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Upper Motor Neuron Weakness

 
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Overview

  • Signs of Upper Motor Neuron Weakness

  • Minimal muscle wasting
  • Spasticity (clasp-knife rigidity) - velocity-dependent increase in tone
  • Clonus - rhythmic contractions in response to a sudden stimulus, e.g. sudden ankle dorsiflexion
  • Reduced power
  • Hyperreflexia
  • Upgoing plantar reflex
  • Significance

  • The presence of upper motor neuron weakness suggests a lesion within the central nervous system, involving the cerebrum, brainstem or spinal cord.
  • Causes of Upper Motor Neuron Weakness

  • Ischaemia - ischaemic stroke, spinal cord infart
  • Haemorrhage - subarachnoid haemorrhage, intracerebral haemorrhage
  • Traumatic brain injury
  • Tumour - astrocytoma, meningioma, brain metastases, spinal cord neoplasia
  • Infection - encephalitis, PML, brain abscess
  • Demyelination - ADEM, multiple sclerosis
  • Hereditary spastic paraparesis
  • Idiopathic transverse myelitis
  • CNS vasculitis
  • Sarcoidosis
  • Syringomyelia
  • Prion disease
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