The Glasgow Coma Scale (GCS) is a clinical tool used to assess a patient's level of consciousness following a head injury. It evaluates three aspects: Eye Opening (1-4 points), Verbal Response (1-5 points), and Motor Response (1-6 points). The total score is the sum of these three components, ranging from 3 (deep coma or death) to 15 (fully awake and oriented). Scores below 8 typically indicate severe brain injury requiring urgent intervention. The range 3-15 is thus the accepted standard for this scale, reflecting the lowest and highest possible scores.

Reference: Adams and Victor’s Principles of Neurology, R. W. Daroff, 10th Edition.