What are the Glasgow Coma Scale Pupils Age Prognostic charts?
The GCS Pupils Age prognostic charts were developed by Gordon Murray, Paul Brennan and Graham Teasdale, and published by the Journal of Neurosurgery in 2018. The charts provide a simple graphical presentation of the probabilities of outcome from traumatic brain injury based on GCS, pupil reactivity, age and CT scan findings.
Perceptions of an acute head injured patient’s prognosis influence clinicians’ management decisions. Nevertheless, despite several decades of interest and descriptions of more than 100 methods for making probabilistic predictions of an individual neurotrauma patient’s outcome, these models have not found a role in clinical practice. A reason may be that clinicians are uneasy about dealing with explicit mathematical probabilities, especially if the process of producing them seems opaque. Whatever the reasons limiting uptake, clinical care itself is exposed to the influence of personal, highly variable subjective opinions, and more effective and acceptable methods of communicating prognosis are needed.
Understanding risks through graphical aids may provide a simpler assessment of risk than more complicated models.
Four prognostic factors contain much of the information about prognosis of people with an acute head injury; GCS, pupil reactivity to light, age, and the findings on Computer Tomography (CT) scan are the most useful investigative index. We therefore investigated ways of combining them to convey information graphically about risks of mortality, or the prospects for independent recovery, after head injury.
We aimed to develop a method of displaying probabilities graphically that would be simple and easy to use, so improving the usefulness of prognostic information in neurotrauma. This builds on our linked paper describing the GCS and Pupils Score (GCS-P) as a tool for assessing neurotrauma clinical severity.
The paper describing our GCS Pupils Age prognostic chart work in more detail can be accessed and downloaded for free from here.
How do I use the GCS-P prognostic charts?
The chart above is one chart from the group of three that is used to estimate 6 month mortality. We will explore in a moment why there are three charts for each outcome.
The chart has two axes, GCS-P and Age. GCS-P is the GCS pupils score. This is calculated by subtracting the Pupil Reactivity Score (PRS) from the Glasgow Coma Scale (GCS) total score:
GCS-P = GCS – Pupil Reactivity Score
Further information on assessment of the GCS can be accessed here.
So, imagine that you are asked to assess a 50 year old patient who has been ejected from the passenger seat of a car at high velocity. They make no eye, verbal or motor movements spontaneously, or in response to your spoken requests. When stimulated their eyes do not open, they make only incomprehensible sounds, and their arms abnormally flex. This can be scored as E1V2M3 using the Glasgow Coma Scale, giving a sum score of 6.
You now test their pupil reactivity to light. Neither pupil is reactive to light. This gives a Pupil reactivity Score (PRS) of 2.
The GCS-P can then be determined as GCS-PRS, which in this case it 6-2 =4.
The estimate of 6 month mortality can then be ascertained by consulting the chart:
The estimate is 33%.
In addition to GCS, pupil reactivity and age, CT findings are the other important predictor of patient outcome. We demonstrated in our paper that analysis of CT scan findings showed the differences in outcome are very similar between patients with or without either a haematoma, or absent cisterns, or subarachnoid haemorrhage. Taken in combination there is a gradation in risk with increasing numbers of any of these abnormalities. A simple extension of the prognostic charts can then be made by stratifying the original charts into three CT groupings: no/only one/two or more CT abnormalities.
Chart A, B, C indicate the probabilities for 1, 2 or 3 CT abnormalities respectively.
Q: How do I read the result for a patient who is 55 years old?
A: This should be read as half way between the 50 and 60 year old age cut offs.
Q: How do I differentiate big and small haematomas?
A: These prognostic tables are developed from data created by the IMPACT and CRASH studies. These studies include patients exhibiting a wide spectrum of haematoma. As such, for these tables, the size of the haematoma or severity of subarachnoid haemorrhage does not need to be separately considered; the size and severity will influence the GCS and pupil reactivity.