Parkinson's Disease 

Hello students and friends, today we are going to learn what is Parkinson's disease, how it is caused along with their pathophysiology, signs and symptoms, diagnosis, and treatment.

Let us discuss first what is Parkinsonism?

• It is a neurological disorder.
• Also known as paralytic agitans.
• It is slowly, progressive, and degenerative disorder of the brain in which dopamine level gets decreased.

~Destruction of a dopaminergic neuron(neuron which synthesizes dopamine).

~Dopaminergic neurons are present in the midbrain(basal ganglia), in basal ganglia substantia nigera is present which releases dopamine.

~The important point related to Parkinson's is that it is not a muscle disease, because there is no muscle weakness in the case of parkinsonism as basal ganglia are not involved with muscle strengthening.

As there is a deficiency of dopamine in the case of Parkinson's, then we have to understand first its function.

Function of Dopamine

1. Dopamine is a neurotransmitter or messenger which helps in sending signals or impulses between the brain and the distal part of the neuron.
2. It gives inhibitory responses, the impulses which the brain sends to the distal parts get filtered and extra impulses get eliminated by its inhibitory response.
3. Mood changes are also associated with the level of dopamine. If there is euphoria, then the level of dopamine is increased.
4. Memory(if the level of dopamine is less then the memory also gets decreased).
5. It also regulates behavior and cognition.

As there is a decreased level of dopamine, then its functions also get altered.

Etiology

• The cause is idiopathic.
• It might be genetic, present from birth(juvenile).
• Trauma
• Damage in the mid-brain after head injury which leads to damage in the brain stem and subsequently decreases in dopamine production cells and the level of dopamine gets decreased.
• Stroke
• As the artery of the brain gets damaged and oxygen supply gets disturbed means condition of hypoxia is seen.
• Hypoxia leads to a decrease in the level of substansia nigera(dopamine production cells), subsequently a decrease in the level of dopamine.
• Hydrocephalus.
• Excessive use of drugs, especially anti-psychotic drugs(which is mainly used in depression).
• Inflammation in the brain parenchyma(encephalitis).

Signs and symptoms

In parkinsonism, there are 4 major cardinal signs.

1. Tremors(first sign)- mostly resting tremors.
2. Rigidity(second sign)- cogwheel rigidity.
3. Bradykinesia(movements get slow down).
4. Postural changes- shuffling gait, slurred speech, torticollis movement, propulsive gait.

Other signs and symptoms are:

1. Speech changes.
2. Writing changes
3. Loss of autonomic movements.

Pathophysiology

• Due to any etiological cause, the level of dopamine gets decreased(decrease of sensory inhibitor) and the level of acetylcholine gets increased(excitatory activity increased).
• When an excitatory activity is increased at the neuromuscular junction, sodium channels get open and it enters through the channel and then the development of positivity increases the muscle tone and stimulation contraction.
• This will rise to tremors and extra contraction of muscles leads to stiffness and spasm of the muscle and there is overstimulation of neuron which leads to an increase in muscle tone.
• As muscle tone increases, it gives rise to tremors and tremors are the first sign of Parkinson's disease.

Management

1. Levodopa+Carbidopa.
2. Bromocriptine.
3. Amantadine
4. Monoamine Oxidase inhibitor(MOAI)- Rasagiline.
5. Anticholinergic drugs(Benzotropine).
6. Physiotherapy management(exercises, using gait-aids, movement strategy training).

Effects of drugs

• Levodopa is given to stimulate basal ganglia to covert it in dopamine.
• Carbidopa helps in the crossing of the blood-brain-barrier and prevents levodopa from a breakdown in the blood due to enzyme dopadihydroxinase.
• Bromocriptine increases the production of dopamine.
• Amantadine increases the level of dopamine if there is a decrease in dopamine levels.
• Anticholinergic drugs increase dopamine levels and decrease the Ach level.

Side-effects of drugs

• Levodopa+Carbidopa may lead to nausea and dysrhythmia.
• Bromocriptine decreases the level of prolactin hormone synthesis, which leads to decrease in milk production in the female which hinder in breastfeeding of baby, that is why it is recommended that pregnant female will not use this medicine during pregnancy.
• Amantadine will cause nausea, constipation, drowsiness, headache, and blurred vision.
• Anticholinergics drugs should be avoided in glaucoma patients and in alcoholic patients.
• MOAI is avoided with levodopa as well as with tyramine food(vine, beer).

Hope you all find this helpful for you, if you have any query related to this topic or any other topic then you all are free to contact me via contact us or you can also ask your doubts on the comment box. Thank you! 

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