Mixed motor signs

Mixed motor signs
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(Paul Lin) #1

A 78yoM has difficulty walking. He has upgoing plantars (UMN) with absent knee and ankle reflexes (LMN).

What are your differentials for mixed motor neuron signs?


(Hao Tran) #2

DDx:
Motor Neurone Disease
Multiple sclerosis
Spinal cord and PNS pathology


(Paul Lin) #3

Great. Useful mnemonic: “Mixed signs from the cord”

  • MND
  • Subacute combined degeneration (look for dorsal column signs)
  • Friedreichs ataxia
  • Taboparesis from syphillis
  • Conus medilaris compression (not Cauda equina which is below the spinal cord and thus only LMNs of the lower limb)

Suspect when you have both

  • UMN - increased tone, clonus, hyperreflexia, upgoing plantars
  • LMN - fasciculation, wasting, hypotonia, reduced/absent reflexes