By Meghna Badami
As we age, it is common for neural pathways to gradually fade, but in neurodegenerative diseases like Parkinson’s, this process is accelerated. Parkinson’s disease is the second most common neurodegenerative disease affecting 1 million people in India. In the United States, 60,000 new cases are added each year.
Parkinson’s is caused due to drop in dopamine levels in the brain. Your brain’s white matter (made of a fatty substance called Myelin that surrounds axons of nerve cells) consists of a group of nuclei called the Basal Ganglia. The Basal Ganglia are responsible for a variety of things including movement, body balance and arousal mechanisms. A band of fibers arising from the Substantia nigra (a component of the Basal Ganglia) is an important Dopaminergic pathway and when this pathway is affected, it manifests as Parkinson’s disease.
Symptoms of Parkinson’s Disease:
Symptom’s begin to develop after the age of 60. Bradykinesia or slow movements is a major symptom. Slowing down of movements occurs as a part of the natural aging process, but is much more advanced in Parkinson’s. Hypokinesia is also a symptom. It refers to difficulty in initiating movements. Rigidity causes difficulty in contraction of muscles and hence difficulty in movement.
The absence of movement coordination results in patients being unable to perform more than one task at a time. For example, the subject will not swing his arms while walking. Patients are often described to have a ‘Mask face’ since they don’t show much expression while talking. The cause for this is the same as the aforementioned one.
Resting tremors are the earliest symptoms of the disease. A Festinant Gait is often observed. This involves short, shuffling steps and bending forward while moving.
Since Dopamine is involved in inducing feelings of joy and happiness, Parkinson’s patients may experience depression. Slurring of speech is often seen.
DOPA drugs: Dopamine cannot be administered directly since it cannot cross the Blood Brain barrier (A barrier formed by nerve cells and endothelial cells in blood vessels that prevent blood flow into the brain) and hence it’s precursor- I-1,3-Dihydroxyphenylalanine is given orally.
Dopamine Agonists mimic the effect of Dopamine on the brain.
MOA inhibitors: Monoamino Oxidase in an enzyme that degrades Dopamine and hence this method helps increasing dopamine activity.
Speech Therapy and Occupation therapy can help patients deal with symptoms.
Deep Brain Stimulation is done in the later stages where medication has no effect. An electrode is inserted into the Pedunculopontine (PPN) Nucleus that controls movement. A pacemaker like device- a neurostimulator is placed under the skin of the chest. The neurostimulator sends signals to the electrode which in turn stimulates the PPN to release neurotransmitters that induce action potentials in nerves which eventually stimulate a muscle.
A recent study showed that misfolding of a protein called Alpha Synuclein causes it to accumulate in the Basal Ganglia, affecting nigrostriatal pathways. Drugs are being developed as antagonists to these proteins.
Parkinson’s affects millions worldwide and as someone who is a caregiver to a Parkinson’s patient, mine and many other families can only hope that research helps us find a definitive cure.
 Guyton and Hall Textbook of Medical Physiology
 GK Pal Textbook of Medical Physiology