Recovery of Transcranial Motor Evoked Potentials After Atlantoaxial Stabilization for Chiari Formation: Report of 20 Cases.

BACKGROUND

The outcome of neurophysiologic motor evoked potential (MEP) monitoring during surgery for Chiari formation by atlantoaxial fixation and without any bone or dural foramen magnum decompression is analyzed.

METHODS

During the period August 2017 to October 2018, 20 patients having Chiari formation with or without syringomyelia were surgically treated by atlantoaxial fixation. Apart from other forms of monitoring, MEP monitoring formed the basis of study. MEP monitoring was done during various phases of surgery that included monitoring immediately after screw tightening for atlantoaxial fixation.

RESULTS

It was observed that there was positive improvement in MEP in 100% of the patients when measured in the surgical stage immediately after the procedure of screw tightening for atlantoaxial fixation. The improvement in MEP correlated with parallel improvement in neurologic function.

CONCLUSIONS

Improvement in MEP adds credence to the hypothesis that atlantoaxial instability forms the nodal point of pathogenesis of Chiari formation.