Tremor refers to an involuntary shakiness which is most noticeable in the hands, characteristically called a pill-rolling tremor, because it looks like the sufferer is rolling a pill between the thumb and index finger. Rigidity refers to stiffness which can appear as cogwheel rigidity, and is also responsible for a stooped posture and an almost expressionless face. Bradykinesia refers to slow movement, hypokinesia refers to lessened movement, and akinesia refers to absence of movement. All three result from difficulty initiating movement, like legs freezing up when trying to walk and walking with a shuffling gait. Postural instability refers to problems with balance and can lead to falls, which is considered to be a late feature of the disorder.
Parkinson’s disease affects non-motor brain functions as well, leading to additional common symptoms like depression, dementia, sleep disturbances, and difficulty smelling. These are thought to arise due to dysfunction of dopaminergic signaling in other parts of the brain, beyond the substantia nigra. Another thought is that non-motor symptoms come about because of dysfunction in other neurotransmitters, like acetylcholine. There are also a handful of conditions that mimic Parkinson’s disease. These include essential tremor, normal pressure hydrocephalus, dementia with Lewy bodies, multiple system atrophy, corticobasal syndrome, and progressive supranuclear palsy. In each of these conditions, one or more of slowness, stiffness, tremor, and imbalance are present.
The cause of Parkinson’s disease is unknown, but it is believed that genetics, environmental factors, and the interaction between genetics and the environment may play a role. Genetic causes may include mutations in the PINK1 gene, parkin gene, or alpha-synuclein gene. In rare cases, a toxic impurity known as MPTP may be the cause, which is found in the recreational drug called MPPP, or a synthetic opioid. Parkinson’s disease is thought to affect approximately 1 in 500 people, with most of them developing symptoms after the age of 50. That said, approximately 1 in 20 sufferers will experience symptoms before the age of 40.
In order for a neurologist to consider Parkinson’s disease, two of its four main symptoms must be present. That is, tremors or shaking, slowness of movement, stiff or rigid muscles, and trouble with balance. As such, diagnosing Parkinson’s disease is not a straightforward process, but making an accurate and early diagnosis is very important, since early treatment is greatly beneficial. While there is no standard treatment for Parkinson’s disease, common options include medication, surgical therapy, lifestyle modifications, rest, and exercise.