Electronystagmography (ENG) is an equilibrium function test that records eye movements. Its objectives are to detect asymmetry in peripheral vestibular function and to detect central nervous system disorders. The merits of ENG are as follows: 1) various types of eye movements, including nystagmus, can be recorded; 2) nystagmus can be quantitatively analyzed; and 3) eye movement with the eyes closed and with the eyes open in darkness can be recorded. A weakness of ENG is that while it can record eye movement in the horizontal and vertical directions, it is not capable of recording rotatory eye movements. In clinical practice, ENG is used to detect the following: 1) spontaneous ocular motility in bright light and in the absence of fixation (with the eyes closed and with the eyes open in darkness); 2) gaze nystagmus; 3) positional nystagmus; 4) positioning nystagmus; 5) smooth pursuit; 6) optokinetic nystagmus; 7) saccade; 8) rotatory nystagmus; 9) caloric nystagmus; and 10) visual suppression. ENG can be performed with either binocular or monocular leads, and the latter is used particularly for recording of dysconjugate ocular motility, which occurs with supranuclear ocular motility disorders such as MLF syndrome. Although ENG is being used for diagnosis of dizziness and disequilibrium, we must not place too trust on the results of ENG tests. ENG is only a test of eye movement, and the causal relationship between ENG results and lesions must be determined by the users themselves. Recently, the use of videooculography (VOG) using an infrared CCD camera that also enables recording of rotatory eye movements has gradually spread, while the use of ENG is in decline.
We have translated the dizziness handicap questionnaires (DHI), which were one of the dizziness questionnaires of a few years ago, confirmed the reliability and applied our results in our clinical research. However each of the sentences in the DHI is not always familiar to the individual dizzy patient. Some other type of questionnaires would therefore be better for some dizzy patients. A vertigo handicap questionnaire (VHQ) is one of the questionnaires for the quantitative evaluation of the degrees of handicap in the daily lives of patients with vestibular disorders. It consists of 25 questions. The aim of the present study was to examine the validity and reliability of the Japanese translation of the VHQ (VHQ-J). The VHQ-J was undergone by 110 patients suffering dizziness. The results were analyzed and are summarized as follows: (1) Cronbach's alpha coefficient, which measures the reliability based on the consistency of the questionnaire, was 0.78. (2) The VHQ-J components significantly correlated with the Dizziness handicap inventory (DHI-J) (p<0.05). (3) The VHQ-J results significantly correlated with the Hospital Anxiety and Depression Scale (HADS) (p<0.05). (4) The VHQ-J significantly correlated with the State-Trait Anxiety Inventory (STAI) (p<0.05). These results indicated that the VHQ- J is a valid and reliable questionnaire that can be used to assess the degree of handicap in the daily lives of patients with vestibular disorders.
We investigated the efficiency of a micropressure pulse generator, Meniett® in controlling the symptoms of patients with intractable Meniere's disease. Nine patients with intractable vertigo despite adequate medical treatment underwent the placement of a standard tympanostomy tube. Seven of these patients self-administered Meniett® three times a day because their vertigo symptoms were not improved by the placement of a standard tympanostomy tube only. The treatment periods with Meniett® ranged from 6 to 38 months with an average of 18.3 months, and the follow up periods ranged from 12 to 38 months with an average of 23.9 months. Five patients did respond to the device and it reduced the frequency and severity of their vertigo attacks, however 2 patients did not show adequate benefits. Two patients showed an improvement in hearing level after a follow-up of 12 months. In addition, there was no complication during the follow-up periods. These results suggest that Meniett® is effective and safe in controlling vestibular symptoms.
The origin of the vertical component of caloric nystagmus is unknown. Recent developments in magnetic resonance imaging have enabled precise measurement of the labyrinth. We aimed to explain the direction of the vertical component of caloric nystagmus by assessing the spatial orientation of semicircular canals using MR imaging. Some authors suspected that the inclination of the lateral semicircular canal in respect with the head sagittal plane is the origin of the vertical component of the caloric nystagmus. Other authors suspected that the concurrent activation of 2 vertical canals may be the origin of the vertical component. Therefore, in a group of vertiginous patients we measured the angle between the horizontal canal plane and the head sagittal plane. Further, we calculated the difference of angles between the posterior and anterior canal plane to the head sagittal plane. We compared those values with the direction of the vertical component of caloric nystagmus recorded in those ears. However, neither of those values were related to the direction of the vertical component of caloric nystagmus. We could not explain the direction of the vertical component of caloric nystagmus by special orientation of semicircular canals and assumed that additional influences of other peripheral or central vestibular factors were the potential reason.
We investigated the availability of the newly developed portable type of device for measuring subjective visual vertical (SVV). The new device consisted of a monocular telescope-like body and a ring attached to rotate a bar inside the body. The device was fixed on a small board. When subjects looked into the telescope-like body, they found a red bar sign tilted by the examiner. They were then asked to rotate the bar sign to the subjective vertical position using the attached ring. The results using the portable device in 20 healthy subjects and 6 patients with peripheral vestibular disorders showed a close correlation with those using a conventional fixed type of a device, which had a light-emitting diode (LED) bar operated by a joy-stick. This new method requires neither darkroom nor electric power supply. Our results suggested that we could measure SVV with this newly developed device wherever examiners might want.
The vestibulo-ocular reflex (VOR) generates smooth eye movements that compensate for head movements to ensure gaze stabilization during head rotation. The VOR is under adaptive control and corrects VOR performance when visual-vestibular mismatch arises during head movement. During normal visual-vestibular interaction, cooperation between the VOR and vision results in stabilization of the retinal image. Adaptive VOR recalibration occurs when visual-vestibular mismatch arises through the manipulation of visual feedback during head movement. In consideration of how important VOR is in stabilizing gaze, it could be predicted that when VOR is lost, patients would be severely disabled by retinal image movement due to head movement. The vestibular center uses substitutes such as visual and somatosensory information to compensate for lost vestibular signals. In the present study, to investigate the contribution of somatosensory signals to VOR, especially the otolith-ocular reflex (OOR), we examined the plasticity of the OOR using vestibular-somatosensory interaction and the effect of the adaptive plasticity of the OOR by somatosensory stimulation using alternative pressure stimulation on the outer side of the bilateral upper arms for 20 seconds. To study the influence of somatosensory input on the otolith-ocular reflex, we used sinusoidal off-vertical axis rotation at a tilt angle of 30 degrees. Subjects were rotated with their eyes open in complete darkness at frequencies of 0.32 Hz with a maximum angular velocity of 60 o/s. Results showed a significant gain decrement in EVAR after somatosensory adaptive stimulation, whereas gain change was not significantly different in OVAR. We suggest that somatosensory input had an additive effect on the otolith-ocular reflex in this study. This result could be applied to vestibular rehabilitation using somatosensory input.