PET Scans: A Deeper Dive into Traumatic Brain Injury
A normal CT or MRI does not rule out a brain injury. Learn what a PET scan shows, why insurers fight it, how Missouri courts decide whether a jury sees it, and what steps protect your health and your claim.
By Joseph Ott
Your CT scan came back normal. Your MRI came back normal. Yet you still lose words mid-sentence, forget appointments, and wake up exhausted. Your family says you're different since the crash. If this sounds familiar, you are not imagining things — and your doctors are not necessarily missing anything. Structural scans and brain injury sometimes measure different worlds.
This guide is for Missourians living with a suspected traumatic brain injury after a car crash, a fall, or a workplace accident. It explains what a PET scan shows that CT and MRI cannot, why insurers resist paying for one, what Missouri law requires before a jury ever sees your scan, and the practical steps that protect both your recovery and your legal claim.
A normal CT or MRI does not clear your brain
CT and MRI are structural cameras. A CT scan looks for bleeding, fractures, and swelling that need emergency surgery. An MRI shows the brain's anatomy in finer detail — torn fibers, small bleeds, lesions. Both answer the same question: what does the brain look like?
Mild traumatic brain injury often leaves that question unanswered. The injury happens at the cellular level, where axons stretch and tear and brain cells struggle to use energy. Nothing about that damage has to show up as a visible lesion. The Centers for Disease Control and Prevention describes a TBI as a bump, blow, or jolt that disrupts how the brain works — a functional problem, not necessarily a structural one. You can have a real injury and a clean scan at the same time.
This gap is why so many survivors hear "good news, your scan is normal" and feel dismissed. It is also why insurers build entire defenses around normal imaging. The scan did its job. It simply wasn't asked the right question.
A PET scan asks a different question: how is your brain working?
PET stands for positron emission tomography. Instead of photographing anatomy, it tracks metabolism. Before the scan, a technician injects a small amount of radioactive tracer — most commonly a tagged form of glucose called FDG. Brain cells that work hard absorb more glucose. Cells that struggle absorb less.
The scanner reads where the tracer collects and builds a map of which brain regions are metabolizing normally and which are running below par. A region that looks intact on MRI can show depressed activity on PET. That difference matters for injuries whose damage is functional — exactly the injuries that standard imaging misses.
Researchers have used PET for decades to study how the brain behaves after trauma. In a TBI workup, the scan can reveal patterns of reduced metabolism that line up with a patient's symptoms — memory networks running cold in someone who can't retain new information, for example. The CDC's TBI symptom guidance lists exactly the problems PET studies track: trouble thinking clearly, memory gaps, headaches, sleep disruption, and mood changes.
PET is a supporting witness, not a star witness
Honesty matters here, because overclaiming hurts real patients. PET is not part of the standard emergency workup for head injury. CT rules out surgical emergencies. MRI hunts structural damage. PET usually enters the picture later, when symptoms persist and the treatment team or the legal team needs functional evidence. Many hospitals don't offer it for TBI at all, and much of the research remains concentrated in academic centers.
A PET scan also does not diagnose by itself. Low metabolism in a brain region can reflect many things — poor sleep, depression, migraine, even how you prepared for the scan. Blood-sugar levels, caffeine, and certain medications can distort FDG uptake. That's why the treating physician, not the patient and not the lawyer, must decide whether the scan makes sense and how to prepare for it. Never stop or change a medication on your own before any test.
The strongest TBI cases treat PET as one layer of corroboration among several. A thorough clinical history, a neurologist's examination, neuropsychological testing, and consistent symptom reporting over time carry the load. Imaging supports that story; it doesn't replace it. Our article on SPECT scans in TBI cases covers another functional-imaging tool with the same supporting role, and diffusion tensor imaging takes yet a different approach.
Missouri decides what a jury gets to see
Admitting scan evidence in a Missouri courtroom is not automatic. Under § 490.065 RSMo, an expert may testify only when specialized knowledge will help the jury, the opinion rests on sufficient facts or data, the methods behind it are reliable, and the expert applied those methods reliably to your case. Missouri tightened this statute in 2017 to track the federal gatekeeping standard from Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).
That gatekeeping shapes the whole strategy around a PET scan. Expect the defense to argue that your expert extrapolated from group research data to you as an individual, or that confounders — medications, blood sugar, timing — make the scan unreliable in your case. A well-prepared expert answers with a differential diagnosis: ruling out the other explanations for the abnormal pattern and tying the imaging to your clinical records and neuropsychological results.
This is why early, consistent medical care matters more than any single test. A scan ordered two years after the crash, with gaps in treatment, invites attack. A scan that fits a documented timeline of symptoms, referrals, and testing is far harder to dismiss.
Insurers have a playbook for normal scans
Once you see the playbook, it loses its power. Defense attorneys and insurance experts typically run three arguments in mild-TBI cases.
First, the nothing-is-wrong argument: your CT and MRI are normal, so your brain is fine, and your symptoms must come from stress or from wanting money. You now know the answer — structural scans don't measure function, and the CDC recognizes that TBI symptoms persist in many patients without positive structural findings.
Second, the junk-science argument: your PET scan is experimental, your expert is an outlier, and the methodology fails the reliability gate. The answer is preparation — a qualified expert, sound methodology, and imaging corroborated by testing, as § 490.065 RSMo demands.
Third, the exaggeration argument: your symptoms are real only when someone watches you. Neuropsychological testing includes built-in validity measures that detect inconsistent effort, and honest patients pass them. Defense teams also misuse the word "malingering" against genuine survivors; our guide to malingering claims in TBI cases explains how that accusation gets answered. And because many survivors never lost consciousness, the myth that you must black out to have a brain injury still circulates — it is simply wrong.
Your recovery can be reduced, but not erased, by shared fault
Missouri follows pure comparative fault. Under § 537.765 RSMo, a jury assigns percentages of fault, and your compensation shrinks by your share — but never disappears because of it. If a jury values your damages at $500,000 and finds you 20 percent responsible for the crash, you recover $400,000. Missouri adopted this system in Gustafson v. Benda, 661 S.W.2d 11 (Mo. banc 1983).
Comparative fault makes objective injury evidence more valuable, not less. When the defense cannot deny the crash happened, it shifts to denying the injury or inflating your share of blame. Documented brain injury — clinical records, testing, and where appropriate functional imaging — anchors the damages side of the case while your lawyers fight the fault percentages.
One deadline overrides everything else. Missouri's general personal-injury statute of limitations, § 516.120 RSMo, gives you five years from the injury to file suit. Five years sounds generous until you account for the months that proper diagnosis, imaging, and expert review consume. Some claims carry shorter windows — claims against government entities, for instance, have notice requirements. Waiting also lets the defense argue that your symptoms appeared too late to connect to the crash.
What to do next
You don't need to become a neuroimaging expert. You need a short list of moves that protect your health and your case:
- See a doctor now if you haven't, and describe every symptom — headaches, memory gaps, sleep problems, mood changes, sensitivity to light or noise. A documented symptom history is the foundation everything else builds on.
- Ask for the right referrals. Persistent symptoms after a normal scan warrant a neurologist, and often a neuropsychologist. Ask directly; primary-care visits run short.
- Never adjust medications on your own before any scan. If a PET scan is on the table, the treating physician and imaging center will give you preparation instructions. Follow those, not internet advice.
- Keep a symptom journal. Two lines a day — what happened, what you couldn't do — creates a timeline no one can fabricate later.
- Preserve the evidence of the crash itself: photos, the police report, witness names, and your discharge papers from the ER.
- Talk to a Missouri injury lawyer before you give a recorded statement to any insurer. Adjusters are trained to lock in "I feel fine" before your symptoms fully declare themselves.
If you're dealing with the aftermath of a head injury, our traumatic brain injury practice handles exactly these cases, and our car accident practice covers the most common cause. You can reach Ott Law Firm through our contact page or at 314-710-2740.
Common questions about PET scans and brain injury claims
My CT and MRI were normal. Can I still have a brain injury?
Yes. CT and MRI show structure; mild TBI often disrupts function without leaving a visible mark. The CDC recognizes persistent TBI symptoms — headaches, memory problems, sleep and mood changes — as real consequences of the injury even when standard imaging looks normal. Persistent symptoms deserve a neurological workup regardless of what the first scans showed.
Will insurance pay for a PET scan?
Often not without a fight. Insurers commonly call PET experimental for TBI and refuse preauthorization. Sometimes the treating physician's documentation of persistent, unexplained symptoms justifies the scan; sometimes it happens later as part of case evaluation. Cost and coverage are real factors, and no one should promise you a scan or a specific result from one.
Can a PET scan prove my case in court?
No single scan proves a case. In Missouri, § 490.065 RSMo requires the expert behind the scan to show reliable methods reliably applied to you. A PET result works as corroboration alongside your clinical history, neurological exams, and neuropsychological testing — and defense counsel will probe every weakness. Courts admit or exclude this evidence case by case.
How long do I have to file a brain injury lawsuit in Missouri?
Missouri's general personal-injury deadline is five years under § 516.120 RSMo, but exceptions shorten some claims, and evidence deteriorates long before any deadline. Symptoms documented early connect far more convincingly to the crash than symptoms first reported years later. Talk to a lawyer early enough that the deadline never drives the strategy.
Should I stop taking my medications before a PET scan?
No. Some medications can affect FDG uptake, but only the treating physician and the imaging team should decide whether to adjust anything. Stopping a medication on your own can endanger your health and can contaminate the scan's value. Raise the question with your doctor and follow the preparation instructions you are given.
This article is for informational purposes only and is not legal or medical advice. Every case is different, and reading this page does not create an attorney-client relationship. If you or a family member is dealing with a brain injury after a Missouri accident, contact Ott Law Firm at 314-710-2740 or through our contact page to discuss your situation.