CLINICAL RISK REDUCTION
Is it a stroke? D
PHOTO: ZEPHYR/SCIENCE PHOTO LIBRARY Professor Charles Warlow discusses some common pitfalls in the early diagnosis of stroke
IAGNOSING a stroke should be easy – very easy. Aſter all, sudden onset of a focal neurological deficit can hardly be anything else. By sudden, I
do mean sudden. Te 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, aſter 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. Te 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
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people. Some diagnoses will appear on brain imaging but not all. Te 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 – aſter 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. Tis 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 oſten 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. Te patient has suddenly become unwell or disabled (stroke somewhere) but there do not appear to be any neurological signs (stroke nowhere). However, oſten doctors don’t stand the patient up; if they do and the patient falls over the diagnosis is obvious (stroke in the cerebellum).
SUMMONS
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