Functional sensory symptoms and signs: a case-control study of 102 patients

Despite being frequently reported by patients, the prevalence, character and clinical relevance of sensory symptoms in functional neurological disorder (FND) is unknown. This study aimed to (i) estimate the frequency and explore the characteristics of sensory symptoms and signs (excluding the special senses) in patients with motor-FND, (ii) compare these features to patients with recent stroke, and (iii) investigate potential mechanisms underlying functional sensory symptoms. In this prospective observational cohort study, 102 patients with motor-FND and 75 patients with recent stroke were assessed using structured clinical interviews, body maps, validated questionnaires, clinical assessment and quantitative sensory testing. Motor-FND participants were followed up at 12-months. Data were analysed using thematic analysis for symptom description, descriptive statistics for frequency and regression models to explore predictors of symptom severity and change. Sensory symptoms were highly prevalent in motor-FND, reported by 96% compared to 67% of mild to moderate recent stroke. However, 27% of motor-FND and 36% of stroke only endorsed experiencing sensory symptoms after prompting. Motor-FND participants described a broader spectrum of sensory experiences compared to stroke, including numbness, paraesthesia, movement-related perceptions and abstract descriptions. Feelings of limb absence/'feels dead' (19% versus 1%) and areas of complete sensory absence (27% versus 15%) were more commonly reported in individuals with FND than in mild-moderate stroke. The motor-FND group experienced pain more frequently than the stroke group (88% versus 41%) and more frequently endorsed having a high pain tolerance (70% versus 49%). The distribution of sensory symptoms differed from the distribution of pain. Sensory symptoms were often perceived as severe and associated with disability and depression. Conflation of the concepts of weakness and numbness was common in both groups (21% of motor-FND versus 10% of stroke). Only one-third of motor-FND patients reported improvement in sensory symptoms at 12 months. Dissociation, body perceptual disturbance and sensory hypersensitivity were significantly more common in motor-FND. Dense midline splitting of light touch or splitting of vibration sense across the forehead or sternum were uncommon and had poor diagnostic specificity, but asymmetries in vibration sense were more common in motor-FND. Quantitative sensory testing provided no clear added diagnostic value. Sensory symptoms in motor-FND vary in nature, are highly prevalent, persistent, clinically significant and often linked to broader illness burden and psychological distress. Sensory symptoms should be routinely assessed in FND, both for diagnosis and treatment planning. Future research should evaluate targeted interventions to specifically address sensory symptoms within multidisciplinary rehabilitation frameworks.