Can over straining while passing stool leads to nerve or vein in head & neck to break ?after straining during bowel movements feel pain in forehead .

Headaches: Straining for bowel movements can increase intra abdominal and intra cranial pressure. Most of the time there is no threat to brain vessels. Very very rarely if a person has brain artery aneurysm then there is a possibility of rupture and bleeding in side the brain, which can lead to severe sudden headache, coma and death if not taken care quick;y.