Introduction
Motor neuron disease is a neurological condition of unknown cause which can present with both upper and lower motor neuron signs. It rarely presents before 40 years and various patterns of disease are recognised including amyotrophic lateral sclerosis, progressive muscular atrophy and bulbar palsy.
Epidemiology
- Incidence: 2.00 cases per 100,000 person-years
- Peak incidence: 60-70 years
- Sex ratio: more common in males 2:1
| <1 | 1-5 | 6+ | 16+ | 30+ | 40+ | 50+ | 60+ | 70+ | 80+ |
Clinical features
There are a number of clues which point towards a diagnosis of motor neuron disease:
Other features
*vague sensory symptoms may occur early in the disease (e.g. limb pain) but 'never' sensory signs
- fasciculations
- the absence of sensory signs/symptoms*
- the mixture of lower motor neuron and upper motor neuron signs
- wasting of the small hand muscles/tibialis anterior is common
Other features
- doesn't affect external ocular muscles
- no cerebellar signs
- abdominal reflexes are usually preserved and sphincter dysfunction if present is a late feature
*vague sensory symptoms may occur early in the disease (e.g. limb pain) but 'never' sensory signs
Investigations
The diagnosis of motor neuron disease is clinical, but nerve conduction studies will show normal motor conduction and can help exclude a neuropathy. Electromyography shows a reduced number of action potentials with increased amplitude. MRI is usually performed to exclude the differential diagnosis of cervical cord compression and myelopathy
Management
Motor neuron disease is a neurological condition of unknown cause which can present with both upper and lower motor neuron signs. It rarely presents before 40 years and various patterns of disease are recognised including amyotrophic lateral sclerosis, progressive muscular atrophy and bulbar palsy
Riluzole
Respiratory care
Riluzole
- prevents stimulation of glutamate receptors
- used mainly in amyotrophic lateral sclerosis
- prolongs life by about 3 months
Respiratory care
- non-invasive ventilation (usually BIPAP) is used at night
- studies have shown a survival benefit of around 7 months
Prognosis
Prognosis
- poor: 50% of patients die within 3 years