Motor Neurone Disease Flashcards
What is Motor Neurone Disease?
A progressive, ultimately fatal condition where the motor neurones stop functioning, with no effect on the sensory neurones (no sensory symptoms = big clue in diagnosis).
What are the risk factors of Motor Neurone Disease?
Genetic - increased risk with some genes.
Familial - 5-10% cases are inherited.
Environmental - increased risk with smoking, exposure to heavy metals and certain pesticides.
Give three epidemiological facts about Motor Neurone Disease.
- Rare presentation before age of 40.
- Median age at onset in UK is 60.
- Ratio of 3:2 between males and females.
Give three features of an UMN disease.
- Hypertonia (Spasticity).
- Hyperreflexia.
- Upgoing Plantar Reflexes.
Give four features of a LMN disease.
- Muscle Wasting (especially small Hand muscles, Tibialis Anterior).
- Hypotonia.
- Fasciculations (Twitches in Muscles e.g. Tongue, Abdomen, Back, Thigh).
- Hyporeflexia.
- Fasciculations are not enough to diagnose a LMN lesion - there must be a weakness too.
Give three features that do not occur in Motor Neurone Disease.
- No effect on External Ocular Muscles.
- No Cerebellar Signs.
- No Sensory Symptoms.
What is the stereotypical patient?
- Late/Middle-aged man (60) with an affected relative.
- Presenting with insidious progressive weakness of the muscles of the body affecting the limbs, trunk, face and speech.
- It first is noticed in upper limbs.
- Increased fatigue when exercising, complaining of clumsiness and dysarthria.
What is the commonest pattern of presentation?
- Name.
- Proportion of Cases.
- Celebrity.
- Gene.
- Presentation.
- Pathophysiology.
- Poor Prognostic Factors.
Amyotrophic Lateral Sclerosis (ALS) - 50-80%.
(Stephen Hawking).
Gene : Chromosome 21 coding for Superoxide Dismutase.
Presentation : Variable Mixture of LMN signs in arms and UMN signs in legs.
Pathophysiology : Loss of motor neurones in the motor cortex and anterior horn of the cord, resulting in both UMN and LMN signs.
Prognosis : Worse if bulbar onset, old or reduced FVC.
What is the 2nd commonest pattern of presentation?
- Names.
- Epidemiology.
- Presentation (Pseudobulbar, Corticobulbar, Bulbar).
- Pathophysiology.
Progressive Bulbar Palsy / Pseudobulbar Palsy / Bulbar and Corticobulbar Palsy.
Epidemiology : Commoner in elderly women. Worst prognosis.
Presentation : Palsy of tongue (2Fs = Flaccid and Fasciculating - like a sack of worms), muscles of mastication and facial muscles.
Pseudobulbar : Pseudobulbar Affect (emotional incontinence without a mood change).
Corticobulbar : Tongue has slow movements with slow deliberate speech and brisk reflexes of jaw, palate and pharynx.
Bulbar : Quiet, hoarse or nasal palsy.
Pathophysiology : Loss of functioning of the brainstem motor nuclei, affecting cranial nerves IX-XII in the medulla.
What is the pattern of presentation with the best prognosis?
- Name.
- Presentation.
- Pathophysiology.
Progressive Muscular Atrophy.
Presentation : LMN signs only, affecting the distal muscles before proximal muscles.
Pathophysiology : Anterior horn cell lesions = LMN signs only.
What is the OTHER pattern of presentation?
- Name.
- Presentation.
- Pathophysiology.
Primary Lateral Sclerosis.
Presentation : UMN signs, affecting legs first, then trunk, then upper limbs, then brainstem.
Pathophysiology : Loss of Betz Cells in the motor cortex.
What is the pathophysiology of Motor Neurone Disease?
Progressive degeneration of both UMNs and LMNs with sparing of the sensory neurones - characteristic loss of neurones in the motor cortex, cranial nerve nuclei and anterior horn cells.
How is MND diagnosed? (2)
- Clinical Presentation and Exclusion of Differentials.
2. Only by a specialist - causes delayed diagnosed.
How can MND be distinguished from MS? (2)
No sensory loss.
No sphincter disturbance.
How can MND be distinguished from polyneuropathies? (3)
No sensory loss.
No sphincter disturbance.
Normal motor conduction on nerve conduction studies.
