EMOTIONAL AND COGNITIVE ABNORMALITIES IN PATIENTS AFFECTED BY FUNCTIONAL MOTOR SYMPTOMS: TOWARDS A BIOLOGICAL MARKER

INTRODUCTION: Functional motor symptoms (FMS) encompass weakness and movement disorders (e.g. tremor, ballism, gait disturbances, dystonia or tic) that are genuine but are not due to an organic cause. According to the recent edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), they are part of the wide spectrum of Conversion Disorders (Functional Neurological Symptom Disorders), which also include non-epileptic seizures and functional sensory disturbances. Although their high prevalence, aetiological mechanisms underlying FMS are still unknown. AIMS: Aim of this thesis was to determine a possible biological marker for FMS. To this aim, I first examined the role of emotional and cognitive abnormalities in patients affected by FMS. In particular, I aimed to explore: 1. the prevalence of alexithymia; 2. the degree of interoceptive awareness; 3. the deception ability (as a measure of mild multifacet cognitive impairment); 4. the neuromodulatory effect of a single anodic Transcranial Direct-Current Stimulation (tDCS) on interoceptive sensitivity and on spatial attention in a sample of patients affected by FMS and in a sample of healthy subjects served as a control group. Second, I aimed to explore the level of various brain metabolites (N-Acetyl-aspartate - a neuronal marker, creatine - an energy buffer and shuttle, myo-inositol - a glial cell marker, choline - involved in cell membrane synthesis and degradation and the sum of glutamate - the major excitatory neurotransmitter - and glutamine) in the anterior cingulate cortex (ACC)/medial prefrontal cortex (mPFC) and in the occipital cortex (OCC) (control region), using magnetic resonance spectroscopy as neuroimaging technique, in a group of patients with FMS and in a group of healthy controls. MATERIALS & METHODS: For each part of the study, I enrolled a number of patients with FMS and a number of age and gender-matched healthy controls. Methods included: rating scales for the assessment of psychological variables (alexithymia, depression, anxiety, personality disorders, self-objectification, quality of life), the heart beat detection task for the assessment of interoceptive awareness, the guilty knowledge task (GKT) to detect the deception ability and the Posner paradigm to detect the spatial attention. A single anodic tDCS session over the right posterior parietal cortex was used to assess the neuromodulatory effect. To explore the level of various brain metabolites I used magnetic resonance spectroscopy. RESULTS: My results showed that patients with FMS have: 1. significantly higher level of alexithymia than healthy controls; 2. significantly lower degree of interoceptive awareness than healthy controls; 3. significantly longer reaction times at the GKT than healthy controls. I also showed that there was a significant difference between the levels of interoceptive awareness after real and sham tDCS stimulation in the whole group of participants. When considering the two groups separately, this difference still remained significance only in patients with FMS. Finally, a significant increase in glutamate+glutamine/creatine was found in the ACC/mPFC but not the OCC in patients with FMS. CONCLUSION: My results contribute to the understanding of the aetiopathogenesis of functional motor symptoms, opening a novel window for future research and possibly novel treatments.