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A pilot study of somatotopic mapping after cortical infarct
S C Cramer1, C I Moore, S P Finklestein
1Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. cramers@u.washington.edu
Background And Purpose:
Animal studies have described remodeling of sensory and motor representational maps after cortical infarct. These changes may contribute to return of function after stroke.
Methods:
Functional MRI was used to compare sensory and motor maps obtained in 35 normal control subjects with results from 2 patients with good recovery 6 months after a cortical stroke.
Results:
During finger tapping in controls, precentral gyrus activation exceeded or matched postcentral gyrus activation in 40 of 42 cases. Patient 1 had a small infarct limited to precentral gyrus. Finger tapping activated only postcentral gyrus, a pattern not seen in any control subject. During tactile stimulation of a finger or hand in controls, postcentral gyrus activation exceeded or matched precentral gyrus activation in 11 of 14 cases. Patient 2 had a small infarct limited to postcentral gyrus and superior parietal lobule. Tactile stimulation of the finger activated only precentral gyrus, a pattern not seen in any control. In both patients, activation during pectoralis contraction was medial to the site activated during finger tapping.
Conclusions:
Results during finger tapping (patient 1) and finger stimulation (patient 2) may reflect amplification of a preserved component of normal sensorimotor function, a shift in the cortical site of finger representation, or both. Cortical map reorganization along the infarct rim may be an important contributor to recovery of motor and sensory function after stroke. Functional MRI is useful for assessing motor and sensory representational maps.