearing loss in children. Methods: A systematic literature search was conducted to the databases PubMed, Cochrane library, Scopus, ClinicalTrials.gov, SciELO and Lilacs in order to identify studies that examine the association between prenatally Zika exposure and hearing loss within the first few years of life. Studies were eligible for inclusion, if solely objective methods for hearing evaluation of patients such as otoacoustic emissions (OAEs) and/or auditory brainstem response (ABR) were used, in children who intrauterine exposed to the Zika virus. Results: Thirteen studies were included, which included 1275 children who are prenatally exposed to Zika virus. In 852 of the cases an objective hearing evaluation was performed using either OAEs or ABR. 709 children were tested with ABR and 79 had a failed outcome. 143 children were tested with OAEs whilst of these, 30 had a failed outcome. Altered OAEs ranged from 8.7% to 30.2%, while altered ABR ranged from 0% to 19.9%. The initial sample includes 428 children with microcephaly, while 5 of the studies comprise microcephaly to the inclusion criteria. Conclusion: It seems to be a possible association between prenatal Zika virus exposure and hearing loss in children during the first years of their life. It is of great importance that in future studies possible confounding factors, like microcephaly, will be appropriately controlled. Additionally, the follow-up period of monitoring hearing loss in children should be prolonged in order to identify potential late onset hearing problems caused by intrauterine exposure to Zika virus.