Is it a stroke?

Professor Charles Warlow discusses some common pitfalls in the early diagnosis of stroke 

  • Date: 01 January 2014

DIAGNOSING a stroke should be easy – very easy. After all, sudden onset of a focal neurological deficit can hardly be anything else. By sudden, I do mean sudden. The onset occurs at a recognisable moment in time and, if asked, the patient can generally recall what they were doing when it happened. And by focal I mean not a general perturbation of brain function (like feeling faint or woozy in the head, or losing consciousness) but some manifestation of a focal lesion in the brain like weakness or numbness down the whole or part of one side of the body, losing vision to one side, difficulty thinking of words, difficulty in finding one’s way about, double vision or serious imbalance.

In stroke, after the sudden onset, the focal deficit may worsen, the patient may lapse into coma, and about one third die. But the rest improve over days, weeks and months and many recover completely. If the patient survives but does not improve, something else may be going on, perhaps a brain tumour (unlikely to have been missed on CT scan, but it does happen) or something very obscure (in which case call an obscure specialist, i.e. a neurologist).

When the diagnosis is tricky and liable to be missed

If anything, stroke is over-diagnosed these days, particularly in clinics devoted to stroke and particularly now that doctors fear the sins of omission far more than the sins of commission. What can be so wrong in unnecessarily prescribing a statin even if the patient only has migraine, against failing to start secondary stroke prevention in someone with a mild stroke or transient ischaemic attack who goes on to have a stroke and then sues the doctor for negligence? Quite a lot in my view, but that is another subject.

The usual culprits in over-diagnosis (or misdiagnosis) are:

  • migraine aura
  • functional problem (i.e. symptoms without disease) which is not confined to young people or even to people who are overtly depressed or anxious
  • a space-occupying lesion such as a tumour or subdural haematoma
  • occasionally hypoglycaemia
  • multiple sclerosis
  • possibly focal epilepsy.

Even a peripheral nerve lesion can confuse some people. Some diagnoses will appear on brain imaging but not all. The history and examination may still be all one has to rely on, even these days. And if you can’t manage that yourself, refer the patient to someone who can – after all neurology gets really interesting and indeed challenging when the scan is normal but the patient is not.

Missing the diagnosis of stroke is particularly problematic in young people who are so unlikely to have a stroke compared with an older person. But it happens and, when it does, any stroke is not due to atheroma but more likely to:

  • Dissection of the neck arteries: ask directly about indirect trauma like a car crash, being grabbed round the neck etc. This is a fruitful area for litigation not against the doctor but whoever was responsible for the trauma
  • Embolism from the heart: check the heart and rhythm
  • Haemorrhage due to an intracranial vascular malformation.

Sometimes stroke even happens inexplicably out of the blue and no cause is ever found (although the oral contraceptive is often blamed if a woman is taking it which some, but not all, are).

Missing the diagnosis is also an issue if the patient does not appear to have any focal symptoms. So beware the “stroke somewhere, stroke nowhere, stroke in the cerebellum” scenario. The patient has suddenly become unwell or disabled (stroke somewhere) but there do not appear to be any neurological signs (stroke nowhere). However, often doctors don’t stand the patient up; if they do and the patient falls over the diagnosis is obvious (stroke in the cerebellum).

This “stroke nowhere” business also applies to strokes in the thalamus where the only symptom might be loss of memory, perhaps along with some sleepiness – but the clue as ever is the sudden onset, “out of the blue”. Sometimes stroke in the right parieto-occipital region can be very difficult if all the patient complains of is vague difficulty with their vision, maybe not recognising places and people. It is all too easy to brush off the symptoms as psychological, but again the clue is that they came on all of a sudden – one day they were there, the day before they were not.

Early diagnosis: delays can matter

Not so long ago it really didn’t matter too much if the diagnosis of stroke was delayed for hours or even a day or two. It didn’t even matter if the diagnosis was completely missed, provided the patient recovered, because until the 1980s there was no intervention that would reduce the risk of another stroke.

Now it does matter because intravenous thrombolysis is, or at least should be, available. Although this treatment is no panacea (anymore than thrombolysis for acute myocardial infarction), it does on average across a population of stroke patients reduce somewhat the risk of dying or being left dependent, and it may even reduce the level of dependency of patients not all that affected in the first place. Thrombolysis does not work for everyone, but is most likely to be helpful if the patient is treated within six hours, better in under three hours, and in someone whose stroke is not already getting better.

Of course thrombolysis is contraindicated if the stroke is due to haemorrhage, so everyone needs a CT brain scan first. Upsetting as it may be for the neurologists who prefer the comfort of their outpatient clinic to the hurly burly of an acute ward, stroke patients are now blue light medical emergencies. Recently qualified doctors know this; older ones may not be so aware. In their day stroke was ‘untreatable’.

“No history available”

What nonsense – there is always some history from someone if one bothers to look for it. But how often does one see these three weasel words written in medical notes! Apart from the patient, has anyone else been asked what happened – paramedics, friends, relatives, bystanders, police? This issue is important for inebriated patients who are found unconscious where a cut on the head might be due to falling as a result of a stroke rather than alcohol. The presence of focal neurological signs should be one clue to do a scan, but of course rather than a stroke one might find a subdural haematoma which is certainly useful to know about.

A sound history is also important for anyone who is otherwise unable to give their own history, particularly if they are dysphasic. Dysphasia can be misinterpreted for psychosis if you are not careful to listen to how the patient is speaking. Are their words wrong, jumbled up, rather than just slurred?


  • Take a decent history and not just from the patient. Was the onset sudden? Exactly when did it all start? What exactly seems to be wrong?
  • Make an attempt at the neurological examination. It does sometimes matter a lot, e.g. radial nerve palsy vs stroke.
  • If in doubt ask for help, and fast if there has been an apparently sudden onset of focal neurological symptoms in the previous few hours.
  • And again ask for help if the patient keeps coming back with the same problem and you have not got a sensible diagnosis, even if the brain scan is normal.

Charles Warlow is Emeritus Professor of Medical Neurology at the University of Edinburgh

This page was correct at the time of publication. Any guidance is intended as general guidance for members only. If you are a member and need specific advice relating to your own circumstances, please contact one of our advisers.

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