Motor neurone disease (MND) is a progressive neurodegenerative disease. It tends to affect those in their 60s/70s.
There are 3 subtypes of MND:
1) Amyotrophic lateral sclerosis = Classic motor neurone disease
- upper and lower motor neurons affected
- commonest form patterns of onset are
- limb onset
- commonest
- asymmetrical distal weakness – patients often have difficulty opening bottles/writing if hand is affected, or difficulty going upstairs if a foot is affected
- brisk reflexes
- muscle wasting
- bulbar onset
- around 20% of cases start like this
- slurring of speech
- wasting and fasciculation of tongue
- dysphagia
- often associated with emotional lability
- respiratory onset
- rarest form of onset
- dyspnoea
- orthopnoea
2) Primary lateral sclerosis
- pure upper motor neurone disease
- 2% of cases of MND
- look for upper motor neurone features such as
- spasticity
- hyperreflexia
- extensor plantar response
3) Progressive muscular atrophy
- pure lower motor neurone disease
- 4% of cases of MND
- look for lower motor neurone features such as
- muscle wasting
- muscle weakness
- fasciculation
- absent reflexes
- slight male preponderance
- earlier age of onset
- better prognosis than ALS
Most cases are sporadic although around 5-10% of cases are familial; these tend to have a younger onset
Diagnosis of MND is usually clinical with supporting electrophysiological evidence and tests to eliminate other possible diagnoses. Investigations may include:
- Nerve conduction tests
- Electromyography
- Tests to eliminate other conditions which can present similarly, such as:
- Thyroid tests - ? hyperthyroidism
- Calcium - ? hyperparathyroidism
- B12
- Copper
- Lyme serology
- MRI - ? MS
Management can include
- Riluzole (an inhibitor of glutamate release) - recommended by NICE - prolongs life by around 2 months
- NIV if required
- NG feeding if required
- Symptomatic management
- Drooling: Transdermal or sublingual hyoscine, oral atropine, TCA, beta blockers, injection of botulinum toxin to salivary glands, irradiation of parotid gland
- Muscle cramps: quinine, diazepam, phenytoin
- Spasticity: baclofen, dantrolene, tizanidine
- Pain: medications as per pain ladder
- Multidisciplinary team approach
Prognosis:
- most patients die 2 to 3 years after diagnosis
- poorer prognosis if
- onset with bulbar form of MND
- older age at onset
- lower than predicted FVC
- low BMI <18.5
Possible differentials include:
- Cervical radiculomyelopathy
- Benign cramp fasciculation syndrome
- Multifocal motor neuropathy- an important differential as it is treatable
- Inclusion body myositis
- Polymyositis
- Hyperthyroidism
- Hyperparathyroidism
- Vitamin B12 deficiency
- Copper deficiency
- Myasthenia gravis
- Multiple sclerosis
- Lyme disease
- Heavy metal poisoning
