Association between the fMRI manifestations of activated brain areas and muscle strength in patients with space-occupying lesions in motor cortex

BACKGROUND ： Functional magnetic resonance imaging （fMRI） studies have disclosed the changes of the motor function in the motor cortex of ipsilateral and contralateral hemispheres of tumor, which have special significance for making the surgical planning and most greatly minimizing the postoperative functional damages. OBJECTIVE： To analyze the association between the manifestation characteristics of hand functional area and motor dysfunction using fMRI in patients with space-occupying lesions of tumor in motor cortex. DESIGN ： A case-controlled observation SETTING： Department of Radiology, Second Affiliated Hospital, Shantou University Medical College .PARTICIPANTS： Twenty-three patients （13 males and 10 females） with space-occupying lesions of central sulcus area, aged 21-53 years with a mean age of （47±1） years were selected from the Second Affiliated Hospital of Shantou University Medical College. All the patients were diagnosed by MR scanning as space-occupying lesions of motor area, and pathologically confirmed that the lesions involved central sulcus and central Iobule; Lesions occurred in left and right hemispheres in 13 and 10 cases respectively. The tumor types were astrocytoma （n =8）, metastatic tumours （n =7）, meningiomas （n =5） and oligodendroglioma （n =3）. The muscle strength was normal in 11 cases （grade 5） and obviously decreased in 12 cases （grade 2-3 in 3 cases and grade 4 in 9 cases）; muscle strengths of both upper and lower limbs were decreased in 7 cases, and only that of upper limbs was decreased in 5 cases. Informed consents were obtained from all the subjects. Meanwhile, 9 healthy physical examinees （5 males and 4 females） of 20-56 years old with an average of （34±1） years were taken as controls. All the patients and healthy subjects were right-handed. METHODS： All the enrolled subjects were examined with MR scanning and functional imaging. Twenty cases whose clinical symptoms were mild in the patient group and 9 healthy volunteers adopted simple active finger-tapping movements, and for the 3 cases whose clinical symptoms were severe in the patient group, the simple passive finger-tapping movements were used. The manifestations in the activated brain areas were analyzed in the patients with brain tumor of different muscle strength and the controls. The motor deficit and activation of contralateral primary motor cortex （M1） in simple finger-tapping movements were observed in the patient group. MAIN OUTCOME MEASURES： （1） Brain areas activated by finger-tapping movements in each group： （2） Activated volumes in hemisphere by finger-tapping movements between groups. RESULTS： The contralateral M1 area could not be activated in 1 case in the patient group,, all the other 22 patients and 9 healthy subjects were involved in the analysis of results. （1） In the control group, unilateral finger tapping movement activated the contralateral primary motor cortex （M1）, bilateral SMA and bilateral PMC. The activation volume was the largest in contralateral primary motor cortex （M1）, smaller in the SMA, and the smallest in PMC. The finger tapping movement in healthy subjects could activate contralateral primary motor cortex （M1）, bilateral SMA and bilateral PMC, which had no obvious differences from the manifestations of brain functional area activated by active finger tapping. There was no significant difference in the volume of activated functional areas between right and left hands. In the patient group, the central sulcos around the tumor in the activated M1 area displaced towards dorsal or ventral side, also extended. The distance of displacement in the functional area was determined as compared with the contralateral central sulcus, and the results suggested the M1 displacement, including that there were 10 cases with the M1 displacement larger than 10 mm in the patients with motor deficit, which were obviously more than in those without motor deficit （n =1, P 〈 0.01）, and the activated volume in contralateral M1 area was obvious smaller in the patients with motor deficit than in those without motor deficit （P 〈 0.01）. （2） The M1 activation and changes were observed in contralateral hemisphere in the patient group, and the activated volume was obviously larger than that in the control group （P 〈 0.01）. The activated volumes of M1 and PMC in ipsilateral hemisphere were obviously larger than those in the control group （P 〈 0.05）, but that of SMA had no obvious difference between the two groups （P 〉 0.05）. CONCLUSION： fMRI can be used to observe the activation of the brain motor functional areas of patient with space-occupying lesions in motor area, and evaluate the state of their motor function. The larger the distance of displacement of M1 compressed by tumor, the more obviously the muscle strength decreases in the patients.