My brain scan was normal. Why am I still forgetting things?
What CT, MRI, blood tests and thinking tests can and cannot show after a concussion
After the crash, you had a CT scan. The doctor came back with good news: no bleeding, no fracture. You went home relieved. Weeks later, you still lose your train of thought, forget appointments and struggle to follow a TV show.
It is natural to wonder what that means. Some people start to doubt themselves. Some worry that others, including employers or insurers, will doubt them too.
A normal scan and real memory trouble can both be true at the same time. Each test answers a different question. None of them answers every question.
What a CT scan is built to find
A CT scan uses X-rays to make quick pictures of the brain and skull. When doctors suspect an injury inside the skull, a radiology expert panel from the American College of Radiology calls CT the first imaging test to use [1]. Doctors use it to look for problems that may need urgent treatment.
In research studies, a CT counts as positive when it shows a skull fracture or an acute injury inside the skull, such as bleeding or a bruise on the brain [2]. Not everyone with a head injury needs a CT. The radiology panel notes that practice guidelines call for using CT selectively, often guided by checklists called clinical decision rules [1].
What a normal CT tells you
A normal CT is reassuring about emergencies. It does not tell you whether you had a concussion or how your memory will do. Diagnostic criteria for mild TBI released in 2023 by the American Congress of Rehabilitation Medicine make this point [3]. Their expert panel agreed that a person can be diagnosed with concussion, another name for mild TBI, when scans come back clear or were never needed [3].
So a concussion diagnosis rests mainly on what happened and how you were affected. A University of British Columbia release about the new criteria noted that concussions usually do not show up on brain scans [4].
Why a normal scan and real symptoms can both be true
Large studies show that a normal CT does not guarantee a smooth recovery. Researchers in TRACK TBI, a U.S. study run at 11 level I trauma centers, enrolled 1,154 adults with mild TBI [5]. A year after injury, 61% of those with an abnormal CT reported some limit in daily life. So did 49% of those whose CT was normal [5].
The researchers also compared the CT negative group with people who had orthopedic injuries but no head injury. The mild TBI patients with normal scans were more likely to report daily life limits at one year [5]. These numbers describe broad everyday function, so they include more than memory. They also come from trauma center patients, who may have had more serious injuries than people treated elsewhere.
What a scan cannot see
Some injury is too small for CT to detect. In an earlier TRACK TBI study, 135 adults with mild TBI had both CT and an early MRI, about 12 days after injury [2]. Among the 98 whose CT was normal, 27% had changes on MRI [2]. Most were tiny spots of bleeding along nerve fibers, a finding called hemorrhagic axonal injury [2].
Even MRI has limits. Memory also depends on attention, sleep, pain, mood and fatigue, which no scan measures. Canada’s adult Living Concussion Guidelines, updated in 2023, list several conditions tied to worse or longer lasting thinking symptoms [6]. Among them are anxiety, low mood, PTSD, sleep problems, fatigue and pain.
How your care team should respond
The VA/DoD’s 2021 mild TBI guideline suggests that clinicians take a symptom focused approach and acknowledge symptoms instead of labeling them as psychological [7]. In practice, your description of daily problems should guide the next steps.
Where MRI fits
MRI uses a strong magnet instead of X-rays. The American College of Radiology panel says MRI is useful when problems with brain function last and a CT does not explain them, especially weeks to months after the injury [1].
In the 2013 TRACK TBI MRI study, certain MRI findings were linked to poorer recovery at three months [2]. Bruises on the brain and four or more spots of axonal injury each raised the odds of a worse outcome [2]. Adding MRI findings helped predict who would struggle, beyond basic facts about the person and the injury [2].
Why MRI is not ordered for everyone
The same authors cautioned that routine MRI for all patients with mild TBI may not be cost effective [2]. They also noted that many people with abnormal MRI scans still recovered well [2]. So an MRI finding is one clue among many. Whether you need an MRI depends on your symptoms and history. It is fair to ask what question the scan would answer before you have it.
A 2025 U.S. guideline for adults in the first six months after a brain injury agrees. It tells clinicians not to order a brain CT or MRI for every patient [8]. When someone asks for a test that is not needed, the guideline says the clinician should explain why the result would be unlikely to change the care plan [8].
Blood tests for brain injury
Blood tests for brain injury are newer. They measure blood levels of two proteins found mainly in the brain, called GFAP and UCHL1 [9, 10]. In January 2021, the FDA cleared a handheld version of this test, run on a device called the i-STAT Alinity [9].
In 2024, the FDA cleared a whole blood version, the i-STAT TBI cartridge, that can give results in about 15 minutes [11]. It is cleared for adults 18 and older with a suspected mild TBI, within 24 hours of the injury [11]. It is meant to be used along with other clinical information, including to help rule out the need for a head CT [11].
What the blood test does not do
At the time of the 2024 clearance, the test was not cleared to rule in a concussion [10]. A normal result can help a doctor decide a CT is not needed. But an abnormal result is not a diagnosis by itself [10]. The test is also not designed to track memory weeks later, since it is cleared for use within 24 hours of the injury [11].
The 2023 ACRM criteria take blood tests into account as one piece of evidence, along with tests of thinking, balance and vision [4]. Blood tests are one part of the picture, alongside your symptoms and exam.
Advanced scans: research tools for now
You may hear about special brain scans for concussion. One example is diffusion tensor imaging (DTI), an MRI method researchers use to study white matter, the bundles of nerve fibers that link brain regions [12].
In its 2016 criteria, the American College of Radiology panel described advanced neuroimaging as an area of active research that was not part of routine clinical practice [13]. Results that look meaningful across a research group may not apply to a single patient.
A 2014 TRACK TBI study shows why caution makes sense [12]. Researchers used DTI in 76 adults with mild TBI and 50 healthy volunteers. They found white matter changes at the group level in patients whose CT or MRI already showed injury. In patients with normal CT and MRI, they found no group level evidence of white matter injury [12]. The authors called their study exploratory and said it needed confirmation in a larger group [12].
If a clinic offers an advanced scan to prove or rule out a concussion, ask your care team whether it would change your treatment, and what the cost would be.
Comparison compiled by Safety Behind the Wheel Foundation
What each test can and cannot tell you
| Test | What it can show | What it cannot show |
|---|---|---|
| Head CT | Skull fractures and bleeding that need urgent care | Most concussions; how memory is working |
| Brain MRI | Small bleeds and bruises CT can miss | Whether symptoms will last; how memory is working |
| GFAP and UCHL1 blood test | Whether a head CT is likely needed, within 24 hours | Whether you have a concussion |
| Advanced MRI such as DTI | Research findings about nerve fiber pathways | A reliable diagnosis for one person |
| Thinking tests | How memory, attention and speed are working now | The cause of a problem on their own |
Sources: ACR Appropriateness Criteria [1, 13]; Yuh 2013 and 2014 [2, 12]; FDA clearance reports [11, 10]; Living Concussion Guidelines [6].
What thinking tests can and cannot tell you
If memory is your main concern, tests of thinking often answer more than scans can. In a neuropsychological assessment, a trained specialist gives and scores a series of detailed tasks covering memory, attention, processing speed and problem solving. A CDC concussion form notes that this kind of testing can give useful information about how the brain is working [14].
When testing makes sense
Timing matters. The VA/DoD guideline steers clinicians away from a full battery of cognitive tests during the first month after a mild TBI [7]. It also suggests against using computer based concussion screening batteries for routine diagnosis and care [7].
According to the Living Concussion Guidelines, a referral for this kind of assessment may be considered once several conditions line up [6]. Your thinking problems get in the way of daily life. Sleep, pain, mood and similar issues are under good control. Progress has stalled. And the symptoms have gone on for longer than four weeks. Concussion trained occupational therapists or speech language pathologists can be another route when waits for testing are long [6].
What testing cannot do
Tests are a snapshot of one day. A 2023 TRACK TBI analysis pointed out that formal cognitive tests can miss the thinking complaints people describe after a mild TBI [15]. A normal test result does not erase the trouble you have at work or at home. Guidelines suggest managing fatigue, pain, poor sleep and mood before formal testing, since those conditions are tied to worse thinking symptoms [6].
The INCOG 2.0 international guidelines, updated in 2023 and written mainly for moderate to severe TBI, added recommendations on giving cognitive assessments by video [16]. Ask whether that is an option if travel is hard.
Results can also guide practical steps. If thinking symptoms continue past the first planned period of changes at work or school, the Living Concussion Guidelines advise reviewing and extending those changes [6]. A written report can help you explain what support you need.
Checklist from Safety Behind the Wheel Foundation
- Bring the names of all your medicines and supplements
- Bring notes on when memory slips happen and what they look like
- Wear your glasses or hearing aids if you use them
- Try to get a normal night of sleep beforehand
- Mention pain, low mood or worry, even if no one asks
- Ask how the results will be shared and what happens next
Getting help when tests look normal
A normal scan or test does not mean you are on your own. Guidelines lay out several next steps.
Start with your primary care clinician, who can look at the full picture [7]. Sleep problems, pain, headaches and low mood are tied to worse thinking symptoms, so treating them is often an early step [6]. If memory, attention or planning problems continue after those are managed, the VA/DoD guideline supports a short trial of cognitive rehabilitation with a clinician [7].
For symptoms that start more than a month after the injury, the VA/DoD guideline suggests checking other possible causes too [7]. Memory trouble that keeps getting worse deserves a fresh medical look.
If you drive for work or daily life, talk with your care team about whether your memory and attention are ready for it. A normal scan does not answer that question.
Get emergency care right away
Some concussion symptoms do not appear until hours or days after the injury, so an early normal scan is not the final word [17]. Based on the CDC list of danger signs, call 911 or get to the nearest emergency room if you:
- Have a headache that worsens and does not go away
- Feel weak or numb, lose coordination, or have convulsions or seizures
- Vomit over and over
- Have slurred speech or behave in unusual ways
- Notice one pupil looking bigger than the other (the pupil is the black circle in the middle of the eye)
- Stop recognizing people or places, or grow confused, restless or agitated
- Lose consciousness, seem very drowsy or cannot be woken
Questions to ask your care team
Question checklist from Safety Behind the Wheel Foundation
- What was my CT scan looking for, and what did it rule out?
- Do my symptoms fit a concussion even though my scan was normal?
- Would an MRI change my treatment, and what question would it answer?
- Was a blood test for brain injury used in my emergency care, and what did it show?
- Is it the right time for a thinking assessment, or should we treat sleep, pain or mood first?
- Who can do the assessment, and is there a video option?
- If my tests are normal but I still struggle, what treatment or therapy can I try?
- Which new symptoms should send me back to the emergency room?
Frequently asked questions
Should I ask for an MRI if my CT was normal?
It depends on your situation. MRI can help weeks to months later when problems last and a CT does not explain them [1]. Still, research has found that routine MRI for every mild TBI may not be cost effective [2]. Ask your care team what an MRI would add in your case.
Can a blood test tell me if I had a concussion?
Not on its own. The FDA cleared blood tests for GFAP and UCHL1 to help decide whether adults need a head CT within 24 hours of an injury [11]. As of the 2024 clearance, they were not cleared to rule in a concussion [10].
If my thinking tests came back normal, am I fine?
Not necessarily. Thinking complaints after mild TBI do not always show up on tests [15]. Share specific examples from daily life with your care team, and ask about treatment for sleep, pain, mood and memory strategies.
Are advanced brain scans worth paying for?
Usually not. The radiology panel’s 2016 criteria described advanced neuroimaging as a research area, not routine care [13], and a TRACK TBI study of one such method called itself exploratory [12]. Ask whether any scan would change your treatment before paying for it.
The bottom line
Recommendation from Safety Behind the Wheel Foundation
A normal brain scan after a crash is good news about emergencies. It does not prove that you did not have a concussion. It does not explain away memory problems. Concussions usually do not show on standard scans. People with normal CTs can still struggle for months.
The most useful next steps are often a careful talk with your care team, treatment for sleep, pain and mood, and a thinking assessment at the right time. Ask what question each test would answer before you have it.
Sources and further reading
- 1Shih RY, Burns J, Ajam AA, et al. (Expert Panel on Neurological Imaging). ACR Appropriateness Criteria head trauma: 2021 update. Journal of the American College of Radiology. 2021;18(5S):S13-S36. doi.org/10.1016/j.jacr.2021.01.006
- 2Yuh EL, Mukherjee P, Lingsma HF, et al. Magnetic resonance imaging improves 3-month outcome prediction in mild traumatic brain injury. Annals of Neurology. 2013;73(2):224-235. doi.org/10.1002/ana.23783
- 3Silverberg ND, Iverson GL, et al. The American Congress of Rehabilitation Medicine diagnostic criteria for mild traumatic brain injury. Archives of Physical Medicine and Rehabilitation. 2023. doi.org/10.1016/j.apmr.2023.03.036
- 4University of British Columbia. International group of experts redefines concussions. News release via EurekAlert. May 23, 2023. eurekalert.org/news-releases/989899
- 5Nelson LD, Temkin NR, Dikmen S, et al. Recovery after mild traumatic brain injury in patients presenting to US level I trauma centers: a TRACK-TBI study. JAMA Neurology. 2019;76(9):1049-1059. doi.org/10.1001/jamaneurol.2019.1313
- 6Living Concussion Guidelines (Ottawa Hospital Research Institute). Cognitive difficulties, guideline section 9 (adult concussion). Last updated May 2023. concussionsontario.org/…/cognitive-difficulties
- 7U.S. Department of Veterans Affairs, U.S. Department of Defense. VA/DoD clinical practice guideline for the management and rehabilitation of post-acute mild traumatic brain injury, version 3.0. 2021. Summary at ASHA Evidence Maps. apps.asha.org/…/f28e156a-8117-ee11-8145-005…
- 8Silverberg ND, Lee K, Mikolić A, et al. Action Collaborative on Traumatic Brain Injury Care: adapted clinical practice guideline. Annals of Family Medicine. 2025;23(6):552-569. doi.org/10.1370/afm.250352
- 9Practical Neurology. FDA gives clearance for the first 15-minute handheld blood test for concussions. January 13, 2021. practicalneurology.com/…/2469475
- 10360Dx. With new FDA clearance for POC test, Abbott further expands TBI portfolio. Undated news report on the 2024 whole blood clearance. 360dx.com/node/91706
- 11Practical Neurology. Abbott’s portable whole blood test for TBI cleared by FDA. April 10, 2024. practicalneurology.com/…/abbotts-portable-whole-bloo…
- 12Yuh EL, Cooper SR, Mukherjee P, et al. Diffusion tensor imaging for outcome prediction in mild traumatic brain injury: a TRACK-TBI study. Journal of Neurotrauma. 2014;31(17):1457-1477. doi.org/10.1089/neu.2013.3171
- 13Shetty VS, Reis MN, Aulino JM, et al. ACR Appropriateness Criteria head trauma (2016 version). Journal of the American College of Radiology. 2016;13(6):668-679. doi.org/10.1016/j.jacr.2016.02.023
- 14Gioia G, Collins M. Acute Concussion Evaluation (ACE), physician/clinician office version, v2. CDC HEADS UP. 2006. cdc.gov/…/ace_v2-a.pdf
- 15Eagle SR, Jain S, Sun X, et al. Network analysis and relationship of symptom factors to functional outcomes and quality of life following mild traumatic brain injury: a TRACK-TBI study. Frontiers in Neurology. 2023;14:1308540. doi.org/10.3389/fneur.2023.1308540
- 16Bayley MT, Janzen S, Harnett A, et al. INCOG 2.0 guidelines for cognitive rehabilitation following traumatic brain injury: methods, overview, and principles. Journal of Head Trauma Rehabilitation. 2023;38(1):7-23. doi.org/10.1097/HTR.0000000000000838
- 17Centers for Disease Control and Prevention. Symptoms of mild TBI and concussion. Updated September 15, 2025. cdc.gov/…/index.html
This article reflects the safety priorities of brain injury recovery and safe driving education. It explains brain scans and thinking tests in general terms and is not medical advice. Testing rules and device clearances change, so check official sources and talk with your own care team. Reviewed October 2026.
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