Lecture 35 - Muscular Dystrophies - Clinical Challenges Flashcards
Describe the make up of the multidisciplinary team that looks after DMD
What are the goals of this team?
• Genetic counsellor • Physicians • Physiotherapists • Palliative care • Speech pathologist • Occupational therapist etc.
Goals:
• Genetic counsellor
• Maintenance of ambulation
• Prevention and treatment of contractures
• Anticipatory monitoring for DMD complications
• Medical therapy
• Palliative care
Describe Genetic counselling and its role in DMD
• Commencement
• Aim
• Commences at the time of diagnoses
Aim: disease prevention
• Allow carriers to have normal boys
• Reassurance of those who aren’t carriers
1/3rd of mutations causing DMD are…
De novo
Antenatal diagnosis is most accurate with …
Deletions
Describe the importance of maintenance of ambulation
What happens when there is loss?
Importance:
• As long as the child with DMD is ambulant, he can live a reasonably independent existence and cope with most daily activities
• Less tendency to develop contractures and scoliosis when ambulant
Loss of ambulation: • Loss of independence • Prone to increasing complications: - Contractures - Scoliosis
How is ambulation maintained?
• Weight control - Diet - Exercise • Prevention of contractures • Physiotherapy • Corticosteroid therapy
Describe the observation of joint contractures in DMD
Which joints are affected?
Why do they arise?
• Achilles tendon contractures & muscle weakness → toe walking
Progressive contractures: • Hips • Knees • Elbows • Wrists
Arise because of:
• Static positioning in position of flexion
• Muscle imbalance around joint
• Fibrotic changes in muscle tissue
How can contractures be prevented?
Describe in detail surgical release
- Maintenance of ambulation
- Passive stretching (someone stretches for you)
- Active stretching (performed oneself)
- Physiotherapy
- Night time splints and braces
Surgical release of contractures • Variable, depending on the individual - Tendon Achilles releases - Anterior hip releases • Can prolong ambulation for 1-3 years • Bracing required post-operatively • Important to mobilise boys immediately post-operatively
Describe the importance of exercise in DMD
Which exercise is most beneficial?
What are the benefits?
Can exercise be harmful?
Sub-maximal aerobic exercise has a number of benefits on:
- Cardiovascular health
- Maintenance of muscle strength and raise of motion
- Avoidance of disuse atrophy
- Weight control
- Quality of life
e.g. Swimming:
• Aerobic
• Uses respiratory muscles
• Can be continued by the non-ambulant
Important to avoid:
• Over-exertion
• Eccentric / high-resistance strength training
Describe anticipatory monitoring in DMD
Monitoring of expected or common complications of DMD • Learning problems • Scoliosis • Respiratory muscle weakness • Cardiomyopathy
Describe management of learning disability in DMD
Early intervention strategies:
• Speech therapy
• Physiotherapy
• Occupational therapy
Assessment of skills and weaknesses
• Formal neuropsychological assessment in school age children
• Tailored school programme
• Provision of aide in classroom
Appropriate careers counselling
Describe the risk of scoliosis in DMD and how it can be attenuated
What about vertebral fractures?
Without steroids:
• 90% chance of developing scoliosis
• Small chance of vertebral compression fractures from osteoporosis
With steroids:
• Less risk of scoliosis
• Greater risk of vertebral fractures
Describe spinal monitoring in DMD
When is surgery performed?
Ambulatory phase: clinical observation sufficient
Non-ambulatory phase: annual X-rays
Guidelines of surgery: • Spinal curve > 25 degrees • Vital capacity > 30% of predicted • No active infection • No significant cardiomyopathy
What is Spinal Fusion?
What role does it play?
Spinal fusion is the surgical joining of vertebrae
aka Spondylodesis
Purpose: • Straightens the spine • Improves seated posture and comfort • Prevents further worsening • Eliminates pain due to vertebral fracture • Slows rate of respiratory decline • Prevents progression of scoliosis
Drawbacks / potential complications • Doesn't restore lost pulmonary function • Post-operative pain • Loss of muscle conditioning and strength with immobilisation • Loss of arm use • Decreased spinal motility • Complications of anaesthesia: - Malignant hyperthermia - Respiratory problems - Cardiac arrhythmias
Describe the effect of spinal fusion (Spondylodesis) on respiratory function
Can slow the rate of respiratory decline, but cannot restore lost function
Compare Spinal fusion with spinal bracing
Spinal fusion: the surgery
• Stops scoliosis progression
Spinal bracing:
• Rigid plastic brace worn on the outside
• Suitable for those unfit for surgery
• Does not stop scoliosis progression
Describe the various complications due to anaesthesia
What is specifically that it that brings about these complications?
Complications:
- Malignant hyperthermia
• Exposure to anaesthetic agents → predisposition to high fever and muscle breakdown - Acute hyperkalaemia
- Profound hyper-CK-aemia
- Acute cardiac decompensation
• Arrhythmias - Respiratory decompensation
Brought about by:
Triggering anaesthetics:
• Halothane
• Succinylcholine
Describe respiratory function in DMD
What is the progression seen during sleep?
Weak intercostal muscles → restrictive deficit
Early years:
• Vital capacity increases as normal
Early teens:
• Vital capacity plateaus
• Decline: 5-10% / year
Late teens / early 20’s
• Respiratory failure
Sleep disordered breathing → Nocturnal hypoventilation → Daytime hypoventilation
Describe how nocturnal hypoventilation can be treated
Nocturnal assisted ventilation
Benefits:
• Relieves symptoms
• Reduces hospitalisations
• ? Prolongs life
Describe how respiratory monitoring in DMD is carried out
What is the frequency?
Pulmonary function tests (Spirometry)
• Annual
Annual sleep study
• Desaturations
• Hypercapnia indicates decreased respiratory reserve
Peak cough flow test
• Annual
• Low PCF: risk of respiratory infections / failure
The frequency of the various tests is based on the age and progression of the DMD in the individual:
• Ambulatory and aged 6 or older: at least annually
- Non-ambulatory: At least every 6 months
- Non-ambulatory + suspected hypoventilation / FVC <50% predicted, use of assisted ventilation: At least annually
What is the best predictor of survival in DMD?
Pulmonary function tests
What is the implication of the following:
• Vital capacity <1L
< 1L: 100% mortality > 3 years if not ventilated*
Describe non invasive ventilation in children
NIV: Non-invasive ventilation
Mask strapped on, worn at night
Provides positive pressure to better inflate the lungs and alveoli
Mechanism:
1. Ventilatory provides air at positive pressure via mask
- Improved lung expansion
- Improved alveolar ventilation
- Reduced work of breathing and respiratory muscle fatigue
Describe cardiac involvement in DMD:
• Age of onset
• Presentation
• Treatment
Involvement may begin by 10, invariable by 18
Presentation: • Sinus tachycardia • Dilated cardiomyopathy (enlargement of heart) • Arrhythmias • Cardiomyopathy
Treatment:
Progression can be slowed by:
• ACE inhibitors
• Beta blockers
