Parkinson’s disease (PD) is a slowly progressive neurodegenerative disease caused when a small group of brain cells that control body movements die. This disease was first described by James Parkinson in 1817. The disease occurs in about 1% of the people over the age of 65 years. The peak onset of the disease is in the sixth decade of the life. However young onset Parkinson’s disease is not uncommon. The estimated prevalence rate of PD is approximately 8-22/1000.
What causes Parkinson’s Disease
Although no distinct cause has been determined, Parkinson’s disease is due to gradual loss of cells in an area deep within the brain called substantia nigra, which normally produces a chemical called dopamine. Once produced, dopamine travels to other portions of the brain. One portion called the striatum is the coordination center for various brain circuits. As there is insufficient dopamine in the striatum, the chemical imbalance leads to the symptoms of Parkinson’s disease. Later in the disease, cells in other portion of the brain and nervous system also degenerate. No one knows why this dopamine producing cells die. Scientists are exploring several theories including chemical reactions within the body, exposure to toxic substances and certain genetic factors. A new gene in certain families suffering from Parkinson’s disease known as ” Parkin gene” has been identified to be the positive factor for Parkinson’s disease surgery. However this has been found to be positive in a small group of patients with young onset of Parkinson’s disease. The research is still going on to find out the real cause for Parkinson’s disease in large patient population.
Diagnosis of Parkinson’s Disease
Parkinson’s disease is just one of several neurologic movement disorders that produce similar symptoms. It is important that the physician you are seeing has experience with all of the different disorders that can masquerade as Parkinson’s disease.
The diagnosis of Parkinson’s disease is entirely clinical. It is characterised by tremors, slowness of movements (bradykinesia), stiffness (rigidity), postural imbalance and gait disturbances. In various patients combination of any of the above symptoms can be seen. One of the distinguishing feature of PD from other Parkinson’s like diseases, is its classical response to medical treatment in the early years. According to one estimate, there can be an error of upto 40% in diagnosis when the patient is seen by non-specialist. As there are no radiological (i.e. CT scan, MRI) or blood investigations that can confirm the diagnosis of PD; the onus of diagnosis rests on the physician.
It is very important to make a correct diagnosis. As in some of these diseases, like Progressive supranuclear palsy, Cortioc-basal ganglionic degeneration or Multiple system atrophy; people quickly become totally disabled and the surgical interventions in such cases can be disastrous to say the least.
Criteria for diagnosing Parkinson’s Disease:
Following are similar looking guidelines for diagnosing Parkinson’s Disease, Parkinson’s motor symptoms and diagnostic criteria.
- Tremors at rest
- Loss of postural reflexes
- Flexed posture
- Freezing (motor blocks)
Definite : At least two of these features must be present, one of them being 1 and 2.
Probable : Feature 1 or 2 alone is present.
Possible : At least two of features 3 to 6 must be present.
U. K. Parkinson’s disease Society Brain Bank’s clinical criteria, for diagnosis of probable Parkinson disease.
At least one of the following criteria :
- 4-6 Hz rest tremor.
- Postural instability not caused by primary visual, vestibular, cerebellar, or proprioceptive dysfunction.
Exclude other causes of Parkinson’s disease.
At least three of the following supportive criteria :
- Unilateral onset.
- Rest tremors.
- Progressive disorder.
- Persistent asymmetry affecting side of onset most.
- Excellent response (70% to 100^%) to levodopa.
- Severe levodopa _induced chorea (dyskinesia).
- Levodopa response for 5 years or more.
- Clinical course of 10 years or more.