What is Parkinson's Disease (PD)?

PD is a progressive nervous system disorder that affects how the person moves, including how they speak and write.

  • PD belongs to a group of conditions called movement disorders. Movement disorders describe a variety of abnormal body movements that have a neurological basis
  • Symptoms start gradually, sometimes starting with a barely noticeable tremor in just one hand. Tremors are common, but the disorder also causes stiffness or slowing of movement
  • The muscles of a person with PD become weaker and the individual may assume an unusual posture
  • In PD, certain nerve cells (neurons) in the brain gradually break down or die. Many of the symptoms are due to loss of neurons that produce a chemical messenger in the brain called dopamine. When dopamine levels decrease, it causes abnormal brain activity, leading to symptoms of PD

Causes Of Parkinson's

PD results from degenerative loss of midbrain dopamine neurons in the Substantia nigra that causes movement problems1.


10% of cases of PD’s disease are primarily due to genetic causes. The most common genetic effect that triggers PD is mutation in a gene called LRRK2.

Environmental triggers2.

  • Significant exposure to pesticides or certain heavy metals.
  • Repeated head injuries.


People usually develop PD around age 60 or older. If someone is diagnosed with PD at the age 21-50 years, it is referred to as early onset or young onset PD (YOPD).


Men are more likely to develop PD than are women.

causes of parkinsons

Problems of Oral Therapy in PD patients

Treatment Related

Failure of an oral dose of levodopa to produce an effect and delay in the onset of action have been associated with problems in absorption of oral medication in PD patients.

Most patients continue to experience residual OFF time with Oral dopamine agonists, Monoamine oxidase (MAO) inhibitors, and (COMT) inhibitors, which causes4,5

  • Delayed time-to-ON
  • Dose failures
  • Suboptimal ON response

Patient Related

More than 80 % of patients with PD develop dysphagia during the course of their disease4.

Dysfunction of the gastrointestinal tract leads to:

  • Problems with absorption of oral PD medication6
  • Erratic treatment response
  • Silent aspiration, which is one of the key risk factors in developing pneumonia

The issue is further complicated by gut abnormalities, such as

  • Small intestinal bacterial overgrowth (SIBO), altered gut microbiota

Stages Of Parkinson's



Symptoms of Parkinson’s are mild and only seen on one side of the body (unilateral involvement)



Symptoms of Parkinson’s on both sides of the body (bilateral involvement) or at the midline



Symptoms of Parkinson’s are characterized by loss of balance and slowness of movement



Symptoms of Parkinson’s are severely disabling



Symptoms of Parkinson’s are severe and are characterized by inability to rise

Signs and Symptoms


  • Tremor: Usually begins in a limb, often the hand or fingers. Patient may rub thumb and forefinger back-and-forth, known as a pill-rolling tremor. Patient’s hand may tremor when it's at rest
  • Slowed movement (Bradykinesia): Movement may slow down making simple tasks difficult and time-consuming. Steps may become shorter while walking and it may be difficult to get out of a chair
  • Rigid muscles: The stiff muscles can be painful and limit the range of motion
  • Impaired posture and balance: Posture may become stooped or patient may have balance problems
  • Loss of automatic movements: Patients may have a decreased ability to perform unconscious movements, including blinking, smiling or swinging arms
  • Speech changes: Patient may speak softly, quickly, slur or hesitate before talking. Speech may become monotonous
  • Writing changes: Patient may face difficulty in writing, and the writing may appear small


  • Mood disorders: Such as depression, anxiety and irritability
  • Cognitive changes: Such as problems with focused attention and planning, slowing of thought, language and memory difficulties, personality changes, dementia
  • Orthostatic hypotension: A drop in blood pressure when standing, light-headedness
  • Sleep disorders: Such as insomnia, Excessive Daytime Sleepiness (EDS) Etc
  • Constipation and early satiety: A feeling of fullness after eating small amounts
  • Hallucinations and delusions
  • Pain, Fatigue
  • Urinary incontinence


1. Dialogues Clin Neurosci. 2004 Sep; 6(3): 259–280.

2. American Parkinson disease association https://www.apdaparkinson.org/what-is-parkinsons/causes/

3. Mayo clinic. Parkinson's disease. https://www.mayoclinic.org/diseases-conditions/parkinsons-disease/symptoms-causes/syc-20376055

4. Suttrup I1 Dysphagia in Parkinson's Disease. Dysphagia. 2016 Feb;31(1):24-32.

5. Iisaacson S. et al.Apomorphine Subcutaneous Injection for the Management of Morning Akinesia in Parkinson's Disease.2016. MOVEMENT DISORDERS CLINICAL PRACTICE.

6. Chaudhuri K. et al, Non-oral dopaminergic therapies for Parkinson's disease: current treatments and the future. NPJ Parkinsons Dis. 2016 Dec 1;2:16023.

7. parkinson's foundation http://www.parkinson.org/Understanding-Parkinsons/Non-Motor-Symptoms

8. American parkinson's disease association. https://www.apdaparkinson.org/what-is-parkinsons/symptoms/

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