Dystonia is the third most common movement disorder characterized by excessive involuntary muscle contractions leading to abnormal postures and movements. There are various clinical forms of dystonia, and the current available treatments remain mostly symptomatic. While the vast majority of focal dystonias respond well to pharmacological and surgical treatments, many patients with generalized dystonia continue to have mixed responses. The use of rehabilitation-based treatments has emerged as a means to improve outcomes based on the beneficial effect shown in other movement disorders. In this blog, we invited Drs. Batla, Bradnam, and Kimberley who have expertise in this field to discuss the status of employing a rehabilitation approach for the therapy of dystonia.
What are the limitations of current pharmacological and surgical treatments for dystonia?
Dr. Batla
The current treatments for dystonia are mainly symptomatic and are not curative. The systemic (oral) pharmacological treatments, including anticholinergic, dopaminergic, and GABAergic medications, are the most frequently prescribed therapies for dystonia.1, 2 However, efficacy is modest (in the range of 50-60% improvement of clinical scores) and is compromised by dose-limiting side effects. Much of the evidence supporting these pharmacotherapies are derived from studies using small samples, non-blinded assessments, and anecdotal clinical experience. None of these treatments have been subjected to large-scale, double-blinded, placebo-controlled trials.3, 4 Thus, we do not have FDA approval for the use of these medications in the United States.
For alleviation of focal dystonia, the intramuscular injection of botulinum neurotoxins (BoNT) is one of the main treatments, but BoNT injections are painful, expensive, and require frequent clinic visits usually every three months. Additionally, side effects of BoNT such as dysphagia and neck drop, albeit temporary, may markedly impair the quality-of-life. Moreover, the long-term use of BoNT poses the risk to develop immunoresistance, although newer formulations seem to carry lower risks.5 Another shortcoming is that BoNT may not adequately address all aspects of dystonia. For example, BoNT may be ineffective for the apraxia of eyelid opening present in blepharospasm and laryngeal dystonia. Some forms of dystonia are more responsive or resistant to BoNT. Clear examples are the spasmodic adductor dysphonia that improves more predictably than the abductor dysphonia, or many types of cervical dystonia that respond much better than anterocollis, which requires experienced hands to inject the deep neck muscles.2
Deep brain stimulation (DBS) is an important therapy for dystonia, but the improvement in outcome measures has a wide-range (20 – 70%), and markers predictive of surgical outcomes have not been identified.6 Appropriate utilization of DBS therapy is also limited by high costs, patient eligibility for surgery, and regulatory challenges (the FDA has approved DBS for dystonia only under a humanitarian disease exemption category). Ablative surgical procedures that are irreversible are used in patients with fixed contractures, or if there is a risk for hardware-related complications, or a permanently implanted hardware is not acceptable for the patient.2
Dystonia is associated with several non-motor symptoms, including pain, depression, anxiety, sleep disturbances, and sensory and cognitive deficits;7 however, these features are frequently under-recognized and undertreated. The current pharmacological and surgical treatments are not useful to reduce pain, anxiety, and depression, all symptoms that largely affect the quality of life of patients with dystonia.8
Is there a role for physical rehabilitation in dystonia?
Dr. Bradnam
Definitely! Our recent research has proven people with dystonia have additional functional deficits, some affecting gait and balance control. Some patients may have fear of falling and visual difficulties that significantly reduce the quality of life. Physical rehabilitation should be utilized from a holistic perspective, not just targeted at the dystonic body part. For example, most therapeutic interventions for cervical dystonia to date have focused on exercises aimed at reducing the neck impairment, but have had limited success. It is necessary to encourage people with dystonia to engage in physical activity to maintain/improve their physical and psychological health and well-being.
Dr. Kimberley
There is significant disability associated with focal dystonia due to pain and impairment, reduction in participation of daily activities, employment, loss of self-confidence, and fatigue. These impairments can be addressed with physical therapy. Many small-scale studies have explored the potential benefits of non-pharmacological strategies such as transcutaneous electrical nerve stimulation (TENS), Braille training, and Kinesio Taping, vibration-based training, and movement practice. These strategies have been developed because of evidence of abnormalities in sensorimotor integration in dystonia. There have been varying degrees of success with the application of these strategies.
In cervical and hand dystonia, physical therapy can be helpful in conjunction with botulinum toxin injections to strengthen the muscles injected with the toxin, promote improved body alignment, strengthen antagonist muscles, improve relaxation, task efficiency, and fatigue management. Improvements have been observed in terms of reduced disease severity, quality-of-life, and motor performance. There is some evidence that combining physical therapy with rehabilitation may reduce botulinum dose. In generalized dystonia, physical therapies have a promising role in retraining more normal movement patterns and postures within the context of daily activities such as walking, running, reaching and grasping, and moving from one place to another. 9
Are we underutilizing rehabilitation-based therapies in dystonia? What are the current challenges?
Dr. Kimberley
The main challenges that limit the utilization of rehabilitation for dystonia are lack of sufficient evidence and a low number of trained experts. A systematic review performed a few years ago did not find any A1 or A2 level evidence for interventions with specific physical and occupational therapy for dystonia.10 However, a more recent review proposed a classification system for rehabilitation interventions, and determined that movement practice had the highest-rated evidence.3 In the United States, patients with dystonia are rarely referred to physical therapists, and the treatment of people with dystonia is not typically covered. In Sweden, where physical therapy is more commonly used in the management of cervical dystonia than it is in the US, patients rate it as the second most effective intervention after botulinum toxin.11 In a European survey, only half of the 24 countries that participated reported easy access to rehabilitation therapies.
Most studies conducted so far have included a small number of participants; have employed a broad range of exercises from active isometric exercises, to stretching, biofeedback, sensory training and relaxation techniques including massage therapy.3 As such, systematic reviews have concluded that there is insufficient evidence to recommend any particular strategy for the treatment of dystonia.3, 12 However, given the diversity of this disorder, it is unlikely that a single intervention will prove effective. Complex diseases require complex interventions, which is difficult to standardize in a randomized controlled trial. This does not mean that for a given individual, positive effects cannot be obtained with well-trained providers. In my opinion, what we need most is funding to support large-scale studies.
Dr. Bradnam
We are underutilizing these therapies, and indeed this is a worldwide problem. We need to raise the awareness of dystonia in allied health professionals, develop effective treatments, and implement them in service delivery models that are accessible and affordable.
While customization of the intervention to meet the individual patient needs has a clear advantage, large protocol-based clinical trials are difficult to follow. There is a very limited number of scientifically validated studies to support clear benefits, and large trials are quite challenging to design. Because of these significant limitations, no specific guidelines for rehabilitation therapies have been developed, thereby leading to overall underutilization.
Which combination of rehabilitation-techniques has shown most effective control of dystonia symptoms?
Dr. Bradnam
I do not think it is as simple as, for example, targeting different neck muscles with exercises such as strengthening agonists and stretching antagonists. We have to think about the brain network sub-serving dystonia and design interventions to target that network. Exercises serve to simulate afferent signals from muscles to the brain, which, if delivered incorrectly, can overload the dystonic brain already processing sensory information in a dysfunctional way. The cerebellum is known to participate as a key node in the dysfunctional brain network, movements that enhance cerebellar afferent processing may be worth considering. It is important not to utilize a ‘one size fits all’ approach, as each presentation of dystonia is different. Assessment of the main motor (e.g., tremor) and non-motor (e.g., fatigue) symptoms may provide clues as to the predominant neural circuitry that is dysfunctional in that individual, and this can be used to guide interventions including exercises.
Dr. Batla
There is a role for occupational therapy to help activities of daily living, and a role for sensory-motor integration-based physical therapies to control pain and involuntary movements. In conjunction with adequate medication and cognitive behavior strategies for pain and neuropsychiatric symptoms, these rehabilitation therapies can lead to a better outcome. However, combination strategies have not been validated, and at the end of the day, the lack of supportive evidence undermines recommendations of these approaches widely.
Dr. Kimberley
I believe as an essential first step that movement disorder clinics need to recruit physical and occupational therapists, and then invest in their training for effective treatment strategies for people with dystonia. This has the potential to extend the benefit of botulinum toxin and provide an alternative for those that seek it. Secondarily, we need to recognize that movement practice (through rehabilitation) is a powerful driver of neuroplastic change in the brain. Thus, a better understanding of the nature of dystonia as a brain network disorder will help us refine rehabilitation strategies to partner with the current standard of care.
In closing, dystonia has many clinical forms, and current pharmacological and surgical treatments have several limitations. Thus, the current standard-of-care treatments may not optimally control the overactivity of muscles or the numerous secondary problems that contribute to disability. The causes and manifestations of dystonia are not restricted to the motor system, further adding complexity to the design of effective treatments. Rehabilitation has a promising role as an adjunct treatment; however, we have not thoroughly exploited its therapeutic potential. A multidisciplinary program that addresses the multiple facets of dystonia in the patient as a whole could fill the current gaps, and thereby accomplish the much-needed therapeutic success in this challenging disorder.
References
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