Update on Parkinson's Disease

It is with great pleasure that we introduce this issue of Seminars in Neurology entitled, “Update on Parkinson's Disease.” The 13 articles contained in the issue represent a comprehensive and state-of-the-art update for the diagnosis and management of Parkinson's disease (PD). The content has been provided from preeminent experts and leaders in the field. Each article discusses a key aspect of PD and places a special emphasis on practical clinical care and an appreciation of the scientific and research facets required to guide complex clinical decision-making. The overarching goal of this issue is to inform and influence the practice of general neurologists. We hope that this issue can also serve as both a stand-alone framework for the care of PD patients for neurology residents and fellows, as well as a useful update for experts in the field of movement disorders.

The first two articles provide the framework for PD and PD management. The first is focused on the rich phenomenology of motor symptoms that occur in PD, and reviews the often underappreciated subtleties of the cardinal motor features. It also addresses the less commonly described motor control abnormalities. We are grateful for the contribution of Dr. Mark Hallett, a leader in the field of movement disorders clinical neurophysiology and one of the foremost experts in movement disorders phenomenology. The second article provides an overview of the diagnosis and management of PD and is authored by Arjun Tarakad and Joseph Jankovic. Together, they expertly synthesize an expansive and complicated topic into a practical and highly readable text that seamlessly moves the reader from the initial diagnosis to the basic principles of treatment.

The topics of the subsequent articles were carefully chosen to focus on specific aspects of PD and its management. We were fortunate that leading experts for each topic agreed to contribute to the issue. Parkinsonian tremor is unique among the motor symptoms of PD; neither does it progress like nor does it correlate with the severity of the other cardinal symptoms of the disease. Rick Helmich and Michiel Dirkx provide an update on the latest theories regarding the pathophysiology of parkinsonian tremor, and together they review the general principles and specifics of tremor management. Patients commonly inquire about the role of genetic testing in PD, and Roy Alcalay and Christine Kim provide a comprehensive and practical review, as well as a discussion of the genetic forms of PD. One important consequence of medical therapy with dopaminergic agents is motor complications, and Eliza Freitas and Susan Fox provide a definitive review of motor fluctuations and dyskinesias, including a classification of the complications and an assessment of the current therapeutic approaches. These authors also give us a peak at emerging therapies.

A bit slower to be fully appreciated in clinical care and in research, the nonmotor symptoms of PD can in some instances be more disabling than the motor symptoms. Umer Akbar, Anelyssa D'Abreu, and Joseph H. Friedman address this topic in a highly useful overview of nonmotor symptoms that spans cognitive, neuropsychiatric, somatic, and behavioral domains. Specific nonmotor symptoms in PD are expertly covered in more detail by Meagan Bailey and Jennifer Goldman, who focus specifically on cognitive impairment; Ron Pfeiffer, who addresses autonomic dysfunction; and Alexander Lopez, Dan Weintraub, and Dan Claassen, who contribute a unique discussion of impulse control disorders and their similarities to other reward-based behavioral disorders.

Adjunctive treatments for PD are covered in the next two articles, with Aparna Wagle Shukla and Irene A. Malaty covering the use of botulinum toxins in the treatment of PD symptoms, and Leonardo Almeida leading a discussion of the use of deep brain stimulation in PD and where the field of neuromodulation for PD is headed.

The final two articles round out this update by addressing common diagnostic pitfalls and PD mimics. Nikolaus McFarland guides the reader through the atypical parkinsonisms and their pathophysiology, pointing out red flags important to differentiating them from PD, and he also reviews the treatment options. In the final article, Kathrin LaFaver and Alberto Espay discuss the importance of the clinical diagnosis in the recognition of psychogenic parkinsonism, an entity that is likely underrecognized and yet critical to avoid potentially harmful and unnecessary treatments.

We would like to thank Dr. Greer for the opportunity to have served as Guest Editors for this issue, and we especially would like to thank the authors who have generously contributed their time and expertise to this endeavor. We are proud of the result of our combined efforts, and we hope that the readers of Seminars in Neurology find this “Update on Parkinson's Disease” helpful in providing the best possible interdisciplinary care guided by and coupled with the best interdisciplinary research.