Over the past few decades, various cortical regions in primates have been labeled as vestibular: area 2v, area 3, area 7, superior temporal gyrus and parieto-insular vestibular cortex (PIVC). These areas have reciprocal connections with each other and form an "inner circuit." The PIVC physiologically responds well to vestibular stimulation as well as visual and somatosensory inputs. It also morphologically receives projections from all other vestibular cortical regions. Thus these findings suggest that PIVC integrates multisensory information from different cortical areas. The PIVC may play a major role in the cortical vestibular system. We recorded neuromagnetic responses to visually-induced linear forward acceleration in humans using a 122-channel whole cortex neuromagnetometer. In the study, visual stimulation without vestibular stimulation induced activation in the PIVC in humans. Hence, it is suggested that the vestibular cortex not only receives vestibulr inputs from peripheral vestibular apparatus, but also produces vestibular sensation using other multi-model inputs. The monkey, cat and rat have homologous vestibular cortical system over species, which projects corticofugally onto the vestibular nuclei. These projections may play a role in an antagonistic coordination of involuntary oculomotor and skeletomotor movements during head movements or locomotion.
We investigated the distribution of the maximum velocity of the slow phase of nystagmus (max. spv) induced by cold air caloric stimulation, that were evaluated as normal responses in different age groups. Test subjects who had no spontaneous nystagmus with eyes open in darkness and showed max. spv of caloric nystagmus above 20 degrees/sec were selected. The distribution histogram of the values of max. spv in all 355 subjects (710 ears) was skewed and different from Gaussian distribution. Each value was much more concentrated at the level above the mean value than at the level below it. The subjects were classified into three groups, such as the younger (20-39 years old), the middle aged (40-64 years old) and the older group (above 65 years old) and the distribution of max. spv in each group did not show a Gaussian distribution. The mean value of max. spv in the younger group was significantly higher than one in the older group. The values in both the younger and middle aged group tended to be higher than the mean but those in the older group did not. In conclusion, we must remain aware that when we obtain the normal range of cold air caloric nystagmus, max. spv of caloric nystagmus does not show a Gaussian distribution, especially in the elderly.
We reported a patient with cavernous hemangioma of the internal auditory canal. A 47-year-old man demonstrated progressive hearing loss and facial palsy on the left hand side over 4 years. A small tumor was detected in his left internal auditory canal by magnetic resonance imaging (MRI). The lesion displayed iso-signal intensity in T1-weighted images, high signal intensity in T2-weight images, and positive Gadolinium enhancement. Under tentative diagnosis as neurinoma, the tumor was totally removed by the translabyrinthine approach. The red tumor had compressed the facial and cochlear nerves, and adhered to the vestibular nerve in the internal auditory canal. It was diagnosed as cavernous hemangioma by immunohistochemical examination. There has not been any sign of recurrent tumors, but hearing loss and left facial palsy persisted after surgery. A cavernous hemangioma of the internal auditory canal tends to manifest with progressive hearing loss and facial palsy based on a review of past reports.
We devised a new three-dimensional eye movement image analysis technique using a commercialized infrared CCD camera, a personal computer and public domain software. Image analysis was performed automatically using the public domain software NIH Image. 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 each 0.1 degrees, 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. Rotational axis of the eyeball was calculated from three-dimensional data using the coordinates transformation technique. As a result of the analysis of artificial eye movement images, the average error of the torsional component was 0.06+/-0.09 degrees for each 1 second, and was 0.31+/-0.46 degrees for 5 seconds. Using this technique, it is possible to inexpensively perform three-dimensional eye movement analysis and rotational axis analysis from video images recorded by many types of infrared CCD cameras.