Topographic mapping of the primary sensory cortex with intraoperative optical imaging
Martin Oelschlägel (Dresden), Witold H. Polanski (Dresden), Gerald Steiner (Dresden), Edmund Koch (Dresden), Tareq Juratli (Dresden), Ilker Y. Eyüpoglu (Dresden), Stephan B. Sobottka (Dresden)
Intraoperative Optical Imaging (IOI) is a non-invasive imaging technique that is able to visualize functional areas of the cerebral cortex. Therefore, minimal changes in cortical optical properties are detected and evaluated. The physiological origin of the optical signal are changes in cortical hemodynamics that are following neuronal activation. Here, we are demonstrating the potential of the method for a detailed mapping of different body parts and their corresponding areas within primary sensory cortex (PSC).
Measurements were performed on five patients that underwent surgical resection of lesions near the PSC (3 female, 2 male patients, median age 54 years). Different body parts of the patients (arm, hand, leg) were intraoperatively stimulated (tactile/electrical) and IOI data was acquired simultaneously. The localization of the activated regions within IOI was mapped onto anatomical MRI and plausibility was assessed in accordance to expected anatomical localization for the different regions. In two patients, IOI results were additionally compared towards preoperatively acquired fMRI datasets. Therefore, a quantitative approach using the Dice coefficient (DC) for assessment of activation overlap between fMRI and IOI was applied.
The results reveal in all five patients well delineated activated regions using the IOI technique. Furthermore, in all patients a plausible topographic distribution of the activated regions along the PSC were observed and results were in correspondence to electrophysiological measurements. Comparing IOI and fMRI activation, the brain areas that were activated in fMRI showed also in IOI a significant higher level of activity. The DICE coefficient evaluation reveals a good spatial agreement between both modalities for tactile stimulation of the hand (DC = 0.48 for patient #1 respectively DC = 0.61 for patient #2).
IOI is in combination with a suitable stimulation method and paradigm able to identify distinct regions that are representing different body parts on PSC. Therefore, the method can provide valuable information about the localization of different functional areas during surgery.