PARKINSON'S DISEASE
The disease starts when there is depigmentation of substantia nigra compacta a portion of the basal ganglia located at the midbrain composed of dark dopaminergic nerve network and the loss of dopamine input into the network.
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| SEE THE SUBSTANTIA NIGRA COLOURED IN RED |
In general, due to the excessive loss of dopaminergic nerve network in the basal ganglia and the depletion of dopamine input into the midbrain leads to the distinctive motor disability known as Parkinson's disease.
TYPES OF PARKINSONISMS
This is also known as Classic type or paralysis agitans
The etiology is unknown and even the treatment is palliative the classic form is incurable.90% of the cases are of this type.
But there is some hypothesis of the etiology of this type. They are assumed as prolonged exposure to potent neurotoxins such as carbon monoxide, N-methyl-4-phenyl-1,2,3,6 tetrahydro pyridine(MPTP), and manganese. But these are only assumptions as some of the pathologic conditions produced by these toxins can be cured by proper therapies.
Exposure to these agents along with the age of nervous weakness or degeneration may be the cause for this incurable type.
Another hypothesis is exposure to free radicals. Dopamine is catabolized by Monoamine oxidase (MAO) an enzyme abundantly available at the mitochondria of the ganglia which results in the formations of toxic free radicals such as OH-, Fe3+along with hydrogen peroxide(H2O2). If any deficiency of our body's natural protective mechanism against these free radicals or lack of supply antioxidants such as vitamin-C and E or hypersecretion of dopamine may lead to the suicide of its own nerve network in substantia nigra compacta at the midbrain.
2.Non-Classical or Secondary
This type is rare and uncommon and curable as mostly this type occurs with known causes.
This type is mostly caused by drug abuses such as:-
Dopamine antagonists such as Phenothiazines(Chlorpromazine, perphenazine)
Butyrophenones(Haloperidol)
Reserpine
Poisoning by chemicals such as
CO poisoning
Heavymetal poisoning (Manganese, mercury)
MPTP, a commercial product used in the making of synthetic heroin-like narcotics.
Infections such as
Viral Encephalitis.
Syphilis
Other physiological disorders such as
Arteriosclerosis
Progressive supranuclear palsy(A nervous degenerative defects)
Wilson's disease (A metabolic disorder)
Symptoms of Parkinsonism
Tremor, starts with action tremor followed by resting tremor(First symptom)
Limb rigidity is clinically detected by when the arm responds with a rachet-like(e.g. Cog wheeling) movement when the limb is moved passively
Akinesia or Bradykinesia, Akinesia is characterized by difficulty in initiating movement and bradykinesia a slow response of the muscle for a move.
Gait and Postural Difficulties are detected by the patient's walk with a stooped flexed posture; a shuffling stride and an irresponsive and irregular rhythm of arm movements with the legs.
Changes in mental state including 50% depression and 25% dementia
There are five stages of the disease as follows:-
1.Unilateral involvement
2.Bilateral involvement but no postural abnormalities
3. Mild postural imbalance with bilateral involvement and patient can lead an independent life
4. Bilateral involvement with postural instability, require substantial help
5. Severe fully developed disease and patient restricted to bed and chair.
Diagnosis
Tests such as MRI scans should be carried out to rule out the secondary type of the disease.
The latest technology of imaging such as Positron Emission Tomography is carried out in order to estimate the extent of the neuronal loss and to visualize the dopamine uptake in the substantia nigra.
