Horizontal Semicircular Canal Plane Research Articles

Active and Adequate Exposure of the Facial Nerve and Chorda Tympani Nerve to Improve the Safety of Cochlear Implantation.

The posterior tympanum approach of cochlear implantation is easy to damage the facial nerve and cord tympanic nerve. Therefore, we need to improve the safety of cochlear implantation. To discuss the safety and feasibility of active and adequate transparent exposure of the facial nerve and chorda tympani nerve during the surgery. A retrospective analysis was performed on all 945 patients who underwent cochlear implantation from January 2011 to September 2017. All patients have been followed up for 14 months to 5 years postoperatively and postoperative complications have been observed. All 945 patients received artificial cochlear implantation. The facial nerves of 76 cases were above the horizontal semicircular canal plane, while narrow facial recess was observed in 44 cases. Serious chorda tympani nerve variation was found in 1 case. No facial paralysis and facial nerve irritation and abnormal taste occurred after operation. Cochlear implantation with initiative and adequate exposure of facial nerve and the chorda tympani nerve can improve the safety of the cochlear implant surgery. Our study provide a safe and effective method for clinical cochlear implantation to reduce facial nerve and tympanic cord nerve injury.

Effect of peripheral vestibular pathologies on reading ability and auditory-verbal memory

Background and Aim: Auditory-verbal mem­ory and reading problems are frequently obser­ved in patients with vestibular disorders, but rarely considered as a cognitive consequence of vestibular disease. Many clinicians do not rec­ognize or ignore the psychological symptoms of vestibular disease. This approach could under­estimate the cognitive problems of the patients, or even led to misdiagnosis of a combined ves­tibular-cognitive condition. The current study aimed to assess the cognitive impact of acute vestibular disorders. Methods: A total of 71 patients with unilateral vestibular neuritis, Meniere’s disease, and ben­ign paroxysmal positional vertigo underwent a through audiologic evaluation, including otos­copy, pure tone audiometry, tympanometry, vestibular evoked myogenic potentials, video­nystagmography plus caloric testing, and video head impulse testing in the plane of horizontal semicircular canals. After determination of the disease, the Persian version of the dizziness handicap inventory, the Persian reading test, and Rey auditory-verbal learning test were admi­nistered. Results: There were no significant difference between the patient groups with regard to their inabilities like reading and learning problems according to their auditory verbal memory score induced by acute vertigo. However, acute ver­tigo can reduce the reading ability and capacity of auditory-verbal memory of the patients com­pared with normal subjects. Conclusion: Unilateral vestibular disorders in which patients suffer from acute rotatory vertigo could lead to reading difficulties and learning because of auditory-verbal memory impairment. The exact mechanism of vestibular impairment is not a determinant factor for these cognitive problems.

Motion Illusion-Evidence towards Human Vestibulo-Thalamic Projections.

Contemporary studies speculated that cerebellar network responsible for motion perception projects to the cerebral cortex via vestibulo-thalamus. Here, we sought for the physiological properties of vestibulo-thalamic pathway responsible for the motion perception. Healthy subjects and the patient with focal vestibulo-thalamic lacunar stroke spun a hand-held rheostat to approximate the value of perceived angular velocity during whole-body passive earth-vertical axis rotations in yaw plane. Vestibulo-ocular reflex was simultaneously measured with high-resolution search coils (paradigm 1). In primates, the vestibulo-thalamic projections remain medial and then dorsomedial to the subthalamus. Therefore, the paradigm 2 assessed the effects of high-frequency subthalamic nucleus electrical stimulation through the medial and caudal deep brain stimulation electrode in five subjects with Parkinson's disease. Paradigm 1 discovered directional mismatch of perceived rotation in a patient with vestibulo-thalamic lacune. There was no such mismatch in vestibulo-ocular reflex. Healthy subjects did not have such directional discrepancy of perceived motion. The results confirmed that perceived angular motion is relayed through the thalamus. Stimulation through medial and caudal-most electrode of subthalamic deep brain stimulator in paradigm 2 resulted in perception of rotational motion in the horizontal semicircular canal plane. One patient perceived riding a swing, a complex motion, possibly the combination of vertical canal and otolith-derived signals representing pitch and fore-aft motion, respectively. The results examined physiological properties of the vestibulo-thalamic pathway that passes in proximity to the subthalamic nucleus conducting pure semicircular canal signals and convergent signals from the semicircular canals and the otoliths.

The Age-Related Orientational Changes of Human Semicircular Canals.

ObjectivesSome changes are found in the labyrinth anatomy during postnatal development. Although the spatial orientation of semicircular canals was thought to be stable after birth, we investigated the age-related orientational changes of human semicircular canals during development.MethodsWe retrospectively studied the computed tomography (CT) images of both ears of 76 subjects ranged from 1 to 70 years old. They were divided into 4 groups: group A (1–6 years), group B (7–12 years), group C (13–18 years), and group D (>18 years). The anatomical landmarks of the inner ear structures were determined from CT images. Their coordinates were imported into MATLAB software for calculating the semicircular canals orientation, angles between semicircular canal planes and the jugular bulb (JB) position. Differences between age groups were analyzed using multivariate statistics. Relationships between variables were analyzed using Pearson analysis.ResultsThe angle between the anterior semicircular canal plane and the coronal plane, and the angle between the horizontal semicircular canal plane and the coronal plane were smaller in group D than those in group A (P<0.05). The JB position, especially the anteroposterior position of right JB, correlated to the semicircular canals orientation (P<0.05). However, no statistically significant differences in the angles between ipsilateral canal planes among different age groups were found.ConclusionThe semicircular canals had tendencies to tilt anteriorly simultaneously as a whole with age. The JB position correlated to the spatial arrangement of semicircular canals, especially the right JB. Our calculation method helps detect developmental and pathological changes in vestibular anatomy.

Analysis of the coplanarity of functional pairs of semicircular canals using three-dimensional images reconstructed from temporal bone magnetic resonance imaging.

This study was conducted to investigate the angles and orientation of semicircular canals, and the coplanarity of functional canal pairs. Fluid signals in semicircular canals were reconstructed with three-dimensional reconstruction software using 20 temporal bone magnetic resonance images of normal subjects. The angles between each pair of semicircular canals were measured. The mean angles between the anterior and horizontal semicircular canal plane, the horizontal and posterior semicircular canal plane, and the anterior and posterior semicircular canal plane were 83.7°, 82.5° and 88.4°, respectively. Pairs of contralateral synergistic canal planes were formed 15.1° between the right and left horizontal semicircular canal planes, 21.2° between the right anterior and left posterior semicircular canal, and 21.7° between the left anterior and right posterior semicircular canal. Each semicircular canal makes an almost right angle with other canals, but synergistically acting functional canal pairs of both ears do not lie in exactly the same plane.

Vestibular Dysfunction in Turner Syndrome

Turner syndrome is a well-known cause of sensorineural hearing loss, and the lack of estrogen has been implicated in cochlear dysfunction. It has never been associated with vestibular dysfunction. We report a case of a patient with Turner syndrome who was found to have bilateral vestibular dysfunction based on video-oculography (VOG) testing. A single patient with a history of Turner syndrome who was found to have significant bilateral vestibular dysfunction. After noticing a deficit in the vestibulo-ocular reflexes on qualitative horizontal head impulse examination, the patient underwent VOG testing. VOG testing quantatively measures angular vestibulo-ocular reflex (AVOR) gain in the horizontal semicircular canal plane. AVOR gain represents the eye movement response to a head movement; in normal individuals the eye movement is fully compensatory and gain values are close to unity. VOG results showed AVOR gains of 0.29 and 0.36 on the right and left sides, respectively. We have presented a case of a woman with Turner syndrome with asymptomatic vestibular dysfunction demonstrated with VOG testing. Although there is a documented relationship between Turner syndrome and sensorineural hearing loss, there are no previous studies or case reports linking Turner syndrome and vestibular dysfunction. Additional research and added vigilance in monitoring Turner syndrome patients may be warranted.

A case of apogeotropic nystagmus with brainstem lesion: An implication for mechanism of central apogeotropic nystagmus

We report a case showing apogeotropic nystagmus with the lesion of the brain stem, and discuss a possible mechanism of central apogeotropic nystagmus. The case was a 73-year-old male. We analyzed his nystagmus three-dimensionally. He showed apogeotropic nystagmus. Axis angles of slow phase eye velocity of his apogeotropic nystagmus were not in line with the axes perpendicular to the plane of horizontal semicircular canals, but with the patient's vertical axis. We then found that his nystagmus including the apogeotropic nystagmus was positioning, but not positional and that the direction of his positioning nystagmus was the same direction of postrotatory nystagmus after his head movement. His MRI scans showed an infarction around the prepositus hypoglossi nucleus of the brain. His apogeotropic nystagmus seemed to consist of a combination of prolonged postrotatory nystagmus after his head rotation to the left and right lateral position because the axis of postrotatory nystamus was in line with the axis of the head rotation. Therefore, it is suggested that a possible mechanism of central apogeotropic nystagmus is a prolonged postrotatory nystagmus after his head movement in the supine position due to the brain lesion involving the velocity storage mechanisms.

A new coordinates system for cranial organs using magnetic resonance imaging

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°.

Origin of Orientation-Dependent Asymmetries in Vestibulo-Ocular Reflexes Evoked by Caloric Stimulation

A caloric stimulus evokes primarily a horizontal vestibulo-ocular reflex (VOR) when subjects are in a supine or prone orientation with the horizontal semicircular canal plane oriented vertically. In both monkeys and humans, the magnitude of VOR eye movements is greater in the supine than in the prone orientation, indicating that some factor or factors, other than the conventionally accepted convective stimulation of the horizontal canals, contributes to the generation of the VOR. We used long-duration caloric irrigations and mathematical models of canal-otolith interactions to investigate factors contributing to the prone/supine asymmetry. Binaural caloric irrigations were applied for 7.5 or 9.5 min with subjects in a null orientation with horizontal canals in the earth-horizontal plane (control trial), or with the subject's pitch orientation periodically changing between null, supine, and prone positions with each orientation held for 30 s (caloric step trial). The control trial responses identified a small response attributable to a direct thermal effect on vestibular afferent activity that accounted for only 15% of the observed prone/supine asymmetry. We show that the gravito-inertial force resolution hypothesis for sensory integration of canal and otolith information predicts that the central processing of canal and otolith information produces an internal estimate of motion that includes both a rotational motion component and a linear acceleration component. These components evoke a horizontal angular VOR and linear VOR, which combine additively in the supine orientation, but subtract in the prone orientation, thus accounting for the majority of the observed prone/supine asymmetry.

Head stabilization during various locomotor tasks in humans

This experiment, which extends a previous investigation (Pozzo et al. 1990), was undertaken to examine how head position is controlled during natural locomotor tasks in both normal subjects (N) and patients with bilateral vestibular deficits (V). 10 normals and 7 patients were asked to perform 4 locomotor tasks: free walking (W), walking in place (WIP), running in place (R) and hopping (H). Head and body movements were recorded with a video system which allowed a computed 3 dimensional reconstruction of selected points in the sagittal plane. In order to determine the respective contribution of visual and vestibular cues in the control of head angular position, the 2 groups of subjects were tested in the light and in darkness. In darkness, the amplitude and velocity of head rotation decreased for N subjects; these parameters increased for V subjects, especially during R and H. In darkness, compared to the light condition, the mean position of a line placed on the Frankfort plane (about 20-30 degrees below the horizontal semi-circular canal plane) was tilted downward in all conditions of movement, except during H, for N subjects. In contrast, this flexion of the head was not systematic in V subjects: the Frankfort plane could be located above or below earth horizontal. In V subjects, head rotation was not found to be compensatory for head translation and the power spectrum analysis shows that head angular displacements in the sagittal plane contain mainly low frequencies (about 0.3-0.8 Hz). The respective contribution of visual and vestibular cues in the control of the orientation and the stabilization of the head in space is discussed.

Head stabilization during various locomotor tasks in humans

Head kinematics were studied in ten normal subjects while they executed various locomotor tasks. The movement of the body was recorded with a video system which allowed a computer reconstruction of motion of joint articulations and other selected points on the body in three dimensions. Analyses focus on head translation along the vertical axis and rotation in the sagittal plane. This was done by recording the displacement of a line approximating the plane of horizontal semi-circular canals (the Frankfort plane: F-P). Four conditions were studied: free walking (W) walking in place (WIP) running in place (R) and hopping (H). In the 4 experimental conditions, amplitude and velocity of head translation along the vertical axis ranged from 1 cm to 25 cm and 0.15 m/s to 1.8 m/s. In spite of the disparities in the tasks regarding the magnitude of dynamic components, we found a significant stabilization of the F-P around the earth horizontal. Maximum amplitude of F-P rotation did not exceed 20 degrees in the 4 situations. Vertical angular velocities increased from locomotion tasks to the dynamic equilibrium task although the maximum values remained less than 140 degrees/s. Predominant frequencies of translations and rotations in all the tasks were within the range 0.4-3.5 Hz and harmonics were present up to 6-8 Hz. During walking in darkness, mean head position is tilted downward, with the F-P always below the earth horizontal. Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, WIP and R, but during H the amplitude decreased by 37%. Residual head angular displacement is found to compensate for head translation during the 4 conditions. Our study emphasizes the importance of head stabilization as part of the postural control system and described as a basis for inertial guidance.

Chapter 13 Integration of vestibular and neck afferent signals in the central cervical nucleus

The responses of spinocerebellar tract neurons in the CCN to natural stimulation of vestibular and neck muscle receptors were investigated in decerebrate cats. The spike activity of single CCN neurons was recorded extracellularly with a floating microelectro-de in the C2 segment of the spinal cord. CCN neurons exhibited clear modulation of firing activity in response to sinusoidal rotation of the head in the vertical planes but not to rotation in the horizontal semicircular canal plane. The response to vertical rotation was attributed to stimulation of the vertical semicircular canals, since selective stimulation of otolith organs by static tilt of the head in the same plane had no effect. The response was approximately in phase with the head angular velocity at 0.05–2.0 Hz. Vector analysis suggested that the optimal orientation of vertical rotation varied considerably among neurons. The CCN neurons increased or decreased their firing rate in response to stretch of dorsal neck muscles. The time course of the responses suggested that muscle spindle primaries were most likely to be the receptors responsible for both excitatory and inhibitory responses. The input was highly muscle specific in that most CCN neurons received excitation from one muscle or two synergists, and that a group of neurons was specifically inhibited from biventer cervicis and complexus. The vestibular and neck muscle afferent signals converged with specific patterns of combination on individual CCN neurons. It is suggested that each CCN neuron integrates signals from the labyrinth and the neck and provides the cerebellum with information concerning the head movement in a certain vertical direction.