Effects of recurrent acute otitis media on cortical speech-sound processing in 2-year old children

To investigate at the age of 2 years the effects of childhood recurrent acute otitis media (RAOM) on central auditory processing by using cortical event-related potentials elicited by syllable stimuli.

During a 1-year period, 22- to 26-month-old children fulfilling the criteria for tympanostomy tube insertion in Oulu University Hospital, Oulu, Finland, were recruited to the RAOM group (N = 20). The control group (N = 19) was matched by age, sex, and mother's educational level. In both groups, children were typically developing and had no family history of language disorder or developmental language problems. Finnish syllables /ke:/ and /pi:/ as standards and their variants with changes in frequency, intensity, vowel, consonant, and vowel duration as deviants were used to record P1, N2, and mismatch negativity (MMN) responses in the multifeature paradigm. The clinically healthy ears at the time of registration were a prerequisite for the participation.

Children with RAOM and their controls showed the age-typical P1 and N2 responses with no differences in the amplitudes or latencies between the groups, which suggests unaffected basic encoding of sound features and sound representation formation. However, the groups showed different auditory discrimination profiles. In children with RAOM, frequency and vowel MMN amplitudes were increased. Furthermore, the MMN latency for the frequency change was shorter and the frequency MMN amplitude lateralized to the left hemisphere in the RAOM group instead of an adult-like right-hemispheric lateralization observed in the controls. The children with RAOM had a more anterior MMN amplitude scalp distribution for the intensity change than control children. In addition, the MMN amplitude elicited by consonant change was evenly distributed unlike in controls, who had a left-side preponderant lateralization. Taken together, these results suggest an elevated responsiveness for frequency, vowel, and intensity changes, and an immature pattern of discriminating small speech sound contrasts in children with RAOM.

The results suggest that childhood RAOM does not affect the central auditory pathway integrity or sound encoding. However, RAOM may lead to aberrant preattentive discrimination of sound features even when the peripheral auditory input is normal. These results are clinically significant because even transient problems with auditory processing may delay language development.