Motor neurone disease Flashcards
Describe the pathophysiology of MND.
Degeneration of motor neurones in: The motor cortex Cranial nerve nuclei Anterior horn cell There is NO sensory loss.
Describe the pathophysiology of upper motor neurone disorders
Degeneration of motor cortex neurones.
Describe the pathophysiology of mixed MNDs
Degeneration of cranial nerve nuclei neurons
Describe the pathophysiology of lower MNDs
Anterior horn cell neuronal degeneration
Which is the most common type of MND?
Amyotrophic lateral sclerosis
Which type of MND affects UMNs?
Primary lateral sclerosis,
Which type of MND affects LMNs?
Progressive muscular atrophy
What is progressive bulbar palsy?
A rare type of MND.
Which type of MND affects upper motor neurones of the corticobulbar tract?
Pseudobulbar palsy
[PTS]
What investigations would you do if you suspect MND?
- Clinical exam - UMN and LMN signs.
- Electromyography (EMG) - shows neurophysiology
- Nerve conduction studies (NCS) - shows denervation
- MRI to exclude other causes
- LP to exclude inflammatory causes eg infection/autoimmune (MS)
What is the normal physiology of deciding on, and doing a movement?
- Idea of movement in association areas
- Activation of UMNs in precentral gyrus
- Impulses travel to LMNs via corticospinal tracts
- Modulation activity by the cerebellum and basal ganglia
- Modification of movement based on sensory feedback.
What makes up a motor unit?
LMN + its axon + supplied muscle fibres - FEWER fibres PER LMN the more SOPHISTOCATED the movement is.
Describe the management of MND.
- Riluzole: antiglutaminergic
- MDT
- Symptomatic tx:
- amitriptyline for drooling
- nil by mouth due to dysphagia (PEG)
- GABA agonist eg baclofen/ ca inhibitor eg dantrolene for spasticity
- analgesic ladder for joint pain
- NIV for respiratory failure.
How is muscle tone regulated?
- Stretch receptors in muscle (muscle spindles)*?
What are 3 clinical features of lower MNDs?
Everything goes down/ LOWERs:
- Decreased muscle tone
- Muscle wasting
- Reflexes weaken
- Fasciculation (contraction of motor units)
What is the final common pathway?
The motor neurons by which nerve impulses from many central sources pass to a muscle or gland in the periphery. (medical-dictionary.thefreedictionary.com)
What can damage the FCP?
Brainstem/SC: MND
Spinal roots: Prolapsed intervertebral disc, spinal tumours, malignant infltration
Peripheral nerves: axon demyelination/ degeneration
NMJ: Myasthaenia gravis, congenital
Muscle: weakness mostly affects proximal muscles.
How would you differentiate MND from MS?
MS causes sensory loss, disturbances in eye movements and sphincter disturbances, none of which occur in MND.
How would you differentiate myelopathy from MND?
If there is sensory loss, it is not MND.
What is the pharmacology of riluzole?
Riluzole is an antiglutaminergic which inhibits glutamate release and inhibits NMDA receptors.
What are the common side-effects of riluzole?
Nausea, weakness, decreased lung function.
Give 3 risk factors for MND.
Male 3:2
Family history, esp in inherited form of MND.
Increasing age
How does baclofen work?
Skeletal muscle relaxant, used to treat spasticity. Activates GABA receptor, blocking release of excitatory neurotransmitters.
How does dantrolene work?
Inhibits calcium ion release to reduce skeletal muscle contraction.
What is non-invasive ventilation?
Airway support administered through a nasal mask instead of an endotracheal tube.
