Parkinson’s disease is a chronic progressive neurodegenerative disorder affecting millions of people all over the world. It is caused by the lack of neurotransmitter dopamine in the brain. This neurotransmitter is responsible to control the part of brain incharge of the control movement, emotional response and the ability to feel pleasure and pain. The deficiency of dopamine act synergistically with the increase in the amount free radicals in the body and bring about the physical manifestation of the disease.
The symptoms might appear anytime, but majority of the patients affected are usually above 50 years and rarely below 30 years of age. Although the characteristic symptoms of Parkinson’s disease (PD) involve motor functions such as tremor, rigidity, slowness of movement and loss of postural reflex, there are other neurological and psychiatric symptoms present in later stages of the disease which point to definite changes in brain function and personality of PD patients.
Cognitive Abilities in Parkinson’s Disease
Cognition relates to higher level functions of the brain and may be defined as the mental process involved in gaining knowledge and understanding, which includes the process of thinking, knowing, learning, remembering, decision making, judging and problem solving. Language, imagination, perception and planning are the necessary components.
People with PD often have trouble processing two cognitive acts simultaneously. Mild cognitive impairment may be present in most people with PD. Stress, depression, sleep disturbances, or medication can lead to such changes. Not only the dopaminergic pathways but also other pathways associated with the emotion and cognition such as the serotonergic, adrenergic, cholinergic, and frontal dopaminergic pathways are also variably destructed in the Parkinson’s disease.
Many non-motor aspects of Parkinson’s disease includes depression, impulsive control disorders, drug induced psychosis, anxiety, sleep disturbances, and cognitive impairment. Cognitive disturbances, as well as mood and behavior alterations, can be as traumatic and frustrating as any physical problem, both for the patient as well as the caregiver. They even complicate the clinical management of the disease and are responsible for the poor quality of life for the patients and financial burden on their care-givers.
Cognitive deficits can be present even in the early stages of Parkinson’s disease, gradually worsening as the disease progresses, and may ultimately lead to dementia. A person with PD is at a greater risk of developing dementia and this risk gradually increases in proportion to the duration of the disease. The cognitive deficits seen in PD patients (subcortical dementia) are similar to those caused by frontal lobe damage. Due to the degeneration of the cells of the part of the brain known as substantia nigra in the basal ganglia, there is deficiency of the chemical transmitter dopamine. As a result, there is dysfunction of the circuits connecting the frontal lobe of the brain and the basal ganglia, causing problems with memory, language, concentration, attention, visuo-spatial functions, and executive function of the brain.
Depression in Parkinson’s Disease
Depression is the most common neuropsychiatric disturbance in Parkinson’s disease affecting about 40% of the patients. It is particularly crucial as it is associated with a higher rate of progression of the symptoms, greater decline in the cognitive skills, leading to a poorer treatment compliance and quality of life and increase in the financial burden on the caregiver. It has also been researched that as compared to the motor disability in Parkinson’s patients, depression has been found to be a more sensitive predictor of the overall disability of the affected individual.
Poor sleep, decreased energy, lack of concentration and psychomotor retardation are seen in almost all the patients of Parkinson’s disease and the cluster of these symptoms are used to make the diagnosis of depression. The etiology of depression in Parkinson’s patients is multifactorial. While many patients are thought to be demoralized about suffering through the serious and progressive illness, on the other hand other factors have also been investigated which include the examination of level of neurotransmitters levels in the cerebrospinal fluid, neurological examination and neuroimaging techniques with PET scan. These diagnostic methodologies have come to the conclusion that the patients of Parkinson’s disease have depression because of the damage to the serotonergic system as well as to the dopaminergic basal ganglia-limbic-frontal system which are predominantly involved in the mood regulation and in the feeling of pleasure and general well being.
The treatment for depression in Parkinson’s patients involve the use of nortriptyline and paroxetine antidepressants. It has also been established that the management of depression leads to a generalized improvement in the quality of life, sleep pattern and certain aspects of cognition in such patients. However the inter-individual differences in response to various medications and the patient’s tolerability must also be kept in mind. It has been scientifically studied that there is a slight worsening of the motor symptoms in Parkinson’s disease with the use of SSRIs antidepressant drugs. Also there has been a study to indicate a potentially serious interaction between the monoamine oxidase B inhibitors antiparkinsonian drugs with the antidepressant drugs. Having said that, it has been well concluded in various reports that the electroconvulsive therapy (ECT) is an effective treatment of the different patients in PD as in most of the cases it improves both the mood and the motor symptoms of the patients. Also, the patients must be encouraged to exercise, participate in local group discussions, and to keep up their social activities
Memory Loss in Parkinson’s Disease
Anything that affects cognition can affect memory too. However, sometimes it becomes difficult to differentiate memory loss or impairment due to PD from that due to normal aging process.
Subcortical cognitive deficits, as seen typically in PD patients, are characterized more by problems with memory recall (especially of recent events) than by memory formation, decrease in mental speed or slowed thinking (bradyphrenia), and apathy. It is not that PD patients suffering from bradyphrenia are unable to think. It is only that their thinking process is slow, so they need time to answer questions or make decisions.
Executive impairment may be more pronounced than language deficit. Executive functions involve higher level thinking skills such as logical thinking, prioritizing, organizing, planning, and executing. Dementia may be accompanied by psychosis, agitation, and sleep disturbances.
Personality Changes in Parkinson’s Disease
Personality changes occur frequently in people with PD. The caregivers of the Parkinson’s patients are frequently heard saying that “Parkinson’s has made their relatives different, that something has discernibly altered their loved ones.” Frontal cortical damage could account for some of the behavioral and personality changes that are seen in PD patients, such as depression, mental lethargy, mood swings, and irritability. On the other hand, obsessive compulsive behavior such as binge-eating, hypersexuality, and pathological gambling may be related to some drugs used to treat PD. The constellation of such traits are collectively called as Parkinson’s personality
A Parkinson’s personality is often mentioned in relation to PD patients. Certain personality traits have been noted in people with PD which includes being hard-working, ambitious, serious-minded, dogmatic and honest. They are less likely to have any addictions to alcohol, tobacco or drugs. These traits may be present even before the development of PD. One theory that may explain this is that loss of dopamine (which is thought to be responsible for these personality traits) starts long before the manifestation of motor symptoms.
It must be kept in mind that the Parkinson’s disease is the result of the deficient dopamine in the brain and it is not at all the fault of the patient that he/she is no longer the same individual as before the diagnosis of the disease. This fact is important to the families challenged by the Parkinson’s in regard to the financial and emotional stability of the caregiver. The biggest source of conflict in the families arises when the caregivers are unfair to the person with the brain insult. It is important for the families to articulate their feelings that the person has now changed and that they must have strength in optimism, hope for the progress, and provide immense love and support to the affected individual.