Muscular Dystrophy: How Should It Be Treated?

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Chapter 42 Muscular Dystrophy: How Should It Be Treated?

Improvements in healthcare have resulted in longevity for patients with muscular dystrophies. Until a cure is found, therapeutic and supportive care is essential in preventing complications and improving the affected child’s quality of life (QOL). This chapter reviews the available evidence from a surgeon’s perspective to guide in the management of this condition.

STEROID THERAPY

Currently, corticosteroids are the only class of drug that has been extensively studied in this condition. In 1989, a large, multicenter, randomized, placebocontrolled study in the United States showed an unequivocal improvement in muscle force with prednisone in patients with Duchenne muscular dystrophy (DMD), and that a low-dose (0.75 mg/kg) daily regimen was as effective as the standard 1.5 mg/kg.¹ The improvement in muscle force seemed to be fairly rapid, within a matter of weeks, and followed by a plateau. However, the substantial side effects, particularly weight gain, weighed heavily against the potential benefits, and the authors recommended further research regarding use of steroids as a long-term therapy for muscular dystrophy. After the initial trial, another randomized study examined the use of alternate dosing regimens, and duration of therapy was reported.² Although many studies provided Level III and IV evidence,³^–⁸ they showed that use of a relatively high dose of deflazacort resulted in long-term maintenance of pulmonary function, and the age at which boys became full-time wheelchair users increased by several years over boys who did not take deflazacort. Some debate remains as to the exact dosage regimen (daily vs. alternative schedules) of steroids to compare both efficacy and adverse effects.^9,¹⁰ Long-term steroid effects on quality and length of life are not yet known. Nevertheless, current Level III and IV evidence suggests that all boys with DMD should be given the opportunity to start these medications early in their disease course, well before they reach the stage of full-time wheelchair use.

NECK HYPEREXTENSION

Neck hyperextension with progressive increase of lordosis associated with a limitation in flexion of the cervical spine forces these patients to assume awkward compensatory postures to maintain balance and level vision, worsening their QOL significantly. Level IV evidence suggests posterior interspinous cervical fusion in seven patients led to a better sitting position, to easier nursing, and better cosmesis.¹¹ The mean angle between C2-C7 decreased from an average of 30 degrees before surgery to an average of 19 degrees at 1-year of follow-up. Clinically, these patients had more control over their head position after surgery.

SHOULDER

Orthopedic intervention for the shoulder is mainly confined to fascioscapulohumeral dystrophy. Surgical indications that have been described include inability to abduct or elevate arms and loss of power with inability to hold arm sustained in abduction and elevation. As the muscles stabilizing the scapula become involved, the scapula starts to wing, leading to issues with cosmesis and problems with garment wear particularly in female patients.¹² Surgery should be performed only if the deltoid strength is 4/5 or better. Furthermore, although improvement in appearance and diminution of pain and fatigue can be maintained over the long term, the gains in motion may be lost over time.

Scapulothoracic Fusion

Copeland and colleagues ¹² reported Level IV evidence with average 16-year follow-up period (range, 14 months to 44 years) of scapulothoracic arthrodesis in patients aged 16 to 35 years. From the 13 initial patients (20 fusions), 10 patients (14 shoulders) were available for long-term follow-up. Complications included pleuritic pain (resolved spontaneously within 1 week), hemopneumothorax (requiring drainage), rib and scapula fractures, screw pullout, and painful nonunion requiring revision surgery. These patients had an average flexion of 123 degrees and an average abduction of 103 degrees. All patients eventually had improved function, activities of daily living, and cosmesis.

Diab and coauthors ¹³ report their Level IV evidence of 11 scapulothoracic arthrodesis in 8 patients with adolescent and infantile forms of fascioscapulohumeral muscular dystrophy. They fused the scapula to the thorax in 25 degrees of abduction using 16-gauge wires, a plate, or washers on the posteromedial scapular surface to prevent wire pullout and iliac crest autograft. In all cases, scapular winging and shoulder fatigue and pain initially were eliminated. Active abduction and forward flexion improved to an average of 145 and 144 degrees, respectively. At 6.3 years after surgery, seven shoulders retained motion, whereas four lost motion because of progressive weakness of deltoid with no evidence of failure of the arthrodesis. No short- or long-term respiratory compromise was reported.

Scapulopexy

Scapulopexy has been proposed as an alternative to theoretically avoid the problems of reduced respiratory function, and the shoulder can be mobilized almost immediately after surgery, reducing the risk for muscle atrophy and complications such as stress fractures and nonunion. Giannini and coworkers ¹⁴ have reported their case series (Level 4 evidence) with 9 patients (18 shoulders). The scapula was repositioned over the rib cage and fixed to the ribs with metal wires. Arm abduction increased from an average of 68 degrees before surgery to 96 degrees after surgery. Arm flexion increased from an average of 57 degrees before surgery to 116 degrees after surgery. The position of the scapula obtained at the time of surgery was maintained, and the patients had satisfactory cosmetic results at 9.9 years of follow-up. This technique does not require grafts and reduces postoperative complications such as pneumothorax or hemothorax.

SPINE

Steroid Treatment and the Development of Scoliosis

Alman and researchers ¹⁵ reported Level 2 evidence showing that steroid treatment slows the progression of scoliosis in male patients with DMD. This was a nonrandomized, comparative study with 7- to 10-year-old boys who were able to walk. Thirty patients were treated with deflazacort (treatment group), and 24 were not (control group). Patients were matched for age and pulmonary function at baseline, and were managed for at least 5 years. A curve of 20 degrees or greater developed during the follow-up period in 16 (67%) of the 24 patients in the control group, but in only 5 (17%) of the 30 patients in the treatment group. Fifteen of the 24 patients in the control group underwent spine surgery, at a mean age of 13 years, whereas only 5 of the 30 patients in the treatment group underwent spine surgery, at a mean age of 15 years. Kaplan–Meier analysis demonstrated a significant difference between the two groups with regard to development of scoliosis of 20 degrees or more (P < 0.001). Adverse effects with steroids included cataract (10 patients, none of which interfered with visual acuity or required surgical treatment), stress fractures (3 patients treated with immobilization and/or rest), and weight gain (patients in the treatment group weighed a mean of 3.7 kg more than did those in the control group). Because the families rather than the physician chose the treatment, there may be an inherent selection bias because it is possible that the families who saw more physical deterioration in their child decided against steroid treatment, resulting in the selection of a less severely affected treatment group. These patients were continued on steroid therapy even while the patients were using the wheelchair full time. The future of spines of these patients once skeletal maturity is reached is currently unclear and warrants further study.

Prediction of Spinal Deformity

Several studies have shown that scoliosis develops in almost all patients with DMD, with the exception of those who have a stable, hyperextended spine.¹⁶^–¹⁸ The progression of spinal deformity leads to a deterioration in pulmonary function in patients with DMD. Yamashita and colleagues¹⁹ reported a case series (Level IV evidence) showing the correlation of age at and value of the plateau of vital capacity (VC) with the severity of progression of spine deformity. They show in a retrospective study of 36 patients that rapid and severe progression of spinal deformity could be expected in patients whose VC plateau was less than 1900 mL and in those in whom it occurred before age 14 years.

To further refine their criteria, Yamashita and colleagues ²⁰ published their results on a cohort of 11 patients (Level IV) using multiple discriminant analysis on the basis of 4 predictors: (1) VC at age 10 years, (2) age at which ambulation ceased, (3) curve pattern of spinal scoliosis, and (4) Cobb angles at age 10 years. In these 11 patients, multiple discriminant analysis correctly predicted the severity of the clinical course of 91.7% of patients with DMD. VC at age 10 was found to be the strongest predictor among the variables. These patients could be identified earlier on as candidates for surgical intervention of spinal deformity.

Surgical Management

Spinal fusion surgery with instrumentation remains the mainstay of treatment for patients with DMD with scoliosis. Cheuk and investigators ²¹ reviewed the available evidence in the literature for spinal surgery in patients with DMD. They evaluated publications from 1861 to January 2006, and because there were no randomized or quasi-randomized clinical trials to evaluate the effectiveness of scoliosis surgery in patients with DMD, they were unable to make any evidence-based recommendation for clinical practice. They recommend that patients should be informed about the uncertainty of benefits and potential risks of surgery for scoliosis.

The potential advantages of spinal surgery described in the literature are to obtain and maintain sitting balance and correction of pelvic obliquity to preserve the ability of the patient to be mobile in a wheelchair for the remainder of his life. In addition, cosmetic improvement, no need for orthopedic braces, easier nursing care, and pain relief are other mentioned factors. Nevertheless, the effects of spinal surgery on respiratory function and life expectancy are still controversial. Velasco and coauthors ²²

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