A CT showing early signs of a middle cerebral artery<unk>  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.<unk>  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<unk>  itself is clinical, with assistance from the imaging techniques. Imaging techniques also assist in determining the subtypes and cause of<unk> . There is yet no commonly used blood test for the<unk>  diagnosis itself, though blood tests may be of help in finding out the likely cause of<unk> . In deceased people, an autopsy of<unk>  may help establishing the time between<unk>  onset and death. Physical examination A physical examination, including taking a medical history of the symptoms and a neurological<unk> atus, helps giving an evaluation of the location and severity of a<unk> . It can give a<unk> andard score on e.g., the NIH<unk>  scale. Imaging For diagnosing ischemic (blockage)<unk>  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<unk>  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<unk> able<unk> , 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<unk> , 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<unk>  mimics and detect bleeding. Underlying cause T-waves. Various ECG changes may occur in people with<unk> s and other brain disorders. When a<unk>  has been diagnosed, various other<unk> udies 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<unk>  varies with age, comorbidity and the clinical presentation. The following are commonly used techniques: * an ultrasound/doppler<unk> udy of the carotid arteries (to detect carotid<unk> enosis) 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<unk> udy 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<unk> s, 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<unk> ructural 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<unk> s 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<unk> s, misdiagnosis occurs 2 to 26% of the time. A<unk>  chameleon" (SC) is<unk>  which is diagnosed as something else. People not having a<unk>  may also be misdiagnosed as a<unk> . Giving thrombolytics (clot-busting) in such cases causes intracerebral bleeding 1 to 2% of the time, which is less than that of people with<unk> s. This unnecessary treatment adds to health care costs. Even so, the AHA/ASA guidelines<unk> ate that<unk> arting 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<unk>  when in fact having a<unk> . In addition, adults under 44 years of age are seven times more likely to have a<unk>  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<unk> udies for persons initially thought to have a low likelihood of<unk> . And in some of these persons,<unk> s have been found which were then treated with thrombolytic medication.
Stroke
Hypoglycemia
Epilepsy
Hypertensive encephalopathy
Subarachnoid hemorrhage
Giant cell arteritis
Migraine 
Bell's palsy