These "short circuits in the wiring" sometimes run in families or result from a difficult birth, just like any learning disability. Auditory processing disorder can be associated with conditions affected by genetic traits, such as various developmental disorders. Inheritance of auditory processing disorder refers to whether the condition is inherited from your parents or "runs" in families. Central auditory processing disorder may be hereditary neurological traits from the mother or the father. Developmental
In the majority of cases of developmental APD, the cause is unknown. An exception is acquired epileptic aphasia or Landau-Kleffner syndrome, where a childs development regresses, with language comprehension severely affected. The child is often thought to be deaf, but normal peripheral hearing is found. In other cases, suspected or known causes of APD in children include delay in myelin maturation, ectopic (misplaced) cells in the auditory cortical areas, or genetic predisposition. In a family with autosomal dominant epilepsy, seizures which affected the left temporal lobe seemed to cause problems with auditory processing. In another extended family with a high rate of APD, genetic analysis showed a haplotype in chromosome 12 that fully co-segregated with language impairment.Hearing begins in utero, but the central auditory system continues to develop for at least the first decade. There is considerable interest in the idea that disruption to hearing during a sensitive period may have long-term consequences for auditory development.
This can include problems with: "...sound localization and lateralization (see also binaural fusion); auditory discrimination; auditory pattern recognition; temporal aspects of audition, including temporal integration, temporal discrimination (e.g., temporal gap detection), temporal ordering, and temporal masking; auditory performance in competing acoustic signals (including dichotic listening); and auditory performance with degraded acoustic signals".The Committee of UK Medical Professionals Steering the UK Auditory Processing Disorder Research Program have developed the following working definition of auditory processing disorder: "APD results from impaired neural function and is characterized by poor recognition, discrimination, separation, grouping, localization, or ordering of speech sounds. It does not solely result from a deficit in general attention, language or other cognitive processes." Types of testing
The SCAN-C for children and SCAN-A for adolescents and adults are the most common tools for screening and diagnosing APD in the USA. Both tests are standardized on a large number of subjects and include validation data on subjects with auditory processing disorders. The SCAN test batteries include screening tests: norm-based criterion-referenced scores; diagnostic tests: scaled scores, percentile ranks and ear advantage scores for all tests except the Gap Detection test. The four tests include four subsets on which the subject scores are derived include: discrimination of monaurally presented single words against background noise (speech in noise), acoustically degraded single words (filtered words), dichotically presented single words and sentences. Random Gap Detection Test (RGDT) is also a standardized test. It assesses an individuals gap detection threshold of tones and white noise.