Evaluating Ossifications of the Nuchal Ligament with Cervical Computed Tomography

The nuchal ligament (NL) extends from the external occipital protuberance and median nuchal line to the spinous process of the 7th cervical vertebrae. In this study, we evaluated the incidence, location level, and size of ossifications of the NL (ONL) in patients who underwent cervical computed tomography (CT) for various reasons.

The present study included 481 patients (187 females and 294 males) who underwent cervical CT from February 2011 to November 2016 due to reasons such as trauma, cervical spondylosis, neck pain, and screening for metastasis. CT was performed using 2- or 8-slice scanners. Archive images of patients on picture archiving and communication system were retrospectively evaluated by two radiologists. The structures in bone density and form detected in NL were evaluated as nuchal ossification. ONL location levels, numbers, and dimensions were determined. The relationship between both sexes and age and the incidence of ONL was investigated.

ONL was detected in 44 patients (9.14%). The mean ages of patients with ONL and without ONL were 62.27±13.92 (23-86) and 41.78±20.76 (4-101) years, respectively. There was a statistically significant relationship between ONL and age (p<0.001). Thirty-six patients had one ONL, seven patients had two, and one patient had three. The most common ONL location was the C5 spinous process level (n=12) followed by the C6 spinous process level (n=8). The longest ONL in craniocaudal direction was 20.9 mm, and the shortest one was 3.1 mm.

ONL is a smooth-contoured ovoid or round bone structure extending parallel to the longitudinal axis that can frequently be observed as one or multiple occurrences with different sizes on cervical CT images.