What type of muscle tone is characterized by a "lead pipe" rigidity?

"Lead pipe" rigidity is a type of rigidity that is characterized by increased muscle tone where the resistance to passive movement is constant throughout the range of motion, resembling the firmness of a lead pipe. This condition is often observed in patients with certain neurological disorders, particularly those associated with basal ganglia dysfunction, such as Parkinson's disease.

Unlike spasticity, which involves a velocity-dependent increase in muscle tone and may result in a "clasp-knife" phenomenon, lead pipe rigidity maintains consistent resistance regardless of the speed of movement. Additionally, flaccidity refers to an absence of muscle tone, leading to weakness and lack of resistance, while hypotonia indicates a reduced muscle tone, neither of which can be described as "lead pipe." Rigidity, in this context, refers specifically to the stiffness without any fluctuating resistance, which aligns perfectly with the characteristics of lead pipe rigidity.