Posthypoxic myoclonus – early and late

We spoke about hypoxic encephalopathy a few times already. The problem of prognosis for early posthypoxic patients is – in my view – quite simple t0 solve:

  1. Make sure that you are dealing with posthypoxia rather than something else (do an exam, imaging [at least CT], perhaps an EEG).
  2. Use as much information as possible.
    • History
      • Time to (any) resuscitation
      • Initial rhythm
      • Time of resuscitation – may use the total epi dose instead
      • Epidemiology: as always, age, CHD and diabetes are bad
    • Exam
      • If he shows any cortical activity, the prognosis cannot be too bad, so don’t bother with additional tests.
      • Especially look out for reaction to (severe) pain, remembering that brainstem activity is necessary but not sufficient to get a meaningful outcome
    • Tests
      • Remember that most of the old tests (say SSEP) have been developed in old age. They didn’t know anything about hypothermia, temperature management and so on. So beware of old data. Always request new studies to be done.
      • Labs: NSE, S100B (I like those; they have been evaluated in recent times)
      • EEG: probably not good for prognosis (except if zero EEG or burst suppression)
      • SSEP, AEP: This is just as good as testing for reactions to pain, but easier to make objective. Never been evaluated for hypothermic patients.
      • MRI: nice to have for rule-out of structural disease (such as stroke), yet not good for (early) prognosis. After 2 weeks it might be fine, but then we all know the outcome.
      • Posthypoxic status: again, this used to portend a bad prognosis, but nowadays the false positive rate is to high (might be about 7-10%).

But really we want to deal with posthypoxic myoclonus – here you have to distinguish the pt with coma + myoclonus vs. the (more or less) awake recovering patient with post-hypoxic (nearly always action induced) myoclonus. The latter used to be taught as rare, but probably is quite common among resuscitation survivors. As for treatment, I recommend

  • Levetiracetam (piracetam is probably no better)
  • Valproate
  • Lacosamid
  • Zonisamid

Nothing is evidence-based, really, but this is the choice you have.

References:

  • There is a good article in Movement Disorders, but I cannot access it’s full text.
  • See this article for the difference of posthypoxic status vs. Lance Adams.
  • Here is a short review on the topic.
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