Functional MRI with motor strip activation.

An adult with  top frontoparietal  glioma, by imaging and MRS parameters  with no neurological deficit so far needs surgery. Functional MRI (fMRI) is ordered to delineate the motor strips. Motor strips on both sides are equally and adequately  delineated , with the lesion anteriorly located in relation to the ipsilateral strip. In addition, supplementary motor activation area in parasagittal location is identified in posterior and medial location to the lesion. Case submitted by Dr MGK Murthy, Mr Sahadev and Abdul Hamid.

Teaching points

·         fMRI is preneurosurgical investigation to localize eloquent cortices controlling language, motor, and memory functions   based on BOLD sequences i.e.-Blood level Oxygen dependent sequence  studying the mapping of oxygen extraction

·         Motor mapping is fairly reliable and easy to perform even for cognitively impaired patients , by simply doing finger tapping

·         Ideal is to perform cued motor movements of fingers/feet/and/or  tongue  depending on the location of the lesion

·         Shows spatial relationship between tumor and  motor activation area, contralateral motor activation and supplementary motor activation

·         It could be decreased on the  side of the lesion depending on the mass effect and vascularity

·         MR report should be specific and brief,  for example- Motor strip on the side of the  lesion is  seen medial/lateral to and anterior/posterior  to the  lesion. Supplementary motor activation is noted /absent. Activity appears decreased / same  as contralateral activity. Preferably film should depict sagittal and axial images.