← All lessons

Signs · 2 min read

Early ischaemic signs on unenhanced CT

The subtle signs of an early middle cerebral artery infarct on a plain head CT: the insular ribbon, the lentiform nucleus and the grey-white border.

Key points

• Early ischaemic signs on unenhanced CT include a hyperdense middle cerebral artery, loss of grey-white differentiation, the insular ribbon sign, parenchymal hypodensity and sulcal effacement.
• In the deep middle cerebral artery territory, early signs are blurring of the edge of the lentiform nucleus and loss of the insular ribbon.
• Compare the two sides on the same slice: the normal side keeps a sharp grey-white border.
• ASPECTS divides the middle cerebral artery territory into ten regions so that early change can be recorded region by region.

Why the first CT can look almost normal

In the first hours of an ischaemic stroke, the brain has not yet changed much on CT. The signs are there, but they are quiet: a slight loss of the difference between grey and white matter, a border that is a little less sharp than it should be. Learning to see them starts with knowing where to look.

The signs

The early ischaemic signs on unenhanced CT are:

• a hyperdense middle cerebral artery, the artery itself looking brighter than its partner;
• loss of grey-white differentiation;
• the insular ribbon sign, loss of the thin grey line of the insular cortex;
• parenchymal hypodensity;
• sulcal effacement, the sulci over the affected area becoming hard to see.

Where to look first

In the deep territory of the middle cerebral artery, two places show change early. The first is the insula: normally a thin ribbon of grey cortex sits against the white matter beneath it; in early ischaemia that ribbon fades into its surroundings. The second is the lentiform nucleus: its normally crisp edge blurs.

In the image above, compare the two sides at the level of the basal ganglia. On the patient's right, which is the viewer's left, the insular ribbon is less distinct and the edge of the lentiform nucleus is softer than on the other side. Comparing like with like on the same slice is the most reliable habit you can build.

A shared language: ASPECTS

ASPECTS divides the middle cerebral artery territory into ten regions, so that early ischaemic change can be recorded region by region instead of as a single impression. It gives readers a common way to describe the extent of early change on CT.

A practical habit

Scroll up and down through the basal ganglia, then the level just above them. At each level, ask the same question on both sides: is the grey-white border as sharp here as on the other side? If not, describe where.

Check yourself

Which of these is an early ischaemic sign on unenhanced CT?

1. A. Loss of the insular ribbon
2. B. Ring enhancement
3. C. Dense calcification
4. D. A fluid-fluid level

Show the answer

Sources

1. Mendizabal JE, Lurie DN, Greiner FG, Shah AK, Zweifler RM. Baseline computed tomography changes and clinical outcome after thrombolysis with recombinant tissue plasminogen activator in acute ischemic stroke. J Neuroimaging 2001;11(2):101-104. doi:10.1111/j.1552-6569.2001.tb00018.x · PMID 11296577
2. Nakano S, Iseda T, Yoneyama T, Wakisaka S. Early CT signs in patients with acute middle cerebral artery occlusion: incidence of contrast staining and haemorrhagic transformations after intra-arterial reperfusion therapy. Clin Radiol 2006;61(2):156-162. doi:10.1016/j.crad.2005.08.016 · PMID 16439221
3. Barber PA, Demchuk AM, Zhang J, Buchan AM. Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy (ASPECTS). Lancet 2000;355(9216):1670-1674. doi:10.1016/s0140-6736(00)02237-6 · PMID 10905241