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Presentation

Typically patients present with symptoms in one muscle group, for example, weakness and wasting of one hand or a unilateral foot drop.

  • lower motor neurone (LMN) or upper motor neurone (UMN) signs may be present elsewhere on examination
  • also typical to find evidence of LMN and UMN features in the same limb, for example, leg muscle wasting and fasciculation in combination with increased muscle tone, exaggerated reflexes and an extensor plantar response
  • some patients may present with acute respiratory symptoms 
  • as the disease progresses other muscle groups become involved (MND Australia 2011).

MND Australia 2011

Motor neurone disease is characterised by progressive degeneration of motor neurones:

  • anterior horn cells in the spinal cord - resulting in lower motor neurone (LMN) lesions:
    • skeletal muscle wasting and fasciculation
    • reduced muscle tone and stretch reflexes
    • weakness of limb, trunk and respiratory muscles
  • cranial motor nuclei in the brain stem - resulting in LMN weakness of the facial, jaw and bulbar muscles (bulbar palsy)
  • upper motor neurone (UMN) lesions in the motor cortex - resulting in degeneration in corticobulbar and corticospinal pathways:
    • spastic weakness of cranial and bulbar muscles (pseudobulbar palsy)
    • spastic weakness of limb and truncal muscles
    • exaggerated jaw, gag and cough reflexes
    • pseudobulbar affect - emotional lability
    • exaggerated limb stretch reflexes and extensor plantar responses