Evaluation of Fetal First and Second Cervical Vertebrae: Normal or Abnormal?

Area of Science:

• Fetal imaging
• Orthopedic development
• Medical diagnostics

Background:

• The fetal cervical spine and craniocervical junction exhibit variable appearances.
• Unrecognized variations can lead to misdiagnosis of malalignment at the first and second cervical vertebrae (C1 and C2).

Purpose of the Study:

• To evaluate the variable appearance of the normal fetal cervical spine and craniocervical junction using 3D sonographic volumes.
• To identify potential causes of misdiagnosis in fetal spinal assessment.

Main Methods:

• Acquired 3D sonographic volumes of the fetal cervical spine in 24 fetuses (12 weeks 6 days to 35 weeks 1 day).
• Reviewed volumes using 4D software, labeling vertebrae and evaluating ossification centers for alignment and structure in oblique planes.
• Assessed multiplanar images for perceived anomalies, correlating head rotation with apparent C1-C2 malalignment.

Main Results:

• 16 fetuses had adequate data for assessment.
• All 16 cases showed apparent C1-C2 non-alignment on rotated multiplanar images, mimicking malalignment.
• Head rotation (2°-36°) was observed in all cases and may explain the perceived malalignment; lateral offset ranged from 0.0 to 3.3 mm.

Conclusions:

• Normal C1 and C2 ossification centers can appear malaligned due to physiological offsetting (lateral displacement) of C1 on C2.
• Understanding normal cervical spine development is essential for accurate fetal spinal anatomy assessment.
• This knowledge aids in preventing misdiagnosis of spinal malalignment in fetuses.