PARKINSON DISEASE
Parkinson disease is a slowly
progressive degenerative disease of nervous system associated with destruction of
brain cells, which produce dopamine. It is named after the discoverer James
Parkinson. It is also called parkinsonism or paralysis
agitans. Great boxer Mohammed Ali is affected by parkinsonism because of
repeated blows he might have received on head resulting in damage of brain cells
producing dopamine.
Causes of Parkinson
Disease
Parkinson disease occurs
due to lack of dopamine caused by damage of basal ganglia. It is
mostly due to
the destruction of substantia
nigra and the nigrostriatal pathway, which has
dopaminergic fibers. Damage of basal
ganglia usually occurs because of the following causes:
i. Viral infection of
brain like encephalitis
ii. Cerebral
arteriosclerosis
iii. Injury to basal
ganglia
iv. Destruction or removal
of dopamine in basal ganglia. It occurs mostly due to longterm
treatment with antihypertensive
drugs like reserpine. Parkinsonism due to the drugs is known as
drug-induced
parkinsonism.
v. Unknown causes:
Parkinsonism can occur because of the destruction of basal ganglia due
to some unknown causes.
This type of parkinsonism is called idiopathic parkinsonism.
Signs and Symptoms of
Parkinson Disease
Parkinson disease develops
very slowly and the early signs and symptoms may be unnoticed for months or even
for years. Often the symptoms start with a mild noticeable tremor in just one
hand. When the tremor becomes remarkable the disease causes slowing or freezing
of movements followed by rigidity.
Following are the common
signs and symptoms of
Parkinson disease:
i.
Tremor
ii.
Parkinson
In this disease, the tremor occurs during
rest. But it disappears while doing any work. So, it is called static
tremor or resting tremor. It is also called drum-beating
tremor, as the movements are similar to beating a drum. Thumb moves rhythmically over the index and middle fingers.
These movements are called
pill-rolling movements.
ii. Slowness of
movements
Over the time, movements
start slowing down (bradykinesia) and it takes a long time even to
perform a
simple task. Gradually the
patient becomes unable to initiate the voluntary activity (akinesia)
or the voluntary movements are reduced (hypokinesia).
It is because of hypertonicity of the muscles.
iii. Poverty of
movements
Poverty of movements is
the loss of all automatic associated movements. Because of absence of the
automatic associate
movements, the body becomes statue-like. The face
becomes mask-like, due to absence of appropriate expressions
like blinking and smiling.
iv. Rigidity
Stiffness of muscles
occurs in limbs resulting in rigidity of limbs. The muscular stiffness occurs
because of
increased muscle tone
which is due to the removal of inhibitory influence on gamma
motor neurons. It affects both flexor and extensor muscles
equally. So, the limbs become more rigid like pillars. The
condition is called lead-pipe rigidity. In later stages the rigidity
extends to neck and trunk.
v. Gait
Gait refers to manner of
walking. The patient looses the normal gait. Gait in Parkinson disease is
called
festinant
gait. The patient walks quickly in short steps by bending forward as if
he is going to catch up the
center of gravity.
vi. Speech problems
Many patients develop
speech problems. They may speak very softly or sometimes rapidly. The words are
repeated many times. Finally, the speech becomes slurred and they hesitate to
speak.
vii. Emotional changes
The persons affected by
Parkinson disease are often upset emotionally.
viii. Dementia
In later stages, some
patients develop dementia.
Treatment for
Parkinson Disease
As Parkinson disease is
due to lack of dopamine caused by damage of dopaminergic
fibers, it is treated
by dopamine
injection. Dopamine does not cross the bloodbrain barrier. So,
another substance called levodopa (Ldopa) which
crosses the bloodbrain barrier is injected. Ldopa moves
into the brain and there it is converted into
dopamine. Since, Ldopa can be converted into dopamine
in liver, some side effects occur due to excess
dopamine content in liver and blood. So, along with
Ldopa, another substance called carbidopa is administered.
Carbidopa prevents the conversion of Ldopa into
dopamine and carbidopa cannot pass through
bloodbrain barrier. Thus, Ldopa moves
into the brain tissues and is converted into dopamine. Some of
the symptoms of Parkinson disease such as tremor
are abolished by surgical destruction of basal ganglia
or thalamic nuclei.
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