A long-term follow-up study on otoacoustic emissions testing in paediatric patients with severe malaria in Gabon

Abstract

Background: In a previous study, severe and cerebral malaria have been connected with acute cochlear malfunction in children, demonstrated by a decrease of transitory evoked otoacoustic emissions (TEOAEs) reproducibility. This study aims to determine whether cochlear malfunction persists for 4 years after recovery from severe malaria in a subset of the previous study's collective. Follow-up TEOAEs were performed on site (CERMEL, Hôpital Albert Schweitzer, Lambaréné, Gabon) or at the participants' homes; 33 out of 90 participants included in the initial investigation by Schmutzhard et al. could be retrieved and were re-examined, 31/33 could be included. Of the 57 missing participants, 51 could not be contacted, 1 had moved away, 4 refused to cooperate, and 1 had died.

Methods: As in the initial investigation, participants of this prospective follow-up study were subjected to TEOAE examination on both ears separately. A wave correlation rate of > 60% on both ears was considered a "pass"; if one ear failed to pass, the examination was considered a "fail". The results were compared to the primary control group. Additionally, a questionnaire has been applied focusing on subsequent malaria infections between the primary inclusion and follow-up and subjective impairment of hearing and/or understanding.

Results: The cohort's mean age was 9 years, 14 children were female, 18 male. 31 had been originally admitted with severe, one with cerebral malaria. 83.8% of participants (n = 26) presented with a TEOAE correlation rate of > 60% on both ears (the cut-off for good cochlear function); in the control group, 92.2% (n = 83) had passed TEOAE examination on both ears. Recurrent severe malaria was associated with a worse TEOAE correlation rate. Age at infection and gender had no influence on the outcome.

Conclusions: Cochlear malfunction seems to be persistent after 4 years in more than 16% of children hospitalized for malaria. In a healthy control group, this proportion was 7.8%. Yet, the severity of the initial TEOAE-decrease did not predict a worse outcome.

Keywords: Children; Hearing loss; Otoacoustic emissions; Severe malaria.

Fig. 1

Shows the percentage of participants who presented at follow-up with a TEOAE wave reproducibility rate of < 60% on at least one ear compared to a healthy control group. Statistical significance was assessed using Fisher’s exact test (p value = 0.159)

Fig. 2

Shows the overall pass rates in black and the overall fail rates in grey at timepoint 4 (14–28 days after admission) compared to the overall pass rates and fail rate at the followed-up measurement (p value from GEE model = 0.189 with sequential Sidak correction)

Fig. 3

a Visualizes a model prediction of the wave reproducibility rates of the patients who had recovered from cochlear damage secondary to acute P. falciparum malaria at follow-up versus those who had not. Between day 14 and 28 after admission and follow-up, wave reproducibility rates increased in the recovery group significantly. (p < 0.01, GEE model with sequential Sidak correction). This trajectory illustrates two findings: not all children recover, and recovery occurs between 1 month (timepoint 4) and 5 years (follow-up). b, c A longitudinal analysis of all measurements (timepoints 1–5) of the followed-up cohort, illustrating that most children recover from cochlear damage, but not all. A distinct dip in wave reproducibility either at 12–24 h after hospitalization or after recovery (7 days later) can be seen