Focal dehiscnece of lamina papyracea

Above axial CT images show focal dehiscence / absence of lamina papyracea in the right orbit with herniation of orbital fat into the right ethmoid sinus. The medial rectus muscle on this side is slightly thickened and irregular although it does not herniate through the bony defect.
This was an incidental finding in the above young patient.

Dehiscence of lamina papyracea may be congenital or acquired( post traumatic/ post-surgical).
There may either be a focal bony defect or inward displacement of the the lamina papyracea.
The defect is usually small with focal herniation of orbital fat and/ medial rectus muscle into the ethmoid bulla.
However, there may be herniation of the optic nerve or the entire  globe.

IMPORTANCE: This defect provides a direct route for sinus surgery instruments which can cause orbital injuries like medial rectus muscle laceration, orbital hematoma, orbital fibrosis, perforation of the orbital wall, damage to globe etc. Hence, it should be highlighted to the otolaryngologist to avoid possible complications during FESS( functional endoscopic sinus surgery).
It may also cause mild diplopia.

REFERENCES:
Hoang JK, Eastwood JD, Tebbit CL, Glastonbury CM. Multiplanar sinus CT:A Systematic Approach to Imaging Before Functional Endoscopic Sinus Surgery. AJR; 194:W527-W536
Radiology picture of the day. Dr Ahmed Haroun.