Functional propriospinal myoclonus in Alzheimer's disease: coincidence or a new challenge?

Propriospinal myoclonus (PSM) is a rare hyperkinetic movement disorder characterized by involuntary and repetitive axial muscle contractions. Although traditionally classified as idiopathic or symptomatic, a functional etiology has often been described for PSM. Functional neurological disorders (FNDs), including functional PSM, are defined by symptoms inconsistent with other organic neurological conditions and often arise from brain circuit dysfunction affecting emotion processing, agency, attention, interoception, and predictive processing. Electrophysiological biomarkers such as Bereitschaftspotential (BP) and event-related desynchronization (ERD) offer diagnostic support, with ERD showing promise for functional PSM diagnosis. We report the first case of functional PSM in a 61-year-old woman with Alzheimer's Disease (AD). She presented with involuntary arrhythmic trunk movements, associated with anxiety and restlessness, resolving with distraction. Electrophysiological evaluation revealed ERD without BP, supporting a functional diagnosis. The coexistence of FMDs and neurodegenerative diseases like AD, though rare, underscores shared pathophysiological mechanisms, including disrupted agency and altered cortical processing. Treatment with Sertraline improved motor symptoms and anxiety, illustrating the importance of personalized management strategies in such cases. This report highlights the necessity for clinicians to recognize FMD in neurodegenerative diseases, promoting accurate diagnosis through biomarkers and integrated treatment approaches to improve patient outcomes. Further research is essential to refine diagnostic tools and therapeutic strategies for functional PSM in AD.