In the Keros classification used before endoscopic sinus surgery, a Keros type III configuration implies:

• A Olfactory fossa depth of 1 to 3 mm with a short lateral lamella
• B Olfactory fossa depth of 8 to 16 mm with a long lateral lamella ✓
• C Olfactory fossa depth of 4 to 7 mm with a moderate lateral lamella
• D Agenesis of the cribriform plate with encephalocele

Explanation

Keros classified the depth of the olfactory fossa relative to the ethmoid roof: type I is 1 to 3 mm, type II is 4 to 7 mm, and type III is 8 to 16 mm. In type III the lateral lamella of the cribriform plate is long and thin, exposing it to injury during dissection near the middle turbinate attachment, with consequent CSF leak. This is why preoperative coronal CT assessment of the skull base is mandatory before FESS.

Reference: Scott-Brown's Otorhinolaryngology and Head and Neck Surgery, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.