What condition is characterized by rigidity with little jerks when muscles are stretched?

The condition characterized by rigidity with little jerks when muscles are stretched is known as cogwheel rigidity. This type of rigidity is often associated with neurological conditions, particularly Parkinson's disease. In cogwheel rigidity, when the examiner attempts to passively move the affected limb, the patient exhibits resistance that feels like a series of catches or jerks, resembling the movement of a cogwheel.

This phenomenon occurs due to a combination of muscle rigidity and intermittent relaxation of the muscles, resulting from the underlying dysfunction of the basal ganglia in the brain. The resulting movements are not smooth but rather exhibit a stop-and-go quality as the muscles respond to stretching.

Understanding cogwheel rigidity is crucial for clinical assessment as it helps differentiate it from other forms of muscle tone abnormalities and provides insights into the motor control issues associated with certain neurological conditions.