Motor neurone disease Flashcards
What is motor neuron disease (MND)?
- Neurodegenerative condition caused by loss of UMNs and LMNs in the CNS
- Cause:
- Mostly sporadic
- SOD1 gene mutation 20% of familial cases
- Repeat sequence of C9orf72 gene on ch9 is associated with MND and frontotemporal dementia
What is the most common type of MND?
Amyotrophic lateral sclerosis (ALS)
Onset of MND?
- Average age of onset is 65
- 10% present before 45
- More common in males
Name some types of motor neuron disease?
- ALS
- Progressive muscular atrophy
- Primary lateral sclerosis
- Progressive bulbar palsy
Describe ALS?
- Mixed LMN and UMN
- Distal and proximal muscle wasting and weakness
- Fasciculation
- Spasticity, exaggerated reflexes, extensor plantars
- Pyramidal tract features may predominate
Describe Progressive muscular atrophy?
- Predominantly LMN
- Weakness and wasting of distal muscles initially
- Fasciculation
- Tendon reflexes may be present
Describe Primary lateral sclerosis?
- Predominantly UMN
- Spasticity - few lower motor neuron signs
- Gradual progression
Describe Progressive bulbar palsy?
- Predominantly cranial nerves
- Early involvement of tongue, palate and pharyngeal muscles
- Dysarthria/dysphagia
- Wasting and fasciulations of tongue
- Pyramidal signs may be present
Name a common terminal event of MND?
Type II respiratory failure
Describe cognitive impairment in MND?
- Up to 50% will have executive impairment
- 10% develop frontotemporal dementia (FTD)
Symptoms on MND?
- Limb weakness, cramps, fasciculation
- Disturbance of speech/swallowing
- Cogntivie and behavioural features common (similar to FTD)
What is dysarthria?
What is dysphagia?
Unclear execution of speech
Difficulty with swallowing
Signs of MND?
- Muscle wasting
- Weakness of limbs, tongue, face and palate
- Pyrimidal tract invovlement
- External ocular muscles and sphincters remain intact
What does pyrimidal tract involvement in MND cause?
- Spasticity
- Exaggerated tendon reflexes
- Extensor plantar responses
Describe investigations into MND?
- Clinical features are often typical but treatable causes should be excluded
- Blood:
- Mildly elevated creatine kinase
- Sensory and motor nerve conduction studies:
- Normal but ampoutude of motor action potentials may be reduced due to axonal loss
- EMG:
- Confirm widespread denervation and re-innervation
- Genetic testing:
- SOD1, C9orf72
Describe the management of MND?
- MDT
- Physio, OT, speech therapist, dieticians, palliative care
- Riluzole
- Non-invasive ventilation
- Feeding by percutaneous gastrostomy
Describe the use of Riluzole in MND?
- Licensed for ALS
- Glutamate release antagonist
- Prolongs median survivial by 2-3 months
Describe the use of non-invasive ventilation in MND?
Signficantly prolongs survival and improves QoL
Describe the mechanism of ALS?
- Mechanism of disease is unknown btu several theories exist:
- Glutamate toxicity
- Protein misfolding
- Mitochondrial dysfunction
Read this presentation of ALS
Name some differentials for ALS?
- Cervical spondylosis w/ myelopathy and radiculopathy
- Usually has bladder/bowel disturbances too
- MRI C-spine shows cord compression
- Myasthenia gravis
- Symptoms fluctuate
- Acetylecholine receptor antibodies present
