Clinical question: Can a TIA cause syncope?

Gday readers – today I am crowdsourcing an answer to a clinical conundrum.  Sorry no answers – I want to know what you think.

I have been giving a particular tutorial to my trainees for a while now – it is a sort of “choose your own adventure” diagnostic puzzle.

I split my class into 2 groups and ask them to choose a serious of diagnostic “decision points” in order to try and work out what is going on.

It starts with a pair of patients presenting by ambulance post collapse / syncope and now fully conscious on arrival to the ED

–  the patient has a normal BSL from the ambulance and has no focal neurology on arrival.

–  witnesses report a simple collapse, no seizure activity

It is usually a lot of fun, but every time I play this game one of the teams inevitably comes to the conclusion that a TIA is top of their diagnostic probability.

Now, I have done this enough times to be sure that this is more than just chance – there must be something to it.

So here are my questions to you smart folk out there:

Q1:  Have you ever seen a patient with syncope which was due to an ischemic / embolic TIA?

Q2:  In theory – can an embolic TIA cause syncope, and if so –

Q3:  Where does it have to lodge in the cerebral vasculature?

Q4: is this a common belief amongst doctors – did I miss something in Med School?  Is TIA likely in a patient with syncope?


PLease educate me – can TIAs cause syncope?



PS;  Here are some of the twitter comments coming in over the past 24 hours.  Seems  most say no, but never say never.  The old Davidson paper cited from  Clin. Cardiology 1991 is a bit soft for my reading – they called anything where they couldn’t find an alternate diagnosis a TIA – which is a long bow to draw – after all vagally-mediated syncope is pretty common and leaves no trace on subsequent Ix usually.  And this was before much MRI and MRA etc.  Though I think it is fair to say if you work up the patient and they have bilateral 90+% carotid stenoses then you might want to consider a vascular cause over a primary cardiac problem!

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  1. @1: If you talk of LOC in general YES, if you think of strictly syncope NO

    @2: I had a case of a about 60 yr old chap with a transient (but merely >8 hrs lasting) LOC caused by a embolic bi-thalamic ischemia. MRI showed DWI lesions but Patient improved almost fully, so strictly stroke no TIA because of the DWI. Theoretically if this is even more transient and recovery is complete you might call this a TIA? Probably this is still a theoretical but VERY VERY unprobable thing. I would still teach ” cause of syncope can be a TIA = wrong”

    @3: bi-thalamic for example?

    @4:never learned that anywhere. At our German ED it seems that TIA is mostly used as an entry ticked by GPs to get patients admitted (rarely works ;-))

  2. Nothing is never, and some weak-kneed folk will faint at anything, so I’d say you can’t rule it out, but I must say it skews me away from TIA as a cause too rather than towards it. I’ve noticed the same trend of equating syncope with TIA in junior docs though. Got no evidence for you, just heuristics. My tuppence. Opinion only!

  3. For my colleagues and me in med school, this was certainly a common belief that was dispelled by one of our better clinical tutors, but not until close to graduation. I don’t think I learned it anywhere in particular – my thought would be that the concept follows naturally from thinking about stroke as interrupted blood flow to the brain (why *wouldn’t* you lose consciousness?). But as I was taught this rarely if ever is the case in practice as clots or bleeding in the arteries supplying the reticular activating system as exceedingly rare, and that if a patient presents with LoC then stroke/TIA should move further down your differential.

  4. David Berger says

    Never say never. Don’t think I’ve ever seen it, though. At least, not knowingly…

  5. Though uncommon, isolated loss of consciousness can occur from a brainstem TIA / vertebrobasilar insufficiency


  6. Doug Larsen says

    From my understanding, loss of conciousness requires either interupption of brainstem function (as Chris aptly points out) or complete interupption of bilateral cortical hemispheres (i.e. seizure type activity where nothing is working correctly upstairs). So while theoretically possible to bump off your brainstem for a short bit, the latter part seems very unlikely without other symptoms. Makes me lean towards TIA as a cause of syncope as being extremely rare. Just my two cents (for now, seems the US may be getting rid of pennies, so im not sure what my thoughts will be worth in the future)


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