The Prevalence of Cervical Foraminal Stenosis on Computed Tomography of a Selected Community-Based Korean Population

The most important finding of this study is that left C5–6 stenosis was most common (24.66%) in the cervical spine on the CT scan, but the more severe grade of stenosis was found in the left C5–6 level (2.97%). The incidences were evaluated from a selected community-based population that had no clinical symptoms of CFS.

Cervical neuromuscular disease is manifested by symptoms in specific neuromuscular regions of the upper limbs, and radiating pain is mostly caused by cervical nerve root compression due to stenosis of the cervical vertebrae.11, 12, 13) In the presence of progressive neurological deterioration, intractable pain, signs of myelopathy, fracture, instability, or ligamentous injury, and bone anomalies or destruction are associated with surgical indications. However, CFS can be asymptomatic.14) To determine the affected level that requires cervical spine surgery, the patients undergo neurological and physical examinations and then both CT and magnetic resonance imaging (MRI); if the results do not match, additional neurophysiological testing is required to determine the affected level. However, if neurological examinations are performed after radiological examinations, it is difficult to rule out the possibility of bias; radiological findings may influence surgeon's decision making.

CT and MRI sometimes do not show stenosis of the cervical vertebra in spite of clinical and neurological symptoms.15) CFS is sometimes referred to as silent cervical spinal canal stenosis, and this compression of the cervical nerve roots is mainly caused by degenerative changes in the spine or secondary intervertebral stenosis caused by disc herniation.11, 12) Silent cervical spinal canal stenosis has been reported by several authors for the risk of neurological damage at the time of injury and prophylactic surgery,16) but there are very few studies on stenosis of the cervical intervertebral disc.1, 17, 18, 19, 20) According to Kuijper et al.,14) false positive nerve root compression is also seen in 45% of cases, mostly in the upper and lower parts of at least one of the clinical abnormalities and even on the opposite side; this asymptomatic nerve root compression is often accompanied by nerve root compression with clinical symptoms, and based on compression findings observed on MRI, patients may be treated unnecessarily. To avoid this, clinicians should take detailed histories of the patient and conduct neurological examinations and interpret MRI results based on these findings. In the case of CFS, it may be more accurate to use CT spine images rather than MRI,21, 22, 23, 24) and we had difficulty gathering and analyzing MRI scans of the general population.

Teresi et al.25) analyzed the MRIs of 100 patients with laryngeal disease and reported symptomatic cervical disc herniation in 57% of patients older than 64 years and in 20% of patients between 45 and 54 years of age. In addition, Boden et al.1) reported major cervical spine abnormalities such as disc herniation, intervertebral stenosis, and stenosis of the cervical intervertebral disc in 28% of patients over age 40 years without symptoms.

In this study, C5–6 was the most common level for CFS, including severe stenosis. Degenerative changes in the cervical spine are known to occur frequently at C5–6,26) and in previous studies, the incidence of CFS was found to be higher at C5–6 than at other sites.2, 27) The causes of CFS in this specific area have not yet been elucidated. However, based on the results of cervical motion studies, it may be attributable to the range of flexion and axial rotation in the C5–6 segment that is broader than that in other regions.28) Further investigation is needed to determine whether these biomechanical properties are related to inducing intervertebral disc stenosis. In addition, C5–6 stenosis was more frequent in the left intervertebral foramina than on the right side, and the stenosis also differed from that in other segments in terms of the higher incidence of diffuse type.

The limitations of this study are as follows. First, this study did not evaluate the correlation between the extent of stenosis and clinical symptoms. However, the aim of this study was to evaluate incidence of CFS in CT among a selected community-based population without clinical symptoms of cervical spine. Second, since the study period was not the entire year but only 3 months of 2016, this study may not be free from selection bias. Third, we could not explain why diffuse type was more common on the left side; further investigation is needed to establish its relationship with the dominant side of the body. Last, the neck CT scan, which was performed for other purposes in various departments, does not accurately show the appearance of the foramen of cervical spine. However, to the best of our knowledge, this is the first study on the extent and shape of the intervertebral foramina at each level of the cervical vertebrae, and it is also important to note that this is the first study that addresses the differences between the left and right sides.

The prevalence of CFS was highest at the C5–6 level: 19.06% for CFS, and 2.29% for severe stenosis (more than 50% nerve root compression). CFS occurred more often on the left side than on the right side (24.66% vs. 13.47%). Focal stenosis was more frequent at C4–5 and diffuse stenosis was more common at C5–6 than at other sites. At C6–7, focal stenosis was more common on the right side and so was diffuse stenosis on the left side. If CT shows normal changes in spite of clinical symptoms of cervical vertebrae stenosis, neurological and neurophysiologic examinations may be important in determining the extent of the lesion.