title: Focal opacification of the olfactory recess on sinus CT: just an incidental finding?
abstract: OBJECTIVE
  The CT appearance of the anterior skull base has been investigated but with limited attention directed to the olfactory recess. As defined by opacity abutting the undersurface of the cribriform plate, the prevalence of olfactory recess opacity (ORO) on sinus CT was examined to clarify whether this should raise suspicion for an unsuspected pathologic process.
  
  
  METHODS
  Outpatient sinus CTs were evaluated for ORO in 500 consecutive patients (mean age, 46.9 years; 52.6% women). On a per-side basis (n = 1000), the presence of surgical changes, inflammatory sinus disease, and concha bullosa was determined by 2 neuroradiologists. Logistic regression was used to examine the association of ORO with these variables.
  
  
  RESULTS
  ORO was identified in 59 (11.8%) patients, bilateral in 27 (5.4%), and unilateral in 32 (6.4%). There were 343 of 1000 ethmoid sides that were diseased, and 66 (27.2%) showed ipsilateral ORO. In contrast, only 20 (3.0%) of 657 clear ethmoid sides showed ORO (P < .0001). ORO was significantly (P = .013) more common with previous surgery (18/75; 24.0%) than without (68/925; 7.4%). Ipsilateral concha bullosa was not associated with ORO. Of 32 patients with unilateral ORO, 5 (15.6%) had no ethmoid opacification or previous surgery, and 1 of these patients had an encephalocele causing the ORO. Finally, unilateral ORO was present in only 1 of 122 patients with completely clear sinuses (the encephalocele that was just mentioned).
  
  
  CONCLUSIONS
  ORO is distinctly uncommon without sinonasal inflammation or previous surgery. Isolated unilateral ORO raises suspicion for an underlying neoplasm or cephalocele and warrants further evaluation.
authors.affiliation: Department of Radiology, Mayo Clinic, Scottsdale/Phoenix, AZ 85259-5404, USA. hoxworth.joseph@mayo.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Hoxworth
authors.forename: C M
authors.initials: CM
authors.lastname: Glastonbury
authors.forename: N J
authors.initials: NJ
authors.lastname: Fischbein
authors.forename: W P
authors.initials: WP
authors.lastname: Dillon
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002140:California / Q000453:epidemiology; D005005:Ethmoid Sinus / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D009300:Nasal Septum / Q000000981:diagnostic imaging*; D010255:Paranasal Sinus Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D015995:Prevalence; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*