Headache after cranial trauma due to low cranial pressure causing traction on brain tissue and arteriovenous dilatation is called post-traumatic hypocranial pressure syndrome headache. Headache is the main manifestation of post-traumatic hypocranial pressure syndrome, mostly appearing 1 to 2 hours or 2 to 3 days after the injury, mostly in the frontal and occipital areas, sometimes spreading to the tongue and radiating to the back of the neck. The headache is clearly related to body position, aggravated when sitting and standing, and relieved or disappeared when lying down. Patients should remain in a horizontal position, and drinking plenty of water is useful in relieving this headache. There are three main causes of low cranial pressure due to trauma: 1. Trauma inhibits the function of the choroid plexus. The choroid plexus is located in the cerebral pools of the subarachnoid space, the lateral ventricles, the third ventricle, and the fourth ventricle, and is responsible for the production and recycling of cerebrospinal fluid. The low function of the choroid plexus directly leads to a decrease in cerebrospinal fluid production and a decrease in cranial pressure. 2.The arachnoid membrane is broken under the action of external force, and cerebrospinal fluid flows out from the broken area, resulting in a decrease in the amount of cerebrospinal fluid in the subarachnoid space, which makes it difficult to maintain normal physiological functions. 3.Low arterial blood pressure. The generation of intracranial pressure includes the combined effect of three factors: the pressure generated by cerebrospinal fluid, the pressure generated by brain tissue on the wall of the cranial cavity, which in turn includes two aspects – the hydrostatic pressure of the fluid and the pressure generated by the flow of blood is also reduced, resulting in low cranial pressure.