In the online series Shrinking, Hollywood actor Harrison Ford plays the role of Dr Rhoades, who is diagnosed with Parkinson’s disease. Ford’s portrayal of the noticeably soft, shaky voice and frozen gait, and otherwise unknown symptoms of the condition was so convincing that viewers wondered if Ford had Parkinson’s in reality.
Parkinson’s disease is a neurodegenerative movement disorder where people experience hand tremors, shaky voice or unsteady walking (gait) symptoms.
However, Dr Oliver Sacks, neurologist and author of Awakening, points out: “It is necessary to say at the outset that shaking, or tremor is by no means a constant symptom in Parkinsonism; it is never an isolated symptom and is often the least problem which faces the person with Parkinson’s.”
The unseen symptoms
According to Dr Sacks, in some cases, the telltale signs could begin as early as a decade before a person is diagnosed with Parkinson’s disease.
Dr Roopa Rajan from the All India Institute of Medical Sciences, Delhi, and Dr Sindhu D M from Apollo Hospitals, Bengaluru, list nine non-motor symptoms of Parkinson’s:
- Constipation: Dr Rajan and Dr Sindhu confirm that constipation surfaces nearly ten years before the onset of Parkinson’s. It continues after the diagnosis, with further bloating and gastrointestinal dysfunction.
- Loss of smell: “[They have] `hyposmia’ or a reduced sense of smell. It is gradual and begins before the onset of Parkinson’s,” says Dr Sindhu. Dr Rajan says that over 80 per cent of people with Parkinson’s experience hyposmia.
- Sleep disorder: Dr Rajan says that people with the condition have vivid dreams, so much so that they begin acting out their dreams and can sometimes get violent. Dr Sindhu says that prolonged or REM sleep behaviour disorder leads to excessive daytime sleepiness.
- Anxiety and depression: 70 to 80 per cent of people with Parkinson’s experience depression and anxiety at some point in their lives, says Dr Rajan.
- Fatigue: Once Parkinson’s sets in, people can experience unexplained pains and fatigue. “Sometimes people come in with shoulder pains, not realising that the symptoms are setting in,” says Dr Sindhu.
- Cognitive issues: Parkinson’s being a neurodegenerative condition, symptoms of memory, attention and cognition loss begin to set in gradually. Dr Rajan and Dr Sindhu note that the symptoms are similar to dementia.
- Psychiatric issues: Sometimes people might develop visual hallucinations or delusions, says Dr Sindhu. People with Parkinson’s have also been seen to ‘act out’ impulsively and show promiscuous behaviour.
- Low blood pressure and light-headedness: Also called neurogenic orthostatic hypotension, people can have sudden giddiness or light-headedness when they get up from a sitting position. Sometimes they may faint, say the experts.
- Facial expression: Due to loss of muscle movement, these people can fail to make facial expressions and can be misunderstood to be indifferent to others.
What causes non-motor symptoms
Dopamine — a neurotransmitter produced in the brain – is found to be a key player in Parkinson’s disease. Studies have found that dopamine mediates other brain hormones — namely serotonin, noradrenaline and acetylcholine. It has a domino effect on them, initiating their role in different brain regions.
Dopamine’s role assumes importance in the disease condition as it influences the cross-talk between other brain regions responsible for movement, emotion, memory and cognitive functions. An imbalance in dopamine affects this cross-talk in the brain.
Parkinson’s disease has been linked to many genes called PARK genes, which are critical in energy utilisation in cells (mitochondrial dysfunction), cell death pathways, synapses and the body’s immune response.
Interestingly, PARK genes are most active in adulthood. This means the genes kick in during adulthood, and the resulting symptoms develop later in life. Hence, although dopamine is an essential neurotransmitter, the effects of its insufficiency are not seen until later in life.
That could also be why some of the non-motor symptoms of Parkinson’s begin years before the onset of the condition.
Inflammation effects
Studies in mice have shown that when some Parkinson’s mutation occurs in genes involved in social stress, the mice become prone to depression. The same is true for PARK genes that play a role in the immune pathway. When these genes are mutated, they lead to inflammation in the brain, which is gradual and eventually affects cognition.
In addition, low dopamine levels affect the cross-talk between the immune system and the brain, leading to an inflamed condition. The inflammation affects neurons – another reason for non-motor symptoms.
Elusive symptoms
Dr Rajan says although constipation, hyposmia, sleep disorder, and depression are seen earlier than the onset of the classic Parkinson’s symptoms, they cannot be used as an indicator of the condition. Detailed investigations by a neurologist will help with an accurate diagnosis.
“Research has still not found definitive causes for Parkinson’s. We know that genetic and environmental factors are involved, and studies are looking further into it,” she adds.
Dr Sindhu points out that the fear of the condition is understandable. However, it is heartening that some people have lived quality lives 20-25 years after they were diagnosed as having the disorder.
Read more: Trembling truths: not all tremors are Parkinson’s
Read more: Deep brain stimulation can revive movement in Parkinson’s
