Severe brain damage turned him into a vegetable.

严重的脑损伤使他变成了植物人。

《牛津词典》

He suffered severe brain damage after a motorbike accident.

摩托车祸后他的脑部严重受损。

《柯林斯英汉双解大词典》

500 and up -- Severe brain damage and/or death.

500及以上 -严重大脑损伤与/或死亡。

youdao

Otherwise, the pressure in her cranium would have caused severe brain damage, likely killing her.

CNN: Malala: 'I'm feeling better' after skull surgery

Patients in a vegetative state are awake, not in a coma, but have no awareness because of severe brain damage.

BBC: India court rejects Aruna Shanbaug euthanasia plea

But if the affected person has suffered severe brain damage, he or she may sustain permanent disabilities or may never regain consciousness.

CNN: Coma