Exercise-associated hyponatremia cells in one area begin to increase in size, swelling occurs in the affected area. Swelling is commonly observed in hands, legs, and feet. Sodium is also important in regulating the amount of water that passes through the blood-brain barrier. Decreased sodium blood levels result in increased permeability of water across the blood-brain barrier. This increased influx of water causes brain swelling which leads to severe neurological symptoms. EAH is categorized by having a blood serum or plasma sodium level below normal, which is less than 135 mmol/l. Asymptomatic EAH is not normally detected unless the athlete has had a
Cerebral edema (ECF) in the brain is slightly lower than that of plasma. Plasma can be diluted by several mechanisms, including excessive water intake (or hyponatremia), syndrome of inappropriate antidiuretic hormone secretion (SIADH), hemodialysis, or rapid reduction of blood glucose in hyperosmolar hyperglycemic state (HHS), formerly known as hyperosmolar non-ketotic acidosis (HONK). Plasma dilution decreases serum osmolality, resulting in a higher osmolality in the brain compared to the serum. This creates an abnormal pressure gradient and movement of water into the brain, which can cause progressive cerebral edema, resulting in a spectrum of signs and symptoms from headache and ataxia to seizures