Abstract
Early treatment of single sided deafness in children has been recommended to protect from neurodevelopmental preference for the better hearing ear and from social and educational deficits. A fairly homogeneous group of five young children (≤3.6 years of age) with normal right sided hearing who received a cochlear implant to treat deafness in their left ears were studied. Etiology of deafness was largely cytomegalovirus (n = 4); one child had an enlarged vestibular aqueduct. Multi-channel electroencephalography of cortical evoked activity was measured repeatedly over time at: 1) acute (0.5 ± 0.7 weeks); 2) early chronic (1.1 ± 0.2 months); and 3) chronic (5.8 ± 3.4 months) cochlear implant stimulation. Results indicated consistent responses from the normal right ear with marked changes in activity from the implanted left ear. Atypical distribution of peak amplitude activity from the implanted ear at acute stimulation marked abnormal lateralization of activity to the ipsilateral left auditory cortex and recruitment of extra-temporal areas including left frontal cortex. These abnormalities resolved with chronic implant use and contralateral aural preference emerged in both auditory cortices. These findings indicate that early implantation in young children with single sided deafness can rapidly restore bilateral auditory input to the cortex needed to improve binaural hearing.
Highlights
There are significant consequences of single sided deafness (SSD) in childhood on auditory development and function[1,2,3] but questions about treatment remain[4]
cochlear implant (CI) use in the 4 children with complete data did not vary with CI experience (χ2(1) = 0.3, p = 0.61)
Cortical recovery from SSD occurred rapidly in a small but relatively homogenous group of young children (≤ 3.6 years old) who consistently wore their CI for several hours daily
Summary
There are significant consequences of single sided deafness (SSD) in childhood on auditory development and function[1,2,3] but questions about treatment remain[4]. Similar findings are reported from kittens born with unilateral deafness[17,18] or experimentally induced unilateral/asymmetric hearing in young animals[19,20,21] Such auditory asymmetries have consequences for processing binaural timing and level cues[19,22] which are integral for locating and distinguishing one sound amongst many[23]. To avoid problems of single sided listening and preserve opportunities for binaural hearing, it has been recommended that hearing loss (unilateral or bilateral) be treated by providing the most appropriate device in each ear as soon as possible[3]. Plasticity of the neural input to auditory cortices was measured to assess whether expected representation can be restored by providing electrical stimulation from a CI in one ear with normal hearing in the other ear in early development. Results in a group of young children (≤3.6 years) who were deaf in their left ears from infancy demonstrate marked and rapid uptake of input from the newly implanted ear, restoring symmetric representation of both ears in the auditory brain
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