TMS Motor Mapping Applications

Basic Neurophysiology / Plasticity Assessment

Mapping the motor cortex with TMS enables assessing motor cortex physiology and plasticity. For instance, corticomotor representation of finger muscles can be mapped using single pulse TMS. These muscle-specific maps are thought to contain spatial information about its functional cortical representation in motor cortex and is used to study plasticity of human hand. Additional examples include studying relationship of direction of TMS induced current to cortical output, neuronal reactivity, cortical connectivity, obtain insights into mechanisms for diseases involving motor problems, etc.

Brain Surgery Planning

The determination of viable cortical areas responsible for function is crucial for safe and effective resection. The need to resect as much as possible is continuously balanced by the need to preserve the patient’s existing function and quality of life. In addition, the tumor itself may distort underlying anatomical features. As navigated TMS allows co-registration of motor maps with the patient’s anatomical scan, localization of the exact area for a response can be readily determined. Infact, navigated TMS has been validated to be as accurate to Direct Cortical Stimulation which is considered the gold standard for generating maps of the motor system.

Motor recovery after stroke

TMS Motor Mapping may act as a marker for recovery of function after stroke. It is known that clinical improvement of hand function after stroke is accompanied by profound functional reorganization within motor areas of both hemispheres, representing brain plasticity changes. These could be either beneficial or detrimental and as such can be mapped using TMS. For instance, measuring the location, extent, and amount of cortical hand motor representation, within motor cortices of both the lesioned and the non-lesioned hemisphere help understand the mechanisms underlying motor recovery after stroke. Similarly, studying the aforementioned metrics over time also contribute to this understanding. The knowledge of the underlying changes within motor cortex after stroke may help develop individualized treatment approaches aiming to modulate maladaptive plasticity in order to facilitate recovery after stroke.

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