title: C2 nerve root on magnetic resonance imaging of occipital neuralgia.
abstract: METHODS
  Review and grade the morphology of the C1-C2 neural foramina, from the MR images of patients who underwent C1-C2 spinal surgery, and determine the relationship with ON.
  
  
  OBJECTIVE
  To evaluate the feasibility of MRI for C1-C2 neural foramen evaluation with a new grading system and to correlate the C1-C2 neural foramen grade with ON.
  
  
  BACKGROUND
  There have been no MRI studies of patients with and without ON in relation to C2 nerve root ganglion findings.
  
  
  METHODS
  Among the registry of 124 patients who underwent C1-C2 spinal surgery between July 2004 and May 2012 in Seoul National University Bundang Hospital, we enrolled 101 patients who had information about ON and a relevant preoperative cervical spine MR image. A total of 202 neural foramina were evaluated with our new C1-C2 neural foramen grading system (grade, 0-3) using consensus reading by 2 experienced radiologists who were blinded to the clinical information. The relationship between the C1-C2 grading system and ON was assessed using a χ test and Fisher exact test. Inter- and intraobserver reliability agreement was assessed using the κ statistic.
  
  
  RESULTS
  All C1-C2 neural foramina were delineated on T2 parasagittal images. Among 202 C1-C2 neural foramina, grade zero was found in 49 foramina (24.3%), grade 1 in 95 (47.0%), grade 2 in 30 (14.9%), and grade 3 in 28 (13.9%). Grade 1 stenosis was most frequently noted. The grade 2 group had the most frequent prevalence of ON (43.3%), followed by grade 3 (35.7%), grade zero (30.6%), and grade 1 (29.5%). However, the relationship between the grade and ON was not statistically significant. Inter- and intraobserver agreements were substantially high.
  
  
  CONCLUSIONS
  C1-C2 neural foramina can be depicted on MR image. However, the relationship between the new grading system for C1-C2 neural foramina and ON was not statistically significant.
  
  
  METHODS
  4.
authors.affiliation: Departments of *Radiology and †Orthopedic Surgery, Seoul National University Bundang Hospital, Gyeonggi-do, Korea; and ‡Department of Radiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Minkyung
authors.initials: M
authors.lastname: Yi
authors.forename: Joon Woo
authors.initials: JW
authors.lastname: Lee
authors.forename: Jin S
authors.initials: JS
authors.lastname: Yeom
authors.forename: Eugene
authors.initials: E
authors.lastname: Joe
authors.forename: Sung Hwan
authors.initials: SH
authors.lastname: Hong
authors.forename: Guen Young
authors.initials: GY
authors.lastname: Lee
authors.forename: Heung Sik
authors.initials: HS
authors.lastname: Kang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000473:pathology; D001270:Cervical Atlas / Q000473:pathology* / Q000601:surgery; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D019547:Neck Pain / Q000473:pathology / Q000601:surgery; D009437:Neuralgia / Q000473:pathology* / Q000601:surgery; D015588:Observer Variation; D009777:Occipital Bone / Q000473:pathology; D009809:Odontoid Process / Q000473:pathology* / Q000601:surgery; D012042:Registries / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013126:Spinal Nerve Roots / Q000473:pathology* / Q000601:surgery; D013130:Spinal Stenosis / Q000473:pathology*; D055815:Young Adult; D021801:Zygapophyseal Joint / Q000473:pathology