Motor Neurone Disease Flashcards
Define MND
Progressive neurodegenerative disorder of cortical, brainstem and spinal motor neurones
Amyotrophic lateral sclerosis (Lou Gehrig’s disease) – UMN & LMN degeneration
Progressive lateral sclerosis – UMN degeneration
Progressive muscular atrophy – LMN degeneration
Progressive bulbar palsy – LMN bulbar degeneration
Bulbar palsy – LMN lesion at nuclear, nerve or muscle level affecting cranial nerves
IX-XII presenting with nasal speech, nasal regurgitation of food (especially fluids), ↓
gag reflex, absent jaw jerk, wasted fasciculating tongue
Pseudobulbar palsy – UMN lesion at cortical or brainstem level affecting cranial
nerves IX-XII presenting with monotonous or explosive speech, dysphagia, ↑ gag
reflex, brisk jaw jerk reflex, shrunken immobile tongue, emotional lability, UMN limb
spasticity and weakness
What are the causes/risk factors of MND?
Unknown aetiology • Glutamate toxicity • Protein misfolding • Oxidative stress • Microglial activation • Mitochondrial dysfunction • Disrupted axonal transport
Risk Factors
• Family history
• SOD-1 gene mutations (20% of familial MND, 1-4% of sporadic MND)
• Associated with frontotemporal dementia
What are the symptoms of MND?
• Limb weakness • Dysarthria – tongue and pharyngeal muscle weakness - Slurred - Hypophonic (↓ volume) - Dysphonic (hoarse) • Dysphagia – choking on liquids -> foods - UMN: lack of co-ordination - LMN: tongue and pharyngeal muscle weakness • Nasal regurgitation • Dyspnoea • Disinhibition • Emotional lability – inappropriate bursts of crying or laughter
What are the signs of MND?
UMN signs • Spastic weakness - Stiffness - Poor co-ordination and balance • Brisk reflexes • Extensor (upgoing) plantars LMN signs • Muscle wasting • Fasciculations • Flaccid weakness - Difficulty brushing teeth/hair - Foot drop • Hyporeflexia/arreflexia • Dysphagia – lack of co-ordination - Choking on liquids -> foods
What investigations are carried out for MND?
• CK - mildly elevated due to denervated muscles in ALS.
• Anti-GM1 Ab - multifocal motor neuropathy: Characterised by asymmetrical LMN signs. Important to distinguish from MND as treatable. Motor nerve conduction studies show evidence of conduction block, representing focal demyelination. Associated with GM1 autoantibodies. Treatable with intravenous immunoglobulin, steroids or immunosuppression.
• EMG - evidence of diffuse, ongoing (fibrillation potentials and positive waves), and chronic (motor unit potentials with large amplitude and long duration) denervation.
• Nerve Conduction -
normal
• MRI - to exclude cord or root compression, and brainstem lesion in progressive bulbar palsy.
- May show high signal in motor tracts on T2 imaging.
• Spirometry - to assess lung function and respiratory muscle weakness (FVC).
