Neurorehabilitation of Parkinson's Disease and ALS.

Parkinson’s disease (PD) is the second most common neurodegenerative disease, exceeded only by Alzheimer’s disease (AD). About 1 million people in the United States, 1 million in Western Europe, and 5 million worldwide suffer from PD. Clinically, PD is characterized by motor symptoms including rest tremor, rigidity, bradykinesia, and posture instability. In addition, patients with PD also suffer from non-motor symptoms including cognitive impairment and dementia, fatigue, autonomic disturbances, and sleep disorders. While the degeneration of dopaminergic neurons in the substantia nigra is responsible for the motor symptoms, the degeneration of nondopaminergic neurons including cholinergic neurons of the nucleus basalis of Meynert (NBM), norepinephrine neurons of the locus coeruleus (LC), serotonin neurons in the raphe nuclei of the brainstem, and peripheral autonomic nervous system are responsible for the nonmotor symptoms (Orlanow el al., 2015). Because PD is a slowly progressive disorder that compromises patients’ quality of life (QOL) progressively, neurorehabilitation plays a critical role in improving QOL in PD. Difficulty turning, freezing, and postural instability result in high risk for falls and fractures. Cognitive impairment and dementia are also major risk factors for shortened life. Poor motor control and cognitive impairment lead to driving impairment. Poor nocturnal sleep and daytime sleepiness associated with dopaminergic medicine further affect driving safety. Neurorehabilitation is increasingly playing a major role as part of a multidisciplinary approach in managing PD. Neurorehabilitation interventions have been used in the treatment of motor, gait, speech, and cognitive problems (Uc et al., 2014). A systematic review showed that neurorehabilitation has beneficial effect on motor functions, quality of life, and activities of daily living (Foster et al., 2014). The advance of technology enables researchers to use wireless wearable sensors to measure motor impairments in PD quantitatively. In this issue, Mancini el al. used wireless sensors to compare turning mobility in PD versus normal control over seven days. They showed that although the total numbers of steps and turns were not different between the two groups, the PD group had slower and more variable turning velocity and higher number of steps per turn. These wearable sensors therefore can quantitatively detect abnormality in turning that cannot be detected by clinical examination. These sensors will be useful for monitoring progress in rehabilitation practice and clinical trials. Parkinson’s disease, due to its slowly progressive nature, may offer a unique model to investigate whether non-invasive brain stimulation (NIBS) such as transcranial magnetic stimulation (TMS) or direct current stimulation (tDCS) can improve symptoms and reverse functional changes in the motor cortex and motor circuit secondary to dopaminergic deficiency. The motor system is an ideal target for cause-effect exploration, because its output can easily be measured using neurophysiological techniques such as surface EMG or motor function assessment. The rationale for non-invasive brain stimulation is that if the abnormalities in brain activity and physiology that cause clinical deficits are reversed, normal function should be restored. The dramatic effects of deep brain stimulation (DBS) provide the best evidence for this rationale and suggest that DBS may have widespread effects across the motor circuit that connects motor cortex, basal ganglia, and thalamus. This raises hope that stimulating elsewhere within this circuit, such as stimulating motor cortex by NIBS, could achieve comparable effects. The second paper, by Benninger and Hallett, reviewed the available clinical studies in TMS and tDCS. Although rTMS and tDCS have therapeutic potential, their clinical effects so