The hyperdense vessel sign is a radiological sign appreciated on non-contrast CT brain whereby there is focal hyperattenuation (mean of approximately 55 HU) within an intracranial blood vessel 1,2. Notably, this is a distinct sign to the hypodense vessel sign.
The hyperdense vessel sign is often used synonymously with hyperdense artery sign, which may be appreciated in the setting of hyperacute ischaemic stroke, but hyperdense vessel sign may also be used more liberally to refer to a hyperdense cerebral vein or venous sinus in the setting of cerebral venous sinus thrombosis 1.
In the context of hyperactive ischaemic stroke, the hyperdense vessel sign represents the acute intraluminal thrombus, and is the earliest radiographic feature of ischaemic stroke 1,2. It may be appreciated in any large vessel occlusion, including occlusions of the proximal middle cerebral artery segments (see hyperdense MCA sign and MCA dot sign), intracranial internal carotid artery, anterior cerebral artery, posterior cerebral artery, basilar artery, and intracranial vertebral artery 1,2. Rarely, the hyperdense vessel segment may have a higher radiodensity suggesting calcium (e.g. ~160 HU), due to calcified cerebral embolism 3. The MRI equivalent of a hyperdense artery sign in this setting is the susceptibility vessel sign 4.
Similarly, in context of cerebral venous sinus thrombosis, the hyperdense vessel sign again represents the intraluminal thrombus 1. It is less commonly seen than its arterial counterpart 1. When present (see dense vein sign and cord sign 5), the hyperdense vessel sign is most seen in the superior sagittal sinus, transverse sinus, straight sinus, and cortical veins 1.
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History and etymology
The hyperdense vessel sign was first described by Gyula Gács (fl. 2024), a Hungarian neurologist-psychiatrist, in a 1983 case series of seven patients with the hyperdense MCA sign and one patient with a hyperdense posterior cerebral artery 6.
Differential diagnosis
intravascular calcification (e.g. intracranial atherosclerotic disease)
elevated haematocrit (e.g. polycythaemia)
relative vessel hyperattenuation due to surrounding parenchymal hypoattenuation (e.g. in HSV encephalitis mimicking a hyperdense MCA sign)
beam hardening artifact (e.g. in interpretation of the basilar artery for this sign)
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