Children with evidence of congenital Zika virus infection should undergo regular auditory testing and follow-up evaluations, regardless of the presence of microcephaly, according to research published in the CDC’s Morbidity and Mortality Weekly Report.
“Hearing loss is a well established feature of other congenital infections, including cytomegalovirus (CMV), rubella, toxoplasmosis, herpes simplex, and syphilis,” said Mariana C. Leal, PhD, of Hospital Agamenon Magalhães, Federal University of Pernambuco, Recife, Brazil. “In these syndromes, the hearing loss is sensorineural, usually bilateral, and severe or profound; it is often undetectable at birth, and sometimes it is progressive or fluctuating.”
Dr Leal and colleagues conducted a retrospective assessment of 70 infants between 0 and 10 months old who had both microcephaly and laboratory confirmation of Zika virus infection; all infants were enrolled between November 2015 and May 2016. Auditory screening and diagnostic hearing tests were conducted on all infants; if the initial screening was considered abnormal, researchers repeated the test approximately 1 month later. A hearing loss diagnosis was confirmed if the infants’ hearing thresholds exceeded 25 dB nHL.
Among all 70 infants tested, 16 (22.8%) failed their first screening test in at least one ear; 8 of these infants failed the repeat test and were evaluated using frequency-specific auditory brainstem response (ABR). ABR assessment confirmed hearing impairment in 7 (10%) infants, including 2 infants with conductive hearing loss and 5 with sensorineural hearing loss.
Dr Leal noted that behavioral auditory testing was not performed, and that all children considered “normal” after the auditory evaluation will be regularly reassessed for evidence of late-onset hearing impairment.
Information on the presence of rash during pregnancy was obtained from 63 mothers, 54 (86%) of whom confirmed the presence of a rash. Among these mothers, 41 (76%) experienced the rash during their first trimester. Timing of maternal rash during pregnancy did not differ between infants with and without sensorineural hearing loss (P =.64).
“Hearing loss varied in severity and laterality, which has been reported in hearing loss associated with other congenital infections,” concluded Dr Leal. “In the majority of [those] cases … the damage to the auditory system is within the cochlea. It is likely that similar lesions account for the hearing deficit in children with congenital Zika virus infection, although histologic studies are needed to confirm this.”
Leal MC, Muniz LF, Ferreira TSA, et al. Hearing Loss in Infants with Microcephaly and Evidence of Congenital Zika Virus Infection – Brazil, November 2015-May 2016. MMWR Morbid Mortal Wkly Rep. 2016 Aug 30; doi: 10.15585/mmwr.mm6534e3. [Epub ahead of print].