Reliable assessment of the Glasgow Coma Scale is key to user satisfaction and to the conduct of good quality clinical care and research. Along with its spread, varying approaches to assessment emerged over the years after the Scale was described, but none provided sufficient reason to make more than minor alterations to the content of the scale and its application. The goal of the modern structured schema is therefore to reinforce a standard approach to assessment and hence to enhance the consistency of its use.
The structured approach (Nursing Times 2014; 110: 12-16 ) clearly defines the steps taken in assessing each component of the scale. It sets out standardisation in stimulation and an emphasis on reporting of the three components rather than the total sum. These steps are detailed in the video. Each step is related to assessment against a specific criterion. These are summarised in the downloadable GCS Do it this way Aid.
The development of the structured assessment drew on input from a range of medical, surgical and nursing specialists across the world to identify areas of satisfaction with the Coma Scale and where ‘improvements’ might be made. We highlight important topics here.
Eye and Verbal Scales
The numbers of steps in these two components of the Scale have not been changed since it was first described but the terms applied to some findings were updated.
Eye opening ‘to pressure’ replaced opening ‘to pain’, in part to reflect accurately the nature of stimulus used; in part also because of reservations about the concept of pain as a component of care and in part because of uncertainty if painful sensation is necessary or even possible in a patient in coma.
In the verbal scale ‘inappropriate words’ and’ incomprehensible sounds’ were simplified to ‘words’ and ‘sounds’.
The makeup of the 5 step motor component of the scale was altered in 1976 by the incorporation of an additional, 6th step: the introduction of differentiation between “normal” and “abnormal” flexion. (Acta Neurochirurgica. 1976 34: 45-53) Earlier studies of observer variability had shown that this distinction was difficult for less experienced staff, so it was not included in original descriptions. However, the findings of studies, using early clinical features, collected by researchers, began to show that the distinction was useful in prognosis. This led to the so-called ‘extended’ motor scale being adopted. This was first for research, but it was then progressively taken up in routine clinical care and is now the most widely used system.
The transition between abnormal and normal flexion is only rarely a key factor in decision-making about individual patients and the original simpler scale also remained in use, giving rise to the potential for confusion between two systems. To resolve confusion, it is now recommended that the extended six point motor scale is used for all purposes. Reliable application of all parts of the motor scale should be achieved by the guidance now provided in the video and structured approach.
Teasdale G Jennett B Assessment and Prognosis of coma after head injury. Acta Neurochir Suppl (Wien). 1976 34 45 – 55)
The technique of stimulation to be used to elicit responses was not tightly specified in the original 1974 report. A year later (Nursing times, 1975; 71: 972-973) a more detailed description of practical use of the Glasgow Coma Scale referred to locations for stimulation being finger nail bed, trapezius muscle and supraorbital notch.
The assessment of motor responses in people not obeying commands continues to take account of information from finger pressure and trapezius / supraorbital sites. In practice the sequence will usually be in that order, finger tip pressure having been used first it when eye opening does not occur spontaneously or to sound. Some concerns have been expressed that undue force exerted repeatedly on the finger nail bed can produce damage (albeit very rarely); pressure on the side of the finger has been proposed as an alternative. In the absence of evidence about the equivalence of the responses to the different sites, the fingernail continues to be recommended, peripherally rather than proximally, with variation over time in the finger stimulated in any given patient.
Both trapezius and supraorbital sites are recommended for central stimulus in a standard sequence of graded intensity. Information about the relative performance of these two different stimuli would be a useful topic for future research. Pressure behind the jaw,(retromandibular / styloid process) is difficult to apply accurately and is not recommended for routine use. Stimulation by rubbing the knuckles on the sternum is strongly discouraged; it can cause bruising and responses can be difficult to interpret.
Teasdale G. Acute impairment of brain function-1. Assessing 'conscious level'. Nursing Times.1975 71(24):914-7
Teasdale G, Allen D, Brennan P, McElhinney E, Mackinnon L. The Glasgow Coma Scale: an update after 40 years. Nursing Times 2014; 110: 12-16