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The signs and symptoms Parkinson disease causes in large part define what the disease is. Since there is no specific test for it, the diagnosis rests on these clinical features and the response of some of them to treatment.
Parkinson disease (PD) is the second most common chronic neurodegenerative disease. Only Alzheimer’s disease is more common. PD is the most common movement disorder. Like some other diseases named after a person, the name may or may not be apostrophized. The public is accustomed to the name with the apostrophe s. But in recent years medical scholars have preferred omitting the punctuation of linguistic ownership. Parkinson’s disease and Parkinson disease are both correct terms that refer to the same disorder.
Understanding PD involves some knowledge of basal ganglia (nuclei in deep portions of the brain and brainstem) and their function. There are three types. One type receives signals from various sources in the brain. They are input nuclei. Another type sends signals to a region of the brain just beneath the cerebrum known as the thalamus. They are output nuclei. After processing the data the thalamus in turn relays the signals to the cerebrum. The third type relays signals between input and output nuclei. They are intrinsic nuclei. The signaling to, from and between basal ganglia is by means of the release of various neurotransmitters.
PD is primarily a disease of an intrinsic nucleus basal ganglion in the midbrain known as the substantia nigra (SN). There is one on the right side of the midbrain and one on the left side of the midbrain. Each has two parts. The part affected by PD produces the neurotransmitter dopamine which regulates body movements including coordination and balance. As best we know to date, there are two types of pathology in this structure when PD is present. The type that is most recognized and understood is the death and loss of cells that produce dopamine. A less understood finding that autopsies on some patients with PD have shown is the presence of Lewy bodies in the SN. Lewy bodies are abnormal aggregates of a specific protein that form inside nerve cells. To date it is unclear though whether Lewy bodies are a cause or effect, or what role, if any, they play in PD.
The SN has functions other than motor ones but they are less well-understood. They include the following:
- Regulating mood
- Processing of information in the brainstem reward center
Signs and symptoms of Parkinson disease
Sorting the signs and symptoms Parkinson disease causes is a practical approach for learning many of them as opposed to rote. A reasonable assortment scheme is one based on:
- Cardinal signs and symptoms for making a diagnosis – tremor, rigidity, bradykinesia, and postural instability (impaired balance)
- Type of nervous system dysfunction
- Non-motor → autonomic, cognitive, emotional and other
- Early signs and symptoms
Cardinal signs and symptoms for diagnosis
The rest tremor of Parkinson disease usually begins in an upper extremity (limb) and is asymmetric. That means it starts out on one side or even when it is bilateral it is more obvious on one side than the other.
Postural instability (balance impairment) is often included as the fourth main sign and symptom of PD but is not one of the criteria for making the diagnosis.
Motor signs and symptoms of Parkinson disease
Motor signs and symptoms of Parkinson disease are those having to do with voluntary or involuntary movement, skeletal muscle tone, balance and gait. Motor symptoms generally don’t appear until roughly 60%-80% of the dopamine-producing cells in the SN are lost. They include the cardinal signs and symptoms listed above and others.
Other motor signs and symptoms Parkinson disease can cause other than the cardinal ones already mentioned include the following:
- Masked facies – reduced facial expression due to decreased function of the related muscles in the face
- Decreased arm swing on the first-affected side during walking due to rigidity
- Stooped posture due to rigidity, brain-mediated impairment of one’s proprioceptive reflex, and other factors not well understood (pain might be a factor)
- Parkinsonian gait – might have any or a combination of the following features:
- Shuffling gait – steps are shorter than normal (choppy) with dragging of the feet due to the heel or entire sole striking during forward foot movement; arm swing (usually on one side) during walking is reduced; stooped posture (trunk and head tilted forward) while walking
- Festinating gait – short choppy steps with an involuntary increase in the speed of walking; head, and trunk are flexed but stiff; legs are flexed at the knees and hips but stiff
- Other non-specific – walking is unsteady; slowness of movement; movement freezing; difficulty initiating or terminating walking; difficulty making turns while walking; trembling of the head ± extremities during walking
- Freezing of movements during activities other than walking
- A subtle decrease in manual dexterity
- Micrographia – a decrease in the size of one’s handwriting; it might progress
- Various speech problems due to abnormal contractions of the muscles of the pharynx (throat), larynx (voice box), palate (roof of the mouth), and/or tongue; speech signs and symptoms might be any or a combination of the following:
- Soft voice with inability to speak loudly – usually the first speech change to occur
- Monotone voice
- Slurred speech
- Voice fading with continuous talking
- Fast speech without appropriate pauses between words and sentences
- Hesitation in initiating speaking
- Coarse or tremulous voice ± indistinct word articulation
- Uncontrolled repetition of words or phrases while speaking
- Dysphagia (trouble swallowing) due to abnormal contractions of throat muscles
Nonmotor signs and symptoms of Parkinson disease
In recent years it has become evident that PD is not a disease that affects just motor function. It also affects various other bodily functions that require precise integration of signals between structures within and outside of the brain. Faulty processing of these signals pertaining to involuntary functions of the nervous system leads to related signs and symptoms. The categories of nonmotor signs and symptoms that Parkinson disease can cause are autonomic, cognitive, emotional and other.
Autonomic signs and symptoms
- Orthostatic hypotension
- Nocturia; urinary frequency; or urinary hesitancy due to a hyperactive bladder
- Delayed bladder emptying; or difficulty starting urination due to a hypoactive bladder
- Excessive sweating
- Heat or cold intolerance due to impaired thermoregulation (regulation of body temperature by the brain)
- Increased saliva production
- Dandruff due to an oily scalp caused by excessive production of sebum by sebaceous glands
Cognitive signs and symptoms
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- Bradyphrenia – Slow thinking and processing of information
- Changes in memory, concentration and judgment ± other cognitive symptoms, which if severe enough to interfere with activities of daily living, are indicative of Parkinson disease dementia which develops in 50% to 80% of individuals that have had Parkinson’s disease for ten or more years
Emotional signs and symptoms
The emotional signs and symptoms of Parkinson disease can be a part of, or they can be separate from cognitive ones. They include:
- Mood or personality change
- Delusions, hallucinations, agitation or mania which usually occur only with certain medications used to treat PD
Other signs and symptoms
There are other signs and symptoms that don’t fit precisely in either of the above categories because their mechanisms might be unclear or multifaceted. They include any or a combination of the following:
- Sexual dysfunction – erectile dysfunction in men; vaginal dryness in women; decreased libido (sex drive) in men and women; impaired mechanics due to other symptoms previously discussed
- Loss of smell – may range from mild to marked
- Sleep problems
- Drooling – mechanism not totally clear but might be due to increased saliva production, which is known to occur, and pooling of secretions caused by swallowing difficulties
Early signs and symptoms of Parkinson disease
The clinical features of PD vary between persons, but in general amongst the ones previously listed there are certain signs and symptoms Parkinson’s disease causes early on in the course of the disease. They are the following:
- Loss of smell – often precedes motor signs and symptoms; a few studies suggest it might be a predictor of PD
- A subtle decrease in manual dexterity
- Trouble sleeping
- Slow movement
- Small writing
- Voice change
- Change in gait, particularly reduced arm swing on the side first affected
- Trouble moving or walking due to stiffness
- Masked face
- Posture change
- Constipation and other symptoms of autonomic dysfunction
- Lightheadedness or fainting
- Dystonia – can be an early symptom if PD is diagnosed before the age of 40