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Grasp Reflex – Frontal Release Sign — SCE Neurology MCQ

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ModerateMovement DisordersGrasp Reflex – Frontal Release SignSCE Neurology

A 55-year-old man with known corticobasal syndrome has progressive left limb apraxia, cortical sensory loss, and rigidity. His right hand has developed involuntary grasping — when anything touches his right palm, his hand closes around it involuntarily and he cannot release it voluntarily. What is this sign called?

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Correct answer: B — Grasp reflex — a primitive reflex that re-emerges with frontal lobe damage, particularly supplementary motor area and prefrontal cortex; it reflects release of subcortical reflexes from cortical inhibition

The grasp reflex is a primitive reflex present in neonates that normally disappears as frontal cortical inhibition develops. Its re-emergence in adults indicates frontal lobe dysfunction (particularly medial frontal/SMA). It is elicited by stroking the palm or placing an object in the hand — the hand involuntarily closes and the patient cannot voluntarily release. It differs from alien limb (which involves complex, purposeful-appearing involuntary movements). Other frontal release signs include: palmomental reflex, glabellar tap (Myerson sign), snout reflex, and sucking reflex. A: Alien limb has complex purposeful movements. C: Myotonia is delayed muscle relaxation from channel dysfunction. D: Dystonia is sustained posturing. E: Spasticity catch is velocity-dependent increase in tone.

Reference: Clinical Neuroanatomy