Mitsuo Matsuzaki

Stage-Assessment of the Progress of Continuous Vertigo of Peripheral Origin by Means of Spontaneous and Head-shaking Nystagmus Findings

The stages of continuous vertigo of peripheral origin were classified into nine categories according to the findings of spontaneous nystagmus (SPN) and head-shaking nystagmus (HSN). The patients analysed were 18 with vestibular neuronitis, 6 with sudden deafness and 6 with unilateral inner ear disorders. 1) Irritative SPN (Stage I) was rarely encountered. 2) SPN of the paralytic type (Stage II) was usually observed in the period less than one month after the onset of diseases. 3) HSN directed toward the intact side with or without a reversal phase (Stages III-2 and III-1, respectively) were the common types of central compensation. 4) The progress of recovery to complete cure (Stage V) was usually rapid once it had actually begun. 5) During the process of recovery, HSN could disappear transitorily (Stage III-3), or be directed toward the affected side without a reversal phase (Stage III-5). Spontaneous recovery nystagmus (Stage IV) could also occur. 6) About 40% of patients recovered to Stage V within about 4 months after the onset of vertigo, but about 30% of patients remained in Stage III-1 or III-2 even after 4 months.

A Quantitative Analysis of Head-shaking Nystagmus of Peripheral Vestibular Origin

A quantitative analysis of horizontal head-shaking nystagmus (HSN) was made on 48 patients with unilateral peripheral vestibular lesions in conjunction with stimulus intensity. Each patient underwent three head-shaking tests with 10, 30 and 50 horizontal head-excursions at a frequency of approximately 2 Hz, and HSN was recorded on ENG with eyes open in total darkness. i) HSN appeared in a biphasic or monophasic pattern. ii) The maximal slow-phase eye velocity (MSV) of the 1st phase (PI) of biphasic HSN increased significantly in proportion to stimulus intensity, and was significantly greater than that of monophasic HSN. iii) The duration of HSN was greater in the 2nd phase (PII) of biphasic HSN than in PI and increased markedly in proportion to stimulus intensity. iv) As the stimulus intensity rose to a high level, the interval between PI and PII (2nd phase latency) shortened, and the PII tended to appear more quickly after head-shaking. It was especially noteworthy that in response to an increase in stimulus intensity, both the MSV in PI and the duration of PII of biphasic HSN increased, but the duration of PI was reversely suppressed by the PII.

Influence of lateral head tilting on head-shaking nystagmus

We conducted a trial to determine whether or not head-shaking nystagmus (HSN) was influenced by lateral head tilting. Twenty-two patients with unilateral peripheral vestibular lesions were examined between July 1990 and June 1996. All of the patients were found to have horizontal HSN following horizontal head shaking in the upright head position. Eye movements were recorded by electronystagmography with the eyes open in complete darkness. Patients voluntarily tilted their heads to the lateral head positions with the assistance of the examiner as quickly as possible immediately after head shaking in the upright head position. Findings showed that monophasic horizontal HSN and the first phase of biphasic horizontal HSN were suppressed by lateral head tilting. The second phase of biphasic horizontal HSN was influenced differently by head tilting when compared with the first phase. Vertical (down-beating) components in horizontal HSN may appear in the peripheral vestibular lesions, but seem to have no definite relation to head positions.