A New Simple Technique for Indirect Odontoid Decompression in Patients with Basilar Invagination

Introduction: Basilar invagination (BI) is a result of a defect in the craniovertebral junction (CVJ) development in which the odontoid process is projected through the foramen magnum above the Chamberlain line. It is characterized by alterations in local neuroaxis and might be associated with Chiari malformation, syringomyelia and platybasia. The better way to treat BI has never been defined so there is a myriad of different surgical approaches. The present study describes a very simple surgical technique to indirectly decompress the brain stem just by a posterior route.

Objective: Describe radiological changes in craniometric parameters of the CVJ in patients with (BI) submitted to a modified occipitocervical fixation with indirect anterior decompression.

Methods: Computadorized Tomography (CT) and Magnetic Resonance Imaging (MRI) of the CVJ were performed during the pre-operative and post-operative period and the craniometric parameters (odontoid process across Chamberlain Line and Wackenheim angle) were compared.

Results: Eight patients were enrolled in this study. Mean age was 56,7 years (56–69). In all patients, there was a reduction of the odontoid process insinuation across the Chamberlain line (mean of 3,7 mm) and an enlargement of Wackenheim angle (mean of 17,2°) after analysis of the data.

Conclusion: The technique for indirect decompression of the CVJ in patients with BI, evaluated in the present study, was efficient in changing their craniometric parameters towards physiological position.