Direction Of Nystagmus Research Articles

Effect of semicircular canal stimulation on the perception of the visual vertical.

The subjective visual vertical (SVV) is usually considered a measure of otolith function. Herewith we investigate the influence of semicircular canal (SCC) stimulation on the SVV by rotating normal subjects in yaw about an earth-vertical axis, with velocity steps of +/- 90 degrees /s, for 60 s. SVV was assessed by setting an illuminated line to perceived earth vertical in darkness, during a per- and postrotary period. Four head positions were tested: upright, 30 degrees backward (chin up) or forward, and approximately 40 degrees forward from upright. During head upright/backward conditions, a significant SVV tilt (P < 0.01) in the direction opposite to rotation was found that reversed during postrotary responses. The rotationally induced SVV tilt had a time constant of decay of approximately 30 s. Rotation with the head 30 degrees forward did not affect SVV, whereas the 40 degrees forward tilt caused a direction reversal of SVV responses compared with head upright/backward. Spearman correlation values (Rho) between individual SCC efficiencies in different head positions and mean SVV tilts were 0.79 for posterior, 0.34 for anterior, and - 0.80 for horizontal SCCs. Three-dimensional video-oculography showed that SVV and torsional eye position measurements were highly correlated (0.83) and in the direction opposite to the slow phase torsional vestibuloocular reflex. 1) during yaw axis rotation without reorientation of the head with respect to gravity, the SVV is influenced by SCC stimulation; 2) this effect is mediated by the vertical SCCs, particularly the posterior SCCs; 3) rotationally induced SVV changes are due to torsional ocular tilt; 4) SVV and ocular tilts occur in the "anticompensatory," fast phase direction of the torsional nystagmus; and 5) clinically, abnormal SVV tilts cannot be considered a specific indication of otolith system dysfunction.

耳石性眼反応の特徴―ステップ状側方直線加速度負荷による解析―

Lateral linear acceleration induces otolithic nystagmus and the otolith-ocular reflex (OOR). These response properties have been studied mostly by dynamic analysis using sinusoidal translation, and only a few reports are available so far with static analysis using step-mode acceleration, due to technical limitations. According to our studies using a linear accelerator with a period up to several seconds of step-mode lateral oscillation (Mori and Katayama, 1998; Katayama and Mori 2001), the direction of nystagmus is dependent on G-direction and directional preponderance (DP) of nystagmus elicitation is physiological. The slow cumulative eye-position (SCEP) curve in which the fast components are eliminated is saw-toothed in shape when lateral oscillation continues in a step mode, implying that the eye position, instead of the eye velocity, is controlled by stimulus velocity signals. The SCEP often accompanies a slow drift during the oscillation, and the slow-drift slope is positively correlated with DP: the steeper the slope, the larger the DP. The OOR velocity measured from the SCEP slope is symmetrical between G-directions when the slow drift is cancelled algebraically. Such symmetry in OOR velocity is in agreement with the previous reports (Gianna et al., 1997; Lempert et al., 1998 1999) using a short and single step-mode acceleration, suggesting that the slow drift is a component hidden behind the ordinary ocular movement and adjusted by the fast phase of nystagmus.

良性発作性頭位めまい症の回旋性眼振の垂直成分

Benign paroxysmal positional vertigo (BPPV), one of the most common diseases of peripheral vestibular origin, is characterized by transient vertigo accompanied by benign paroxysmal positional nystagmus (BPPN) provoked by turning over in bed, lying down or sitting up. BPPN with a torsional component, short latency and a crescendo-decrescendo mode, is provoked by positional testing and disappears within 30 sec. The direction of the torsional nystagmus, provoked by lying down, reverses by sitting up. The nystagmus may decrease by repeated provocations as an adaptation. Canalolithiasis of the posterior canal is widely accepted as a cause of BPPV, because BPPN is well predicted and BPPV is successfully treated by Epley's canalith repositioning procedure on the basis of this hypothesis. Canalolithiasis of both the horizontal and anterior canals has also been reported as BPPV-variants. In this study, BPPN recorded by an infrared CCD camera and video recorder, and the incidence and meaning of the vertical component of BPPN were investigated in 110 cases of BPPV with torsional BPPN. Out of all 110 cases, up beating vertical component appeared in 39 (35.5%), down beating in 24 (21.8%) and no vertical component in 47 cases (42.7%), when torsional BPPN was provoked by lying down. Horizontal nystagmus of the direction changing type was also observed in 4 cases. According to the canalolithiasis hypothesis, upward and downward vertical components triggered by lying down should occur in the posterior and anterior canal types, respectively. Pure torsional positional nystagmus provoked by positioning was assumed to occur in the crus communis type, in which free-floating endolymph particles remain in the crus communis of the labyrinth.

The directions of nystagmus and apparent self-motion evoked by caloric tests and angular accelerations

To further investigate the direction of (I) nystagmus and (II) self-motion perception induced by two stimuli: (a) caloric vestibular stimulations and (b) a sudden halt during vertical axis rotation. Twelve normal humans received caloric stimulation at 44 degrees C, 30 degrees C, and 20 degrees C while in a supine position with the head inclined 30 degrees upwards. In a second test they were rotated around the vertical axis with the head randomly placed in two positions: tilted 30 degrees forward or tilted 60 degrees backward, at a constant velocity of 90 degrees /sec for 2 minutes and then suddenly stopped. After both tests they were asked to describe their sensations of self-motion. Eye movements were recorded with an infrared video-technique. Caloric stimulation evoked only horizontal nystagmus in all subjects and induced a non-uniform complex perception of angular in frontal and transverse planes (the former dominated) and linear movements along the antero-posterior axis (sinking dominated) of the subject's coordinates. The self-motion was felt with the whole body or with a part of the body. Generally the perception evoked by cold (30 degrees C) and warm (44 degrees C) calorics was similar, although there were some differences. The stronger stimulus (20 degrees C) evoked not only quantitative but also qualitative differences in perception. The abrupt halt of rotation induced self-motion perception and nystagmus only in the plane of rotation. The self-motion was felt with the whole body. There was no difference in the nystagmus evoked by caloric stimulation and a sudden halt of vertical axis rotation (in head positions to stimulate the horizontal canals); however, the two stimuli evoked different perceptions of self-motion. Calorics provoked the sensation of self-rotation in the frontal plane and linear motion, which did not correspond to the direction of nystagmus, as well as arcing and a reset phenomenon during angular and linear self-motion, caloric-induced self-motion can be felt predominantly or only with a part of the body, depending on the self-motion intensity. The findings indicate that, unlike the self-motion induced by sudden halt of vertical axis rotation, several mechanisms take part in generating caloric-induced self-motion.

Multivariate vestibular testing: Laterality of unilateral Ménière's disease

This paper discusses the use of vestibular testing to discriminate between right (n = 29) and left (n = 27) Ménière's disease. We examined reduced vestibular response (RVR), directional preponderance, and spontaneous and positional nystagmus measurements from electronystagmography, as well as the asymmetry measurements from the sinusoidal harmonic acceleration test, to determine whether multivariate logistic regression could improve upon the discrimination performance of RVR alone. We found that patients with a spontaneous or positional nystagmus often had a "recovery nystagmus", beating in the opposite direction of that predicted for an acute lesion. When present, the direction and magnitude of such nystagmus could be used in the classification algorithm to increase the discriminatory power over RVR alone, but in these patients the rotation test asymmetry measurements were rendered useless. In the absence of spontaneous or positional nystagmus, asymmetry measurements significantly enhanced right/left discrimination. Directional preponderance was insignificant in determining the side of lesion.

The contribution of midbrain circuits in the control of gaze.

The midbrain contains several structures important for the generation of torsional and vertical eye movements including the rostral interstitial nucleus of the MLF (riMLF) and the interstitial nucleus of Cajal (iC). While the riMLF is the immediate premotor structure for the generation of torsional and vertical saccades, the iC is considered a major part of the neural integrator for torsional and vertical eye movements. Experiments in monkeys show that a unilateral inactivation of the riMLF with muscimol leads to spontaneous contralesional torsional nystagmus, whereas an iC inactivation causes ipsilesional torsional nystagmus. In addition, inactivation of either structure leads to a tonic ocular torsion to the contralesional side. While the deficits after a riMLF lesion are thought to result from an imbalance of the saccade generator, a vestibular imbalance probably causes the deficits after an iC lesion. Contralesional and ipsilesional torsional nystagmus is also found in patients with unilateral mesencephalic lesions. A detailed analysis of the lesions from MRI scans shows a preferential involvement of the riMLF for patients with contralesional torsional nystagmus, and a major involvement of iC in cases with ipsilesional torsional nystagmus. Thus, the direction of torsional nystagmus appears to be a valuable topodiagnostic sign for patients with midbrain lesions.

頭位変換療法中に眼振の変化したＢＰＰＶ例 方向交代性上向性眼振例

Apogeotropic direction-changing positional nystagmus is considered to appear in patients with disorders of the central nervous system. However, this peculiar nystagmus is more likely to be caused by peripheral vestibular disorder. The mechanism of apogeotropic direction-changing positional nystagmus can be explained by benign paroxysmal positional vertigo (BPPV) caused by cupulolithiasis in the horizontal semicircular canal.We used the canalith repositioning procedure (CRP) in a patiant with apogeotropic direction-changing positional nystagmus diagnosed as BPPV, and observed the change from upper-beating nystagmus to down-beating nystagmus during the procedure. The change in the direction of nystagmus seemed to indicate the dispersion of otolithic debris from the cupula, that is to say, the conversion of cupulolithiasis to canalolithiasis. We observed the disappearance of nystagmus and vertigo after three days.

めまいを伴った突発性難聴患者の頭位眼振所見からみた前庭障害の予後

Ninety-seven patients with sudden deafness with positional nystagmus under Frenzel's glasses were analyzed. The patients were treated with steroids, low-molecular dextran and prostaglandin E1. The positional nystagmus disappeared in 59.8% within 28 days of the onset. 23.6% of the patients were observed to have positional nystagmus continuously until sixth months from onset. The factors of poor prognosis of positional nystagmus up to sixth months seemed to be canal paresis, age group and frequent change of direction of the positional nystagmus. There was no relationship between the period from the onset to the initiation of treatment and prognosis of the positional nystagmus.

Three-dimensional spatial characteristics of caloric nystagmus

We investigated the three-dimensional spatial characteristics of caloric nystagmus during excitation and inhibition of the lateral semicircular canal in five normal human subjects. Each subject was repositioned in 45 degrees steps at 1-min intervals such that the right lateral semicircular canal plane was reoriented in pitch, from 135 degrees backwards from the upright position to 135 degrees forwards, while the right ear was continuously stimulated with air at 44 degrees C. In orientations in which caloric stimulus resulted in excitation of the right lateral semicircular canal, the eye velocity axis was orthogonal to the average orientation of the right lateral semicircular canal plane. However, in orientations in which caloric stimulus resulted in inhibition of the right lateral semicircular canal, the eye velocity axis was orthogonal to the average orientation of the left and not the right lateral semicircular canal plane. These findings suggest that velocity and direction of caloric nystagmus depend not only on the absolute magnitude of vestibular activity on the stimulated side but also on the differences in activity between the left and right vestibular nuclei, most probably mediated centrally via brainstem commissural pathways.

Periodic alternating nystagmus and vestibulo-spinal system facilitating activity

Objective: Periodic alternating nystagmus has been associated with the instability of the velocity storage mechanism, which is known to play an important role in both the vestibulo-oculomotor and the optokinetic systems. In the present study we looked for a possible spinal equivalent to PAN.Methods and results: In 3 PAN patients, the H-reflex amplitude proved to be slightly but significantly influenced by nystagmus direction, in that it was greater when the nystagmus was beating toward the stimulation side.Conclusions: This finding suggests that projections from velocity storage may play a role not only in the ocular motor but also in assisting postural stability through the vestibulo-spinal system.

Eye movement deficits after unilateral mesencephalic lesions

The effect of unilateral mesencephalic lesions on eye movements in experimental and clinical studies is compared, with an emphasis on torsional eye movements. Two main structures in the mesencephalon are involved in the premotor processing of torsional and vertical eye movements: the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF) and the interstitial nucleus of Cajal (iC). In experimental and clinical studies, a unilateral lesion of riMLF leads to a loss of torsional saccades to the ipsilesional side, and vertical saccades are slower. In addition, there is a torsional nystagmus with the fast phase beating to the contralesional side. Experimentally, an iC lesion leads to ipsilesional torsional nystagmus with a conjugate vertical component and a vertical gaze-holding deficit. Saccade velocity is not reduced. Clinically, there appears to be no report with a lesion confined to the iC. Clinical studies with ‘presumed’ iC lesion effects differ in several aspects from experimental studies. The torsional nystagmus has a vertical see-saw component, and there is no major vertical gaze-holding deficit. Based on the present evidence and taking into consideration that a loss of ipsilesional torsional saccades is difficult to detect, the most convenient clinical sign to distinguish an involvement of riMLF or iC in a unilateral mesencephalic lesion is the direction of the torsional nystagmus: it is ipsilesional with an iC lesion and contralesional with an riMLF lesion.

Positional nystagmus in the dark in normal subjects

Horizontal and vertical components of spontaneous nystagmus in the dark were assessed in 40 healthy subjects with monocular computerised video-oculography. Five different static head-in-space positions were used: sitting upright, face up, right ear down, left ear down, and face down; the head-on-trunk position being kept the same in each position. In the sitting position, four subjects (10%) had downbeat nystagmus (slow-phase velocity [SPV] 0.7 °/s, SD 0.27) and 12 (30%) had upbeat nystagmus (SPV 2.58 °/s, SD 1.38). In the supine position, three subjects (7.5%) had downbeat nystagmus (SPV 5.60 °/s, SD 6.72) and 25 (62.5%) had upbeat nystagmus (SPV 3.86 °/s, SD 4.54). The direction of nystagmus frequently changed with changes in head position. In 15 subjects, the behaviour of the vertical nystagmus was investigated during a slow 1.2 °/s, 360° revolution in pitch. All subjects had nystagmus at some point and the slow-phase velocity was modulated sinusoidally suggestive of gravitational modulation by otolithic signals with an offset towards upbeat nystagmus. Normal subjects have a physiological spontaneous nystagmus of low velocity in the dark, often upbeating, which is under the modulation of otolith input.

メニエール病でみられる眼振の性質

Typical spontaneous nystagmus associated with Meniere's disease has been known to have a characteristic pattern consisting of horizontal, or horizontal and rotatory nystagmus beating toward the unaffected ear during the acute phase of the attack, followed by a reversal of the nystagmus direction as the patient recovers. However, different types of nystagmus were observed occasionally in some Meniere's disease patients by our experiments. The goal of this study is to investigate the character of nystagmus and to determine if there is atypical nystagmus in Meniere's disease. The positional nystagmus of forty-six Meniere's disease patients who visited the Department of Otolaryngology, Facility of Medicine, Aichi Medical University, was investigated retrospectively.The results were as follows: 1) Spontaneous nystagmus was observed in thirty-five patients (76%) on their first visit to the hospital.2) There was no significant difference between the groups when observing the nystagmus beating toward the affected ear and the unaffected ear.3) Benign paroxysmal positional vertigo (BPPV) was observed in five patients while down beat nystagmus was revealed in four patients during their visits to the hospital.4) No evidence of central disturbance, when examined by CT and MRI, was observed in the four patients combined with down beat nystagmus.As many scientists agree, endolymphatic hydrops in the inner ear was attempted to explain the etiology of Meniere's disease. The endolymphatic hydrops may cause debris in the inner ear and induce the BPPV which was observed in this study. Generally, the down beat nystagmus was only observed in the central origin. However, it can be also revealed when bilateral peripheral disfunction happens. The down beat nystagmus reported in this study may indicate bilateral Meniere's disease. In comparison with the typical nystagmus, we suggest there is atypical nystagmus in the Meniere's disease.

The head shaking nystagmus

The head shaking nystagmus is a sign of vestibular assymmetry. Its detection is simple office test useful for screening the patients with vertigo and dysequilibrium. Its nature defies its recording with electro-oculography and is simply observed under Frenzel's glasses. The direction of nystagmus is persistently directed away from the site of lesion and is not influenced by the compensatory adjustments. It is transient, rotatory and repeatable in nature. Its reliability is limited in face of the difficulty in its recognition. In presence of strong spontaneous nystagmus in the same face, it is not recognised easily. In the present study, its validity in peripheral disorders was 49.27% and 14% in central cases. There are limitations In earring out this test in situations of railed intracranial the tension, hence, its use in the latter cases is limited.

Optokinetic nystagmus with spontaneous reversal of transparent motion perception.

When two visual patterns moving in opposite directions are superimposed, they appear to be at different depths and to slide over each other. Because the stimulus does not specify the depth-order between the surfaces, this transparent motion perception is essentially ambiguous. With prolonged observation, the perceived depth-order of the two moving surfaces reverses spontaneously. In the present study, the correlation between the perceived direction of transparent motion and optokinetic nystagmus (OKN) was examined. While viewing superimposed random-dot patterns moving in opposite horizontal or vertical directions, subjects attempted to fixate the center of the stimulus, while paying attention to either the near or far depth plane, and reported any changes of the direction of surface-motion at the attended depth. Even with attention focused on a particular depth, the spontaneous reversal of transparent motion perception still occurred. This indicates that the perceptual reversal may reflect a preattentive mechanism for depth-from-motion. Furthermore, the OKN slow-phase tended to be in the same direction as the perceived motion of the surface at the attended depth. These results support the idea that the mechanisms for OKN maintenance are sensitive to perception of depth-from-motion and, therefore, cortically mediated.

The direction of nystagmus is important for the diagnosis of central paroxysmal positioning nystagmus (cPPV)

Head-positioning maneuvers can lead to paroxysmal nystagmus and vertigo, which are usually due to a peripheral vestibular disorder like, for example, benign paroxysmal positioning vertigo (BPPV). They are less commonly caused by a central lesion (central paroxysmal positioning nystagmus, cPPV). While many typical features do not permit differentiation between BPPV and cPPV, for example, latency, course, and duration of nystagmus and vertigo during an attack, the direction of nystagmus often does. The nystagmus in BPPV always beats in the direction aligned to the affected semicircular canal plane, i.e., horizontal for the horizontal canal and vertical-torsional for the vertical canals. Any other direction (paroxysmal torsional, upbeat, or downbeat nystagmus) indicates a central origin. Three cases of cPPV exhibiting nystagmus in the latter directions are presented. In one of the cases with paroxysmal downbeat nystagmus and vertigo, all other parts of the neurological examination and brain imaging initially showed no lesion in the posterior fossa. The direction of nystagmus was the only sign that indicated a central origin.

Diagnostic Criteria for Central versus Peripheral Positioning Nystagmus and Vertigo: a Review

Head positioning can lead to pathological nystagmus and vertigo. In most instances the cause is a peripheral vestibular disorder, as in benign paroxysmal positioning vertigo (BPPV). Central lesions can lead to positional nystagmus (central PN) or to paroxysmal positioning nystagmus and vertigo (central PPV). Lesions in central PPV are often found dorsolateral to the fourth ventricle or in the dorsal vermis. This localization, together with other clinical features (associated cerebellar and oculomotor signs), generally allows one to easily distinguish central PPV from BPPV. However, in individual cases this may prove difficult, since the two syndromes share many features. Even if only BPPV as a peripheral lesion is considered, differentiation based on such features as latency, course, and duration of nystagmus during an attack, fatigability, vertigo, vomiting, and time period during which nystagmus bouts occur, may be impossible. Only the direction of nystagmus during an attack can allow differentiation.

外側半規管型ＢＰＰＶに対する頭部傾斜・捻転法

Benign paroxysmal positional vertigo (BPPV) of lateral semicircular canal variant is characterized by geotropic nystagmus when the head is turned from the supine to either lateral position.The modified Lempert method, one of the canalith repositioning methods, had been reported to be effective for BPPV of lateral canal type. After this method was performed, however, a patient presented ageotropic nystagmus when the head was turned from the supine to either lateral position. This change in the direction of nystagmus seemed to indicate the conversion of canalolithiasis to cupulolithiasis. A canalith was thought to have moved from the proper canal of the lateral canal to the utricle, and moreover, into the cupula from the orifice of the ampulla of the lateral canal. Since this event, we have adopted the head tilt and rotation method. Its effect is as quick as that of the modified Lempert method, and no unfavorable side effects seen in modified Lempert method were observed.

垂直半規管の回転検査 頭位別の眼球運動解析

Benign Paroxysmal positioning vertigo and acoustic tumors are thought to be related to the function of the vertical semicircular canal (VSCC). Therefore, we developed a new test to assess VSCC function by analyzing VSCC-induced nystagmus. We examined 11 healthy subjects, wearing goggles equipped with an infrared CCD camera and sitting on a chair designed to bilaterally stimulate the VSCCs by tilting the head backward during 45° rotation to the right on the sagital plane. The stimuli used were sinusoidal rotation with a maximal angular velocity of 100°/sec at a frequency of 0.033 Hz. The result was that the maximum slow phase eye velocity (MSPEV) of horizontal nystagmus decreased parallel to the head-tilted angle and the MSPEV of the vertical nystagmus was maximal when the head was tilted 60° or 70° backward. From the perspective of VSCC anatomy, the direction of horizontal nystagmus is reversed when head is tilted 60° backward. However, we could not observe the reverse of the direction of horizontal nystagmus even when head tilted 80° backward. We considered that vertical nystagmus was maximal when the head was tilted 60-70° backward because this position applied the optimal stimulation to the VSCC. This finding is in agreement with the position of the vertical VSCC in skull. We concluded that rotational test with respect to the VSCC can be used to analyze VSCC function.

めまいと難聴を呈したＶ‐Ｐシャント不全例

A case of ventro-peritoneal (V-P shunt) shunt insufficiency with dizziness and sensorial hearing loss is reported. The patient was a sixteen-year-old boy who had been diagnosed as hydrocephalic at six of age. Subdural space-peritoneal shunt was performed in February 1980, but because of the insufficiency, V-P shunt was subsequently required in September 1984. He began to experience dizziness in the middle of September 1995, which worsened with both standing and sitting. While his dizziness was improved in the supine position, however, it was gradually accompanied by progressive headache, nausea and vomiting. The patient subsequently admitted to a hospital, where a brain CT scan revealed narrow and slit-like ventricles. Further exacerbation of a month resulted in transfer of the patient to the department of a neurosurgery in Kanagawa Rehabilitation hospital and consulted for a neurlo-otological examination. Directional nystagmus detected during the initial examination had disappeared but left-sided positional horizontal nystagmus was found the following day. The eye tracking test revealed ataxia while the optokinetic pattern was lightly impaired. The result of the caloric test were normal. The right ear showed sensorial hearing loss at all frequencies which was more marked in the lower frequencies. The left showed sensorial hearing loss in the lower frequencies. The patient's cerebral spinal pressure was 1-2 mmH2O in supine position and 0 mmH2O at thirty degrees with the head up. The patient's hearing loss was gradually recovered. After reconstruction of the V-P shunt, however, the hearing loss in lower frequencies remained. Although endolymphatic hydrops due to shut insufficiency was initially thought to have caused this patient's dizziness and hearing loss, the result of the caloric test was normal. The neuro-otological findings revealed the possibility that the dizziness originated in the cerebellum although the real cause remains uncertain. Fluctuating hearing loss without dizziness and vertigo has reported previously in a case of V-P shunt insufficiency. The observation suggested V-P shunt insufficiency can be clinically divided into two types, one of which the chief symptom was marked hearing loss without dizziness and the other one of which is characterized by hearing loss without dizziness.