My cousin has anoxic brain injury during MRI now he is on ventilator what is the prognosis of getting well?

Dismal. Anoxic brain injury involves diffuse severe and irreversible injury. This carries a dismal prognosis.
Anoxic brain. Wow - this is bad - how did this happen during an mri. Was he put to sleep? Prognosis really depends on how much injury and how long he was anoxic.