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 • 2
Case-based discussion: 1 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 on the right. You note hyperreflexia and visualise fasciculations. 5
A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped over Case History 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. Q6 Q1 Q2 Q3 Q4 Q5 Which part of the motor system is affected in amyotrophic lateral sclerosis? Parietal cortex Dorsal horn Corticospinal tract Muscle Neuromuscular junction app.bitemedicine.com 6
Explanations Q6 Q1 Q2 Q3 Q4 Q5 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 app.bitemedicine.com 7
Case-based discussion: 1 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 on the right. You note hyperreflexia and visualise fasciculations. 8
Classification of Motor Diseases Classification Pathology Examples Muscular disorders Inherited dystrophies Duchenne’s muscular dystrophy • Becker’s dystrophy • Inflammatory myopathies Polymyositis • NMJ disorders Interference of synaptic Myasthaenia gravis • transmission 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 • 9
L R 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) • (1) 10
L R 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 • (1) 11
L R 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 • (1) 12
A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped Case History 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. Q6 Q3 Q5 Q4 Q1 Q2 Which of the following most suggests a UMN lesion? Weakness Extensors weaker than flexors in upper limb Hyporeflexia Lower limb weakness > upper limb Upper limb weakness > lower limb 13 app.bitemedicine.com
Explanations Q3 Q4 Q5 Q6 Q1 Q2 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 app.bitemedicine.com 14
UMN vs LMN lesions UMN lesion means the LMN is no longer regulated • Upper motor neuron lesion Lower motor neuron lesion Site Proximal to anterior horn synapse Anterior horn and distal Tone Spasticity and/or rigidity Flaccid Pronator drift Power Reduced Reduced Upper limb: extensors weaker than • flexors Lower limb: flexors weaker than • extensors Reflexes Hyperreflexia Hyporeflexia Fasciculations Absent Present 15
Introduction 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 • 16
A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has tripped Case History 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. Q3 Q4 Q5 Q6 Q1 Q2 Which of the following is implicated in the pathophysiology of motor neuron disease? SOD1 Glutamate absence NAPQI excess Amyloid plaques PMP-22 mutation 17 app.bitemedicine.com
Explanations Q3 Q4 Q5 Q6 Q1 Q2 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) app.bitemedicine.com 18
Pathophysiology Degeneration of UMN and LMNs (1) 19
A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has Case History 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. Q5 Q4 Q1 Q2 Q3 Q6 Which of the following types of motor neuron disease has the worst prognosis? Amyotrophic lateral sclerosis Progressive muscular atrophy Primary lateral sclerosis Progressive bulbar palsy None of the above 20 app.bitemedicine.com
Explanations Q5 Q4 Q1 Q3 Q6 Q2 Which of the following types of motor neuron disease has the worst prognosis? 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 21 app.bitemedicine.com
A 69-year-old male presents with increasing clumsiness when he walks. Recently, he has Case History 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. Q1 Q3 Q5 Q6 Q2 Q4 Which of the following would we NOT expect to see? Tongue fasciculations Muscle atrophy Ophthalmoplegia Hyperreflexia Spasticity 22 app.bitemedicine.com
Explanations Q1 Q3 Q5 Q6 Q2 Q4 Which of the following would we NOT expect to see? 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 23 app.bitemedicine.com
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 24
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 25
Clinical features Absent features Sensory Extraocular muscles Cerebellar signs Extra-pyramidal 26
Clinical features Upper motor neuron lesion Lower motor neuron lesion Site Proximal to anterior horn synapse Distal to synapse Tone Spasticity and/or rigidity Flaccid Pronator drift Power Reduced Reduced Upper limb: extensors weaker than • flexors Lower limb: flexors weaker than • extensors Reflexes Hyperreflexia Hyporeflexia Fasciculations Absent Present 27
Clinical features (2) 28
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