Setsuko Takemori

Visual Suppression Test

Visual suppression of caloric nystagmus was studied in normal adults and in 98 clinical cases in order to justify the application of the procedure as a clinical test. The maximum slow phase velocity during ten seconds in darkness and the slow phase velocity during ten seconds in light were taken from the recordings and measured. The mean values of these slow phase velocities were calculated and the mean slow phase velocity in darkness was assigned a value of 100%. The value which the slow phase velocity in light subtracts from the slow phase velocity in darkness, represents the visual suppression. It was determined that visual suppression of the slow phase velocity of caloric nystagmus was 48 ± 10% in 22 normal adults. This was caused by the visual fixation mechanisms. Cases in which lesions were diagnosed in the cerebellum, such as spinocerebellar degeneration and cerebellitis, showed reduced or abolished visual suppression. The lesion side can be determined by this test. Compensation following unilateral sudden loss of inner ear function can be measured by the visual suppression test.

Clinical Usefulness of Glycerol Vestibular-evoked Myogenic Potentials: Preliminary Report

The detection of intense sound-induced vestibular-evoked myogenic potentials (VEMPs) on the sternocleidomastoid muscle comprises the basis of the saccular function test. In order to evaluate the endolymphatic hydrops (EH) of the saccule of the inner ear, a glycerol VEMP (GVEMP) test was performed in 15 patients with unilateral typical Ménières disease (UMD) and 7 with delayed endolymphatic hydrops (DEH). Using the GVEMP test, 8 of the 15 patients (53%) with UMD were evaluated as being abnormal. In addition, a greater number of patients (67%) were judged to be abnormal when the results of the GVEMP test were combined with those from a glycerol dehydration test, trans-tympanic electrocochleography (ECochG) or furosemide vestibulo-ocular reflex test (FVOR). Four of the 7 patients with DEH (57%) showed abnormal results in the GVEMP test. In particular, in patients with the ipsilateral type of DEH, only the GVEMP test was able to detect the affected side. These findings suggest that the GVEMP test is a new and useful test for EH, and that a test battery comprising the GVEMP test together with one of the other three tests is useful for diagnosing EH of the inner ear.The detection of intense sound-induced vestibular-evoked myogenic potentials (VEMPs) on the sternocleidomastoid muscle comprises the basis of the saccular function test. In order to evaluate the endolymphatic hydrops (EH) of the saccule of the inner ear, a glycerol VEMP (GVEMP) test was performed in 15 patients with unilateral typical Ménières disease (UMD) and 7 with delayed endolymphatic hydrops (DEH). Using the GVEMP test, 8 of the 15 patients (53%) with UMD were evaluated as being abnormal. In addition, a greater number of patients (67%) were judged to be abnormal when the results of the GVEMP test were combined with those from a glycerol dehydration test, trans-tympanic electrocochleography (ECochG) or furosemide vestibulo-ocular reflex test (FVOR). Four of the 7 patients with DEH (57%) showed abnormal results in the GVEMP test. In particular, in patients with the ipsilateral type of DEH, only the GVEMP test was able to detect the affected side. These findings suggest that the GVEMP test is a new and useful test for EH, and that a test battery comprising the GVEMP test together with one of the other three tests is useful for diagnosing EH of the inner ear.

Vestibular training after sudden loss of vestibular functions.

12 cases of unilateral labyrinthectomy, 3 cases of VIIIth nerve section, 22 cases of streptomycin sulfate infusion into the middle ear cavity and 8 cases of bilateral vestibular a-functions underwent vestibular training. Our training is very useful for regaining equilibrium and for evaluating the effects of training on equilibrium by recording the gravity center movements.

Visual Suppression of Vestibular Nystagmus after Cerebellar Lesions

Visual suppression of calorically induced vestibular nystagmus was observed following discrete lesions of various structures in the cerebellum. Unilateral lesions of the flocculus resulted in a complete loss or a significant reduction in visual suppression when the quick phase of the nystagmus was directed to the ipsilateral side of the lesions, and bilateral flocculus lesions caused a bilateral loss of suppression. Nodulus lesions resulted in a loss of suppression, and this loss tended to recover in time. Lesions of the dentate nucleus resulted in a very short term loss of suppression. Extirpation or lesions of the uvula, vermis, para-flocculus, cerebellar cortex, or the fastigial or interpositus nuclei had no observed effect on the visual suppression of vestibular nystagmus. The results of this study suggest that the flocculus and nodulus function as intermediators through which the visual system can modify or alter vestibular reflexes. Also, this phenomenon, that is, loss of visual suppression after the flocculus and nodulus lesion, is very useful to diagnose the localized lesion in the cerebellum.

Cerebellar Contribution to Oculomotor Function

Normal 38 juvenile rhesus monkeys were used to study cerebellar contribution to oculomotor function. (1) Gaze nystagmus was seen only after bilateral flocculus lesions. (2) Spontaneous nystagmus was observed after nodulus, flocculus and cerebellar nuclei lesions. (3) OKN was severely impaired after bilateral flocculus and nodulus lesions. It was slightly impaired after dentate nucleus lesions in a long-term observation. (4) It is a very interesting finding that OKN is severely impaired after destruction of the flocculus and nodulus which have a very important role in the visual fixation.

Influence of Height on the Spatial Orientation and Equilibrium of the Body

The sway of the center of gravity for 30 seconds with a stabilometer was examined in 30 volunteers under 3 visual conditions (eyes open with and without fixation and eyes closed) at heights of 0, 1, and 2 m and under 2 visual conditions (eyes open with fixation and eyes closed) at a height of 10 m 22 cm. Eight of the subjects had acrophobia. The sway worsened at 10 m 22 cm but showed no change at 1 or 2 m. The acrophobic group became clearly worse at 10 m 22 cm. In another group of 12 volunteers, the subjects were guided to the roof with the eyes closed, and sway was measured. Sway was also measured with the eyes uncovered and open and again with the eyes closed. The first measurement with the eyes closed showed worse sway, and the second with the eyes open was better, except in 2 subjects who were acrophobic. (Otolaryngol Head Neck Surg 2000;123:501-4.)

The Similarities of Optokinetic After-Nystagmus to the Vestibular Nystagmus

Optokinetic after-nystagmus (OKAN) was investigated quantitatively in the rhesus monkey to clarify the physiological characteristics. OKAN was always induced after optokinetic nystagmus (OKN) in darkness, was dependent on the preceding OKN and increased up to 135°/sec. OKAN was not influenced by changing the period of OKN. OKAN was very strongly suppressed in light, but the responses were still dependent on the preceding OKN. The responses of OKAN were not changed by the level of illumination during OKN. OKAN showed the response decline in the repetitive testings on one day and in daily tests in all parameters of OKAN. Also, OKAN had a secondary phase. Thus there were many similarities between OKAN and the vestibular nystagmus induced by caloric or rotatory stimulation.

High-resolution MR Imaging of the Inner Ear

The magnetic resonance (MR) images of the temporal bones have been analyzed, these MR images taken with head coils utilizing a 1.5-Tesla magnet whole-body imaging system. The MR images were acquired by means of spin-echo pulse sequences, and the thickness of the sections was 2.5 mm. By this modality, the T2-weighted images could clearly delineate the details of the liquid-containing labyrinthine structures and facial nerve. MR imaging can provide information that is unobtainable from a CT scan in the diagnosis of inner ear disorders, particularly as to whether the membranous labyrinth is filled with the lymph fluid or is fibrosed. This point is one of the greatest advantages of MR imaging over a high-resolution CT scan.

A rare case of acoustic neuroma extending from the cerebellopontine angle to the external auditory canal

A 57-year-old woman presented with tinnitus and complete hearing loss in her right ear and a mild right-sided facial palsy. She was found to have an atypical acoustic neuroma involving the internal auditory canal, labyrinth, and middle ear, extending into both the cerebellopontine angle and the external auditory canal. The tumour was completely removed as a two-stage surgical procedure. The underlying mechanism for the atypical extension is discussed.

Cerebral Control of Eye Movements

87 cases of cerebral lesions were examined to determine which part of the cerebrum is the most important for eye movements and how it controls eye movements. (1) The frontal lobe (frontal eye field) is important for saccades, and (2) the parietal lobe, especially the lower parietal lobe, is very important for visual fixation.