The dangers of subarachnoid hemorrhage include severe headache and other symptoms, damage to the brain nerves, damage to vision and field of vision, and even life-threatening. 1. Symptoms: Subarachnoid hemorrhage can cause severe headache, accompanied by nausea, vomiting, pallor, cold sweat, dizziness and so on. Some serious patients may also have transient consciousness disorder or even coma, etc. In addition, some patients may have post hemorrhage symptoms. In addition, some patients may have convulsive seizures after bleeding. 2. Damage to cerebral nerves: the tip of basilar artery and aneurysm of posterior cerebral artery can lead to paralysis of the motor nerve on the same side. 3. Damage to visual field: when the amount of hemorrhage is large, it can cause vitreous hemorrhage and damage the vision. When huge aneurysm compresses the optic nerve, it can damage the visual field and cause ipsilateral hemianopsia. 4. Endangering patients’ life: when subarachnoid hemorrhage is serious, it can make patients fall into deep coma, appear to go to the brain to straighten up, endangering patients’ life. If there is any discomfort, it is recommended to consult a doctor in time for diagnosis and treatment.