Motor neuron disease (MND) is a spectrum of neurodegenerative disorders that selectively affect motor neurons.

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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

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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

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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

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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

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Prognosis

Poor prognosis:

• Later age of onset
• Bulbar involvement
• Short diagnostic interval
• ALS/PMA variant