Understanding and Interpreting the Glasgow Coma Scale

8 Min Read Published April 26, 2023
Nurse wearing gloves taking notes near patient in bed

What is the Glasgow Coma Scale?

The Glasgow Coma Scale (GCS), designed in 1974, is a tool that has the ability to communicate the level of consciousness of patients with acute or traumatic brain injury. Developed by Graham Teasdale and Bryan J. Jennett, professors of neurosurgery at the University of Glasgow's Institute of Neurological Sciences, this scale is the gold standard used for all acute medical and trauma patients. 

Used by trained medical professionals, the GCS is an objective and reliable tool that nurses and nursing students should become familiar with regardless of their place of employment. Most commonly used in the ICU and ER setting, nurses may need to perform a GCS on a patient at any given time.

The Glasgow Coma Scale can identify changes to consciousness in traumatic brain injury patients but requires nurses to fully understand its purpose and how to use it. Identifying the patients that require scoring is the first step in properly using the scale.

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When to Use the GCS 

The patients who need a GCS assessment have generally suffered a traumatic brain injury and are either in the ER or ICU. An initial GCS should be done at the time of admission and then every four hours unless otherwise indicated by the medical team.

Documentation of the GCS is crucial since the medical team, which generally includes neurology, will use this to determine the improvement or decompensation of the patient. 

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How to Calculate a Patient’s Glasgow Coma Score

The Glasgow Coma Scale analyzes patients on three different criteria:

  • Eye Opening
  • Motor Response
  • Verbal Response

Each criterion is on a different scale, with a total possible score of 15. The lowest possible score is 3. 

Eye Response

  • Closed by local factor - (NT)
  • None - No opening at any time, no interfering factor (+1)
  • To Pressure - After fingertip stimulus (+2)
  • To Sound - After spoken request (+3)
  • Spontaneous - Open before stimulus(+4)

Verbal Response

  • Non-testable - Factor interfering with communication (NT)
  • None - No audible response, no interfering factor (+1)
  • Sounds - Only moan/groans (+2)
  • Words - Intelligible single words (+3)
  • Confused - Not orientated but communicates coherently (+4)
  • Oriented - Correctly gives name, place, and date (+5)

Motor Response

  • Non-testable - Paralysed or other limiting factor (NT)
  • None - No movement in arms/legs, no interfering factor (+1)
  • Extension - Extends arm at elbow (+2)
  • Abnormal flexion - Bends arm at elbow, features clearly predominantly abnormal (+3)
  • Normal Flexion - Bends arm at elbow rapidly but features not predominantly abnormal (+4)
  • Localising - Brings hand above clavicle to stimulus on head/neck (+5)
  • Obeys Commands - 2-part request (+6)

Medical professionals use the aforementioned scale for the best eye-opening response, the best motor response, and the best verbal response. Consideration is made for those with tracheostomy and endotracheal breathing tubes. The column of 1t is added to verbal response at some hospitals to accommodate those patients without altering their GCS score.

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How to Interpret the Glasgow Coma Scale

To calculate a patient’s GCS, first, score the patient on each of the three main areas. Once a number has been determined, add these to create the sum, which is the patient’s Glasgow score. Once a score has been identified, it’s important to understand the meaning.

Every brain injury is different, but generally, brain injury is classified as:

  • Severe: GCS 3-8 
  • Moderate: GCS 9-12
  • Mild: GCS 13-15

Certain scores on the Glasgow Coma Scale have significance. Patients with a Glasgow Coma Scale score of 7 or less are considered comatose. Patients with a Glasgow Coma Scale score of 8 or less are considered to have suffered a severe head injury.

As previously mentioned, accommodations are made for intubated patients but also those with gross facial edema, or swelling. These patients are identified with the numerical value of 1 and an attached modifier.

For example, an intubated patient would have a verbal response of 1t, whereas a patient with pronounced eye swelling would have an eye response of 1c identifying the eyes as closed and unable to open due to the swelling.

Limitations of the GCS

While the Glasgow Coma Scale is a great diagnostic tool there are multiple limitations that can alter the score and not provide an accurate picture of the patient’s brain injury. These include: 

  • Pre-existing facts
  • Language or cultural difference
  • Hearing loss or speech impediment
  • Intellectual or baseline neurological deficit
  • Baseline psychological issues
  • Age (actual and intellectual)
  • Current Treatment
  • Physical 
  • Intubation
  • Edema (swelling)
  • Tracheostomy
  • Pharmacological 
  • Sedation
  • Paralysis
  • Other injuries/wounds/lesions
  • Orbital fracture
  • Cranial fracture
  • Spinal cord damage
  • Dysphasia (language disorder due to damage of the brain)
  • Hemiplegia (paralysis of one side of the body)
  • External Factors
  • Alcohol
  • Drugs

A recent study in the June 2017 edition of Neurosurgery magazine entitled “Factors Influencing the Reliability of the Glasgow Coma Scale: A Systematic Review” studies the overall reliability of the GCS in a variety of clinical settings.

The review identifies multiple limitations, which include the knowledge of the evaluator. The level of education and training of the medical professional can alter the score. 

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Pediatric Glasgow Coma Scale

Another significant limitation of the Glasgow Coma Scale, as it was originally developed, is that it does not accurately measure traumatic brain injury in children under 5 years of age. The aptly named ‘Pediatric Glasgow Coma Scale (PGCS)’ includes modifications for this patient population.

Similar to the adult version, the sum of the eye response, motor response, and verbal response equals the PGCS. The highest score is a 15 (fully awake and aware) and the lowest is 3 (deep coma or brain death). 

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Eye Response

  • Does not open eyes (+1)
  • Opens eyes in response to pressure (+2)
  • Opens eyes in response to speech (+3)
  • Opens eyes spontaneously (+4)

Verbal Response

  • No verbal response (+1)
  • Inconsolable, agitated (+2)
  • Inconsistently inconsolable, moaning (+3)
  • Cries but consolable, inappropriate interactions (+4)
  • Smiles, orients to sounds, follows objects, interacts (+5)

Motor Response

  • No motor response (+1)
  • Extension to pain (decerebrate response) (+2)
  • Abnormal flexion to pain for an infant (decorticate response) (+3)
  • Infant withdraws from pain (+4)
  • Infant withdraws from touch (+5)
  • Infant moves spontaneously or purposefully (+6)

The GCS and PGCS can be confusing at times but understanding the basics is the first step in mastering the scale. Speaking to advance practice nurses and the rest of the medical team to determine the proper GCS for a patient can help drive the patient’s care. 

Glasgow Coma Scale FAQs

  • How do you assess the level of consciousness using the Glasgow Coma Scale?

    • There are three aspects to the GCS that are assessed to determine a patient’s level of consciousness. They are motor responsiveness, verbal performance, and eye-opening.
  • What is a good score on the Glasgow Coma Scale?

    • The highest possible score is 15 (fully conscious) and the lowest possible score is 3 (coma or dead).
  • What are the 5 levels of consciousness?

    • Conscious, Preconscious, Unconscious, Non-conscious, and Subconscious.
  • What does a Glasgow Coma Scale of 8 or less indicate?

    • Patients with a Glasgow Coma Scale score of 8 or less are considered to have suffered a severe head injury. 
  • What does a 6 on the Glasgow Coma Scale mean?

    • Patients with a Glasgow Coma Scale score of 7 or less are considered comatose. 
  • What does a GCS of 15 mean?

    • A GCS of 15 means a patient is fully conscious. 
  • Can you recover from a GCS of 7?

    • Yes, a patient can recover with the proper medical care. 
  • How do you calculate GCS intubated?

    • The maximum GCS score is 10T and the minimum score is 2T for intubated patients. 
  • What are the components of the Glasgow Coma Scale?

    • The three components are motor responsiveness, verbal performance, and eye-opening.

*This website is provided for educational and informational purposes only and does not constitute providing medical advice or professional services. The information provided should not be used for diagnosing or treating a health problem or disease.

Kathleen Gaines
Kathleen Gaines
News and Education Editor

Kathleen Gaines (nee Colduvell) is a nationally published writer turned Pediatric ICU nurse from Philadelphia with over 13 years of ICU experience. She has an extensive ICU background having formerly worked in the CICU and NICU at several major hospitals in the Philadelphia region. After earning her MSN in Education from Loyola University of New Orleans, she currently also teaches for several prominent Universities making sure the next generation is ready for the bedside. As a certified breastfeeding counselor and trauma certified nurse, she is always ready for the next nursing challenge.

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