Basilar invagination and atlantoaxial dislocation as a complication of severe dystrophic cervical kyphosis correction in neurofibromatosis type 1: Report of a rare case and review of literature

Abstract

Introduction and importance: Neurofibromatosis type 1 (NF1) affects the musculoskeletal system as well as the cervical spine. It is associated with severe, progressive cervical kyphosis. Surgical intervention is the treatment of choice to avoid neurological impairment and malalignment.

Case presentation: We herein report an 11-year-old NF-1 patient with severe cervical kyphosis and intact neurological status. We applied five days of cervical traction followed by surgery utilizing the combined cervical approach (posterior release, anterior corpectomy and reconstruction, and posterior cervicothoracic instrumentation). In one-year follow-up, atlantoaxial dislocation (AAD) and basilar invagination (BI) were detected in neuroimagings. The complication was corrected by adding C1 to the previous construct via unilateral C1 lateral mass screw, contralateral C1 sublaminar hook, unilateral C3 and contralateral C4 sublaminar hook insertion, fixed with contoured rods medial to previous rods. This led to the correction of the AAD and the BI and the patients remained neurologically intact.

Clinical discussion: Severe cervical kyphosis in the setting of NF-1 is progressive and carries a considerable risk of neurologic compromise. Surgical intervention is thus necessary.

Conclusion: The combined approach with complete spinal column reconstruction is the surgical approach of choice. However, complete curve correction to near-normal lordosis carries the risk of proximal junctional failure (PJF).

Keywords: Atlantoaxial dislocation; Basilar invagination; Cervical kyphosis; Neurofibromatosis-1; Proximal junctional failure.

Fig. 1

Preoperational lateral cervical radiography. A: lateral cervicothoracic standing radiography demonstrating severe dysplastic cervical kyphosis; B: lateral cervical radiography in extension demonstrating a kyphotic angle of 34°; C: lateral cervical radiography in flexion demonstrating a kyphotic angle of 86.5°.

Fig. 2

A: Sagittal cervical T2-STIR magnetic resonance imaging (MRI) demonstrating severe cervical kyphosis and dysplastic changes; B: sagittal cervical T2-weighted MRI; C: sagittal 3D cervical computed tomography (CT) scan; D: sagittal cervical CT scan, showing non-ankylosed facet joints and the C2 intervertebral foramen; E: C2–C4 and C2–C7 angles in the sagittal cervical CT scan.

Fig. 3

Three-dimensional view of the vertebral arteries on the computed tomography angiogram demonstrating no challenging abnormalities.

Fig. 4

A: Postoperative anterior-posterior cervicothoracic radiography; B: postoperative lateral cervicothoracic radiography, demonstrating the C2–C7 angle of 14°.

Fig. 5

Sagittal cervical computed tomography scan showing the O-C2 angle of 22°.

Fig. 6

A: Preoperative standing lateral cervical radiography and T1-slope measuring 8°; B: Postoperative midsagittal cervicothoracic spinal computed tomography scan. Cervical lordosis (CL) corrected to −14° and T1-slope to 26°.

Fig. 7

Pre- (A) and post-operative (B) computed tomography scans related to the second surgery: the atlantodental interval (ADI) and ventral C1 arc in Clark zones [32] are compared.

Fig. 8

The final sagittal T2-weighted magnetic resonance imaging (MRI) of the patient 1-year after final surgery demonstrating appropriate alignment of the cervical spine and intact spinal cord.