The patient presented with posterior mid-cervical pain following a motor vehicle accident. Radiographs and computed tomography were initially thought to be suspicious of a left C4-C5 facet joint dislocation.
The patient presented with posterior mid-cervical pain following a motor vehicle accident. On physical examination painful limitation of movement was noted. There were no neurological signs in the upper extremities.
Radiographs were initially thought to be suspicious of a left C4-C5 facet joint dislocation (Fig. 1). The absence of effective reduction by halo traction suggested a misdiagnosis, and the radiological findings were reviewed, which led to the correct diagnosis. An axial computed tomography (CT) scan and parasagittal two-dimensional reformatted images (Fig. 2) showed a dorsally displaced articular mass, which was responsible for the first impression of a dislocated facet.
The exact pathogenesis of congenital absence of a cervical spine pedicle is unclear, but it appears to relate to a defect in the chondrification centre of the neural arch in the early cartilaginous stage [1]. The abnormality has been found at all levels from C2 to C7, with C6 being most frequently affected [2].
Oblique radiography is the most typical and useful view [3]. One key to the diagnosis of this normal variant is the fact that the cortices are well preserved and clearly intact, as in this case. There is also a constant triad of findings comprising: (1) absence of the pedicle produces apparent enlargement of the ipsilateral neural foramen; (2) a dysplastic, dorsally displaced ipsilateral articular mass and rotated lamina; and (3) deficiency or absence of the ipsilateral transverse process. Less commonly the articular mass or entire ipsilateral neural arch is absent and occasionally this malformation can affect the two pedicles of the same level [3]. Anomalies such as spina bifida occulta, vertebral body or neural arch fusions, hypoplastic pedicle, atlas abnormalities, cervical spondylolysis in another level and sagittal defect of the vertebral body frequently coexist [3]; occasionally Arnold-Chiari malformation and syringomyelia coexist [1]. Anterolisthesis at the same level has never been described.
In the vast majority of cases reported, this finding has been considered incidental, although the role of mechanical stress as the possible cause of cervical pain has been suggested in 60% of cases. Neural compression is certainly very uncommon, and only in such rare instances is surgical intervention appropriate [4].
The most frequent confusion arises in the context of acute trauma when the dysplastic reversed facet may be mistaken for a unilateral facet dislocation [3]. These patients have accordingly been subjected to halo traction [3], as in this case. Appreciation of the absent pedicle and associated giant foramen on the oblique view is vital to correct the interpretation of plain radiographs. If there is doubt, CT findings are pathognomonic.
The other pitfall is misdiagnosis of the giant foramen as a true foraminal enlargement, including dumbbell neural tumours, neoplastic bone destruction by benign or malignant tumours, bone erosion by a tortuous or aneurysmal vertebral artery, meningocele and dural ectasia.
In cases where myelography has been performed, an enlarged dural sheath containing two nerve roots has often been shown to occupy the foramen [3]. Jones et al. have described the MRI findings and noted an enlarged dural sheath and increased epidural fat in the foramen [5].
In conclusion, awareness of the congenital absence of a cervical spine pedicle with its typical oblique radiography view should facilitate correct diagnosis and avoidance of inappropriate treatment. In addition, where there is believed to be facet malalignment, subluxation or displacement, then it is prudent to perform an MRI if traction is contemplated. This would have confirmed the absence of significant ligamentous and soft tissue trauma associated with the normal variant.
Congenital absence of a cervical spine pedicle
1. This is a 25-year-old male patient who developed mid-level posterior neck pain after a car accident.
2. Routine X-ray (anteroposterior, lateral, and oblique views) shows a clear absence or dysplasia of the left C4-C5 pedicle, resulting in a significantly enlarged ipsilateral intervertebral foramen.
3. There was suspicion of a facet joint malalignment from the imaging, but a subsequent CT scan suggests that the left pedicle absence is congenital rather than due to an acute injury; a reversed protrusion of the residual facet structure is observed, with smooth and intact cortical margins, lacking typical signs of fresh fracture or dislocation.
4. No obvious destruction or erosive changes of the vertebral body or other bony structures are seen, and there is no significant swelling or mass observed in adjacent soft tissues.
5. On coronal and axial CT images, a congenital absence of the left pedicle can be clearly identified, along with certain compensatory structural changes in adjacent vertebrae and neural foramina.
Based on the imaging characteristics and clinical information, the main differential diagnoses or potential diagnoses include:
1. Congenital absence of the cervical pedicle: Imaging can show a pedicle defect and a noticeably enlarged corresponding intervertebral foramen, accompanied by mild facet deformity or malposition while maintaining good cortical integrity. Often discovered incidentally or causing only mild mechanical neck pain.
2. Unilateral cervical facet dislocation: Common after trauma, typically showing facet malalignment, changes in the intervertebral space, or evidence of acute bony or soft tissue damage on X-ray and CT (e.g., facet avulsion, abnormal disc space, or swelling in adjacent tissues).
3. Space-occupying lesion (e.g., schwannoma, “dumbbell”-shaped tumor): Such lesions may present with an enlarged intervertebral foramen or erosive bone changes. Characteristic radiological findings (defined margins, specific signal intensity, or enhancement) often aid in diagnosis. The absence of erosive changes or soft tissue masses in this case argues against this diagnosis.
4. Aneurysm or vascular variant causing bony remodeling: Major vessel anomalies or dilatations can cause pressure-induced bone changes. However, these vascular anomalies or dilatations would typically be evident on imaging. None are seen here, making this diagnosis unlikely.
Considering the patient’s age, trauma mechanism, imaging findings, and clinical presentation, the most likely diagnosis is: Congenital absence of the cervical pedicle (left C4-C5).
Initially, it could be misdiagnosed as an acute unilateral facet dislocation post-trauma, but a thorough CT examination confirmed congenital pedicle deficiency with intact cortical margins and no acute injury signs, indicating a congenital variant.
1. Treatment Strategy:
- Conservative Management: For patients without significant neural compression and with only mild mechanical neck pain, conservative measures include cervical collar support, physical therapy (e.g., heat therapy, physiotherapy), and anti-inflammatory or analgesic medications to alleviate local pain and inflammation.
- Surgical Intervention: Consider surgery only if there are nerve root or spinal cord compression symptoms or if significant instability and severe symptoms arise from the deformity. In this case, without neurological deficits or severe pain, surgery is not recommended.
- Avoid unnecessary cranial traction or over-immobilization: As this is a congenital variant rather than an unstable dislocation, traction is not indicated if there is no associated ligamentous injury. MRI is advised to rule out any underlying soft tissue or ligament injuries.
2. Rehabilitation and Exercise Prescription:
- Early Phase (Marked pain period):
Disclaimer:
This report is based on existing imaging and clinical information for reference only; it cannot replace an in-person consultation or professional medical advice. Specific treatment and rehabilitation plans should be determined according to the patient’s actual condition and under the guidance of qualified medical professionals.
Congenital absence of a cervical spine pedicle
