Hello dear friend,
I really feel concerned and pray almighty for all the good ,he can do for you.It appears by the short history given by you that your mother had this acute event of unresponsiveness with frothing from mouth.Most likely causes in this setting can be-
1)toxin-accidental intake of any poisonous substance
2)Seizure- a fit or seizure is usually accompanied with a tonic contraction of
limbs and neck with face along with frothing from mouth
3)stroke-frothing is uncommon in stroke,but still in any case of acute or sudden unresponsiveness,a stroke is always a consideration.
Important investigations in this case are a brain imaging-
computerised tomographic(CT) scan or magnetic resonance imaging(
MRI) scan,to detect a stroke or any other brain pathology.
Electroencephalogram(EEG) to see brain
cortex activity whether there are any ongoing non-convulsive seizures causing unresponsiveness.
In case of
poisoning,if suspected,measures like gastric lavage and diuresis may help(depends on the type of poison).
Also,other investigations like
cerebrospinal fluid analysis may help sometimes(to be decided by the treating physician)
You need to discuss the possibilities with your treating physician and plan accordingly.I hope it helped a bit.