Silent sinus syndrome is a spontaneous, asymptomatic collapse of the maxillary sinus and associated with negative sinus pressures. It can cause painless facial asymmetry, diplopia and enophthalmos. Usually the diagnosis is suspected clinically, and it can be confirmed radiologically by characteristic imaging features that include maxillary sinus outlet obstruction, sinus opacification, and sinus volume loss caused by inward retraction of the sinus walls. Treatment is surgical involving making an outlet for mucous drainage from the obstructed sinus, and, in some cases, paired with reconstruction of the orbital floor.