A traumatic brain injury can cause damage that impairs the patient’s consciousness. The Glasgow Coma Scale measures the degree of the impairment by measuring eye, motor and speech functions. It assigns a numerical value for each function, and the higher the number, the less impairment.
According to StatPearls, the Glasgow Coma Scale has been in use for nearly 50 years for assessing consciousness in patients following a traumatic brain injury. Nevertheless, there are some issues that can interfere with its effectiveness and accuracy.
Pre-existing factors
Sometimes, there is a condition or factor from the patient’s past that prevents an accurate score on the Glasgow Coma Scale. For example, the patient could have hearing loss or a speech impediment that prevents him or her from responding to verbal instructions. Another possibility is that the patient does not speak or understand the language that the person administering the test is speaking.
Effects of other injuries
Where there is a traumatic head injury, there is also an increased likelihood of spinal cord injury. A spinal cord injury does not itself affect consciousness, but it can affect a patient’s ability to respond to instructions from the person administering the test.
Effects of treatment
If the patient is in the hospital following a traumatic brain injury, factors related to treatment could affect his or her score on the Glasgow Coma Scale. For instance, sedated patients are likely to score low, meaning that providers should wait until after the assessment to sedate the patient. A patient requiring intubation is unable to speak. The person administering the test indicates this by adding “T” as a suffix for the verbal score.
Another limitation of the Glasgow Coma Scale is that it is not appropriate for preverbal children. There is a second Pediatric Glasgow Coma Scale for use with these young patients.