Brain Changes with Functional Neurological Disorder (FND)

Functional Neurological Disorder (FND) is a condition that can feel confusing and frustrating for patients. Symptoms are real and disabling—such as tremors, weakness, non-epileptic seizures, or difficulty walking—but standard medical scans often return “normal.” "Normal" tests can feel invalidating when you feel anything but "normal". However, modern neuroscience shows that FND is very real and arises from changes in how the brain functions and communicates, not from damage to brain structure.

What is FND?

Have you ever had your computer glitch? You turn it off and on and that resets it to proper function. That's a software glitch. This is similar to FND. The brain is dysfunctional in its firing patterns and this is what gives the symptoms.

Unlike strokes, degenerative diseases and tumours, there's no damage to the brain and nervous system. To use the computer analogy again, the hardware (eg: motherboard, keyboard and screen) are intact and not broken.

FND has a wide variety of symptoms that can occur. This might include:

History of FND

Historically, what we now call FND was first described in ancient medical writings as “hysteria.” The concept evolved over centuries, with French neurologist Jean-Martin Charcot in the late 1800s formalising many of the diagnostic features. Sigmund Freud later proposed psychoanalytic explanations in the early 1900s.

The modern, brain network–based understanding of FND began to take shape in the late 20th and early 21st centuries as neuroimaging advanced. Today, FND is increasingly recognised and more commonly diagnosed in neurology clinics.

It is important to note that while terms like “hysteria” and Freud’s psychoanalytic theories are part of the historical record, they do not reflect the modern scientific understanding of FND. This past history unfortunately still colours some public and professional perceptions, leading to the mistaken belief that symptoms are ‘all in the head’ in the sense of being imagined or faked. In reality, symptoms are very much ‘in the head’ because they arise from brain network dysfunction, but they are genuine, involuntary, and disabling. Recognising this distinction is vital to reduce stigma and ensure people receive appropriate and compassionate care.

Functional Brain Network Changes in FND

Limbic vs Frontal Pathways

The limbic system (emotional centres like the amygdala) and the frontal cortex (the “executive brain”) work in constant balance. In FND:

• The limbic system is often overactive, amplifying sensations and stress responses.

• The frontal cortex underperforms, reducing inhibitory control over these signals.

• The result is a imbalance between emotional drive and rational regulation, producing symptoms.

When the limbic system becomes too dominant, it can effectively “hijack” the body’s sensorimotor system. This means that emotional and stress-driven brain circuits override the normal motor control pathways. Instead of the frontal lobe guiding precise, voluntary movements and the sense of touch, the limbic system floods the system with threat or stress signals, disrupting smooth control of muscles and body awareness. This can also affect how touch and pain are experienced. For example, a light touch might feel like it lasts long after it has stopped, or the gentle pressure of clothing might be perceived as uncomfortable or even painful. This is because the limbic's alarm system is exaggerating the body’s signals. The result is symptoms such as tremors, weakness, altered sensations, or unexplained pain that feel completely out of the person’s control.

To understand this better, think of the frontal cortex as the careful driver of a car, using the steering wheel to guide movement and interpret sensory input calmly. The limbic system, on the other hand, is like an alarm system that reacts instantly to danger. It's sensitive and reacts quickly - like a learner driver over-correcting.

In FND, the alarm system takes over the steering wheel, even when there is no real danger. The car still moves, but the movements are jerky, unpredictable, or don’t match what the driver intends. Likewise, the alarm system may signal pain or discomfort even though there's no pain trigger, like a smoke alarm going off without a fire. This explains why FND symptoms are very real—your brain’s “driver” has temporarily lost control to the brain’s “alarm,” leading to genuine, involuntary experiences of weakness, movement changes, or pain.

Rehabilitation helps strengthen frontal control while calming limbic overactivity, restoring a more stable neurological state.

Further Details of Functional Brain Changes in FND

Research shows that FND involves disruptions in multiple brain networks:

• Limbic/salience networks, responsible for emotional regulation and stress responses.

• Self-agency/multimodal integration circuits, involved in the sense of control over movement.

• Attentional networks, which help regulate focus and awareness.

• Sensorimotor circuits, linking movement with body sensation (Perez et al., 2021).

Connectivity dysfunction has been visualised between limbic (emotional) and motoric (movement-related) networks, helping explain why stress or emotional triggers can precede or worsen physical symptoms.

These changes are not unique to FND. Similar functional brain network disruptions are seen in other conditions such as chronic pain. In chronic pain, structural imaging often appears normal, but subtle changes such as cortical thinning and altered network connectivity emerge with more advanced tools. FND appears to share this same “hidden” neuro-biology.

In fact, research has found that people with FND may show differences in brain volume, including:

• Increased size of the amygdala, striatum, cerebellum, fusiform gyrus, and thalamus.

• Decreased size of the sensorimotor cortex (Maurer et al., 2018).

These are subtle changes and are not usually detected on routine clinical imaging, which is why patients are often told their scans are normal.

Diagnosing FND

FND Diagnosis

FND will usually be diagnosed by a neurologist through a detailed clinical examination as well as brain imaging. The neurologist may test muscle strength, reflexes, skin sensation, eye movement, and other neurological functions. These testing helps to exclude other neurological causes of the symptoms and to see if it matches the pattern of FND.

One of the hallmark signs is that symptoms often vary depending on attention or distraction. For example, a patient may show weakness when consciously trying to perform an action, yet that weakness disappears when they are distracted or performing an automatic movement. This pattern helps differentiate FND from other neurological conditions caused by structural damage. These fluctuating findings reflect the underlying imbalance between limbic (emotional/automatic) activity and frontal (executive/regulatory) control, where symptoms can be overridden when brain networks are engaged differently.

Structural Brain Scans for FND

Structural brain scans like MRIs and CTs won't show brain damage. Your doctor will likely tell you your scan is "clear". There's no tumours or bleeds. This is reassuring but doesn't tell you why you are suffering.

Studying the neurobiology of FND is complex because:

• Symptoms are highly variable, ranging from movement disorders to seizures.

• Patients often have co-existing conditions such as anxiety, depression, or chronic pain which have their own associated brain function changes.

• Multiple different pathways may contribute to similar symptoms.

A Functional Approach to FND

The Role of QEEG Functional Brain Scans

One tool that can be used is quantitative electroencephalography (QEEG). Unlike structural imaging (like MRI and CT), QEEG measures the brain’s electrical activity and compares it to healthy patterns.

In FND, QEEG may reveal:

• Excess slow-wave activity (delta/theta) in frontal areas, suggesting reduced executive control.

• Excess beta activity in limbic or temporal regions, reflecting hyper-vigilance and autonomic overdrive.

• Asymmetry between brain hemispheres, showing disrupted communication.

By mapping these patterns, QEEG helps create personalised rehabilitation strategies whilst also validating your real experiences. This is still an evolving area of science as we continue to keep learning about the functional changes seen with FND.

Functional Neurological Examination Approach

A functional neurological examination goes beyond standard reflex and muscle testing. It often includes assessing balance, eye movements, coordination, gait, sensory integration, and autonomic responses. The clinician looks for patterns that reveal how brain networks are functioning rather than just identifying structural damage. For example, subtle eye movement abnormalities, asymmetry in reflexes, or changes in performance under distraction can point to imbalances between frontal and limbic control systems. This detailed functional approach provides a roadmap for targeted rehabilitation.

Functional Neurological Rehabilitation Approaches

A Functional Neurological Chiropractor integrates neurological examination findings with QEEG results to develop targeted rehabilitation programs. These may include:

• Sensorimotor retraining – Exercises to restore normal control of movement and body awareness, moving away from emotional control of sensation and movement.

• Eye movement therapies – Training the oculomotor system to improve attention, balance, and executive control.

• Autonomic regulation – Breathing exercises, vagal stimulation, and graded exposure to reduce stress-driven symptoms.

• Neurofeedback – Teaching patients to actively regulate brainwave patterns for better frontal-limbic control. This may be guided by QEEG functional brain scans or based off symptoms.

• Chiropractic adjustments and vestibular rehab – Providing precise sensory input to stimulate neuroplasticity and integration.

Conclusion

Functional Neurological Disorder is not imaginary, nor is it simply “stress.” It is a brain-based condition rooted in dysfunctional network connectivity and regulation. Research shows clear changes in how the brain processes movement, emotion, and sensation. A chiropractic functional neurological approach combines QEEG-guided assessment with evidence-informed rehabilitation strategies to restore network balance. While the neuroscience of FND is still emerging, personalised neurorehabilitation offers hope for patients to improve symptoms, regain function, and enhance quality of life.