C2 nerve root on magnetic resonance imaging of occipital neuralgia.

STUDY DESIGN: 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.

SUMMARY OF BACKGROUND DATA: 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.

CONCLUSION: 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.

LEVEL OF EVIDENCE: 4.