Research suggests the use of rhythmic stimuli for gait rehabilitation can help improve gait and balance in patients with Parkinson disease, stroke, and other conditions, but some questions regarding its overall applicability and optimal delivery method remain.

By Greg Gargiulo

Moving one’s body in sync with the rhythm of music is a natural phenomenon that anyone who’s ever danced to a beat can easily attest to.^1,2 Because rhythm is an essential element in both music and many motor-control functions, music is capable of stimulating synchronized bodily movements, and this phenomenon can bring about positive therapeutic effects beyond the pleasure of dancing to one’s favorite song.^3,4

The concept of music as a therapy has been around for thousands of years, and was originally based on ancient beliefs that it can have a healing effect on mind and body.⁵ More recently, music therapy has been used in research and clinical settings to rehabilitate patients with neurological or physical disorders, and one of its emerging applications is for improving gait in those with impairments.^6-9

Current research has shown that this type of music therapy can lead to significant improvements in various aspects of gait, as well as balance, in patients with Parkinson disease and stroke.^10-17 But the evidence base in support of music therapy for improving gait in other neurological disorders is not as strong, and some questions regarding its overall applicability and optimal delivery method remain.^18-24

Starting with rhythm

Neurologic music therapy (NMT) is a set of research-based methods for the therapeutic application of music to cognitive, sensory, and motor function deficits related to neurologic disease.⁷

Michael Thaut, PhD, director of the Center for Biomedical Research in Music at Colorado State University in Fort Collins, developed NMT in the early 1990s after realizing that traditional approaches to music therapy hadn’t yet led to any major breakthroughs.

“I thought we should start with rhythm, one of the most important elements in musical structure, and the observation that, when rhythmic sound somehow activates the motor system, it’s almost instinctive to move rhythmically, so there must be some connections between the auditory system and the motor system,” Thaut said.

Advertisement

His research led him to discover that there are in fact regions of the brain where sound processing and motor system control both occur, creating very direct connections between the two networks; this discovery formed the basis of NMT.

“NMT is based on a neuroscience model of how music changes the brain and how the elements in music work as therapy, and it differs from conventional music therapy, which uses more of a social/psychological interpretive approach to music,” Thaut said.

NMT is comprehensive, with techniques for upper extremity rehabilitation and cognitive and speech rehabilitation. But, when the technique uses rhythmic stimuli to work with gait, it’s called rhythmic auditory stimulation (RAS).² RAS is used primarily to aid the recovery of walking patterns in patients with significant gait deficits from stroke, Parkinson disease, traumatic brain injury, or other causes.⁴

RAS works as follows: a piece of music or a metronome click is selected with a constant rhythm—usually in either 2/4 or 4/4 meter, which are basic symmetric beats in the rhythmic structure of walking—and a tempo that’s based on the target gait speed. It’s then played through a personal audio device or stereo, and the rhythm serves as an anticipatory and continuous time reference, or cue, for the patient’s movements.^8,16,25-27

Parkinsonian gait is typically characterized by reduced velocity, shortened stride length, increased cadence, asymmetric stride times, and occasional freezing or festination.^1,11 These gait deficits, which are resistant to most pharmacological and surgical treatments, may also lead to falls, making them a major clinical challenge.^10,12

Parkinson disease research

RAS and other similar techniques for improving gait in Parkinson patients have been studied since the early days of Thaut’s research.^10-12,20,28

A 1996 study by McIntosh et al found that a RAS 10% faster than baseline cadence was associated with significant improvements in mean gait velocity, cadence, and stride length in 31 Parkinson patients and 10 healthy elderly adults.²⁸ A meta-analysis by de Dreu et al concluded that similar auditory cueing techniques combined with exercise therapy led to small but significant effects on stride length and balance.¹²

In studies by Benoit et al and Dalla Bella et al, musically cued gait training not only increased stride length and speed, but extended beyond gait, leading to improvements in perceptual and sensorimotor timing abilities that lasted after training ended.^10,11 These studies suggest this type of training may help delay cognitive decline in Parkinson patients.

Two other studies have found that listening to music can actually exacerbate gait impairments in Parkinson patients, possibly because, for some patients, listening to the music was effectively an additional task that directed attention away from the primary task of walking safely.^1,29 However, another randomized controlled trial by many of the same authors found that a similar program was safe and led to multiple improvements.²⁴

“In the later study, the participants had repeatedly been exposed to the task of walking whilst listening to music. We actually found that not only was there an improvement in gait and motor symptoms, but the participants with Parkinson’s disease also improved in their ability to dual-task, which was not the case with our other studies,” said Natalie de Bruin, PhD, a postdoctoral researcher in the Balance Research Laboratory at the University of Lethbridge in Alberta, Canada, and a coauthor of these studies.

Studies of stroke

Music therapy approaches such as RAS have been found to elicit significant improvements in various gait parameters for stroke patients.^13-16,25,26

In a randomized controlled trial of 78 patients—a larger sample size than most music therapy studies—Thaut et al found that RAS led to significant improvements in velocity, stride length, cadence, and symmetry from baseline when compared with neurodevelopmental therapy, a more traditional type of gait therapy.²⁵ Other studies have confirmed this with similar comparisons, and have also identified improvements in balance, stability, and quality of life.^13-16,26,30

In a 2013 systematic review, ²⁰ Wittwer et al evaluated six studies on rhythmic auditory cueing for gait in stroke patients, and determined that there was moderate evidence of improved velocity and stride length after gait training. They concluded that more high quality and larger studies were needed before recommendations for clinical practice could be made.

But according to Joanne Wittwer, PhD, a physical therapist and research fellow in the movement laboratory at the Musculoskeletal Research Center of La Trobe University in Bundoora, Australia, “More high quality studies of auditory cues to improve gait in stroke patients have been completed since then, such as Cha et al¹⁴ and Kim et al,³¹” she said. “This increased the level of evidence from moderate to strong, and I think that there is now sufficient evidence for the approach to be recommended in clinical practice.”

Other populations

While most of the literature pertaining to Parkinson disease and stroke is generally favorable, evidence is more varied for other neurological disorders.^{4,8,17,22,27,32-36}

Two studies of patients with cerebral palsy found that RAS led to improvements in stride length and velocity, as well as positive kinematic changes at the pelvis and hip.^4,22

Conversely, a study by Clair and O’Konski³² found that RAS was not associated with statistically significant changes in cadence, velocity, or stride length in late-stage dementia patients. However, the authors still believe RAS is a viable approach in this population.

“I actually don’t think there was a negative outcome, there just wasn’t much of a positive outcome,” said first author Alicia Ann Clair, PhD, a board-certified music therapist and professor emeritus at the University of Kansas in Lawrence. “We chose people who were too impaired and needed a two-person assist. As a result, they got their cueing from the people walking them instead of the auditory clicks.”

One study on auditory cueing for Huntington disease patients did not detect a significant positive impact on gait parameters,³⁵ while another found that it improved locomotor function.³⁴ Other studies have demonstrated positive effects on gait for patients with traumatic brain injury¹⁷ and healthy older adults at risk for falls.^33,25 However, in patients with Alzheimer disease or spinal cord injuries, auditory cueing led to negative and insignificant effects, respec­tively.^21,27

Regarding disorders other than Parkinson disease and stroke, Wittwer et al’s systematic review concluded that current evidence of benefit is still insufficient.²⁰

“In general, neurological rehab studies on brain injuries, stroke, Parkinson’s disease, cerebral palsy, and the like will never have hundreds of participants,” Thaut said. “It’s just not possible. But in good randomized experimental studies, even if it’s small sample sizes, if you show consistent results across the research, that will make up for the lack of size in one single study. RAS in the neurological rehab literature is considered a level one evidence-based medicine clinical technique, so it has actually very strong support.”

Mechanistic questions

Despite the growing body of research on the topic, the actual mechanisms by which RAS mediates the synchronization between motor and auditory systems are still not completely understood.^8,21,37

“I think that the difficulty in understanding how RAS works has to do with the physiological complexity of walking, the heterogeneity of gait impairments, and the underlying neurologic disorders or injuries that caused them,” said Francois Bethoux, MD, a physiatrist at the Mellen Center for Multiple Sclerosis Treatment and Research at the Cleveland Clinic Foundation in Ohio. “But the ‘therapeutic ingredient’ of RAS is thought to be the ‘beat,’ which is thought to work through entrainment.”

Auditory entrainment is the body’s ability to synchronize movements to an external rhythmic cue with a stable time relationship;^4,25 rhythm serves as an anticipatory and continuous time reference for movement. This is believed to occur via extensive connections between the auditory and motor regions of the brain. In this model, improvements in impaired gait likely stem from patients’ capacity to access auditory-premotor circuits that still remain functional.²¹

Meanwhile, researchers are also investigating strategies to enhance the effectiveness of music therapy. Use of music or metronome clicks, characteristics of music selections like genre, “groove” and familiarity, and method of delivery have all have been found to influence the impact of auditory cueing.^{15,18,19,32,37}

A wide variety of musical genres, either chosen by researchers or participants, as well as simple metronome clicks, have all been used as auditory cues. The wide range of genres includes classical, funk, country, jazz, big band, rock, and folk, but every piece is based on a desirable rhythm of 2/4 or 4/4, and a tempo that is typically 40 to 120 beats per minute. Though patients may prefer certain styles of music, no major correlations have been found between specific genres and gait improvements.^15,20,26

“The style of music is completely irrelevant to gait facilitation as long as it’s rhythmically structured to the foot movements in walking,” Thaut said.

“Groove,” or how much the music makes someone want to move, and participants’ familiarity with the music have also been investigated. Leow et al found that, during synchronization of footsteps to a music beat, high-groove and high-familiarity music led to more accurate tempo matching with faster and less variable strides than low-groove and low-familiarity music.^18,19

Studies also differ in their use of either metronome clicks or musical selections for auditory cueing, with some finding that the two lead to similar improvements and may be used interchangeably.^10,11,20

“The metronome clicks can activate the motor system in the same way, and the music is not necessary,” Clair said. “Music just makes it more interesting.”

A 2012 study by Wittwer et al found that music, but not metronome cues, produced a significant increase in mean gait velocity in healthy older adults, but the sample size was small.³⁷

“I think that because most people like to listen to some type of music, and have an emotional response to music, it’s a good way to entice them,” Bethoux said. “Music also triggers other brain functions; for example, specific music pieces are often tied to memories.”

Delivery methods

The method of delivery, such as the device through which the cue is played (ie, stereo or portable music player with headphones) and the use of instructions, also may influence the effectiveness of auditory cueing.^1,8,10,11,29 An MP3 player, according to Bethoux, can help patients focus on the stimulus by blocking out some of the ambient noise, while a stereo allows researchers to give directions to participants during training and may be safer overall.^1,8,10,24

Although instructions typically are given to patients before initiating therapy in most studies,^20,37,38 Clair believes it may actually be unnecessary.

“Sometimes it’s better to not use any instructions, especially if people have significant neurological problems,” she said. “Trying to get them to cognitively think about what they’re doing may actually make it harder to get them to respond appropriately.”

Software applications are available for mobile devices that deliver auditory cues to improve walking patterns, one of which was found to be a safe and effective adjunct for symptomatic improvement of gait in Parkinson patients.²³

“I believe that self-guided and personalized training is an interesting avenue to be pursued, provided that these methods, even if realized at home, are supervised by a doctor and validated scientifically,” said Simone Dalla Bella, PhD, a professor in the EuroMov Movement to Health Laboratory at the University of Montpellier in France.

Safety is an important concern in the application of any auditory cueing techniques.^8,24

“I definitely think some guidance is needed, at least at the beginning, and periodic re-evaluations are also necessary for some patients, particularly those with progressive conditions,” Bethoux said. “One of the reasons for this guidance is safety.”

Clair also pointed out that patients must keep up with their training to maintain initial improvements.

“RAS can powerfully facilitate gait rehab, but if patients don’t regularly keep up their walking program at home, they will lose skill,” she said.

With additional funding and further support, experts said, the clinical use of music therapy for treatment of gait impairments will expand.^13,15,20,38

“I think it’s a really simple technique that can be used very easily with very little technology and resources, and the effect of auditory rhythm as a sort of anticipatory timer for the motor system is extremely helpful for motor control,” Thaut said. “We’re fortunate to have seen some wonderful things with it.”

Greg Gargiulo is a freelance medical writer based in the San Francisco Bay Area.

Advertisement