Identification of the sensorimotor cortex with functional MRI: frequency and actual contribution in a neurosurgical...

We assessed the actual frequency of motor functional MRI (fMRI) in a neurosurgical environment and estimated the extent to which it aided surgeons' identifications of the sensorimotor cortex.

During five consecutive years, an fMRI protocol aimed at generating a selective activation of the hand cortical area was prescribed to 147 patients showing a centrally located space-occupying lesion, which represents 6.7% of all assisted surgical candidates showing an intracranial mass. Three senior neurosurgeons indicated the position of the sensorimotor cortex on two different anatomical displays, reporting confidence ratings for each decision.

The sensorimotor cortex could not be identified in 16.5% of cases using conventional anatomical MRI, and in 15% of cases using 3-dimensional reconstructions. In an additional 12.5% of cases, the neurosurgeons were not confident when they correctly identified the sensorimotor cortex. The tumor distorting effect on central region anatomy significantly contributed to sensorimotor cortex misidentification. fMRI, by contrast, showed a selective activation indicating the position of the sensorimotor cortex in all but 4% of cases.

In our neurosurgical environment, fMRI was prescribed to a selected group of surgical candidates showing a centrally located brain lesion. Compared to conventional anatomical imaging, fMRI does appear to improve the identification of sensorimotor cortex.