Abstracts

Functional and clinical outcomes of hemispherectomy have recently become an area of intensive research. Understanding the potential of the remaining hemisphere and the mechanisms of functional recovery is crucial in designing rehabilitation strategies for this population. We investigated the effects of intervention in children with hemispherectomy performed as long as 10 years ago by studying training-induced neuroplasticity of the intact hemisphere, employing functional magnetic resonance imaging (fMRI). Twelve children (4 females and 8 males) who underwent hemispherectomy as part of the UCLA Pediatric Epilepsy Surgery Program between 1986 and 2001 were offered intensive therapy to improve their gait and walking speed. Their age ranged from 10 to 19 years (median 12 years). The postsurgery period ranged from 2 to 10 years (median 6 years). Etiology classification, inclusion criteria and hemispherectomy technique were similar to those reported in de Bode, 2004. Each participant received the Body Weight Support Treadmill Training provided by trained therapists in two sessions a day, 5 days a week for 2 weeks. The fMRI activation study of ankle dorsiflexion (active and passive) was performed before the BWSTT intervention and following its completion two weeks later. To monitor functional changes associated with training the following measures were collected pre- and posttraining: the Fugl-Meyer motor index for the lower extremity, walking speed (normal and fast pace) and the single limb stance time (i.e., the time a child could stand unassisted on her affected leg). Three of the four measures showed statistically significant changes indicating improvements. Functional changes correlated with the evolution of cortical maps observed with fMRI. The two main trends of activation changes were noted: in children with limited ability to actively dorsiflex their ankle cortical maps evolved from wide-spread into focal and localized areas as their ability to move an ankle improved; in children with relatively spared ability to voluntarily move an ankle, locations of cortical activations remained unchanged but intensity of the signal in these areas statistically increased. The goal of our study was to use the intensive practice of a well-defined locomotor therapy to demonstrate that functional improvements associated with cerebral representational plasticity are possible in children whose surgery was 1 - 10 years ago. An intensive pulse of physical therapy seemed to improve walking and reduce impairments associated with hemiplegia. Furthermore, cortical plasticity induced by training suggests that the potential of the remaining hemisphere may not be fully utilized without specific intervention. (Supported by the NRSA in Neurological Rehabilitation (NS 07479) to B. Dobkin, the RehabNet West grant to S. de Bode and R01 NS 38992 to G.W. Mathern)