Tractography in Neuronavigation during Intraaxial Brain Tumour Surgery Near Corticospinal Tract

Summary

Objective:
This study was conducted to assess the benefit of integrating corticospinal tract diffusion tractography into neuronavigation during operations for intra-axial brain tumours located close to the corticospinal tract.

Methods:
Diffusion tractography was used, together with subcortical electric stimulation, to locate the corticospinal tract. Motor-evoked potentials elicited by stimulation were recorded. The method was used in five patients with intra-axial brain tumour (astrocytoma gr. II–IV).

Results:
The corticospinal tract was successfully confirmed by electro-stimulation in the approximate location predicted by diffusion tracto­graphy in all patients. Resection of the tumour was terminated when motor-evoked potentials were elicited by a stimulus current of 15 mA (monopolar stimulation, train of four pulses at a frequency of 500 Hz and pulse duration of 400 µs). No patient has since suffered from new permanent neurological deficit.

Conclusion:
Although we remain convinced that, due to the brain shift that occurs during tumour resection, it is not enough to rely solely on the projections of the corticospinal tract in neuronavigation without electrophysiological validation of the tract course, diffusion tractography integrated into neuronavigation appears to be a valuable guide for the identification of the corticospinal tract in the surgical field.

Key words:
neuronavigation – diffusion 
tractography – corticospinal tract – motor evoked potentials – brain 
tumours – diffusion tensor imaging

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