OBJECTIVES: To investigate the reorganization of somatosensory and motor cortex in congenital brain injury. METHODS: We recorded motor evoked potentials (MEPs) following transcranial magnetic stimulation (TMS) and somatosensory evoked potentials (SEPs) in a 41 year old man with severe congenital right hemiparesis but only mild proprioceptive impairment. Brain magnetic resonance imaging showed a large porencephalic cavitation in the left hemisphere mainly involving the frontal and parietal lobes. RESULTS: TMS showed fast-conducting projections from the undamaged primary motor cortex to both hands, whereas MEPs were not elicited from the damaged hemisphere. Left median nerve stimulation evoked normal short-latency SEPs in the contralateral undamaged somatosensory cortex. Right median nerve stimulation did not evoke any SEP in the contralateral damaged hemisphere, but a middle-latency SEP (positive-negative-positive, 39-44-48 ms) in the ipsilateral undamaged hemisphere, with a fronto-central scalp distribution. CONCLUSIONS: Our data show that somatosensory function of the affected arm is preserved, most likely through slow-conducting non-lemniscal connections between the affected arm and ipsilateral non-primary somatosensory cortex. In contrast, motor function was poor despite fast-conducting ipsilateral cortico-motoneuronal output from the primary motor cortex of the undamaged hemisphere to the affected arm. This suggests that different forms of reorganization operate in congenital brain injury and that fast-conducting connections between primary cortex areas and ipsilateral spinal cord are not sufficient for preservation or recovery of function.
OBJECTIVES: To investigate the reorganization of somatosensory and motor cortex in congenital brain injury. METHODS: We recorded motor evoked potentials (MEPs) following transcranial magnetic stimulation (TMS) and somatosensory evoked potentials (SEPs) in a 41 year old man with severe congenital right hemiparesis but only mild proprioceptive impairment. Brain magnetic resonance imaging showed a large porencephalic cavitation in the left hemisphere mainly involving the frontal and parietal lobes. RESULTS: TMS showed fast-conducting projections from the undamaged primary motor cortex to both hands, whereas MEPs were not elicited from the damaged hemisphere. Left median nerve stimulation evoked normal short-latency SEPs in the contralateral undamaged somatosensory cortex. Right median nerve stimulation did not evoke any SEP in the contralateral damaged hemisphere, but a middle-latency SEP (positive-negative-positive, 39-44-48 ms) in the ipsilateral undamaged hemisphere, with a fronto-central scalp distribution. CONCLUSIONS: Our data show that somatosensory function of the affected arm is preserved, most likely through slow-conducting non-lemniscal connections between the affected arm and ipsilateral non-primary somatosensory cortex. In contrast, motor function was poor despite fast-conducting ipsilateral cortico-motoneuronal output from the primary motor cortex of the undamaged hemisphere to the affected arm. This suggests that different forms of reorganization operate in congenital brain injury and that fast-conducting connections between primary cortex areas and ipsilateral spinal cord are not sufficient for preservation or recovery of function.
Authors: Marko Wilke; Martin Staudt; Hendrik Juenger; Wolfgang Grodd; Christoph Braun; Ingeborg Krägeloh-Mann Journal: Hum Brain Mapp Date: 2009-03 Impact factor: 5.038