Ankle clonus in critically ill burn patients

[DJ__0]

  I work in a burn center and have had several patients who are critically ill
  with no known upper motor neuron lesion or documented anoxia who exhibit ankle
  clonus with dorsiflexion.  This is always a concern to the PTs who suspect some
  type of UMN lesion,although most patients upon recovery and weaning from the
  vent exhibit no long term problems. Could anyone explain to me what might cause
  this clonus? The most frequent pain meds given prior to dressing changes are morphine
  and versed. I would appreciate any input .Thank you.
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Dear D.J.:
That is an interesting observation. Hypostheses to explain this are:
1. Anxiety, pain, hyperadrenergic state. Clonus can occur even in normal individuals who are very tense and anxious.
2. Metabolic encephalopathy. Clonus can occur transiently in encephalopathy from verious causes.
3. Possible mild central pontine myelinolysis related to osmolar fluctuations from burns.

About as frequently, especially in the very ill who are on the ventilator for long, one sees areflexia from critical illness neuropathy/myopathy.