i have had the tsunami spasms that you describe,thankfully not too ofton.
i think they are the myoclonus but more violent,like myoclonic epilepsy.
had a couple of real nasty ones,one that caused my body/back to suddenly snap and double in two.
i dared not move as i thought it had broken my back.
another time i was sat at the end of the sofa,just put my cup of tea on the table.
i was suddenly thrown back accross the sofa.
they happen so fast and without warning but i am positive i can hear a snapping noise in the back of my head when they happen.
i don,t think baclofen can help,you may need a anti-spasmodic drug that is used to treat sezuires.
mine are not ofton so i declined drugs for it,it did,nt want to get into taking serious epilepsy drugs.
i hope you find something that works.
baclofen pumps are very good if you can not tolerate the tablets or need larger doses.
take good care.
caroline