We recommend booking assistance as far in advance as possible if you or someone you're traveling with will require assistance with things like getting on and off the train.
You can book assistance, reserve a seat or a wheelchair space and inquire about facilities and accessibility directly with the railway you are travelling with.
SNCF
Accessibility & mobility service in SNCF - France
TGV Lyria
Accessibility & mobility service in TGV Lyria - France and Switzerland