What Is the Glasgow Coma Scale?

Medically Reviewed by Jabeen Begum, MD on October 13, 2022
5 min read

When someone is injured, medical personnel need to be able to evaluate them to provide proper treatment. Different types of injuries have different methods of assessment. One assessment method, used for brain injuries, is the Glasgow Coma Scale.

The Glasgow Coma Scale is a tool used to measure the consciousness of patients who have been through trauma and may have a traumatic brain injury. The scale was developed in 1974 by neurosurgeons at the University of Glasgow’s Institute of Neurological Sciences and today is the preferred method of checking trauma patients. Because the Glasgow Trauma Scale is used for patients who may have a traumatic brain injury, it’s most commonly used in emergency rooms and intensive care units.

Traumatic brain injuries, or TBIs, happen when you receive damage to the brain. There are two types of traumatic brain injuries:

  • Closed brain injuries. Closed brain injuries happen when you receive a violent hit to the head. This results in the brain being shaken or hitting the sides of your skull, causing bruising on the brain or the tearing of blood vessels or brain tissue. Closed brain injuries are usually caused by car accidents, falls, and sometimes sports.
  • Penetrating brain injuries. Penetrating brain injuries happen when something breaks through the skull and enters the brain, such as a bullet.

Mild forms of traumatic brain injury may only affect your brain for a short time. More severe forms of traumatic brain injuries can have long-term complications and even lead to death.

The Glasgow Coma Scale measures the consciousness of a patient with a traumatic brain injury. Because symptoms of a traumatic brain injury worsen over time, the Glasgow Coma Scale can also be used to identify changes in a patient’s level of consciousness.

To calculate a patient’s level of consciousness, the Glasgow Coma Scale measures the following:

  • Eye response: Are the patient’s eyes open? Does the patient open them when prompted?
  • Verbal response: Can the patient speak in sentences and answer questions correctly?
  • Motor response: How does the patient respond to things happening? Can they follow commands?

The resulting scores can help assess the severity of the traumatic brain injury as well as what issues the injury may be causing.

The Glasgow Coma works by taking the scores of each of the three categories and adding them together. The higher that score, the more conscious and alert the patient is. Adjustments are made for disabilities, such as if the patient is on a breathing tube and can't talk.

Eye response. The possible scores for eye response are as follows:

  • Eyes closed for a reason other than injury: Not Testable (NT)
  • Eyes do not open and nothing is interfering with the eyes opening: 1
  • Eyes open to pressure, such as fingertip touches, or to pain: 2
  • Eyes open to sound or upon request: 3
  • Eyes open without stimulus or are already open: 4

Verbal response. The possible scores for verbal response are as follows:

  • Patient can't respond for an unrelated reason (patient is non-verbal or ill, etc): NT
  • No audible response and nothing is interfering with the patient: 1
  • Patient can make sounds, but only moans or groans: 2
  • Patient can speak single words people can understand: 3
  • Patient is confused but able to speak clearly and make sens: 4
  • Patient can speak clearly and correctly answer questions such as name, date, and location: 5

Motor response. The possible scores for motor response are as follows:

  • Patient can't move due to unrelated factors, like being paralyzed: NT
  • Patient can't move arms/legs and nothing is interfering with the patient: 1
  • Patient extends the arm in response to something painful happening: 2
  • Patient flexes or bends the arm in response to something painful happening: 3
  • Patient withdraws from pain but can't touch the source of the pain: 4
  • Patient can reach the source of the pain but can't obey commands: 5
  • Patient can obey commands and can do two different movements- 6

Glasgow Coma Scale interpretation.

Once the assessment has been done, the results are added up:

  • A mild traumatic brain injury has a Glasgow Coma Scale score of 13–15.
  • A moderate traumatic brain injury has a Glasgow Coma Scale score of 9–12.
  • A severe traumatic brain injury has a Glasgow Coma Scale of 8 or less.

When assessing children with traumatic brain injuries, the Pediatric Glasgow Coma Scale is used. This is a version of the scale for young children who may not have strong language skills yet. The main differences are in the verbal response, with one change in motor response.

Verbal response. The possible scores for verbal response on the pediatric scale are as follows:

  • Patient is unable to respond for an unrelated reason: NT
  • Patient doesn't respond and nothing is interfering with the patient: 1
  • Patient is extremely upset: 2
  • Patient is moaning and is inconsistently very upset: 3
  • Patient cries but can be calmed down; interactions are inappropriate: 4
  • Patient is interactive, smiling: 5

Motor response. All of the possible scores for motor response are the same, except for the option with a score of 6. Instead of the child obeying commands, the Pediatric Glasgow Coma Scale checks to see if the child is moving on their own or moving with purpose.

Several things can affect and interfere with a Glasgow Coma Scale assessment.

Pre-existing factors. These are factors in place before the injury that prevent the patient from responding or following directions. These may include:

  • Hearing loss
  • Intellectual or neurological disability
  • Language barriers
  • Speech impediment

Effects of current treatment. If the patient is currently undergoing other types of medical care, they may not be able to properly respond. This includes:

  • Physical treatment such as intubation
  • Treatment with medication, such as sedation, or paralysis

In a situation where the patient is intubated, they are assessed only on motor response and eye response, and a note is added about the tube. If the patient is being sedated, the medical professional should try to assess the patient before they're sedated.

Effects of other injuries. Other injuries caused during in the same trauma may make it difficult for the patient to respond appropriately. These may include:

  • Fractured skull or eye socket
  • Brain problems due to a lack of blood flow to the brain after cold exposure, known as hypoxic-ischemic encephalopathy
  • Injury to the spinal cord

Other factors such as being drunk or on drugs, shock, low blood pressure, and severe low blood sugar can affect a patient’s level of consciousness and lead to an inaccurate Glasgow Coma Scale score.