Results of sinusoidal harmonic acceleration test in one thousand patients: preliminary report.

One thousand patients with dizziness were tested by sinusoidal harmonic acceleration with frequencies of .01, .02, .04, .08, and .16 Hz. Two hundred fifty (25% of data base) were randomly selected for this study. One hundred forty-eight diagnoses were confirmed: 66 (45%) patients had a clinical diagnosis of peripheral vestibular dysfunction, 28 (19%) had central vestibular dysfunction, and 53 (36%) had dizziness of undetermined cause. This preliminary study investigated the response patterns of phase (latency), asymmetry (slow phase preponderance), and gain (output/input) as they correlated with each of the above patient groups. The main response pattern was a varying degree of asymmetry with normal or abnormal latency. Persistent abnormal phase pattern indicated permanent vestibular damage and could not be used reliably to differentiate peripheral from central vestibular dysfunction. Asymmetry changed with time and correlated with patients' symptoms. The dynamic pattern of asymmetry could be used to differentiate peripheral from central vestibular dysfunction. Gain was a reliable and essential measure of the sensitivity of the vestibular system and the validity of the rotational response.