One of the most common neurodegenerative diseases; it especially affects motor skills.
Parkinson’s is the most common neurodegenerative disease after Alzheimer’s. It is estimated that approximately 1% of people over 60 years of age suffer from this disorder.
Although it is believed that Parkinson’s disease has genetic causes and therefore can hardly be prevented or cured, there are treatments capable of alleviating its symptoms and delaying the physical and cognitive deterioration that it entails, especially medications such as levodopa.
What is Parkinson’s disease?
Parkinson’s disease affects regions of the brain that produce dopamine, a neurotransmitter that allows for voluntary and precise (fine) movement in addition to other non-motor functions.
The main symptoms of this disease, described by James Parkinson in 1817, include tremors at rest, muscle stiffness, and impaired speech and gait.
Parkinson’s usually begins between the ages of 50 and 60, although it is not uncommon for it to begin after the 30s. The course of this disease is chronic and usually causes severe disability in the person who suffers it after about 10 years.
Although some treatments can alleviate symptoms, once Parkinson’s disease develops there is no cure.
Causes of this pathology
Parkinson’s symptoms are a consequence of the degeneration of subcortical brain structures. The destruction of dopaminergic neurons in the basal ganglia, especially in the region known as the “substantia nigra”, hinders multiple cognitive and motor functions.
The causes of Parkinson’s disease are unknown. It is known that there is a genetic component, since 15% of the people diagnosed have close relatives who also suffer or have suffered from this disorder.
The development of Parkinson’s is probably due to the combination of mutations in several genes. Exposure to some toxins, such as those present in pesticides, herbicides, and heavy metals, is also considered a risk factor, although the importance of these environmental factors seems less than that of genetic ones.
The first symptoms of Parkinson’s disease usually include slight tremors that progressively intensify. The same happens with the rest of the symptoms, which are also related to movement.
Other early signs are stiff arms when walking, difficulty articulating sounds, and lack of facial expressiveness (the “mask face” characteristic of this disease).
Subsequently, all these symptoms will worsen as the degree of cerebral involvement increases, evolving in many cases until the diagnosis of dementia caused by Parkinson’s disease.
1. Resting tremors
Tremors at rest are slow and wide and occur in a part of the body that is not making any movement. They are very characteristic of Parkinson’s disease, to the point that in many cases they are called “parkinsonian tremors”.
They usually start in one of the hands, but as the disease progresses they spread to both arms and can also affect the legs and head.
In general, tremors at rest occur together with muscle stiffness and motor slowness, and occur to a lesser extent during voluntary movements.
2. Muscle stiffness
The increased muscle tone that occurs as a result of Parkinson’s disease in turn leads to muscle stiffness, which limits movement and causes pain.
A characteristic of Parkinson’s is what we know as “cogwheel rigidity”, consisting in that when another person moves the patient’s affected limbs, they stop, showing excessive resistance, as if there were something that locks the joints. However, the problem is not in the joints, but in the muscle activation patterns that the nervous system commands in real time.
3. Bradykinesia (motor slowness)
Parkinson’s disease progressively hinders movements, especially those of the extremities. This decreases the ability to carry out simple manual tasks, which are being performed more and more slowly. It also makes it harder to get up and walk.
On the other hand, the difficulties caused by these motor difficulties also mean that there is little willingness to move, which is why a psychological effect is added to the motor symptoms that overlaps with the above.
4. Loss of automatic movements
The involvement of the basal ganglia causes a progressive loss of automatic movements in people with Parkinson’s. This is manifested in the absence of blinking, smiling and swinging the arms when walking.
5. Posture and balance problems
In Parkinson’s disease, postural reflexes are affected, giving rise to a stooped and flexed posture that in turn causes lack of balance or postural instability, facilitating falls and making movement more difficult. In addition, in the case of falls, avoiding falling to the ground with all the weight and then getting up also costs more.
6. Impairment of gait
One of the most visible consequences of the motor problems we have mentioned is gear changes. People with Parkinson’s typically take shorter steps, drag their feet, and move their arms less when walking.
Difficulties occur in all phases of gait, so that not only does walking become more difficult, but the ability to start, turn, and stand is also impaired.
7. Speech difficulties
Some of the most common speech problems in Parkinson’s cases are decreased volume and difficulties in pronouncing, derived from motor impairments in the articulatory organs.
Likewise, prosody is altered, speech can accelerate (tachyphemia) and some words and phrases can be repeated compulsively (palilalia). These symptoms appear to be more frequent in cases where Parkinson’s disease is associated with dementia.
As a consequence, the social life of the person is damaged, and sometimes it predisposes them to seek isolation.
The alterations that Parkinson’s causes in the brain can cause a specific form of dementia of this disease to develop .
Dementia is diagnosed in 20-60% of Parkinson’s cases, although a lower degree of cognitive impairment may also occur in the rest. Dementia caused by Parkinson’s disease is especially likely if the patient is male, old, late-onset, or does not respond well to medication.
Compared with Alzheimer’s disease, the most common cause of severe cognitive impairment, in Parkinson’s dementia, motor disturbances are more relevant at the beginning. This is due to Parkinson’s own dopamine deficiency. In contrast, cognitive symptoms are more intense in the early stages of Alzheimer’s.
However, as Parkinsonian impairment progresses, cognitive symptoms such as memory loss and delusions increase. The different types of dementia differ less between them when they are in an advanced stage.
Prevention and treatment
It is not clear whether the onset of this disease can be prevented. Some studies suggest that consuming caffeine and green tea reduces the risk of Parkinson’s.
In addition, the practice of moderate intensity aerobic exercise in adulthood has been associated with a lower probability of developing this disease in old age. However, for the moment it has not been possible to confirm the preventive efficacy of sport, and the same happens with caffeine and green tea.
Once Parkinson’s disease has developed its symptoms can be alleviated using different types of treatment. The management of this disorder is carried out mainly with medication that increases the levels of dopamine in the body.
Levodopa is the most widely used drug to treat Parkinson’s, especially in its early stages. This compound increases the concentration of dopamine. As the disease progresses, levodopa may lose its effectiveness, in which case it is replaced by dopamine agonists such as pramipexole and ropinirole.
Other forms of treatment, such as surgery, are less effective than levodopa and similar drugs. Physical exercise and relaxation techniques also help maintain mobility to a greater extent, slowing the progress of Parkinson’s disease.