How is it treated and managed?
Duchenne Muscular Dystrophy
Physiotherapy and ankle splints
The diagnosis is likely to be made in early childhood at 4-5 years of age. At this stage the child will be mobile with an abnormal gait and unable to run and jump because of muscle weakness. They are more likely to fall over or be knocked over by other children because they do not have normal strength to maintain posture and balance. The aim of treatment in these early years is to prolong walking ability for as long as possible. Treatment will consist of physiotherapy exercises focussing on stretching exercises of the hips and ankles to promote normal gait -these children tend to walk on their toes. Achilles tendon contracture (shortening) is common. To prevent this, tendons are stretched using daily exercises and ankle splints may worn on the lower legs to stretch the Achilles tendon at night. Splints are not worn during the day at this stage.
Steroid drug treatment
Drug treatment between ages 5 and10 may aid muscle function and delay confinement to a wheelchair. The main drug used is corticosteroids (usually prednisolone), which may be given for a prolonged period. These improve muscle strength over a six month period but trials are still ongoing to determine the effect on walking ability. Side effects of treatment include weight gain, behavioural problems and changes in appearance. Obesity will make both mobilising in walking aids more difficult for the child and care more difficult once the child is confined to a wheelchair.
Rehabilitation of walking ability for exercise when independent walking ability is lost
Eventually the progressive muscle weakness results in the child being unable to walk at all. This is called ‘loss of ambulation’. Treatment at this stage may involve rehabilitation and possibly surgery to enable the child to walk a minimal distance with aids. This is likely to consist of the following:
- Fitting of long leg callipers/ knee-ankle-foot orthosis (KAFO)
- Child learning to walk in the callipers
- Surgery to lengthen the Achilles tendon may be required to enable fitting of callipers
- Training the parent to manage the callipers
Useful walking ability is rarely achieved but it does provide exercise for the child and improves prognosis. Walking in the KAF splints or callipers needs to be supervised because of the risk of falls. At first the child will be able to walk short distances in the walking aids but over time this distance will reduce as muscle weakness gets worse. If a ‘functional walking distance’ is mentioned in the medical evidence this means a distance of 10 metres. Many children will be using the aids mainly for standing and taking a few paces, they are unable to walk a useful distance. Wearing the aids and spending time standing may delay the onset of scoliosis.
After independent mobility is lost
Inevitably there will come a time when a child is unable to stand even with the support of orthoses/KAFO splints/callipers and at this time they will be confined to a wheelchair. This usually occurs at any age between 8 and 12. The aim of treatment at this stage is to preserve respiratory function to prolong survival. There are two aspects to loss of respiratory capacity in Duchenne Muscular Dystrophy. These are:
- The development of severe scoliosis (curvature of the spine), this restricts chest movement as well as making sitting in the wheelchair more difficult.
- The effect of gradually weakening respiratory muscles.
Respiratory function is monitored by measuring Forced Vital Capacity (FVC) this falls once independent mobility is lost. FVC falls gradually and boys become at serious risk of chest infection and ultimately respiratory failure. The underlying problem is that breathing is shallow because muscles are weak and this leads to low oxygen levels in the blood (hypoxia). Sleep studies will show if blood oxygen levels are becoming low at night. If this develops, night-time respiratory support will be provided. This delivers breaths via a snugly fitting face or nose mask. It is non-invasive and is not worn during the day. This type of support reduces the frequency of chest infections and improves survival. Later on in the condition, as muscle weakness progresses, the mask may be used during chest infections or routinely during the day.
Surgery for scoliosis
Surgery is performed before severe curvature develops. During the operation the vertebrae of the spine are fused together with metalwork – this is called spinal fusion. The whole length of the spine is fused and this restricts twisting, bending and reaching ability because the spine is made rigid. The procedure prevents further curvature from developing and preserves upright posture, which is important functionally for wheelchair users as well as preserving lung function. Recovery from surgery takes around 3 months. The surgery may make some activities with the upper limbs such as eating and personal care more difficult. In particular eating becomes more difficult as they cannot bend down to the plate and must reach further. If spinal surgery cannot be performed perhaps because of cardiomyopathy making anaesthesia and surgery too risky, the prognosis for survival is poor. Surgery is always more effective than conservative management of the spinal curvature with braces or supports. The priorities for physiotherapy are postural support and containment of contractures. Some boys may wear a spinal jacket and this is as limiting as spinal surgery in terms of movement. The carer must put on and remove the jacket for them each day. It is not worn in bed.
Cardiomyopathy
The heart is composed of muscle, when the muscle fibres become weak heart failure develops. This can be controlled with drugs for a time. The onset of heart failure in this condition is usually the early to mid teens. Drug treatment can prevent the onset of symptoms of heart failure and prolong survival. Drugs used include:
- Angiotensin Converting Enzyme (ACE) Inhibitor
- Beta-blockers
- Diuretic tablets to treat heart failure e.g. frusemide
Nutritional Problems
If steroid drug therapy is used to preserve mobility obesity may result. Obesity will make mobility more difficult for the child and is likely to persist into the period when mobility is lost. If the child is very heavy helping with care, especially transferring from bed to wheelchair and to the bath or shower for washing may be very difficult and a hoist may be required.
Once the child is in the wheelchair the reverse problem is encountered and weight loss is common, nutritional supplements may be necessary. Eating becomes more effortful over time and they develop swallowing problems, which can lead to choking episodes. Choking risks and difficulties with swallowing may mean that they physically cannot consume enough calories to support themselves and extra nutritional support is required. This commonly includes gastrostomy feeding.
Becker Muscular Dystrophy
Often no treatment is required during childhood for Becker Muscular dystrophy. Physiotherapy, splints and rarely oral steroid treatment may be used. If cramps of the legs after exercise are a particular problem, which they may be in boys in the teenage years, then intermittent compression therapy boots can be worn for half an hour at a time to relieve them (trade name for these boots is ‘Flotron’). Often cramps are related to exercise or walking and over time teenagers will learn what their walking threshold is and can avoid episodes of painful cramping by staying under it.
