Parkinson’s disease

Parkinson’s disease is a complex and often misunderstood condition, with symptoms that can range from subtle to life-altering. It’s easy to confuse the occasional shaking from nervousness with something more serious, but in Parkinson’s disease, the loss of control over movement happens gradually and persistently.

Thankfully, with early diagnosis and proper management, you can greatly improve yours or your loved one’s quality of life.

What is Parkinson’s disease?

Parkinson’s disease is a progressive neurological disorder that commonly affects the substantia nigra in the brain, or the centre that controls balance and movement [1]. This part or the brain is responsible for producing dopamine, which influences movement. When dopamine levels decline, patients may experience movement-related symptoms.

The common first sign of Parkinson’s is tremor of the limbs or the jaw. Stiffness is also a common early indicator of Parkinson’s disease.

Signs and symptoms of Parkinson’s disease

Symptoms of Parkinson’s disease can be classified to movement related symptoms, and non-movement related symptoms [1].

Movement-related symptoms (motor symptoms):

Tremors — This usually appears as trembling or shivering of the limbs while at rest, and can occur in the hands, feet, arms, legs, head, or jaw.
Bradykinesia — This refers to slowed movement, for example it may take longer for you to button your shirt, your arms may not swing when you walk.
Rigidity or muscle stiffness — Patients may feel that their muscles are tense and painful, and movements may appear jerky.
Problems with balance and coordination – Some patients also present poor or unstable posture, sometimes presenting an abnormal, or shuffling gait. Poor balance and coordination can also lead to falls.
Speech impairment – Slurred or slowed speech is common in Parkinson’s disease patients.
Loss of control of facial muscles – Trouble with facial expressions, sometimes referred as “masked face” or hypomimia, drooling, blinking less.
Dysphagia – Difficulty swallowing.

Signs and symptoms of Parkinson’s disease — Motor symptoms of Parkinson’s disease include tremors, slow movement, rigidity, and poor balance or coordination.

Non-movement related symptoms (non-motor symptoms):

Constipation or gastrointestinal problems
Urinary incontinence
Depression
Loss of smell
Sleep changes (Rapid eye movement sleep behaviour disorder) [3]
Dementia

In some cases, non-motor symptoms such as loss of smell, sleep disturbances, and constipation come before the motor symptoms manifest [1, 3, 4].

What causes Parkinson’s disease?

The exact cause of Parkinson’s disease is still undetermined, but researchers believe that it may be due to both genetic and environmental factors, such as:

Loss of dopamine-producing neurons — Damage and death of dopamine-producing neurons lead to the loss of connection between the central nervous system and muscles required to control movement.
Genetic predisposition — Genetic mutations in genes such as SNCA, LRRK2, PRKN, and PINK1 can lead to pathologic changes or features observed in Parkinson’s disease.
Environmental factors — Toxic exposure to copper, manganese, pesticides, or pollutants can lead to lesions in the basal ganglia, where the substantia nigra is located [5].
Age — Old age is the biggest risk factor in Parkinson’s disease. This is likely when the pathological effects of Parkinson’s disease start to take effect.
Oxidative stress — Accumulation of oxidised dopamine can lead to other factors such as mitochondrial dysfunction and protein aggregates [6].
Mitochondrial dysfunction — Mitochondria are important energy resources for synaptic transmission, hence damage to mitochondria can impair synaptic function [7].
Protein misfolding and aggregation — Aggregates of abnormal alpha-synuclein protein can lead to death of neurons in the brain.
Medications — Dopamine-blocking medications such as antipsychotics, metoclopramide, prochlorperazine, can lead to drug-induced parkinsonism [8]
Head trauma — Traumatic head injuries may damage parts of the brain.

Dopamine-producing neurons are damaged in Parkinson’s disease. — Damage to the neurons in the substantia nigra causes gradual loss of movement control.

Some cases of Parkinson’s disease are idiopathic, meaning that the disease happened on its own with no clear cause. That said, issues with the dopamine-producing neurons are at the core of this condition.

Who is at risk of Parkinson’s disease?

Researchers have identified the following to be risk factors of Parkinson’s disease:

Age — The risk of Parkinson’s disease increases as we get older. Onset of Parkinson’s disease is usually seen at ages 50 to 70. When symptoms start to show at ages below 50 years, it is considered early onset Parkinson’s disease.
Genetics — Some genetic mutations inherited can indicate a higher risk of developing Parkinson’s disease, such as mutations of the LRRK2, PRKN or SNCA gene [3, 4]. Genetic mutations that are not inherited may also contribute to this; this can occur in sporadic cases (non-hereditary).
Gender — Men are more likely to develop Parkinson’s disease compared to women.
Environmental factors — Exposure to toxins, mould, herbicides, or pesticides may increase the risk of Parkinson’s disease [2].

Stages of Parkinson’s disease

Many doctors use the Hoehn and Yahr rating scale to identify and classify the disease progression of Parkinson’s disease. This scale consists of 5 stages that describe the severity of symptoms.

However, this scale only relies on observing motor symptoms. Many cases of Parkinson’s disease also exhibit non-motor symptoms, which are not described in the Hoehn and Yahr rating scale. Today, doctors are more likely to use the Movement Disorder Society – Unified Parkinson’s Disease Rating Scale (MDS-UPDRS).

The scale is broken down to 4 parts to describe the different aspects of how Parkinson’s disease affects the patient:

Part 1: Non-motor aspects of experiences of daily living — This part examines the non-motor parts of Parkinson’s disease symptoms, such as dementia, depression, bodily functions such as constipation and incontinence, fatigue, and pain.
Part 2: Motor aspects of experiences of daily living — This part examines the motor symptoms that the patient may experience, such as tremors, stiffness, and general motor symptoms. This part also addresses the patient’s ability to function in daily living activities such as the ability to speak, eat, or dress themselves.
Part 3: Motor examination — This section is important for the doctor to examine the patient’s motor abilities, including speaking, making facial expressions, walking, or keeping balance. It also covers other aspects such as tremors, muscle stiffness or rigidity, and bradykinesia.
Part 4: Motor complications — The doctor will use this section to determine how the symptoms of Parkinson’s disease impact the patient’s life, such as the amount of time the symptoms take each day, and whether daily activities are affected by these symptoms.

How is Parkinson’s disease diagnosed?

If you suspect yourself or a loved one of suffering from Parkinson’s disease, a visit to your doctor or healthcare provider is highly recommended. Early diagnosis can prepare you to manage or slow down its progression.

Your neurologist will take your medical history, symptoms, as well as information on family history of Parkinson’s disease. Your doctor will then perform a neurological and physical exam to determine your diagnosis.

Several other tests can be conducted as well:

Laboratory tests — Blood tests are usually used to rule out other conditions that may cause parkinsonism.
Imaging test — Computed tomography (CT) scan or magnetic resonance imaging (MRI) can be used to visualise the brain.
Genetic tests — Genetic testing can determine whether the cause of your symptoms can be contributed by genetic mutations, it is usually used when there is a family history of Parkinson’s disease, or if you have early onset Parkinson’s disease.
Spinal tap (lumbar puncture) — This test requires the neurologist to take samples of cerebrospinal fluid (CSF). This test is useful in identifying the presence of biomarkers such as alpha-synuclein aggregates.

Parkinson’s disease diagnosis in Singapore — Lumbar puncture or spinal tap can detect biomarkers of Parkinson’s disease

Is there a cure for Parkinson’s disease?

Unfortunately, there is no cure for Parkinson’s disease for now. However, treatment for Parkinson’s disease is available in the form of medication or surgery. Early treatment is key in proper management and slowing down the progression of symptoms.