A CT showing early signs of a middle cerebral artery stroke with loss of definition of the gyri and grey white boundary Dens media sign in a patient with middle cerebral artery infarction shown on the left. Right image after 7 hours. Stroke is diagnosed through several techniques: a neurological examination (such as the NIHSS), CT scans (most often without contrast enhancements) or MRI scans, Doppler ultrasound, and arteriography. The diagnosis of stroke itself is clinical, with assistance from the imaging techniques. Imaging techniques also assist in determining the subtypes and cause of stroke. There is yet no commonly used blood test for the stroke diagnosis itself, though blood tests may be of help in finding out the likely cause of stroke. In deceased people, an autopsy of stroke may help establishing the time between stroke onset and death. Physical examination A physical examination, including taking a medical history of the symptoms and a neurological status, helps giving an evaluation of the location and severity of a stroke. It can give a standard score on e.g., the NIH stroke scale. Imaging For diagnosing ischemic (blockage) stroke in the emergency setting: * CT scans (without contrast enhancements) : sensitivity= 16% (less than 10% within first 3 hours of symptom onset) : specificity= 96% * MRI scan : sensitivity= 83% : specificity= 98% For diagnosing hemorrhagic stroke in the emergency setting: * CT scans (without contrast enhancements) : sensitivity= 89% : specificity= 100% * MRI scan : sensitivity= 81% : specificity= 100% For detecting chronic hemorrhages, MRI scan is more sensitive. For the assessment of stable stroke, nuclear medicine scans SPECT and PET/CT may be helpful. SPECT documents cerebral blood flow and PET with FDG isotope the metabolic activity of the neurons. CT scans may not detect an ischemic stroke, especially if it is small, of recent onset, or in the brainstem or cerebellum areas (Posterior circulation infarct). MRI is better at detecting posterior circulation infarct with diffusion-weighted imaging. A CT scan is more to rule out certain stroke mimics and detect bleeding. Underlying cause T-waves. Various ECG changes may occur in people with strokes and other brain disorders. When a stroke has been diagnosed, various other studies may be performed to determine the underlying cause. With the current treatment and diagnosis options available, it is of particular importance to determine whether there is a peripheral source of emboli. Test selection may vary since the cause of stroke varies with age, comorbidity and the clinical presentation. The following are commonly used techniques: * an ultrasound/doppler study of the carotid arteries (to detect carotid stenosis) or dissection of the precerebral arteries; * an electrocardiogram (ECG) and echocardiogram (to identify arrhythmias and resultant clots in the heart which may spread to the brain vessels through the bloodstream); * a Holter monitor study to identify intermittent abnormal heart rhythms; * an angiogram of the cerebral vasculature (if a bleed is thought to have originated from an aneurysm or arteriovenous malformation); * blood tests to determine if blood cholesterol is high, if there is an abnormal tendency to bleed, and if some rarer processes such as homocystinuria might be involved. For hemorrhagic strokes, a CT or MRI scan with intravascular contrast may be able to identify abnormalities in the brain arteries (such as aneurysms) or other sources of bleeding, and structural MRI if this shows no cause. If this too does not identify an underlying reason for the bleeding, invasive cerebral angiography could be performed but this requires access to the bloodstream with an intravascular catheter and can cause further strokes as well as complications at the insertion site and this investigation is therefore reserved for specific situations. If there are symptoms suggesting that the hemorrhage might have occurred as a result of venous thrombosis, CT or MRI venography can be used to examine the cerebral veins. Misdiagnosis Among people with ischemic strokes, misdiagnosis occurs 2 to 26% of the time. A "stroke chameleon" (SC) is stroke which is diagnosed as something else. People not having a stroke may also be misdiagnosed as a stroke. Giving thrombolytics (clot-busting) in such cases causes intracerebral bleeding 1 to 2% of the time, which is less than that of people with strokes. This unnecessary treatment adds to health care costs. Even so, the AHA/ASA guidelines state that starting intravenous tPA in possible mimics is preferred to delaying treatment for additional testing. Women, African-Americans, Hispanic-Americans, Asian and Pacific Islanders are more often misdiagnosed for a condition other than stroke when in fact having a stroke. In addition, adults under 44 years of age are seven times more likely to have a stroke missed than are adults over 75 years of age. This is especially the case for younger people with posterior circulation infarcts. Some medical centers have used hyperacute MRI in experimental studies for persons initially thought to have a low likelihood of stroke. And in some of these persons, strokes have been found which were then treated with thrombolytic medication.
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