Functional Motor Symptoms in Parkinson’s Disease and Functional Parkinsonism: A Systematic Review

Abstract

Whereas functional symptoms are common in Parkinson's disease (PD), a parkinsonian syndrome may occasionally reflect a pure functional disorder (also named functional parkinsonism [FP]). This review aimed to decipher these entities to clarify the link between functional manifestations and PD.Methods: Following the PRISMA guidelines, the authors performed a systematic literature search of the PubMed and Science Direct databases for the period 1988 to December 2018 to identify studies of patients with either FP or PD associated with functional neurological symptoms.Results: From the 844 articles screened, 22 were retained, including 12 studies of functional neurological symptoms in PD and 16 studies of FP. The studies of functional symptoms in PD included 121 patients-57% were women, and the mean age was 61.3 years. Psychiatric history (mostly depression) and exposure to triggering stressors were frequent: 60% and 82.5%, respectively. The most common symptom was tremor (33.8%), most often located on the side most affected by PD (50%). Studies of FP included a total of 120 patients-62% were women, and the mean age was 50.7 years. The first FP symptoms appeared on average 5 years before diagnosis, with an abrupt onset in half the cases; 67.6% had a psychiatric history, and 46.8% were exposed to triggering stressors, such as physical injury, stress at work, or loss of family or friends. Conclusions:Findings suggest a possible relationship between PD and FP. Clinicians should keep in mind the possibility of functional symptoms in PD patients.

Functional motor disorders associated with other neurological diseases: Beyond the boundaries of “organic” neurology

“…The same network abnormalities, together with abnormal overweighting of prior expectancies about symptoms might distort sensory perception [33] and contribute to the development of comorbid FMDs. We do not have enough evidence to explain the occurrence of FMDs before PD, but it is likely that functional symptoms arise through the same network [34] and neurochemical abnormalities [4].…”

“…A prospective study found that 19.6% and 8.9% of patients assessed in the emergency department had comorbid functional symptoms in addition to stroke and migraine, respectively [9]. A recent systematic review showed that onset of functional symptoms often predated or occurred at the same time as PD diagnosis and was more likely to involve the side most affected by parkinsonism [4]. Another systematic review highlighted a 12% frequency of paroxysmal non‐epileptic seizures (PNES) in subjects with a primary diagnosis of epilepsy [10], whereas the reported rate of epilepsy among a large sample of people with a primary diagnosis of PNES was 5.3% [11].…”

Demographic and clinical characteristics of patients with functional motor disorders: the prospective Salpêtrière cohort

“…To note, there was a tendency towards older age at onset in movement disorders, notably in patients with functional parkinsonism (mean: 48.3 years old). In a recent literature review, the mean age at onset in functional parkinsonism was 45.6 years (Ambar Akkaoui et al 2020). On the contrary, age at onset was lower in functional dystonia (mean: 35.2), and this is also in agreement with a previous study that found age at onset of 29.6 years old in functional dystonia.…”

“…Recent studies have suggested that some phenotypes affect more one gender or one age range. For example, previous studies suggested that functional myoclonus affects more men (55%)(van der Salm et al 2014), while functional parkinsonism is more frequent in older patients (Ambar Akkaoui et al 2020). Some controversies also exist about FMD affecting more the left side of the body (J.…”

Searching for Peripheral Biomarkers in Neurodegenerative Diseases: The Tryptophan-Kynurenine Metabolic Pathway

“…Abnormal deposit of insoluble proteinaceous material amyloid beta (Aβ) in the neuron and glial cells is mainly located in the atrophic lesions of AD patients [52]. Tau [53]. Disturbance of calcium homeostasis was observed, and calcium-related proteins were proposed to be diagnostic and therapeutic biomarkers in AD [54].…”