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Biomedical subjects

R Kanayama

Publications and source records attributed to R Kanayama.

At least 19 recordsLinked to original sources
PubMed1996

Clinical significance of step stimulus-induced optokinetic nystagmus.

The optokinetic nystagmus (OKN) test has diagnostic values in that it can detect lesioned sites in patients with infratentorial lesions. The test has so far been performed by using angular acceleration to the final velocity over 100 degrees/s, which is time-consuming and inconvenient for patients. In the present study, we tried to modify and simplify the OKN test used previously to give step stimulus of constant stimulus and compared the results in 20 normal subjects. Slow-phase velocity versus stimulus velocity, and fast phase amplitude and peak velocity versus stimulus velocity of OKN were compared between step-stimulus OKN and linear-stimulus OKN. As a result, each parameter showed significantly higher values in step-stimulus OKN than in linear-stimulus OKN. Averaged slow-phase OKN velocity during the first 5 s is sufficient to calculate OKN velocity, and it requires only short time to perform.

Adult↗
PubMed1995

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

To determine the lesions and the lateralization in patients with Wallenberg's 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 Wallenberg's syndrome.

Angiography↗
PubMed1995

Vertical and torsional VOR in posterior canal occlusion.

The vertical and torsional vestibulo-ocular reflexes (VOR) were investigated in 3 patients with surgical occlusion of the posterior semicircular canal and 1 patient with singular neurectomy, for treatment of refractory paroxysmal positional vertigo. Stimuli comprised sinusoidal oscillation in the coronal ("roll") and sagittal ("pitch") plane as well as in two oblique planes intermediate between pitch in order to stimulate left anterior + right posterior (LARP) and right anterior + left posterior (RALP) canal pairs separately. One case with left side BPPV was investigated pre and post-operatively. Depression of the vertical and torsional VOR gain was seen 1 week postoperatively when the occluded canal was placed in the optimal plane for stimulation at 1 week postoperatively and subsequently gradually recovered. Recordings in other planes suggested that the contralateral posterior canal was also hypofunctioning, a finding which may explain some residual gait unsteadiness in this case. The other 3 cases who were investigated postoperatively all showed a decrease in downward VOR gain in the "on' direction of the operated canal. The data indicate the specificity of the test procedure and underline the prognostic value of comprehensive pre-operative vestibular assessment.

Adult↗
PubMed1995

Perceptual studies in patients with vestibular neurectomy.

Twelve patients undergoing unilateral vestibular neurectomy for the treatment of refractory vertigo were investigated. Vestibular motion perception was assessed using a self-rotational task and "vestibular remembered saccades". Cervical perception was also measured with remembered saccades. The tests were performed pre- and post-operatively to examine changes in vestibular and cervical perception following an acute vestibular lesion, and to monitor the progress of vestibular compensation. These perception tests were carried out in conjunction with a conventional evaluation of the vestibular ocular reflex (VOR), using electro-oculography. The patients' subjective symptoms at each stage of testing were also quantified with questionnaires. Generally, in the vestibular tests, for stimulation to the operated side, responses became strongly hypometric directly after the neurectomy, with a partial recovery during convalescence. In the cervical test, responses were bilaterally reduced immediately after operation. Results from both of the vestibular perception tests were significantly correlated with the VOR assessment of vestibular function. Scores for the patients' subjective symptoms of "vertigo" were only significantly correlated with the vestibular perception tests, and not with the conventional measures of vestibular function. Perceptual measurements afford useful complementary information in the assessment of vestibular patients.

Adult↗
PubMed1994

Visually and memory guided saccades in a case of cerebellar saccadic dysmetria.

Saccades under four specific test conditions (visually guided, visually remembered, vestibular remembered, and cervical remembered) were studied in a 38 year old man with ocular dysmetria due to an angioma of the dorsal cerebellar vermis. The aim of the study was to investigate if the saccadic disorder was specific to certain subsets of saccades elicited by different sensory modalities. The experiments showed that initial saccades were equally hypermetric in all four conditions and that final eye position was normal in all memory guided saccade tests. Eye movements differed after the initial saccade, however. Whereas corrective saccades were seen in most visually guided and visually remembered experiments, postsaccadic centripetal drifts were documented in non-visual (vestibular and cervical) remembered saccades. These results indicate that the cerebellar vermis modulates the amplitude of the initial saccade (pulse size of saccadic innervation) independently of the saccadic task. The finding that post-saccadic drift never occurred when saccades were programmed using visual positional information suggests that the dorsal vermis may participate in the process of pulse step integration of saccades elicited by memorised vestibulo-cervical information.

Adult↗
PubMed1994

Recovery from unilateral vestibular nerve section in human subjects evaluated by physiological, psychological and questionnaire assessments.

Patients undergoing vestibular nerve section for vertigo or acoustic neuroma surgery were compared pre- and post-operatively and during long-term follow-up using a range of tests including: nystagmography, impulsive rotational testing of the vestibulo-ocular reflex (VOR), ability to estimate and reproduce imposed rotational displacements, validated questionnaires rating vertigo, imbalance, autonomic reactivity and somatisation, and clinical and self-assessment scales of overall outcome in terms of symptoms and disability. Correlations were found between rating scale assessments, questionnaire scores and estimates of self-rotation. Neither nystagmography nor VOR tests correlated with the presence or severity of vertigo or imbalance. Post-operatively, vertigo patients reported that they had received significant relief, although they had higher incidences of residual complaints of imbalance and vertigo than patients after acoustic neuroma surgery. Factors impeding rehabilitation in patients with vertigo are discussed.

Adaptation, Physiological↗
PubMed1994

Effects of aging on hearing results in tympanoplasty.

The effects of aging on the preoperative and postoperative hearing results of tympanoplasty were assessed in 642 patients with chronic suppurative otitis media (COM) or cholesteatoma (CHL). Analysis focused on the correlation between hearing results and age for each disease and type of tympanoplasty. Data were evaluated by calculating the regression line, mainly using second order polynomial regression analysis. Averaged air and bone conduction thresholds (PTA) in patients were appreciably poorer in younger patients and increased with age, compared with physiological hearing impairment in old age (presbyacusis). Regression lines for PTA of air and bone conduction in patients and for normal data (air conduction) separated from each other after the age of 30 and hearing impairment gradually accelerated with age. Means of air-borne gap, however, were almost the same in each age group, though hearing thresholds in individual patients were distributed widely. This was more dominant in patients who had undergone type III or IV tympanoplasty than those with type I tympanoplasty, and in patients with COM than with CHL. Labyrinthine function thus appears to be gradually aggravated with age in patients with chronic inflammatory ear disease. Patients with chronic otitis media should be thus recommended to undergo tympanoplasty at an early age.

Adolescent↗
PubMed1994

Slow saccades and quick phases of nystagmus after pontine lesions.

A patient was referred to the university hospital to test eye movements after she had suffered cerebellar hemorrhage one month previously. Examination showed a selective deficit of saccades and quick phases of nystagmus toward the lesion site in the horizontal plane, which was later confirmed pathologically, and which corresponded precisely to the paramedian pontine reticular formation (PPRF). This may suggest that velocities in the quick phase of nystagmus, whether visual or vestibular, and saccades show the same result in PPRF lesion and they share the same neural circuitry in cells located in the PPRF. In the present study, the non-linear saccade velocity-amplitude equation was best-fitted to this patient. Quantitative evaluation of the quick phase may provide a simple and quick reference in saccade slowing.

Brain Diseases↗
PubMed1994

Quantitative assessment of influence of aging on optokinetic nystagmus.

A quantitative assessment of the influence of aging on optokinetic nystagmus (OKN) was investigated using 50 normal adults in ages ranging from 30 to 70 years. In linear stimulus-induced OKN, a statistically significant difference was demonstrated in slow-phase OKN velocity only between the 30-59 year old age group and the 70-79-year-old age group, when OKN stimulus was more than 60 degrees/s. Step stimulus-induced OKN was investigated in the same age groups in order to compare aging effects upon slow-phase OKN velocity. No statistically significant difference was found in slow-phase OKN velocity between younger age groups and the oldest age group. There was no significant difference in fast-phase velocity among the age groups. Thus, step-induced OKN has a wider clinical application than linear stimulus-induced OKN.

Adaptation, Physiological↗
PubMed1994

Computer analysis for routine electronystagmography tests.

A computer program has been developed for on-line analysis of routine electronystagmography (ENG) tests. With this system, data acquisition of eye movements and stimulus signals obtained from ENG are accomplished at a rate of 200 Hz through a 12-bit analog-digital converter. A small spotlight for eye tracking tests is sinusoidally driven by a computer-generated analog signal. Six optokinetic stripes projected onto a screen are also controlled by the computer. Seven spots for saccade tests can be turned on or off based on digital signals produced through a digital output device. There are three types of eye movements in this series: nystagmus, pursuit eye movement and saccadic eye movement. An algorithm for the analysis of different eye movements is described in this paper. Recent significant advances in computer technology make it possible to perform such complicated tasks and to accomplish quantitative assessment of any type of eye movements in routine ENG tests. Consequently, computer analysis provides clues to the location of a disease and is very useful as a diagnostic tool in routine ENG testing.

Artifacts↗
PubMed1994

Effect of aging on smooth pursuit eye movement.

Examination of smooth pursuit eye movement is useful for detecting central nervous system disorders. It is important to take patient's age into consideration when evaluating smooth pursuit eye movement. The purpose of the present study was to clarify the effect of aging on smooth pursuit eye movement. Thirty healthy volunteers (three groups of 10 volunteers, in their fifties, sixties, and seventies and over, respectively) served as subjects, and 10 healthy young volunteers (23 to 33 years old: mean age 26) served as controls. The pursuit target was driven by sinusoidal waveform with various amplitudes and frequencies. Target peak velocities ranged from 12.6 to 94.2 degrees/s. Eye movement signals were recorded d.c. EOG and pursuit gain (ratio of eye peak velocity to target peak velocity) was measured by a computer. Pursuit gain decreased with increasing target frequency and velocity in all age groups. This tendency was more remarkable in the older groups than in the young controls; in particular, it was more frequently seen at a frequency of 0.5 Hz. On the other hand, there was no significant relationship between pursuit gain and the target amplitude. In the group in their seventies and over, pursuit gain was saturated at about 60 degrees/s.

Adult↗
PubMed1994

Detection of peripheral vestibular disorders by the pendular rotation test in cats.

Unilateral vestibular disorders were induced in 3 cats by means of the injection of a small amount of sodium hydroxide into the middle ear, and vestibulo-ocular responses (VOR) to various kinds of pendular stimulation were investigated at 1 week and at 1, 2, 3, 4, and 5 months after the operation. The pendular rotation test was performed at frequencies of 0.025, 0.1, 0.25 and 0.5 Hz, and peak velocities of 50, 100, 150, and 200 degrees/s, and the directional preponderance of the VOR gain (DP%) was measured using a computer. DP% 1 week after the operation was still very high at each frequency and velocity of the stimulation. On the other hand, DP% more than 1 month after the operation had decreased markedly, although it increased with an increase in the velocity of stimulation at all frequencies except at 0.5 Hz, and DP% at a velocity of 200 degrees/s was still high even 5 months later. This suggests that high velocity pendular stimulation should be used to detect unilateral vestibular disorders.

Animals↗
PubMed1994

Ocular abnormalities in amyotrophic lateral sclerosis.

It has long been known that the oculomotor system is not involved in amyotrophic lateral sclerosis (ALS). In early stages. Some authors suggest oculomotor abnormalities in some patients. In the present study, quantitative analysis of ocular movements including smooth pursuit eye movements, optokinetic nystagmus (OKN), visual suppression of vestibular nystagmus (VS), and horizontal saccades were investigated in 9 patients with ALS. These patients were neurologically diagnosed as having ALS in the early stage. The results were as follows: The velocity of saccade was markedly reduced in 4 patients. In addition, there were abnormalities of smooth pursuit (one patient), OKN (one patient) and visual suppression (2 patients). Furthermore, these abnormalities were observed more often in patients with bulbar signs. In conclusion, the results suggest a existence of ocular abnormalities in ALS, even at early stages.

Adult↗
PubMed1994

Quantitative analysis of oblique ocular movements.

In the present study, oblique saccadic eye movements in the orthogonal and oblique directions were investigated in 10 normal subjects, and a computer program was used to accomplish quantitative assessment of oblique eye movements. Eye movements were recorded with direct-current electronystagmography (DC-ENG) and a 12-bit analog to digital converter was used to collect analog data of horizontal and vertical eye position, and stimulus signals at a sampling rate of 200 Hz. The oblique eye movement was displayed two-dimentionally on a high-resolution color graphic terminal for the evaluation of the trace of eye movements, and the peak velocity and the amplitude of the horizontal, vertical and oblique saccades were calculated. It was frequently found that the tracing line in the oblique saccadic eye movement was not completely straight, but loosely curved. The velocity of the vertical component of the oblique saccade was much lower than that of the horizontal component. This suggests that oblique saccades might be made by synchronized but independent vertical and horizontal pulse generators, and the system developed this time might be very useful for investigation of oblique eye movements in both the clinical and physiological field.

Adult↗
PubMed1994

Trapezius osteomyocutaneous flap in reconstructive surgery for mandibular and oral defects.

A scapular-trapezius osteomyocutaneous flap was used for mandibular reconstruction in 4 cases of oral cavity carcinoma after segmental resection of the mandible. In 3 cases, both the flap and bone took well, and the functional and morphological results were satisfactory. In one case, impaired venous return resulted in flap necrosis; a second reconstruction was performed using a rib-latissimus dorsi osteomyocutaneous flap. Functional disturbances of the donor site were minimal and, because the donor site was on the back, the cosmetic result was excellent. This flap is a bone-attached compound flap using the transverse cervical artery and veins as the vascular bundle, and is thought to be useful in the reconstruction of mandibular defects associated with extensive tissue defects of the oral cavity.

Aged↗
PubMed1991

EOG findings in patients with lesions in cerebellar peduncles.

EOG tests were performed in patients with lesions in either the superior or the middle cerebellar peduncle, because these patients showed cerebellar signs and symptoms and were difficult to distinguish from patients with cerebellar lesions symptomatically. EOGs of these patients showed a predominant decrease of pursuit gains and OKN velocity gains toward the lesioned side, whereas the percent reduction of fixation-suppression of caloric nystagmus decreased predominantly toward the side contralateral to the lesioned side, regardless of whether lesions were located either in the superior or the middle cerebellar peduncle. The present EOGs are best interpreted as a corresponding to a deficit of the neuronal events of the flocculus in the monkey and are solely ascribed to lesions in the cerebellar peduncles, because even well-defined cerebellar lesions on one side showed bilateral impairments of these visually induced eye movements.

Cerebellar Diseases↗
PubMed1991

Quantitative analysis of ocular movements in Parkinson's disease.

In the present study, oculomotor abnormalities were investigated in 24 patients with idiopathic Parkinson's disease. Pursuit gain, slow and fast phase velocity of optokinetic nystagmus (OKN), saccade latency, amplitude and velocity, as well as vestibulo-ocular reflex (VOR) gain were quantitatively analyzed. Twenty-one out of 24 patients showed some abnormalities in their ocular movement. A reduction in pursuit gain, impaired OKN and a significantly increased saccade latency were observed in 11 patients. In 12 patients, hypometric saccade was seen, while a decrease in saccade velocity was observed in 10 patients. All patients registered normal values for VOR gain. Only one patient who had impaired smooth pursuit and decreased saccade velocity before treatment with a dopaminergic drug showed a remarkable improvement in these ocular abnormalities after treatment. These results suggest the possibility of dopaminergic control on these ocular movements.

Aged↗