Auditory Processing in Patients with Structural Lesions of the Brain

This thesis investigated structure versus function in the central auditory nervous system (CANS) by using the lesion study approach and by utilising a validated clinical test battery for the assessment of auditory processing as well as selfor parent report measures. The central auditory test results were correlated with the macroscopical appearance o f the CANS on brain MRJ and with patient reported hearing difficulties. The two regions of interest for this study were the insula (first group of studies) and the interhemispheric pathway, comprised by the corpus callosum and the anterior commissure (second group of studies). First group of studies: Patients with a history of ischemic or haemorrhagic cerebral stroke of the CANS were identified by their scans. Exclusion criteria were significant psychiatric or expressive language disorders. Second group of studies: Adults and children with congenital aniridia and abnormality of the interhemispheric pathway due to a PAX6 mutation were recruited. The assessment included questionnaire of auditory capabilities, baseline audiometry (pure tone audiometry, tympanometry and otoacoustic emissions) and central auditory tests (speech and non-speech). The brain MRIs of these patients were visually inspected (1st and 2nd group of studies). The corpus callosum area was measured in the children participants of the 2nd group of studies. Main findings The insula is an integral part of the central auditory nervous system which may be necessary for auditory temporal resolution and sequencing. Patients with a unilateral focal ischemic lesion of the CANS have greater difficulties with sound detection & distinction, speech intelligibility in noise & in quiet, and sound localization than normal controls. Congenital structural and/or functional abnormalities of the anterior