Recognising motor impersistence at the bedside

Motor impersistence—the inability to sustain a voluntary motor action—is a subtle but clinically informative neurological sign. It is most commonly associated with right-hemisphere lesions involving the frontal and central regions but may also occur in callosal disconnection syndromes and neurodegenerative disorders such as Huntington’s disease. Bedside assessment is simple and uses tasks such as sustained eye closure, tongue protrusion or hand grip. Abnormalities found when using these tests raise the possibility of underlying structural or neurodegenerative disease and are believed to be specific to underlying attentional-intentional motor network dysfunction. However, sensitivity varies with technique and experience. Standardised protocols and quantitative tools, such as glossomotography to measure tongue protrusion force, can improve reliability and detection. Greater clinical awareness, supported by normative data and agreed diagnostic thresholds, would strengthen the clinical use of motor impersistence as a practical, accessible and revealing sign in the neurological assessment.