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SYNOPSIS: The authors of this comprehensive review article found evidence for the use of music-based interventions as part of rehabilitation across a broad range of neurological disorders.
SOURCE: Sihvonen AJ, et al. Music-based interventions in neurological rehabilitation. Lancet Neurol 2017;16:648-660.
Music is an integral part of the human experience, existing in cultures and civilizations throughout history. Although the purpose, meaning, and significance may vary over time, the universal pull of rhythm allows music to assist in crossing language and other psychosocial barriers.
Interest in incorporating music into medical treatment is equally universal. An early case report from Sweden in 1745, “On a mute who can sing,” describes a farmer’s son who developed aphasia post-stroke but retained the ability to sing familiar tunes.1 This may be the first documented report suggesting that the ability to speak words and to sing words are directed by different areas of the brain. As our awareness of the effect of music on the brain has evolved, it is not surprising that interest in studies investigating musical interventions have blossomed.2
Known to improve connectivity of neurons, listening to music reduces the level of analgesics and enhances patient satisfaction in postsurgical settings.3 Active participation in a musical activity appears to stimulate grey and white matter changes and increase neural plasticity.4 Therefore, the use of music-based interventions is a natural fit for areas in which cortical stimulation is essential for progress, such as in the recovery and treatment of neurological disorders.
Noting that the financial and medical burden of neurological disorders often lie in recovery and rehabilitation, Sihvonen et al reviewed and consolidated knowledge of the effect of music-based interventions in rehabilitation of specific disorders, including stroke, dementia, Parkinson’s disease, multiple sclerosis, and epilepsy. Within these broad categories, the authors identified areas of specific impact, such as cognitive rehabilitation, speech post-stroke, or gait in Parkinson’s disease.
The music-based interventions and outcomes in the included studies are quite diverse and cover a range of interventions, including traditional music therapy, rhythmic auditory stimulation (synchronizing movements to rhythm), and music-supported therapy (playing musical instruments usually to help with rehabilitation of gross and fine movements). One newer modality in music-supported therapy involves transforming movement into sound as part of music sonification therapy. For example, a post-stroke patient is encouraged to move an affected arm as a technician attaches sound to position in space, thus substituting rhythmic melodies for impaired proprioception. In this manner, a patient can relearn to eat by “playing” specific sounds or tunes while changing arm position (rather than relying on an impacted internal sense of position in space).5
One challenge with such diversity of interventions and outcomes (as well as different disease states) is the meaningful comparison of results. Sihvonen et al used Cohen’s d value to measure, rate, and compare the effect size of specific outcomes. Cohen’s d is a common way to measure effect size in meta-analytic studies. An effect size is defined as small if d = 0.2 (may not be a meaningful effect and not easily discernible), medium if d = 0.5, and large if d ≥ 0.8.6 Control group protocol varied from study to study.
Stroke: Sixteen randomized, controlled trials (RCTs) were included in this category. Outcomes included motor movements, language improvements, cognitive functions, mood, and quality of life. Two studies show no significant difference between intervention and control groups. In both studies, the control group used a form of sound or other therapy. Sample sizes ranged from 20 to 92. (See Tables 1, 2, and 3.)
Dementia: The authors reviewed 17 RCTs in this category. Most involved music-based therapies and the effect on neuropsychiatric and behavioral symptoms (anxiety, depression, agitation, cognition, and quality of life predominate.) Sample sizes ranged from 18 to 100 participants. Four studies showed no significant difference between the intervention and control groups. It is noteworthy that most of the studies showing cognitive improvement in dementia were restricted to patients with mild forms of this disorder. Two of the RCTs that did not demonstrate an effect from music-based interventions on mood used control groups with active non-music interventions rather than standard care. (See Tables 4 and 5.)
Parkinson’s Disease, Multiple Sclerosis, and Epilepsy: The authors of five RCTs in this review investigated music-based interventions in Parkinson’s disease, primarily looking at the effect on motor symptoms of this degenerative disorder as well as evaluating quality of life and social parameters. All sample sizes were small, with only one study involving more than 50 participants. Dancing clearly had the most effect on motor symptoms in the reviewed studies, helping with balance, stride length, and general mobility.
Only two RCTs included in this study involved music-based interventions in multiple sclerosis, one of the more common neurological disorders occurring in the young adult population. Treatment has been proposed to decrease or prevent flare-ups of new episodes. Neither study included more than 20 participants; results are inconclusive and, according to the study group, allow no firm
One RCT was included for epilepsy. These authors looked at stimulation of the cortex via music as a mechanism to reduce epileptiform activity. Classical music was played every night for a year to 73 participants; the control group received no intervention. Seizure frequency in the active group decreased by 17 % (P = 0.14) during the treatment phase and by 16% one-year post treatment.
Given the widespread access and relatively inexpensive availability of music, the use of music-based interventions in the complex care of patients with neurological disorders is an attractive proposition. In fact, for many caregivers, the informal use of music during treatments and in daily life may be less strategic and more intuitive. This large-scale review study brings promising direction to the field; understanding the effect of specific musical interventions on specified outcomes could and should lead to a more targeted and efficacious approach.
Understanding the effect but also the mechanism of action of these musical interventions is important. At this point, explanations remain speculative — the process is not yet well-delineated. Sihvonen et al offered several possible etiologies that could explain the results presented in the reviewed studies. These are based largely on what is known about the effect of music on the healthy brain.
Three proposed mechanisms were presented: enhancement of neural activation, cerebral blood flow, and neuroplasticity; activation of reward centers; and/or activation of spared neural networks.
Modern medical innovations and imaging studies have confirmed findings from early observational studies (such as a “mute who could sing” noted earlier.) The sparing of music abilities despite widespread speech and language loss led to early conclusions that speaking, language, and music may involve different areas of the brain. We now know that singing, for example, involves bilateral and more extensive areas of the brain than speaking. This allows intervention aimed at relatively healthy portions of the brain post-insult. Familiar tunes activate the anterior and medial prefrontal cortex — areas that tend to be spared from rapid degeneration in Alzheimer’s disease and may help explain why singing is often preserved in these patients.7
Although work remains to be done regarding understanding the full etiology and mechanism of music-based interventions, gaps remain regarding what we know about when the interventions work best and which are most effective. Studies that clearly spell out protocol, including presence or absence of speech therapist and type of music applied, are necessary to make firm recommendations. Looking for publication bias among the published studies is important; replication of the studies in a methodical manner is essential to bring legitimacy and further develop this field.
Future direction in use of music-based interventions most likely will look at the length of time interventions show an effect, the need to reinforce, as well as any relationship between response to music-based interventions and exposure or involvement in music during premorbid years. A not well-studied but hidden benefit of music-based interventions in these neurological disorders may be the positive effect on a caregiver. A caregiver may receive some of the same mood benefits from the music as the patient, a potentially far-reaching intervention given what we know about the stress involved in caring for patients with neurological disorders.8 The development of effective music-based interventions implemented by a caregiver within a home setting provides numerous benefits from economic, logistical, and health perspectives.
There remains enough evidence to promote the use of music-based interventions during rehabilitation and recovery of motor deficits post-stroke, in mobility in Parkinson’s disease, and in treatment of aphasia post-stroke. In dementia, the use of music-based interventions may help with cognitive improvements in early stages of the disease. Although there are mixed results regarding an effect on mood and agitation in dementia and post-stroke, there is no recognizable harm. The results of the investigations of music-based interventions in multiple sclerosis and in epilepsy are inconclusive, but promising preliminary results show exciting potential. Sharing this information with patients and caregivers allows the provider to help shape an innovative and comprehensive treatment plan for rehabilitation from devastating neurologic insults.
The specifics of such a plan will vary not only with patient preference and condition, but also with practical considerations, such as availability of music therapists, caregiver attitudes, and physical limitations such as hearing impairment. At the least, providers can offer the suggestion to add music to everyday routines, all the while remaining actively vigilant in a search for more tailored and accessible interventions appropriate for each unique individual.
Financial Disclosure: Integrative Medicine Alert’s Executive Editor David Kiefer, MD; Peer Reviewer Suhani Bora, MD; AHC Media Executive Editor Leslie Coplin; Editor Jonathan Springston; and Editorial Group Manager Terrey L Hatcher report no financial relationships relevant to this field of study.