When a "Concussion" Isn't the Whole Story: Understanding Functional Cervical Instability After Head Trauma

By Matthew M. Antonucci, DC, DACNB, FACFN, FABCDD, FABNN, FABVR. FABBIR, FICC

If you've suffered a head injury and still experience headaches, dizziness, nausea, light and sound sensitivity, fatigue, or brain fog, you're not alone.

Many patients visit my office months or even years after being told they have a concussion or post-concussion syndrome — yet despite therapy, rest, and even medication, they still don't feel like themselves.

They start to wonder: "Why haven't I recovered?"

For many, the answer lies in a hidden problem that looks almost identical to concussion but originates just below the skull: functional cervical instability.

The Overlooked Connection Between the Neck and the Brain

A concussion occurs when the brain rapidly accelerates and decelerates inside the skull, stretching delicate neural tissue. But the same forces that injure the brain also travel through the neck — particularly the upper cervical region, where the skull meets the first two vertebrae, C1 (atlas) and C2 (axis).

These vertebrae are stabilized by the alar and transverse ligaments, which help control head and neck movement. Even if they aren't torn, they can become stretched or lax after trauma. The result is functional instability — subtle, excessive movement that disrupts how your brain perceives motion and balance.

This instability can mimic or worsen concussion symptoms, causing headache, dizziness, nausea, fatigue, sensitivity to light or sound, and fogginess.

That's why many patients diagnosed with "persistent concussion" actually have a combination of brain injury and neck instability working together to prolong their suffering.

What Functional Cervical Instability Really Means

"Functional" instability doesn't mean your neck is broken or requires surgery. It means the stabilizing structures aren't performing properly.

Ligaments may allow too much motion, muscles tighten to compensate, and nerves around the upper cervical spine can become irritated — all without visible damage on MRI or CT.

Unlike structural instability (which requires fusion or surgical repair), functional instability happens dynamically. The problem appears only during movement and is therefore often invisible on routine imaging.

Yet for the patient, it can be disabling — fueling pain, dizziness, and fatigue that make even small daily activities exhausting.

(References: Treleaven, Manual Therapy, 2008; Kristjansson & Treleaven, J Rehabil Med, 2009.)

The Clinical Definition: Understanding AOMSI and Its Guaranteed Impairment Rating

The American Medical Association (AMA) formally recognizes this type of instability through their definition of Alteration of Motion Segment Integrity (AOMSI). According to the AMA Guides to the Evaluation of Permanent Impairment, AOMSI represents abnormal motion at a spinal segment that exceeds normal physiological limits.

The AMA defines AOMSI as motion segment instability demonstrated by:

• Abnormal translation (horizontal movement) of vertebrae exceeding normal limits
• Abnormal angular motion between vertebrae beyond physiological ranges
• Loss of motion segment integrity that can be documented through specialized imaging

Importantly, when AOMSI is documented in the cervical spine, the AMA Guides mandate a minimum 25% whole person permanent impairment rating. This isn't discretionary — it's an automatic rating that recognizes the serious nature of ligamentous instability and its impact on function.

This means:

• Your symptoms have a recognized medical and legal basis
• The condition automatically qualifies for disability consideration
• Insurance companies must acknowledge the severity of documented AOMSI
• Your ongoing struggles are validated by established medical standards

The significance of proper AOMSI documentation cannot be overstated. It transforms "invisible" suffering into a quantifiable, recognized medical condition with specific diagnostic criteria and mandatory impairment ratings. This is why obtaining the right imaging — like DMX when indicated — can be so crucial for both treatment and legal/insurance purposes.

(References: American Medical Association. Guides to the Evaluation of Permanent Impairment, 6th Edition. Chicago: AMA Press, 2008; Croft AC. Biomechanics of Whiplash Injury: AOMSI and Permanent Impairment. Spine Research Institute of San Diego, 2016.)

Why Standard Imaging Often Misses It

Traditional imaging captures still pictures of the neck. But cervical instability is a motion problem — and static imaging can't reveal how the vertebrae behave when you move.

That's where Digital Motion X-Ray (DMX) can provide crucial insight.

DMX uses continuous fluoroscopy to record the neck in motion at 30 frames per second, allowing clinicians to see precisely when and where the vertebrae begin to shift abnormally.

In the right clinical context, DMX can reveal ligament laxity, abnormal coupling, or compensatory motion patterns that explain why symptoms persist despite "normal" scans.

While not yet standard in all radiology practices, it can be a valuable piece of the diagnostic puzzle when concussion-like symptoms won't resolve.

(References: Kim JH et al., Spine J., 2018; Harrison DE et al., JMPT, 2004.)

Convenient Access to DMX Imaging

Understanding the importance of motion-based imaging, we've established a partnership with a specialized imaging facility located just a few miles from our practice. When we suspect cervical instability during your evaluation, we can typically arrange same-day DMX imaging with our partner facility.

This immediate access means you don't have to wait weeks for answers or travel long distances to specialized centers. We can often review the motion studies together within days, allowing us to quickly determine whether cervical instability is contributing to your symptoms and coordinate appropriate treatment without delay.

How I Identify Cervical Instability in Post-Concussion Patients

When I evaluate someone with lingering post-concussion symptoms, my first goal is to determine what's driving their dysfunction — the brain, the neck, or both.

A typical assessment may include:

• Orthopedic ligament tests, such as the alar and transverse ligament stress tests, the Sharp-Purser test, and flexion-rotation testing for C1–C2 function.
• Joint position error and proprioceptive testing to measure how accurately the neck communicates with the brain.
• Balance and eye-movement analysis, to assess vestibular-cervical interactions.
• Imaging, including MRI or Digital Motion X-Ray when clinically indicated.

By comparing findings across these systems, I can tell whether symptoms are primarily neurological, mechanical, or both — and develop a plan that targets the true cause.

(References: Aspinall, Manual Therapy, 2010; Hall & Robinson, Phys Ther, 2011.)

Many Patients Have Both: Concussion and Cervical Instability

In my experience, a large percentage of patients actually suffer from both concussion and cervical instability. These conditions are deeply intertwined — the brain and neck work together to control balance, coordination, and sensory integration.

When the brain is injured, it can fail to stabilize the neck effectively. And when the neck is unstable, it continuously sends distorted feedback to the brain, preventing full neurological recovery.

Here's what often happens in my clinic:

1. A patient arrives with persistent headaches, dizziness, and fatigue.
2. Neurological testing confirms a concussion component, and we begin functional neurorehabilitation.
3. As their brain function improves — eye movement, balance, sensory integration — many symptoms dramatically lessen.
4. What remains are subtle neck-driven symptoms that become much clearer and easier to manage.

By restoring proper brain function first, we often relieve the majority of the symptom burden, allowing patients to finally focus on treating the remaining neck instability and crossing that long-awaited finish line of recovery.

My Role: Diagnose Precisely, Treat Concussion, and Coordinate Care

As a clinician specializing in concussion and functional neurology, my responsibility is to accurately identify the source of ongoing post-traumatic symptoms.

If testing shows your symptoms are primarily neurological, we proceed with an individualized concussion rehabilitation program, using advanced sensory, vestibular, and cognitive therapies to restore brain function.

If there is evidence of cervical instability, I collaborate with trusted professionals — including physical therapists, regenerative medicine specialists, and physicians performing stem-cell or prolotherapy procedures — who focus on restoring neck stability.

I don't directly treat cervical instability, but I work closely with those who do. This ensures you get a complete, coordinated plan rather than fragmented or repetitive care.

Functional Instability: Small Problem, Big Impact

Because functional cervical instability doesn't require surgery and often hides on imaging, it's easy to underestimate. Yet this subtle problem can keep the nervous system in a constant state of stress.

It can alter proprioceptive input to the brainstem, affect cranial nerve function, and perpetuate dizziness and fatigue even after the concussion has healed.

Recognizing and addressing it — in tandem with concussion care — is often the missing piece that unlocks lasting recovery.

(References: Kristjansson, J Orthop Sports Phys Ther, 2009; Treleaven, Manual Therapy, 2017.)

A Comprehensive, Functional Approach to Healing

At NeuroSynergy Associates, every post-traumatic patient receives a holistic evaluation that integrates:

• Advanced concussion testing – balance, eye movement, and sensory-cognitive metrics.
• Cervical function analysis – orthopedic and motion assessments to uncover hidden instability.
• Collaborative care – referrals to regenerative and physical medicine specialists when necessary.
• Ongoing communication – ensuring each aspect of your recovery complements the others.

This comprehensive approach doesn't just identify what's wrong — it builds a roadmap to help you regain function, confidence, and quality of life.

Why Accurate Diagnosis Is Everything

Patients with unrecognized neck instability often spend years chasing answers. They're told it's "just a concussion" or that their scans look fine. But when we identify both the concussion and the cervical component, everything changes.

By treating the brain first and clarifying the neck's contribution, we can dramatically reduce suffering, streamline referrals, and give patients renewed hope that recovery is possible.

If You're Still Struggling After a Head Injury

If you've been living with headaches, dizziness, nausea, fatigue, light and sound sensitivity, or mental fog after a head or neck trauma, it's time for a comprehensive evaluation.

You may have a lingering concussion, functional cervical instability, or both. The right assessment can uncover what's really driving your symptoms — and lead you to the right specialists for each piece of your recovery.

At NeuroSynergy Associates, I specialize in identifying and treating concussion, while coordinating care for related cervical issues through a trusted network of regenerative and rehabilitative experts.

Many patients find that once we stabilize and retrain the brain, the majority of their symptoms fade — and they can finally focus on healing the neck and finishing their journey back to health.

You don't have to live in limbo. The right diagnosis changes everything.

Selected References

Treleaven J. Sensorimotor disturbances in neck disorders affecting postural stability, head and eye movement control. Manual Therapy. 2017;28:46–53.

American Medical Association. Guides to the Evaluation of Permanent Impairment, 6th Edition. Chicago: AMA Press, 2008.

Croft AC. Biomechanics of Whiplash Injury: AOMSI and Permanent Impairment. Spine Research Institute of San Diego, 2016.

Treleaven J. Dizziness, unsteadiness, visual disturbances, and sensorimotor control after cervical injury. Manual Therapy. 2008;13(1):2–11.

Kristjansson E, Treleaven J. Sensorimotor function and dizziness in neck pain: implications for assessment and management. J Rehabil Med. 2009;41(9):673–679.

Harrison DE et al. Radiographic analysis of sagittal alignment and kinematics of the cervical spine. J Manipulative Physiol Ther. 2004;27(7):460–470.

Kim JH et al. Dynamic radiographic evaluation of cervical spine instability. Spine J. 2018;18(6):1022–1030.

Hall TM, Robinson K. The flexion–rotation test and C1–C2 dysfunction. Phys Ther. 2011;91(9):1195–1204.

Aspinall W. Clinical tests for upper cervical ligamentous instability. Manual Therapy. 2010;15(5):476–481.

Kristjansson E. Sensorimotor control and cervical joint position sense. J Orthop Sports Phys Ther. 2009;39(10):703–715.