The Use of Rhythmic Auditory Stimulation for Gait Disturbance in Patients with Neurologic Disorders

Abstract

The development of modern research technology, such as brain imaging and motor analysis systems, has led to a greater understanding of brain processes involved in the perception and production of music as well as the connectivity between music and motor, speech, and cognitive networks in the brain. These findings have revealed that music therapy could produce stronger and more specific outcomes than merely a general sense of well-being. This has led to the use of music for rehabilitation of motor, speech, and cognitive functions through the systematic application of music for motor disturbances (Thaut et al., 2005; de l'Etoile, 2007). The most highly researched area has been in regards to gait training through the use of Rhythmic Auditory Stimulation (RAS). RAS is defined as:A technique of rhythmic motor cuing to facilitate training of movements that is intrinsically and biologically rhythmical. In humans, the most important type of these movements is gait. Therefore, RAS is used almost exclusively for gait rehabilitation. It uses rhythmic cues in 2/4 or 4/4 meter, presented either as pure metronome beats or as strongly accentuated beats in complete musical patterns, to cue gait parameters such as step cadence, stride length, velocity, symmetry of stride length and stride duration, and double and single support time of leg stance. (Thaut, 2005, p. 138-139)The effects of RAS as a treatment intervention for gait disturbances have been investigated with various patient populations including stroke, Parkinson's disease and other neurologic conditions. These interventions will be described in the following sections.RAS for StrokeAccording to the American Stroke Association (2012), stroke is the number four cause of death and a leading cause of disability in the United States. Deficits following a stroke are highly variable and are dependent upon the type of stroke as well as the area of the brain affected. The most common type of stroke, called an ischemic stroke, occurs when there is sudden vascular insufficiency. Ischemic strokes are most commonly caused by a blood clot formed within a vessel, or a bit of foreign matter, such as part of a blood clot, that is carried along in the bloodstream (Nolte, 2002). Damage from an ischemic stroke depends on several factors, such as the size and distribution of the infarct, as well as the location of the occlusion along the course of the artery. For example, due to the high number of autonomic functions controlled there, a very small lesion in the brainstem can have a much more devastating effect than damage to some large areas of the cerebral hemispheres or cerebellum (Nolte, 2002).The second type of stroke, called a hemorrhagic stroke, results from the rupture of blood vessels in the brain. Blood is then released into the surrounding structures of the brain and blood supply to the area is interrupted. Resulting deficits are again dependent upon the location of the ruptured vessels as well as the size of the bleed. It is important to remember that because axons carrying information from the corticospinal tract cross midline, damage to one cerebral hemisphere results in weakness to the contralateral, or opposite, side of the body (Nolte, 2002).While stroke related deficits are highly variable, gait disturbances are prevalent among a wide range of stroke patients. Common post-stroke gait deficits include reduced preferred walking speed, cadence and stride length, as well as reduced symmetry (Roerdink et al., 2007). Stroke patients may also demonstrate reduced coordination and reduced ability to adjust their gait to variations in task demands such as turning, initiation and termination of gait and speed adjustments. Given that gait disturbances can cause substantial impairment to the quality of life in stroke patients, it is important to identify interventions effective in improving gait coordination, speed and symmetry. RAS is one such intervention that has been found to be effective in improving gait parameters in stroke patients. …