Understanding Parkinson’s disease

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.