Central Motor Reorganization in Cerebral Palsy Patients with Bilateral Cerebral Lesions

Abstract

Transcranial magnetic stimulation (TMS) has been used to describe cortical plasticity after unilateral cerebral lesions. The objective of this study was to find out whether cortical plasticity occurs after bilateral cerebral lesions. We investigated central motor reorganization for the arm and leg muscles in cerebral palsy (CP) patients with bilateral cerebral lesions using TMS. Seventeen patients (12 with spastic diplegia, 1 with spastic hemiplegia, and 4 with athetoid CP) and 10 normal subjects, were studied. On CT/MRI, bilateral periventricular leukomalacia was observed in all spastic patients with preterm birth. In two normal subjects, motor responses were induced in the ipsilateral tibialis anterior, but no responses were induced in any normal subject in the ipsilateral abductor pollicis brevis (APB) or biceps brachii (BB). Ipsilateral responses were more common among CP patients, especially in TMS of the less damaged hemisphere in patients with marked asymmetries in brain damage: in 3 abductor pollicis brevis, in 6 BBs, and in 15 tibialis anteriors. The cortical mapping of the sites of highest excitability demonstrated that the abductor pollicis brevis and BB sites in CP patients were nearly identical to those of the normal subjects. In patients with spastic CP born prematurely, a significant lateral shift was found for the excitability sites for the tibialis anterior. No similar lateral shift was observed in the other CP patients. These findings suggest that ipsilateral motor pathways are reinforced in both spastic and athetoid CP patients, and that a lateral shift of the motor cortical area for the leg muscle may occur in spastic CP patients with preterm birth.

Transcranial magnetic stimulation in children

“…By stimulating at a number of different scalp positions (using a stimulus intensity close to MEP threshold) and measuring the amplitude of the MEP at each site, it is possible to assess the location of the optimal position for stimulation and the center-of-gravity, which defines the mean position of the map (Abbruzzese and Trompetto, 2002;Chen, 2000). Only one study has examined cortical maps in a small group of typically developing children, 6 to 14 years of age, as a comparison for children with cerebral palsy (Maegaki et al, 1999). Cortical representation sites for the tibialis anterior, biceps brachialis, and abductor pollicis brevis muscle were identified between 1 to 4 cm, 4 to 6 cm, and 5 to 8 cm lateral to the cranial vertex, respectively; the authors did not report the optimal stimulation site or the center of gravity.…”

“…Cortical maps of the lower extremity muscles are laterally displaced in children born prematurely who have PVL and spastic diplegia. In contrast, maps of lower extremity muscles are normally placed in individuals born at term who have spastic diplegia and in those with a bilateral dyskinetic form cerebral palsy, neither of which are associated with abnormalities resulting from ischemia of central white matter (Maegaki et al, 1999).…”

Transpontine Connection Fibers between Corticospinal Tracts in Hemiparetic Patients with Intracerebral Hemorrhage

“…Furthermore, TMS studies have reported changes in motor pathways at the subcortical level, and a number of these studies focused on the ipsilateral motor pathway from the unaffected motor cortex to affected extremities, through the transcallosal pathway, the anterior CST, and pathways synapsed in the brainstem, such as the reticular formation [1,2,3,4,5,6,21,22,23,24]. However, the TMS is limited by an inability to visualize neural tracts.…”

“…Many studies have been conducted on neural pathway changes at the subcortical level following brain injury [1,2,3,4,5,6,7,21,22,23,24]. Furthermore, TMS studies have reported changes in motor pathways at the subcortical level, and a number of these studies focused on the ipsilateral motor pathway from the unaffected motor cortex to affected extremities, through the transcallosal pathway, the anterior CST, and pathways synapsed in the brainstem, such as the reticular formation [1,2,3,4,5,6,21,22,23,24].…”

Identification of Abnormal Motor Cortex Activation Patterns in Children with Cerebral Palsy by Functional Near Infrared Spectroscopy

“…7 Nevertheless, there are case reports on the use of fMRI alone or in combination with transcranial magnetic stimulation, which investigated different aspects of cortical reorganization in children with CP. [8][9][10][11][12][13][14] Although CP is thought to originate mostly from subcortical lesions and less often from cortical ones, 8 there is evidence that associated plasticity changes occur in the motor cortex. [9][10][11][12][13][14] Certain differences in cortical activation patterns have emerged from these studies between healthy and children with CP.…”