Operative techniques expert panel discussion
Chiari malformation I: is it a nature’s protective ‘air-bag’?
Understanding that atlantoaxial instability is the cause of Chiari malformation (CM), the author treated 275 patients using atlantoaxial stabilization during the period from January 2010 to December 2017. Surgery was aimed at segmental arthrodesis. Twenty patients had been treated earlier using foramen magnum decompression and duraplasty. According to the extent of their functional capabilities, patients were divided into 5 clinical grades. On the basis of the type of facetal alignment and atlantoaxial instability, the patients were divided into 3 groups. Type I dislocation was anterior atlantoaxial instability wherein the facet of the atlas was dislocated anterior to the facet of the axis. Type II dislocation was posterior atlantoaxial instability wherein the facet of the atlas was dislocated posterior to the facet of the axis. Type III dislocation was the absence of demonstrable facetal malalignment and was labelled as “central” atlantoaxial dislocation. All patients were treated with atlantoaxial plate and screw fixation using techniques described in 1994 and 2004. Foramen magnum decompression or syrinx manipulation was not performed in any patient. Occipital bone and sub axial spinal elements were not included in the fixation construct. On the basis of outcomes in this study, it appears that the pathogenesis of CM, with or without associated basilar invagination and/or syringomyelia, is primarily related to atlantoaxial instability. The data suggest that the surgical treatment in these cases should be directed toward atlantoaxial stabilization and segmental arthrodesis. Except in cases in which there is assimilation of the atlas, inclusion of the occipital bone is neither indicated nor provides optimum stability. Foramen magnum decompression is not necessary and maybe counter-effective in the long run.
Basilar invagination: decompression, fusion or both?
Basilar invagination is a rare craniocervical malformation, which may lead to neurological deficits related to compression of the brainstem and upper cervical cord, as well as instability of the craniocervical junction. 124 patients with basilar invagination were encountered. The clinical courses were documented with a score system for individual neurological symptoms for short-term results after 3 and 12 months. Long-term outcomes were analysed with Kaplan-Meier statistics. Patients with (n = 55) or without (n = 69) ventral compression were distinguished. 56 patients declined an operation, while 68 patients underwent surgery. Surgical management depended on the presence of ventral compression and segmentation anomalies between occiput and C3, signs of instability and presence of caudal cranial nerve dysfunctions. Of 28 patients without ventral compression, 19 underwent a foramen magnum decompression for the associated Chiari I malformation only, while 9 underwent decompression and fusion. Among 40 patients with ventral compression, 29 patients required a decompression and fusion, while 11 were treated by decompression only. Within the first postoperative year neurological scores improved for all symptoms in each patient group. In the long-term, postoperative deteriorations were related exclusively to instabilities either becoming manifest after a foramen magnum decompression in 3, or as a result of hardware failures in 2 patients. The great majority of patients with basilar invagination report postoperative improvements with this management algorithm. Most patients without ventral compression can be managed by foramen magnum decompression alone. The majority of patients with ventral compression can be treated by posterior decompression, realignment and stabilization alone, reserving anterior decompressions for patients with profound, symptomatic brainstem compression. Patients undergoing decompression only require close post-operative follow-up to rule out post-operative C1/2 instabilities
Condylar screw fixation in occipito-cervical fusions
Surgical fixation at the craniovertebral junction is indicated in a number of clinical pathologies. Condylar screw fixation has been recently suggested and validated as a rescue technique and an alternative to the conventional configuration, whenever former surgical bone removal along the supraocciput makes the anchoring of the plate technically difficult. Cadaveric investigations and a limited number of case studies using occipital condyle (C0) fixation have been published so far, in both the adult and paediatric population. The challenging dissection of C0-1, concerns about possible complications, and the overall modest number of occipitocervical fusions required have thus far prevented the acquisition of large surgical series utilizing occipital condylar screws. In this IRB approved study (IRB #13-655B), we present our single-surgeon experience accumulated in 250 cases of occipitocervical fusions using occipital condylar screws, over a period of 8 years. Only two direct complications from condylar screw insertion occurred in this study, and resulted in a complete reversal of the deficit. At short and long follow-up, the subjects of the condylar cohort have demonstrated good levels of postsurgical clinical improvement, solid bone fusions, and a low amount of local discomfort from the hardware.
The symposium is co-organised by The Ann Conroy Trust, in association with Aesculap Academia.
The Ann Conroy Trust is Registered Charity No: 1165808.
We provide Support, Education and Research for patients living with Chiari Malformation, Syringomyelia and associated conditions.