Reliability and application variability of a commercially available infrared videonystagmography unit.

PURPOSE: Nystagmus is a condition of involuntary eye movement. The causes for nystagmus may be congenital, idiopathic, or acquired. Considerable debate exists on the therapeutic potential of various surgical techniques. Currently, there are neither standardized protocols nor devices to record quantitative data on patients with clinical nystagmus undergoing various procedures at multiple centers to facilitate randomized prospective clinical trials. METHODS: The authors evaluated the reliability and variability of a commercially available infrared videonystagmography unit by recording eye movement waveforms elicited from normal volunteers (n = 117, 13 patients, 9 trials) by different examiners (A, B, and C). Five movement characteristics were examined, including saccadic latency, velocity and precision, and pursuit gain and velocity. RESULTS: The overall test/retest variability was low, where the median coefficient of variation of the three testers for all five eye movement categories was less than 15%, and less than 10% of the coefficients of variation calculated were more than 20%. However, there was a significant difference in interobserver variability for all outcomes, except saccade latency. CONCLUSIONS: The between-tester analysis was found to have greater variability than the test/retest reliability analysis. Future studies at multiple sites using videonystagmography measurements should aim to have each patient repeatedly tested by the same tester. In anticipation of multicenter, randomized, prospective clinical trials of surgical procedures for nystagmus, standardized protocols for nystagmographic data collection and analysis must be validated both within and among participating centers.

Electronystagmographic analysis of optokinetic and smooth pursuit eye movement disorders in vestibular lesions.

The electronystagmographical analysis of the eye movements is an important method in the evaluation and topical diagnostic procedure of several vestibular lesions. The aim of the study was to compare the electronystagmographical results of the optokinetic and the smooth pursuit eye-movement, and their sensitivity in several vestibular disorders. The patients were divided into five groups: right and left unilateral and bilateral peripheral lesions, central vestibular dysfunction, and normal vestibular function. In patients with normal vestibular system the optokinetic eye movement was pathological in 9.53% of patients, while the smooth pursuit eye movements were pathological in 8.3% of patients with normal vestibular function. In unilateral lesions, 17.42% of the OKNs were pathological, compared with the smooth pursuit test's 20.3% pathological ratio. In the bilateral peripheral vestibular dysfunction the ratio of the pathological eye-movements was 28% equally with to two methods. In central vestibular lesions 22.72% of the patients had abnormal optokinetic eye movements, and the smooth pursuit eye movement was abnormal in 41.6%. Our results show that in the unilateral peripheral vestibular lesions the smooth pursuit eye movement examination seems to be more sensitive than the OKN test, while in central dysfunctions the smooth pursuit eye movement examination is more sensitive than OKN examination.

Air caloric computer system application in monitoring vestibular function changes after cochlear implantation.

INTRODUCTION: The computer-based ENG system's analytical routine refinements are available only in research laboratories. The computer-based system contains a stimulator for saccadic eye-movement and an air caloric stimulator interconnected to the registration program and analysis software. Several authors have reported the preoperative and postoperative vestibular functions in cochlear implant patients. The safe examination of the operated ear and comparison of the preoperative and postoperative average slow phase velocities of the caloric nystagmus is possible using the air caloric computer system. METHODS: The authors have used a computer-based ENG system with caloric air stimulation, which is very useful for examination of the operated ear. The vestibular system of patients with total deafness was examined before and after the cochlear implantation. The results of 60 vestibular examinations of 64 patients are reported. RESULTS: The vestibular function in the operated ear was found unchanged in 20 patients. In 14 patients the vestibular function was worse. In 16 patients the postoperative vestibular responsiveness improved. The detailed data analysis of 10 patients in whom preoperative and postoperative vestibular examination was similar was performed by the authors. The preoperative and postoperative average slow phase velocity values and the relative canal paresis was observed. The values demonstrated that the caloric responsiveness of the operated ear improved in few cases. CONCLUSIONS: The computer-based air caloric system is a useful and safe method in evaluation of the vestibular system changes after ear surgery. The reason of the improvement of vestibular responsiveness is not clear. The results need further investigation to solve the problem of vestibular responsiveness improvement after cochlear implantation.

Predicting fall risks in an elderly population: computer dynamic posturography versus electronystagmography test results.

OBJECTIVES/HYPOTHESIS: Falls are the leading cause of morbidity and mortality for persons aged 65 years and older, with more than 2 million people falling and sustaining serious injury annually. This study compared computer dynamic posturography (CDP) and electronystagmography (ENG) results as predictors of falls. STUDY DESIGN: Retrospective. METHODS: Thirty-three patients over the age of 65 years who presented to a balance disorders and falls prevention clinic were used for this study (22 women and 11 men, with an average age of 78.0 y and a mean fall rate of 3.5 times). All had experienced at least one fall in the year before visiting the clinic and were tested with both CDP and ENG. The CDP results were divided into subcategories (sensory organization testing and limits of stability); ENG results were divided into four categories (ocular motor, rotational chair, positional, and caloric studies). RESULTS: Test findings were classified as normal or abnormal based on age-matched normative data. Of the patients in the study, 27.3% were normal for one type of testing and abnormal for the other. Twenty-six patients (78.8%) had abnormal results on CDP, and 20 individuals (60.6%) showed ENG abnormalities (42.4% for ocular motor, 28.6% for positional, 13.6% for caloric, and 11.2% for rotational chair studies). The limits of stability category was significant in predicting multiple falls. CONCLUSION: For this population, CDP was determined to be a more sensitive test for identifying patients who have fallen, with limits of stability testing the most significant part of the CDP battery; for ENG studies, the best falls indicator was the ocular motor battery.

Toward a standard for electronystagmography.

Although the adoption of a standard is desirable, no person or laboratory will be entirely happy with whatever standard because ENG testing has become so individualized. Hopefully, a standard that will enhance patient care can be implemented without much cost.

[Computer analysis of the ENG signal in real time]. / Analiza komputerowa sygnalu ENG w czasie rzeczywistym.

The theoretical basis of ENG signal analysis in real time was described as well as the equipment and the examination algorithm . 80 ENG examinations were analysed by means of the classical and computer automatic methods. The clinical usefulness of this equipment was presented.

[A nomogram of vestibular pendular stimulation in guinea pigs]. / Nomogram pobudzenia wahadlowego narzadów przedsionkowych u swinki morskiej.

Vestibular pendular test was performed in 20 guinea pigs of various sexes and weights 250-300 g. The total sum of deviations on the right and on the left was 105-164. According to the standard deviation we have accepted the minimal norm 94 and maximal 183. Taking into consideration this norm we have elaborated the nomogram for the quantitative reaction to pendular excitation. There were 6 positions from 0.7 to 1.2 deviations for sec. and total sum from 94 to 183. The results in guinea pigs were in contrast with those in men. The guinea pig vestibular organ is more susceptible for high-rate excitation (17-12 degrees/sec2) and of minor susceptibility in lower rate of acceleration (12-0 degrees/sec2).

Artifacts in electronystagmographic recordings.

Electronystagmography is an important part of the otoneurological investigation. It is mandatory that it is performed in an efficient way, avoiding the many pitfalls and sources of error that the method entails. High quality results crave that the patient is well informed and motivated, relaxed and not under the influence of tranquillizers, hypnotics or alcohol. The technician should be familiar with the equipment, in order to avoid mistakes concerning shielding, time constant and filtering. The most common errors, however, tend to appear in the patient-equipment contact, i.e. the electrodes. A thorough preparation of the skin and high quality Ag/AgCl electrodes and use of electrolyte paste are necessary.

The eye-tracking test.

Quantitative assessment of the electronystagmogram of the eye-tracking test (eye-tracking pattern) was undertaken in 20 normal subjects and 70 patients with vertigo. The abnormal recordings, contrary to the normal, showed, in varying degrees, remarkable irregularties of eye speed. These irregularties appeared in the form of spikes on the electronystagmogram at the time constant of 0.03 second. We measured the height of the spikes using 40 degrees/sec as a unit added the units of spikes appearing during a nine-second period to obtain the total index. Total indices ranged from zero (normal) to 40 + (severely abnormal), and their values showed levels of abnormality in the eye-tracking pattern more accurately than the visual analysis in current use. Standardization of the eye-tracking test, especially of the target velocity, is required for the purpose of comparing abnormalities of eye-tracking patterns recorded in different clinics. In considerations of the results of several good reports on target velocities, we have the following remarks: 1) The maximum velocity of a target which normal subjects can follow without delay of the eye movement is about 20 degrees/sec. 2) When pursuit eye movements of normal subjects are registered with the aid of an electronystagmography, the eye-tracking patterns will remain normal at target velocities of up to 45 degrees/sec. 3) In order to detect abnormalities of pursuit eye movement with the aid of an electronystagmograph, the target velocity should be as fast as possible, but not exceeding 45 degrees/sec. As an instrument for the examination of pursuit eye movements, for reasons outlined in the text, the Umeda circular eye-tracking test apparatus (amplitude 40 degrees, frequency 0.33 Hz, and target veolocity 42 degrees/sec) is ideal. The target amplitude and technical problems in making the apparatus also are discussed.

Frequency responses of office electronystagmography machines.

The high and low frequency characteristics of clinically used electronystagmography (ENG) machines were evaluated using a "dummy patient" calibration source. About one half of the machines yielded tracings that were either seriously divergent from specifications or that otherwise inaccurately reproduced the calibration wave form. Some of these differences do affect the accuracy and quality of clinical recordings.