Parkinson's disease: symptoms, causes, diagnosis and treatment

Parkinson's disease is best known for tremor, but it affects far more than movement. It usually develops slowly, and many people respond well to treatment. This review explains the symptoms, causes, diagnosis and care of Parkinson's disease, using information from the NHS, the World Health Organization (WHO) and the US National Institute of Neurological Disorders and Stroke (NINDS).

1. Introduction

Parkinson's disease is a long-term condition in which parts of the brain become progressively damaged over many years, so symptoms gradually worsen ^[1]. WHO describes it as a progressive brain condition that affects movement, mental health, sleep and pain, and notes it cannot currently be fully reversed, although medicines, surgery and rehabilitation can reduce symptoms ^[2]. WHO estimated that more than 8.5 million people were affected in 2019, and that the number has doubled over 25 years ^[2].

2. Signs and symptoms

The NHS names three main symptoms: involuntary shaking called tremor, slowed movement and stiff, inflexible muscles ^[1]. NINDS describes tremor as often starting in one hand, rigidity as muscle stiffness, bradykinesia as slowed movement, and postural instability as balance problems that raise the risk of falls. Walking may change, with a stooped posture, reduced arm swing and small shuffling steps ^[3]. Symptoms often start on one side of the body and usually reach both sides later ^[3].

Non-movement symptoms are also common ^{[1, 2, 3]}:

• Low mood and anxiety, which can appear early
• Sleep problems, including insomnia
• Loss of sense of smell
• Memory and thinking changes, and possible dementia
• Swallowing, speech, bladder and digestive problems
• Pain and tiredness

3. Causes and risk factors

The NHS explains that nerve cells in a brain area called the substantia nigra are lost, which lowers dopamine, a chemical that helps control movement. The reason for this loss is unclear, and experts believe genetic and environmental factors combine ^[1]. NINDS says that in most cases the cause is unknown, and that clumps of a protein called alpha-synuclein are found in many affected cells ^[3].

Known risk factors include older age (average onset is in the early to mid-60s), male sex, a family history and exposure to certain pesticides and pollutants ^{[2, 3]}. The NHS notes that most people develop symptoms after age 50, though some develop them before 40 ^[1].

4. Diagnosis and tests

No single test confirms Parkinson's disease. NINDS says diagnosis relies on medical history, a neurological examination and ruling out other conditions, and that blood tests and scans may be used to exclude other disorders ^[3]. WHO says it is diagnosed clinically, meaning from a doctor's assessment of symptoms ^[2]. Genetic testing with counselling is available for inherited forms ^[3]. The NHS advises seeing a doctor if you think you may have symptoms, who may refer you to a specialist ^[1].

5. Treatment and management

Treatment is chosen and adjusted by your doctor. The NHS says treatments can reduce the main symptoms and help maintain quality of life, and may include physiotherapy, occupational therapy, medicines and, in some cases, brain surgery. Early symptoms are often mild, so treatment may not be needed at first, but regular specialist check-ups are usually advised ^[1].

• Medicines: both WHO and NINDS describe a dopamine-raising medicine as the most effective main therapy for movement symptoms. Other medicine groups act like dopamine, slow its breakdown or change other brain chemicals ^[3]. Some medicines can cause side effects such as sleepiness or low blood pressure, so regular monitoring matters, and the main medicine should not be stopped suddenly ^[3].
• Deep brain stimulation: a surgical option considered when medicines stop working well. It helps movement symptoms but not every symptom ^[3].
• Therapy: physical, occupational and speech therapy support daily life. WHO describes strength, walking and balance training as improving function and quality of life ^{[2, 3]}.

Because Parkinson's disease affects many body systems, care usually involves a team. The NHS notes that support is available for people who need help with daily life and for those who care for someone with the condition ^[1]. WHO points out that myths, such as the idea that the condition is contagious, can get in the way of care, and that it is not contagious ^[2].

6. Exercise, diet and self-care

NINDS says regular activity such as walking, dancing, yoga, cycling and swimming can improve flexibility, balance, strength and mobility, and that people should check with a doctor before starting a new programme. A fibre-rich diet and enough fluids can help with constipation. Too much protein may reduce how well the main medicine is absorbed, so discuss meals with your care team ^[3].

Many people respond well to treatment and have only mild to moderate disability, and most now have a normal or near-normal life expectancy ^[1]. Family and friends who provide care need support too ^[2].

7. When to see a doctor

See a doctor if you notice tremor, stiffness, slowness or balance problems that are new or worsening ^[1]. NINDS describes falls, hallucinations, confusion and trouble swallowing as problems that can occur in Parkinson's disease or as effects of its medicines ^[3], so tell your care team if they happen.

In an emergency, call your local emergency number (112 in India, 911 in the United States).

8. Conclusion

Parkinson's disease is a progressive condition that affects movement and many other body functions, and its cause is mostly unknown. Early assessment, a team approach with medicines, therapy and exercise, and regular reviews can help people keep independence and quality of life. Your own doctor decides the treatment plan.