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Rehabilitation in Neuromuscular Disorders
∗ The first edition of this chapter was coauthored with Lisa Krivickas, MD. This current chapter includes some of Dr. Krivickas’ original work.
While there are no cures for so many neuromuscular disorders (NMDs), pharmacologic and other interventions are increasingly available to slow the progression of some NMDs. Rehabilitation is currently a cornerstone of comprehensive NMD management, optimizing quality of life and facilitating function and independence to the greatest extent, and for the longest duration, possible. As life expectancy increases, individually tailored rehabilitation across the trajectory of disease will become ever more important.
Rehabilitation is the process of helping a person to reach the fullest physical, psychological, social, vocational, avocational, and educational potential consistent with their physiological or anatomic impairment, environmental limitations, and desires and life plans. Realistic goals are determined by the person and those concerned with his or her care. Thus, one is working to obtain optimal function despite residual disability, even if the impairment is caused by a pathological process that cannot be reversed ( ).
The pathologic processes underlying NMDs are often progressive and irreversible. Comprehensive care should include rehabilitation that restores patients to a level of optimal functioning in their normal societal environments and achieves the optimal quality of life possible throughout the course of the disease. Rehabilitation includes management of musculoskeletal dysfunction, respiratory failure, dysarthria, dysphagia, pain, mood, and cognition and is attentive to the patient’s environment, quality of life, and family and caregivers.
The nature of rehabilitation for individuals with NMDs can vary over time with changes in health and social supports. Thus, rehabilitation can be more challenging for these patients than for patients with static functional deficits caused by single events, such as spinal cord injury. One of the most difficult tasks for the rehabilitation team is to predict how quickly the patient’s disease will progress so that the team can “stay ahead” of the disease process and can recommend interventions at appropriate times. This is most difficult with more rapidly progressing disease processes.
Rehabilitation and symptom management in NMDs may be approached in a problem-oriented manner. Rehabilitation topics addressed in this chapter include the role of exercise in patients with NMDs and management of impairments resulting in difficulties with mobility, activities of daily living (ADLs), communication, and the maintenance of oxygenation and nutrition. Musculoskeletal pain syndromes are discussed because of their direct effect on the ability to exercise, maintain mobility, and perform ADLs. Mood disorders and cognitive dysfunction are discussed because they are easily overlooked in the context of multiple rehabilitation needs and impaired communication; optimal management can allow patients to maintain social contacts, improve patient quality of life, and lessen caregiver and family stress. Palliative care is also discussed, as early initiation of palliative care provides a valuable layer of support and continuity for patients across the trajectory of illness. Palliative care collaboration provides valuable guidance for a patient’s primary providers in optimizing symptom management and advance care planning. Palliative care can be provided concurrently with primary treatment and management of NMDs.
Rehabilitation needs are best addressed by interdisciplinary teams, which can consist of some or all of the following individuals: physiatrist, neurologist, psychologist, physical therapist, occupational therapist, speech therapist, recreational therapist, nutritionist, respiratory therapist, orthotist, social worker, chaplain, peer visitor, palliative care specialist, and nurse. At the center of every team are the patient and family. Studies from the Netherlands, Ireland, and Italy have shown that patients with amyotrophic lateral sclerosis (ALS) who are cared for in a multidisciplinary clinic have a better quality of life, longer survival, and fewer emergency hospitalizations and are more likely to use riluzole and noninvasive positive-pressure ventilation (NIPPV) ( ; ; ). They are also more likely to have the appropriate equipment and assistive devices to meet their needs. The same findings hold true for those with other NMDs.
Rehabilitation services are beneficial throughout the course of a person’s life with an NMD ( ). Most NMDs are not static; as function declines, patients develop needs for new treatment interventions to improve outcomes, and additional therapy is required. Frequently, therapy is also required to maintain a certain functional status, i.e., maintenance therapy (which, since the first edition of this book, has become a Medicare-covered indication for therapy). By knowing how many therapy sessions a patient’s insurance plan will allow, the rehabilitation team can thoughtfully use short bouts of therapy intermittently over time as needed, with special attention to giving patients recommendations for home use and indications for initiating new rounds of therapies. For example, a patient with early ALS may be referred to a physical therapist for help with designing an appropriate aerobic exercise and strengthening program. As increasing spasticity develops, the patient and family may return to physical therapy for a few sessions of education about stretching and range-of-motion exercises. If foot drop develops and the patient is prescribed an ankle-foot orthosis (AFO), he or she may return for a few sessions of gait training with the new brace. As weakness increases, additional sessions of physical therapy may be necessary to teach a caregiver how to transfer the patient between surfaces effectively.
Management of Muscle Weakness
Exercise
Exercise is an important part of the rehabilitation process for individuals with NMDs of all severities. Early in the course of progressive disease, an exercise program can maximize strength and prolong independence. For those with disease states that respond to pharmacologic treatment (e.g., multifocal motor neuropathy), exercise can reverse acquired muscle weakness and cardiovascular deconditioning. For any patient for whom exercise is an important part of lifestyle, continuing to exercise improves mood, psychological well-being, and social engagement.
Several factors must be considered when assessing the ability of patients with NMDs to participate in and benefit from an exercise program. The specific diagnosis and rate of disease progression will affect the response to exercise. One might expect patients with neuropathic disorders to respond differently from those with myopathic disorders. In rapidly and relatively rapidly progressive diseases, slowing the rate of functional impairment is a positive outcome. In more slowly progressive diseases, a positive outcome might be actual gain of strength or aerobic exercise capacity. Response to an exercise program can be affected by patient age, baseline strength, baseline physical activity, cardiopulmonary health, and medication regimen. For example, the cardiomyopathy associated with some muscular dystrophies and the restrictive lung disease associated with both dystrophies and anterior horn cell disorders may limit aerobic capacity. Medications such as beta-blockers can limit aerobic exercise capacity. Each of these factors must be considered when designing exercise programs as well as studies to investigate the role of exercise in patients with NMDs. Generally, exercise within a patient’s comfort level (no pain or prolonged postexercise soreness) is considered to be safe, without producing overuse weakness.
Four forms of exercise training are relevant to patients with NMDs: flexibility , strengthening , aerobic , and balance exercises . The general benefits of these four forms of exercise are summarized in Table 8.1 .
Table 8.1
Exercise Training Relevant to Patients with Neuromuscular Disorders
| Type of Exercise | Description | General Benefits |
|---|---|---|
| Flexibility | Stretching and range of motion | Prevent contractures Prevent pain Reduce spasticity Increase joint blood flow and lubrication |
| Resistance | Strengthening Static (no joint movement) Isometric (constant length) Dynamic (involving joint movement) Isotonic (constant force) Isokinetic (constant velocity) Concentric (shortening contraction) Eccentric (lengthening contraction) |
Reverse disuse weakness Strengthen minimally weak muscles Delay onset of impairment Muscle fiber hypertrophy Fiber-type conversion Increase protein synthesis Increase capillary density Reduce mitochondrial density Reduce lipid storage Neural adaptations |
| Aerobic | Low-resistance dynamic activity using large muscle groups that has a cardiopulmonary training effect | Improve functional exercise capacity Decrease psychological stress Improve quality of life Improve sleep Prevent secondary diseases Help maintain bone density Greater independence with activities of daily living in the frail elderly |
| Balance | Improving unipedal stance and functional reach | Reduce risk of falls |
Flexibility Training
Flexibility training involves stretching and range-of-motion (ROM) exercises. Although there is little scientific literature on the role of flexibility training in patients with NMDs, it is generally accepted that this form of exercise (often in combination with orthotic use for prolonged static stretch) can help prevent the development of contractures. Contractures typically develop in the shoulder, when patients are too weak to raise their arms overhead, and also in the hips, knees, and ankles, when patients spend most of their days in wheelchairs. Contractures can place weak muscles at biomechanical disadvantage, impairing their function. In addition, it can also produce pain and interfere with positioning and the performance of ADLs. In addition to preventing contractures, ROM exercises stimulate joint and cartilage blood flow, enhancing the health and lubrication of joints in both healthy individuals and those with NMDs.
Strengthening Exercises
Providing an appropriate exercise prescription is an important component of a rehabilitation program. Importantly, among the several forms of strengthening exercises, some may be safer than others for patients with NMDs.
Strengthening exercises can be classified as static or dynamic. Static (also called isometric ) exercises are those performed at a constant muscle length, e.g., quadriceps setting (straight-leg raises using gravity or ankle weights to strengthen the quadriceps). Dynamic exercise involves joint movement. Dynamic muscle actions can be described as isotonic , isokinetic , concentric , and eccentric. Isotonic muscle actions supply constant force throughout a muscle movement, which rarely occurs in real-life settings. Isokinetic muscle actions are those performed at a constant velocity and require the use of specially designed exercise machines. Concentric actions are those in which the muscle shortens as it produces force, and eccentric actions are those in which the muscle lengthens as it produces force. Elbow flexion using a dumbbell (a “curl”) is a concentric action of the biceps muscle; if the weight is then slowly lowered by extending the elbow, an eccentric muscle action of the biceps occurs.
Eccentric muscle actions are more efficient than concentric actions and generate more force at a given level of exertion. In healthy individuals, a heavy bout of eccentric exercise can produce a long-lasting decrease in muscle twitch tension and elevated serum creatine kinase (CK). Muscle fiber necrosis and mononuclear cell infiltration may be seen on muscle biopsy specimens for up to 20 days after such a bout of exercise. In healthy individuals, this muscle damage may serve as a stimulus for hypertrophy. However, in patients with muscle diseases affecting the cell membrane, such as the dystrophinopathies and sarcoglycanopathies, there is concern that the damage may not be reparable, and heavy exercise is generally not recommended. Both muscular and neural adaptations occur in response to strength training. Muscular adaptations take at least 6 to 8 weeks to develop. They include muscle fiber hypertrophy, conversion from type IIa to type IIx fibers, increased protein synthesis, decreased protein degradation, increased capillary density, reduced mitochondrial density, and decreased lipid storage. Neural adaptations may occur in as little as 2 weeks and account for early strength gains when a training program is initiated. Neural adaptations occur without muscle hypertrophy and may be due to increased motor unit activation and synchronization. Cross-transference is a neural adaptation in which a single limb is trained, but strength increases also occur in the contralateral untrained limb. This is an important consideration in reviewing the literature on strength training in NMDs because some studies have been designed such that a single limb is exercised, with the contralateral limb used as a control.
Studies across NMD subtypes suggest that strengthening exercise can be tolerated and has a beneficial effect.
In muscle disease (e.g., fascioscapulohumeral dystrophy [FSHD], myotonic dystrophy, hereditary muscular dystrophies), moderate-intensity strengthening exercises appear to be safe, although they do not necessarily result in dramatic strength gains in individual muscles ( ). Generally, exercise is recommended for maintaining strength and slowing disease progression ( ).
In motor neuron disease, ALS and postpolio syndrome (PPS) are best studied. In ALS, moderate-intensity strengthening exercise is considered safe and generally recommended for its impact on function and quality of life. Although studies are limited by population heterogeneity, small sample size, and methodological differences, generally, a positive impact on function and quality of life is found, with no adverse safety events; a profound impact on survival has not been demonstrated ( ; ; ; ). Studies of strength training in individuals with PPS have shown increased quadriceps strength without evidence of histologic muscle damage, changes in CK, or changes in motor unit physiology, suggesting neutrally mediated strength gains ( ; ; ; ).
Regarding neuromuscular junction disorders, a recent study in myasthenia gravis suggests that strengthening exercise is tolerated and may have a beneficial impact on function ( ).
In hereditary motor and sensory neuropathy, or Charcot-Marie-Tooth (CMT) neuropathy, a retrospective study showed an association between self-directed exercise strength in certain muscles, suggesting that exercise could be well tolerated in some subpopulations of individuals with CMT ( ).
An interesting case report of heavy resistance training in a patient with a mitochondrial myopathy demonstrates a possible “gene shifting” benefit induced by exercise ( ). When heavy resistance exercise damages the muscle, satellite cells are incorporated into the muscle as part of the repair process. In mitochondrial disorders, satellite cells contain much lower levels of mutant mitochondrial DNA than do muscle cells. By incorporating satellite cells into muscle, the proportion of mitochondria carrying mutant DNA can be reduced. In a patient with Kearns-Sayre syndrome, wild-type mitochondrial DNA in the biceps increased by 33% with an 18-day training program. Interestingly, concentric exercise appears to cause greater gene shifting than eccentric exercise.
Although most studies of strength training have focused on major muscle groups in the extremities that are important for mobility and ADLs, the impact of strength training on ventilatory muscle function is also important in patients with NMDs. A 3-month uncontrolled study of an inspiratory muscle training program in 24 adults with motor neuron disease, neuromuscular junction disorders (mainly myasthenia gravis), and myopathies demonstrated increases in forced vital capacity (FVC), maximum voluntary ventilation (MVV; a measure of ventilatory muscle endurance), and maximum inspiratory pressure (MIP) in all groups ( ). Interestingly, the patients with motor neuron disease were the weakest initially and made the greatest gains. Several studies have addressed the role of inspiratory muscle training in boys with Duchenne muscular dystrophy (DMD) ( ; ; ; ). One study found an increase in MIP in those with an FVC greater than 25% of predicted ( ); another study documented an increase in MVV with no change in MIP ( ). FVC did not improve in any of these studies, but there was no evidence of overuse weakness. Inspiratory muscle training in patients with myasthenia gravis has also improved respiratory muscle strength and endurance ( ). The clinical impact of small increases in MIP and MVV is unknown.
Aerobic Exercise
Aerobic exercise refers to prolonged low-resistance dynamic activity utilizing large muscle groups; it has a cardiopulmonary training effect. The American College of Sports Medicine recommends that the minimum quantity and quality of training to maintain cardiorespiratory fitness in healthy adults is at least 30 minutes of aerobic activity at 55% to 90% of maximum heart rate (HR) or 40% to 85% of maximum oxygen uptake (V o 2 max) reserve most days of the week; activity may be accumulated in 10-minute bouts. Maximum HR can be estimated using the formula: HR = 220 – age. In healthy individuals, aerobic exercise improves functional exercise capacity, decreases psychological stress, improves quality of life, helps prevent secondary diseases (i.e., heart disease, diabetes, cancer), improves sleep, helps maintain bone density if performed in a weight-bearing manner, and produces greater independence with ADLs in the frail elderly. In general, the cardiovascular response to aerobic training in patients with NMDs appears to be the same as that in healthy adults. A study comparing the response of patients with a variety of myopathic disorders to control subjects during a cycle ergometer exercise test found that, in general, the patients had normal resting oxygen consumption and a normal oxygen cost of exercise ( ). Their V o 2 max was reduced, reflecting their deconditioned status. Of the 24 patients in the study, 5 had an increased oxygen cost of exercise; their diagnoses were Becker muscular dystrophy, carnitine palmitoyl transferase deficiency, and mitochondrial myopathy.
Training studies utilizing home-based cycle ergometry have been performed in patients with FSHD, myotonic dystrophy, limb girdle muscular dystrophy (LGMD) type 2I, Guillain-Barré syndrome, and chronic inflammatory demyelinating polyradiculoneuropathy. In all of these studies, V o 2 max increased, with some self-reported improvement in strength, endurance, ability to perform ADLs, and mood ( ; ; ; ). Patients with McArdle disease (myophosphorylase deficiency) have also shown a positive response to a carefully controlled walking and cycling aerobic exercise program ( ).
Taivassalo et al. have studied adaptations to aerobic training in patients with mitochondrial myopathy. In an initial study, 10 patients with varied mitochondrial disorders (chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, and myopathy) trained for 8 weeks on a treadmill at 60% to 80% of HR three to four times per week for 20 to 30 minutes ( ). Aerobic capacity and exercise duration improved by 30%. Serum lactate concentrations at rest and after exercise decreased by 30%, and magnetic resonance spectroscopy measurements of adenosine diphosphate recovery after exercise improved by 60%. In a follow-up study utilizing a similar protocol, patients with mitochondrial disorders, patients with other myopathies, and sedentary control subjects were trained ( ). Aerobic capacity improved in all three groups, but the gain was greatest in the group with mitochondrial disorders. There has been some concern that endurance training might shift the proportion of mutant to wild-type mitochondrial DNA in a deleterious manner. However, studies have demonstrated an increase in the overall mitochondrial DNA content without a change in the ratio of mutant to wild-type DNA ( ; ).
Several studies have documented aerobic training benefits in patients with PPS ( ; ; ). These studies have utilized both cycle ergometry and treadmill training and have demonstrated increases in V o 2 max, endurance, and oxygen consumption at a given exercise intensity without any loss of strength or other adverse events.
In a study of response to aerobic exercise in individuals with ALS, the oxygen cost of exercise was increased, possibly because of spasticity. Ventilation and HR increases were proportional to those in oxygen consumption, as would be expected in healthy individuals ( ). Interestingly, the expected increases in plasma free fatty acids, beta-hydroxybutyrate, and carnitine were blunted in patients with ALS, suggesting a possible defect in lipid metabolism.
A small study of patients with ALS and respiratory insufficiency who exercised on a treadmill while using bilevel positive airway pressure ventilation has suggested that the progression of respiratory failure may be slowed by aerobic exercise ( ).
Recently, the impact of aerobic exercise for individuals with CMT-1A and individuals with inclusion body myositis (IBM) was assessed. A 12-week exercise program utilizing recumbent exercise bicycles was found to be feasible and safe and to yield improvements in V o 2 max ( ).
Balance Exercises and Training
Balance often is impaired in patients with NMDs due to a combination of sensory neuropathy, proximal muscle weakness, and/or spasticity. In neuromuscular disease, the pattern of weakness can yield impairments in static and/or dynamic balance, with proximal weakness yielding greater impairment in static balance and distal weakness yielding greater perturbation of dynamic balance ( ).
Impaired balance, which may be defined as a unipedal stance time of less than 30 seconds, is a risk factor for falling among healthy older individuals ( ). Among patients referred to a university electromyography laboratory for lower extremity complaints, an abnormal unipedal stance time (<45 seconds) had a sensitivity of 83% and specificity of 71% for predicting peripheral neuropathy ( ). Clinically, balance training is generally included in exercise programs for individuals with NMD. Rigorous research on the types of interventions and long-term impact on function and fall risk in this population is sparse.
enrolled patients with diabetic neuropathy in a 3-week exercise program designed to improve balance. The exercises included bipedal and unipedal toe raises, heel raises, and ankle inversion and eversion exercises as well as unipedal balance challenges. Patients improved their unipedal and tandem stance time as well as their functional reach. These results suggest that balance exercises may be a promising therapy for patients with NMDs if the improvements translate into a decreased incidence of falling.
Exercise Recommendations
Existing research regarding exercise in patients with NMD is limited in scope, but some recommendations for exercise prescription can be formulated. An exercise prescription should include the form of exercise, as well as the intensity, duration, and frequency of training sessions. Research thus far has focused on the safety and efficacy of exercise with increasing attention to the impact of exercise programs on performance of ADLs, as well as mood, psychological well-being, sleep, and appetite. Even in cases where exercise has a minimal impact on physical function, it may still have an important impact on quality-of-life parameters such as those mentioned here.
Flexibility and ROM exercises are certainly safe and should be prescribed to all patients with or at risk for muscle tightness due to limited mobility or spasticity.
Strength training appears to be safe when performed with proper supervision. It can reverse disuse weakness and may improve absolute muscle strength in those with more slowly progressive NMDs or acquired NMDs that have responded to pharmacologic treatment (e.g., myasthenia gravis or dermatomyositis). Overuse weakness has not been documented with any moderate-resistance strengthening program, and moderate-resistance strength training can increase strength in muscles with an initial Medical Research Council (MRC) grade of 3/5 or better. Strength gain appears to be proportional to the initial strength of the muscle, with the strongest muscles making the greatest gains. Thus, it is logical to institute a strengthening program as early in the course of a progressive disease as possible. The goal of a resistance training program should be to maximize the strength of unaffected or minimally affected muscles to delay the onset of impairment. To ensure safety, patients should be advised to avoid high-resistance eccentric exercise. A practical recommendation is to find a weight that a patient can lift 15 to 20 times comfortably and then ask him or her to perform several sets of 10 lifts each. Patients also should be counseled to reduce their training load if they experience persistent muscle soreness or fatigue after exercise sessions.
In general, patients with NMDs have a normal cardiovascular response to aerobic training. Unless they have significant cardiac or respiratory disease, there are no apparent contraindications to aerobic exercise. The benefits of aerobic training are similar to those in healthy individuals. Patients should select a mode of exercise with minimal risk of injury from falling; for example, in patients with poor balance, a cycle ergometer may be safer than a treadmill. Balance training is a promising form of exercise for patients with a variety of NMDs. In patients with neuropathy, training has been demonstrated to improve balance, and it is hoped that this will, in turn, reduce the risk of falling.
In general, the US Department of Health and Human Services guidelines regarding intensity, duration, and frequency of exercise should be followed ( ). The recommendation for individuals with disabilities is that they adhere to these recommendations to the greatest and safest extent possible. Barriers to clinician prescription of exercise, such as lack of confidence, lack of formal guidelines, and lack of infrastructure, must be addressed ( ).
Orthoses and Mobility Aids
Over time, individuals with NMDs may require orthoses and mobility aids to maximize function and independence. Especially for individuals with rapidly progressive disease, the rehabilitation focus may shift quickly from using exercise to optimize strength and physical fitness to utilizing assistive devices for supporting autonomy.
Orthoses
Orthoses are devices applied externally to the body to provide support, protection, and improved function. They support weak muscles, decrease stress on compensatory muscles, minimize fatigue, prevent deformity, and conserve energy. Orthoses can be prefabricated or individually fashioned. Orthoses are one component of a comprehensive rehabilitation program; orthosis needs must be frequently reassessed, as fit and needs change over time. To promote safety and patient/caregiver comfort, one or two physical therapy sessions can often be helpful for providing gait and transfer training to accommodate new orthoses.
Spinal Orthoses
Weakness of neck extensor muscles, as can occur in inflammatory myopathies, neuromuscular junction disorders, and motor neuron diseases, can result in head drop. Head drop is associated with pain and fatigue, as well as restricted forward gaze and impaired speech, swallowing, and interpersonal communication. In severe neck extensor muscle weakness, the cervical spine can become completely flexed, resulting in substantial pain. Cervical orthoses (collars) can be utilized to mitigate head drop. Table 8.2 lists the routinely used types of cervical orthoses and their indications, including a creatively designed baseball cap orthosis ( ). Fig. 8.1 depicts the Headmaster collar, an example of a commonly used orthosis for the treatment of head drop.
Table 8.2
Cervical Orthoses/Collars
| Collar Type | Examples | Indication | Benefits | Disadvantages |
|---|---|---|---|---|
| Soft | Foam | Mild neck extensor weakness | Comfortable Well-tolerated |
Minimal limitation of neck movement |
| Semirigid or hard | Aspen a Malibu a Miami-J a Philadelphia |
Moderate to severe neck weakness | Limitation of neck flexion and extension | Discomfort Skin breakdown |
| Open air | Headmaster Executive Canadian |
Often the most acceptable balance between stability and comfort | Limited lateral support | |
| Baseball cap ( ) | Can be individually fabricated by a therapist | Good neck extensor strength and adequate cervical spine range of motion | Cosmesis Comfort |
a These collars provide increased sagittal and lateral support, as well as anterior neck access.
The commonly prescribed cervical orthoses can be difficult to fit, overly restrictive, and uncomfortable. Recently, a team of designers, with input from individuals with ALS and head drop, created the Sheffield support snood, a more flexible and adjustable cervical support collar. It consists of a flexible fabric that surrounds the neck with a Velcro seal and has a vertical support element that is placed below the chin. Additional support elements can be added as needed. Emerging research suggests the Sheffield support snood provides both support and flexibility, as well as good comfort and aesthetic ( ) ( Fig. 8.2 ). In preadolescent children with neuromuscular scoliosis, including those with spinal muscular atrophy (SMA), muscular dystrophies, and peripheral neuropathies, including the hereditary motor and sensory neuropathies/CMT disease, thoracolumbosacral orthoses can be used to provide support to the spinal column during growth. Molded seating supports can be used adjunctively for spine support as well. Orthosis use cannot prevent curve progression; if the curve has progressed significantly or seating positioning is compromised, surgery is typically performed at the onset of puberty in those who qualify as surgical candidates. In many individuals, surgery is performed prophylactically in anticipation of curve progression. In those who are not surgical candidates, thoracolumbosacral orthoses and wheelchair modifications addressing seating and arm height can provide stability and comfort.
Upper Extremity Orthoses
Upper extremity orthoses compensate for weakness, position an extremity for comfort and function, and enforce directional control in the treatment and prevention of contractures. Orthoses can be static (to prevent deformity, reduce tone), serial static (to provide stretch), static progressive (to provide stretch), dynamic (to allow restricted motion), or adaptive/functional (to compensate for absent upper extremity function).
Considerations in selecting and fitting upper extremity orthoses include cosmesis, skin protection, extremity positioning, tolerability, and individual functional goals. Tolerability includes comfort and lack of interference with desired hand functions. Grasp is most effective with the wrist in extension and slight radial deviation. Most right-handed individuals write with the wrist slightly extended, whereas left-handed individuals write with the wrist slightly flexed. For maintenance of muscle stretch, it is desirable for joints to be held at the end range of motion for the maximal tolerated duration.
Weakness of proximal upper extremity muscles, as can be seen, for example, in FSHD, Emery-Dreifuss muscular dystrophy (EDMD), proximal myopathies, and motor neuron disorders, can result in glenohumeral joint subluxation, contractures, pain, and diminished function. Although slings cannot always prevent subluxation, they can be used for support and pain relief. Slings can be used in conjunction with appropriate seating and arm rests for individuals who use wheelchairs. Types of slings include the humeral cuff and pouch/single strap. The humeral cuff sling consists of an arm cuff on the distal humerus secured by a figure-of-eight harness. The pouch sling supports the elbow and wrist; however, because this sling holds the upper extremity in adduction, internal rotation, and elbow flexion, it may promote the development of contractures over time.
For individuals with intrinsic hand muscle weakness, wrist-hand and hand-finger orthoses can be utilized. The resting hand splint (wrist-hand orthosis) can be used during the days or at night to maintain muscle length and reduce contracture risk. This orthosis promotes wrist and metacarpophalangeal extension, along with interphalangeal flexion. An anti–claw hand splint can reduce claw-hand deformity and improve grasp by limiting metacarpophalangeal extension of digits four and five.
Individuals with finger flexor (notably IBM) or extensor weakness can use a variety of wrist-hand-finger orthoses to improve grasp and reduce contracture risk. These include the dynamic finger-extension splint for individuals with finger extensor weakness and adequate flexor strength; a volar cock-up splint for those with wrist and finger extensor weakness; and an opponens splint for those with abductor pollicis brevis, extensor pollicis longus, and extensor pollicis brevis weakness. The tenodesis orthosis (wrist-driven prehension orthosis) allows an individual with finger flexor and extensor weakness to create a three-jaw chuck handgrip using wrist extension. Fig. 8.3 depicts several of the orthoses discussed here. Functional upper extremity orthoses can afford individuals with upper extremity weakness increased independence in performing specific daily activities. These orthoses include the universal cuff to compensate for limited hand function and the balanced forearm orthosis to compensate for shoulder abduction weakness. The universal cuff is secured to the hand by an elastic strap and has a pocket that can hold utensils, hygiene tools, and writing implements. The balanced forearm orthosis (also known as a ball bearing feeder) supports the weight of the forearm and arm against gravity and utilizes ball bearings to allow for independent horizontal movement. These movements facilitate manipulation of desktop items and independent grooming and feeding. Balanced forearm orthoses can include adjustable resistance and ROM settings, as well as flexible mounting options.
Nonmotorized passive exoskeletons as well as motor-powered exoskeletons triggered by minimal muscle movement are increasingly being refined and tested, particularly for serving the population of individuals with DMD. Dynamic arm supports with multiple joint control, such as the innovative A-gear, can be worn relatively inconspicuously and comfortably and allow the user to initiate and carry out movement in multiple planes ( ). Fig. 8.4 shows a boy with DMD wearing a prototype of A-gear. Exoskeletal technology can be utilized in both the rehabilitation training setting and in the home, with the focus in both settings generally upon facilitating functional independence for as long as possible.
Rates of use of both passive and motorized upper extremity robotics to support function remain relatively low in the DMD population, with equipment weight, aesthetic, and limitations in replicating natural movement limiting their use. Emerging attention to user assessment, new technologies such as soft (wearable) robotics and eye gaze access, and facilitation of natural mechanics for performing ADLs will hopefully improve state-of-the-art equipment and increase meaningful usability ( ). A recent report described the potential for powered exoskeletal robotic technology to be triggered by surface EMG readings even in late-stage Duchenne, providing optimism that technology may be able to extend functional independence for longer than has generally been thought possible ( ). Further research in this area is warranted.
Lower Extremity
Lower Extremity Orthoses
In NMDs, ankle dorsiflexion, knee extension, and hip flexion weakness can be quite marked. Similar to upper extremity orthoses, lower extremity orthoses are used to compensate for weakness, position an extremity for comfort and function, and enforce directional control. Orthoses should be as lightweight as possible. Cognitive status and upper body strength must be considered in order to optimize ease of use of lower extremity orthoses. The physiatrist, orthotist, and physical therapist collaborate in assessing gait and orthosis needs and in training individuals in the use of the orthoses. Often, a nurse also participates in the care of individuals using orthoses by teaching about and screening for effects on the skin.
AFOs are the most commonly prescribed lower extremity orthoses in adults with NMDs. AFOs are prescribed for individuals with ankle dorsiflexion weakness to optimize safe, efficient ambulation (promote clearing of the toe during swing phase) and prevent ankle plantar flexion contractures. When prescribed for poorly selected candidates, however, AFOs can limit both gait and function. For example, solid-ankle AFOs reduce equinus, yet in children with DMD, for example, equinus gait may be compensatory for weak quadriceps muscles. Particularly in children, impaired gait may be more functional than braced gait. Generally, AFOs can be solid or hinged, static or dynamic and can be modified to accommodate quadriceps weakness, spasticity, and desired function. Often, new or modified shoes may be required to accommodate an AFO’s bulk and shape. Fig. 8.5 depicts examples of commonly used AFOs.
Solid (nonhinged) AFOs include the solid-ankle, semi-solid-ankle, and posterior leaf spring (PLS) AFOs. The standard solid-ankle AFO is made of thermoplastic material and provides maximal static stability in all planes of ankle-foot movement. This AFO encapsulates the posterior calf, with the proximal border 1 to 2 inches below the fibular head. Anterior and posterior trimlines are at the midlines of the malleoli. Because it is a static AFO, it does not allow for any ankle movement in the sagittal plane. This restriction of movement can limit sit-to-stand transfers and stair climbing. As needed, an AFO can be set in a few degrees of plantar flexion to help prevent buckling at the knee or a few degrees of dorsiflexion to limit hyperextension at the knee. If the AFO is set in dorsiflexion, an individual must have sufficient quadriceps control to compensate for rapid knee flexion during the loading phase of gait. Semi-solid-ankle AFOs have trimlines posterior to the malleoli, and although they do not provide as complete ankle support as solid-ankle AFOs, semi-solid-ankle AFOs may be better tolerated than solid-ankle AFOs when used bilaterally.
The PLS AFO is a dynamic AFO, allowing for some flexibility of the anatomic ankle joint in the sagittal plane. The PLS AFO has trimlines posterior to the malleoli and has a narrow posterior calf component. It allows for tibial advancement over the forefoot during the stance phase of gait and for adequate clearance of the foot during the swing phase. However, it does not provide complete ankle stability in other planes of motion or provide firm equinus support. The PLS AFO is indicated for individuals with mild ankle dorsiflexion weakness but limited tone. Hypertonicity and spasticity can diminish the functionality of the PLS AFO by overcoming its flexibility.
Floor-reaction AFOs are solid-ankle AFOs that incorporate pretibial shells that limit tibial advancement during the stance phase of gait, thus reinforcing knee extension and overall gait stability. These AFOs are indicated when quadriceps strength is ≤3+/5 on the MRC scale and knee range of motion is good. Floor-reaction AFOs are not indicated for individuals with structural knee abnormalities. Individuals with poor postural control may need to use canes or other assistive devices along with the floor-reaction AFOs.
As compared with solid AFOs, hinged (or articulating) AFOs allow for easier sit-to-stand transfers and stair climbing. The articulation across the ankle allows for improved anterior displacement of the tibia over the foot during the stance phase of gait. Hinged AFOs tend to be most appropriate for individuals with mild ankle dorsiflexion weakness and fairly preserved quadriceps strength. A 90-degree plantar flexion stop can be added to a hinged AFO to limit ankle plantar flexion in the setting of increased tone. A disadvantage of the hinged AFO is slightly increased weight and greater bulk around the ankle, making it more difficult to find shoes to accommodate it. Adductor spasticity and bilateral hinged AFO use can result in the medial aspects of the orthosis componentry catching, leading to falls.
In individuals with progressive quadriceps weakness, such as those with IBM, even a floor-reaction AFO may provide insufficient support over time. The stance-control knee-ankle-foot orthosis (KAFO) can lock and unlock without user manipulation, thus optimizing gait mechanics. The weight of this orthosis and the training required for its use may prohibit individuals with excessive weakness, fatigue, or cognitive impairment from successfully utilizing the device. Older KAFO designs include those with ratchet locks, drop locks, ball locks (for individuals with poor hand control), and dial locks (adjustable for knee flexion contractures). These older designs are often used by patients with a history of polio and by some boys with DMD but are not practical for those with most other NMDs. They are relatively heavy and require walking with a locked knee, which is not possible in the setting of significant proximal weakness.
Antispasticity features that can be incorporated into AFOs and KAFOs include full foot plates, metatarsal head supports, built-up medial longitudinal arches, plantar flexion stops, and peroneal ridges.
If upper body strength allows, AFO and KAFO use can be accompanied by the use of crutches, canes, and walkers as needed for support and balance.
Lower Extremity Robotics
In the NMD population, lower extremity robotics tend to be used somewhat experimentally, and for gait training more so than for daily home use. This is due in large part to cost and cumbersome nature of use (existing robotics are bulky and limited substantially in use by proximal and upper extremity weakness).
Exoskeletal supported treadmill training, historically utilized in nondegenerative conditions such as spinal cord injury, stroke, and cerebral palsy, has recently been tested in individuals with proximal weakness and gait impairment resulting from LGMD. The repetitive ambulation training seems to be both feasible and to have a positive effect on ambulation endurance ( ). While there are limited data in this area, a recent case report suggests that the combination of conventional rehabilitation therapy and overground exoskeletal supported gait training may have a beneficial impact on gait parameters in myotonic dystrophy type 1 ( ).
Canes, Crutches, and Walkers
Canes, crutches, and walkers can be used with or without orthoses to normalize gait pattern, reduce energy expenditure, and enhance balance, safety, and mobility. These aids can be considered extensions of the upper limbs; therefore, the maintenance of upper limb strength and range of motion can prolong their use. Device selection is based on strength, tone, and range of motion in the trunk and upper and lower extremities; degree of body weight support needed; degree of fatigue present; rate of disease progression; individual desires and goals; and insurance coverage/affordability. Training by a physical therapist on any aid prescribed is recommended.
In general, canes provide the least support for gait stability and can be recommended for individuals with mild lower extremity weakness or balance impairments. Canes can be wooden or aluminum, solid or adjustable height, with one or four points of contact with the ground, and with narrow or wide bases. Grips on handles can be enlarged to accommodate handgrip weakness. A cane should be held in the arm opposite the weakest side and should be fitted for 20 degrees of elbow flexion. One should lead with the stronger limb on flat ground. One should also lead with the stronger limb for ascending stairs and with the weaker limb for descending stairs. Quad canes, which provide four points of contact with the ground, can be of standard or wide base and provide additional stability as compared with standard canes. Different types of canes are shown in Fig. 8.6 .
Crutches provide support from the axilla to the floor. They are indicated for individuals with lower extremity weakness but preserved upper extremity and trunk strength. Lofstrand crutches are typically recommended over standard axillary crutches because they provide a forearm cuff that can free hands for use during standing. Platform forearm orthoses are useful for individuals with elbow flexion contractures or severe hand weakness. Crutch tips and handgrips must be routinely evaluated to ensure integrity and safety. Three types of crutches are depicted in Fig. 8.7 .
Walkers provide greater support for ambulation than canes and crutches. Options for walkers include folding, wheeled, and with brakes. Seating surfaces, baskets, and trays can also be added. When brakes are selected, push-down brakes (engage when body weight is placed over the walker) are preferable to squeeze brakes for individuals with hand weakness. A lightweight wheeled walker with a seat and handbrakes is commonly used by people with ALS early in disease course. Given the rapidity of disease progression, however, once an individual begins to use a walker, anticipatory planning for fall prevention and response, as well as future wheelchair use, should be initiated. Three walkers are depicted in Fig. 8.8 .
Seated Mobility Options
When independent or assisted ambulation is not feasible, seated mobility options can be used to maximize functional independence. These include power scooters, manual wheelchairs, and power wheelchairs. Power scooters should be recommended with caution for individuals with NMDs. Power scooters require good upper extremity and trunk strength, cannot be modified for disease progression, and when covered by insurance, can preclude insurance coverage of power wheelchairs within a several-year time period. Individuals with IBM tend be the largest subset of individuals with NMD who use power scooters.
A manual wheelchair can be used when an individual cannot ambulate long distances independently. Frequently, individuals with NMDs will not be able to self-propel a manual wheelchair due to easy fatigability and the need to conserve energy. For ease of transport, wheelchairs prescribed should be lightweight (<36 pounds) or ultra-lightweight (<30 pounds) and with folding frames rather than rigid frames. Of note, a standard manual wheelchair, such as that used in hospitals, should not be prescribed because it is heavier than these chairs and comes in a more restricted set of seat width, seat depth, and back height options. Standing capability for a manual wheelchair, which can provide weight-bearing and pressure relief, confers limited stability and flexibility for wheelchair modifications and is not typically prescribed for individuals with NMDs. Particularly for individuals with rapidly progressive diseases, such as ALS, a manual wheelchair should be rented or borrowed through organizations such as the Amyotrophic Lateral Sclerosis Association or Muscular Dystrophy Association, because most insurance companies will reimburse for only one wheelchair purchase over the course of several years. Insurance coverage for an eventual power wheelchair should be the priority.
Power-assist wheelchairs provide powered assistance to manually controlled use. They are heavier than manual wheelchairs and do not provide the flexibility of modifications available for fully powered wheelchairs. For these reasons, as well as the considerations described earlier, power-assist wheelchairs are typically not recommended for individuals with progressive NMDs.
When manual wheelchair use is no longer feasible due to weakness or the need for the use of ventilator or other equipment, full-power wheelchairs are used. The transition from manual to power wheelchair use can be psychologically, physically, and logistically challenging. These challenges include psychological adjustment to disease progression, the need to modify previously used methods for performing ADLs and transfers, the need to modify home and work environments, and the need to modify vehicles and typical means of transportation.
Power wheelchairs are divided into three classifications by the . Class A wheelchairs are the conventional nonprogrammable power wheelchairs with basic seating. Class B wheelchairs can be modified based on an individual’s needs in the realms of speed, acceleration, and braking. Class C wheelchairs, the most durable and modifiable, allow for seating, pressure relief, and ventilator modifications. Class C wheelchairs allow for the most flexibility and accommodation for long-term needs.
Specialty wheelchair and seating clinics, often coordinated by physical therapists, can provide expert recommendations to a rehabilitation team regarding optimal individualized wheelchair systems. Seat width, depth, and height, as well as back height and leg rest length, are based generally on the height and size of the user. Componentry for head and neck support (e.g., head rests), trunk support (e.g., lateral supports), seating/cushioning (e.g., molded cushioning to accommodate orthopedic abnormalities), pain and pressure relief (e.g., tilt-in-space or recline functionalities), upper and lower extremity support, and seatbelts can be individualized based on patient needs. Flexibility for adding items such as trays, ventilators, and communication or other equipment must also be specified.
Final factors that must be specified are type of drive and user-wheelchair interfaces. Wheelchairs can be front-, mid-, or rear-wheel drive. Front-wheel drive chairs navigate bumps and curb cuts well but do not track straight consistently. Mid-wheel drive chairs have the smallest turning radius and can negotiate some outdoor terrain. Rear-wheel drive chairs have the most consistent straight tracking but have a large turning radius and are most appropriate for patients who are heavy outdoor users. Many factors go into drive selection. Because most homes were not built to accommodate wheelchairs with large turning radii, mid-wheel drive chairs are often utilized to facilitate use in the home.
The user-wheelchair interface refers to the means by which a user controls their wheelchair. Interfaces include the joystick, sip-and-puff mechanism, head array switch, voice control, and eye gaze control. Joystick selection includes several features: proportional versus switched control, mounting site (joysticks can be operated by nearly any body part), and shape. The sensitivity of the input device must be programmed to match the user’s capabilities. The sip-and-puff mechanism is particularly useful for individuals with SMA, who retain strong respiratory systems while losing significant extremity strength. Eye gaze control can be valuable for individuals with advanced ALS. Importantly, eye gaze control requires substantial training time and cognitive capacity. These factors need to be anticipated in advance.
Integrated controls are also available—for these, a single input device, such as a joystick, can be toggled between controlling the wheelchair and controlling other electronic devices in the home.
Wheelchair features can be designed to accommodate weakness, spasticity, contractures, and anticipated medical and functional needs. Allowing an individual to personalize a wheelchair through choice of a esthetic design features such as color is also recommended.
The process of obtaining a power wheelchair through insurance requires multiple steps, including detailed physician documentation of need. It is recommended that a prescriber review each patient’s insurance company requirements prior to initiating a wheelchair prescription. Typically, in order for a patient to qualify for a powered mobility device, the prescribing physician must document why a manual device is insufficient, that the device is required for home-based mobility-related ADLs (insurance does not cover mobility devices for activities out of the home, including medical appointments; the mobility device must be required to facilitate the performance of typical ADLs in their typical location, e.g., bathing in a bathroom), that the individual receiving the wheelchair has expressed willingness to use it, and that the individual has the cognitive capacity and supports to be able to use it ( ). It can easily take 4–6 months from the time of prescription for an individual to receive a power wheelchair.
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