This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
The most common cause of CSF rhinorrhea is? 
Select and explain. 
A. Intracranial infection, B. Accidental trauma, C. Iatrogenic trauma, D. Congenital defects
B: Accidental trauma
Answer: B: Accidental trauma 
Explanation: Trauma to the floor of anterior cranial fossa cause disruption of the arachnoid, tear in dura and fracture of the bone leading to CSF leakage. Trauma to middle cranial fossa cause leakage of CSF into the nose sphenoid. CSF leakage may also occur from posterior cranial fossa due to fracture of clivus or petrous bone. (Ref: Textbook of ent surgeries by P Hazarika D R Nayak pg 361)