The role of the Supplementary Motor Area (SMA) in the execution of primary motor activities in brain tumor patients: functional MRI detection of time-resolved differences in the hemodynamic response.
ABSTRACT Interpreting volume of activation maps of brain tumor patients remains difficult using blood oxygenation-level dependent (BOLD) functional magnetic resonance imaging (fMRI) methods. A time-resolved fMRI may offer an informative strategy for investigating the possibility of functional reorganization by elucidating temporal variations in the activation of cortical structures . The aim of this study is to use time-resolved fMRI to investigate potential alterations in the spatially-varying and time-dependent hemodynamic response function within the supplementary motor area (SMA) and primary motor cortex (PMC) in the presence of an adjacent brain tumor, relative to normal control subjects.
Fifteen patients and eight healthy volunteers were recruited. By utilizing a brief motor paradigm that exerts a differential effect on the activation of these structures, latency differences in the hemodynamic responses of such areas may be sensitively investigated. The present study determines the utility of this approach in brain tumor patients by examining the time to peak of the BOLD hemodynamic response within the SMA and PMC.
In patients with glial tumors involving the PMC, the activation of the SMA was delayed and approached that of the PMC with time-to-peak difference between the PMC and SMA averaging 0.2 s. This delay in SMA activation was seen in all patients with glial tumors involving the PMC.
The results suggest that in patients with high-grade brain tumors invading the PMC , the SMA may assume a greater role in the execution of primary motor activities, in addition to its role in executive motor planning.
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ABSTRACT: Well-developed compensatory mechanisms, based on the phenomenon of brain plasticity, exist in patients with neuroepithelial tumors, especially with highly differentiated gliomas (WHO grade II). We studied phenomenon of rearrangement of sensorimotor cortex using functional magnetic resonance imaging (fMRI), and verified relationship between observed changes and results of neurological and neuropsychological assessment. Study group included 20 patients with WHO grade II gliomas located within motor or sensory cortex. fMRI examination, as well as clinical, neurological (Karnofsky performance score [KPS] and Lovett's scale [Lo]), and neuropsychological assessment (Digit Coding Symbol Test and Digit Span Test) were performed pre-operatively and 3 months post-surgery. There were no significant differences in pre- and postoperative performance status of patients. Although statistically insignificant, an increase in frequency of activation of primary and secondary cortical motor centers was observed postoperatively (p>0.05). Prior to surgery, motor centers were characterized by lower values of t-statistics than in postoperative period (p>0.05). In contrast, values of parameters describing the size of examined centers, i.e. mean number of clusters, were lower, but not statistically significant on postoperative examination (p>0.05). Compared to individuals without motor deficit, patients with preoperative Lo3/Lo4 paralysis showed significantly higher mean values of t-statistics in the accessory motor area on postoperative examination (p<0.05). The processes of motor cortex rearrangement seemed to be associated with the pre- and postoperative neurological and neuropsychological status of patients. After contralateral primary motor cortex, accessory motor area was the second most frequently activated center, both pre- and postoperatively.Clinical neurology and neurosurgery 10/2013; 115(12). DOI:10.1016/j.clineuro.2013.09.034 · 1.25 Impact Factor
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ABSTRACT: Functional magnetic resonance (fMR) imaging for neurosurgical planning has become the standard of care in centers where it is available. Although paradigms to measure eloquent cortices are not yet standardized, simple tasks elicit reliable maps for planning neurosurgical procedures. A patient-specific paradigm design will refine the usability of fMR imaging for prognostication and recovery of function. Certain pathologic conditions and technical issues limit the interpretation of fMR imaging maps in clinical use and should be considered carefully. However, fMR imaging for neurosurgical planning continues to provide insights into how the brain works and how it responds to pathologic insults.Magnetic resonance imaging clinics of North America 05/2013; 21(2):269-78. DOI:10.1016/j.mric.2012.12.001 · 0.80 Impact Factor
Article: Functional rearrangement of the primary and secondary motor cortex in patients with primary tumors of the central nervous system located in the region of the central sulcus depending on the histopathological type and the size of tumor: Examination by means of functional magnetic resonance imaging[Show abstract] [Hide abstract]
ABSTRACT: The aim of this study was to analyze the reorganization of the centers of the motor cortex in patients with primary neuroepithelial tumors of the central nervous system (CNS) located in the region of the central sulcus in relation to the histopathological type and the size of tumor, as determined by means of functional magnetic resonance imaging (fMRI). The fMRI was performed prior to the surgical treatment of patients with tumors located in the region of the central sulcus (WHO stage I and II, n=15; WHO stage III and IV, n=25). The analysis included a record of the activity in the areas of the primary motor cortex (M1) and the secondary motor cortex: the premotor cortex (PMA) and the accessory motor area (SMA). The results were correlated with the histopathological type of the tumor and its size expressed in cm(3). The frequency of activation of the motor center was higher in the group of patients who had less aggressive tumors, such as low-grade glioma (LGG), as well as in tumors of lower volume, and this was true both for the hemisphere where the tumor was located and in the contralateral one. Mean values of t-statistics of activation intensity, mean numbers of activated clusters, and their ranges were lower in all analyzed motor areas of LGG tumors. The values of t-statistics and activation areas were higher in the case of small tumors located in ipsilateral centers, and in large tumors located in contralateral centers, aside from the SMA area where the values of t-statistics were equal for both groups. The contralateral SMA area was characterized by the highest stability of all examined centers of secondary motor cortex. No significant association (p>0.05) was observed between the absolute value of the mean registered activity (t-statistics) and the size of examined areas (number of clusters) when the groups were stratified with regards to the analyzed parameters. The presence of a neoplastic lesion, its histopathological type and finally its size modulate the functional reorganization of the motor centers as suggested by the differences in the frequency of the neural center activation in the analyzed groups. Processes of functional rearrangement are more pronounced and more precisely defined in patients with less aggressive and/or smaller tumors. The contralateral accessory area is the most frequently activated center in all analyzed groups irrespective of the grade and size of the tumor.03/2012; 77(1):12-20.