When brain cells are dehydrated by increased extracellular fluid osmolarity, it can cause a series of symptoms of central nervous system dysfunction, including drowsiness, muscle twitching, coma, and even death. It is hypertonic dehydration. When the brain volume is significantly reduced due to dehydration, the vascular tone between the skull and cerebral cortex increases, thus leading to localized intracerebral hemorrhage and subarachnoid hemorrhage due to venous rupture. The following is a detailed description of the etiology. When the cellular osmolarity increases, in order to maintain the osmotic balance between intracellular and extracellular fluid, intracellular water extravasates, causing intracellular dehydration brain cell dehydration, then manifests impaired consciousness, irritability, neck tonicity, and in severe cases, coracoacusis, muscle tremor, local or generalized convulsions. It even leaves sequelae. The capillary endothelial cells in brain tissue are closely connected with brain cells, and there is no interstitial space between blood and brain, so when brain cells are dehydrated, water flows directly into the blood circulation. As the brain tissue is densely enclosed in the cranial cavity, brain cell crumpling can lower the cranial pressure, while the heart pumping pressure remains unchanged, which can result in cerebral vasodilation; in severe cases, it can cause cerebral hemorrhage or thrombosis.