Functional neurological disorder — conversion, dissociative seizures and paralysis

What a functional neurological disorder is

In a functional neurological disorder (FND) the nervous system's function fails while its structure is intact. Nerves, muscles and brain are sound, but the signal does not get through, or gets through wrongly. The result is neurological symptoms as real and as disabling as those caused by injury — but invisible on a scan, and not following the anatomy of the nerves.

The older name is conversion disorder: the feeling is "converted" into a bodily symptom. In ICD-10, as used in Denmark, these conditions sit under F44, dissociative and conversion disorders, next to the other dissociative disorders. That is no accident: it is the same mechanism. Where DID and depersonalisation are a disconnection of awareness and identity, conversion is a disconnection of the body's control.

We are licensed psychologists in Frederiksberg, central Copenhagen, and we offer the same treatment online, in English, anywhere in Denmark.

The symptoms

• Dissociative / functional seizures (PNES) — attacks with shaking, loss of awareness or freezing that look like epilepsy, but with no epileptic activity on EEG. About one in five people referred to a specialist epilepsy centre for drug-resistant epilepsy turn out to have functional seizures. Some have both epilepsy and dissociative seizures — and what happens with anti-epileptic medication is always the neurologist's decision.
• Functional paralysis and weakness — a leg or an arm that will not, often after a minor injury, an operation or a severe strain.
• Functional tremor, dystonia and gait disturbance.
• Sensory loss — numbness, loss of vision or hearing, tunnel vision.
• Functional aphonia and speech difficulty — the voice goes, or the words will not come.
• Functional cognitive symptoms — memory and concentration failing, without dementia.

The diagnoses

• F44.4 Dissociative motor disorder. F44.5 Dissociative convulsions. F44.6 Dissociative anaesthesia and sensory loss. F44.7 Mixed.
• ICD-11: 6B60 Dissociative neurological symptom disorder. DSM-5-TR: Functional neurological symptom disorder (conversion disorder).

The diagnosis is made by a neurologist — and it is made positively, on signs characteristic of FND (such as Hoover's sign in functional leg weakness, or the course of an attack), not merely by ruling everything else out. That matters: a functional diagnosis is not "we could not find anything". It is "we found something specific". If you have not seen a neurologist, we help get that started, and we work with neurologists and psychiatrists where it helps.

What it is not

It is not imagination. It is not malingering. It is not weakness of character, and it is not something to pull yourself together from — most people with FND have been pulling themselves together for years. The symptoms are not produced on purpose, and they are no more under voluntary control than a panic attack. Many have been told "there is nothing wrong" and gone home with a leg that still will not carry. That is the worst message to receive: it says nobody knows what to do. We do.

The body carries what could not be felt — the ISTDP understanding

We work with Intensive Short-Term Dynamic Psychotherapy (ISTDP) as developed and researched by Allan Abbass, professor of psychiatry at Dalhousie University, Canada, with whom Simon Secher trained. Over twenty years Abbass has described how unconscious feelings become bodily symptoms — and developed a treatment built on exactly that understanding.

The model is this. When a person is hurt by someone they are attached to, feelings arise that have no room: rage at the person one loves and depends on; grief; guilt about the rage. They cannot be felt without threatening the attachment, so they are repressed. But feelings do not vanish because they are repressed. In their place comes unconscious anxiety — and that anxiety, in Abbass's account, takes one of a few fixed pathways in the body:

1. Striated muscle — tension, sighing, restlessness. The anxiety is felt, and borne.
2. Smooth muscle — gut (irritable bowel), airways, migraine, blood pressure. Felt not as anxiety but as illness.
3. The cognitive–perceptual field — thinking stops, vision blurs, you are "not there": dissociation.
4. Motor conversion — as the feeling approaches, the body's control switches off: the leg goes heavy, the hand shakes, the voice goes, or a seizure comes. That is FND.

What makes this understanding useful is that it can be seen in the room. In the session we follow not only what you say but what happens in your body as you say it. As we approach a feeling — typically a rage that was never allowed to exist — we can watch the anxiety change pathway: the leg goes heavy, the hand starts to shake, the eyes glaze. There we stop. Not to avoid the feeling, but to bring the anxiety down so that a little more can be felt. And a little more next time. That is building capacity.

As capacity grows, the feeling can be felt all the way through — rage as rage, grief as grief, guilt as guilt, aimed at the people it belongs to. When it can, the body has nothing left to carry. The symptom can lose its function and fade. That is not a side effect of the treatment; it is the treatment. It is why ISTDP for FND is not about learning to live with it, but about it being able to stop. We do not promise an outcome — nobody can — but we work towards it, not around it.

What the research shows

• In a study of 28 patients with dissociative seizures (PNES), healthcare costs after ISTDP fell by 88% in the first year, 90% in the second and 81% in the third compared with the year before — after an average of fewer than four sessions (Russell, Abbass et al., 2016).
• A UK study in 2023 found a similar reduction in healthcare use among patients with functional seizures treated with ISTDP in a neurology service (Malda-Castillo et al., 2023).
• Meta-analyses of short-term dynamic therapy for functional somatic disorders show effects on symptoms, function and wellbeing that hold or grow after treatment ends (Abbass et al., 2009, 2020, 2021).
• A 2025 scoping review gathers the ISTDP studies across functional somatic and neurological disorders, including functional movement disorders and seizures (Abbass & Haghiri, 2025).

To be plain: the FND-specific studies are small and uncontrolled. What is solid is the method and its evidence across the bodily conditions. All references are below, with links.

How the treatment goes

1. First session: understanding. We go through the symptoms, your neurological assessment and the history behind them — and we begin at once to watch what happens in the body as we approach what is difficult. Most people get an explanation they recognise in the first hour.
2. Anxiety regulated, capacity built. We work with the feelings in doses the body can bear, and stop when the anxiety changes pathway. It is not confrontation. It is training.
3. The feelings felt through. When the capacity is there, what was repressed can be felt — and the symptom can lose its reason.
4. Ending and follow-up. Many FND courses are shorter than for DID and OSDD; where serious developmental trauma lies underneath, it takes longer. We judge it together after the first sessions.

REAC neuromodulation as a supplement

As a supplement to psychotherapy we offer REAC neuromodulation — a gentle, non-invasive treatment aimed at regulating the nervous system, which we are the only clinic in Denmark to provide. In functional neurological disorders the nervous system's baseline arousal is often high, and a high baseline makes it harder to feel without the body disconnecting. REAC can lower that baseline so there is more to work with in the sessions. Psychotherapy is the treatment; REAC supports it. It is optional, and we do not offer it on its own.

Research

• Russell LA, Abbass AA, Allder SJ, Kisely S, Pohlmann-Eden B, Town JM (2016). A pilot study of reduction in healthcare costs following the application of intensive short-term dynamic psychotherapy for psychogenic nonepileptic seizures. Epilepsy & Behavior, 63, 17–19. doi.org/10.1016/j.yebeh.2016.07.017
• Malda-Castillo J, Howell B, Russell L, Town J, Abbass A, Perez-Algorta G, Valavanis S (2023). Intensive Short-Term Dynamic Psychotherapy (ISTDP) associated with healthcare reductions in patients with functional seizures. Epilepsy & Behavior, 141, 109147. doi.org/10.1016/j.yebeh.2023.109147
• Abbass A, Town J, Holmes H, Luyten P, Cooper A, Russell L, Lumley MA, et al. (2020). Short-Term Psychodynamic Psychotherapy for Functional Somatic Disorders: A Meta-Analysis of Randomized Controlled Trials. Psychotherapy and Psychosomatics, 89(6), 363–370. doi.org/10.1159/000507738
• Abbass A, Lumley MA, Town J, Holmes H, Luyten P, Cooper A, Russell L, et al. (2021). Short-term psychodynamic psychotherapy for functional somatic disorders: A systematic review and meta-analysis of within-treatment effects. Journal of Psychosomatic Research, 145, 110473. doi.org/10.1016/j.jpsychores.2021.110473
• Abbass A, Kisely S, Kroenke K (2009). Short-term psychodynamic psychotherapy for somatic disorders: systematic review and meta-analysis of clinical trials. Psychotherapy and Psychosomatics, 78(5), 265–274. doi.org/10.1159/000228247
• Abbass A, Haghiri B (2025). Intensive Short-Term Dynamic Psychotherapy for Functional Somatic Disorders: A Scoping Review. Clinical Neuropsychiatry, 22(2), 111–120. doi.org/10.36131/cnfioritieditore20250201
• Abbass A, Town J, Driessen E (2012). Intensive Short-Term Dynamic Psychotherapy: A Systematic Review and Meta-analysis of Outcome Research. Harvard Review of Psychiatry, 20(2), 97–108. doi.org/10.3109/10673229.2012.677347

Full reference list with DOIs: research and references (in Danish).