Functional magnetic resonance imaging and cortical mapping in motor cortex tumor surgery: complementary methods

Area of Science:

• Neurosurgery
• Neuroimaging
• Brain Mapping

Background:

• Preoperative functional brain topography is crucial for surgery near the primary motor cortex (Brodmann area 4).
• Functional magnetic resonance imaging (fMRI) and direct electrocortical stimulation (DES) are common methods, but consensus on their efficacy in reducing operative morbidity is lacking.

Purpose of the Study:

• To compare the topographical accuracy of fMRI and DES in patients with primary motor cortex tumors.
• To analyze the correlation between fMRI and DES results and evaluate the influence of lesion characteristics on mapping outcomes.

Main Methods:

• 30 patients with primary motor cortex tumors underwent preoperative fMRI (BOLD sequences) and intraoperative DES.
• Results were digitally matched using a frameless image-guidance system.
• Correlations, lesion influences, and motor outcomes were analyzed.

Main Results:

• The mean deviation between fMRI and DES was 13.8 mm (range: 7-28 mm), irrespective of lesion histology, size, or position.
• Variability in fMRI analysis thresholds caused topographical inaccuracy.
• fMRI and DES showed considerable differences in mapping motor areas.

Conclusions:

• fMRI and DES are valuable complementary methods for preoperative motor area assessment.
• fMRI assists in estimating operational risk, while DES provides precise intraoperative mapping when tumors are near motor areas.
• These methods aid in optimizing surgical planning and potentially reducing morbidity.