A concussion is defined as a mild traumatic brain injury (TBI) that results from a bump, blow, or jolt to the head or body, causing temporary changes in brain function. The question of whether concussions have different “levels” is common, and the answer has changed over time. While traditional, numerical grades like “Grade 1” or “Grade 3” used to be standard practice, major medical organizations no longer use these fixed systems. The current approach assesses the injury by dynamically evaluating its functional impact on the individual, providing a more accurate picture of the injury and the recovery process.
The Historical Practice of Concussion Grading
For many years, medical professionals used numerical grading systems to categorize concussions, determining injury severity and guiding return-to-play decisions. These systems emerged from the 1980s through the early 2000s, attempting to standardize an injury that often presents ambiguously. The most widely used examples were the Cantu grading system and the guidelines published by the American Academy of Neurology (AAN) in 1997.
These classifications relied heavily on two immediate markers: loss of consciousness (LOC) and the duration of post-traumatic amnesia (PTA). For instance, under the Cantu guidelines, a Grade 1 concussion involved no LOC and post-traumatic amnesia lasting less than 30 minutes. A Grade 2 injury included LOC lasting less than five minutes or amnesia lasting between 30 minutes and 24 hours, while a Grade 3 was assigned for LOC over five minutes or amnesia lasting longer than 24 hours.
The AAN’s 1997 system similarly used confusion and LOC to assign a grade, with Grade 1 representing transient confusion and no LOC, and Grade 3 representing any LOC. These grading scales were designed to predict recovery time and the earliest safe return to activity. However, they were developed largely through expert opinion and lacked comprehensive scientific validation to support their prognostic power.
Why Medical Professionals Moved Away from Grading
The abandonment of fixed numerical grading systems was driven by scientific evidence showing these classifications did not reliably predict patient outcomes. Research demonstrated that a seemingly “mild” Grade 1 concussion could result in a significantly longer recovery period than a “severe” Grade 3 injury. Recovery time proved to be inconsistent with the assigned initial grade.
A concussion is fundamentally a functional injury—a temporary disturbance in brain chemistry and energy—not a structural one categorized by the severity of the initial impact. Cutoffs based on the presence or absence of brief LOC failed to account for the individualized nature of concussion recovery. The Concussion in Sport Group (CISG) and other major bodies recommended abandoning these scales because they provided a false sense of certainty regarding prognosis.
The traditional systems also failed to account for the variability of symptoms across individuals, making them poor tools for guiding patient management. Less than 10% of concussions actually involve loss of consciousness, yet this factor was heavily weighted in the old grading scales. The overall severity of a concussion is not determined at the moment of impact but evolves over the days and weeks following the injury.
Current Assessment: Evaluating Severity Through Symptoms and Duration
Today, concussion severity is assessed dynamically based on the type, number, and duration of symptoms, rather than a fixed initial grade. This modern approach focuses on how the functional injury manifests in the patient over time. Severity is now understood as a measure of impairment and recovery trajectory.
A comprehensive functional assessment begins with detailed symptom tracking, often utilizing standardized tools like the Sport Concussion Assessment Tool (SCAT). The SCAT includes an evaluation of 22 different symptoms across physical, cognitive, emotional, and sleep categories, with each symptom graded on a severity scale from zero to six. This systematic evaluation provides an objective measure of the patient’s impairment at a given time and helps monitor changes as they recover.
Red Flags
A second component of the modern assessment involves identifying “Red Flags,” which are severe, immediate symptoms suggesting a potential structural injury, such as a brain bleed, requiring urgent care. Examples of red flags include:
- A seizure
- Neck pain
- Worsening headache
- Double vision
- A rapidly deteriorating level of consciousness
The presence of any red flag immediately necessitates activating emergency procedures and transporting the patient for advanced medical imaging and evaluation.
Duration of Impairment
The third and most telling component of severity is the duration of impairment. While most concussions resolve within a few days to four weeks, protracted symptoms lead to a diagnosis of Post-Concussion Syndrome (PCS) if they persist for more than three months. This prolonged recovery is a key indicator of severity in the modern clinical framework. The number and type of symptoms, especially cognitive issues like memory problems or slower mental processing speed, are more predictive of a longer recovery than the initial presence of LOC.