Parkinson's disease

Deep inside the brain is a small area that makes dopamine, a chemical that helps movements start smoothly and stay steady. In Parkinson's disease these cells are lost slowly over years, dopamine falls, and movement becomes slow, stiff and shaky.

Symptoms usually begin after the age of fifty, though some people are affected younger. The condition worsens slowly, but it is not contagious and not directly fatal.

Symptoms usually start on one side of the body and are mild at first. Three movement signs define the condition.

• Slowness: tasks take longer, steps become short and shuffling, and the face shows less expression
• Stiffness: muscles feel tight, and arms swing less while walking
• Tremor: shaking that is usually worst when the hand or leg is resting
• Smaller handwriting, a softer voice, and drooling
• Loss of smell, constipation and disturbed sleep, often years before the movement signs
• Low mood, tiredness and, in later years, poor balance, falls and memory difficulty

See a doctor within a few days for a new or worsening tremor, stiffness or slowness, for repeated falls, for medicines wearing off early or causing extra movements, for difficulty swallowing, or for new confusion, hallucinations or low mood.

The reason the dopamine-making cells die is not known. Most experts consider it a mix of genetic make-up and things in the environment. A small number of families carry genes that clearly raise the risk.

Similar symptoms can also come from certain medicines, repeated head injury or small strokes, so a doctor checks for these before settling on a diagnosis.

• Older age, most often after fifty
• Being male, as men are affected slightly more often
• A close relative with Parkinson's disease
• Long exposure to pesticides or industrial solvents
• Air pollution, and repeated head injury

Falls and the fractures they cause are the most common serious problem, and difficulty swallowing can let food or drink enter the lungs and cause pneumonia. Constipation, disturbed sleep, bladder trouble and dizziness on standing are frequent.

Depression and anxiety affect many people, and memory can suffer in later years. All of these can be treated, so they are worth reporting rather than accepting.

There is no proven way to prevent Parkinson's disease. Sensible steps include:

• Regular exercise, including walking, balance work and strength training
• Protecting the head with a helmet while riding
• Careful handling of pesticides and solvents, with proper protection at work
• Not smoking, and controlling blood pressure, sugar and cholesterol
• Making the home safer: good light, no loose mats, rails where needed

There is no single test. A neurologist makes the diagnosis from the history and a careful examination of movement, looking for slowness together with stiffness or a resting tremor.

Blood tests and an MRI or CT scan are often done to rule out other causes such as thyroid problems or small strokes. A specialised scan of the dopamine system is sometimes used when the picture is unclear, and a clear response to dopamine medicine supports the diagnosis.

The main treatment is medicine that raises dopamine in the brain, most commonly levodopa combined with another drug that helps it reach the brain. Other groups act on dopamine in different ways, and the doctor chooses according to age, symptoms and daily routine.

Physiotherapy for walking and balance, occupational therapy for daily tasks, and speech therapy for voice and swallowing matter as much as the tablets. Regular exercise helps function.

When medicines no longer give steady control, a specialist may consider deep brain stimulation, in which fine electrodes placed in the brain deliver small electrical pulses.