Inclusion Criteria:  - Clinical diagnosis of postdural puncture headache (PDPH) after elective cesarean section under spinal anesthesia.  Exclusion Criteria:  Hypersensitivity of dexmedetomidine, neostigmine or atropine Overactive thyroid gland Myasthenia gravis Closed angle glaucoma High blood pressure and coronary artery disease. withdrawal of consent