Dysfunction of inhibitory-excitatory cortical circuits induces density-dependent facilitation of motor-evoked...

Area of Science:

• Neurosurgery
• Neurophysiology
• Neuroradiology

Background:

• Intraoperative monitoring of motor-evoked potentials (MEPs) is crucial for preventing ischemic complications during aneurysm surgery post-subarachnoid hemorrhage (SAH).
• Reduced MEP amplitude signals corticospinal tract damage, necessitating avoidance during surgical procedures.

Purpose of the Study:

• To evaluate pre-operative MEP amplitude as a control for intraoperative MEPs.
• To assess MEP amplitude's role in indicating cortical excitability and inhibitory-facilitatory circuit pathophysiology post-SAH.
• To determine MEP amplitude's predictive value for perioperative neurological dysfunction.

Main Methods:

• Focused on MEP amplitude measurements immediately before intraoperative clipping or coil embolization.
• Compared MEP amplitude between hemispheres affected by SAH.
• Analyzed the MEP amplitude facilitation ratio against initial CT hematoma density (Hounsfield units).
• Correlated MEP facilitation ratio with short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) values.

Main Results:

• MEP amplitude was significantly higher in the hemisphere with more severe SAH compared to the contralateral side.
• The MEP amplitude facilitation ratio showed a significant linear correlation with initial CT hematoma density (HU).
• MEP facilitation ratio correlated linearly with SICI and ICF abnormalities, particularly with delayed cerebral ischemia.

Conclusions:

• Pre-operative MEP amplitude may serve as an indicator of SAH-related cortical excitability changes.
• Elevated MEP amplitude correlates with initial CT findings and suggests dysfunction in intracortical inhibitory-facilitatory neuronal circuits.
• These findings highlight the potential of pre-operative MEPs in understanding SAH pathophysiology and guiding perioperative management.