TMS and the Neurology of Stroke
Basic findings
After a stroke, the initial functional deficit, degree and pattern of cortical re-organisation and the degree of functional recovery can very greatly among patients. The loss of voluntary movement in the limbs of one side of the body or loss of speech production or understanding are severe consequences of stroke and require intensive rehabilitation. Central motor conduction time prolongation is usually observed along with a high motor threshold (Oxford Handbook).
Ongoing research
Monitoring The Disease
Transcranial magnetic stimulation (TMS) measures excitability of central motor pathways in humans and is used to characterise neuroplasticity after stroke (Wheaton et al., 2009).
Modulating The Disease
Changes in cerebral cortex excitability have been demonstrated after a stroke and are considered relevant for recovery. Repetitive transcranial magnetic stimulation (rTMS) of the brain can modulate cerebral cortex excitability and, when rTMS is given as theta burst stimulation (TBS), LTP- or LTD-like changes can be induced. A recent study found that facilitatory TBS over the stroke hemisphere and inhibitory TBS over the intact hemisphere in acute phase enhance the excitability of the lesioned motor cortex. The authors concluded TBS might be useful to promote cortical plasticity in stroke patients. (Lazzaro et al., 2008)
TMS is a promising therapeutic tool to minimize motor, speech, cognitive, and mood deficits (Bashir et al 2010). Increased cortical activity ipsilateral to the affected muscles has been correlated with good recovery (Schwerin 2007). Additionally, suppression of activity in the contralesional motor cortex may promote the recovery of limb function after stroke (Carey 2007). TMS is being used to provide vital insights into the mechanisms of neurologic recovery and how it can be exploited for modulation of plasticity after brain injury (Bashir et al 2010, Bestmann et al 2010).
Links
References
- Bashir et al., PM&R, 2010.
- Bestmann et al., Journal of Neuroscience, 2010.
- Carey JR et al., Neurorehabil Neural Repair, 2007.
- Hummel et al., Brain, 2005.
- Lazzaro et al., Clinical Neurophysiology, 2008.
- The Oxford Handbook of Transcranial Stimulation.
- Rapisarda et al., Stroke, 1996.
- Schwerin S et al., Exp Brain Res, 2007.
- Wheaton et al., J Neurological Sciences, 2009.
