A small hyperdense focus on head CT is a spot brighter than the surrounding brain. I am talking about a tiny spot less than say 5 mm. Bright spots or hyperdense areas in the brain in general can be caused by blood, calcification, clot, masses, and blood vessels. Hyperdense spots in the brain can be single or multiple. They are usually not associated with symptoms or are incidental findings.
I would say the most common reason for finding this is artifact and image noise. Small little bright spots can be seen throughout the brain if you look carefully. Sometimes several of these spots come together to form a bigger bright spot. This may cause some confusion and be mistaken for a bleed or other abnormality. Often an MRI will clear this up and demonstrate nothing abnormal in the region.
A small hyperdense focus on head CT can be a calcifications. I most commonly see these small calcifications related to old healed neurocysticercosis or pork tapeworm infection. I see this most commonly in patients from Latin American countries. It is much less common to see this in the active phase of infection. Calcifications related to other infections,metabolic disease and old insults to the brain are also possible. Small hyperdense foci can rarely represent spread of cancer to the brain. This is best evaluated with MRI.
A small hyperdense focus in the brain can be a bleed. Bleeds in the brain can be along the surface of the brain and it’s meninges. These are often from trauma. Brain bleeds can also be within the brain itself, say from a bruise or from some underlying lesion that bled. These types of bleeds can in some cases be subtle and seen as a small hyperdense focus on head CT. MRI can provide a better look at these areas.
Small hyperdense foci on head CT can be blood vessels. If you look carefully at different planes you can see them as elongated tubular structures. Sometimes when you cut a vessel in one plane it can look like an abnormality. A hyperdense focus on head CT can also be a vascular malformation. These are divided into categories depending on whether there is low or high flow in them. MRI and MR studies of the blood vessels are best to evaluate these.
Small hyperdense Foci on head CT can have many different causes from benign artifacts to brain bleeds and malformations of blood vessels. Sometimes it’s not possible to tell using head CT alone what the cause is. The clinical history along with MRI and specialty consult will be helpful.