Parkinson’s Disease- Causes, Features & Diagnosis


When we talk about neurological disorders or diseases, Parkinson’s disease is one of the most common names. In the case of neurological disorders, most people confuse them with mental illness. The same thing is applicable to Parkinson’s disease as well. But we must remember that these two are a totally separate issue. We must have a clear idea of this disease. So, this article will help you to understand Parkinson’s disease in a better manner.


In this article, Dr. Gurneet Sawhney will explain the causes, features & diagnosis of Parkinson’s disease. He is one of the best neurosurgeon in Mumbai with several years of experience in this field. Dr. Gurneet Sawhney was also awarded as the “Most Promising Neurosurgeon in Maharashtra – 2016″ by Times Group.


Parkinsons Disease-

Parkinson’s disease is also called Parkinson disease, or PD. It is a movement disorder where the dopamine-producing neurons present in the substantia nigra of the brain go through degeneration. It is one of the most common neurological disorders.It is a progressive, adult-onset disease that gets

more common with age.


Causes of Parkinsons Disease-

Most of the time, there’s no known cause. But in some cases, there might be a genetic cause, like mutations, parkin, or alpha-synuclein genes. In rare cases, Parkinsonian disease may be caused by MPTP. It is a toxic impurity that can be found in the desmethylprodine.

In other people, one or more risk factors might contribute to Parkinson’s. For example, pesticide exposure or DNA variants in genes can be the reason. Whatever the cause is, Parkinson’s derives from the death of dopamine-producing neurons in the substantia nigra part of the brain. The name substantia nigra means “black substance”.

We usually considersubstantianigra as a single location. But actually, two of these regions are present in the brain. One on each side of the midbrain. The substantia nigra is a part of the basal ganglia which is a collection of brain regions that control movement through their connections with the motor cortex. In Parkinson’s, the darkened areas of substantia nigra get affected & they gradually disappear. Lewy bodies are present in the affected substantia nigra neurons before they die. Lewy bodies are eosinophilic, round inclusions made of alpha-synuclein protein. The function of alpha

-synuclein & Lewy bodies are not known. They are both found in several other diseases including Lewy body dementia and multiple system atrophy.


The SubstantiaNigra is divided into Two Sub-Regions

  1. Pars reticulata- This receives signals from another part of the basal ganglia called the striatum, and relays messages to the thalamus via neurons rich in the neurotransmitter gamma-aminobutyric acid.
  2. Pars compacta- This is the part of the substantia nigra affected in Parkinson’s sends messages to the striatum via neurons rich in the neurotransmitter dopamine, forming the nigrostriatal
    pathway, which helps to stimulate the cerebral cortex and initiate movement.

Therefore, when neurons present in substantia nigra pars compacta die, the individual may be in a hypo-kinetic or low movement state which is commonly seen in Parkinson’s. Besides simply initiating movements, the substantia nigra helps to calibrate and fine-tune the way those movements happen, which leads to the clinical features of Parkinson’s.


Clinical Features of Parkinsons-

  1. First, there’s a tremor, which is an involuntary shakiness most noticeable in the hands. It is called a “pill-rolling” tremor It actually looks like someone rolling a pill between their thumb and index finger. This is basically a “resting tremor,” meaning it is present at rest and diminishes with intentional movement.
  2. Next is rigidity. It refers to the stiffness that can appear as“cogwheel” rigidity. This is when there are a series of catches or stalls as a person’s arms or legs are passively moved by someone else. Besides this, rigidity is also responsible for the stooped posture and an almost expressionless face.
  3. Next up is Hypokinesia, a slow movement &akinesia, an absence of movement, and all these results from difficulty initiating movements. Examples of this are having the legs freeze up when trying to walk and also walking small steps.
  4. Finally, a late feature of Parkinson’s disease is postural instability. It causes problems with balance and can lead to falls.


Despite these multiple effects on body movement, Parkinson’s Disease does not produce any weakness. This helps to differentiate it from other diseases that affect the motor cortex or corticospinal pathway. Also, the resting tremor of Parkinson’s Disease helps to differentiate it from other cerebellar diseases, which might result in an action or intention tremor. This is a tremor that essentially the opposite of resting tremor, where the tremor actually gets worse with movement.

Also, bradykinesia and postural instability help to differentiate Parkinson’s disease from essential tremor. Non-motor brain functions can be affected in Parkinson’s disease as well which leads to additional common symptoms including depression, dementia, sleep disturbances, and difficulty smelling. These are because of dysfunction in dopaminergic signaling in other parts of the brain beyond the substantia nigra.

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