Clasp-knife

Clasp-knife response is a medical term used to describe a type of muscle spasticity in which a muscle initially resists movement, but then gives way. It is one of the characteristic symptoms of spasticity, a condition often associated with neurological disorders such as multiple sclerosis, cerebral palsy, and stroke.

Overview

The clasp-knife response is named for its similarity to the action of a clasp knife, which resists initial pressure when closing but then snaps shut. In the same way, a muscle with clasp-knife spasticity resists initial movement but then suddenly relaxes, allowing the movement to continue.

This response is caused by an imbalance in the nervous system's control of muscle tension. Normally, the brain and spinal cord work together to maintain a balance between muscle contraction and relaxation. In conditions that cause spasticity, this balance is disrupted, leading to increased muscle tension and abnormal reflexes.

Causes

Clasp-knife spasticity is most commonly associated with conditions that damage the upper motor neurons, the nerve cells that carry signals from the brain to the spinal cord. These conditions include:

• Multiple sclerosis, a disease that damages the protective covering of nerve fibers in the brain and spinal cord
• Cerebral palsy, a group of disorders that affect a person's ability to move and maintain balance and posture
• Stroke, a condition that occurs when the blood supply to part of the brain is interrupted or reduced

Treatment

Treatment for clasp-knife spasticity typically involves a combination of physical therapy, occupational therapy, and medication. Physical and occupational therapy can help improve muscle strength and coordination, while medication can help reduce muscle stiffness and improve movement.

Medications used to treat spasticity include baclofen, diazepam, and tizanidine. In severe cases, surgery may be considered to relieve muscle stiffness and improve function.

See also

• Spasticity
• Upper motor neuron syndrome
• Hypertonia

Clasp-knife Resources
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