ENT Nose and PNS abb09c59 Sinusitis is LEAST involved in A Maxillary B Ethmoid C Frontal D Sphenoid High-Yield Explanation (Sphenoid) (181- Dhingra 4th)* Most common sinus involved is - Maxillary* Least common sinus involved in - Sphenoid* Order of sequence - Maxillary >ethmoid > frontal > sphenoid