Parkinson's disease (PD) is a movement disorder that is chronic and progressive, meaning that symptoms continue and worsen over time. PD affects nerve cells in a part of the brain that controls muscle movement.
PD occurs when a group of cells in an area of the brain called the substantia nigra begin to malfunction and die. The cells in the substantia nigra produce a chemical called dopamine. Dopamine is a neurotransmitter, or chemical messenger, that sends information to the parts of the brain that control movement and coordination. When an individual has PD, their dopamine-producing cells begin to die and the amount of dopamine produced in the brain decreases. Messages from the brain telling the body how and when to move are therefore delivered more slowly, leaving a person incapable of initiating and controlling movements in a normal way.
PD is the most common form of parkinsonism. Parkinsonism is a group of movement disorders that have similar features and symptoms. When the cause of PD is unknown, it is called idiopathic Parkinson's disease.
The four primary symptoms of PD are tremor, or trembling in hands, arms, legs, jaw, and face; rigidity, or stiffness of the limbs and trunk; bradykinesia, or slowness of movement; and postural instability, or impaired balance and coordination (parkinsonian gait). As these symptoms become more severe, patients may have difficulty walking, talking, or completing other simple tasks.
Early symptoms of PD are subtle and occur gradually. In some people, the disease progresses more quickly than in others. As the disease progresses, the shaking, or tremor, which affects the majority of PD patients may begin to interfere with daily activities. Other symptoms may include depression and other emotional changes; difficulty in swallowing, chewing, and speaking; urinary problems or constipation; skin problems; and sleep disruptions.
PD usually affects people over the age of 50. According to the National Institute of Neurological Disorders and Stroke (NINDS), at least 500,000 people in the United States are estimated to have Parkinson's disease, and about 50,000 new diagnoses are made each year. The disorder occurs in all races but is somewhat more prevalent among Caucasians. Men are affected slightly more often than women.
Symptoms of PD may appear at any age, but the average age of onset is 60. It is rare in people younger than 30 and risk increases with age. It is estimated that 5-10% of patients experience symptoms before the age of 40.
Currently, there is a lack of blood or laboratory tests that have been proven to help in diagnosing PD. Therefore, the diagnosis is based on medical history and a neurological examination. The disease can be difficult to diagnose accurately. Doctors may sometimes request brain scans or laboratory tests in order to rule out other diseases.
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