Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services for sudden new loss of balance or coordination, especially with:
Facial drooping, one-sided weakness, or numbness
New difficulty speaking or understanding speech
Sudden loss of vision or severe double vision
A sudden, unusually severe headache
Collapse, loss of consciousness, or a seizure
Inability to stand or walk safely
Symptoms markedly different from previous attacks
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Sudden ataxia can be caused by stroke or another urgent condition, even if it resembles a previous episode.
3
Does any of this apply?
Book an appointment
Arrange a routine appointment for repeated unexplained episodes of poor balance, slurred speech, abnormal eye movements, or loss of coordination, especially if relatives have similar symptoms.
If you have a diagnosis, request follow-up when attacks become more frequent, last longer, change in character, or interfere more with daily life.
Increasing falls, new symptoms between attacks, or possible medicine side effects also need review.
The article also says
Do not drive yourself during a severe or unfamiliar episode.
Every sign above is quoted from the sofidex article on Episodic ataxia. If you are not sure, err upward — it is always reasonable to be checked.