What are the risks of misdiagnosis or delaying FND treatment?

The short version: the evidence on misdiagnosis and treatment delay for FND is thin, and the biggest risk is that a missed neurological disease gets worse while being treated for FND.

The 2026 Italian registry of 847 functional motor disorder patients gives the clearest picture of what delay looks like [1]. Adolescent-onset patients saw an average of 4.4 doctors before diagnosis, compared to 3.4 for adults. Their symptoms lasted an average of 8.4 years before diagnosis versus 4.2 years in adults. That is a long time to be told nothing is wrong or to receive the wrong treatment. The same study found that adolescent patients had higher rates of functional seizures (21.5% vs 12.3%) and more panic attacks (19.4% vs 16.7%) than adults [1]. Whether those are consequences of the delay or features of the underlying disorder is not clear from this data.

The risk of misdiagnosis cuts both ways. A 2020 case report outside this retrieval describes a woman initially diagnosed with FND who was later found to have progressive supranuclear palsy, a neurodegenerative disease. A 2025 case report describes ALS masquerading as multiple system atrophy with parkinsonism and anxiety. These are reminders that FND is a real syndrome, but it can also be a misdiagnosis when a structural or degenerative disease is missed. The Italian registry does not report how many of its 847 patients were later re-diagnosed with something else [1]. That is a significant gap.

The evidence here does not include a single study that compares outcomes for patients diagnosed early versus late, or that tracks misdiagnosis rates over time. The Italian study shows that delay is common, especially in adolescents, but it does not measure what that delay costs in terms of permanent disability, missed treatment windows, or unnecessary procedures [1]. Without that comparison, the risk of delay is inferred, not proven.

My call: the evidence shows that diagnostic delay is real and longer for adolescents, but no study in this retrieval measures the harm it causes. The biggest documented risk is that a missed neurological disease progresses untreated. Confidence: low.