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Clinical Test Paradigms and Problems: Human Otoprotection Studies
Published in Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm, Advances in Audiology and Hearing Science, 2020
Colleen G. Le Prell, Kathleen C. M. Campbell
During electronystagmography (ENG), electrodes are placed above and below the eye and the measured electrical activity is used to measure the involuntary rapid eye movements, termed nystagmus, that occur in response to various stimuli. There are multiple types of ENG tests. These include a calibration test (assessing ability to follow a light stimulus from 40 to 48 in. away), a gaze test (measurement of nystagmus while eyes are fixed on a target), a pendulum tracking test (the ability to follow a light source as it moves like the pendulum of a clock), an optokinetic test (ability to follow a quickly moving light back and forth across visual field), and positional testing that involves moving the head and body. During head impulse/head thrust testing, the patient/participants head is quickly turned by the examiner, who watches the patient/participants eyes to monitor the “catch-up” nystagmus saccades. ENG testing also includes water caloric testing, during which warm, or cool, water or air is delivered into the ear canal. Videonystagmography (VNG) is similar to ENG but the movements of the eyes are directly measured using high-speed, lightweight video goggles to precisely quantify the velocity of these eye saccades, which increases the accuracy of the testing.
Evaluation of Balance
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
There are many techniques available and they all offer advantages and disadvantages. The two techniques usually available in ENT or audiology departments are electro-oculography (EOG) and video-oculography (VOG). These two techniques are relatively easy to set up, inexpensive, non-invasive and have a range of signal linearity of approximately ±20–30 degrees, capable of coping with the large eye movements encountered during vestibular tests in the dark. The main disadvantages are poor spatial (EOG) and temporal (VOG) resolution, but in the clinical vestibular setting these two techniques are the ones to be recommended (note that EOG and electronystagmography (ENG), are synonymous). An increasingly popular use of VOG is as part of the video head-impulse test (VHIT).
Neurological Investigations
Published in John Greene, Ian Bone, Understanding Neurology a problem-orientated approach, 2007
Although nystagmus may be observed clinically, it is possible to assess nystagmus in a more quantitative manner by means of electronystagmography (ENG). These studies of eye movements are performed in darkness, in order to eliminate the stabilizing effects of visual fixation.
Reconstructing animated eye movements from electrooculography data to aid the diagnosis of vestibular disorders
Published in International Journal of Audiology, 2022
Jacob L. Newman, John S. Phillips, Stephen J. Cox
A further challenge shared with conventional electrode-based electronystagmography is that frequent device calibration is usually required to determine precise eye-movements in degrees. This is due to the variability of the corneo-retinal potential, which is the bioelectrical signal used by both systems as a proxy for eye-movement. Calibration can be performed by the subject performing a calibration task, such as predefined eye movements (e.g. moving the eyes by ± 30 degrees), in order to calculate the number of native device units per degree of eye movement. Alternatively, an average calibration value could be used, with a known margin of error. We did not perform these steps here as it is possible to determine the presence of nystagmus, its duration and beat-direction without prior calibration.
Vestibular assessment and management in adults: South African audiologists’ expressed level of confidence and knowledge explored
Published in Hearing, Balance and Communication, 2020
Katijah Khoza-Shangase, Ben Sebothoma, Tasneem Seedat
Most of the audiologists in the present study (59.5%) indicated that they were not confident in performing vestibular assessments. Similarly, as depicted in Figure 3, a high proportion of audiologists (65.5%) were not confident in performing vestibular management. These findings are consistent with those reported by Callahan [26], where 79% of the participants indicated low comfort levels in performing vestibular assessments. Among the vestibular assessments performed by South African audiologists, 40.6% were not confident in performing electronystagmography (ENG), while 46.9% feel less confident in interpreting ENG results. In contrast, Blohm [27] found that audiologists in the USA were not confident in performing head shake test, and interpreting postural control tests. Gananca et al. argue that ENG is an advanced vestibular assessment technique that requires technical skills that most undergraduate based audiologists may not possess; as is the case with the South African undergraduate programs.
Dealing with Nystagmus
Published in Journal of Binocular Vision and Ocular Motility, 2018
Electronystagmography is not available in all centres but can be very useful for pre- and post-surgical evaluation and can sometimes help with the differential diagnosis. The details are complex, but it is worth remembering that before the typical IN wave of increasing velocity of the slow phase establishes at around age one and a half, movements recordings evolve through earlier phases of wide amplitude triangular movements followed by a pendular waveform.24 Intensity as well as the waveform itself change at different gaze positions. Dell’Osso and Daroff classified the mature IN waveforms into 12 categories and emphasized the importance of foveation periods as the real determinant of vision potential.25 The foveation period occurs at the beginning of the IN slow wave, and foveation is better or worse among different types of waves. Sophisticated software algorithms such as NAFX attempt to provide information solely about the foveation, excluding all irrelevant parts of the nystagmus waves, from the analysis.26