A 21-year-old male was involved in a motorcycle accident and sustained a closed head injury

A 21-year-old male was involved in a motorcycle accident and sustained a closed head injury. He is waking up and interacting with his family and medical team. He complained of thirst that doesn’t seem to go away no matter how much water he drinks. The nurses note that he has had 3500 cc of pale-yellow urine in the last 24 hours. Urine was sent for osmolality which was reported as 122 mOsm/L. A diagnosis of probable neurogenic diabetes insipidus was made.

Question:

What causes diabetes insipidus (DI)?