Fits, faints, funny turns and fakers. Prolactin to the rescue….NOT

My colleague (Dr Dave) asked me today about the use of a serum prolactin level to diagnose a seizure in a patient presenting with “syncope ? convulsion”.  This is not something I have really done in the past so I thought I would look into it a bit.  Actually I am sitting on the labour ward – employing the principle that a watched CTG never delivers – so I have popped out to blog a bit!

So how to tackle the patient presenting with a “funny turn”.  Well my teaching is that the best test is a rigourous history, covering the patient’s previous medical history / predisposition to seizures / family history and the context in which the seizure occured.  Crucially an accurate description of the actual seizure activity / phenomena is vital to getting clues about the diagnosis, and possibly if there is a focal component to the fit.  Remember to ask about drugs, trauma, sleep correlation and family history.  In my neck of the woods – alcohol is “the causin’ of it all” so ask, then ask again, then ask the wife….

Physical examination is useful to ellicit abnormal neurology post-event, also to look for primary casues of the fit.  But for the most part to exclude seizure mimics.

Investigations I feel are over-weighted in the workup of seizures. The yield of a CT brain on somebody with a generalised seizure is pretty low.  Checking a BSL and ECG is easy, all the other biochem is low yield without something on the history to guide you.  EEG – sounds like a good idea, but is rarely available acutely and has lower-than-you-think specificity / sensitivity.  (Normal people have abnormal EEGs, and epileptics often have normal EEGs!)

So can we use prolactin levels to diagnose a seizure?

after a seizure?]Well, the physiological evidence from Austria suggests an immediate rise, still up at 20 minutes post-ictal and return to normal by 1 hour. So if you are going to do this test – you have to do it in the first 20 – 30 minutes I would imagine, otherwise there would be an increasing false negative rate in the true seizures.

to rule in / out a seizure?]Well, not very is the answer. This 2004 prospective, observational study in Jour of Neurology, gave it a sensitivity of 42%, specificity of 82%. This gives a PPV of 74% and a negative predictive value of 54%. So in summary: For ruling out seizure – “toss a coin in the air for similar accuracy”, to “rule in” a fit – it is 3/4 accurate – I reckon a decent history is in the same ballpark.  Interestingly it has been noted that {prolactin] goes up even after a purely syncopal event.

Well as stated above – the negative predictive value is poor. There are a few studies showing no significant difference between [prolactin] in patients with pseudoseizures and true seizures. So I think you might be wasting your money…

So in Summary:  see this from Neurology 2005.  If you really want to help “rule in” a seizure – then do an early serum prolactin, though I cannot recall a scenario when I needed to do this after taking a decent history.  But – you cannot use it reliably to “rule out” seizures.  Interestingly it has been noted that {prolactin] goes up even after a purely syncopal event


  1. My own view is that isolated and resolved seizure is rarely a life threatening event. When I see these patients I try to rigorously rule out ventricular dysrhythmias as a cause of seizure mimic, mainly with careful history, family history, cardiac exam and ECG.
    I have twice had the pleasure of un-diagnosing epilepsy and sending patients for implantable defibrillators.
    Although epilepsy or seizure is certainly what patients are most worried about it is probably among the more benign diagnostic possibilities in the syncope/seziure differential. It’s important but down on the list of priorities.
    My 2 cents,

  2. Casey Parker says:

    Thanks Dr J
    Great point – missing an arrhythmia is potentially lethal. So make sure it is not VT or other cardiac cause.
    Any chance you might share your “undiagnosis” cases – these are gold.

  3. Minh Le Cong says:

    Thanks Casey for this useful update. I have used prolactin in the past to assess suspected pseudo seizures and have not found it to be all that helpful. Your references are good support for my observations and I will stop ordering those tests!

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