Neuromuscular Rehabilitation of CMT (continued)

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Cardiac Considerations

Although cardiac arrhythmias are rarely a problem in young neuromuscular patients, they can be life-threaten-ing in those with Emery-Dreifuss muscular dystrophy who require close monitoring and possibly chemical treatment even during the ambulatory stage. Cardiac monitoring can usually be empirically delayed until the stage of wheelchair dependence.

Nutritional Considerations

Under-nutrition results from the inability to feed oneself, swallowing impairments, shortness of breath, aspiration of food, the presence of an indwelling tracheostomy tube, decreased appetite due to bowel disturbances, restrictions of food textures and flavors, and impairment in taste, especially in those receiving tracheostomy and intermittent positive pressure ventilation (IPPV) (29).

Patients should be weighed regularly and weight changes considered in the context of their diseases. As little as a 10% loss of ideal weight can be associated with loss of physiologic adaptability and increased morbidity (30). This is particularly true in patients with impaired pulmonary defense mechanisms. Food deprivation impairs respiratory muscle function by reducing available energy substrates. Diaphragm isometric strength (31,32), endurance, maximum static inspiratory and expiratory pressures (31,32), and maximum voluntary ventilation decrease during a fast (32), as does hypoxic (33,34) and hypercapnic (35) ventilatory drive. Ventilatory failure can also occur with chronic starvation. Rats restricted to a third of their normal caloric intake for 6 weeks developed emphysema-like lung changes (36), similar to the lesions found in starved individuals from Warsaw ghettos (37). Malnutrition impairs cell-mediated and humoral immunity (38,39) and alveolar macrophage phagocytic activity (40,41) and increases bacterial adherence to the lower air-ways in patients with tracheostomy tubes (42). In addition, deficiencies in specific nutrients can affect respiratory function.

Obesity may be a complicating factor and can compromise ventilatory dynamics. However, by the time a patientrequires a ventilator, severe weight loss and undernutrition often supervene. The average weight of a DMD patient at the time of ventilator use was 70 pounds (43). The serum albumin and transferring levels reflect the protein synthetic ability of the liver. Both have half-lives of just under 2 weeks; therefore, the serum levels reflect long-term, not short-term, changes in protein status. Retinol-binding protein and prealbumin are more useful for assessing short-term nutritional status because of the shorter half-life of 12 hours and 2 days, respectively (29). Other useful tests include total iron-binding capacity and serum vitamin A, C, and E levels.

Food intake can be assessed by use of a diet diary to compare calorie and nutrient intake with ideal quantities. However, the ideal intake levels of inactive patients differ from those in the general population. The following equation calculates the daily recommended caloric intake of children with DMD: Kcal = 2,000 - age (years) x 50 (44). For advanced DMD and other patients with neuromuscular disease, caloric needs may not exceed normal resting energy expenditure, estimated to be 110% of the basal metabolic rate. Patients commonly go from being able to eat foods of all consistencies to soft or pureed foods and later to high-calorie thick liquid nutritional supplements. Patients should be referred for gastrostomy when they can no longer be fed without aspiration, especially when there are signs of chronic undernutrition and arterial oxyhemoglobin desaturation due to aspiration of upper air-way secretions.

Stage of Wheelchair Dependence

Scoliosis Prevention

Severe scoliosis develops in virtually all patients with SMA type I and II, in up to 90% of patients with DMD (45), and in many other childhood-onset neuromuscular disorders. The higher the plateau VC, that is, the highest VC ever attained by the patiient, the less likely is the development of scolosis and the longer one can wait before intervening. (46)

The usual indication for scoliosis-reduction surgery is a curvature of the spine of 40 or more I a patient who has failed thoracollumber bracing and in whom cardiopulmonary foundation is adequate enough for reasonable safe intervention Although this is appropriate for many patients with neuromuscular diseases. Wheelchair seating modifications and thoracolmbat bracing are useful in delaying sugianl intervention in those with infantile SMA but should be avoided in patients with DMD, the delay in intervention until a curvature 40 is obtained is usually associated with in adequate pulmonary function (Fig.2) (48). In a third patient with DMD and a relatively low plateau VC, waiting until the scolottic curve attains 40 results in diminution of the VC to under 30 of predicted normal surgical intervention (48).

Scolosis develops early in childhood in patients with SMA. The most common approach to limit progression of their irreversible curvature is by total contact plastic thoracolumbar bracing to allow normal early vertebral growth followed by spinal inssstrumentation and fusion after age 6 (49-51). Failure to prevent scoliosis results in a variety of sequelae: loss of the ability to sit because of the protrusion of the ribs into the abdominal wall, loss of balance and comfort when seated, the need for complicated and expensive seating modifications and custom seating systems, low back pain, compressive lumbar radiculopathies, ischial discomfort and skin breakdown,inability to use an intermittent abdominal pressure ventilator for ventilatory assistance (52), and hindrances in the use of mobile arm supports for self-feeding (53).

During the stage of wheelchair dependence, the presence of an excessive spinal curvature and the vital capacity should be monitored at 6-month intervals and surgical intervention recommended (48,54-57). Some investigators recommend prophylactic intervention in all patients (57). We recommend that DMD patients with a plateau VC below 1,500 mL undergo surgical intervention as soon as they are wheelchair dependent and have any pelvic obliquity A plateau VC of 1,500 to 2,000 ml and a curvature of 20 to 40° are also indications for intervention. Patients with a plateau VC of more than 2,000 ml can safely delay intervention until the curve reaches 40°.

Of the surgical approaches to reduce scoliotic curves, some, but not all, include spinal fusion. Perhaps the idea lmethod is not yet in general practice (46). Spinal fusion methods should be used for definitive interventions in all patients with DMD and nonfusion methods reserved for interventions deemed temporary as for SMA children under age 6.

FIG. 2. This plot of vital capacity (VC) vs. degree of scoliosis over time for boys with Duchenne muscular dystrophy with low plateau VCs (about one third of Duchenne patients VCs plateau below 1 600 mLbefore14 years of age shows that by the time scoliosis reaches 23°, the VC has decreased to 40% of predicted normal, thereby increasing the risk of general anesthesia and preoperative pulmonary complications. The safe surgical window is presented (between the solid lines).

Prevention of Cardiac Complications

Holter monitoring should be performed on a regular basis in conjunction with other standard studies of cardiac function such as chest radiographs, electrocardiography, and either echocardiography and radioscintigraphy scanning in patients with Emery-Dreifuss muscular dystrophy because they can have life-threatening cardiac arrhythmias, even in the presence of normal cardiac ejection. There is little, if any, evidence that cardiac arrhythmias pose a serious risk in patients with other dystrophies or myopathies, except of course whenthe jection fraction is severely diminished, indicative of advanced cardiomyopathy.

Neuroendocrine activation is triggered by congestive heart failure (58). Measurements of plasma atrial natriuretic peptide (59-63) and norepinephrine are useful for estimating the severity of dilated cardiomyopathy and congestive heartfailure (64,65). Norepinephrine concentrations have been shown to be an independent predictor of prognosis for patients with congestive heart failure (64,65). Atrial natriuretic peptide levels, normally about 10 pg/mL in young adults, increase as a function of cardiothoracic ratio and with the ratio of the preejection period to left ventricular ejection time. Atrial natriuretic peptide concentrations increase in DMD patients once left ventricular ejection fractions decrease to under25% (66). Most such patients have a poor prognosis despite effective use of respiratory muscle aids. Thus, norepinephrine and atrial natriuretic peptide concentrations are useful for evaluating heart failure and monitoring treatment. Trials of the use of the angiotensin-converting enzyme inhibitor captopril, and hydralazine in the treatment of patients with severely decreased ventricular function, with or without congestive heart failure, demonstrated significant improvements in left ventricular ejection fraction and neuroendocrine levels (67). Patients with severe left ventricular dysfunction are at risk for developing mural thrombi and embolic complications that should be managed by anticoagulation. The correction of chronic hypercapnia with the use of inspiratory muscle aids is useful in reversing cor pulmonale and right ventricular failure.

Facilitation of Activities of Daily Living

Arm Function
Arm weakness parallels leg and diaphragm weaknessin patients with neuromuscular disease. For example, by age 13 the strength of arm muscle group in patients withDMD was only 4% of normal (68). Affected patients lose the ability to feed themselves by late adolescence when substitute movements, like flexing the trunk to meet the hand, balancing the forearm on the tip of the elbow, using objects as levers for the forearm, and using the fingers to crawl up the opposite arm, no longer work. A variety of mechanical systems can be useful for self-feeding, including an overhead sling counterweight and motorized system of arm suspension (68) and a ball-bearing forearm orthosis or mobile arm support (69); however, the latter requires adequate elbow flexor strength (69). When these are no longer adequate because of progressive weakness, finger-operated robotic arms mounted on a wheelchair (Fig. 3) (70,71), finger controlled motorized wheelchairs, and environmental control systems permit paients to continue to feed themselves and perform many other upper extremity activities.

Other useful adaptive aids include long-handled combs, brushes, sponges, toilet paper holders, and shoe horns; flexible shower hoses; shower-tub transfer seats; grab bars; elevated toilet seats; bedside commode chairs; hospital beds; dressing and kitchen aids; and lifts (72). The latter can be useful for transfers and to facilitate bowel evacuation. For example, the patient is placed onto a lift with a seat that has a central cutout area, as is the case with many lift seats. The buttocks are slowly lowered almost to the commode, and with the feet on the floor, the legs are placed into an abdomen-bowel evacuation posi- tion, and time is greatly reduced. Condom drainage systems can increase independence. The need for the frequent turning of severely disabled patients in bed at night can be eliminated by use of a bed that slowly turns the patient from side to side (Motion Bed, J.H. Emerson Co., Cambridge, MA). The home visit of an occupational therapist can aid the physician in prescribing the devices and home modifications that are most useful. With the use of assistive devices, many neuromuscular patients have gone on to achieve professional educations and gainful employment (73).

Fig. 3. Duchenne muscular dystrophy patient using a robot manipulator to perform electronic work.

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