ABSTRACT
Functional movement disorders (FMD) are proposed to reflect a specific problem with voluntary control of movement, despite normal intent to move and an intact neural capacity for movement. In many cases, a positive diagnosis of FMD can be established on clinical grounds. However, the diagnosis remains challenging in certain scenarios, and there is a need for predictors of treatment response and long-term prognosis.In this context, we performed a systematic review of biomarkers in FMD. Eighty-six studies met our predefined criteria and were included.We found fairly reliable electroencephalography and electromyography-based diagnostic biomarkers for functional myoclonus and tremor. Promising biomarkers have also been described for functional paresis, gait and balance disorders. In contrast, there is still a lack of diagnostic biomarkers of functional dystonia and tics, where clinical diagnosis is often also more challenging. Importantly, many promising findings focus on pathophysiology and reflect group-level comparisons, but cannot differentiate on an individual basis. Some biomarkers also require access to time-consuming and resource-consuming techniques such as functional MRI.In conclusion, there are important gaps in diagnostic biomarkers in FMD in the areas of most clinical uncertainty. There is also is a lack of treatment response and prognostic biomarkers to aid in the selection of patients who would benefit from rehabilitation and other forms of treatment.
Subject(s)
Brain/diagnostic imaging , Conversion Disorder/diagnosis , Electroencephalography , Electromyography , Functional Neuroimaging , Movement Disorders/diagnosis , Biomarkers , Brain/physiopathology , Conversion Disorder/physiopathology , Dystonia/diagnosis , Dystonia/physiopathology , Gait Disorders, Neurologic/diagnosis , Gait Disorders, Neurologic/physiopathology , Humans , Magnetic Resonance Imaging , Movement Disorders/physiopathology , Myoclonus/diagnosis , Myoclonus/physiopathology , Neuronal Plasticity , Paresis/diagnosis , Paresis/physiopathology , Positron-Emission Tomography , Reaction Time , Tics/diagnosis , Tics/physiopathology , Tremor/diagnosis , Tremor/physiopathologyABSTRACT
Levodopa-induced dyskinesia (LID) represents a severe adverse effect of long-term treatment of Parkinson's disease with levodopa. Neuroimaging studies have contributed to our understanding of LID and may help to identify patients at risk of developing LID. Amantadine can be used for the treatment of LID, and novel drugs are under development. Deep brain stimulation of the subthalamic nucleus and globus pallidus internus alleviates LID, the former indirectly by reducing levodopa intake, the latter through direct effects. Repetitive transcranial magnetic stimulation has been shown to transiently improve LID.
