Abstract
Background
We sometimes experience patients with persistent torsional/vertical (upbeating) positional nystagmus in the head-hanging position. We have been convinced of the existence of cupulolithiasis of the posterior semicircular canal because such cases reveal persistent torsional/vertical (downbeating) positional nystagmus in the nose-down position.
Purpose
In order to confirm the validity of Ewald’s third law, we quantified the difference between positional nystagmus in the head-hanging position and that in the nose-down position.
Methods
The subjects were 10 patients with posterior cupulolithiasis, 9 female and 1 male, with a mean age of 58.9 years. Nystagmus was recorded using an infrared camera and the findings were converted to digital data. Using ImageJ, we performed three-dimensional video-oculography and measured the maximum slow-phase velocity (MSV) of three components.
Results
In the horizontal component, the mean value of MSV in the head-hanging position was 3°/s, and that in the nose-down position was 2.7°/s. There was no significant difference between the two positions. In the vertical component, the mean value of MSV in the head-hanging position was 4.3°/s, and that in the nose-down position was 6°/s. There was no significant difference between the two positions. In the torsional component, the mean value of MSV in the head-hanging position was 4.4°/s, and that in the nose-down position was 1.4°/s. The former was significantly greater than the latter ( p < 0.01).
Conclusions
Although we could not confirm the validity of Ewald’s third law, the torsional component in the head-hanging position was significantly greater than that in the nose-down position.
1
Introduction
Peripheral positional vertigo is classified as posterior semicircular canal type and horizontal semicircular canal type. Positional nystagmus of the horizontal canal type is classified as direction-changing apogeotropic nystagmus (the horizontal component is toward the ceiling) and direction-changing geotropic nystagmus (the horizontal component is toward the Earth). Apogeotropic nystagmus is always persistent (duration of more than 1 min), but there are two types of geotropic nystagmus. One is a transient type and the other is a persistent type. Canalolithiasis (moving debris) accounts for the transient type and persistent geotropic nystagmus, which lasts for more than 1 min, is thought to be due to a light cupula of the horizontal canal .
In the posterior canal type, the canalith repositioning procedure and operative findings proved the theory of canalolithiasis. Many clinicians reported the efficacy of the canalith repositioning procedure , and we have also put this treatment into practice since 20 years ago. However, the success rate of this treatment is not always 100%. We sometimes experience patients in which it has no effect. Positional nystagmus of such cases lasts for more than 1 min. We have considered that the pathophysiology of patients with persistent torsional positional nystagmus is cupulolithiasis of the posterior canal , and have observed the eye movements in the nose-down position. All patients showed downbeating vertical/torsional nystagmus. Furthermore, we noticed that persistent upbeating vertical/torsional nystagmus occurred in the supine position.
According to Ewald’s third law, ampullofugal (away from the ampulla) deflection of the posterior semicircular canal cupula is stimulatory and ampullopetal (toward the ampulla) deflection is inhibitory. Morphological features of hair cells explain the validity of Ewald’s third law; however, it remained unclear how much of a difference there was between excitatory nystagmus and inhibitory nystagmus. In order to quantify the difference between positional nystagmus in the head-hanging position and that in the nose-down position, we analyzed nystagmus of posterior cupulolithiasis patients using three-dimensional video-oculography. The accuracy of video-oculography is equivalent to that of a scleral search coil system .
2
Materials and methods
2.1
Subjects
The subjects were 10 patients with posterior cupulolithiasis, who were diagnosed at our institution from September 2010 to December 2012 with a chief complaint of positional vertigo, and who fulfilled the following conditions.
- 1)
The Dix–Hallpike test reveals torsional/vertical (upbeating) nystagmus, and it lasts for more than 1 min in the head-hanging position.
- 2)
In the sitting position, no nystagmus or mild vertical (downbeating) nystagmus occurs.
- 3)
In the nose-down position, torsional/vertical (downbeating) nystagmus occurs and lasts for more than 1 min.
- 4)
In the supine position, torsional/vertical (upbeating) nystagmus occurs and lasts for more than 1 min.
- 5)
The prognosis is good. In most cases, vertigo and positional nystagmus disappear within 1 month. Severe cases get cured in a total period of 2 months maximum.
- 6)
No cochlear symptoms related to vertigo, and no central nervous system disorder.
2.2
Nystagmus testing and analysis
Nystagmus testing was performed in the dark with the patients’ eyes open using an infrared charge-coupled device camera. Eye movements were recorded and converted to digital data. Using ImageJ 1.36 and a Macintosh computer (Mac OS 10.6.2), three-dimensional video-oculography was performed. For analysis of horizontal and vertical components, the XY center of the pupil was calculated. For analysis of the torsional component, the whole iris pattern, which was rotated in steps of 0.1°, was overlaid with the same area of the next iris pattern, and the angle at which both iris patterns showed the greatest match was calculated . Maximum slow-phase velocity (MSV) of three components was measured manually. We compared the MSV of positional nystagmus in the head-hanging position with that in the nose-down position. Statistical analysis was performed by paired t test.
2.3
Determining the affected side
The affected side is the direction of the torsional component in the head-hanging position. If the superior pole of the eyeball moves toward the right ear of the patient in a quick-phase, the affected side is the right.
2
Materials and methods
2.1
Subjects
The subjects were 10 patients with posterior cupulolithiasis, who were diagnosed at our institution from September 2010 to December 2012 with a chief complaint of positional vertigo, and who fulfilled the following conditions.
- 1)
The Dix–Hallpike test reveals torsional/vertical (upbeating) nystagmus, and it lasts for more than 1 min in the head-hanging position.
- 2)
In the sitting position, no nystagmus or mild vertical (downbeating) nystagmus occurs.
- 3)
In the nose-down position, torsional/vertical (downbeating) nystagmus occurs and lasts for more than 1 min.
- 4)
In the supine position, torsional/vertical (upbeating) nystagmus occurs and lasts for more than 1 min.
- 5)
The prognosis is good. In most cases, vertigo and positional nystagmus disappear within 1 month. Severe cases get cured in a total period of 2 months maximum.
- 6)
No cochlear symptoms related to vertigo, and no central nervous system disorder.
2.2
Nystagmus testing and analysis
Nystagmus testing was performed in the dark with the patients’ eyes open using an infrared charge-coupled device camera. Eye movements were recorded and converted to digital data. Using ImageJ 1.36 and a Macintosh computer (Mac OS 10.6.2), three-dimensional video-oculography was performed. For analysis of horizontal and vertical components, the XY center of the pupil was calculated. For analysis of the torsional component, the whole iris pattern, which was rotated in steps of 0.1°, was overlaid with the same area of the next iris pattern, and the angle at which both iris patterns showed the greatest match was calculated . Maximum slow-phase velocity (MSV) of three components was measured manually. We compared the MSV of positional nystagmus in the head-hanging position with that in the nose-down position. Statistical analysis was performed by paired t test.
2.3
Determining the affected side
The affected side is the direction of the torsional component in the head-hanging position. If the superior pole of the eyeball moves toward the right ear of the patient in a quick-phase, the affected side is the right.
3
Results
Data on the 10 patients are shown in Table 1 . Video-oculography results and movie for patient no. 3 are shown in Fig. 1 and Supplemental data .
| Patient | Age (years) | Sex | Affected side | Head-hanging | Nose-down | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| MSV (°/s) | MSV (°/s) | ||||||||||
| H | V | T | Sum | H | V | T | Sum | ||||
| 1 | 38 | F | R | 2 (I) | 2 | 4 | 8 | 3 (I) | 4 | 0 | 7 |
| 2 | 42 | F | R | 0 | 3 | 3 | 6 | 4 (I) | 6 | 1 | 11 |
| 3 | 47 | M | L | 7 (I) | 14 | 6 | 27 | 0 | 5 | 2 | 7 |
| 4 | 60 | F | L | 7 (A) | 4 | 4 | 15 | 6 (I) | 4 | 0 | 10 |
| 5 | 62 | F | R | 4 (A) | 6 | 4 | 14 | 4 (A) | 6 | 0 | 10 |
| 6 | 63 | F | L | 0 | 5 | 4 | 9 | 4 (A) | 5 | 0 | 9 |
| 7 | 63 | F | R | 10 (I) | 0 | 6 | 16 | 0 | 14 | 5 | 19 |
| 8 | 68 | F | L | 0 | 0 | 5 | 5 | 0 | 6 | 4 | 10 |
| 9 | 72 | F | R | 0 | 5 | 6 | 11 | 3 (I) | 5 | 2 | 10 |
| 10 | 74 | F | L | 0 | 4 | 2 | 6 | 3 (I) | 5 | 0 | 8 |
| Mean | 58.9 | 3 | 4.3 | 4.4 | 11.7 | 2.7 | 6 | 1.4 | 10.1 | ||
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
