Yasuko Arai

Eye-Head Coordination During Lateral Gaze in Normal Subjects

To elucidate the characteristics of eye-head coordination during lateral gaze, eye, head and gaze displacements to 10 degrees, 20 degrees, 30 degrees, 40 degrees, and 50 degrees target presentations were analysed quantitatively in 10 normal subjects. Head displacement was recorded without mechanical restraint by a newly devised apparatus containing two terrestrial magnetic sensors. Eye movements were recorded using d.c. electro-oculography through bitemproal leads. (1) As the target angle increased, the latency of eye movement increased while that of head movements decreased. (2) The rise times of eye and head movements increased almost linearly with the target angle. (3) The maximum velocity of eye movement averaged 292 degrees/sec at 10 degrees, increased to 398 degrees/sec at 20 degrees, and remained unchanged thereafter. The maximum velocity of head movement increased linearly with the target angle. (4) The head displacement at the end of eye saccade became relatively larger as the target angle increased, though the sum of eye and head displacements, i.e. gaze, agreed with the target angle. (5) At the final resting position, the percentage of target angle attained by head displacement decreased from 93% to 10 degrees to 62% at 50 degrees. However, gaze displacement was exactly the same as the target angle, with little dispersion for each angle of gaze shift, indicating that the head rotation detector is an accurate device for recording horizontal head movement under natural conditions.

Three-dimensional analysis of caloric nystagmus in the rhesus monkey.

The aim of this study was to investigate whether caloric nystagmus contains response components that can be attributed to a stimulation of the vertical semicircular canals. Three dimensional eye movement recordings with a dual search coil technique revealed important horizontal, vertical and torsional nystagmus components following irrigation of the external ear canal with cold water in various head positions relative to gravity. Horizontal nystagmus components, i.e. lateral semicircular canal vectors, followed a cosine function of both the pitch and yaw angle of the head relative to gravity, confirming a mainly thermovective mechanism for stimulation of the horizontal canals. Vertical and torsional nystagmus components behaved differently following left and right ear irrigations. Right-left symmetrical vectors emerged only when the vertical and torsional components were transposed into vectors of single semicircular canal directions. The intensity of these vertical semicircular canal vectors as a function of the position of the corresponding canal relative to gravity, however, excludes important thermovective mechanisms acting at the vertical canals. It remains an open question whether these vertical canal vectors represent a non-thermovective caloric stimulation of vertical canal afferents.

Planer orientation of the bilateral semicircular canals in dizzy patients

OBJECTIVE Recent development of 3-dimensional analysis of eye movement enabled to detect the eye rotation axis, which is used to determine the responsible semicircular canal(s) in dizzy patients. Therefore, the knowledge of anatomical orientation of bilateral semicircular canals is essential, as all 6 canals influence the eye movements. SUBJECTS AND METHODS Employing the new head coordinate system suitable for MR imaging, we calculated the angles of semicircular canal planes of both ears in 11 dizzy patients who had normal caloric response in both ears. RESULTS The angles between adjacent canal pairs were nearly perpendicular in both ears. The angle between the posterior canal planes and head sagittal plane was 51° and significantly larger the angle between the anterior canal planes and head sagittal plane, which was 35°. The angle between the horizontal canal plane and head sagittal plane was almost orthogonal. Pairs of contralateral synergistic canal planes were not parallel, forming 10° between right and left horizontal canal planes, 17° between right anterior and left posterior canal planes and 19° between the right posterior and left anterior canal planes. CONCLUSION Our measurement of the angles of adjacent canal pairs and the angle between each semicircular canal and head sagittal plane coincided with those of previous reports obtained from CT images and skull specimens. However, the angles between contralateral synergistic canal planes were more parallel than those of previous reports.

A head-tilt caloric test for evaluating the vertical semicircular canal function.

Conclusions: The caloric test with head-tilt can be used as a tool for assessing vertical canal function as an office procedure. Objective: Evaluation of vertical canal function. Patients and methods: We provoked caloric response by cold water in the vertiginous patients in supine position. During the culmination of the response we rotated the head 45° from the sagittal plane to place the posterior canal to earth-vertical. Thereafter we rotated the head 45° to the opposite direction to place the anterior canal to earth-vertical. The eye movements were recorded by two-dimensional electronystagmography. The data collected from the examination of 100 ears with normal caloric response in horizontal component were analyzed. Results: The down-beating vertical component intensified when the posterior canal was placed to earth-vertical. The up-beating vertical component intensified when the anterior canal was placed to earth-vertical. These findings suggested that the vertical canals were functioning.

Clinical significance of vertical component of caloric response including its second phase in vertiginous patients

Conclusions. Up-beating vertical component recorded in the caloric first phase was attributed mainly to the inhibitory endolymph flow in the anterior canal. Down-beating vertical component recorded in the caloric second phase provoked by a positional change could be explained by a reversed endolymph flow in vertical canal(s). Objective. To investigate the origin of a vertical component in caloric response. Materials and methods. We analyzed electronystagmography (ENG) of caloric responses, which had measurable horizontal component in the caloric first phase in both ears in 200 ears of 100 vertiginous patients. A caloric first phase was provoked by cold water in the supine position with the lateral semicircular canal earth-vertical. A caloric second phase was provoked by re-orienting the lateral canal from the earth-vertical to earth-horizontal after the cessation of the first phase (provoked second phase). The nystagmus of the whole procedure was recorded by two-dimensional ENG. Results. We recorded the vertical component in 103/200 ears in the caloric first phase, which was directed mostly upward (92/103 ears). We also recorded the vertical component in 91/200 ears in the provoked second phase, which was directed almost exclusively downward (90/91 ears).

Effects of Semicircular Canal Plugging on Caloric Nystagmus Recorded in Three Dimensions

In Rhesus monkeys, distinct eye movement response components in the planes of the semicircular canals (canal plane vectors, CPV) were identified by 3-dimensional recordings of caloric nystagmus elicited in different head positions relative to gravity. Surgical plugging of single semicircular canals (SCC) was used to identify the generators of these response components. The lateral CPV is a sinusoidal function of head position, compatible with a thermovective mechanisms in this canal. Surgical plugging of the lateral SCC leaves only a small head position independent, lateral CPV, probably due to direct temperature effects on lateral SCC afferents. The posterior and anterior CPVs are complex responses composed of various components of which the present plugging experiments identified two generators: i) effects of thermovection in the lateral SCC, demonstrated by modifications of posterior and anterior CPVs after occlusion of the lateral SCC; and ii) thermovection in the vertical SCCs, demonstrated by effects of plugging a single vertical SCC exclusively on the corresponding CPV. This is the first definite identification of the vertical SCCs as contributors to the generation of nystagmus induced by caloric irrigation of the outer ear canal. It may provide a basis for the development of a modified caloric test measuring more than only lateral canal function in human patients.

A new coordinates system for cranial organs using magnetic resonance imaging.

Abstract Conclusion: We developed a new coordinates system for magnetic resonance imaging (MRI) that utilizes the labyrinth and eyeballs as references to measure the spatial arrangement of cranial organs, and we verified its usefulness by observing small structures in the labyrinth in 39 ears from 33 patients. Our new coordinates system could be used for stereotactic analysis of cranial organs in MRI. Objectives: To research semicircular canal anatomy in healthy organisms, we propose a method that employs references visible on MRI for stereotactic measurement of cranial structures, and we evaluated the usefulness of our method. Methods: Using the new coordinates system and vector analysis, we calculated angles among the semicircular canals and sagittal head plane from MRI volume data containing temporal bone and orbit. Results: The angle between the anterior semicircular canal plane and sagittal plane was 35.3 ± 4.1°; posterior semicircular canal plane and sagittal plane, 50.9 ± 4.7°; and horizontal semicircular canal plane and sagittal plane, 90.4 ± 7.0°. The angle between the anterior and posterior semicircular canal planes was 95.1 ± 4.2°; anterior and horizontal semicircular canal planes, 92.3 ± 7.5°; and posterior and horizontal semicircular canal planes, 93.5 ± 4.9°.

Dual-Energy Subtraction Imaging for Diagnosing Vocal Cord Paralysis with Flat Panel Detector Radiography

Objective To investigate the clinical feasibility of dual energy subtraction (DES) imaging to improve the delineation of the vocal cord and diagnostic accuracy of vocal cord paralysis as compared with the anterior-posterior view of flat panel detector (FPD) neck radiography. Materials and Methods For 122 consecutive patients who underwent both a flexible laryngoscopy and conventional/DES FPD radiography, three blinded readers retrospectively graded the radiographs during phonation and inspiration on a scale of 1 (poor) to 5 (excellent) for the delineation of the vocal cord, and in consensus, reviewed the diagnostic accuracy of vocal cord paralysis employing the laryngoscopy as the reference. We compared vocal cord delineation scores and accuracy of vocal cord paralysis diagnosis by both conventional and DES techniques using κ statistics and assessing the area under the receiver operating characteristic curve (AUC). Results Vocal cord delineation scores by DES (mean, 4.2 ± 0.4) were significantly higher than those by conventional imaging (mean, 3.3 ± 0.5) (p < 0.0001). Sensitivity for diagnosing vocal cord paralysis by the conventional technique was 25%, whereas the specificity was 94%. Sensitivity by DES was 75%, whereas the specificity was 96%. The diagnostic accuracy by DES was significantly superior (κ = 0.60, AUC = 0.909) to that by conventional technique (κ = 0.18, AUC = 0.852) (p = 0.038). Conclusion Dual energy subtraction is a superior method compared to the conventional FPD radiography for delineating the vocal cord and accurately diagnosing vocal cord paralysis.

Horizontal saccadic palsy associated with gliosis of the brainstem midline

We studied premotor cell groups involved in the generation of saccades in a patient with a disturbance of voluntary horizontal gaze. The only neurological symptom found was a slowing of horizontal saccades, reported since birth and unaltered over his lifetime. We attribute this disorder, for the first time, to a fibrous gliosis of the brainstem midline, which may disrupt neuronal elements of the horizontal saccade generator crossing the brainstem midline, but it caused no obvious loss of omnipause-, excitatory burst-, and inhibitory burst neurons. No neuronal loss or demyelination, was apparent elsewhere in the brainstem; but there was evidence of an ependymal infection throughout the entire ventricular system. A diagnosis of Gaucher disease was made from the bone marrow of this patient shortly before his death, but for several reasons we considered this complication unlikely to be the cause of the saccadic disorder.

Management of peritonsillar abscess

Abstract To attempt to determine the appropriate management for peritonsillar abscess (PTA) and recurrences, we retrospectively analyzed 337 PTA and recurrent PTA, referred to our department between 1995 and 2002. Of the 205 patients treated surgically; needle aspiration was performed in 52 (15%), incision and drainage in 108 (32%), immediate abscess tonsillectomy in 42 (12%), and neck incision in 3 (1%), and 69 patients (20%) were treated medically with antibiotics alone. Interval tonsillectomy was performed in 39 patients (12%). Among 106 patients who did not undergo tonsillectomy, PTA recurred an average of 2.0 months after recovery from previous PTA. Patients not treated by tonsillectomy should be carefully followed for at least 3 months. Abscess or early interval tonsillectomy should be considered in PTA patients under 40 years old, because they have a high rate of recurrence of PTA.