title: Retropharyngeal lymph nodes in children: a common imaging finding and potential source of misinterpretation.
abstract: OBJECTIVE
  The retropharyngeal lymph nodes are the least well-described portion of the Waldeyer ring. Originally described as occurring in medial and lateral groups, reports have described only the presence of lateral nodes in children. We have seen cases of MRI sleep studies in children with obstructive sleep apnea (OSA) in which lateral and medial retropharyngeal lymph nodes are present and have been misinterpreted. Our purpose is to describe the frequency and appearance of retropharyngeal lymph nodes in children with and without OSA.
  
  
  METHODS
  Axial and sagittal T2-weighted MRI scans were reviewed in 150 children with OSA and 150 control subjects without OSA, who underwent imaging for other indications. The presence, size, and location of the retropharyngeal lymph nodes were evaluated. Retropharyngeal lymph nodes were evaluated for frequency of medial nodes, frequency of lateral nodes, size as indicated by the anterior-to-posterior diameter, laterality (bilateral or unilateral), and superior-to-inferior location compared with the cervical vertebral body level. Analyses were performed using the chi-square or Fisher's exact test (for categorical data) and generalized linear model or two-sample Wilcoxon's Mann-Whitney test (for continuous data).
  
  
  RESULTS
  Lateral retropharyngeal lymph nodes were common in both children with OSA (137/150 [91.3%]) and children without OSA (146/150 [97.3%]). Medial retropharyngeal lymph nodes occurred not uncommonly in both children with OSA (32/150 [21.3%]) and those without OSA (26/150 [17.3%]). Lateral retropharyngeal lymph nodes were more commonly bilateral (95% CI, 88.4-97.4%; p < 0.0001) and located at the skull base (C1) or C1-C2 level (99%; p < 0.0001). Medial retropharyngeal lymph nodes were more commonly unilateral (95% CI, 71.9-84.6%; p < 0.0004) and located at the C2-C3 level (95% CI, 78.13-84.62%; p < 0.0001). There were no statistically significant differences in the proportion of medial or lateral retropharyngeal lymph nodes in the OSA group compared with the control group.
  
  
  CONCLUSIONS
  Retropharyngeal lymph nodes are seen commonly in children in both lateral (95% CI, 91.3-97.3%) and medial (95% CI, 17.3-21.3%) locations. Media nodes are present more frequently than previously described. Such nodes occur almost equally frequently in populations with and without OSA. Retropharyngeal lymph nodes should be considered normal in children and not be interpreted as abnormal or misdiagnosed.
authors.affiliation: Department of Radiology, Cincinnati Children's Hospital Medical Center, MLC 5031, 3333 Burnet Ave, Cincinnati, OH 45229-3039, USA.
authors.forename: Norma S
authors.initials: NS
authors.lastname: Costa
authors.forename: Shelia R
authors.initials: SR
authors.lastname: Salisbury
authors.forename: Lane F
authors.initials: LF
authors.lastname: Donnelly
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D016014:Linear Models; D008198:Lymph Nodes / Q000033:anatomy & histology / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010614:Pharynx; D012016:Reference Values; D020181:Sleep Apnea, Obstructive / Q000473:pathology*; D018709:Statistics, Nonparametric