Contents
Motor neuron disease (MND) is a spectrum of neurodegenerative disorders that selectively affect motor neurons.
Classification
Type | UMN degeneration | LMN degeneration |
---|---|---|
Amyotrophic lateral sclerosis (ALS) | Yes | Yes |
Hereditary spastic paraplegia (HSP) | Yes | No |
Primary lateral sclerosis (PLS) | Yes | No |
Progressive muscular atrophy (PMA) | No | Yes |
Progressive bulbar palsy (PBP) | No | Yes, bulbar region |
Pseudobulbar palsy | Yes, bulbar region | No |
Etiology
Mixed UMN & LMN (ALS) syndrome
- Compressive myeloradiculopathy
- HIV infection
Pure LMN syndrome
- Multifocal motor neuropathy + conduction block
- Pure motor chronic inflammatory demyelinating polyneuropathy
Toxic neuropathies
- Myasthenia gravis

Pure UMN syndrome
- Cord compression
- B12 deficiency

Non-neurological features:
- Respiratory:
- Progressive respiratory failure (M/C cause of death)
- ENT:
- Dysphagia
- Orthopaedics/neurosurgery:
- Foot drop or other symptoms suggestive of compressive radiculopathy
- Geriatric case:
- Difficulty walking
Diagnosis
Mixed UMN & LMN (ALS) syndrome:
Nerve conduction studies/electromyography
MRI (spinal cord & brain)
Routine blood tests, thyroid function, serum electrophoresis
HIV test (if appropriate risk factors)
Pure LMN syndrome:
Genetic tests (if slowly progressive, suggesting spinal muscular atrophy)
Nerve conduction studies/electromyography for conduction block.
Routine blood tests, thyroid function, serum electrophoresis
Pure UMN syndrome
MRI (spinal cord & brain as appropriate to the level of the neurological signs)
B12/folate
Central motor conduction time (using transcranial magnetic stimulation techniques, not routinely available)
Lumbar puncture
Management
Multidisciplinary approach
- Patient and carer support groups
- Palliative care

Nutrition:
- Percutaneous endoscopic gastrostomy (PEG)
- Endoscopic medical procedure in which a PEG tube is passed into a patient’s stomach through the abdominal wall to provide a means of feeding when oral intake is not adequate


Respiratory care:
- Non-invasive ventilation (NIV)
- Use of airway support administered through a face (nasal) mask instead of an endotracheal tube
- NIV is not the same as continuous positive airway pressure (CPAP), which applies a single level of positive airway pressure throughout the whole respiratory cycle. CPAP does not deliver ventilation but is occasionally used in conditions also treated with NIV
Drug therapy:
- Riluzole
Prognosis
Poor prognosis:
- Later age of onset
- Bulbar involvement
- Short diagnostic interval
- ALS/PMA variant