What Is the Most Representative Parameter for Describing the Size of the Atlas? CT Morphometric Analysis of the Atlas with Special Reference to Atlas Hypoplasia

Abstract

The spinal canal diameter (SCD) is one of the most studied factors for the assessment of cervical spinal canal stenosis. The inner anteroposterior diameter (IAP), the SCD, and the cross-sectional area (CSA) of the atlas have been used for the evaluation of the size of the atlas in patients with atlas hypoplasia, a rare form of developmental spinal canal stenosis, however, there is little information on their relationship. The aim of this study was to identify the most useful parameter for depicting the size of the atlas. The CSA, the IAP, and the SCD were measured on computed tomography (CT) images at the C1 level of 213 patients and compared in this retrospective study. These three parameters increased with increasing patient height and weight. There was a strong correlation between IAP and SCD (r = 0.853) or CSA (r = 0.822), while correlation between SCD and CSA (r = 0.695) was weaker than between IAP and CSA. Partial correlation analysis showed that IAP was positively correlated with SCD (r = 0.687) and CSA (r = 0.612) when CSA or SCD were controlled. SCD was negatively correlated with CSA when IAP was controlled (r = −0.21). The IAP can serve as the CSA for the evaluation of the size of the atlas ring, while the SCD does not correlate with the CSA. As the patient height and weight affect the size of the atlas, analysis of the spinal canal at the C1 level should take into account physiologic patient data.

Anatomical Basis and Clinical Significance of Atlas Stenosis: a Systematic Review

“…The average dural sac diameter is 10-12 mm at this level, while the normal sagittal spinal canal diameter ranges from 16-25 mm. A sagittal diameter below 14 mm can cause severe cord compression, and below 10 mm can result in symptoms of myelopathy (10,11,(14)(15)(16). These findings are supported by Yamahata et al (16), who measured the spinal canal diameter in 213 patients and found a mean diameter of 18.6±1.9 mm in males and 17.6 ± 1.6 mm in females.…”

“…A sagittal diameter below 14 mm can cause severe cord compression, and below 10 mm can result in symptoms of myelopathy (10,11,(14)(15)(16). These findings are supported by Yamahata et al (16), who measured the spinal canal diameter in 213 patients and found a mean diameter of 18.6±1.9 mm in males and 17.6 ± 1.6 mm in females. Yamahata et al (16) also discovered that the cross-sectional area (CSA) of C1 (639±75 mm 2 in males and 574±60 mm 2 in females) and the inner anteroposterior diameter (IAP) of C1(30.7±2.0 mm in males and 28.5±1.6 mm in females) could indicate C1 smallness.…”

Classification and Surgical Treatment of Developmental Spinal Canal Stenosis at Atlas Level

“…10 Diagnosis of DSSA is mainly based on cervical CT and MRI results, and clinical symptoms. 8,9,11,12 It was reported that the normal diameter of the midsagittal canal at C1 level ranged from 16 to 25 mm. 8 A diameter of less than 14 mm indicated significant compression of the cervical spinal cord, and a diameter of less than 10 mm would induce myelopathic signs and symptoms.…”

“…Developmental spinal canal stenosis is relatively rare at the upper cervical level than at lower cervical level 10 . Diagnosis of DSSA is mainly based on cervical CT and MRI results, and clinical symptoms 8,9,11,12 . It was reported that the normal diameter of the midsagittal canal at C1 level ranged from 16 to 25 mm 8 .…”

Percutaneous full endoscopic C1 laminectomy for developmental atlantal stenosis with myelopathy: a case report of three cases and review of the literature

“…Yamahata et al (38) measured the internal anterior posterior diameter (IAPD) at the C1 level of 213 cases by CT scan, and the results showed the IAPD was 30.7 mm in males and 28.7 mm in females. Musha et al (8) found the IAPD was 34.4 mm in Japanese females and 37.1 mm in males, and that atlantal stenosis was confirmed when the IAPD less than 29.4 mm in females and 30.5 mm in males.…”