Motor Neuron Disease Flashcards
Define motor neuron disease
Progressive neurodegenerative disorder or cortical, brainstem and spinal motor neurones (UMN and LMN)
What are the types of motor neuron disease
Amyotrophic lateral sclerosis (50-60%) (Lou Gehrig’s disease) → UMN + LMN
Progressive muscular atrophy variant → LMN only
Progressive bulbar palsy variant → Cranial nerves XI-XII (CN11-12) - worst prognosis
Pseudobulbar palsy → UMN lesion
of cranial nerves IX-XII (CN 9-11)
Primary lateral sclerosis variant (Loss of Betz cells in motor cortex) → mainly UMN
General symptoms of motor neuron disease
Progressive muscle weakness (focal or asymmetrical)
Dysphagia: Choking on food, Nasal regurgitation
Dysarthria: Slurring or dysphonia
SOB
Behavioural changes e.g. disinhibition, emotional lability
Sparing of oculomotor, sensory and autonomic function
What nerves are affected in ALS and what are the signs and symptoms
UMN + LMN
Usually one limb initially - foot drop, clumsy weak hand
Wasting
Fasciculations with brisk reflexes + upgoing plantars
Muscle wasting e.g. thenar, dorsal interosseous
What nerves are affected in progressive muscular atrophy variant and what are the signs and symptoms
LMN only
Flail arm/flail foot syndrome
What nerves are affected in progressive bulbar palsy variant and what are the signs and symptoms
CN XI-XII
Tongue: Flaccid, fasciculating tongue
Jaw: brisk jaw-jerk(UMN), Absent jaw-jerk (LMN),
Voice: Nasal ‘Donald Duck’ voice
Dysarthria and dysphagia
What nerves are affected in pseudobulbar palsy and what are the signs and symptoms
UMN lesion of cranial nerves IX-XII
Tongue: Slow movements
Jaw: ↑jaw-jerk
Voice: ‘Hot potato’ speech
What nerves are affected in Primary lateral sclerosis variant and what are the signs and symptoms
Loss of Betz cells in motor cortex → mainly UMN
UMN pattern of weakness
Brisk reflexes
Extensor planter response
No LMN signs
Investigations for motor neurone disease
CK (raised), ESR, anti-GM1 ganglioside Abs (+Ve if multifocal, usually -ve)
MRI brain.spinal cord: exclude structural causes (root/cord compression, brainstem lesion)
EMG: evidence of denervation (fibrillation potentials and positive waves → motor unit potential with large amplitude and long duration)
LP: exclude inflammatory cause
Spiro: ?respiratory function
Nerve conduction studies: Exclude alternative aetiology
Management for motor neurone disease
MDT: Psychological support | Physio | Walking aids | Occupational therapy | SALT | Swallow assessment | Dietician | End-of-life care: Percutaneous endoscopic gastrostomy | Non-invasive ventilation | Hospice
Mainly supportive and symptomatic - no cure
First line: Riluzole (inactivates VGSC and inhibits Glutamate release, monitor LFTs + FBCs) - extends life by 3 months
Second line: Edaravone,
Symptomatic:
- Spasticity → Baclofen, botulinum injections
- Salivation → Anti-cholinergics
- Dyspnoea/resp. failure → NIV
- Anxiety → Opiates or Benzodiazepine
- Dysphagia → NG/PEG
- Pain → analgesia via pain ladder
Complications of motor neurone disease
Depression
Emotional lability
Frontal-temporal dementia
Weight loss
Malnutrition (dysphagia)
Immobility → DVT, aspiration pneumonia
Respiratory failure (weakness of ventilator muscles)
Prognosis for motor neurone disease
Relentless progression | Mean survival is 3 years
