Unveiling the less explored side of Parkinson's disease

Abstract

Although only recognised in very few studies, non-motor symptoms (NMS) are one of the most disabling aspects of Parkinson's disease, often outweighing the burden of dyskinesias and substantially affecting quality of life of patients, as well as precipitating hospitalisation. NMS include dementia, depression, apathy, constipation, pain, genitourinary and gastrointestinal problems, and sleep disorders. Unfortunately, these symptoms are generally under-reported and are overshadowed by the more prominent report of motor symptoms. Chaudhuri, Tolosa, Schapira, and Poewe have edited a book with more than 60 co-authors and 29 chapters to update and review NMS in Parkinson's disease. After an introductory review on the topic, the first three chapters address NMS according to different stages of disease. Starting with the premotor stage, the authors describe symptoms that are considered premonitory of the diagnosis, subsequently discussing those observed during the early stages and ultimately those that appear during the final or advanced stages. The next two chapters deal with diagnosis of NMS by use of current scales and imaging techniques. In addition to reviewing diagnostic tools for NMS, these chapters offer interesting material on current hypotheses underlying the pathophysiology of such symptoms, a topic that I would have liked to have seen discussed more thoroughly in the chapter on NMS and premotor diagnosis later in the book. Several chapters individually outline different NMS, with two chapters that review the effect of deep brain stimulation on these symptoms and fluctuations of these symptoms that are associated with antiparkinsonian medication. Treatment-related NMS are also included here, as is a separate chapter on impulse control disorders and dopamine dysregulation syndrome. Focusing on NMS in this way has enabled the editors to put together a most comprehensive review. When reading the book from beginning to end, this approach induces certain overlap in content between the first four chapters and later ones dedicated to a particular symptom. However, this approach is very helpful in terms of consultation on specific NMS issues, and the wide range of topics covered widens readers' interest to include not only movement disorders specialists but also the general practitioner. The chapter on NMS and the genetic forms of parkinsonism is novel, with a large batch of new material that I found particularly enjoyable reading. More than 350 papers are reviewed, suggesting that the number of cases of NMS in genetic forms of Parkinson's disease might be lower than sporadic forms, with some exceptions. These include dementia in the parkinsonism caused by the mutation in ATP13A2, psychiatric disorders caused by the mutation in PINK1, and the well known preservation of the sense of smell in patients with mutations in PARK2. However, following the intuitive outline of the text as a whole, this chapter would perhaps have been better placed at the end of the book. The work is fully referenced and contains more than 60 well-considered tables with excellent summaries of most clinically relevant information, helping the reader to rapidly consult key chapter facts. The introduction and purpose of a second order of tables outlined as boxes was not as clear to me. Initially, I thought that these boxes were intended for the display of take-home messages, accepted clinical criteria, or clinical vignettes but, in the end, the authors mixed together all kinds of different information. As a minor point, seborrheic dermatitis is mentioned on only three occasions throughout the book; bearing in mind that this symptom affects a substantial number of patients, this sign should have deserved a little more attention. In my opinion, this book is an enjoyable read and represents a great effort and an important addition to increasing awareness of the long list of NMS that burdens patients with Parkinson's disease.