Glasgow Coma Scale (GCS) — Scoring, Severity and Exam Traps

The Glasgow Coma Scale (GCS) is a bedside tool that describes a patient's level of consciousness by watching three behaviours: whether the eyes open, how well the patient talks, and how well the patient moves in response to a defined stimulus. It was published in The Lancet in 1974 by the Glasgow neurosurgeons Graham Teasdale and Bryan Jennett. Their aim was simple: to give doctors and nurses a common language for describing consciousness after acute brain injury, so that deterioration could be spotted early and communicated clearly.

The scale was first meant to be charted as three separate responses. A single summed score (3–15) came later (1979), and in 2018 the GCS-Pupils (GCS-P) score was added to fold pupil reactivity into the same number. Today the GCS is used well beyond head injury — in stroke, poisoning, sepsis and any cause of altered sensorium — and it appears in trauma protocols (ATLS), triage tools and intubation decisions.

Each component is scored separately according to the best (highest) response you can elicit. The official Glasgow assessment aid uses slightly updated wording (e.g. 'to sound', 'to pressure', 'normal flexion'); older textbooks use 'to speech', 'to pain', 'withdrawal'. Both describe the same levels and give the same numbers.

For physical stimulation the official aid recommends three sites: fingertip pressure, a trapezius pinch, and pressure at the supraorbital notch. A peripheral stimulus (fingertip) is used to see whether the eyes open or the limb flexes; a central stimulus (trapezius or supraorbital) is needed to test localising, because localising means the hand moves up towards a stimulus above the clavicle.

Read the vignette one component at a time and pick the level that matches best. Examiners like to hide one component in an unusual phrase, so translate each clue before adding.

Two more habits save marks. First, always write the breakdown (E3 V4 M5 = 12) — two patients with the same total can be very different clinically. Second, when a vignette gives only a total ("GCS 10"), map it straight to the severity band and to the management step being asked about.

These bands (mild 13–15, moderate 9–12, severe 3–8) are the ones used by StatPearls, most trauma literature and Indian exam keys. The GCS total is only a first-pass severity label: CT findings, pupils, age and the trend over the next hours matter as much. For NEET PG and INI-CET, answer with 13–15 / 9–12 / 3–8 unless the question defines its own cut-offs.

Sometimes a component simply cannot be tested: the patient has an endotracheal tube or tracheostomy (no speech), severe facial swelling (eyes cannot open), or is paralysed. The official Glasgow guidance is clear: record that component as NT — not testable, and do not substitute a score of 1. Writing V1 for an intubated patient would make them look deeper in coma than they are.

Whichever notation is used, the eye and motor components can still be followed in an intubated patient and their trend remains useful. The motor response is especially valuable because it is independent of speech.

The GCS-Pupils score (GCS-P), introduced in 2018 by the Glasgow group, combines two of the strongest early indicators of outcome after head injury — the GCS and pupil reactivity — into one number. You first work out the Pupil Reactivity Score (PRS) and then subtract it from the GCS.

Example: a patient with E3 V3 M3 (GCS 9) and both pupils briskly reactive has PRS 0, so GCS-P = 9. The same patient with one fixed dilated pupil has PRS 1 and GCS-P = 8. The extra range at the bottom (down to 1) improves prognostic discrimination in the most severe injuries, where plain GCS bunches everyone at 3.

A preverbal child cannot give name, place and date or obey a two-part command, so the adult verbal and motor levels do not fit. Paediatric (modified) GCS versions keep the same 3–15 structure but change the descriptors. They are typically used in children under about 2 years, and many units apply them up to 5 years. Several versions exist and wording differs between institutions, but the logic is the same: the verbal score rewards age-appropriate vocalisation and the motor score rewards normal spontaneous movement.

• Trend matters more than one reading. A fall of 2 or more points, or a drop in the motor score, is a red flag for an expanding lesion. The classic PYQ picture is the lucid interval of an extradural haematoma: GCS 15 after the injury, then rapid deterioration with a fixed dilated pupil on the side of the clot (third-nerve compression from uncal herniation) — urgent surgical evacuation.
• Deep coma with a normal CT after high-speed rotational injury suggests diffuse axonal injury; MRI (especially susceptibility-weighted imaging) shows the small haemorrhages at the grey–white junction, corpus callosum and brainstem.
• GCS ≤ 8 = protect the airway (ATLS primary survey: Airway with cervical spine protection, Breathing, Circulation, Disability, Exposure). 'Disability' is where GCS and pupils are checked.
• Cushing reflex (hypertension + bradycardia + irregular breathing) with a low GCS signals raised intracranial pressure and impending herniation — secure the airway first, then image.
• Outside trauma, GCS is used to describe altered sensorium in poisoning, meningitis, stroke and sepsis, but the head-injury severity bands were designed for trauma.