Parkinson's Disease | Why Do My Hands Shake and My Body Feel Stiff?

A resting tremor is an involuntary, rhythmic shaking that occurs when a muscle is relaxed and not in use. It is a hallmark symptom of Parkinson's Disease (PD) and typically begins in one limb, often a hand or finger. This is distinct from other types of tremors, such as an action tremor, which occurs during voluntary movement. The classic PD tremor is often described as a "pill-rolling" motion, where the thumb and forefinger move back and forth. The underlying cause is the dysfunction of the basal ganglia, a group of structures deep within the brain that control movement. The substantial loss of dopamine-producing neurons in this region disrupts the brain's ability to send smooth, controlled motor commands to the muscles. This disruption results in the characteristic shaking that is most apparent when the individual is at rest and may even subside when they initiate a purposeful action or during sleep. The tremor is a direct manifestation of the brain's struggle to regulate motor output without adequate dopamine, a key neurotransmitter responsible for coordinating movement.

Rigidity refers to a state of muscle stiffness or inflexibility. In individuals with Parkinson's, this manifests as resistance to passive movement. For example, if a clinician tries to bend the patient's arm, they will feel a consistent, "lead-pipe" like resistance throughout the motion. This stiffness can affect any part of the body, leading to a decreased range of motion and causing muscle aches and pain. Bradykinesia, on the other hand, means "slowness of movement." It is a fundamental impairment in both the planning and execution of motor tasks. This makes it difficult to initiate voluntary movements and causes the overall pace of actions to be significantly reduced. Simple, everyday tasks like buttoning a shirt or standing up from a chair become time-consuming and challenging. Both rigidity and bradykinesia are direct consequences of dopamine depletion in the basal ganglia, which impairs the brain's ability to facilitate smooth, rapid, and fluid movements.

The primary cause of resting tremor, rigidity, and bradykinesia in Parkinson's Disease is the progressive loss of dopamine-producing neurons in a specific area of the midbrain called the substantia nigra. Dopamine is a crucial neurotransmitter that acts as a chemical messenger, facilitating communication within the basal ganglia motor circuit. This circuit is responsible for selecting, initiating, and smoothing out voluntary movements. When these dopamine-producing cells degenerate, there is a significant dopamine deficit, leading to a breakdown in this communication pathway. The result is a dysfunctional motor control system that produces the characteristic symptoms of PD. The brain can no longer properly regulate muscle tone or execute movements efficiently.

No, the motor symptoms of Parkinson's Disease do not appear all at once. The onset is typically subtle and gradual, often starting on one side of the body (asymmetric onset). For instance, a mild tremor might begin in the fingers of one hand and remain the primary symptom for a considerable time. As the neurodegenerative process continues, the symptoms slowly worsen and eventually spread to involve the other side of the body. The progression rate and the specific sequence of symptoms vary significantly among individuals, but the gradual and asymmetric nature of the initial motor signs is a classic diagnostic feature of the disease.

Motor symptoms are the most visible signs, but they are not the only symptoms of Parkinson's Disease. The condition is also associated with a wide range of non-motor symptoms that can be equally, if not more, disabling. These symptoms arise because dopamine depletion and other neurochemical changes affect various brain functions beyond motor control. Common non-motor symptoms include a reduced or lost sense of smell (hyposmia), sleep disturbances such as REM sleep behavior disorder (acting out dreams), constipation, and mood disorders like depression and anxiety. Cognitive changes, including problems with attention, planning, and eventually dementia, can also occur, particularly in the later stages of the disease. Recognizing these non-motor symptoms is critical for a comprehensive understanding and management of Parkinson's, as they significantly impact the patient's quality of life.