Head injury is often divided into mild, moderate and severe. These definitions depend on a classification system called the Glasgow Coma Score (GCS). This is a standardized score used worldwide that gauges the depth of coma, and allows tracking of a patient's condition. Here's what it means.

(Dr. Gary Hartstein is the former Chief Medical Delegate for the FIA as well as Formula One's former chief doctor. In the wake of , he has . He doesn't know specifics on Jules's condition, but this is a great explainer to understand what his condition might be and what his prognosis could be. - T.O.)

Marussia F1 driver Jules Bianchi was seriously injured and is reportedly in surgery after crashing…

The immediate approach to a patient with evidence of (or suspected of having) a head injury (and once the airway is opened and secured, oxygen provided, and circulatory status verified) involves assessment of the pupils. Normally, pupils are mid-open, and react to light.

Under some circumstances, that changes. When we remember that the diameter of the pupils is controlled in the brainstem, where most other vital functions are handled, we realise that the pupils can be a marker of significant things happening neurologically.

Dilated pupils that do not constrict with light worry us. A lot. I mean seriously a lot.

One dilated pupil means the brainstem is getting squished to one side by asymmetric pressure above. Not good at all. VERY rapid action is indicated.

There are other pupillary signs – details for us here. Let's move on.

The next thing that's assessed is the GCS. Scores run from a minimum of 3 to a maximum of 8. Scoring allows classification into MILD (GCS 13-15), MODERATE (GCS 9-12) and SEVERE (≤8) head injury. This determines initial management.

When the rescuer looks at the pupils, she's also looking at the eyes. There are four possibilities, and these are given points:

eyes open spontaneously: eyes open when you talk to the victim: eyes open when the victim receives a painful stimulus: no eye opening:

The patient's vocalisation is next assessed. The verbal score is done like this:

oriented: confused: inappropriate, but stil words: sounds only: no verbalisation at all:

Then the patient's movements are considered (the best side if there's a difference):

obeys simple commands: pushes away an "annoying" hand: vague mass reaction to noxious stimulation: highly abnormal generalised flexion response: highly abnormal generalised extension response: no movement at all:

Mild head injury (13-15) is usually what we call concussion. They lose a point because when you leave them alone they shut their eyes, and another because they're confused.

Severe head injury patients lose points with their eyes – usually at best a 2, more often a 1. They lose points on verbal. When we get to these folks fast, they might be speaking. That rapidly becomes mumbles, moans, etc. One point gone each step. And lastly, severe head injury patients often initially show those frightening abnormal responses, which often indicate pressure on the brain from a hematoma.

Enough for now.