James Parkinson was the first to describe Parkinson’s disease (PD) in 1817; he described it as a combination of tremor, rigidity, postural abnormalities, and bradykinesia.

Parkinson's disease is a progressive neurological disorder characterized by the preferential loss of dopaminergic neurons in the substantia nigra, which project to the striatum.

Parkinson's disease (PD) is a neurodegenerative disease involving the basal ganglia, resulting in motor and extra-motor deficits. These extra-motor deficits may be reflective of a self-regulatory deficit impacting patients' ability to regulate cognitive processes, thoughts, behaviors, and emotions.

With advances in knowledge disease, boundaries may change. Occasionally, these changes are of such a magnitude that they require redefinition of the disease. In recognition of the profound changes in our understanding of Parkinson's disease (PD), the International Parkinson and Movement Disorders Society (MDS) commissioned a task force to consider a redefinition of PD.

Several critical issues were identified that challenge current PD definitions. First, new findings challenge the central role of the classical pathologic criteria as the arbiter of diagnosis, notably genetic cases without synuclein deposition, the high prevalence of incidental Lewy body (LB) deposition, and the nonmotor prodrome of PD. It remains unclear, however, whether these challenges merit a change in the pathologic gold standard, especially considering the limitations of alternate gold standards. Second, the increasing recognition of dementia in PD challenges the distinction between diffuse LB disease and PD. Consideration might be given to removing dementia as an exclusion criterion for PD diagnosis. Third, there is increasing recognition of disease heterogeneity, suggesting that PD subtypes should be formally identified; however, current subtype classifications may not be sufficiently robust to warrant formal delineation. Fourth, the recognition of a nonmotor prodrome of PD requires that new diagnostic criteria for early-stage and prodromal PD should be created; here, essential features of these criteria are proposed. Finally, there is a need to create new MDS diagnostic criteria that take these changes in disease definition into consideration ¹⁾.

see Parkinson's Disease Dementia

Current subtype classifications may not be sufficiently robust to warrant formal delineation.

see also Tremor predominant Parkinson's disease.

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease.

Typically, people with Parkinson's disease receive the diagnosis in the sixth or seventh decade of life. Age is the most important risk factor for the disease, and it has been estimated that 1 to 2% of people older than 60 years of age are affected.

see Parkinson's disease etiology.

see Parkinson's disease pathophysiology.

see Parkinson disease clinical features.

Diagnosis largely depends on clinical observation, but motor dysfunctions do not emerge until 70%-80% of the nigrostriatal nerve terminals have been destroyed. Therefore, a biomarker that indicates the degeneration dopaminergic neurons is urgently needed.

DTI and the apparent transverse relaxation rate provide different but complementary information for different parkinsonisms. Combined DTI and apparent transverse relaxation rate may be a superior marker for the differential diagnosis of parkinsonisms ²⁾.

see Parkinson's disease treatment.

Axial motor signs-including gait impairment, postural instability and postural abnormalities-are common and debilitating symptoms in patients with advanced Parkinson disease. Dopamine replacement therapy and physiotherapy provide, at best, partial relief from axial motor symptoms.

The degree of clinical improvement achieved by deep brain stimulation (DBS) is largely dependent on the accuracy of lead placement.

see Parkinsons Disease Questionnaire.

see Parkinson's disease case series.

Listik et al. from the University of São Paulo describe a rare situation in which both essential tremor (ET) and PD coexist in a 72-year-old male referred for zona incerta ZI-DBS due to refractory tremor. The aim of this study was to evaluate whether there was a difference in the area stimulated to improve each type of tremor and whether tractography could improve and predict motor outcome.

Two months after the surgery, in order to define which of the cathodes was the most effective towards improving the tremor and parkinsonian symptoms, a double-blinded, monopolar evaluation was conducted on both hemispheres separately. Once the best contact and parameters were defined, the volume of tissue activation (VTA) was represented spatially for each type of tremor and, finally, the image model was fused with the tractography.

For both types of tremor, the hot spot stimulated region achieved the dentato-rubro-thalamic tract (DRTT) at the higher fiber density region. The DRTT fibers were asymmetrical between the right and left hemispheres.

Regardless of the type of tremor, DRTT can be the most effective region for stimulation. Tractography should be considered when planning the surgical target since the DRTT is not always symmetrical, and the reconstruction of the VTA together with the tractography can greatly improve the DBS programming, and, probably, the patient's outcome to the stimulation ³⁾.

A 38-year-old male with Parkinson's disease developed intractable hemiballism in his left extremities due to a small lesion that was located adjacent to the right deep brain stimulation (DBS) lead, 10 months after bilateral subthalamic nucleus (STN)-DBS placement. He underwent a right globus pallidus internus (GPi)-DBS lead implantation. GPi-DBS satisfactorily addressed his hemiballism.

This case offered a unique look at basal ganglia physiology in human hemiballism. GPi-DBS is a reasonable therapeutic option for the treatment of medication refractory hemiballism in the setting of Parkinson's disease ⁴⁾.