Koichiro Kanaya

GABA Distribution in the Central Vestibular System after Retroauricular Galvanic Stimulation: An Immunohistochemical Study

The changes of the neurotransmitter (GABA) distribution in the brain stem of rats by retroauricular galvanic stimulation were investigated using the immunohistochemical method. In the lateral vestibular nucleus GABA-like immunoreactivity was more intensive on the side ipsilateral to the anodal stimulation than on the other side. It is concluded that retroauricular galvanic stimulation causes some changes in the inhibitory activity of the lateral vestibulo-spinal tract and of the spinal motor neuron.

Compensatory process of vestibular neuronitis : from findings of combined galvanic test and caloric test

The compensatory process of vestibular neuronitis in 7 patients was followed up and evaluated using the Combined Galvanic Test (CGT) and other neuro-otological data. CGT is the simultaneous recording of both galvanic eye movement (GEM) and galvanic body sway (GBS), and has proved to be reliable in the diagnosis of retrolabyrinthine disorders. The results were as follows: The subjective symptoms remained in 3 cases from 1 month to 1 year. The recovery of the GBS response was seen earlier than that of both GEM and caloric responses. The recovery of GEM and caloric responses was observed at almost the same time. We observed the favorable recovery process of caloric response and GEM response in some cases which had recovery of GBS response within 4 weeks and suggest that the system of GBS response is different from that of GEM and caloric response. However, the systems of the latter two may be the same. We assume that the recovery of GBS response is earlier than that of GEM and caloric responses because the otolithic system recovers more easily than the semicircular canal system. The CGT and caloric test were reliable in examining the compensatory process of vestibular neuronitis.

Study of the Accuracy of Stance Regulation

In order to find a rule underlying the control of stance we recorded the center of pressure intermittently every 29 ms, first with subjects standing still for 30 s and then during shifting the center of gravity along the margin of the supporting area for 30 s to detect any movement. Subjects were 5 adult volunteers. They were examined with eyes open and closed as well as standing on one leg, closed legs, and legs 15 cm apart. The distribution of cumulated densities of the center of pressure, in a 3-D drawing, formed a very simple graph, i.e., a tower on a circle. As the difficulty of stance increased, the circle was reduced and the height of tower lowered, independently of visual or supporting condition. Since easy and difficult stances could be simulated by small and large values of SD in a regular distribution, stance may yield action-oriented computation based on probability.

Vestibular Neuronitis Evaluated by the Combined Galvanic Test

Forty-two patients with unilateral vestibular neuronitis were examined by the combined galvanic test (CGT), consisting of the galvanic eye movement test (GEMT) and the galvanic body sway test (GBST). Results of the CGT were evaluated with respect to the time period from the onset of vestibular neuronitis. A favorable recovery was observed earlier with the GBST than the GEMT. We believe that this discrepancy may be due to the difference in compensation between the vestibulo-ocular reflex and the vestibulo-spinal reflex.

Vestibular Compensation in Vestibular Neuronitis: Evaluation of Positional Nystagmus and Caloric Nystagmus

We evaluated the vestibular functions, especially for positional nystagmus and caloric nystagmus, in 43 cases of vestibular neuronitis for long periods after its onset. It is shown that in the cases of vestibular neuronitis that were studied more than 10 years after the onset of the disease, the completed vestibular compensation changed or the vestibular compensation was still incomplete.

Interpretation of the Combined Galvanic Test: Findings from Cases with Vestibular Neuronitis

The combined galvanic test (CGT) was developed in our department for simultaneous recording of galvanic eye movement test (GEMT) and galvanic body sway test (GBST). Twelve cases of vestibular neuronitis were studied first with the caloric test, and then with the CGT. The findings of the caloric test corresponded to those of the GEMT, but did not always correspond to those of the GBST. Thus we suggest that the GBST reflects an abnormality in a system different from that reflected by the caloric test and GEMT. It is likely that the caloric response mainly originates from the semicircular canal system. Thus the GEMT may reflect an abnormality in the semicircular canal system, while the GBST reflects an abnormality in the otolithic system. The CGT may thus be a feasible method of differentiating the disorders of the semicircular canal system from those of the otolithic system in the vestibular nervous system.

Neurotological Examination in Harada Disease

Harada disease is an autoimmune disease which is well known as a systemic disorder involving melanocytes in the eye, ear, skin, and meninges.Thirteen patients with Harada disease were examined neurotologically from January 1987 to December 1991. Subjective cochlear and/or vestibular symptoms were noted in 6 of them. In 25 of the 26 ears sensorineural hearing loss, less than 40 dB, was observed. In 12 of the 13 patients, vestibular function tests revealed abnormal findings, which suggested peripheral or central disorder.We studied a representative of 29-year-old male who complained of sudden onset of rotatory vertigo in spite of improvement of ophthalmic symptoms.