Understanding Parkinson's disease

More than 70,000 Australians are currently living with Parkinson’s disease, a brain condition that impacts both motor skills and many non-motor functions. People with Parkinson’s battle mobility issues and may also suffer from cognitive impairment, psychosis (hallucinations and delusions), anxiety, depression, constipation, and difficulties with sleep, smell, swallowing, speech, writing and vision.

Rates appear to be on the rise, with more than 32 new diagnoses every day. Although those with Parkinson’s disease are mainly elderly, there were nearly 2,400 people aged in their 30s and 40s in Australia estimated to be living with Parkinson’s in 2014.

It is the second most common neurodegenerative condition in Australia but one of the least understood. Although the condition is manageable, it simply gets worse over time. There’s no definitive test and no cure.

So, what do we know about it so far—and what is there still to learn?

What causes Parkinson’s disease?

The main features of Parkinson’s disease occur when the brain cells that produce dopamine are lost, resulting in reduced dopamine production. Dopamine is a neurotransmitter (a chemical 'messenger' in the brain), and it's responsible for smooth, coordinated movements and our drive or desire to get things done. It's also well-known as the 'feel good' chemical, as it controls the brain's pleasure and reward systems.

This death of dopamine-producing cells is accompanied by certain proteins clumping together and becoming tangled, forming what's known as Lewy bodies, which can be seen with a microscope.

People at the early stages of Parkinson's disease may experience symptoms such as a loss of the sense of smell, constipation and Rapid Eye Movement Sleep Behaviour Disorder, where people act out their dreams. The physical symptoms that we more commonly associate with Parkinson's, such as tremor (shakiness), rigidity and slowness, typically come later. 

While deterioration of the dopamine system and its effects on movement are the best-known features of the disease, other brain areas, the peripheral nervous system and the gut are also affected. The degeneration that occurs in these other brain regions later in the disease is responsible for the high rates of dementia and serious disability that often leads to loss of independence and nursing home care.

There is no definitive test or biomarkers for early diagnosis of Parkinson’s disease. By the time Parkinson’s disease has been diagnosed, usually following the appearance of conclusive symptoms, around 50 per cent of the dopamine-producing cells have already been lost.

Scientists are unsure what causes the initial loss of the dopamine-producing cells. Current thinking is that Parkinson’s could be the result of environmental toxins, such as pesticides; damage caused by free radicals—unstable molecules—within brain cells or the body; infections; genetic predisposition; or a combination of some or all of these.

How can we treat it?

Treatment of the symptoms of Parkinson’s disease usually takes the form of complex combinations of drugs that target the systems of the brain associated with dopamine.

Established surgical techniques, such as deep brain stimulation (DBS) and the more experimental transcranial direct current stimulation (tDCS), have been developed to target the regions of the brain responsible for movement. These involve electrical stimulation of the brain, and while they can help with some of the symptoms of Parkinson's, they can't prevent ongoing cell death. 

Research is ongoing to further improve our understanding of brain function, the role of particular brain regions and how dopamine-producing cells start to deteriorate. Scientists are also working to better understand how the progressive build-up of certain proteins associated with Parkinson's occurs in the brain.

If we're able to improve how we objectively measure the symptoms of Parkinson’s disease, through biomarkers and using wearable technologies, this may lead to early detection, improved therapies, better understanding of disease mechanisms and better care.