Training in VNG
How Large are Significant Square Wave Jerks?
Description
In the literature, you will read that square wave jerks ≈> 5 degrees can be significant. However, be careful about strict criteria when using your VNG. Using a strict criterion in measuring square wave jerks is analogous to using strict criteria for measuring slow phase of slow phase velocity of nystagmus. I have seen stroke patients and tumour patients with two degrees per second or four degrees per second of spontaneous nystagmus. So, we must be careful about using strict criteria. Still, if you have square wave jerks that measure 5 to 10 degrees per second, then these are clearly pathological. The problem with square wave jerks is that they are unspecific, meaning that they don't tell you what specifically what's happening in the brain, they just tell you that something is going wrong. It is therefore important to look at the presence of square wave jerks in the context of the full neurological assessment.
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