Aims and objectives Cover the following: Pathophysiology, - - PowerPoint PPT Presentation

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Aims and objectives Cover the following: Pathophysiology, - - PowerPoint PPT Presentation

Jan 10, 2023 144 likes •582 views

Aims and objectives Cover the following: Pathophysiology, clinical presentation, investigations, management Upper motor neuron vs lower motor neuron lesion Different types of MND High yield facts for SBAs and OSCEs

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Aims and objectives

  • Cover the following:
  • Pathophysiology, clinical presentation, investigations, management
  • Upper motor neuron vs lower motor neuron lesion
  • Different types of MND
  • High yield facts for SBAs and OSCEs
  • Duration: 60 mins
  • Slides and recordings: app.bitemedicine.com
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History and examination

A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped over twice and is unable to go jogging due to right leg weakness. On examination, he has bilateral leg weakness which is worse

  • n

the right. You note hyperreflexia and visualise fasciculations.

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Case-based discussion: 1

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A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped over twice and is unable to go jogging due to right leg weakness. On examination, he has bilateral leg weakness which is worse on the right. You note hyperreflexia and visualise fasciculations. Which part of the motor system is affected in amyotrophic lateral sclerosis?

Case History

Parietal cortex Dorsal horn Corticospinal tract Muscle Neuromuscular junction app.bitemedicine.com

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Explanations

app.bitemedicine.com Which part of the motor system is most affected in amyotrophic lateral sclerosis? Parietal cortex This is not part of the motor system Dorsal horn Not part of the motor system. Responsible for sensory neurones Corticospinal tract This would give UMN signs and is affected in MND Muscle Not affected in MND Neuromuscular junction Not affected in MND

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History and examination

A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped over twice and is unable to go jogging due to right leg weakness. On examination, he has bilateral leg weakness which is worse

  • n

the right. You note hyperreflexia and visualise fasciculations.

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Case-based discussion: 1

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Classification of Motor Diseases

Classification Pathology Examples Muscular disorders Inherited dystrophies Inflammatory myopathies

  • Duchenne’s muscular dystrophy
  • Becker’s dystrophy
  • Polymyositis

NMJ disorders Interference of synaptic transmission

  • Myasthaenia gravis
  • Lambert-Eaton syndrome

Lower motor neuron Pathology distal to anterior horn

  • Polio
  • Neuropathies
  • MND

Upper motor neuron Pathology proximal to anterior horn

  • Stroke
  • MS
  • MND

Extrapyramidal Basal ganglia pathology

  • Parkinsonism
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Motor pathways

I want to move my right thumb…

  • UMN activated in left primary motor cortex
  • Medulla:
  • 90% of fibres cross (lateral corticospinal tract)
  • 10% do not cross (anterior corticospinal tract)

L R

(1)

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Motor pathways

I want to move my right thumb…

  • UMN activated in left primary motor cortex
  • Medulla:
  • 90% of fibres cross (lateral corticospinal tract)
  • 10% do not cross (anterior corticospinal tract)
  • UMN continues until they reach the correct spinal level
  • UMN synapses with the LMN at the anterior horn of spinal

cord

  • The LMN innervates the responsible skeletal muscles

L R

(1)

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Upper & lower motor neurons

Upper motor neuron

  • Brain
  • Brainstem
  • Injury to white matter of spinal cord up to level of synapse

Lower motor neuron

  • Injury to the grey matter of spinal cord at level of synapse

(anterior horn)

  • Injury to axons leaving spinal cord

L R

(1)

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Which of the following most suggests a UMN lesion?

Case History

Weakness Extensors weaker than flexors in upper limb Hyporeflexia Lower limb weakness > upper limb Upper limb weakness > lower limb app.bitemedicine.com A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped

  • ver twice and is unable to go jogging due to right leg weakness.

On examination, he has bilateral leg weakness which is worse on the right. You note hyperreflexia and visualise fasciculations.

Q3 Q4 Q5 Q2 Q1 Q6

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Explanations

app.bitemedicine.com Which of the following most suggests a UMN lesion? Weakness This is seen in both UMN and LMN lesions Extensors weaker than flexors in upper limb This is classical of a UMN lesion and is referred to as a pyramidal pattern of weakness Hyporeflexia We would expect hyperreflexia Lower limb weakness > upper limb The worst affected limb depends on the location of the lesion and not whether it’s an UMN lesion Upper limb weakness > lower limb The worst affected limb depends on the location of the lesion and not whether it’s an UMN lesion

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UMN vs LMN lesions

Upper motor neuron lesion Lower motor neuron lesion Site Proximal to anterior horn synapse Anterior horn and distal Tone Spasticity and/or rigidity Pronator drift Flaccid Power Reduced

  • Upper limb: extensors weaker than

flexors

  • Lower limb: flexors weaker than

extensors Reduced Reflexes Hyperreflexia Hyporeflexia Fasciculations Absent Present

  • UMN lesion means the LMN is no longer regulated
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Definition

  • Neurodegenerative condition
  • Progressive degeneration of UMNs and LMNs

Epidemiology

  • Rare disease
  • Incidence of ~ 2 per 100,000

Risk factors

  • Age: median onset at 60 years old
  • Male sex: 1.2 to 1.8 times more likely to develop MND
  • Family history: familial in ~ 5% of cases
  • Smoking: currently a ‘probable’ risk factor for MND

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Introduction

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Which of the following is implicated in the pathophysiology of motor neuron disease?

Case History

SOD1 Glutamate absence NAPQI excess Amyloid plaques PMP-22 mutation app.bitemedicine.com A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped

  • ver twice and is unable to go jogging due to right leg weakness.

On examination, he has bilateral leg weakness which is worse on the right. You note hyperreflexia and visualise fasciculations.

Q2 Q3 Q1 Q4 Q5 Q6

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Explanations

app.bitemedicine.com Which of the following is implicated in the pathophysiology of motor neuron disease? SOD1 mutation SOD1 mutations are found in a small proportion of cases Glutamate absence Glutamate toxicity is thought to contribute to neurodegeneration NAPQI excess Mitochondrial poison that builds up in paracetamol overdose Amyloid plaques Associated with Alzheimer’s disease PMP-22 mutation Seen in HSMN (Charcot-Marie-Tooth disease)

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Pathophysiology

Degeneration of UMN and LMNs

(1)

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Which of the following types of motor neuron disease has the worst prognosis?

Case History

Amyotrophic lateral sclerosis Progressive muscular atrophy Primary lateral sclerosis Progressive bulbar palsy None of the above app.bitemedicine.com A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped over twice and is unable to go jogging due to right leg weakness. On examination, he has bilateral leg weakness which is worse on the right. You note hyperreflexia and visualise fasciculations.

Q2 Q4 Q3 Q1 Q5 Q6

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Explanations

app.bitemedicine.com Amyotrophic lateral sclerosis Most common type but does not carry the worst prognosis Progressive muscular atrophy Rare type. Best prognosis Primary lateral sclerosis Rare type Progressive bulbar palsy Rare type. Worst prognosis None of the above Incorrect Which of the following types of motor neuron disease has the worst prognosis?

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Which of the following would we NOT expect to see?

Case History

Tongue fasciculations Muscle atrophy Ophthalmoplegia Hyperreflexia Spasticity app.bitemedicine.com A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped over twice and is unable to go jogging due to right leg weakness. On examination, he has bilateral leg weakness which is worse on the right. You note hyperreflexia and visualise fasciculations.

Q2 Q1 Q3 Q4 Q5 Q6

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Explanations

app.bitemedicine.com Tongue fasciculations Typical finding Muscle atrophy Can be seen, particularly later on into disease course Ophthalmoplegia Extraocular muscles not usually involved Hyperreflexia UMN sign associated with MND Spasticity UMN sign associated with MND Which of the following would we NOT expect to see?

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Classification

Motor Characteristics Amyotrophic lateral sclerosis Predominantly affects UMNs Can also affect LMNs Starts unilaterally and progresses bilaterally Can cause bulbar palsy Most common form Progressive muscular atrophy LMN signs only Best prognosis Primary lateral sclerosis UMN signs only Progressive bulbar palsy Bulbar palsy (cranial nerves IX-XII)

  • Speech and swallow issues

Worst prognosis

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Clinical features

Symptoms Signs Progressive weakness of multiple limbs UMN and/or LMN signs depending on type of MND Falls Muscle atrophy Speech and swallow issues

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Clinical features

Absent features Sensory Extraocular muscles Cerebellar signs Extra-pyramidal

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Clinical features

Upper motor neuron lesion Lower motor neuron lesion Site Proximal to anterior horn synapse Distal to synapse Tone Spasticity and/or rigidity Pronator drift Flaccid Power Reduced

  • Upper limb: extensors weaker than

flexors

  • Lower limb: flexors weaker than

extensors Reduced Reflexes Hyperreflexia Hyporeflexia Fasciculations Absent Present

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Clinical features

(2)

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Investigations

MND is a clinical diagnosis Investigations to consider

  • EMG: evidence of muscle denervation
  • Nerve conduction studies: typically normal
  • MRI spine: rule out spinal disease e.g. cervical cord compression or demyelination
  • Pulmonary function tests: risk of respiratory failure
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Which of the following management options prolongs survival by the most?

Case History

Gastrostomy Riluzole Respiratory support Physiotherapy Speech and language therapy app.bitemedicine.com A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped over twice and is unable to go jogging due to right leg weakness. On examination, he has bilateral leg weakness which is worse on the right. You note hyperreflexia and visualise fasciculations.

Q2 Q1 Q3 Q4 Q5 Q6

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Explanations

app.bitemedicine.com Gastrostomy Supportive treatment Riluzole Prolongs survival ~ 2-4 months Respiratory support Prolongs survival ~ 7 months Physiotherapy Supportive treatment Speech and language therapy Supportive treatment Which of the following management options prolongs survival by the most?

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Management

Multi-disciplinary team management Treatments prolonging survival

  • Riluzole: used in ALS and prolongs survival by 2-4 months
  • Protects against glutamate-mediated neuronal toxicity
  • Respiratory support: those with reduced FVC can have BiPAP at home
  • Prolongs survival by 7 months

Supportive therapy

  • Muscle cramps: quinine or baclofen
  • Feeding support: gastrostomy
  • Speech and language therapy
  • Physiotherapy
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Complications

Complications Aspiration pneumonia Respiratory failure Swallow failure

Prognosis after diagnosis

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Differential diagnoses

Disease Comments Motor neuron disease

  • Degeneration of UMNs/LMNs
  • Motor symptoms and signs only
  • Clinical diagnosis
  • EMG shows fibrillation potentials

Cervical spondylosis

  • Compression of the cervical spinal cord due to age-related spinal changes
  • Sensory AND motor symptoms
  • LMN signs at the level of compression and UMN signs below
  • Confirmed on MRI

Myasthaenia gravis

  • Ach-R antibodies
  • Fatigable weakness
  • Ophthalmoplegia and ptosis
  • Serology and EMG used for diagnosis
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Which of the following is characteristic of a LMN lesion?

Revision

Hypotonia Spasticity Weakness Rigidity Hyperreflexia app.bitemedicine.com

Q1 Q2

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Explanations

app.bitemedicine.com Hypotonia LMN sign Spasticity UMN sign Weakness Seen in both UMN and LMN lesions Rigidity UMN sign Hyperreflexia UMN sign Which of the following is characteristic of a LMN lesion?

Q1 Q2

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Which of the following types of MND has the best prognosis?

Revision

Amyotrophic lateral sclerosis Primary muscular atrophy Progressive bulbar palsy Progressive lateral sclerosis None of the above app.bitemedicine.com

Q2 Q1

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Explanations

app.bitemedicine.com Amyotrophic lateral sclerosis Most common Primary muscular atrophy Best prognosis Progressive bulbar palsy Worst prognosis Progressive lateral sclerosis Rare subtype None of the above UMN sign Which of the following types of MND has the best prognosis?

Q2 Q1

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Top-decile question

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Explanations

app.bitemedicine.com Which of the following may be seen on EMG in motor neurone disease? Slow motor conduction Suggests alternate pathology Conduction block Suggests alternate pathology Fibrillation potentials Suggest denervation of muscles Small amplitude Usually large amplitude Hypsarrhythmia An EEG finding seen in infantile spasms

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Recap

  • Motor neurone disease consists of 4 types
  • ALS
  • PLS
  • PMA
  • PBS
  • MND involves degeneration of UMNs and LMNs
  • It is a clinical diagnosis but often other tests such as an EMG and spinal MRI are carried out
  • Riluzole and respiratory support can prolong survival
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References

1) OpenStax College / CC BY (https://creativecommons.org/licenses/by/3.0) 2) Okumiya K, Wada T, Fujisawa M, Ishine M, Garcia Del Saz E, Hirata Y, Kuzuhara S, Kokubo Y, Seguchi H, Sakamoto R, Manuaba I, Watofa P, Rantetampang AL, Matsubayashi K - BMJ Open (2014) / CC BY (https://creativecommons.org/licenses/by/3.0) All other images were made by BiteMedicine or under the basic Shutterstock licence and not suitable for redistribution.

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