Complications
The most common cause of morbidity and mortality for patients with progressive generalised muscle weakness results from progressive weakness of respiratory muscles. The respiratory muscles include the inspiratory muscles, expiratory muscles (also used for coughing), and the bulbar-innervated muscles (needed to protect the airway).
The inspiratory and expiratory muscles can be entirely supported by the use of respiratory muscle aids, non-invasive ventilation, and mechanically assisted coughing.[29][40]
There are no non-invasive physical medicine interventions to support the bulbar-innervated muscles, but dysfunction of these muscles does not result in the need for tracheotomy for any patients with muscular dystrophies or other myopathies.
Loss of ambulation results from a combination of limb weakness and musculotendinous contractures.
Provision of motorised and back-up standard wheelchair with ventilator trays and tilt-in-space or full reclining capacity (for adults), removable arm rests, and swing-away removable leg rests is indicated once ambulation becomes precarious.[10] A trial of a standing motorised wheelchair may be appropriate.[52]
Osteoporosis and vertebral compression fractures are common in patients taking regular corticosteroid therapy. Evidence to guide treatments to prevent or treat corticosteroid-induced osteoporosis and reduce the risk of fragility fractures in children and adults with DMD is limited.[111] It is recommended that intravenous bisphosphonate therapy is started when signs of bone fragility (low-trauma fractures of long bones or vertebrae) are evident on spine radiographs. The dose may be reduced, or therapy stopped, when bone health is clinically stable.[29]
Weight loss and malnutrition may be caused by dysphagia, which should be assessed by a speech and language therapist. Placement of a gastrostomy tube for nutritional supplementation may be needed.[10]
Patients with DMD and Becker muscular dystrophy have normal sex drives, but access to sexual exploration is limited by severe physical disability.[30] Patients with sexual partners can benefit from the use of rocking beds. By permitting the adjustment of frequency and amplitude of bed motion it is possible to vary the intensity of the sexual experience.[112]
Impaired growth is common in patients with DMD, and exacerbated by corticosteroid treatment. It is recommended that height is measured every 6 months until the patient has been through puberty and reached their final height. Patients with a decline in growth trajectory may need to be referred to an endocrinologist. Evidence about the effectiveness of treatment with human growth hormone in patients with DMD is limited, and there are potential risks (e.g., possible negative effect on muscle function).[10]
Delayed puberty may occur as a result of corticosteroid treatment. Boys showing absence of pubertal development by 14 years should be referred to an endocrinologist for diagnostic tests to confirm a diagnosis of hypogonadism. Standard of care is testosterone replacement therapy.[10]
Constipation is common in people with DMD, but is often under-diagnosed and under-treated.[114] Risk factors include decreased colonic transit time, immobility, abdominal muscle weakness, and dehydration. A gastroenterologist should be consulted. Treatment with laxatives may be needed, and enemas might be helpful if faecal impaction is present.[10]
All patients with DMD or Becker muscular dystrophy have progressive cardiomyopathy. Its extent does not correlate with age.
A beta-blocker plus an ACE inhibitor or an angiotensin-II receptor antagonist increase left ventricular ejection fraction (LVEF) and are cardioprotective for these patients.[29] Implantable defibrillators and ventricular assist devices are increasingly used as cardiomyopathy worsens.
Risk factors include oesophageal dysmotility, delayed gastric emptying time, corticosteroid therapy, and scoliosis. A gastroenterologist should be consulted. Treatment options include proton-pump inhibitors and histamine-2 receptor antagonists. Eating smaller, more frequent meals and decreasing dietary fat intake may be beneficial.[10]
May occur as skeletal muscle weakness progresses. Symptoms and signs include postprandial abdominal pain, nausea, vomiting, early satiety, and loss of appetite. A gastroenterologist should be consulted. Treatment options include dietary modification, pharmacological therapy, or a gastro-jejunal feeding tube.[10]
Bladder dysfunction may be associated with DMD. Daytime incontinence, urinary frequency, urgency, nocturnal enuresis, nocturia, stress incontinence, and urinary hesitancy have been reported. Causes other than DMD should be excluded. Urodynamic studies may identify small capacity, hyper-reflexic bladder, and/or detrusor sphincter dyssynergia, and treatment should be tailored accordingly.[31]
Excessive daytime sleepiness (EDS) and morning headaches are caused by hypoventilation and hypercapnia in patients with DMD.
In conditions such as myotonic muscular dystrophy, EDS can be caused by involvement of the hypothalamic axis. Treatment options include modafinil, psychostimulant treatment, cognitive behavioural therapy, and behavioural therapy.[12][113]
Adrenal insufficiency is a rare but life-threatening condition associated with abrupt discontinuation of corticosteroid therapy, for example due to illness. Patients taking corticosteroids and their carers should be educated about the signs, symptoms, and management of adrenal crisis, and be provided with intramuscular hydrocortisone for emergency administration at home.[10]
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