A standard brain MRI is an excellent test. It images brain tissue and answers a specific question: is there a bleed, a lesion, a tumor, visible structural damage.
In mild traumatic brain injury, the answer is usually no. Visible damage to brain tissue is rare in these cases, which is part of what makes the category difficult — the symptoms can be significant while nothing observable accounts for them.
The report says normal. It isn't wrong. It's answering a question that may not be the one that needed asking.
Research imaging has picked up group-level differences after mild traumatic brain injury — a meta-analysis of neuroimaging studies found consistent frontal vulnerability and an anterior-to-posterior gradient in white matter changes — but the authors of that work are explicit that considerably more is required before those techniques can diagnose an individual patient (Eierud et al., 2014). That gap between research findings and clinical usefulness is much of why people end up being told nothing is wrong.
Can the Same Image Support Two Different Readings?
I've been in the position of standing a few feet from a radiology report stating that the brain is fine, looking at those same images, and identifying several findings that explain a patient's symptoms.
The report isn't mistaken. The findings I'm looking at aren't in the brain, and the report was assessing the brain.
That difference is about which question the images are being asked. A brain-focused reading asks whether the tissue is damaged. What I'm asking is different: what conditions is this brain operating under? Is fluid draining? Is blood arriving? Is the structure beneath the skull sitting where it belongs?
Same pictures, different question, different answer.
Where Does the Scan Actually Stop?
The craniocervical junction — where your skull meets the first two vertebrae of your neck — is roughly two inches below where a standard brain MRI stops framing.
That's a small distance holding a great deal. The lower brainstem passes through it. The vertebral arteries thread through the bones there [on their way to supply the back of your brain](post-why-coordination-fails-while-a-brain-scan-looks-normal.html). The jugular vein, the main drainage route for fluid leaving your head, passes directly in front of the first vertebra. And the entire assembly is held in position by a set of ligaments with a strikingly low tolerance for force.
If the structures producing someone's symptoms sit in that region, a perfect brain MRI will miss them every time. Not because the imaging failed, but because the imaging was framed for a different target.
The fix is not exotic. Extend a thin-slice, brain-quality MRI down through the craniocervical junction instead of stopping at the brain.
Why Can Lying Down Hide the Finding?
A few specifics matter beyond just extending the field of view, and this is the one most likely to change a result.
Most MRI is performed lying down. That position unloads the structures you're trying to evaluate.
When you lie flat, gravity stops pulling downward through the spine. The brain and its membranes rise slightly. Pathways that are compressed when you're upright open back up. A structure that descends far enough to cause a problem in daily life may sit in an unremarkable position on the table.
**Upright imaging loads the structures the way life loads them.** Gravity pulls everything down to where it actually sits when you're standing, which is when your symptoms occur. Findings that recede when recumbent — a cerebellar tonsil sitting lower than it should, a Chiari-type malformation, maximum restriction of fluid pathways — become visible.
This is why a person can be told their imaging is normal and still be describing something real. The imaging was accurate about the position they were in, and that wasn't the position in which the problem occurs.
Can You Actually Watch the Fluid Move?
Cine MRI is the study I find most compelling, because it shows something a still image cannot.
It captures cerebrospinal fluid in motion, in its pulsing rhythm. You watch the fluid travel, and you see where it moves freely and where it stalls. Newer implementations add velocity readings, which allows turbulence to be identified rather than inferred.
There is a reason to think head position belongs in that assessment. In healthy adults, phase-contrast MRI has shown that head rotation measurably alters cerebrospinal fluid flow rate and stroke volume at the craniocervical junction (Xu et al., 2016). Fluid movement at that junction is not independent of how the structures above and below it are positioned.
If you know what an open flow pattern is supposed to look like, and you observe a region where flow is disrupted and doesn't continue past a certain point, you are effectively watching the mechanism of a person's decline in real time.
That's a different category of evidence than a static picture of normal tissue.
What Measures Position Rather Than Damage?
There's one more type worth naming, and it answers a question no MRI is designed for.
Cone beam CT measures the craniocervical junction — the shape of the bones and their exact positions relative to one another. This isn't a search for fractures. It's measurement: how far off is the alignment, in which direction, at what angle.
That matters because it converts a general impression into specific numbers. Knowing that a structure has moved in a definite, measurable direction is what allows a correction to be calculated rather than estimated. In our field, cone beam CT is moving toward becoming the standard for exactly that reason.
Standard craniocervical X-rays taken in three dimensions serve a similar purpose and remain widely used.
Which Tests Require No Equipment at All?
You don't need a scanner to start asking better questions, and these are worth knowing because any clinician can perform them.
The principle behind all three is the same: **change one variable — the position of the head — and observe what happens.** If output changes when head position changes, the neck is contributing to that output.
**The Fukuda stepping test.** Eyes closed, march in place for thirty seconds. With vision removed and the head relatively still, the dominant remaining input is proprioception. Drifting significantly off center suggests the position signal is unreliable.
**The supine leg length check.** With the head supported on something soft, note whether one leg appears shorter. Then have the person turn their head and look again. If the difference changes with head rotation, the asymmetry is being driven by the upper neck, because head rotation is the variable that changed.
**The cervicogenic shoulder strength test.** With the person on their back and one arm extended upward, press down with steady, equal pressure and compare sides. Take the weaker arm, have them turn their head one way, and retest. Then the other way. If strength shifts with head position, the output is being influenced from the neck — and the main thing rotating when you turn your head is the joint between the first and second vertebrae.
None of these is proof on its own. A single positive finding means very little, and I'd treat any one of them as a reason to look further rather than as a diagnosis.
Why Does Correlation Make a Finding Meaningful?
That last point deserves its own emphasis.
Think of these findings as stars. One star tells you almost nothing. But when several appear together — a positive stepping test, a leg length change with head rotation, a strength shift with head position, plus [headaches](condition-headaches.html), dizziness, brain fog, and [pressure in the head](condition-pressure-in-the-head.html) — you step back and recognize a shape.
At that point you are no longer guessing, because very few locations in the body can produce that entire combination at once. The craniocervical junction is one of them.
Better imaging and better bedside testing don't replace the standard brain workup. They stop us from concluding that nothing is wrong when the accurate statement is that we didn't look two inches lower.
Told Your Scan Was Normal While You Knew Something Wasn't?
A clear brain MRI doesn't mean nothing is wrong. It often means the imaging stopped just above the problem, or wasn't built to show the [craniocervical junction](condition-concussion-and-mtbi.html) in the first place.
Looking two inches lower, with the right tests and the right imaging, is the work we do at Cerebral. If you'd like a real evaluation, we're here.
References
- Eierud C, Craddock RC, Fletcher S, et al. Neuroimaging after mild traumatic brain injury: review and meta-analysis. *NeuroImage: Clinical*. 2014;4:283–294. https://pubmed.ncbi.nlm.nih.gov/25061565/
- Xu Q, Yu SB, Zheng N, et al. Head movement, an important contributor to human cerebrospinal fluid circulation. *Scientific Reports*. 2016;6:31787. https://www.nature.com/articles/srep31787