11. Motor Neurone Disease and UMN + LMN lesions Flashcards
Define weakness/paresis.
Impaired ability to move a body part in response to will.
Define paralysis.
The ability to move a body part in response to will is completely lost.
Define ataxia/incoordination.
Willed movements are clumsy, ill-directioned and uncontrolled.
Define involuntary movements.
Spontaneous movement of a body part, independent of will.
Define apraxia.
The ability to carry out familiar purposeful movements that is consciously organised is lost in the absence of paralysis or other sensory or motor impairments.
E.G. brushing teeth or striking a match
What are upper motor neurones (UMNs)?
Originate in the cerebral cortex.
Travel to the anterior horn of spinal cord or the brain stem.
What are lower motor neurones (LMNs)?
Originate in the spinal cord.
Travel to muscle/gland it innervates throughout the body.
Where are LMN’s located?
LMN cell bodies are found in the spinal cord or in the cranial nerve nuclei in the brainstem.
Describe the UMN pathway.
- Signal begins in the primary motor cortex in the precentral gyrus.
- UMN is responsible for integrating excitatory and inhibitory signals from the cortex and making signal that will initiate or inhibit voluntary movement.
- The UMN cell bodies are in the primary motor cortex.
- The axons of the UMN travel down through the posterior limb of the internal capsule.
- From there, they continue through the cerebral peduncle in the midbrain, longitudinal pontine fibres, and eventually, the medullary pyramids.
- At the medullary pyramids, the majority (approximately 90%) of the fibres will decussate and continue down the spinal cord.
Describe the LMN pathway.
LMN = is responsible for transmitting signal from the UMN to the effector muscle to perform a movement.
3 types of LMN:
1. Somatic motor neurons
2. Special visceral efferent (branchial) motor neurons
3. General visceral motor neurons
What are muscle spindles innervated by?
Gamma motor neurones.
What is the function of muscle spindles?
Muscle spindles control muscle tone and tell you how much a muscle is stretched.
Give 3 things that modulate LMN action potential transmission to effectors.
- Cerebellum.
- Basal ganglia.
- Sensory feedback.
Give 5 potential sites of damage along the ‘final common pathway’.
- Cranial nerve nuclei.
- Motor neurones.
- Spinal ventral roots.
- Peripheral nerves.
- NMJ.
- Muscles.
Give 4 potential sites of UMN damage.
- Motor cortex lesions.
- Internal capsule.
- Brainstem.
- Spinal cord.
Define motor neurone disease (MND).
An umbrella term that encompasses a variety of specific diagnoses:
- Cluster of major progressive degenerative diseases characterised by selective functional loss of motor neurones in the motor cortex, cranial nerve nuclei and anterior horn cells.
- There is no effect on the sensory neurones and patients should not experience any sensory symptoms.
Name a gene that causes MND.
Is this the usual cause?
SOD1.
Causes rare familial MND - most cases are sporadic.
Give some factors that contribute to the epidemiology of MND.
Smoking
Pesticides
SOD1 & C90RF genes
Is MND symmetrical?
No
Which motor neurones are spared in MND?
- Oculomotor nerve
- Onufs nucleus (controls bladder/continence)
Clinical features of upper motor neurone disease.
‘Everything goes up!’
- Increased tone or spasticity
- Brisk reflexes
- Upgoing plantar responses - positive Babinski’s sign
- Characteristic pattern of limb muscle weakness (pyramidal
pattern):
* Upper limbs extensor muscles are weaker than flexors
* Lower limbs flexor muscles are weaker then extensors
* Finer more skillful movement are impaired
Give the features of upper MND affecting the limbs.
-Pyramidal weakness:
-> Extensors in arms and flexors in legs
- Spasticity
- Brisk reflexes
Clinical features of lower motor neurone disease.
‘Everything goes down!’
- Muscle tone reduced - FLACCID
- Muscle wasting
- Fasciculation - twitches in the muscles
- Visible spontaneous contraction of motor units
- NOT ENOUGH TO DIAGNOSE LMN, NEED WEAKNESS TOO! - Reduced reflexes
- reflexes depressed or absent
Give the features of lower MND affecting the limbs.
- Weakness
- Wasting
- Fasciculations
Describe the pyramidal pattern of weakness in the upper limb.
Flexors are stronger than extensors.
Describe the pyramidal pattern of weakness in the lower limb.
Extensors are stronger than flexors.
Name the 4 clinical patterns of MND.
- ALS - Amyotrophic Lateral Sclerosis
- PLS - Primary Lateral Sclerosis
- PMA - Progressive Muscular Atrophy
- PBP - Progressive Bulbar Palsy
What is the most common form of MND?
ALS - Amyotrophic Lateral Sclerosis.
What is the second most common form of MND?
PBP - Progressive Bulbar Palsy
Which MND clinical pattern affects both UMN + LMN?
ALS - Amyotrophic Lateral Sclerosis
Which 2 MND clinical patterns affect LMN only?
- PMA - Progressive Muscular Atrophy
- PBP - Progressive Bulbar Palsy
Which MND clinical pattern affects UMN only?
PLS - Primary Lateral Sclerosis
Give some general symptoms of MND.
Foot drop
Tripping/falling
Difficulty using hands
Fatigue, sleep disturbance
Anorexia
Frontotemporal dementia
Emotional ability
MND: give 3 limb onset symptoms (for ALS pattern).
- Weakness.
- Clumsiness.
- Wasting of muscles.
- Foot drop.
- Tripping.
MND: give 3 bulbar onset symptoms.
- Dysarthria.
- Slurred speech.
- Dysphagia.
- Wasting and fasciculation of the tongue.
MND: give 3 respiratory onset symptoms.
- Dyspnoea.
- Orthopnoea.
- Poor sleep.
When is the breathlessness worst in MND?
At night or when lying flat
What type of respiratory failure is seen in MND?
Type 2
-> Because it is a problem with the muscles so you are unable to both breathe oxygen in AND CO2 out.
Describe the clinical presentation of ALS (UMN + LMN both).
Weakness + UMN signs + LMN wasting/ fasciculations
(usually in 1 limb)
- Asymmetrical onset
- Upper extremity onset
- Stiffness, with poor co-ordination and balance
- Fasciculations of the tongue
- Positive Babinski sign
- Any corticobulbar signs indicate a worse prognosis:
- Brisk jaw reflex
- Dysarthria (difficulty speaking)
- Dysphagia (difficulty swallowing)
- Sialorrhoea (excess salivation)
What is the long term consequence of amyotrophic lateral sclerosis (ALS)?
Progressive spastic tetraparesis.
Describe the clinical presentation of PBP (LMN only).
BULBAR = Medulla Oblangata affected
- Lower cranial nerves: CN 9,10,11,12 + nuclei
Clinical features:
LMN lesion of the tongue, muscles of talking + swallowing + facial muscles
- Dysarthria
- Dysphagia
- Nasal regurgitation of fluids and choking
- Palsy of the tongue
- Flaccid, fasciculating tongue (like a sack of worms) - Jaw spasms
Who should you suspect MND in (typical patient)?
> 40 yrs.
Stumbling spastic gait, foot drop ± proximal myopathy.
Weak grip (e.g. door handles don’t turn) and shoulder abduction (hair-washing is hard) or aspiration pneumonia.
What is the prognosis of MND like?
Most die in 3 yrs from respiratory failure due to bulbar palsy and pneumonia.
Investigations for MND diagnosis.
Clinical diagnosis on El Escorial criteria (gold standard)
1. Presence of: LMN degeneration by clinical electrophysiological, or neuropathological examination; UMN degeneration by clinical examination: progressive symptoms as determined by history.
- Absence of: Electrophysiological and pathological evidence of other disease processes
1) Definite: LMN + UMN signs in 3 regions
2) Probable: LMN + UMN signs in 2 regions
3) Probably with lab support:
- LMN + UMN signs in 1 region, or UMN sign in more than 1 region + Electromyography (EMG) shows acute denervation in more than 2 limbs
4) Possible: LMN + UMN signs in 1 region
5) Suspected: LMN OR UMN sign only - in 1 or more regions
No specific investigations for MND but tests include:
- Nerve conduction studies (NCS):
-> Evidence of diffuse, ongoing, chronic denervation - EMG (electromyography)
- CT or MRI brain and spinal cord
- Used for finding other causes - Bloods - to look for other causes:
-> FBC, B12, Folate, HIV serology, Lyme disease serology, creatinine kinase - Muscle biopsy
Describe the criteria for clinical diagnosis of MND.
El Escorial criteria (gold standard)
1. Presence of: LMN degeneration by clinical electrophysiological, or neuropathological examination; UMN degeneration by clinical examination: progressive symptoms as determined by history.
- Absence of: Electrophysiological and pathological evidence of other disease processes
1) Definite: LMN + UMN signs in 3 regions
2) Probable: LMN + UMN signs in 2 regions
3) Probably with lab support:
- LMN + UMN signs in 1 region, or UMN sign in more than 1 region + Electromyography (EMG) shows acute denervation in more than 2 limbs
4) Possible: LMN + UMN signs in 1 region
5) Suspected: LMN OR UMN sign only - in 1 or more regions
Treatment for motor neurone disease (MND).
- Oral Riluzole + supportive care - 1st line
- Anti-glutamergic drug: inhibits glutamate release and slows disease progression.
- Prolongs life by 3 months - Ventilatory support
- Non-invasive ventilation (NIV) used at home to support breathing at night improves survival and quality of life. - May additionally also prescribe
- Quinine/Baclofen -> for spasms / cramps
- Hyoscine- sialorrhea
- Specialist MDT support:
* Neurologist, speech & language therapists, occupational therapist, specialist nurse, physiotherapist etc.
Differential diagnosis for MND.
MS or polyneuropathies
Spinomuscular atrophy
Muscular dystrophy
Myasthenia Gravis
Diabetic amyotrophy
Guillain-Barre syndrome
Spinal cord tumours
What distinguishes MND from MS/polyneuropathies?
NO sensory loss or sphincter disturbance in MND.
Affects upper and motor neurones.
How could you distinguish MND from myasthenia gravis?
MND never affects eye movement, Myasthenia gravis will.
3 signs that suggest it is not MND?
- Symmetry
- Incontinence
- Sensory disturbance (MND is specifically of the MOTOR neurones)
- Relapsing-remitting pattern (MND is gradually worsening)
Compare UMN and LMN lesions.
