AVP and inappropriate ADH syndrome: Harrigan (15) considered that, within 2 weeks of brain injury, hyponatremia is often caused by CSWS, with an incidence rate higher than that of SIADH and the reason is that, at the onset of hyponatremia, a large amount of sodium is discharged from urine, resulting in hypovolemia and high urinary sodium, while the ADH levels in the blood are normal.