CT Case 016

There is extensive subarachnoid haemorrhage (SAH) throughout the basal cisterns, the occipital horns, the fourth ventricle and the cerebral aqueduct.

There is enlargement of the temporal horns of the lateral ventricles (consistent with hydrocephalus).

This is a very typical suprasellar distribution of non-traumatic subarachnoid haemorrhage secondary to a ruptured aneurysm, in contrast to acute traumatic SAH which is more commonly seen in the sulci. Most aneurysms are located at the branches of the Circle of Willis.

Image 4 demonstrates well the difference between subarachnoid blood and calcified choroid plexus.

The choroid plexus is located within the ventricles of the brain, its primary function is to produce CSF. Overtime it can become calcified, appearing hyperdense on CT.

Sometimes those new to reading CT scans will notice the calcified plexus and ask if this is intraventricular blood.

However, the location of the two is very different. Blood will move with gravity, and is therefore seen in the occipital horns in a supine patient. You will notice the blood fluid level.

The choroid plexus however is not mobile, so will not be seen in the most dependent position.

• Nickson C. Subarachnoid Haemorrhage (SAH). LITFL