Sadao Ogino

Saccadic adaptation in the horizontal and vertical directions in normal subjects

We studied the properties of adaptive gain control in the saccadic system and examined whether the adaptations in the horizontal direction transferred to those in the vertical direction, and vice versa, in 16 normal subjects. Eye movements were measured using search coil system. In the adaptive session, a target moved randomly in amplitude steps of 20 degrees or 30 degrees, with half of the subjects performing in the horizontal direction and the others in the vertical direction. The target eccentricity was changed by a constant percentage (70%) during each saccade aimed at the target. Gains were gradually decreased during the course of 120 repetitions, and then approached approximately 70%. Comparison was made of the accuracy (saccadic amplitude/first target step amplitude) of horizontal and vertical vectors of oblique saccades before and after the adaptation. After the horizontal adaptation, the accuracy of horizontal vectors decreased in the horizontal direction (P<0.05) but not in the vertical direction. After the vertical adaptation, however, the accuracy of horizontal and vertical vectors did not decrease. Our data show that adaptive gain control in the horizontal direction might not transfer to that in the vertical direction, nor vice versa.

A rare case of olfactory neuroblastoma with intracranial extension.

Olfactory neuroblastoma (ONB) is a rare form of head and neck tumor, and further ONB presenting an intracranial extension is extremely rare. Therefore, at the present time there is no established therapeutic standard supported by oncological studies. Our report documents a patient who underwent a craniotomy in combination with transnasal approach for tumor excision, followed by postoperative irradiation. We conclude that the patient shows no evidence of recurrence during the 11-year follow-up involving sinus CT scans and endoscopic examinations.

Aging effects upon smooth pursuit induced by step–ramp stimulation

OBJECTIVE in predictable target movements, pursuit gains are extremely close to 1.0. Under these conditions, aging effects upon pursuit have not been detected. Step-ramp stimuli produced by unpredictable combinations would be favorable procedures to assess the properties of smooth pursuit between young and aged people. METHODS the target was a 0.5 degrees red laser spot. Eye movements of 49 normal subjects (26 younger subjects less than 49 years old and 23 older subjects more than 50 years old) were recorded with infrared reflection oculography and sampled at 250 Hz. Step direction and distance (2, 4, 6, 8 degrees) followed by 10 degrees /s ramp speed movement in the same (onward stimulus) or opposite to the direction (backward stimulus) were programmed in an unpredictable way before each set of ten tests. Both onward and backward stimulation were randomly given for each subject. RESULTS in the onward study, there was a close correlation between retinal slip velocity (RSV) and eye acceleration (EA), which was expressed as a regression curve, being steeper in the younger group. This means that the younger subjects could produce faster velocity and greater acceleration than the aged group (P<0.05). CONCLUSION subtle reduction in visual acuity, visual fields and contrast sensitivity will be one of possible causes, and the degradation of cortical areas crucial for visual processing might be one of possible causes of slowing of pursuit EA.

Wallenberg's syndrome: neurotological classification.

OBJECTIVES Visually induced eye movements were investigated in 26 patients with Wallenbergs syndrome. METHODS Slow-phase optokinetic nystagmus (OKN) velocities, pursuit gains, and percentage fixation suppression (%FS) of caloric nystagmus were recorded by DC electrooculography (EOG), and stored directly onto FM magnetic tape. RESULTS OKN velocities, pursuit gains, and %FS decreased toward the lesion side (group A), whereas OKN velocities and pursuit gains decreased toward the side contralateral to the lesion side. %FS decreased toward the lesion side (group B). MR images in group A showed that lesions were only in and near to the vestibular nuclei, and images in group B showed that lesions extended to the cerebellum. CONCLUSION Visually guided eye movements allow classification of Wallenbergs syndrome into two types, one with brainstem lesions and one with both brainstem and cerebellar lesions. This demonstrates that assessing eye movements is helpful in supplementing MRI data.

Visually guided eye movements in patients with Wallenberg's syndrome.

To determine the lesions and the lateralization in patients with Wallenbergs syndrome, visually-guided eye movements were quantitatively analysed and these findings were compared with a lesioned site as revealed by magnetic resonance imaging (MRI). The 8 patients could be clearly classified into two subgroups based on the functional test of eye movements. In 4 patients, optokinetic nystagmus (OKN), pursuit eye movements and fixation-suppression of caloric nystagmus (FS), utilizing the slow phase velocity as a parameter, were impaired toward the lesioned side in the medulla. In the remaining 4 patients, OKN and pursuit eye movements were impaired toward the side contralateral to the lesion, whereas FS toward the lesioned side, indicating a lesion affecting not only the medulla but also the inferior peduncle and/or the cerebellum. Therefore, the functional visually-guided eye movements can provide a useful test battery with which to detect the lesion site in Wallenbergs syndrome.

Aging Effects upon Pursuit Eye Movements

Quantitative assessment of aging effects upon pursuit eye movements was done in step-ramp stimulus conditions using 32 normal individuals. Eye movements were recorded with infrared reflection oculography. The target was a spot of 0.5 degree red lazar light. The light spot was blanked for 5 ms while the mirror galvanometer moved to a new position. Eye and target position were sampled at 250 Hz and analysed by a personal computer. In onward stimulation in which 2 degrees, 4 degrees, 6 degrees and 8 degrees position steps were followed by fixed ramp speed (10 degrees/s), and also in backward stimulation in which 2 degrees, 4 degrees, 6 degrees step positions were followed by 9 degrees, 17 degrees and 27 degrees/s, eye acceleration increased depending upon increase of retinal slip velocity in the younger group below 49 years. Among the factors effecting aging effects, the cerebrum might be important because visual recognition and eye acceleration are performed in the parietal lobe.

Usefulness of ENG Recordings in Patients with Vertigo As a Screening Test Battery

When patients with vertigo are seen in the clinic, the presence or absence of spontaneous nystagmus is generally tested using Frenzels glasses, and when spontaneous nystagmus is not found, a head-shaking test (HST) is conducted to detect spontaneous nystagmus. We recorded the ENG of these patients with eyes open in total darkness who showed no spontaneous nystagmus under Frenzels glasses. In patients with no nystagmus under Frenzels glasses, clear nystagmus was recognized with a maximum slow-phase velocity of 7.8°/sec and a minimum slow-phase velocity of 3.9°/sec. Therefore, in cases with a maximum slow-phase velocity of less than 7.8°/sec, the possibility that nystagmus may not be recognized with Frenzels glass was indicated. Thus, ENG recording is useful and we use this as an index for treatment and follow-up studies.