We are worried about things like bleeding, fracture, and increased ICP in setting of trauma

Yes, there's a lot going on in this scan. One of the things you likely saw was the hyperdensity in the left cerebellum. It's an intraparenchymal hemorrhage.

There's a touch of subdural hematoma.

There's a bit of subarachnoid hemorrhage.

And there's a left occipital bone fracture that extends down to the skull base.

We all care about seeing whether there is bleeding or not in the brain after trauma, and we should care about that. But there is another finding that we should also care about.

You probably saw that the cisterns around the brainstem had no CSF

Normally, there SHOULD be some CSF in front of the brainstem (arrows) here, around the brainstem here, and again around the brainstem here, but in this case, there isn't.

CSF on CT is a very dark gray, almost black. There should be black around the brainstem, but here there is none.

The CSF spaces around the brainstem are called the BASAL CISTERNS.

No CSF in the basal cisterns = EFFACED basal cisterns (technical term).

There is no CSF because it's been squished away by a swollen brain or something else that's taking up space, like a hematoma.

Effaced basal cisterns = VERY BAD = pressure on the brainstem = brainstem ischemia -----> need immediate action to lower ICP.

The lesson here is that you ALWAYS need to look at the basal cisterns.

Start thinking of how you would make a heuristic out of this:

In the setting of: 

Do this: 

And look:

Now let's look at another patient's scan.