Training in VNG

What is Jerk Nystagmus?

10 mins
09 February 2022

In order to answer this question it is easiest to look at an example. Below you can see a graph which displays horizontal eye movements for a five second period. On the graph is a red and blue line which tells the examiner which eye is being recorded: red = right eye and blue = left eye. You can see on the graph that there appears to be some nystagmus (involuntary eye movement) present. But which direction is it beating?

Well in order to answer this, it is firstly important to know that jerk nystagmus (as displayed above) comprises of two parts: a slow phase which causes the eyes to drift in a certain direction and a fast phase which bring the eyes back to primary position (central position).  It is convention to refer to nystagmus by describing the direction of the fast phase.  In the example we have we can now label the slow phase and the fast based on the duration of the eye movement in each direction.  We can see the eye drifts slowly to the right (upwards on the graph) for a duration of ≈ 1 second and then quickly moves back to centre by moving to the left (downwards on the graph). Therefore by using the naming convention described above we can identify that in this example the fast phase is moving the eye in a leftwards (downwards direction on the graph) and thus we call this left beating nystagmus. In VNG we typically measure in two channels so we can record left beating nystagmus, right beating nystagmus, up beating nystagmus, and down beating  nystagmus for each eye. 



Michael Maslin
After working for several years as an audiologist in the UK, Michael completed his Ph.D. in 2010 at The University of Manchester. The topic was plasticity of the human binaural auditory system. He then completed a 3-year post-doctoral research program that built directly on the underpinning work carried out during his Ph.D. In 2015, Michael joined the Interacoustics Academy, offering training and education in audiological and vestibular diagnostics worldwide. Michael now works for the University of Canterbury in Christchurch, New Zealand, exploring his research interests which include electrophysiological measurement of the central auditory system, and the development of clinical protocols and clinical techniques applied in areas such as paediatric audiology and vestibular assessment and management.

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