Glasgow Coma Scale: Purpose and Proper Use in Clinical Assessment
The Glasgow Coma Scale (GCS) is a standardized clinical tool designed to provide reliable interobserver neurological evaluations of patients with head injury and to facilitate clear communication between healthcare providers about patient status. 1
Components and Scoring
- The GCS consists of three components that assess different aspects of neurological function: Eye Response (E) scored 1-4, Motor Response (M) scored 1-6, and Verbal Response (V) scored 1-5, with total scores ranging from 3 to 15. 1
- GCS scores are categorized as: Mild (13-15), Moderate (9-12), and Severe (≤8), with a score of 8 or less typically indicating the need for airway protection and possible neurosurgical intervention. 2
- The individual components of the GCS often provide more prognostic information than the sum score alone, with the motor component having the highest predictive value in severe TBI. 1
Primary Purpose and Clinical Applications
- The GCS was originally developed in 1974 by Teasdale and Jennett as a standardized tool to facilitate reliable interobserver neurological assessments of comatose patients with head injury and to enable clear communication between healthcare providers on rotating shifts. 3, 1
- The scale was designed to be easy to use in clinical practice by relatively inexperienced care providers, particularly before CT scanning was widely available. 3
- The GCS helps determine appropriate level of care, need for neurosurgical intervention, and enables detection of neurological deterioration requiring intervention. 1
- The scale correlates with mortality and functional outcomes, especially when assessed serially, and serves as a required component in TBI research and classification systems. 1, 4
Importance of Serial Assessments
- Serial GCS determinations are significantly more valuable than single measurements for detecting deterioration in patients with head injuries. 3, 1, 2
- A low GCS score that remains low or a high GCS score that decreases predicts a poorer outcome than a high GCS score that remains high or a low GCS score that progressively improves. 3
- When head CT is not available, serial GCS scores are the best method for detecting patients who require neurosurgical intervention. 3
Important Limitations and Caveats
- The GCS was not designed for mild TBI assessment, and a single GCS determination is insufficient to diagnose mild TBI or determine parenchymal injury extent. 3, 1
- In one of the original multicenter studies validating the scale in the pre-CT era, approximately 13% of patients who became comatose had an initial GCS of 15. 3
- Common confounding factors that can affect GCS assessment include sedation, intubation, facial trauma, and intoxication. 1, 2
- Patients with identical sum scores but different component profiles may have different outcomes, highlighting the importance of documenting individual component scores. 1
Best Practices for Implementation
- Always perform serial assessments to monitor trends rather than relying on single measurements. 1, 2
- Document individual component scores (E, M, V) separately before calculating the total score to avoid common pitfalls in assessment. 1, 2
- Use the GCS alongside other assessments like pupillary response for comprehensive evaluation. 1
- Recognize the limitations of the GCS and consider alternative assessment tools when necessary, such as the Full Outline of UnResponsiveness (FOUR) Score, which incorporates brainstem reflexes and can be used in intubated patients. 1, 5
Global Impact and Adoption
- The GCS is officially employed in more than 75 countries and is a required component of the National Institute of Health Common Data Elements for studies of head injury. 3
- Despite its limitations and the development of competing scales, the GCS remains the most universally utilized level of consciousness scale worldwide due to its simplicity and practical usefulness. 6, 7