Claims involving neurological, cognitive or fatigue-related symptoms without clear structural pathology are among the most challenging in personal injury and clinical negligence litigation. In this editorial, Dr Bruno Silva explores how functional neurological presentations are clinically assessed, why they are often misunderstood, and how expert neuropsychiatric evidence can assist the court.

You can watch the full webinar with Dr Bruno Silva here →

Why This Issue Arises in Medico-Legal Claims

Solicitors frequently encounter cases where claimants report disabling symptoms - weakness, seizures, cognitive problems or fatigue - yet imaging and investigations appear normal or non-explanatory. These cases often arise following road traffic accidents, mild traumatic brain injury, delayed diagnosis, critical illness or surgical complications.

From a medico-legal perspective, this creates tension between subjective symptom burden and objective findings. Defendants may argue exaggeration, lack of causation or alternative explanations, while claimants struggle to understand why they feel profoundly impaired despite being told that “nothing is wrong”. It is within this space that functional neurological disorder (FND) and related presentations commonly emerge.

Clinical Background

Functional neurological symptoms are real, involuntary and disabling.
They are not put on, exaggerated or consciously produced.

From the patient’s perspective, these symptoms are indistinguishable from symptoms caused by other injuries or structural disease. Patients do not experience them as “functional”. They experience them as real symptoms that affect their day-to-day functioning.

These presentations commonly affect movement, cognition and physical functioning. Patients may report weakness of the arms or legs, sometimes to the point of paralysis. Others develop problems with walking, balance or coordination, or experience tremors and abnormal movements.

Seizure-like episodes are also common. These events can look identical to epileptic seizures to an untrained observer, but are not associated with epileptic activity on EEG. Cognitive complaints frequently arise as well, particularly problems with memory, concentration and mental efficiency. Fatigue and persistent pain are often part of the clinical picture.

A key feature of functional symptoms is that they are internally inconsistent. Symptoms may fluctuate in severity, appear and disappear, or vary within the same examination. Despite this variability, there is usually a recognisable pattern over time when a careful history is taken.

Symptoms are often influenced by attention, expectation and perceived threat. When patients focus on a symptom, it may worsen. When they are distracted or feel less threatened, symptoms may temporarily reduce or even disappear.

This fluctuation is frequently misunderstood in litigation. Clinically, however, it is a recognised and meaningful feature of functional neurological presentations rather than evidence of exaggeration or dishonesty.

Diagnostic Complexity and Evidential Challenges

One of the most persistent misconceptions is that functional neurological disorder is a diagnosis of exclusion. It is not.

FND is diagnosed clinically, based on positive signs that demonstrate incompatibility between the symptom presentation and structural neurological disease. These signs can be elicited during examination and do not rely on normal investigations to “rule everything else out”.

From an evidential standpoint, difficulty arises when:

• Investigations are normal or only partially explanatory
• Symptoms appear inconsistent on observation
• Multiple experts are involved without a cohesive formulation
• The claimant has been repeatedly reassured without explanation

Without a clear diagnostic framework, cases can drift into disputed credibility rather than clinical analysis.

Functional vs Organic Presentations

The distinction between functional and organic pathology is often misunderstood.

“Functional” does not mean psychological, imagined or medically unexplained. It refers to disordered function rather than structural damage. This distinction exists throughout medicine - migraines, asthma and cardiac arrhythmias frequently occur without visible structural abnormalities, yet are not considered controversial.

In functional neurological disorder, the “hardware” (brain structure) may appear intact, while the “software” (brain networks governing movement, attention and cognition) functions inefficiently. Importantly, functional and organic conditions can coexist, adding further complexity to medico-legal assessment.

Causation in Disputed or Non-Structural Cases

Causation in functional neurological presentations is rarely straightforward or linear. In neuropsychiatric practice, causation is typically understood using a vulnerability, trigger and maintaining factors framework rather than a single-cause model.

Many patients have pre-existing vulnerabilities that may increase their susceptibility to developing functional symptoms. These can include early life adversity, trauma, personality traits such as perfectionism, or prior health experiences that shape how symptoms are perceived and managed.

Symptoms are often precipitated by a triggering event. In medico-legal cases, this is frequently an accident, physical injury, prolonged pain, diagnostic delay or the consequences of negligent care. These events can materially alter how symptoms emerge, even where the initial physical injury appears limited.

Once symptoms develop, a range of maintaining factors may contribute to their persistence. Ongoing disability, uncertainty about diagnosis, repeated investigations, maladaptive coping patterns and the wider consequences of illness can all play a role. The litigation process itself may also act as a maintaining factor, not through intent, but through prolonged focus on symptoms and delayed access to appropriate treatment.

A common medico-legal misconception is that the presence of vulnerability means the condition would have developed in any event. This is not supported by clinical evidence. Most individuals with pre-existing vulnerabilities never go on to develop functional neurological disorder.

In many cases, the triggering event plays a material role in the onset of symptoms, even if it is not the sole contributing factor. From a medico-legal perspective, causation is therefore best understood as the interaction between vulnerability, trigger and maintenance, rather than a simple one-to-one relationship.

Prognosis and Long-Term Outcome Assessment

Prognosis in functional neurological disorder is variable and conditional. Outcomes depend heavily on:

• Early and accurate diagnosis
• Quality of explanation given to the patient
• Engagement with diagnosis-matched treatment
• Duration of symptoms before intervention

Broadly, studies suggest:

• 30-40% show meaningful improvement
• 30-40% show partial improvement
• 20-30% show little change despite treatment

Prolonged diagnostic uncertainty, repeated investigations and mismatched rehabilitation pathways are associated with poorer outcomes - all factors commonly encountered in litigated cases.

Medico-Legal Considerations

From a legal standpoint, these cases raise important questions around:

• Foreseeability of functional outcomes following injury or delay
• Standard of care in recognising and explaining symptoms
• Causation where symptoms exceed structural findings
• Defensibility of expert opinion in the face of symptom fluctuation

Clear, well-reasoned neuropsychiatric evidence can assist the court by explaining why inconsistency is expected, how causation is assessed probabilistically, and what recovery realistically looks like.

Common Pitfalls in Litigation

Claims involving functional symptoms are often undermined by a series of recurring misunderstandings rather than by any inherent weakness in the evidence.

One common pitfall is treating inconsistency as evidence of dishonesty. In functional neurological disorder, variability and fluctuation are expected clinical features. They reflect how symptoms are influenced by attention, context and perceived threat, not conscious exaggeration or fabrication.

Another frequent error is placing undue weight on normal imaging or investigations. Functional symptoms are not defined by the absence of findings on scans, and normal results do not mean that nothing is wrong. Over-reliance on imaging can lead to premature dismissal of genuine disability.

Difficulties also arise around symptom validity testing. Failed or borderline validity scores are sometimes interpreted as proof of malingering, despite the fact that these tests do not establish intent. In functional presentations, uneven attention, distress and altered cognitive control can all affect performance and must be interpreted in context.

Claims are further weakened where there is no coherent, multi-expert formulation. Without alignment between neurological, neuropsychological and neuropsychiatric evidence, symptoms may appear fragmented or contradictory rather than clinically integrated.

Finally, delayed or inappropriate expert instruction can entrench problems. Late recognition of functional mechanisms often results in mismatched rehabilitation, prolonged symptoms and avoidable dispute around causation and prognosis.

Taken together, these pitfalls usually reflect misunderstanding of functional presentations, rather than any lack of legitimacy in the underlying claim.

Case Examples and Learning Points

In one anonymised clinical negligence case discussed by Dr Silva, a delayed diagnosis caused prolonged pain and uncertainty. Although surgical outcome was ultimately successful, the claimant developed non-epileptic seizures, cognitive symptoms and fatigue.

The key learning points were:

• Functional symptoms arose from the consequences of delay, not structural damage
• There was no evidence of malingering despite symptom inconsistency
• Rehabilitation had been mismatched to diagnosis, prolonging disability
• Neuropsychiatric formulation clarified causation and treatment needs

Such cases highlight how functional outcomes can materially affect prognosis and quantum, even where physical injury appears limited.

Key Takeaways for Solicitors

• Functional symptoms are real, involuntary and disabling
• Normal investigations do not preclude genuine pathology
• Inconsistency is a diagnostic feature, not evidence of exaggeration
• Causation is multifactorial but still legally assessable
• Correct expert sequencing strengthens evidential value

When Expert Evidence Is Critical

Neuropsychiatric expert evidence becomes particularly important where symptoms cannot be fully explained by structural findings. This is often the point at which cases become disputed, not because symptoms are absent, but because existing evidence does not adequately account for them.

Expert input is especially valuable where symptoms exceed or mismatch what would be expected from identified physical injury. In these cases, neuropsychiatric assessment can explain why symptoms persist despite normal or limited findings on imaging or investigation.

Disputes around causation and credibility are another common trigger for instruction. Where functional mechanisms are not recognised, symptoms may be mischaracterised as exaggerated or inconsistent. Neuropsychiatric evidence can provide a clinical framework that explains variability without attributing intent.

Neuropsychiatric expertise is also critical where symptom validity testing has raised concerns. These results require careful interpretation and must be considered alongside history, presentation and examination, rather than treated as determinative in isolation.

Finally, expert input is often needed where prognosis remains unclear despite the passage of time. Functional symptoms may persist longer than expected following physical injury, and without appropriate formulation, this can be misinterpreted as evidence against causation.

Early, well-scoped instruction is key. When neuropsychiatric evidence follows cohesive neurological or neurosurgical opinion, it allows for an integrated formulation that strengthens evidential clarity and avoids fragmented expert debate.

Closing Thoughts

Symptoms without clear pathology sit at the intersection of medicine, law and human experience. They challenge binary thinking and demand careful, evidence-led analysis. When approached correctly, neuropsychiatric expertise can bring clarity to complexity - supporting fair outcomes for both claimants and defendants.

Watch the full webinar here →