Dizziness

Dizziness or light headedness is an unpleasant sensation feeling that one may faint.

Prevalence

 * In a 2001 Belgian study, 69.6% of patients meeting the Fukuda criteria and 74.6 % of patients meeting the Holmes criteria, in a cohort of 2073 CFS patients, reported light headedness.

Symptom recognition
The Canadian Consensus Criteria lists light headedness as a symptom of ME/CFS under the section Autonomic Manifestations.

Dizziness is a potential symptom of Long COVID  in the World Health Organization's definition.

Testing
https://www.youtube.com/watch?v=79Iol892EPw Videonystagmography (VNG eng testing) is used for testing inner ear and central motor functions.

There are 4 main parts to a VNG test:

1. Occular Mobility

You will be asked to have your eyes follow objects that jump from place to place, stand still, or move smoothly. The technician will be looking for any slowness or inaccuracies in your ability to follow visual targets. This may indicate a central or neurological problem, or possibly a problem in the pathway connecting the vestibular system to the brain.

2. Optokinetic Nystagmus

2. You will be asked to view a large, continuously moving visual image to see if your eyes can appropriately track these movements. Like the occular mobility tests, the technician will be looking for any slowness or inaccuracies in your ability to follow visual targets. This may indicate a central or neurological problem, or possibly a problem in the pathway connecting the vestibular system to the brain.

https://www.youtube.com/watch?v=_EnAGlTibd0 3. Positional Nystagmus

The technician will move your head and body into various positions to make sure that there are no inappropriate eye movements (nystagmus), when your head is in different positions. This test is looking at your inner ear system and the condition of the endolymph fluid in your semi-circular canals. The technician is verifying that small calcium carbonate particles called otoconia are not suspended in the fluid and causing a disturbance to the flow of the fluid.

4. Caloric Testing

The technician will stimulate both of your inner ears (one at a time) with warm and then cold air. They will be monitoring the movements of your eyes using goggles to make sure that both of your ears can sense this stimulation. This test will confirm that your vestibular system for each ear is working and responding to stimulation. This test in the only test available that can decipher between a unilateral and bilateral loss.