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Pediatrics > Neuromuscular Disorders > Flashcards

Neuromuscular Disorders Flashcards

1
Q

Describe the pathology of Myasthenia Gravis

A

Autoimmune antibodies to Acetylcholine receptors (AChR antibodies) at the NMJ
Other antibodies: anti-muscle specific tyrosine kinase (anti MuSK)

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2
Q

What are the types of Myasthenia Gravis?

A

Neonatal myasthenia – transient, due to transplacental transfer of AChR antibodies. (Floppy but resolves by 3 months) from a myasthenic mother to foetus
Congenital myasthenic syndromes – genetic disorders of NMJ
Ocular myasthenia: affects eye muscles  ptosis, ophthalmoplegia.
Limb muscle may be mildly involved.
Generalized myasthenia: affects eye muscles, bulbar and limb muscle

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3
Q

Which groups of people are affected by Myasthenia Gravis?

A

Girls>Boys

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4
Q

Symptoms of Ocular Myasthenia Gravis

A

Ptosis
Ophthalmoplegia
Diplopia
NB. May be bilateral or unilateral
When bilateral, usually one eye more affected
Mild facial weakness

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5
Q

Symptoms of Ocular Myasthenia Gravis

A

Ptosis
Ophthalmoplegia
Diplopia
NB. May be bilateral or unilateral
When bilateral, usually one eye more affected
Mild facial weakness

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6
Q

Symptoms of Generalized Myasthenia Gravis

A

Bulbar weakness - weakness of swallowing muscle
Limb weakness
Fatiguability - as patient uses muscle, it gets weak
Diurnal variation - patient is stronger in the morning, weaker as the day progresses.

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7
Q

Other associated autoimmune disorders (with MSG)

A

Thyroiditis
Collagen Vascular Disease
Type 1 diabetes
Thymoma (produces autoimmune antibodies)

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8
Q

Investigations for Myasthenia Gravis

A

Ice pack test: Put ice pack on affected eyelid for 3-5 minutes. The muscle rests and the appearance of bright eyes is a positive test.
Edrophonium chloride test (Tensilon test) - Acetylcholinesterase inhibitor - Within 1 minute patients eyes become bright
Neostigmine test - Acetylycholinesterase inhibitor - but works in 15 minutes.
Repetitive nerve stimulation - Strength of contraction decreases each time - Decremental response on Graph
Serum antibody assay
AChR antibodies – NB. Patients with OMG may be seronegative or have low antibody concentrations
Anti-MuSK antibodies
Trial of pyridostigmine - Given for 2 weeks because of slow action. Same response as other Acetylcholinesterase inhibitors

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9
Q

Management of Myasthenia Gravis

A

Anticholinesterase therapy (pyridostigmine is preferred, but also neostigmine in acute phase)
Immunotherapy: corticosteroids, Intravenous Immunoglobulin, plasmapheresis
?Thymectomy if you suspect Thymoma as source of antibodies
Immunosuppressants: methotrexate

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10
Q

How is DMD inherited? Who does it affect? What causes DMD?

A

X-linked muscular disorder
Mutation causes reduced dystrophin (DMD < 3%, BMD < 20% dystrophin production, so milder)
Dystrophin links muscle fibers - It’s absence leads to muscle weakness
Affects only males
Some female carriers may have cardiomyopathy

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11
Q

Clinical features of DMD

A

Boys
Delayed motor milestones
Gait disturbance - Waddling gait
Toe walking
Frequent falls
Proximal weakness
Difficulty rising from the floor/sitting position
Waddling gait
Gower’s sign

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12
Q

Other Clinical Features of DMD

A

Calf hypertrophy
Increased lordosis
Most children maintain the ability to walk or climb stairs until 8 years of age
Require wheelchair by 10-12 years
Contractures develop easily: TA - Archilles Tendon, knee, elbows
Scoliosis
Deterioration of vital capacity - nocturnal hypoventilation (present with morning headaches or daytime somnolence
Death usually from cardiomyopathy and respiratory insufficiency

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13
Q

Investigations for DMD

A

Diagnosis
Serum CK: very high in the 1000 (usual upper limit is 170.190)
Molecular genetic testing - to confirm DMD
Muscle biopsy - to confirm DMD
Other investigations
ECG - ‘Cause of arrythmias
Echocardiogram - For Cardiac Function
Pulmonary function test
Bone densitometry - because of poor mineralization. Done every year or every 2 years.

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14
Q

Complications of DMD

A

Loss of ambulation
Cardiomyopathy
Respiratory muscle weakness due to worsening respiratory function
Scoliosis
Decreased bone mineralization
Learning difficulty
Psychosocial problems

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15
Q

Management of DMD

A

Steroid treatment: Prednisone 0.75mg/kg daily
does not cure disease
Prolongs ambulation
Improves respiratory and cardiac function
Physiotherapy
Cardiac care
Respiratory care
Bone health - Give Calcium and Vitamin D
Scoliosis care
Sleep quality
Genetic counselling
Genetic modification therapy

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16
Q

Define the following terminologies for Neuromuscular Disorders

A

Hypertonia
Spasticity - Velocity dependent. It gives in as you continue to extend and flex joint vs. Rigidity - Increased tone continues throughout the full range of motion. (Doesn’t give in
Hypotonia
Flaccidity/floppiness
Hemiparesis/hemiplegia - weakness on one side of the body
Paraparesis/paraplegia - weakness in lower limbs
Tetraparesis/tetraplegia - weakness in all 4 limbs

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17
Q

Define the following terminologies for Musculoskeletal Disorders

A

Macrocephaly - Increased Head Circumference > +2 SD
Microcephaly - Decreased Head Circumference > -2SD
Scoliosis - Curvature of Spine
Arthrogryposis - Multiple contractures in multiple joints (Arthrogryposis multiplex congenita)
Posture - Relation of limbs to trunk whilst patient is at rest/lying down
Gait - Relation of limbs to trunk whilst patient is standing
Stature - Height

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18
Q

Neuromuscular disorders by localization

A

Brain
Spinal cord
Anterior horn cells
Peripheral nerve
Neuromuscular junction
Muscle
Generalized - eg. hypothyroidism

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19
Q

Common Presentations of Neuromuscular Disorders

A

Floppy infant: hypotonic and weak
Ventilator dependent neonate failing extubation
Arthrogryposis
Delayed motor development
Poor gait
Frequent falls
Difficulty with steps
Toe walking
Muscle pain or cramps
Stiffness

20
Q

Other common presentations of neuromuscular disease

A

Foot deformity – high arched, flat foot, etc.
Episodic weakness
Exercise limitation
Recurrent apnoea
Chest wall deformities
Pain on or after exercise
Cardiomyopathies
Abnormal biochemistry: raised CK, raised ALT

21
Q

Who is a floppy infant?

A

An infant with generalized hypotonia presenting at birth or in early life

22
Q

Questions to ask in history of Floppy Infant

A

*pre-, peri- and postnatal history
*quality and quantity of fetal movements (For neuromuscular disorders with onset before birth. Compare with other child)
*breech presentation (Neuromuscular condition which prevented normal cephalic version)
*presence of either poly- (from impaired swallowing) or oligohydramnios.
*any clues to hypoxic-ischaemic encephalopathy
*Neonatal seizures or encephalopathic state
*The onset of the hypotonia – may distinguish between congenital and acquired etiologies.
*Enquire about consanguinity and identify other affected family members

23
Q

What are the two approaches to the diagnostic problem on neuro examination?

A

Identifying the neuro-anatomical site of the lesion or insult.
Upper motor neuron (UMN) vs. lower motor neuron (LMN) lesion
Determine whether the hypotonia is accompanied by weakness or not .
Weakness is uncommon in UMN hypotonia except in the acute stages.
Hypotonia with profound weakness therefore suggests involvement of the LMN.

24
Q

Useful indicators of weakness

A

Inability to cough and clear airway secretions
Swallowing ability as indicated by drooling and oropharyngeal pooling of secretions or cough during feeding.
The character of the cry — infants with consistent respiratory weakness have a weak cry.
Paradoxical breathing pattern — intercostal muscles paralysed with intact diaphragm.

25
Q

Patterns of breathing in neuromuscular disorders

A

Brain: axial, truncal or generalized hypotonia
Cord: paraplegia or tetraplegia
Anterior horn cells: proximal > distal, LL > UL
Peripheral nerve: distal weakness
NMJ: generalized weakness
Muscle: proximal weakness

26
Q

Specific Neuromuscular Conditions - BANP

A

Brain/spinal cord
Corticospinal tract disorder
Basal ganglia disorders
Cerebellar disorders
Anterior horn cell
Spinal muscular atrophy (SMA) - Congenital
Poliomyelitis - Acquired
Peripheral nerve
Charcot-Marie-Tooth disease (CMT) - Congenital
Guillian Barre syndrome (GBS) - Acquired
Neuromuscular junction
Myasthenia gravis - Congenital/Acquired
Botulinum toxicity - Acquired

27
Q

Specific Neuromuscular Conditions - Muscle and Generalized

A

*Muscle
Congenital myopathy
Dystrophinopathies (Duchenne/Becker Muscular Dystrophy)
Myotonia dystrophies
Inflammatory (Dermatomyositis)
Metabolic (Pompe disease, mitochondrial myopathies)
*Generalized
Trisomy 21
Hypothyroidism
Prader Willi syndrome

28
Q

What is Spinal Muscular Atrophy and how is it inherited?

A

Anterior horn cell disease
Autosomal recessive disorder

29
Q

What causes SMA?

A

Deletion in the survival motor neuron 1 (SMN1)
Mutation in SMN1 -> degeneration of anterior horn cells -> progressive weakness and wasting of skeletal muscle

30
Q

What makes SMA milder?

A

The number of copies of SMN2 gene, which produces defective protein.

31
Q

Classification of SMA

A

Classified based on severity
Type 1: Werdnig-Hoffman disease (severe type)
Type 2: intermediate type SMA
Type 3: Kugelberg-Welander disease (mild type)
Type 0: Very severe, in utero, results in still birth, or neonatal death
Type 4: Adult onset

32
Q

Describe the age at onset, development and Prognosis of the SMA types

A

Type >Age at onset >Development > Prognosis
1 < 6 months> Never sit unsupported >Most die within the first year of life. Usually due to RTI

2> 6-18 months> Sit but never walk unsupported >May grow into late childhood

3> > 18 months> Walk unsupported at some stage> Often grows into adulthood

33
Q

Clinical features of SMA

A

Alert, normal facial expression (Normal/Superior cognition, no facial weakness)
*Symmetrical flaccid paralysis
*Pattern of weakness: proximal > distal, legs > arms
*Absent deep tendon reflexes
*Tongue fasciculations
*Intercostal muscle weakness with sparing of the diaphragm - paradoxical/Seesaw breathing
*Weakness of the bulbar muscle > weak cry, poor suck and pooling of secretions
*Contractures
*Survival depends on respiratory and bulbar functions (aspiration risk)

34
Q

Diagnosis of SMA - History and Physical Exam

A

History: decreased fetal movement, floppiness at birth, delayed motor milestones, recurrent aspiration and RTI,
Physicals Exam: floppy infant, cognitively bright child, normal facial expression, proximal > distal weakness, tongue fasciculation, bell shaped chest - ‘cause of persistent use of diaphragm, paradoxical breathing, contractures

35
Q

Investigations for SMA

A

Serum Creatine Kinase: normal or mildly raised (To rule out muscle disease)
ECG: may show baseline fibrillations
DNA analysis: to test for deletion on SMN1
Muscle biopsy - muscle atrophy
Electromyogram

36
Q

Supportive management and Definitive treatment for SMA

A

*Supportive Management:
Respiratory care
Prompt treatment of respiratory infections
Chest physiotherapy
Physiotherapy
Nocturnal BiPAP (Prevents poor oxygenation of brain so no morning headaches)
*Definitive treatment
Genetic modification drugs(experimental)

37
Q

Is Guillian Barre Congenital or Acquired?

A

Acquired

38
Q

What are the common and less common causes (variants)?

A

Commonly due to acute inflammatory demyelinating polyneuropathy (AIDP) - Affects myelin
Less common variants include:
Acute axonal neuropathy - Affects axon
Chronic inflammatory demyelinating polyradiculoneuropathy CIDP)
Miller-fisher syndrome - AIDP + Cranial nerve involvement

39
Q

Presentation of AIDP. Phases of AIDP. Associations

A

Acute (reaches maximum within 48-72 hours, monophasic
Demyelinating
Peripheral nerves are the target of an abnormal immune response
Antecedent viral infection (about half of patients)
RTI > GI infections
Progressive phase  plateau phase recovery phase

40
Q

Clinical Features of GBS

A

*Progressive motor weakness with areflexia
*Ascending or descending (recovery in reverse)
*Relatively symmetrical
*Weakness progresses rapidly - same as recovery, reaching a nadir by 2-4 weeks
*Autonomic dysfunction (arrhythmia, labile BP, GI dysfunction)
*Facial weakness (MFS)
*Respiratory paralysis
*Bulbar dysfunction
*Recovery of function within 2-4 weeks

41
Q

Investigations for GBS

A

NB. Diagnosis of GBS is clinical: progressive weakness + areflexia
Investigations to support diagnosis and rule out differentials include:
CSF: Albuminocytologic dissociation after 1st week (↑protein, no/low cells) supports GBS
Stool: for polio and non-polio enteroviruses
Nerve conduction studies
To help differentiate demyelinating type from the axonal type
Demyelinating: slow nerve conduction velocity
Axonal: decreased amplitude
Others
Blood: for campylobacter, Coxsackie
Serology for mycoplasma, EBV, CMV, VZV, Borrelia
MRI of brain and spine - not recommended: the nerve roots lights up on contrast studies in GBS

42
Q

Differential Diagnosis of GBS

A

Poliomyelitis
Non-polio enterovirus infections
Transverse myelitis
Botulinum toxin
Tick paralysis
Porphyria
Diphtheria
Spinal cord compression
Viral myositis

43
Q

Case Definition of Acute Flaccid Paralysis

A

Any child less than 15 years who has AFP or a person at any age with paralytic illness in whom the clinician suspects Polio
Acute: the paralysis is of sudden onset (progresses and reaches maximum level within 72 hours of onset)
Flaccid: floppy, not rigid, not stiff
Paralysis: loss of muscle strength (weakness, limitation of movement)
(For a true AFP, all 3 conditions should be met)

44
Q

Management of Acute Flaccid Paralysis

A

Notify as a case of AFP: disease control officer/public health unit
Two (2) stool samples collected 24-48 apart, within 14 days of onset of paralysis in two different specimen containers
Place specimen in cold box below 8*C between frozen ice packs
Send to WHO-accredited lab within 3 days (If last 2 conditions aren’t satisfied sample will be rejected)

45
Q

Management of Guilian Barre Syndrome

A

Respiratory support: admit to ICU if
rapidly progressive
Vital capacity < 50%
IVIG - Mop up antibodies
Plasma exchange - Mop up antibodies
NB. Corticosteroids not helpful: may produce some initial improvement but tends to prolong the course
Physiotherapy
Recovery is usually in reverse order to the progression

Pediatrics (12 decks)

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