REHABILITATION

REHABILITATION

EXERCISE PARADIGMS TO IMPROVE STRENGTH

Skeletal muscle weakness is the ultimate cause of most clinical problems associated with NMDs. A number of well-controlled studies have documented the effect of exercise as a means for patients to gain strength in NMDs, although much remains to be learned in this area.

In slowly progressive NMDs, a 12-week moderate resistance (30% of maximum isometric force) exercise program resulted in strength gains ranging from 4-20%, without any notable deleterious effects. However, in the same population, a 12-week high-resistance (training at the maximum weight a subject could lift 12 times) exercise program showed no benefit over the moderate resistance program, and evidence of overwork weakness was found in some of the subjects.

In a study comparing CMT to MMD, the only patients who appeared to benefit significantly from a strengthening program were the patients with CMT. The patients with MMD showed neither beneficial nor detrimental effects. This clearly demonstrates that the most effective exercise regimens for patients with neuropathies and myopathies most likely vary, although further investigation is needed.

In rapidly progressive disorders like DMD and ALS, active ongoing muscle degeneration occurs, and the risk for overwork weakness and exercise-induced muscle injury is much greater. In this population, exercise should be prescribed with caution and a common sense approach.

Studies have compared mdx mice (mice lacking dystrophin) to normal control mice. The mdx mice are genetically homologous models of DMD. In voluntary running protocols, dystrophin-deficient muscle is clearly susceptible to exercise-induced muscle injury, particularly eccentric (lengthening) muscle contractions.

Interestingly, mdx mice show considerable avoidance behavior for exercise compared to normal mice. This may be an intuitive survival strategy. Following ad libitum exercise on a flywheel, the extensor digitorum longus and soleus muscles of adult mdx mice significantly weakened. In addition, histochemical evidence showed considerably more damage to the exercise-weakened muscles compared to control nonexercised mdx muscles.  

Considering the results from the animal studies and the available human studies, all patients with NMDs should be advised not to exercise to exhaustion because of the risk of exercised-induced muscle damage. Patients with NMDs in exercise programs should be monitored for signs of overwork weakness.

This includes excessive delayed onset muscle soreness. This usually occurs 24-48 hours following exercise. Other warning signs include severe muscle cramping, heaviness in the extremities, and prolonged dyspnea.

Submaximal, low-impact aerobic exercise (walking, swimming, stationary bicycling) improves symptoms of fatigue via enhancement of cardiovascular performance and increased muscle oxygen and substrate utilization. This is important because fatigue is a significant limiting factor in physical performance in patients with NMDs.

Fatigue in this setting is likely multifactorial because of deconditioning and impaired muscular activation. Improving cardiopulmonary performance through aerobic exercise improves not only physical functioning but also mood state and helps fight depression.

Patients with NMD have been noted on the Minnesota Multiphasic Personality Inventory as having a higher frequency of depression than healthy populations. Aerobic exercise also helps achieve and maintain ideal body weight and improve pain tolerance.

In terms of monitoring progress in an exercise program, a number of reliable, functional assessment tools have facilitated assessing the effectiveness of exercise interventions, including the Timed Motor Performance assessment, which is a useful and simple measurement scale that can be used during routine clinic visits. In terms of testing static muscle strength, manual muscle testing has been shown to be unreliable in patients with NMDs.

A hand-held myometer or MicroFET type of strength measuring device is far more reproducible and just as easy to use in a clinical setting. Although very reliable, quantitative isokinetic strength testing requires too much sophisticated equipment to be useful in clinic. However, this is a good choice for research purposes.

Despite all the benefits, exercise does create some clinical problems. Muscle cramping is common in patients with NMD because of sarcolemmal instability and is often exacerbated by exercise. True muscle spasms, related to upper motor neuron spasticity, are also seen in ALS. A number of pharmaceuticals may help treat muscle spasms.

Baclofen is a good first choice because it acts via motor neuron inhibition at the spinal cord level. Tizanidine and gabapentin may also be helpful in this situation. Gabapentin would be a good choice if neuropathic pain were also present.

Benzodiazepines (or other centrally acting muscle relaxants) are not recommended because of the risk of respiratory suppression. Dantrolene is contraindicated because of its mechanism of action (impairing excitation-contraction coupling), which produces too much muscle weakness to be used in patients with NMDs.

Mexiletine is particularly useful in myotonia congenita, but cardiac conduction must be monitored while this drug is being used. Nonballistic sustained muscle stretching is also helpful and should be routinely performed after exercise.

MANAGING NEUROMUSCULAR CONTRACTURES AND SCOLIOSIS: STRETCHING, BRACING, AND SURGERY

Joint contractures and scoliosis are major clinical problems in NMDs, particularly in patients with DMD and SMA II. A routine examination of the spine and major joints in patients with NMDs should be performed during each clinic visit.

Contractures appear to be related to prolonged static limb positioning. Contractures frequently develop shortly after the patient becomes wheelchair dependent. Several studies have documented that a lack of lower extremity weight bearing and wheelchair dependence contributes to the development of contractures.

In ambulatory patients, upper extremity contractures may occur and can be complicated by joint subluxation, particularly in the shoulder girdle. Slings may help provide support but will not prevent contracture formation.  

Again, stretching and positional splinting may slow the progression of contractures, although the actual effectiveness of this has not been well studied or documented in the literature.

Surgical release of contractures in the lower extremities may allow a patient to be functionally braced. This may prolong ambulation, although a number of studies have shown that weakness, not contractures, contributes most to the loss of functional ambulation.

In terms of scoliosis, an etiologic relationship does not appear to be associated with the loss of ambulation. Although scoliosis and wheelchair dependence are age-related phenomena, several studies have shown no relationship between the 2. One large study by Lord and colleagues reported an almost 4-year difference between wheelchair dependency and the onset of significant scoliosis in patients with DMDs.

Indeed; many patients with DMD and SMA II develop scoliosis before they become wheelchair dependent. Disease progression with increasing weakness of trunk musculature is more likely the major underlying cause of neuromuscular scoliosis.

However, trunk flexor or extensor strength is very hard to measure quantitatively. In NMD patients, scoliosis did not appear to correlate with trunk strength assessed by manual muscle test, although this method is not capable of measuring asymmetric strength and, as discussed earlier, has not been shown to be a reliable method of strength testing in this population.

Patients with DMD typically develop scoliosis around the time of the adolescent growth spurt. However, patients with SMA II may develop scoliosis much earlier. In DMD and SMA, studies have shown that thoracolumbar curves are much more common than lumbar curves. Patients with DMD and SMA should be monitored closely with serial radiographs because the curve may suddenly progress.

An important note is that spinal bracing has not been shown to be effective in preventing progression of neuromuscular scoliosis, although most of the studies were performed involving patients with SMA.

Thus, spinal instrumentation and fusion is the only known, effective treatment option. This should be performed before the primary curve exceeds 25° and the forced vital capacity has not dropped below 50% of predicted.

Complications substantially increase if the patient already has compromised breathing, although, unfortunately, correction of the scoliosis with fusion has not been shown to improve pulmonary function.

Nonetheless, fusion does improve QOL by facilitating positioning, seating, and transfers. If the curve progresses much beyond 40°, successful correction via fusion is much less likely.

For the extremities, the goals of bracing should be to improve function and joint stability. Long leg bracing to prolong ambulation time in DMD has been one of the better-studied uses in NMDs. A number of studies have shown that ambulatory ability may be prolonged by up to 2 years with the use of long leg braces and appropriate contracture release.

However, whether this represents a subset of patients with a slower disease progression and relatively less weakness is unclear. Further, no clear association exists between prolonging ambulation with long-leg bracing and delaying or decreasing scoliosis in patients with DMD. If bracing is used, a long leg brace or knee-ankle-foot orthosis is generally needed because of the amount of weakness in hip and knee extension as well as ankle plantar flexion and dorsiflexion.

Most patients with CMT require short leg braces or ankle-foot orthoses. These are best when they are custom made with a lightweight polymer (polypropylene or carbon fiber). They should fit intimately to avoid skin problems and to provide good stability. If a pressure sore occurs, the brace should be removed until the patient heals.

Double metal upright ankle-foot orthoses may be built into the shoe but are usually too heavy and may limit ambulation. If the ankle is significantly unstable, the braces should be high profile (come around in front of the malleoli). Pes cavus and hammertoe deformities can be accommodated with built-up arches and metatarsal bars.

Patients with CMT and other sensory neuropathies are at very high risk for skin ulcers and neuropathic arthritis (Charcot joint). Thus, skin integrity and joint stability should be checked during every clinic visit.

Any patient with weakness due to an NMD may benefit from bracing depending on the distribution of weakness, gait problems, and joint instability. The decision to brace should include the risk of the brace's added weight and the willingness of the patient to use the brace.

Patients with NMDs should be referred for a course of physical therapy after being fitted with braces to help them learn to use the devices effectively.

VOCATIONAL, PSYCHOSOCIAL, AND QUALITY OF LIFE ISSUES

Patients with NMDs, particularly those with advanced ALS and DMD, may experience reactive clinical depression. As noted previously, studies involving patients with NMDs have shown elevated scores for depression on Minnesota Multiphasic Personality Inventory testing.

In one study, depression was more closely associated with the level of independent functioning than with limb strength. Thus, good family, social, and religious support systems are critical.

Other family members and caregivers may also become depressed, and this should not be overlooked. Group and family counseling may be beneficial.

Patients with NMDs should be referred to support groups, which are also excellent resources for psychological support and problem solving. If necessary, a patient should be referred to a mental health professional. Antidepressant medicine may also help with mood elevation and may improve appetite and sleep. In patients with ALS, tricyclic antidepressants with significant anticholinergic activity dry up oral secretions. This can help minimize drooling.

Significant cognitive involvement is common in patients with MMD and some congenital mitochondrial myopathies. Learning disabilities are also seen in about one third of boys with DMD. Beyond that, most people with NMD show normal intelligence. Unfortunately, employment rates for people with NMDs are significantly lower than for the able-bodied population. In the NMD population, a higher level of education correlated more closely with employment rate than with functional level or physical performance.

The self-esteem levels noted on personality testing also correlated positively with the level of education and employment. This implies that altered personality profiles in patients with NMDs may be a significant factor concerning their ability to integrate into mainstream society and to hold steady employment rates. In this regard, education appears to be at least as important as physical abilities with respect to employability and self-esteem in people with NMDs.

Individuals who have NMDs are incredibly diverse. This may be why very few QOL studies have been conducted to determine the effect of a NMD on QOL. Studies that have been performed have been criticized because many differing NMDs were lumped together in a poorly defined study group and the studies predominately used generic instruments to define QOL.

Thus, they rarely used clinically meaningful data on physical and emotional functioning. Instead, they focused on the extreme manifestations, such as severe pain, rather than looking at how patients experience and deal with their NMD.

Some disease-specific QOL assessment tools, most notably the NeuroQOL and the Amyotrophic Lateral Sclerosis Assessment Questionnaire (ALSAQ-40), among others, have been developed specifically for NMD patients.

These disease-specific measures are especially useful in differentiating QOL and psychosocial functioning of patients as their NMD progresses. Beyond ALS, there has been a dearth of studies using QOL measurements to study NMDs. This is an area that greatly warrants further investigation.

EQUIPMENT

Proper equipment can significantly improve QOL for a patient with an NMD. Common examples of equipment include hospital beds, commode chairs, wheelchairs and wheelchair ramps, handheld showers, bathtub benches, grab bars, raised toilet seats, among many others. An occupational therapist is best qualified to help determine if any of these devices would be useful for a patient with an NMD.

Wheelchairs are a critical component of mobility for people with NMDs. Wheelchairs need to be fitted appropriately with the right frame size, type of seat, lumbar support, and cushioning to avoid pressure ulcers.

The wheelchair should be equipped with other mechanical accessorial devices such as tilt ability to provide comfort and to protect the skin. A physical or occupational therapist should evaluate the patient to ensure proper wheelchair prescription.

Patients who are simply given a prescription for a wheelchair frequently get a chair that does not fit properly or have the proper components. Power wheelchairs are indicated for most patients with NMDs who can no longer ambulate. These patients do not have enough upper extremity strength to propel a manual chair by themselves.

Although expensive, power wheelchairs can be justified to third party payers on the basis that they help prolong independent mobility, thus decreasing medical and psychological comorbidity.

In patients who can still ambulate, walkers or quad (4-point) canes help reduce the risk of falling.

Pressure-relieving mattresses, along with foam wedges for proper positioning, help prevent pressure skin ulcers. In some patients with NMDs, particularly ALS, severe weakness in the neck musculature causes neck pain and muscle spasms.

A cervical collar, particularly the Freeman or Headmaster type, which is a wire-frame collar with padding over the pressure points, may be very helpful.

In patients with dysarthria, typically patients with ALS, augmentative communicative aids, including an alphabet board, word board, or computer based speech synthesizer, can be very helpful to maintain functional communication. A speech language pathologist is best qualified to determine which, if any, of these devices would work best.