Sunday, June 27, 2010
Parkinson's disease (also known as Parkinson disease or PD) is a degenerative disorder of the central nervous system that often impairs the sufferer's motor skills and speech.
Parkinson's disease belongs to a group of conditions called movement disorders. It is characterized by muscle rigidity, tremor, a slowing of physical movement (bradykinesia) and, in extreme cases, a loss of physical movement (akinesia). The primary symptoms are the results of decreased stimulation of the motor cortex by the basal ganglia, normally caused by the insufficient formation and action of dopamine, which is produced in the dopaminergic neurons of the brain. Secondary symptoms may include high level cognitive dysfunction and subtle language problems. PD is both chronic and progressive.
PD is the most common cause of Parkinsonism, a group of similar symptoms. PD is also called "primary parkinsonism" or "idiopathic PD" (having no known cause). While most forms of parkinsonism are idiopathic, there are some cases where the symptoms may result from toxicity, drugs, genetic mutation, head trauma, or other medical disorders.
Symptoms of Parkinson's disease have been known and treated since ancient times. However, it was not formally recognized and its symptoms were not documented until 1817 in An Essay on the Shaking Palsy the British physician James Parkinson. Parkinson's disease was then known as paralysis agitans, the term "Parkinson's disease" being coined later by Jean-Martin Charcot. The underlying biochemical changes in the brain were identified in the 1950s due largely to the work of Swedish scientist
Arvid Carlsson, who later went on to win a Nobel Prize,. L-dopa entered clinical practice in 1967, and the first study reporting improvements in patients with Parkinson's disease resulting from treatment with L-dopa was published in 1968.
Parkinson disease affects movement (motor symptoms). Typical other symptoms include disorders of mood, behavior, thinking, and sensation (non-motor symptoms). Individual patients' symptoms may be quite dissimilar and progression of the disease is also distinctly individual.
The cardinal symptoms are:
• tremor: normally 4-7 Hz tremor, maximal when the limb is at rest, and decreased with voluntary movement. It is typically unilateral at onset. This is the most apparent and well-known symptom, though an estimated 30% of patients have little perceptible tremor; these are classified as akinetic-rigid.
• Rigidity: stiffness; increased muscle tone. In combination with a resting tremor, this produces a ratchety, "cogwheel" rigidity when the limb is passively moved.
• bradykinesia/akinesia: respectively, slowness or absence of movement. Rapid, repetitive movements produce a dysrhythmic and decremental loss of amplitude. Also "dysdiadokinesia", which is the loss of ability to perform rapid alternating movements
• postural instability: failure of postural reflexes, which leads to impaired balance and falls.
Other motor symptoms include:
• Gait and posture disturbances:
o Shuffling: gait is characterized by short steps, with feet barely leaving the ground, producing an audible shuffling noise. Small obstacles tend to trip the patient
o Decreased arm swing: a form of bradykinesia
o Turning "en bloc": rather than the usual twisting of the neck and trunk and pivoting on the toes, PD patients keep their neck and trunk rigid, requiring multiple small steps to accomplish a turn.
o Stooped, forward-flexed posture. In severe forms, the head and upper shoulders may be bent at a right angle relative to the trunk.
o Festination: a combination of stooped posture, imbalance, and short steps. It leads to a gait that gets progressively faster and faster, often ending in a fall.
o Gait freezing: "freezing" is another word for akinesia, the inability to move. Gait freezing is characterized by inability to move the feet, especially in tight, cluttered spaces or when initiating gait.
o Dystonia (in about 20% of cases): abnormal, sustained, painful twisting muscle contractions, usually affecting the foot and ankle, characterized by toe flexion and foot inversion, interfering with gait. However, dystonia can be quite generalized, involving a majority of skeletal muscles; such episodes are acutely painful and completely disabling.
• Speech and swallowing disturbances
o Hypophonia: soft speech. Speech quality tends to be soft, hoarse, and monotonous. Some people with Parkinson's disease claim that their tongue is "heavy".
o Festinating speech: excessively rapid, soft, poorly-intelligible speech.
o Drooling: most likely caused by a weak, infrequent swallow and stooped posture.
o Non-motor causes of speech/language disturbance in both expressive and receptive language: these include decreased verbal fluency and cognitive disturbance especially related to comprehension of emotional content of speech and of facial expression
o Dysphagia: impaired ability to swallow. Can lead to aspiration, pneumonia.
• Other motor symptoms:
o fatigue (up to 50% of cases);
o masked faces (a mask-like face also known as hypomimia), with infrequent blinking;
o difficulty rolling in bed or rising from a seated position;
o micrographia (small, cramped handwriting);
o impaired fine motor dexterity and motor coordination;
o impaired gross motor coordination;
o Poverty of movement: overall loss of accessory movements, such as decreased arm swing when walking, as well as spontaneous movement.
• Estimated prevalence rates of depression vary widely according to the population sampled and methodology used. Reviews of depression estimate its occurrence in anywhere from 20-80% of cases. Estimates from community samples tend to find lower rates than from specialist centres. Most studies use self-report questionnaires such as the Beck Depression Inventory, which may overinflate scores due to physical symptoms. Studies using diagnostic interviews by trained psychiatrists also report lower rates of depression.
• More generally, there is an increased risk for any individual with depression to go on to develop Parkinson's disease at a later date.[
• 70% of individuals with Parkinson's disease diagnosed with pre-existing depression go on to develop anxiety. 90% of Parkinson's disease patients with pre-existing anxiety subsequently develop depression; apathy or abulia.
• slowed reaction time; both voluntary and involuntary motor responses are significantly slowed.
• Executive dysfunction, characterized by difficulties in: differential allocation of attention, impulse control, set shifting, prioritizing, evaluating the salience of ambient data, interpreting social cues, and subjective time awareness. This complex is present to some degree in most Parkinson's patients; it may progress to:
• dementia: a later development in approximately 20-40% of all patients, typically starting with slowing of thought and progressing to difficulties with abstract thought, memory, and behavioral regulation. Hallucinations, delusions and paranoia may develop.
• short term memory loss; procedural memory is more impaired than declarative memory. Prompting elicits improved recall.
• medication effects: some of the above cognitive disturbances are improved by dopaminergic medications, while others are actually worsened.
• Excessive daytime somnolence
• Initial, intermediate, and terminal insomnia
• Disturbances in REM sleep: disturbingly vivid dreams, and REM Sleep Disorder, characterized by acting out of dream content - can occur years prior to diagnosis
• impaired visual contrast sensitivity, spatial reasoning, colour discrimination, convergence insufficiency (characterized by double vision) and oculomotor control
• dizziness and fainting; usually attributable orthostatic hypotension, a failure of the autonomous nervous system to adjust blood pressure in response to changes in body position
• impaired proprioception (the awareness of bodily position in three-dimensional space)
• reduction or loss of sense of smell (microsmia or anosmia) - can occur years prior to diagnosis,
• pain: neuropathic, muscle, joints, and tendons, attributable to tension, dystonia, rigidity, joint stiffness, and injuries associated with attempts at accommodation
• oily skin and seborrheic dermatitis
• urinary incontinence, typically in later disease progression
• nocturia (getting up in the night to pass urine) - up to 60% of cases
• constipation and gastric dysmotility that is severe enough to endanger comfort and even health
• altered sexual function: characterized by profound impairment of sexual arousal, behavior, orgasm, and drive is found in mid and late Parkinson disease. Current data addresses male sexual function almost exclusively
• weight loss, which is significant over a period of ten years - 8% of body weight lost compared with 1% in a control group
A NIMHANS study concentrated on the ethnic roots of Parkinson's disease. In India, Anglo-Indians are found to be less prone to the disease. While 19.5 per cent of Indians at large have Parkinson's disease, only 4 per cent of Anglo-Indians are affected.
Dr Smita Pandey Bhat
Gurgaon, Delhi - NCR, INDIA
Email : email@example.com
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