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Cause of extensor plantar response with loss of ankle jerk

Extensor plantar response is usually associated with brisk ankle reflex .But in certain conditions the plantar response is extensor with absent ankle jerk
  • Subacute combined degeneration.
  • Taboparesis (CPI plus tabes dorsalis).
  • Friedreich's ataxia.
  • Cauda-equina lesion (cauda equina lesion with lesion in conns medullaris)
  • Combined cervical and lumbar spondylosis
Plantar response is flexor with brisk ankle jerk
Sometimes it is observed in anxiety  and thyrotoxicosis (exaggerated deep reflex).