CT angiographic spot sign (intracerebral hemorrhage)

The spot sign is a CTA sign in acute intracerebral hemorrhage representing the focal accumulation/pooling/extravasation of contrast containing blood within the hematoma. It is an important feature to identify during the evaluation of acute intracerebral hemorrhage as it significantly increases the likelihood of hematoma growth. 

Terminology

The spot sign generally defined as a unifocal region of contrast enhancement resulting in focal increased density compared to the surrounding hematoma on CT angiography. The shape is not important and it can be spherical, linear or branching.

The spot sign should not be confused with the dot sign consisting of a hyperdense thrombus within an artery seen in cross-section (e.g. MCA branches within the Sylvian fissure on axial imaging). 

Epidemiology

Of those patients scanned within 6 hours of symptom onset, about 30% will demonstrate the spot sign ². This will depend, however, on the technique used; higher in dynamic CTA and lower in delayed CTA. 

Pathology

The exact etiology of the spot sign remains unclear and multiple processes may be involved. Generally, it is believed that it represents active extraluminal accumulation/extravasation of contrast, although this does not imply active bleeding as only a subset of patients with a spot sign will demonstrate hemorrhage growth ^4,6.

It is worth noting that the term has been used perhaps imprecisely by some authors who have included false aneurysms arising from a damaged vessel and visible on angiography ⁵ or group small "contained" foci of enhancement with larger regions of extravasation ⁴. 

Radiographic features

CT

The spot sign is seen on CTA source images or delayed images as a small focal region of contrast enhancement within the hematoma. Research studies have applied additional definitional criteria:

1. discontinuous with any visible vessels (normal or abnormal) around the hematoma ^2,12

2. attenuation greater than twice that of the surrounding hematoma ² or at least 120 HU ¹²

3. measures 1-2 mm ¹ or at least 1.5 mm diameter ²

4. not corresponding to a hyperdensity on the noncontrast CT ²

A region of lower attenuation may be seen at its location representing non-clotted blood. The presence of these hypodensities on non-contrast studies is not well correlated with the spot sign and their presence is an independent predictor of hematoma growth ¹¹. They are similar and probably equivalent to a focal swirl sign. 

Treatment and prognosis

The spot sign is an independent predictor of intracerebral hemorrhage growth and poor outcome ². Multiple spot signs correlate with increased risk of hematoma growth ⁹. The converse is also true, and the absence of a spot sign suggests that the hematoma is unlikely to significantly increase in size ¹⁰. 

Trials of hemostatic therapy — e.g. recombinant activated factor VII (SPOTLIGHT and STOP-IT) and tranexamic acid (STOP-AUST) — in intracerebral hemorrhage patients have utilized the 'spot sign' to identify patients who are most likely to benefit from therapy. They have, however, so far failed to demonstrate a clear benefit from either therapy although this may be due to timing of therapy ^7,8. 

History and etymology

The sign was first formally described by Wada et al. in 2007 ¹, but the phenomenon was recognized much earlier on conventional angiographic studies performed on intracerebral hemorrhage patients in the pre-CT era ³.

Differential diagnosis

• arteriovenous malformation or aneurysm: in both instances the enhancement is intraluminal

• calcification: choroid plexus, pineal gland, granuloma; thus it is important to ensure it is not hyperdense on non-contrast CT

• tumoral enhancement: gliomas or metastases can present with hemorrhage