Does every concussion patient need a CT scan?

No. Most patients with a straightforward concussion and no red-flag findings do not need imaging. CT is reserved for patients who meet high- or medium-risk criteria under a validated decision rule (Canadian CT Head Rule in adults, PECARN in children) or who show one of the red-flag signs listed above.

Can a patient have a concussion with a completely normal CT?

Yes. A normal CT is the expected finding in concussion, since concussion is a functional rather than structural injury. Imaging rules out hemorrhage and fracture; it does not confirm or exclude a concussion diagnosis, which remains clinical.

Is MRI better than CT for diagnosing concussion?

No — neither is a diagnostic tool for concussion in routine practice. CT is preferred acutely because it is fast and sensitive for the structural findings (bleeding, fracture) that actually change acute management. MRI is occasionally used later for atypical or prolonged courses but is typically normal in concussion and is not part of standard workup.

What if red-flag symptoms appear days after the injury, once imaging was already deemed unnecessary?

New or worsening symptoms — especially worsening headache, vomiting, confusion, or any focal neurologic sign — after the initial evaluation warrant urgent reassessment and imaging consideration, even if the original exam was reassuring. This is part of why structured between-visit symptom monitoring matters for concussion patients, not just the index visit.

Are the same red flags used for pediatric and adult patients?

The underlying red-flag signs (vomiting, seizure, focal deficit, declining consciousness, signs of skull fracture) apply across ages, but the formal decision rule differs: PECARN criteria govern pediatric imaging decisions in the emergency department, while the Canadian CT Head Rule applies to adults. See Pediatric versus Adult Concussion Protocols for broader differences in management.

What Concussion Red Flags Warrant Imaging?

Imaging is warranted when a concussion patient shows red-flag signs such as worsening headache, repeated vomiting, seizure, focal neurologic deficit, declining consciousness, unequal pupils, slurred speech, increasing confusion, or signs of skull fracture. In adults, apply the Canadian CT Head Rule; in children, apply PECARN criteria. Concussion itself is a clinical diagnosis — imaging rules out structural injury, it does not confirm concussion.

The Short Answer

Concussion is diagnosed clinically, not radiographically. A normal CT or MRI does not rule out concussion, and imaging is not a routine part of concussion management. Imaging exists for one purpose in this population: to identify structural injury — intracranial hemorrhage, skull fracture, or another emergent finding — that requires a different management pathway than concussion care. The decision to image should be driven by validated clinical decision rules and an explicit red-flag checklist, not by patient or parent request, and not by the mechanism of injury alone.

Red Flags That Warrant Emergent Imaging

Regardless of which decision rule applies, any of the following findings should prompt emergent CT imaging:

Worsening or severe headache, especially a headache the patient describes as the worst of their life
Repeated vomiting (commonly defined as two or more episodes)
Seizure activity following the injury
Any focal neurologic deficit — weakness, numbness, or asymmetric findings on exam
Declining level of consciousness or Glasgow Coma Scale (GCS) score below 15 at two hours post-injury
Unequal or non-reactive pupils
Slurred speech or increasing confusion/agitation
Signs of basilar skull fracture: periorbital ecchymosis ("raccoon eyes"), postauricular ecchymosis (Battle sign), or cerebrospinal fluid leaking from the nose or ear
Suspected open or depressed skull fracture
A dangerous mechanism of injury (e.g., pedestrian struck, ejection from vehicle, fall from height)

These findings are consistent across CDC HEADS UP guidance and the decision rules described below, and any one of them should override a "clinical diagnosis, no imaging needed" default.

Adults: The Canadian CT Head Rule

For adults presenting with GCS 13–15 after head injury, the Canadian CT Head Rule is the most widely used validated decision instrument. It separates findings into two tiers:

High-risk criteria (predict need for neurosurgical intervention):

GCS below 15 at two hours post-injury
Suspected open or depressed skull fracture
Any sign of basilar skull fracture
Two or more episodes of vomiting
Age 65 or older

Medium-risk criteria (predict clinically important brain injury on CT):

Retrograde amnesia of 30 minutes or more before the injury
A dangerous mechanism of injury

Any high- or medium-risk criterion met warrants CT imaging. Additional factors that lower the threshold for imaging even outside the formal rule include anticoagulant or antiplatelet medication use and known coagulopathy — bleeding risk changes the calculus independent of the standard criteria.

Children: PECARN Criteria

The Canadian CT Head Rule was derived and validated in adults and is not the appropriate instrument for pediatric patients. In the emergency department setting, pediatric head injury imaging decisions should follow PECARN (Pediatric Emergency Care Applied Research Network) criteria, which stratify risk separately for children under 2 and children 2 and older, and are designed specifically to reduce unnecessary CT radiation exposure in low-risk children while still identifying clinically important traumatic brain injury. Clinics managing pediatric concussion patients outside the ED should still apply the same underlying principle — the general red-flag list above applies to children as much as adults, with an even lower threshold for concern given the difficulty of a reliable neurologic exam in younger children.

What Imaging Does Not Do

A normal CT is expected in true concussion — concussion is, by definition, a functional injury without a corresponding structural finding on standard imaging. CT is used to rule out a structural bleed or fracture, not to diagnose or grade concussion severity, and a normal scan should not be interpreted as evidence the patient's symptoms aren't real.

MRI is not part of routine acute concussion evaluation. It is occasionally considered later in the course for atypical presentations, a prolonged or worsening trajectory, new focal deficits, or to exclude alternative diagnoses when the clinical picture doesn't fit expected concussion recovery. Advanced imaging techniques such as diffusion tensor imaging (DTI) or functional MRI remain research tools — they are not validated for individual diagnosis or return-to-play clearance decisions and should not be presented to patients as diagnostic.

After Imaging Is Cleared

Once structural injury has been ruled out (or was never a clinical concern), management shifts to the standard graduated framework: relative rest for the first 24–48 hours, symptom-guided return to activity, and structured follow-up. See Post-Concussion Recovery Timeline, Return to Play Decision Criteria, and Return to Learn for what comes after the red-flag screen is complete. Ongoing monitoring for delayed-onset symptoms — headache, dizziness, mood change, sleep disruption — matters even after imaging is negative, since red flags can theoretically emerge or evolve during the recovery window, not just in the first 24 hours.

How Kavera Handles This

Red flags are an in-person decision, and Kavera doesn't change that. What it adds is the weekly check-in between visits: a symptom score that worsens instead of improving is flagged to you the day it comes in, not at the next appointment. Self-Serve practices run this with their own staff. On Managed, Juliet Mott's team runs it and bills it under your credentials.