Publication

Mapping and Monitoring of the Corticospinal Tract by Direct Brainstem Stimulation

Journal Paper/Review - Jul 14, 2022

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Citation
Yang Y, Neidert M, Velz J, Kälin V, Sarnthein J, Regli L, Bozinov O. Mapping and Monitoring of the Corticospinal Tract by Direct Brainstem Stimulation. Neurosurgery 2022; 91:496-504.
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Type
Journal Paper/Review (English)
Journal
Neurosurgery 2022; 91
Publication Date
Jul 14, 2022
Issn Print
Issn Electronic
1524-4040
Pages
496-504
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Brief description/objective

BACKGROUND
Direct stimulation and diffusion tensor imaging/tractography are established techniques that assist in complex surgery for lesions in the eloquent area of the central nervous system.

OBJECTIVE
To continuously map the corticospinal tract (CST) by direct stimulation during brainstem surgery and to explore the association between direct brainstem stimulation and the shortest distance from the stimulation point to the CST (DS-to-T).

METHODS
We prospectively enrolled 30 consecutive patients for microsurgical resection of lesions within or in proximity to the brainstem between January 2019 and August 2021. Direct stimulation with initially 2 mA was performed for mapping and monitoring the motor fiber tracts. To evaluate CST status and measure DS-to-T, postoperative diffusion tensor imaging/tractography was used. Preoperative and postoperative modified Ranking Scale and motor function were evaluated to assess the clinical outcome.

RESULTS
Intraoperative direct brainstem stimulation was successfully performed in all patients with a total of 909 stimulation points. One patient experienced a temporary neurological deficit postoperatively. Mapping of the CST was achieved in 5 patients. DS-to-T was ≤4 mm when motor-evoked potential responses were positive under 2 mA stimulation and ≤2 mm under 1 mA. Overall sensitivity and specificity for this association were 84.7% and 100%, respectively.

CONCLUSION
This study further supports the paradigm for continuous CST monitoring and mapping through direct brainstem stimulation. The relationship between stimulation intensity and DS-to-T in brainstem surgery could help surgeon's better estimate the safe edge intraoperatively.