The “On-D Off” phenomenon The “On-D Off” phenomenon. Some patients experience fluctuations in symptoms late in the course of levodopa, independent of the time and dose of the drug, which can alternate several times throughout the day. The rate of change can be very rapid and unpredictable. Patients describe the changes as being like the power going on and off, so it is clinically referred to as the “On-D Off Phenomenon”. Heterokinesia”. It is a dance-like, twitchy or simple repetitive involuntary movements, commonly in the facial muscles, but also in the neck, back and limbs. The amplitude of such involuntary movements can be large, and in severe cases can affect the patient’s ability to perform daily activities. This phenomenon accounts for 15% of all drug users and is more frequent the younger the patient is. Involuntary movements Involuntary movements. Or abnormal movement, is the involuntary contraction of a part of the random muscle, a muscle or certain muscle groups. It is a skeletal muscle movement that the patient is aware of but cannot control on his or her own. Clinically common are muscle bundle tremors, muscle fiber tremors, spasms, twitches, myoclonus, tremor, choreiform movements, tardive dyskinesia, and torsional spasms. Muscle stiffness Muscle stiffness. It is the phenomenon of muscle tension, swelling, hardness, spasm (cramp), etc. Muscle tone Muscle tone. Simply put, it is the force generated by muscle cells pulling on each other. The tension of a muscle in a resting and relaxed state is called muscle tone. Myotonia is the basis for maintaining various postures and normal movements of the body, and is expressed in various forms. For example, when a person is at rest, the tension in the muscles of the body is called resting muscle tone. When the body is standing, although no significant muscle contraction, but the front and back of the body muscles also maintain a certain tension to maintain standing posture and body stability, known as postural muscle tone. The tension of the muscles during movement is called motor tone, which is an important factor to ensure continuous and smooth muscle movement (no trembling, jerking, spasm). Tremor Tremor. Two general meanings, one is tremor, also refers to a disease name, a rhythmic, alternating oscillatory action, caused by the repetitive type of muscle contraction and relaxation; the second is vibration, such as gunfire, trembling the earth. Tonicity Tonicity. It is muscle stiffness, resulting in stiffness of the limbs, neck, facial muscles, limb movement with effort, heaviness and weakness, facial expression stiffness and reduced blinking action, resulting in “mask face”, body bending forward, walking, turning neck and turning movements are particularly slow and difficult. When walking, the upper limbs lose their coordinated swinging action and the stride length is shortened. In combination with the flexed posture, the patient can walk with a broken gait and forward movement, which we call “panic gait”.