Functional/Dissociative Seizures and Epilepsy

Diagnosis and differential diagnosis

Functional/dissociative seizures are real, involuntary seizure-like episodes that are not caused by the abnormal electrical activity that defines epileptic seizures. They can look very similar to epilepsy, can be disabling, and can occur in people who also have epilepsy.

Key point: functional/dissociative seizures are not faked or deliberately produced. They are a recognised neurological disorder. The ILAE now recommends the term functional/dissociative seizures (FDS) as a more consistent international label.

What are functional/dissociative seizures?

Functional/dissociative seizures are episodes of altered movement, awareness, sensation, behaviour or responsiveness that resemble epileptic seizures but arise through different mechanisms.

They are part of the spectrum of functional neurological disorder. The symptoms are genuine and involuntary, even though routine seizure-related electrical discharges are not responsible for the attacks.

Why the terminology has changed

Older terms include psychogenic non-epileptic seizures (PNES), non-epileptic attacks and non-epileptic attack disorder (NEAD).

In 2025 the ILAE Functional/Dissociative Seizures Task Force proposed functional/dissociative seizures as the preferred diagnostic label after reviewing terminology, patient acceptability, clinical use and international classification systems.

Functional does not mean imaginary

“Functional” describes a problem with how brain networks are functioning rather than a structural lesion that is visible on a routine scan.

A person does not choose the seizure, and the symptoms are not under normal voluntary control.

Dissociative does not mean everyone has trauma

Dissociation can be one mechanism involved in some people, and trauma, stress, anxiety or other psychological difficulties may be relevant in some cases.

However, not everyone with functional/dissociative seizures has a trauma history, and the diagnosis should not be reduced to “stress caused it”. Modern models are biopsychosocial and recognise interacting neurological, psychological and social factors.

Functional seizures and epileptic seizures are different

Epileptic seizures are caused by abnormal excessive or synchronous electrical activity in the brain. Functional/dissociative seizures are not.

Because the mechanisms differ, treatment differs too. Antiseizure medicines treat epileptic seizures but do not treat functional seizures unless the person also has epilepsy or another reason for taking them.

A person can have both

Functional/dissociative seizures and epilepsy can coexist. This is one of the most important reasons not to assume that every new event in a person with epilepsy is epileptic — or that a functional-seizure diagnosis means epilepsy was never present.

A 2025 study of 460 people with established FDS found a subgroup with clinically established or video-EEG documented co-occurring epilepsy, while a larger intermediate group had possible or probable evidence requiring further assessment.

In a 2026 inpatient video-EEG study of people with idiopathic generalised epilepsy, functional/dissociative seizures were documented in some patients and epileptic seizures were also captured in nearly half of those with FDS during the same admission.

Why coexistence can be difficult to recognise

A person may have two or more event types that look similar from the outside. One may be epileptic and another functional.

This can lead to escalating antiseizure medication for events that will not respond to it, while true epileptic seizures may still need treatment.

Video-EEG is often the most useful diagnostic test

When the diagnosis is uncertain, capturing a typical event on video-EEG can allow clinicians to compare the visible episode with the EEG at the same time.

AAN guidance published in 2026 recommends obtaining video-EEG of typical seizure-like episodes where feasible and assessing for co-occurring epilepsy.

A normal routine EEG does not diagnose functional seizures

Routine EEG can be normal in someone who has epilepsy. Conversely, an abnormal interictal EEG does not prove that every event is epileptic.

Diagnosis depends on the clinical history, event semiology, witness accounts, videos and—when available—capturing typical events on video-EEG.

Read more: Diagnosis and Tests →

There is no single movement that proves FDS

Certain features are more common in functional/dissociative seizures, including prolonged duration, fluctuating intensity, sustained eye closure and some patterns of movement.

However, no single sign is reliable enough to diagnose FDS by itself. Many features overlap with epileptic seizures, and diagnosis should be made by clinicians experienced in seizure disorders.

Duration can help—but not diagnose

Functional seizures are often longer than epileptic seizures when objectively timed, but duration is highly variable.

A 2026 systematic review found that prolonged events increase the likelihood of FDS, but no duration cut-off can safely separate functional from epileptic seizures on its own.

Smartphone video can be useful

A good-quality recording of a typical event may provide valuable semiological information, especially when clinicians cannot directly witness an episode.

AAN guidance recommends using historical information, witness descriptions and smartphone video where available.

Safety must always come before filming.

Why “drug-resistant epilepsy” sometimes needs re-evaluation

If repeated seizure-like episodes continue despite appropriate antiseizure medicines, clinicians should reconsider whether every event is epileptic.

Some people referred for suspected drug-resistant epilepsy are ultimately found to have functional seizures, while others have both conditions.

First aid: protect, observe, avoid harm

During a known functional/dissociative seizure:

protect the person from injury
move dangerous objects away
time the episode
stay calm and reduce unnecessary stimulation
do not restrain them
do not put anything in the mouth
allow recovery in a safe environment

The person’s individual care plan should guide what carers do when event types are already well characterised.

Do not assume every prolonged event is status epilepticus

Prolonged functional seizures can be mistaken for convulsive status epilepticus. This can lead to repeated benzodiazepines, intubation and intensive-care treatment that may not help and can cause harm.

At the same time, true status epilepticus is life-threatening. If the event is new, the diagnosis is uncertain, breathing is abnormal, injury occurs, or the person has known epilepsy and the event could be epileptic, emergency assessment remains appropriate.

Rescue medication needs a clear plan

Rescue benzodiazepines are used for prolonged epileptic seizures or clusters when prescribed in an emergency plan. They do not treat functional seizures.

For someone who has both epilepsy and FDS, the care plan should make the event types and rescue-medication criteria as clear as possible.

When to call 999

Emergency help may still be needed when:

the event is the person’s first or the diagnosis is uncertain
there is serious injury
breathing is abnormal or not recovering
the person remains unresponsive beyond their usual pattern
there is suspected epileptic status or repeated epileptic seizures without recovery
the event follows a significant head injury
something about the episode is clearly different from the person’s established pattern

Treatment is not the same as epilepsy treatment

Functional seizures are usually managed through explanation of the diagnosis, education, treatment of relevant comorbidities and—when appropriate—psychological therapy.

The 2026 AAN practice guideline concluded that psychological interventions are possibly effective for reducing functional-seizure frequency and improving anxiety, quality of life and psychosocial functioning.

Psychological treatment does not mean the symptoms are imaginary

Psychological therapies can change brain and behavioural processes involved in symptoms. Their use does not imply that a person is inventing their seizures.

CBT-based and other structured therapies may be used depending on the person’s formulation, goals and comorbidities.

Not everyone needs the same therapy

Functional neurological disorder is heterogeneous. Treatment may need to address anxiety, depression, trauma-related symptoms, chronic pain, sleep, dissociation, relationship stress, avoidance, physical deconditioning or other relevant factors.

Some people benefit from multidisciplinary care involving neurology, psychology or psychiatry, physiotherapy, occupational therapy or other services.

Antiseizure medicines should not be used to treat FDS alone

The AAN guideline advises against antiseizure medicines for functional seizures when there is no co-occurring epilepsy or another indication.

If epilepsy has been excluded and there is no other reason for the medicine, withdrawal should be supervised rather than abrupt.

Communication of the diagnosis matters

A diagnosis of FDS should be explained positively: what the diagnosis is, why the clinician believes it fits, what it is not, and what treatment options exist.

AAN guidance recommends a specific diagnostic label, clear rationale, shared decision-making and continuity of care.

Simply saying “your tests are normal” or “it is psychological” is not an adequate explanation.

Stigma can make outcomes worse

People with functional seizures are sometimes accused of attention-seeking or faking. This is inaccurate and damaging.

The AAN guideline explicitly recommends respectful care and avoiding stigmatizing behaviour.

Epilepsy and FDS can require two care plans in one

When both conditions coexist, the plan should describe each event type separately:

what the event usually looks like
how awareness and responsiveness change
usual duration
usual recovery
what first aid is needed
whether rescue medication is appropriate
when emergency help is required

Read more: Epilepsy Care Plans →

What should be recorded in a seizure diary?

If a person has more than one event type, record each as precisely as possible:

what happened first
movements and eye position
awareness and responsiveness
duration
breathing and colour
injury
recovery pattern
possible triggers or context
whether rescue medication was used

Avoid labelling an event “epileptic” or “functional” unless the event type has already been clinically established.

The central point

Functional/dissociative seizures are real seizures of function, not epileptic electrical seizures and not deliberate behaviour.

They can coexist with epilepsy, which makes careful diagnosis, video-EEG when appropriate, respectful communication and a clear event-specific care plan especially important.

Where next?

Diagnosis and Tests →
Seizure Types →
Drug-Resistant Epilepsy →
Epilepsy Care Plans →
Back to Understanding Epilepsy →

Sources

Medical note: Seizure-like episodes need proper clinical assessment. Functional/dissociative seizures, epileptic seizures and other causes of collapse can overlap clinically, and some people have both FDS and epilepsy. Do not stop antiseizure medication or change rescue-medication plans without specialist advice.