Basilar invagination: Surgical results

Abstract

Introduction: Basilar invagination (BI) is a congenital craniocervical junction (CCJ) anomaly represented by a prolapsed spine into the skull-base that can result in severe neurological impairment.

Materials and methods: In this paper, we retrospective evaluate the surgical treatment of 26 patients surgically treated for symptomatic BI. BI was classified according to instability and neural abnormalities findings. Clinical outcome was evaluated using the Nürick grade system.

Results: A total of 26 patients were included in this paper. Their age ranged from 15 to 67 years old (mean 38). Of which, 10 patients were male (38%) and 16 (62%) were female. All patients had some degree of tonsillar herniation, with 25 patients treated with foramen magnum decompression. Nine patients required a craniocervical fixation. Six patients had undergone prior surgery and required a new surgical procedure for progression of neurological symptoms associated with new compression or instability. Most of patients with neurological symptoms secondary to brainstem compression had some improvement during the follow-up. There was mortality in this series, 1 month after surgery, associated with a late removal of the tracheal cannula.

Conclusions: Management of BI requires can provide improvements in neurological outcomes, but requires analysis of the neural and bony anatomy of the CCJ, as well as occult instability. The complexity and heterogeneous presentation requires attention to occult instability on examination and attention to airway problems secondary to concomitant facial malformations.

Keywords: Basilar invagination; congenital craniocervical malformation; surgical treatment.

Figure 1

Surgical decision-making flow chart for patients with basilar invagination

Figure 2

Illustrative case – Patient 9-presented with a severe neurological deterioration 3 years after a posterior fossa decompression for treatment a tonsillar herniation. (a) Sagittal T2 sequence magnetic resonance imaging showing odontoid compression over the brainstem and upper spinal cord. (b and c) Flexion and extension CT scan sagittal reconstructions showing atlanto-axial instability. (d) CT scan 3D reconstruction of a unilateral C1-C2 fusion and unilateral occipito-C2 fusion. (e) Note the C1 lateral mass screws and the fusion of the occipital condyle with C1. (f) Laminar screws at C2. (g) Coronal CT scan showing the left C1 screw in the lateral mass. (h) Intraoperative view of the final construction

Figure 3

Illustrative case – Patient 25-presented with cervical neck pain after moderate walking and signs of cord compression (hyperreflexia, a positive Babinski sign) without gait complaints. (a) Sagittal T2 sequence magnetic resonance imaging showing tonsillar herniation and syrinx in the cervical spinal cord. (b and c) Flexion and extension CT scan sagittal reconstructions showing atlanto-axial stability. The clivus canal angle changed from 110° in flexion through 115° in extension. (d) Sagittal CT scan showing a normal facet joints congruence despite an important clivus hipoplasia. (e and f) Postoperatory sagittal CT scan after posterior fossa decompression and dura mater expansion with fascia graft. The patient reported significant relief of cervical axial pain after 4 months of follow-up