Parkinson's disease: understanding the motor and non-motor symptoms

What is Parkinson's disease? 

According to Parkinson's Foundation, about 90,000 Americans are diagnosed with Parkinson's disease every year. On average, almost one in two sufferers is diagnosed at the age of 58. 

Worldwide, 5 million people are affected by this condition, and this figure will very likely double by 2030.

The cause of Parkinson's disease is unknown, but the risk of developing it is higher in people with a family history of the disease.

There are various treatment options, including medication, dietary supplements, surgery, physical rehabilitation and others, that can reduce the symptoms of Parkinson's disease.

Parkinson's disease develops 5 to 10 years before the first clinical signs appear. In general, these first signs are non-motor symptoms (NMS). Then, gradually, the first motor symptoms appear, but only when 50-70% of the dopamine neurons have already been destroyed and the brain is no longer able to compensate.

When motor symptoms appear, they fluctuate and initially affect only one side of the body. They then become bilateral, but always remain asymmetric, i.e. more pronounced on one side than the other.

What are the motor symptoms of Parkinson's disease? 

The motor symptoms of Parkinson's disease are often the most obvious and the first to be noticed. 

One of the characteristic symptoms of Parkinson's disease is tremor, which generally occurs at rest and diminishes with movement. Muscle stiffness (caused by hypertonia), often responsible for a forward-bending (stooping) posture, and slowness of movement, known as bradykinesia, are also some of the most common signs.

Other motor symptoms include: 

• Dyskinesia, involuntary movements and/or difficulty coordinating movements,
  
• Akinesia, difficulty initiating movement, 
  
• Dystonia, a sustained or repetitive painful muscle contraction (spasms or cramps), 
  
• Freezing, a walking disorder characterized by sudden, brief and unpredictable immobility, preventing forward movement, 
  
• Postural instability and loss of balance, linked to muscular rigidity and akinesia, 
  
• Dysarthria, a motor speech disorder caused by muscle weakness, 
  
• Dysphagia, taking longer to eat a meal or coughing at mealtimes, with the risk of false routes,
  
• Sialorrhea, difficulty controlling saliva, 
  
• Micrographia, increasingly small and difficult handwriting.
  

People suffering from these motor symptoms of Parkinson's disease may find it difficult to carry out simple daily tasks, which has a considerable impact on their quality of life.

What are the non-motor symptoms (NMS) of Parkinson's disease?   

The invisible non-motor symptoms (NMS) represent the hidden face of Parkinson's disease. These symptoms are sometimes neglected, but they can actually have a significant impact on patients' daily lives.

Such symptoms include: 

• Chronic fatigue,
  
• Hyposmia or anosmia, corresponding to the partial or total loss of the sense of smell, 
  
• Hypophonia, weakening of the volume of the voice,
  
• Hypomimia, reduction and slowing down of the expressive movements that accompany emotions, 
  
• Orthostatic hypotension, a significant drop in blood pressure when the person rises from a lying or sitting position, which can lead to dizziness or even loss of consciousness and thus the risk of falling.
  

Other categories of non-motor disorders include:

Sleep disorders 

These disorders are associated with psychological factors such as anxiety and depression, and sensory-motor factors such as akinesia and dystonia. 

The most common sleep disorders are insomnia and/or daytime sleepiness.

Genitourinary disorders 

Parkinson's disease can lead to bladder dysfunction, which may include nocturia (waking up more than twice a night to go to the toilet), urinary urgency (a sudden and irrepressible need to urinate), pollakiuria (an abnormally high frequency of infrequent urination) and urinary incontinence (involuntary leakage of urine).

Sexual dysfunction may also be present: erectile dysfunction in men and vaginismus and dyspareunia (pain during intercourse) in women.

Thermoregulation disorders

Parkinson's disease disrupts the function of the hypothalamus and the autonomic nervous system, resulting in poor analysis of outside temperature and problems with sweating.

Digestive disorders

Constipation, gastroparesis (slow emptying of the stomach), dysphagia, irritable bowel syndrome (IBS) and swallowing disorders are among the non-motor symptoms (NMS) of Parkinson's disease.

Recent studies suggest that digestive disorders are early signs of Parkinson's disease.

Pain and sensory disorders 

Pain is often present from the onset of Parkinson's disease and is a pervasive symptom, with 70% of patients complaining of chronic pain. 

This pain can be linked to rigidity and akinesia. It may be rheumatic, muscular (cramps, muscle contractions), tendon or joint pain, as well as spinal pain or sciatica. Patients report numbness, tingling, burning and shooting pains. They also present an altered perception of pain.

Mental problems 

Depression, anxiety, irritability and apathy (lack of motivation) are the most common mental disorders associated with Parkinson's disease.

There are also ICDs (impulse control disorders) and addictive behaviors. The latter are caused by the damage to dopaminergic circuits caused by Parkinson's disease and exacerbated by certain treatments. These disorders are characterized by persistent, uncontrollable thoughts or impulses. ICDs may include pathological gambling, hypersexuality, compulsive shopping or bulimia. 

At an advanced stage, people with Parkinson's disease may suffer from psychosis. 

Cognitive disorders

In the early stages of the disease, cognitive disorders are mild and have little impact on daily life. They include difficulty concentrating, slow thinking, difficulty recalling certain memories or difficulty organizing a number of everyday tasks. 

In some cases, cognitive problems are more severe and lead to loss of independence in managing daily activities: this is known as Parkinson's dementia.


It should be noted that all these non-motor symptoms can be either the consequences of the disease itself, or caused (or aggravated) by the drugs used to treat it.

Conclusion

Parkinson's disease is a chronic neurodegenerative condition which progresses rather slowly.

Every person's patient journey with Parkinson's disease is unique. The nature, intensity and evolution of the various symptoms caused by the disease depend on the patient.

For this reason, a thorough understanding of the motor and non-motor symptoms of Parkinson's disease is crucial for providing appropriate support to those affected.