Parkinson’s disease (PD) is one of the most commonly existing neurological diseases associated with the old age population worldwide. PD is a progressive neurodegenerative disorder and the incidence of it increases significantly with advancing age. It is estimated to be the second most prevalent neurodegenerative disease after Alzheimer’s disease (AD). PD is associated with gradual neurodegeneration of the central nervous system (CNS).
Three major domains for quality of life management in PD are physical, mental as well as social. PD is associated with increased morbidity, mortality, high economic burden, along the declined quality of life.
PD predominantly affects the motor system leading to movement abnormalities. Precise estimation of prevalence is difficult to determine in PD due to the absence of diagnostic accuracy and consistency. Consequently, there is a need for an accurate diagnosis to obtain realistic estimates. According to the World Health Organization (WHO), the mortality rate due to PD will surpass epilepsy and multiple sclerosis by 2030.
Globally, the prevalence of PD ranges from 41 in 100,000 people around the age of 45 years, to more than 1900 in 100,000 above 80 years. About 1 million Americans are affected by PD, with a global estimate of approximately 7-10 million individuals who are affected with PD.
Epidemiologically, in India, there is a lack of homogenous and large-scale epidemiological data on PD. However, a very early study reported a crude prevalence of 14.1 per 100,000 population in the rural areas of Kashmir (Northernmost Indian State). Whereas, a higher prevalence of 27 in 100,000 population was reported from Bangalore (southern part of India). The report also suggests a prevalence of 16.1 in 100,000 population from rural Bengal (eastern part of India). Thus, a crude average of about 20 in 100,000 population can be mentioned as the prevalence in India according to the few accumulated Indian reports.
The symptoms consist of both motor and non-motor impairments during the progression of PD. The classical symptoms are impairment of motor function, which are characterized by the development of:
Slow movements or bradykinesia (slowness of movement)
Gait (a phenomenon defining an individual’s manner of walking)
Non-motor symptoms include sleep disorders, disturbed autonomic function with orthostatic (relating to or caused by an upright posture)
Hypotension, constipation, and urinary disturbances along with a spectrum of neuropsychiatric symptoms
The initial diagnosis of PD relies on three key symptoms of clinical diagnosis namely bradykinesia, tremor, and rigidity. Sometimes postural instability is also seen in patients with PD. Bradykinesia must be one pivotal symptom accompanying at least one of the other two symptoms, either tremor or rigidity, thus defining the prerequisite for PD diagnosis. Another important step in the diagnosis is to exclude symptoms that may indicate other related diseases or conditions such as parkinsonian syndrome which has other neuropathological changes. Thirdly, a good response to levodopa treatment is vital for PD diagnosis.
Thus, these above three criteria are the basis for PD diagnosis. However, other than clinical evaluation, laboratory-based investigations can also lead to a definitive diagnosis of PD. Recently computer-aided diagnosis (CAD) has proven to be more accurate in the diagnosis of PD. It is done in conjunction with the visual evaluation of dopamine transporter (DaT), single-photon emission computed tomography (SPECT), or DaTscan. Reports suggested 98% classification accuracy to distinguish PD from healthy individuals. Recent diagnosis further relies on diagnostic criteria which state that if non-motor symptoms like cognitive symptoms develop within the first year of the emergence of Parkinsonism, then diagnosis requires the presence of Lewy bodies through histopathological assessment. Whereas, the pillar of confirmatory diagnosis is indeed histopathological assessment, with the identification of α-synuclein-containing LBs or Lewy neurites( LN).
The mainstay of PD treatment depends on medications that increase dopamine or mimic its effect on the dopamine receptor. The most effective medication is levodopa, which is paired with carbidopa, a peripheral inhibitor to minimize side effects and maximize therapeutic efficacy.
Further, dopamine agonists such as drugs pramipexole and ropinirole may be initiated in younger patients as they can synchronize in such age group giving fewer side effects. Anticholinergics or Amantadine may be used if the disease modification is associated with controlling tremor symptoms. Selegiline is frequently used as a symptomatic intervention to treat early as well as mild disease symptom relief. Although it is important to note that all such medications can give symptom relief for 3 to 6 years, after that period, in the long run, the disease inevitably progresses to unresponsiveness towards the medications.
Deep brain stimulation (DBS) has currently become the surgical procedure of choice as it leads to a reversible state that does not damage the cerebral area, and the DBS can be altered as the disease progresses. Moreover, psychotherapy, physical exercise, and speech therapies are also important to provide quality of life to PD individuals.