Objective: To describe a consecutive cohort of patients with non-functional neurological diseases that were initially diagnosed as Functional Movement Disorders (FMD).

Background: Functional and non-Functional neurological disorders may be hard to differentiate. A rate of 6-8% misdiagnosis has been reported, which is similar to that seen in other neurological and psychiatric disorders[1]. In this study we report our clinical experience.

Method: Retrospective chart review of consecutive patients evaluated in our FMD Unit between January 2017 and February 2022. Patients with no positive signs of FMD during our first consultation and with a final diagnosis other than FMD were identified. Patients who were thought to have “functional overlay” were excluded. Clinical and demographic features were extracted, with special focus on data from history and/or neurological exam that initially suggested FMD diagnosis.

Results: Of 244 patients evaluated, 20 (8.19%) eventually had an alternative diagnosis different to FMD (85% females, mean age 58.52+15.96 years). Eight patients had a previous history of a neurological disease (primary headaches and epilepsy) and 12 had a previous history of a psychiatric disease (75% depression and/or anxiety disorder). Most common clinical presentations were gait disorders, followed by muscle spasms or dystonia and limb weakness. Onset was acute/subacute in 12 (60%) cases. Most patients (85%) identified a plausible trigger in the preceding 3 months to symptom onset (50% were psychological). Inconsistency and variability of motor symptoms on exam as well as psychological comorbidity were the most common features associated with the initial diagnosis of FMD. Final diagnosis was: motor neuron disease (4), spastic paraparesia (2), corticobasal syndrome (including one prion disease) (2), idiopathic dystonia (4), inheritedmyopathy (2), parkinsonism (2), stiff person syndrome (1), frontal ataxia (1), tics (1) and obsessive-compulsive disorder (1).

Conclusion: We found that 8% of patients who were referred to our FMD Unit eventually had an alternative diagnosis. This is similarly to that previously reported and support that the follow-up of patients with suspected FMD is essential. In our experience, features such as middle age, being female, acute onset and a previous history of a psychiatric disease were pitfalls that might have introduced a diagnostic bias[2].

References: 1. Stone J, Smyth R, Carson A, Lewis S, Prescott R, Warlow C, Sharpe M. Systematic review of misdiagnosis of conversion symptoms and “hysteria”. BMJ. 2005 Oct 29;331(7523):989.
2. Stone J, Reuber M, Carson A. Functional symptoms in neurology: mimics and chameleons. PractNeurol. 2013 Apr;13(2):104-13.

« Back to 2022 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/what-if-it-is-not-a-functional-movement-disorder/