Magnetic resonance angiogram of the neck vessels in a person with Ehlers-Danlos syndrome type IV; it shows a<unk>  of the left internal carotid artery,<unk>  of both<unk>  arteries in their V1 and V2 segments and a<unk>  of the middle and distal third of the right subclavian artery. Such striking episodes of<unk>  are typical for this "vascular" subtype of Ehlers-Danlos syndrome. Various diagnostic modalities exist to demonstrate blood flow or absence thereof in the<unk>  arteries. The gold standard is cerebral angiography (with or without digital subtraction angiography). This involves puncture of a large artery (usually the femoral artery) and advancing an intravascular catheter through the aorta towards the<unk>  arteries. At that point, radiocontrast is injected and its downstream flow captured on fluoroscopy (continuous X-ray imaging). The vessel may appear stenotic (narrowed, 41–75%), occluded (blocked, 18–49%), or as an aneurysm (area of dilation, 5–13%). The narrowing may be described as "rat's tail" or "string sign". Cerebral angiography is an invasive procedure, and it requires large volumes of radiocontrast that can cause complications such as kidney damage. Angiography also does not directly demonstrate the blood in the vessel wall, as opposed to more modern modalities. The only remaining use of angiography is when endovascular treatment is contemplated (see below). More modern methods involve computed tomography (CT angiography) and magnetic resonance imaging (MR angiography). They use smaller amounts of contrast and are not invasive. CT angiography and MR angiography are more or less equivalent when used to diagnose or exclude<unk> . CTA has the advantage of showing certain abnormalities earlier, tends to be available outside office hours, and can be performed rapidly. When MR angiography is used, the best results are achieved in the T1 setting using a protocol known as "fat suppression". Doppler ultrasound is less useful as it provides little information about the part of the artery close to the skull base and in the<unk>  foramina, and any abnormality detected on ultrasound would still require confirmation with CT or MRI.
Vertebral artery dissection
Cervical artery dissection
Carotid artery dissection
Posterior cerebral artery syndrome
Middle cerebral artery syndrome
Anterior cerebral artery syndrome
ROSAH syndrome
Pseudosubarachnoid hemorrhage