Motor Neuron Disease (MND) Flashcards
Briefly describe MND
A cluster of neurodegenerative diseases characterised by loss of neurons in motor cortex, cranial nerve nuclei and anterior horn cells.
Upper and lower motor neurons can be affected. True or false?
True - get mixed signs
Is there sensory loss in MND?
No
Is there sphincter disturbance in MND?
No
Does MND affect eye movements?
No - distinguishes it from myasthenia
What are the types of MND?
Amyotrophic lateral sclerosis (ALS)
Progressive bulbar palsy
Progressive muscular atrophy
Primary lateral sclerosis
In some patients there is a combination of clinical patterns
Describe ALS
Archetypal MND
50% of patients
Loss of motor neurons in cortex and anterior horn of the cord, so combined UMN and LMN signs
In amyotrophic lateral sclerosis, typically LMN signs are seen where?
In arms
UMN signs in legs
In ALS what are some poor prognostic signs?
Bulbar onset
Increased age
Reduced FVC
Describe primary lateral sclerosis
Rare
Mainly UMN signs
Marked spastic leg weakness and pseudobulbar palsy
Describe progressive muscular atrophy
LMN signs only
Affects distal muscles before proximal
Carries best prognosis than ALS
Describe progressive bulbar palsy
Only affects CNs IX- XII
Palsy of tongue, muscles of chewing/ swallowing and talking due to loss of function of brainstem motor nuclei
Carries worst prognosis
What age does MND rarely present before?
40
How does MND present?
Weakness Stumbling, spastic gait Foot drop Proximal myopathy Difficulty rising from chair Weak grip Shoulder abduction Aspiration pneumonia
Look for UMN signs - spasticity, brisk reflexes, up going plantars AND LMN signs - wasting, fasiculation of tongue, abdomen, thigh, back
Is speech or swallow affected?
What is the life expectancy from symptom onset?
3-4 years
MND is associated with what type of dementia in 15% of cases?
Frontotemporal - affects personality and behaviour
What types of respiratory symptoms occur?
SOB on exertion, orthopnia
Can lead to respiratory failure
In ALS can UMN and LMN signs be present in the same muscle
Yes
The cause of MND is unknown. What are some theories?
Premature aging of motor cells
Too much glutamate - excitotoxicity
Genetic component
Exposure to heavy metals and agricultural chemicals
Chronic calcium deficiency, an association with hyperparathyroidism
Is there usually pain?
No
Is the weakness and wasting usually symmetrical?
Yes in 75% and usually in extremities.
Wasting usually begins in hands and spreads. May be unilateral, but develops to bilateral.
Why does fasiculation occur?
Occurs as surviving axons branch out to new motor units and attempts to innervate them.
Fasiculations = motor units discharging spontaneously
How is MND diagnosed?
Clinical signs and symptoms
May be confirmed with electromyography- shows denervation and fibrillation (reduced number of action potentials with increased amplitude)
Nerve conduction studies - will be normal (useful to exclude multi focal neuropathy)
What investigations should be done?
Electromyography
Nerve conduction studies - shows normal motor conduction
MRI - exclude structural causes (will be normal)
LP to exclude inflammatory causes
TFTs to exclude hyperthyroidism
Calcium
Bloods - elevated CK due to muscle breakdown
What is death usually caused by?
Bronchopneumonia as a result of aspiration
What is Riluzole?
Sodium channel blocker - An inhibitor of glutamate release and NMDA receptor antagonist - the only medication to show improved survival
Usually recommended as soon as possible
By how many months does Riluzole increase survival by typically?
3 to 5 months
Most effective if disease has bulbar signs
What type of approach should be taken in terms of treatment management?
MDT approach - neurologist, palliative care team, physio, OT, SALT, dietician, social services, GP
How can spasticity be reduced?
Baclofen - a GABA agonist
Exercise
Orthotics
What can be done for drooling?
Amitriptyline or propantheline
Glycopyrronium bromide
How do you identify those with respiratory insufficiency?
Reduced FVC
When is NIV typically used?
When the patient is sleeping.
During the day respiratory effort by diaphragm is supplemented by accessory muscle use to maintain levels of oxygenation. When entering REM sleep -> sleep paralysis, so diaphragm struggles on own.
There are a number of clues which point towards a diagnosis of MND what are they?
Fasiculations
The absence of sensory signs/symptoms
Mixture of LMN and UMN signs
Wasting of the small hand muscles/ tibialis anterior is common
Doesn’t affect external ocular muscles
No cerebellar signs
Abdominal reflexes usually preserved and sphincter dysfunction if present is late feature
What does amyotrophic mean?
Loss of muscle tone
In Amyotrophic Lateral Sclerosis, the amyotropic part means loss of muscle tone, what does the lateral sclerosis refer to?
Damage to the lateral corticospinal tracts - basically means there is spastic paraparesis.
It is rare to see loss of muscle tone and spastic parapsresis together - except in MND
In MND there are bulbar and pseudo bulbar features in 25% of people. What symptoms does this included?
Dysphagia Dysarthria Nasal regurg (palate weakness) Choking Tongue may be immobile
What is bulbar palsy?
Diseases of the nuclei of CN IX to XII in the medulla
Signs: a LMN lesion of the tongue and muscles of talking and swallowing - facial expression normal
- dysphagia, drooling, nasal regurgitation
- flaccid, fasiculating tongue
- speech quiet, hoarse or nasal
- gag reflex absent
- emotions not affected
- jaw jerk is normal or absent
Causes not just MND, also Guillian Barre, Myasthenia Gravis, brainstem tumours, central pontine myelinolysis, syringobulbia
What is corticobulbar palsy?
UMN lesion of muscles of swallowing and talking due bilateral lesions above the mid pons e.g corticobulbar tracts
- affects CN V, VII, IX, X, XI, XII
Commoner than bulbar palsy
Expressionless face
Difficulty chewing
Dysphagia, drooling, nasal regurgitation
Slow, deliberate speech
Tongue - spastic pointed, no wasting or fasiculation, slow movement
Exaggerated gag reflex and jaw jerk
Pseudobulbar affect - weeping unprovoked by sorrow or mood incongruent giggling
Causes: ALS, PSP, MS, Stroke, injury or malignancy of high brainstem
The first sign of ALS may appear in hand or arm - difficultly with simple tasks e.g buttoning shirt or Turing key in lock. In other cases symptoms initially affect one leg - tripping more.
When symptoms begin in arms or legs= limb onset ALS
Others first notice speech or swallowing problems. What is this termed?
Bulbar onset ALS
Patients with MND often have no cognitive impairment in early stages. True or false
True
Important to plan for the future early - discuss wishes for end of life care
What does electromyography (EMG) show in MND?
Denervation and fibrillation
- denervation may not be present in PLS
EMG : a needle electrode inserted into a muscle to record the electrical activity produced by the muscle
- will show reduced number of action potentials with increased amplitude
How will nerve conduction studies appear?
Normal
Useful to exclude Multifocal neuropathy
NCS measures how fast an electrical impulse moves through nerve. (EMG detects whether the muscle is working properly in response to the nerve stimulus)
What does paraparesis mean?
Partially unable to move legs
Are there cerebellar signs?
No
