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

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