What is Parkinson’s Disease, Symptoms and Common Terms

Parkinson’s disease is a debilitating progressive illness which affects a person’s movement. Various parts of the body can be affected and symptoms such as stiffness in the muscles, difficulty when starting to move, slowness of movement and tremor in the hands at rest are part of the presentation. The disease was named after Dr James Parkinson who first diagnosed the disease in the 19th century.

Why does Parkinson’s disease happen?

The basal ganglia, a part of the brain affected by the disease, plays a vital role in the control of body movements. Cells in the substantia nigra, which is a part of the ganglia, produce a neurotransmitter (chemical messenger) known as dopamine. When someone is affected by Parkinson’s the dopamine-producing cells are lost and this then causes a shortage of dopamine in the brain. The reason why these cells die or are destroyed is unclear.

The basal ganglia in our brain stores dopamine and helps to adjust voluntary movement, similar to a steering mechanism. It works alongside another chemical messenger which is called acetylcholine. The level of dopamine in someone who has Parkinson’s will fall to about 80% and when this happens this steering mechanism in the brain will fail. The body’s internal communication system will then go awry and messages delivered from the brain to parts of the body are interrupted or slowed down and symptoms of Parkinson’s disease then begin to present.

The extent of the disease and parts of the body most affected will differ from person to person although the symptoms of the disease will always get progressively worse as it develops over a period of time. This is a very gradual progression that extends over months, years and decades.

How common is Parkinson’s disease?

Parkinson’s disease occurs throughout the world although as the disease chiefly affects older people. It is more prevalent in developed countries. Statistics show that roughly 1 in every 100 people older than 60 years of age has Parkinson’s disease. It affects about 120 out of every 100,000 people wordlwide and men are 1.5 times more likely to develop Parkinson’s disease than women.

What are the symptoms?

The number one symptom of Parkinson’s disease is how it affects the movement; other typical symptoms are mood disorders, changes in the behaviour, changes in the ways of thinking and changes in sensation. Symptoms  can vary from person to person and with the individual progression of the disease.

There are four major diagnostic symptoms of the disease, these are:

  • Tremor or shaking particularly when the limbs are at rest.
  • Rigidity or stiffness of the joints which can sometimes be very painful.
  • Bradykinesia or slowness of movement.
  • Postural instability.

However, given the nature of the disease, there are a host of other signs and symptoms that may be present.

Motor skills symptoms

The symptoms which are chiefly present are:

  • Tremor – one of the most common symptoms of Parkinson’s disease is tremor of the hands, this is more noticeable when the hands are at complete rest. However it is thought that around 30% of the people who have Parkinson’s disease have very little tremor, these people are generally classed as akinetic-rigid.
  • Rigidity – this includes stiffness of the joints and when combined with tremor will produce a ratchety rigidity when the limbs are passively moved.
  • Akinesia – this is slowness or absence of movement * Postural instability – this often results in the person falling due to impaired balance down to the loss of postural reflexes.
  • Shuffling – the person when walking will very often take short steps with their feet barely leaving the ground, very often the person will trip over small obstacles in their path.
  • Problems turning – the person will keep their neck and trunk rigid when turning instead of just turning their head to look, this usually requires the person to take several small steps to make a turn.
  • Stooped posture – in severe or progressive forms of Parkinson’s disease the person’s head and upper body may become bent at a right angle to the trunk.
  • Speaking softly – the speech of the person may become hoarse, quiet and monotonous.
  • Drooling – the person may often drool, this is thought to be down to the inability to swallow properly and the persons gait.
  • Dysphagia – the person can lose all ability to swallow and this can lead to aspiration and eventually death.
  • Fatigue – the person will easily get tired over 50% of sufferers are thought to be affected by tiredness and fatigue.

Non-motor skill symptoms

  • Depression – depression is thought to affect between 30 to 80% of all people suffering from Parkinson’s disease.
  • Slowed reaction times – the persons voluntary and involuntary responses will show a significant delayed reaction.
  • Dementia – dementia will often occur in about 20 to 40% of all people suffering, this will be a later development in the disease.
  • Memory loss – memory loss is common particularly procedural memory loss rather than declarative.
  • Pain – sufferers can experience pain in their joints, muscles and tendons.

Glossary of Parkinson’s Terms

In order to become familiar with the disease, it is important to understand some of the terms used when discussing this condition.

Acetylcholine

A classical neurotransmitter found in the basal ganglia and throughout the body. An imbalance between the neurotransmitters acetylcholine and dopamine is associated with some of the symptoms of Parkinson’s disease (PD) for example, tremor and rigidity.

Action tremor

Involuntary movement of a limb after initiation of action.

Akinesia

A sharp decline in motor performance with complete loss of the ability to initiate voluntary movement and a loss of automatic movements, such as blinking.

Amantadine

Initially developed as an antiviral agent, this drug improves mild tremor, rigidity, and bradykinesia in some patients with PD. The exact mechanism of action is unclear; however, it seems to increase release of dopamine from the remaining cells of the substantia nigra.

Anticholinergic agents

Drugs, for example procyclidine, that inhibits the actions of acetylcholine. Anticholinergic agents tend to have a limited impact on the symptoms of PD and cause a number of debilitating side-effects, such as dry mouth, blurred vision, confusion, and urinary retention.

Apomorphine

A dopamine agonist is given as a continuous subcutaneous infusion or as a subcutaneous injection. Apomorphine is used to alleviate the symptoms of severe PD that is responding poorly to Levodopa. It is of particular benefit in patients with PD that experience ‘off’-times that last more than 30 minutes as it reverses symptoms within 10-15 minutes.

Ataxia

Loss of balance.

Athetosis

A form of dyskinesia characterised by slow, involuntary movements of the hands and feet.

Basal ganglia

Groups of cells in the grey matter of each half of the brain which coordinates automatic movements. It comprises various specialised groups of cells, or nuclei, such as substantia nigra.

Bradykinesia

A term used to describe slowness of motion and delayed initiation of movement, which is common in early stages of PD. Bradykinesia eventually progresses to Akinesia.

COMT inhibitors

A new class of drugs, for example, tolcapone and entacapone that block COMT resulting in an increased delivery of Levodopa to the brain.

Dementia

A disorder where brain cells die more quickly than in ordinary ageing which the results in memory loss and confusion, although affecting different cells to those affected in PD, it is experienced by some, especially elderly, patients with PD.

Decarboxylase

An enzyme in the blood and brain that metabolizes Levodopa to dopamine.

Dopamine

Dopamine is a neurotransmitter formed in the substantia nigra and transmitted, by the nigrostriatal fibres, to the striatum. A decrease in the number of dopamine-producing cells in PD results in impaired communication between the substantia nigra and the striatum. Dopamine deficiency is a causative factor of PD and is associated with bradykinesia, tremor, and rigidity.

Dopamine agonists

Drugs such as lisuride, bromocriptine, cabergoline, pergolide, and ropinirole that stimulate dopamine receptors directly. They are often used in conjunction with Levodopa to supplement its effect.

Dyskinesia

The most common and disruptive side-effect of PD therapy, dyskinesia is an involuntary movement that can accompany peak doses of Levodopa. Dystonia, athetosis, and chorea are specific types of dyskinesia.

Dystonia

Involuntary spasms of muscle contractions which cause abnormal movements and postures in those suffering from Parkinson’s disease, the Dystonia that occurs most frequently in PD is in the foot and is a characteristic of PD.

Levodopa

A precursor of dopamine, which is converted to dopamine in the brain, Levodopa is currently the treatment of choice for Parkinson’s.

Motor control

A patient’s ability to control movement.

Motor fluctuation

Variations in motor control.

Neurotransmitter

A chemical that is released from a neurone and transmits a message to either a nerve or a cell.

Parkinson’s disease

A progressive disease that is attributable to degenerative changes in cells of the basal ganglia. These result in a deficiency of the neurotransmitter dopamine and, in turn, impaired control of movement.

Resting tremor

Shaking that occurs in a relaxed limb. It usually stops when a voluntary movement of the affected limb is made.

Rigidity

Resistance to manipulation of a limb.

Shaking palsy

The term originally employed by James Parkinson to describe the disorder now known as Parkinson’s disease.

Substantia nigra

A region of the basal ganglia that is rich in dopamine-containing neurones.

Tremor

Involuntary shaking.

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