Parkinson’s disease (PD) is characterized by the primary motor symptoms of tremor, rigidity, postural instability (impaired balance), and bradykinesia (slowing down and loss of spontaneous movement). Not everyone with PD experiences the same symptoms, or to the same severity. There are a number of secondary motor symptoms it may cause as well, such as changes to gait (way of walking), micrographia (small, cramped handwriting), mask-like expression, and speech changes. In addition, other secondary motor symptoms of PD include:
- Unwanted accelerations
- Stooped posture
- Dystonia
- Impaired fine motor dexterity
- Poverty of movement
- Akathisia
- Difficulty swallowing
- Cramping
- Sexual dysfunction1,2
Unwanted accelerations
In contrast to the slower movements seen with bradykinesia, some people with PD experience unwanted accelerations, movements or speech that is faster than expected. When someone with PD experiences unwanted accelerations in speech, it is called tachyphemia. Tachyphemia, also known as cluttering, is characterized by an excessively fast speed of talking and a rapid stammering that makes it difficult to understand the person speaking. Unwanted accelerations in walking is called festination. Festination, or festinating gait, is a quickening and shortening of normal strides. While the steps are quicker, the stride is shorter, causing this to be a very inefficient gait, which can be frustrating and tiring for the person experiencing it. Festination also increases the risk of falling.1,3,4
Stooped posture
The stooped or hunched over posture that many people with PD experience is sometimes called the “Parkinson’s posture.” The body leans forward and the head may be slightly turned down. The person may be bent to one side. It is not fully understood why this occurs but may be due to rigidity, parts of the brain that control posture, or dystonia. The stooped posture can further impair walking, which may already be compromised by PD.5
Dystonia
Dystonia is distinguished by prolonged muscle contractions that can cause twisting of body parts or repetitive movement. Dystonia is often painful, and it is caused by the damage to the area of the brain known as the basal ganglia. Dystonia may affect the arms, hands, legs, feet, neck, eyes, vocal cords, swallowing muscles, face, or jaw.1
Impaired fine motor dexterity
Along with the major motor systems that may be affected with PD, some people also experience impaired fine motor dexterity, causing difficulty with precise hand and finger movement. Impaired fine motor dexterity can impact activities such as in writing, sewing, or fastening buttons.1
Poverty of movement
Poverty of movement is the term used to describe a lack of natural, subtle movements like the decreased arm swing during walking that affects some people with PD.1
Akathisia
Akathisia is restless movement, which may appear as being jumpy or fidgety.1,6
Difficulty swallowing
Some people with PD have trouble swallowing, also known as dysphagia.1,4
Cramping
Cramping occurs when muscles may stay in a contracted position. Cramping frequently is the cause of pain in people with PD.1
Sexual dysfunction
People with PD may experience sexual dysfunction, including decreased sex drive, inability to orgasm, erectile dysfunction in men, decreased lubrication in women, or pain with intercourse in women.1,2
Why does Parkinson’s disease cause motor symptoms?
While the exact disease process is not fully understood, scientists do know that PD causes damage to the nerves in the brain and in the body. As the neurons in the body and brain die or become damaged with Lewy bodies (accumulation of the protein alpha-synuclein), the nerve cells cannot function properly. The damage to the dopamine-producing neurons in the substantia nigra produces the characteristic motor symptoms, including slowing of movement, muscular rigidity, and resting tremor, that are generally used to clinically diagnose PD. However, these symptoms are only a subset of the assorted motor, cognitive, affective, autonomic and sensory impairments that result from the degeneration of neurons in different areas of the central and peripheral nervous systems in PD. While characterized as a movement disorder, PD can also be described as a multisystem neurodegenerative disorder, as it damages the neurons in multiple areas of the body.7