Special Kinds of Disorders of Hearing Development

An overview presenting the types and courses of hearing loss is followed by descriptions of special kinds of hearing impairment. Mechanisms and aetiologies are outlined in this chapter. The three primary types of peripheral hearing loss are conductive, sensorineural and mixed hearing loss. The remaining cases of hearing losses are central in origin. Hearing loss in children can be present at birth (congenital) or acquired later. In some cases the hearing loss is progressive or fluctuating. Developmental auditory processing disorder (APD) is a listening difficulty encountered despite normal auditory sensitivity, diagnosed primarily in children. APD has traditionally been defined as a disorder of the central auditory nervous system (CANS), but it may also involve cochlear hair cell or auditory nerve pathology. Cerebral cortical areas beyond the CANS and descending auditory pathways may also be involved. Hyperacusis is characterised by a reduced tolerance to sound. This kind of hypersensitivity has to be distinguished from phonophobia, misophonia and loudness recruitment. Tinnitus is the perception of sound in the absence of an external acoustic stimulus. It is a symptom that can arise as a result of dysfunction at any point in the auditory pathway. Non-organic (functional) hearing loss in children is characterised by hearing loss without a detectable corresponding pathology in the auditory system. Patient history shows a high prevalence of emotional and school problems. Pre-existing organic hearing loss can be worsened by non-organic causes.