Spot sign | Radiology Signs

Answer:

The spot sign is one or more punctate or serpiginous foci of contrast enhancement within an acute intracerebral haematoma on CT angiography, with no connection to an outside vessel and attenuation typically above 120 HU. It represents active contrast extravasation from ruptured small vessels and is the most robust imaging predictor of haematoma expansion, which is itself the strongest modifiable determinant of outcome. Its predictive strength depends heavily on onset-to-scan time: the sign is common and highly predictive within the first two to three hours and progressively less so thereafter, so timing must be stated when reporting it. Refinements include the number and maximum attenuation of spots, and the demonstration of delayed leakage on a post-contrast delayed acquisition, sometimes called the leakage sign. Mimics that must be excluded are a small aneurysm, an arteriovenous malformation nidus, a cavernoma, calcification on the unenhanced series and a contrast-enhancing underlying tumour, which is why the unenhanced scan must always be compared side by side. Clinically the sign identifies patients for intensive blood pressure lowering, rapid anticoagulation reversal and closer monitoring, and it has been used as an enrichment criterion for haemostatic therapy trials.

Why is it called so?

The extravasated contrast appears as a small bright spot inside the dark haematoma.

Pathophysiology

Spontaneous intracerebral haemorrhage usually arises from rupture of small perforating arteries damaged by chronic hypertension, with lipohyalinosis and Charcot-Bouchard microaneurysm formation, or from cerebral amyloid angiopathy in lobar bleeds. Bleeding is not a single event: the expanding haematoma mechanically shears adjacent small vessels, so bleeding propagates in an avalanche of secondary ruptures. Iodinated contrast leaking from these actively bleeding vessels pools within the clot and is imaged as a dense focus. The same mechanism explains why the sign is time-dependent, since most bleeding stops within a few hours, and why spot number and attenuation scale with the volume of ongoing extravasation.

Alternative names: Contrast extravasation sign; CTA spot sign

Other associated named signs: Swirl sign, the blend sign, the black hole sign and the island sign of haematoma expansion

References

1. Dowlatshahi D, Brouwers HB, Demchuk AM, Hill MD, Aviv RI, Ufholz LA, et al. Predicting Intracerebral Hemorrhage Growth With the Spot Sign: The Effect of Onset-to-Scan Time. Stroke. 2016;47(3):695-700. PMID: 26846857.