This case consists of information on Parkinson's disease and the mechanism (direct & indirect pathway) behind it. Also there is information on Tourette's syndrome.
Part I: Parkinson’s disease
1. What is Parkinson’s disease?
Parkinson’s disease: a progressive nervous system disorder that affects movement.
Symptoms
The 4 major symptoms of Parkinson’s disease are:
- Tremors
- Muscular rigidity
- Involuntary movement
- Postural disturbances
Each symptoms may be manifested in different body parts in different combinations. Because
some symptoms reflect the acquisition of abnormal behaviors (positive symptoms) and others the
loss of normal behaviors (negative symptoms), we consider Parkinson’s symptoms within these 2
categories.
Positive symptoms
The most common positive symptoms are:
1. Tremor at rest. Alternating movements of the limbs when they are at rest stop during
voluntary movements or during sleep.
2. Muscular rigidity. Simultaneously increased muscle tone in both extensor and flexor
muscles is particularly evident when the limbs are moved passively at a joint. Movement is
resisted, but with sufficient force the muscles yield for a short distance and then resist
movement again.
3. Involuntary movements. These may consist of continual changes in posture, sometimes to
relieve tremor and sometimes to relieve stiffness. These small movements or posture
changes, sometimes referred to as akathisia or cruel restlessness, may be concurrent with
general inactivity. Other involuntary movements are distortions of posture, such as those
during oculogyric crisis (involuntary turns of the head and eyes to one side).
Negative symptoms
The negative symptoms can be divided into five groups:
1. Postural disorders.
A disorder of fixation: consists of an inability to maintain or difficulty in maintaining a
body part in its normal position in relation to other body parts.
Disorders of equilibrium: consists of difficulties in standing or sitting unsupported.
2. Righting disorders. Patients have difficulty standing from a supine position. Many patients
with advanced disease have difficulty even in rolling over, which is problematic in bed.
3. Locomotive disorders. Normal locomotion requires supporting the body against gravity,
stepping, balancing while body weight is transferred from one limb to another, and pushing
forward. Patients with Parkinson’s disease have difficulty initiating stepping. The shuffle
with short footsteps on a fairly wide base of support because they have trouble
maintaining equilibrium.
4. Speech disturbances. A speech most noticeable to relatives is almost complete absence of
tone in the speaker’s voice.
, 5. Akinesia. A poverty or slowness of movement may also manifest itself in a blank facial
expression or lack of blinking, swinging the arms when walking, spontaneous speech, or typical
fidgeting movements. Akinesia also manifests in difficulty making repetitive movements, such as
tapping, even in the absence of rigidity.
Epidemiology
Parkinson’s disease is fairly common. Incidence estimates vary from 0.1-1% of the population and
the incidence rises with old age. Also, the incidence is higher in countries with longer life
expectancies.
Risk factors & progression
Most Parkinson’s cases are not likely inherited, but about 25% of people with Parkinson’s do have
a living relative with the disease.
Positive and negative symptoms of Parkinson’s disease begin insidiously, often with a tremor in
one hand and slight stiffness in the distal parts of the limbs. Movements may then slow, the face
becoming mask-like with loss of eye-blinking and poverty of emotional expression. Difficulty in
swallowing saliva may result in drooling. Although the disease is progressive, usually it takes 10-20
years before the symptoms elapse.
A most curious aspect of Parkinson’s disease is its on-again-off-again quality. Symptoms may
appear suddenly and disappear just as suddenly. Partial remission may also occur in response to
interesting or stimulating situations.
Causes of Parkinsonism
The three major types of Parkinson’s disease are:
Idiopathic: its cause is unknown. Its origin may be familiar or it may be part of the
aging process but it is also thought that it might have a viral origin. It most often
develops in people older than 50 years old.
Post encephalitic: the cause is related to the death of cells in the substantia nigra. It
originated from the sleeping sickness. There is no evidence of viral cause, although it is
still believed to be likely.
Drug-induced: it is associated with ingesting various drugs, particularly major
tranquilizers, including reserpine and several phenothiazine and butyrophenone
derivatives. The symptoms are usually reversible but are difficult to distinguish from
those of the genuine disorder.
It may also result from arteriosclerosis, syphilis, tumor development, and carbon monoxide
poisoning or manganese intoxication.
The cells of the substantia nigra are the point of origin of fibers that extend into the frontal cortex
and basal ganglia and to the spinal cord. The neurotransmitter at the synapses of these projections
is dopamine. The cause of Parkinson’s disease has been identified with some certainty as a lack of
dopamine or, in drug-induces cases, lack of dopamine action. Dopamine depletion may not
account for the whole problem in some people, however, because decreases in norepinephrine
have been recorded, and numerous results show that cells in some basal ganglia nuclei may
degenerate as well.
Psychological aspects of Parkinson’s disease
Psychological symptoms in patients with Parkinson’s disease are as variable as the motor
symptoms. Nonetheless, a significant percentage of patients have cognitive symptoms that mirror
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