Systematic Review Feasibility: Prevalence and Underreporting of Onodi Cells
Yes, you can absolutely conduct a systematic review on the prevalence and underreporting of Onodi cells, as existing literature demonstrates significant variability in reported prevalence rates and suggests substantial underrecognition of these anatomically critical structures.
Evidence of Variable Prevalence Rates
The published literature reveals striking inconsistencies in Onodi cell prevalence that justify systematic investigation:
- High prevalence studies report Onodi cells in 65.3% of patients on high-resolution CT, with ethnic variation ranging from 57.0% in African Americans to 83.3% in Asians 1
- Moderate prevalence studies identify Onodi cells in 42.8% of patients using cone-beam CT, with approximately equal distribution between males (42.3%) and females (43.3%) 2
- Lower prevalence studies document Onodi cells in 33.3% of patients, with 98.1% identified on preoperative CT but noted to be "observed more frequently than in previous studies" 3
- Regional variation is demonstrated with 33.3% prevalence in one surgical series and 21.6% in another CT-based analysis 4, 5
Evidence Supporting Underreporting
Multiple lines of evidence suggest systematic underrecognition:
- Imaging modality differences: The variation from 21.6% to 65.3% prevalence across studies suggests that detection rates depend heavily on imaging technique, slice thickness, and observer experience 1, 2, 5
- Surgical versus radiological detection: One study found Onodi cells in 54 patients during endoscopic surgery (33.3%) after identifying them in only 53 patients on preoperative CT, demonstrating near-perfect but not absolute radiological sensitivity 3
- Intraoperative correlation: Only 8 out of 9 HRCT findings were confirmed intraoperatively in one series, suggesting both false positives and potential false negatives depending on surgical technique 4
Clinical Significance Justifying Review
The importance of accurate Onodi cell identification makes this systematic review clinically valuable:
- Surgical risk: Onodi cells have intimate spatial relationships with the optic nerve canal (Type IV bulging observed in 47.1% right side, 41.2% left side) and internal carotid artery, making their identification essential to prevent catastrophic complications during endoscopic sinus surgery 5
- Surgical exposure: In all cases where Onodi cells were present, they limited exposure of the sellar floor during transsphenoidal approaches, requiring removal before complete tumor resection 3
- Anatomical complexity: The posterior-most ethmoid cells lie superior to the sphenoid sinus and can be bilateral (in 23 patients) or unilateral (in 31 patients), with position varying from superior (50%), superolateral (41.9%), to lateral (8.1%) relative to the sphenoid 3, 2
Systematic Review Structure Recommendations
Your systematic review should address:
- Primary outcome: Pooled prevalence estimates across different imaging modalities (HRCT vs. cone-beam CT vs. standard CT) and ethnic populations 1, 2
- Secondary outcome: Discordance rates between preoperative imaging identification and intraoperative findings, quantifying underreporting 3, 4
- Subgroup analyses: Prevalence by ethnicity, gender, imaging technique, observer experience, and anatomical classification systems 1, 2
- Quality assessment: Evaluate studies for imaging protocol standardization, observer training, and surgical confirmation rates 4, 5
Methodological Considerations
- Heterogeneity sources: The 3-fold variation in prevalence (21.6% to 65.3%) suggests substantial methodological heterogeneity that your review should explore through meta-regression 1, 5
- Publication bias: The statement that Onodi cells are "observed more frequently than in previous studies" suggests possible historical underreporting that warrants investigation 3
- Clinical relevance: Focus on studies that correlate radiological findings with surgical outcomes and complication rates to establish the clinical impact of underrecognition 5