Motor Neurone Disease Flashcards
What is MND?
Progressive neurodegenerative disorder of motor neurons (LMN + UMNs)
Name 4 subtypes of MND
Amyotrophic Lateral Sclerosis (ALS)
Progressive Muscular Atrophy
Progressive Bulbar Palsy
Primary Lateral Sclerosis
Describe Amyotrophic Lateral Sclerosis
Most common type of MND
Combined degeneration of UMN + LMNs resulting a mix of signs
Typically LMN signs in arms + UMN signs in legs
In familial cases of ALS, which gene is responsible?
Lies on Chr21 + codes for superoxide dismutase
Describe Progressive Muscular Atrophy
Only LMN signs e.g. flail arm/ foot.
Affects distal muscles before proximal
Better prognosis
~10% of MND
Describe Progressive Bulbar Palsy
Loss of function of brainstem nuclei
Worst prognosis
~20% of MND
Describe Primary Lateral Sclerosis
UMN pattern of weakness
Brisk reflexes
Extensor plantar responses.
NO LMN signs
~1% of MND
Slow progression, normal-ish life expectancy
What causes MND?
UNKNOWN
Free radical damage + glutamate excitotoxicity have been implicated as mutations in SOD1 gene
What condition is MND associated with?
Frontotemporal lobar dementia
What is the epidemiology of MND?
4 in 100,000
M > F 2:1
Mean age of onset: 65y
5-10% have FH with AD inheritance
How does MND usually present?
Asymmetric limb weakness
+/- functional effect; loss of dexterity/ falls/ trips
List 4 signs of MND
UMN + LMN signs, often affecting several regions asymmetrically
Wasting of small hand muscles/ tibialis anterior
Fasciculations
Absence of sensory S/S
List 5 late symptoms of MND
Cognitive impairment ~frontotemporal dementia Autonomic Sx Respiratory failure Dysphagia Sphincter dysfunction
4 features of progressive bulbar palsy
Dysarthria
Dysphagia.
Wasted, fasciculating tongue (LMN).
Brisk jaw jerk reflex (UMN)
What LMN signs are seen in MND?
Muscle wasting
Fasciculations (esp. thighs)
Flaccid weakness
Hyporeflexia
What UMN signs are seen in MND?
Spastic weakness
Extensor plantar response
Hyperreflexia
Which muscles are not affected/ signs not seen in MND?
Doesn’t affect external ocular muscles
No cerebellar signs
Abdominal reflexes usually preserved
What investigations are necessary for diagnosing MND?
Clinical dx
Can do Ix to r/o other differentials
What is seen on nerve conduction studies in MND?
Normal motor conduction
(excludes neuropathy)
What is seen on electromyography in MND?
Reduced number of action potentials with increased amplitude
What is excluded by MRI in suspected MND?
Cervical cord compression
Brainstem lesions
Myelopathy
What blood tests are requested when suspecting MND to rule out other differentials?
Vitamin B12 + folate levels
HIV serology
Lyme disease serology
Creatine kinase assay
Serum protein electrophoresis
Anti-GM1 antibodies (multifocal motor neuropathy with conduction block)
Urinary hexosaminidase-A assay (Tay-Sachs)
What conservative management strategies can be used in MND?
Exercise programme: maintains ROM, prevents contractures + stiffness
Resp physio
Dietetic support
What pharmacological management is used in MND?
Riluzole
Prevents stimulation of glutamate receptors
Prolongs life by ~3 months
What intervention is offered for respiratory impairment in MND?
Non-invasive ventilation (BIPAP) at night
Survival benefit of ~7 months
What is the prognosis in MND?
50% dead within 3y
How should nutrition be provided in late stages of MND?
Percutaneous gastrostomy tube
a/w prolonged survival
What can be used for muscle spasticity in MND?
Quinine
Baclofen
What can be used for excessive saliva in MND?
Glycopyrronium bromide
