Parkinson's disease

Parkinson's disease is one of the most common neurodegenerative diseases. It is characterized by the presence of resting tremor, slowness of the voluntary movements (also known as bradykinesia) and muscular hypertonia (rigidity). The disease is named after James Parkinson, a British doctor that is the first to describe the symptoms. 

Causes and risk factors
The cause for Parkinson disease is yet unclear. Currently, it is considered that Parkinson's disease is the result of degeneration of the substantia nigra. This is a structure within the brain, composed mainly by neurons that operate with the neurotransmitter dopamine. Several factors are likely to involved in the etiology of Parkinson's disease:

• Genetic factors - genetic researches validate the existence of nine different specific genetic defects, which are associated with the development of the disease in families with a particularly high incidence of the disease.

• Family history- in about one fourth of all patients with Parkinson's disease is established family history of the disease.

• Oxidative stress - the body contains many antioxidants, which role is to eliminate free radicals, formed during different chemical reactions. Glutathione is for example a powerful antioxidant. The decrease in its levels is the earliest biochemical marker for degeneration of neurons in substantia nigra, even in the preclinical stage of the disease

• Imbalance of neuromediators- dopamine deficiency, with relative prevalence of acetylcholine. Decreased levels of noradrenaline, serotonin or GABA could also be observed. 

• Toxic factors - Over 100 toxic agents that could damage the dopaminergic neurons in substantia nigra have already being identified. However, scientists consider that their role in Parkinson's disease genesis is minor.

Men are more likely to develop Parkinson disease. The condition usually starts around age 60 and its prevalence increases with age. 

Symptoms
Parkinson's disease develops slowly and gradually and starts with atypical symptoms such as shoulder pain, numbness, clumsiness. With the evolution of the condition, four cardinal symptoms are formed:

• Static tremor (tremor at rest) - in 70% of patients this is the first clinical sign. Typically begins from the hand and affects only one of the hands. The tremor has a frequency 3-7Hz. It is rhythmic and disappears during movements and sleep. It could intensify from emotional stress. Over time it may spread to the whole arm, leg, contralateral limbs.

• Rigidity - increased muscle tone of different muscle groups. It  could be detected during passive muscle movements examination, when constant resistance is felt.

• Bradykinesia - slow voluntary movements, difficulty in initiating and implementing automated movements. Clinical manifestations of bradykinesia also include loss of spontaneous facial expression- "mask face", reduced frequency of blinking, hypophonia ( very weak voice), monotonous speech, reduced to missing physiological synkinesis (for example shaking hands when walking), loss of normal gestures, reduced amplitude of movements. The handwriting becomes slow, with small letters.

• Postural instability. Patients experience a change in posture with flexion of the head and the body with hands close to the body, bent at the elbow joints. The gait becomes slow, the steps are small. The patient experiences troubles while starting to walk or turning around.

• About half of patients develop a number of additional symptoms that are considered as secondary. These include cognitive impairment, dementia, in which it is necessary to make a differential diagnosis of Alzheimer's disease and progressive supranuclear palsy. Troubles with the autonomic nervous system such as orthostatic hypotension, constipation, urinary and sexual dysfunction may also appear. 

Diagnosis
The diagnosis of Parkinson disease usually takes time as there are no specific tests to confirm or reject it. That's why if you have any of the symptoms enumerated above, your condition must be reviewed by a neurologist. After physical examination and depending on your medical history, he may order some blood or imaging tests (such as MRI) to exclude other diseases. Your doctor may also prescribe Levodopa- a drug used for Parkinson treatment. Eventual improvement of your condition will confirm the diagnosis.

Treatment
No definitive treatment is available. Left uncured Parkinson's disease leads to permanent disability. However medications can seriously limit the symptoms. Your doctor may prescribe:
• Carbidopa-levodopa- Levodopa is a drug that passes into the brain and then transforms into dopamine in order to substitute its decreased quantity. Levodopa is combined with carbidopa, which disturbs the early degradation of levodopa outside the brain.
• Dopamine agonists- medications that imitate the effects of dopamine, although they have different structure
• MAO-B and COMT inhibitors- these drugs block the enzymes that participate in the metabolism of dopamine and therefore prolong its effects
• Anticholinergics- when the quantity of dopamine is decreased, the acetylcholine is relatively increased. That's why drugs that eliminate the acetylcholine may also be prescribed

Apart from the medications, patients should also be advised to change their lifestyle. Appropriate exercise program could improve the patient's motor activity, strength and balance. Suitable sports include walking, swimming, stretching, dancing. Moreover exercises could help manage depression and anxiety that are common issues in people with chronic diseases.