20
Treatment
Table 7. Anatomic Relationships to Consider During Sinus
Surgery to Prevent Complications
Anatomic Findings Description
Maxillary-to-Ethmoid
Ratio
Ratio of the maxillary sinus height to the posterior ethmoid
height (just posterior to the basal lamella) in the coronal
plane
Height of the Lateral
Lamella (Keros
Classification)
e length of the lateral cribriform lamella relative to the
fovea ethmoidalis
• Keros I: 1–3 mm
• Keros II: 3–7 mm
• Keros III: 8–16 mm
Ethmoidal Arteries Determine if the location of the anterior and posterior
ethmoid arteries are traversing through the skull base or
suspended below
Sphenoid Sinus
Pneumatization/
Onodi Cell
Classify the pneumatization pattern of the sphenoid sinus
(conchal, presellar, sellar)
Identify the presence or absence of:
• Onodi cell
• Intersinus septation inserting onto carotid canal
• Dehiscence over the carotid canal or optic nerve
Skull Base Asymmetry/
Bony Dehiscence
Evaluate for any areas of asymmetry (height and thickness)
within the skull base
Examine the continuity of the bone overlying the lamina
papyracea, carotid canal, and optic nerve
Table adapted from May et al. Laryngoscope. 1994;104(9):1080-1083 and
Asaka et al. Am J Rhinol Allerg y. 2012;26(1):61-64.
