CHARACTERIZATION OF MOTOR CORTEX USING TMS

Project Principal Investigator: Dobrivoje S. Stokic, M.D., D.Sc.

Background: Posttraumatic motor dysfunction, a term denoting heterogeneous motor impairments after severe TBI, causes limitations in dexterity, gait, balance, and strength. Clinical examination alone often fails to differentiate various aspects of motor dysfunction after TBI. Data from other patient groups, however, have revealed the value of innovative diagnostic techniques, such as transcranial magnetic stimulation (TMS), for characterization of mechanisms underlying motor dysfunction. However, few studies have explored the utility of TMS after TBI and the motor cortex pathophysiology underlying motor impairments after TBI has not been adequately characterized.

Motor signs and syndromes similar to stroke and movement disorders can be seen after TBI. They include ataxia, spastic hemiplegia, dystonia, rigidity and bradykinesia, kinetic or rubral tremor, and myoclonus. These often disabling conditions after TBI typically have a delayed onset, may be temporary or persistent, occur in isolation or combined, and affect one or more body segments. Due to the variable nature of TBI, the correlation between the severity of TBI and the development or the degree of severity of motor impairments is poor.

Many patients who suffer from spasticity, dystonia, tremor, bradykinesia, or ataxia after TBI do not respond well to prescribed medications or surgery. Recent advances in magnetic stimulator design allow multiple pulses to be delivered continuously at frequencies up to 50 Hz (repetitive TMS, rTMS). rTMS has pronounced biological effects, that is, the effects can outlast the stimulation itself. Such biological effectiveness opens the possibility of using rTMS as a therapeutic tool after TBI, however, the development of therapeutic rTMS is based on a thorough understanding of motor cortex changes after CNS injury and the ability of rTMS to modify these cortical functions.

Research Goals

Goal 1: Characterize TBI-related motor dysfunctions by describing motor cortex changes using TMS and to relate these changes to the type and severity of motor impairment.

Goal 2: Develop and investigate feasibility, safety, and effect of rTMS therapeutic protocols for modification of TBI-related motor dysfunction.