Depression, anxiety and panic are more frequent in patients with functional weakness than in controls with comparable neurological disease, but roughly a third of patients have no psychiatric diagnosis at all, so comorbidity cannot confirm the diagnosis. Similarly, financial and interpersonal consequences of illness are found in most chronic conditions and do not distinguish functional from organic disability. The diagnostic weight lies with the positive neurological findings.
Where these factors do matter is prognosis and management. Systematic review of outcome in functional motor symptoms shows that long symptom duration, established disability, receipt of financial benefits, ongoing litigation and a personality disorder are associated with poorer outcome, whereas short duration, early diagnosis, a positive explanation and younger age favour recovery. Overall, about two-fifths of patients are the same or worse at follow-up. Reinforcing disability with wheelchairs, adaptations and caregiver dependence without a rehabilitation plan compounds the problem, which is why aids should be prescribed cautiously and alongside active treatment.
On the ABPN blueprint this maps to the Clinical aspects of neurologic disease axis, because the competency is applying knowledge of natural history and prognostic factors to a chronic presentation. The practical message is to treat early, avoid entrenching disability, and treat comorbid depression on its own merits rather than as proof of the neurological diagnosis.
Incorrect Answers
- A. Secondary gain and psychiatric comorbidity were removed from or never formed part of the positive criteria; both occur commonly in organic disease.
- B. Around one third of patients with functional disorders have no psychiatric comorbidity, so depression is neither necessary nor confirmatory.
- C. Settlement of litigation does not reliably lead to recovery; symptoms commonly persist after claims conclude.
- E. Duration is one of the most consistent predictors of outcome, with longer duration predicting worse recovery.
Testing Pearls
- Psychiatric comorbidity is common but is not a diagnostic criterion for functional disorder.
- Around 40 percent of patients with functional motor symptoms are unchanged or worse at follow-up.
- Short duration, early positive diagnosis and younger age predict better outcome.
- Benefits, litigation and entrenched disability are associated with poorer prognosis.
- Prescribe wheelchairs and adaptations cautiously and only alongside active rehabilitation.
References
- Jankovic J, Mazziotta JC, Newman NJ, Pomeroy SL, editors. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022. p. 2078-2079.
- Gelauff J, Stone J, Edwards M, Carson A. The prognosis of functional (psychogenic) motor symptoms: a systematic review. J Neurol Neurosurg Psychiatry. 2014;85(2):220-226.
- Stone J, Warlow C, Sharpe M. The symptom of functional weakness: a controlled study of 107 patients. Brain. 2010;133(Pt 5):1537-1551.
