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BIOM30002 - M2M > Lecture 35 - Muscular Dystrophies - Clinical Challenges > Flashcards

Lecture 35 - Muscular Dystrophies - Clinical Challenges Flashcards

1
Q

Describe the make up of the multidisciplinary team that looks after DMD

What are the goals of this team?

A 
• 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

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2
Q

Describe Genetic counselling and its role in DMD
• Commencement
• Aim

A

• Commences at the time of diagnoses

Aim: disease prevention
• Allow carriers to have normal boys
• Reassurance of those who aren’t carriers

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3
Q

1/3rd of mutations causing DMD are…

A

De novo

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4
Q

Antenatal diagnosis is most accurate with …

A

Deletions

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5
Q

Describe the importance of maintenance of ambulation

What happens when there is loss?

A

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
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6
Q

How is ambulation maintained?

A 
• Weight control
- Diet
- Exercise
 • Prevention of contractures
 • Physiotherapy
 • Corticosteroid therapy
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7
Q

Describe the observation of joint contractures in DMD

Which joints are affected?

Why do they arise?

A

• 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

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8
Q

How can contractures be prevented?

Describe in detail surgical release

A
  • 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
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9
Q

Describe the importance of exercise in DMD

Which exercise is most beneficial?

What are the benefits?

Can exercise be harmful?

A

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

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10
Q

Describe anticipatory monitoring in DMD

A 
Monitoring of expected or common complications of DMD
 • Learning problems
 • Scoliosis
 • Respiratory muscle weakness
 • Cardiomyopathy
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11
Q

Describe management of learning disability in DMD

A

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

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12
Q

Describe the risk of scoliosis in DMD and how it can be attenuated

What about vertebral fractures?

A

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

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13
Q

Describe spinal monitoring in DMD

When is surgery performed?

A

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
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14
Q

What is Spinal Fusion?

What role does it play?

A

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
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15
Q

Describe the effect of spinal fusion (Spondylodesis) on respiratory function

A

Can slow the rate of respiratory decline, but cannot restore lost function

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16
Q

Compare Spinal fusion with spinal bracing

A

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

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17
Q

Describe the various complications due to anaesthesia

What is specifically that it that brings about these complications?

A

Complications:

  1. Malignant hyperthermia
    • Exposure to anaesthetic agents → predisposition to high fever and muscle breakdown
  2. Acute hyperkalaemia
  3. Profound hyper-CK-aemia
  4. Acute cardiac decompensation
    • Arrhythmias
  5. Respiratory decompensation

Brought about by:
Triggering anaesthetics:
• Halothane
• Succinylcholine

18
Q

Describe respiratory function in DMD

What is the progression seen during sleep?

A

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

19
Q

Describe how nocturnal hypoventilation can be treated

A

Nocturnal assisted ventilation

Benefits:
• Relieves symptoms
• Reduces hospitalisations
• ? Prolongs life

20
Q

Describe how respiratory monitoring in DMD is carried out

What is the frequency?

A

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
21
Q

What is the best predictor of survival in DMD?

A

Pulmonary function tests

22
Q

What is the implication of the following:

• Vital capacity <1L

A

< 1L: 100% mortality > 3 years if not ventilated*

23
Q

Describe non invasive ventilation in children

A

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

  1. Improved lung expansion
  2. Improved alveolar ventilation
  3. Reduced work of breathing and respiratory muscle fatigue
24
Q

Describe cardiac involvement in DMD:
• Age of onset
• Presentation
• Treatment

A

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

25
Q

Describe how cardiac involvement in DMD is monitored, and how it is managed

A

Monitoring:
• Baseline assessment by 6 years

  • Regular ECG and echocardiography
  • Hypertension monitoring in boys on steroids

Management:
• Treatment of signs and symptoms
• Cardiac transplantation (if dilated cardiomyopathy is severe)

26
Q

Describe medical therapy of DMD

A

Drug therapy:
• Corticosteroids
(the only medical treatment shown to be effective in DMD)

Nutrition and dietary supplements

Endocrine treatment
• For delayed puberty

27
Q 
Describe the use of corticosteroids in DMD
 • Mechanism of action
 • Effects
 • When it is offered
 • Drawbacks
A

Mechanism of action:
• Unknown
Theories:
Positive effect on myogenesis
• Anabolic effect on muscle → increased muscle mass
• Stabilisation of muscle fibre membranes (sarcolemmas)
• Attenuation of muscle necrosis
• Immunosuppression (because there is inflammation in muscle during the early stages)

Effects:
• Rapid increase in strength
• Measurable effect in 10 days
• Slowed progression of muscle weakness
• Prolonged independent ambulation by 2-3 years
• Preservation of respiratory muscle function
• Delayed onset of cardiomyopathy and scoliosis
• Prolonged survival

When is it offered:
• At time of decline and frequent falls (4-6yr)
• Would be earlier, but there are some nasty side effects
• Continued at least until ambulation is lost

Drawbacks:
Side effects
 • Cushingoid features
 • Growth failure
 • Weight gain
 • Bone complications
- Avascular necrosis
- Osteoporosis
 • Myopathy
 • Diabetes
 • Skin: acne, striae
 • Hypertension
 • Psychosis, mood disturbance
 • Eye: cataracts, glaucoma
 • Infections
 • Adrenal suppression
28
Q

Describe the role of nutrition and diet in DMD over the years

A

Young boys:
• Energy requirements with DMD unknown
• (Being investigated)

Middle stage:
 • Obesity is common
 • Decreased energy expenditure
 • Reduced voluntary activity
 • Steroid side-effects

Older boys:
• Inconclusive data as to energy requirements

Late stage:
Swallowing difficulties
 → 
 • Poor oral intake
 • Weight loss
 • Constipation, Gastro-oesophageal reflux common
29
Q

Describe the role of micronutrients in DMD

Which micronutrients are supplemented?

A

Osteoporosis:
due to
Steroidal suppression of bone formation and increased bone resorption

→ Increased fracture risk

Treatment:
• Dietary calcium and vitamin D supplementation

30
Q

Describe bone health status in DMD:
• Contributing factors
• Complications

A

Contributing factors:
• Decreased mobility
• Muscle weakness
• Steroid use

Complications of poor bone health:
 • Fractures
 • Osteoporosis
 • Osteopaenia
 • Scoliosis
 • Bone pain
31
Q

Describe how bone health in DMD is assessed

A 
1. Blood tests
 • Ca
 • Phosphate
 • Alkaline phosphatase
 • Vitamin D
  1. Bone density scans
  2. Spine X-rays
32
Q

Describe fractures in DMD
• Prevalence
• When
• Significance

A

Prevalence:
• Long bone fractures: 20-45% of boys
• Vertebral fractures: 30% of boys

When:
• Peak in late childhood
• Due to falling out of the wheelchair

Significance:
• Causes significant pain and disability
• Boys may lose the ability to walk
• Can predispose to scoliosis

33
Q

List ‘adult’ and psychiatric issues associated with DMD

A

Life expectancy continues to extend, so there are more and different issues being encountered:

  • Delayed puberty
  • Adult neurologists (i.e. neurologists who look after adults) have limited experience with DMD

Psychiatric issues:
• Social isolation
• Depression

Social issues:
 • Idependence
 • Sexuality
 • Employment
 • Cognitive issues may complicate transition to adult services
 • Employment: in IT is common
34
Q

Describe palliative and psychiatric care in DMD

A

In end-stage DMD, death should be prepared for earlier rather than later

Common problems:
• Depression
• Anxiety
• Social withdrawal

These things can be anticipated and treated

Aims of palliative care:
• Maximising quality of life for as long as possible
• Minimising stress and fear for families
• giving young men choices and control over their death

35
Q

What complications do steroids help to prevent?

A

Scoliosis

However, on steroids there is a greater risk of vertebral fractures

36
Q

What is the Cobb angle?

A

Curvature of the spine

37
Q

Is respiratory decline in DMD restrictive or obstructive?

What does this mean for the pulmonary function tests?

A

Restrictive: due to the weakness of intercostals

VC: decreased
FEV: not affected

38
Q

By what age will boys with DMD invariably have cardiomyopathy?

A

18

39
Q

What do the following tests provide information about:
• ECG
• Echocardiogram

A

ECG: electrical function: rhythm of heart beat

Echocardiogram: structure and function of the pumping of the heart

40
Q

What about cardiac function in carriers?

A

They do have some cardiomyopathy

They also have ECG and echo every 5 years after the age of 16

41
Q

Which drugs have shown to be effective in DMD?

A

Only steroids have shown to be effective

42
Q

What are Cushingoid features?

A

Features associated with prolonged use of cortisol / steroids

Central obesity:
• Face
• Trunk

BIOM30002 - M2M (36 decks)

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