This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and PNS, Subject name: ENT
"Tear drop" sign on X-ray PNS is seen in 
Select and explain. 
A. Blow out fracture of the floor of the orbit, B. Comminuted fracture of the maxilla, C. Fracture of the nasal bone, D. Fracture of the mandible
A: Blow out fracture of the floor of the orbit
Answer: A: Blow out fracture of the floor of the orbit 
Explanation: Ans. a (Blow out fracture of the floor of the orbit) (Ref. Grainger Diagnostic Rad 4th/2527; Ref . Q. 159. Of MH-2207)BLOW-OUT FRACTURE is caused by fracturing of the orbital walls with herniation of orbital contents and subsequent tethering of the globe, resulting in pain and diplopia. It usually involves the orbital floor with 'trap-door deformity' on skull AP view or characteristic "Tear drop" sign on X-ray PNS.Also Know:# Tripod Fracture: zygomaticomaxillary fracture# "pyramidal" fracture = Le Fort II fracture (fracture medial orbital and lateral maxillary walls).# Bare orbit sign: Neurofibromatosis# Coke-bottle sign: thyroid ophthalmopathy# "Mushroom-shaped" posterior segment mass: choroidal melanoma# Calcification is pathognomonic of: Retinoblastoma# Most common intraorbital tumor in adults: Cavernous hemangioma.