Clinical value of sinusoidal harmonic acceleration test results. Site of lesion and side of lesion

Abstract

Sinusoidal harmonic acceleration tests can be used reliably to determine site and side of lesion. Results from 6000 patients collected over the past 10 years have shown that the temporal pattern of asymmetry can be reliably used to differentiate peripheral from central vestibular dysfunction. Peripheral cases tend to have a high level of asymmetry, with temporal regression to normal range, and a high correlation with patient symptoms. Central cases tend to have a low level of variable asymmetry and variable symptoms. In either case, phase can be abnormal or normal and cannot be reliably used to differentiate peripheral from central dysfunction. By combining phase and symmetry, the side of the lesion can be reliably determined. When phase is abnormal, asymmetry is toward the side of the lesion in 92 per cent of cases, whereas when phase is normal, asymmetry cannot be reliably used to determine side of lesion. SHA testing has contributed significantly to our clinical ability to fully evaluate the vestibular system and has become an indispensable part of the complete vestibular laboratory. It requires a relatively large patient load as well as software and hardware support to become a cost-effective utility.