Clasp-knife response

Clasp-knife response (pronunciation: /klasp naɪf rɪˈspɒns/) is a medical term used to describe a specific type of muscle reaction in certain neurological conditions.

Etymology

The term "clasp-knife response" is derived from the action of a clasp-knife, a type of folding knife that snaps shut when closing, similar to the sudden resistance followed by relaxation observed in this type of muscle response.

Definition

The clasp-knife response is a type of muscle spasticity where there is resistance to movement of a joint, similar to the action of a clasp-knife being closed. This resistance suddenly decreases when the joint has been moved past a certain point. This response is often seen in conditions such as cerebral palsy, multiple sclerosis, and stroke.

Related Terms

Spasticity: A condition in which certain muscles are continuously contracted. This contraction causes stiffness or tightness of the muscles and can interfere with normal movement, speech, and gait.
Hyperreflexia: A condition characterized by overactive or overresponsive reflexes. Examples of this can include twitching or spastic tendencies, which are indicative of upper motor neuron disease as well as the lessening or loss of control ordinarily exerted by higher brain centers of lower neural pathways (disinhibition).
Upper motor neuron: A motor neuron located in the central nervous system that projects its axon outside the central nervous system and directly or indirectly controls muscles.
Cerebral palsy: A group of permanent movement disorders that appear in early childhood. Signs and symptoms vary among people and over time.
Multiple sclerosis: A demyelinating disease in which the insulating covers of nerve cells in the brain and spinal cord are damaged.
Stroke: A medical condition in which poor blood flow to the brain results in cell death.