Intraoperative preservation of corticospinal function in the brainstem

Area of Science:

• Neurosurgery
• Neurophysiology
• Neurology

Background:

• The corticospinal tract's vulnerability during brainstem surgery necessitates reliable monitoring methods.
• Large-scale case series on motor-evoked potential (MEP) monitoring in brainstem procedures are lacking.

Purpose of the Study:

• To analyze intraoperative MEP changes during brainstem-related surgeries.
• To evaluate the efficacy of MEP monitoring in preventing permanent new paresis.

Main Methods:

• Myogenic MEPs were monitored using transcranial electrical train stimulation in 70 patients with brainstem lesions (intraparenchymal and extraparenchymal).
• MEP recordings failed in 5 cases; motor outcomes were prospectively documented and correlated with MEP findings.

Main Results:

• Significant MEP changes were observed in 46% of cases.
• Stable or reversibly deteriorating MEPs correlated with unimpaired motor outcomes (71%).
• Irreversible MEP deterioration or loss indicated a 37% risk of transient deficit, and irreversible loss predicted permanent paresis (1.5%).

Conclusions:

• MEP monitoring is a reliable indicator of corticospinal tract function during brainstem surgery, outperforming somatosensory-evoked potentials (SEPs).
• While pronounced MEP changes are needed to predict deficits compared to supratentorial surgery, MEPs can help prevent permanent motor deficits.