Systematic Reviews on Onodi Cells and Optic Nerve Dehiscence
There are no dedicated systematic reviews specifically examining Onodi cells and underreporting associated with optic nerve dehiscence, but the existing literature consistently demonstrates that Onodi cells create significant risk for optic nerve injury during endoscopic sinus surgery, with prevalence rates substantially higher than historically reported and frequent underdetection on preoperative imaging. 1, 2, 3
Evidence of Underreporting and Detection Challenges
Prevalence Discrepancies Suggest Underreporting
The prevalence of Onodi cells is significantly higher than previously documented, with recent studies identifying them in 39.8% of cases on CT examination and 33.3% of cases during endoscopic transsphenoidal surgery, compared to lower historical estimates 2, 3
Direct contact between the most posterior ethmoid cell and the optic nerve occurs in 55.6% of cases, with optic nerve canal bulging into the sphenoethmoid cell present in 25% of cases 2
Preoperative CT imaging successfully identified 98.1% of Onodi cells that were subsequently confirmed during surgery, indicating that proper imaging technique can minimize underreporting 3
Imaging Technique Impacts Detection Rates
Single-plane CT evaluation leads to systematic underdetection of Onodi cells, as axial views alone miss critical anatomic relationships 2
Three-plane reconstruction (axial, coronal, and sagittal) is essential to avoid both missing and over-detecting Onodi cells, with axial and sagittal planes being most reliable for accurate identification 2
CT scanning provides the best preoperative information for endoscopic surgery with excellent delineation of sphenoethmoidal (Onodi) air cells, which increase the risk of injury to the optic nerves or carotid arteries 1
Clinical Significance and Risk of Optic Nerve Injury
Anatomic Relationship Creates Surgical Risk
Onodi cells pneumatize superiorly and laterally to the sphenoid sinus and maintain intimate spatial relationship with the optic nerve, internal carotid artery, and sellar floor 3, 4
In all surgical cases with Onodi cells, these cells limited exposure of the sellar floor and required removal before complete tumor resection could be achieved during endoscopic transsphenoidal approaches 3
Previously unreported anatomic variations continue to emerge, including the "central Onodi cell" where a posterior ethmoid cell lies superior to the sphenoid sinus in a midline position with at least one optic canal bulge 4
Documented Cases of Optic Neuropathy
Inflammatory lesions within Onodi cells can cause compressive optic neuropathy, as demonstrated by cases of mucosal thickening, polyps, and mucoceles producing progressive vision loss 5, 6
Even isolated or small lesions in Onodi cells may cause bilateral visual disturbance due to the confined anatomic space and proximity to both optic nerves 6
Bone defects along the optic nerve canal within Onodi cells have been identified during surgical exploration, indicating natural dehiscence that increases vulnerability to injury 6
Critical Pitfalls in Clinical Practice
Preoperative Imaging Requirements
Failure to evaluate all three CT planes (axial, coronal, sagittal) systematically leads to missed Onodi cells and increases surgical risk 2
Ophthalmologists and surgeons must specifically assess for Onodi cell pathologies when evaluating patients with unexplained visual symptoms and sinus disease 5
Surgical Planning Implications
Computer navigation systems for image-guided surgery require accurate preoperative identification of Onodi cells to provide real-time information about instrument location relative to the optic nerve 1
The bulging of the optic nerve into the ethmoid cell wall is well visualized endoscopically, but preoperative CT identification remains essential for surgical planning 2
Gap in Systematic Review Literature
While individual case reports 5, 6, case series 3, and prevalence studies 2 document the clinical significance of Onodi cells and their relationship to optic nerve injury, no formal systematic review has synthesized this evidence to quantify the true prevalence of optic nerve dehiscence within Onodi cells or the rate of underreporting across different imaging modalities and clinical settings. The existing guideline literature acknowledges Onodi cells as anatomic variants that increase surgical risk 1 but does not provide systematic analysis of dehiscence patterns or underreporting rates.