Temporal auditory and visual motion processing of children diagnosed with auditory processing disorder and dyslexia.

OBJECTIVE: Auditory processing disorder (APD) is diagnosed on the basis of listening difficulties despite normal audiogram, although the cause is unknown. This study examined the hypothesis that the underlying cause of APD is a modality-specific deficit in auditory temporal processing and also considered how far the auditory impairments in APD differ from those in children with dyslexia. DESIGN: Performance of children diagnosed with APD (N = 22) was compared with that of a normative group (N = 98) as well as with children with dyslexia (N = 19) on a battery of temporal auditory tasks; 2-Hz frequency modulation (FM), 40-Hz FM, and iterated rippled noise detection as well as a control task (240-Hz FM), which is thought to draw on peripheral spectral mechanisms. Visual tasks were coherent form and coherent motion detection. RESULTS: On average, the APD group performed more poorly than the normative group on the 40-Hz FM, 240-Hz FM, and iterated rippled noise tasks. There were no significant differences between the APD and dyslexia group's performance and no evidence for a specific temporal auditory impairment. A higher proportion of children in the APD group performed poorly (<-1 SD) on the visual tasks than those in the normative group. Auditory psychophysical performance correlated positively with the performance on the SCAN-C, a standardized test of auditory processing, but not with reading ability. CONCLUSIONS: The research did not support a modality-specific impairment of temporal auditory processing as being the underlying cause of APD. In both the APD and dyslexia groups, a similar proportion displayed poor auditory performance, and this does not seem entirely accounted for by attention or performance I.Q. However, the significance of these auditory difficulties is uncertain. Serious difficulties with auditory assessment were also identified. Currently, auditory perceptual deficits may be better seen as a part of a multifactorial description of learning problems rather than as part of a diagnostic category in their own right.

The derivation of optimum criteria for use in the monothermal caloric screening test.

OBJECTIVE: The aim of this study was to determine whether it is possible to predict a normal outcome of the bithermal caloric test by testing at a single temperature and if so, what criteria are most appropriate to use. DESIGN: A total of 490 patients were considered candidates for the bithermal test and 414 completed the four necessary components, their nystagmus being measured using videonystagmography. RESULTS: Clinical decision analysis revealed that the cool monothermal test does not provide an adequate combination of sensitivity and specificity for us to recommend its clinical use. However, the warm monothermal test offers a sensitivity of 95% with 29% of patients with normal bithermal results having to undergo the bithermal test (specificity = 71%) if a combination of three criteria are used: a normal bithermal caloric test outcome can be anticipated and testing curtailed after the first temperature if (a) the warm monothermal caloric asymmetry (MCA) is <15% and (b) the two warm results are each >8 degrees per sec ( degrees /sec), and (c) any spontaneous nystagmus is <4 degrees /sec. CONCLUSIONS: When appropriate criteria are used, the warm monothermal caloric test offers a performance that is acceptable for routine clinical use, sparing a considerable proportion of patients from unnecessary tests at the cool temperature. We believe that the warm/cool monothermal test difference is probably a consequence of the interrelationship between canal paresis and directional preponderance.