Review of The Parasomnias and Other Sleep-Related Movement Disorders by Michael J. Thorpy and Giuseppe Plazzi

Have you ever imagined getting rid of your in-laws once and for all? What if you awoke one morning to find that while you were asleep, you drove 14 miles to your in-laws home, bludgeoned your mother-in-law, strangled your father-in-law until he passed out, and then stabbed them both with a kitchen knife (Broughton et al. 1994) As hard as it may be to believe, these are actual real-life events. Sleep-related crimes such as this, albeit rare, do occur, and individuals who perform such acts have been acquitted based on the evidence that they were not conscious, not responsible, and, therefore, not guilty. Now, envision yourself as a 60-year-old who awakens from sleep with the daunting realization that you are punching your beloved partner of many years in the face. Moments before, you were dreaming of being attacked by a group of “thugs” robbing you. Lastly, picture yourself as a parent who is jolted awake by the blood-curdling screams of your 3-year-old boy. When you frantically arrive at the bedside, he is disoriented, but to your surprise, he suddenly stops screaming and returns to sleep as if nothing had happened. In the morning he has no recollection of the event. These above scenarios are examples of sleepwalking, dream enactment related to rapid eye movement (REM) behavior disorder (RBD), and sleep terrors, respectively, all classified as parasomnias. The book Parasomnias and Other Sleep-Related Movement Disorders, edited by Michael Thorpy and Giuseppe Plazzi, two prominent sleep researchers, gives a comprehensive review of these disorders.

For individuals who experience such events, and to those closest to them, parasomnias can have profound and long-lasting consequences. Moreover, parasomnias are common disorders, especially in children, and are often associated with specific diseases as sleep apnea. Sleepwalking affects 2–5% of young adults (Ohayon et al. 1999) and RBD affects 0.4–0.5% of the general population, but is reported as high as 58% in patients with Parkinson's disease (Iranzo et al. 2009). The International Classification of Sleep Disorders (ICSD) defines parasomnias as unpleasant or undesirable behaviors or experiences (such as nightmares) that occur predominantly or exclusively during sleep, and combines together 15 very diverse disorders such as sleepwalking, sleep terrors, RBD, nightmares, enuresis, and sleep starts (American Academy of Sleep Medicine 2001).

The term “parasomnia” derives from the Greek prefix “para” meaning “around” and Latin “somnus” meaning sleep. It was coined in 1932 by the French researcher Henri Roger and contrasted with dyssomnias: disorders of sleep affecting amount or timing of sleep, such as insomnia. Although the term is recent, reports of parasomnias go as far back as the time of Hippocrates, and have been artfully utilized in literature and later in movies. For example, both Shakespeare and Cervantes afflicted some of their most prominent characters, such as Lady Macbeth and Don Quixote, with parasomnias. The first is represented during an infamous sleepwalking episode “You see, her eyes are open.” “Ay, but their sense is shut.” Don Quixote is represented while enacting his dreams of fighting unreal enemies in his sleep (Furman et al. 1997; Iranzo et al. 2004). Hitchcock used nightmares in many of his movies, and in the recent major motion thriller, Side Effect, sleepwalking was an intricate backdrop of the plot. Undoubtedly, popular culture has been fascinated with parasomnias, as the occurrence of complex behaviors without complete awareness puzzles us and raises questions about consciousness and responsibility. Moreover, and more seriously, these disorders have important medical-legal implications for physicians or therapists, because individuals who have parasomnias occasionally may engage in dangerous or violent behaviors, including aggression, homicide, or self-injurious behavior.

Parasomnias and Other Sleep-Related Movement Disorders consists of 33 chapters, organized into six sections. The target audience is sleep disorder specialists and sleep researchers, but the text can be of interest to a broader audience, including neurologists and psychiatrists. The editors reached their stated goal, as this text “provides a comprehensive and authoritative guide for clinicians that is presented in a manner which is both readable and easily understood.” Although the main focus of the book is parasomnias, it also devotes significant space to connected topics such as sleep-related movement disorders and sleep-related epilepsy.

Scientifically, many questions remain open, although research on parasomnias has dramatically increased over the last 20 years, as demonstrated by the growth in publications; only 32 articles were published in 1990 on the topic compared with 411 in 2009. As this book explains, current research has focused on the mechanisms behind parasomnias and their relationship with other medical disorders such as obstructive sleep apnea or neurological diseases. Especially noteworthy is the association between RBD and neurodegenerative disorders such as Parkinson's or dementia with Lewy bodies. Specifically, RBD appears to precede the onset of these diseases, sometimes by decades.

The introductory section of Parasomnias and Other Sleep-Related Movement Disorders is informative, covering general topics including neuroimaging, epidemiology, and clinical evaluation. Both the clinical evaluation and the video-polysomnography chapters provide detailed information on how to differentiate parasomnias from other disorders through history, physical examination, and, if necessary, a sleep study. Furthermore, the polysomnography chapter includes important yet often-neglected details such as the type of digital recording device required and recording parameters. Although some of this information might be obvious to the sleep specialists, it is extremely helpful for clinicians from other disciplines who can visualize the setup of a polysomnography. Overall, the illustrations, tables, and pictures are just one of several strengths of this book. Sleep specialists, particularly, will appreciate the numerous polysomnographic fragments/epochs shown that clarify phenomena described in the text.

The sections on parasomnias have three main categories: Disorders of arousals (occurring in NREM sleep; e.g., sleepwalking, sleep terrors, and confusional arousal); parasomnias associated to REM sleep including RBD and nightmares; and other parasomnias, for example sleep enuresis or sleep-related eating disorder. Although sleep-related movement disorders and sleep-related epilepsy are not classified as parasomnias, they often enter into the differential diagnosis and are therefore included. The presence of these additional disorders along with detailed descriptions of the rarer parasomnias is a strength of the book, as it provides the kind of concise, in-depth reviews usually only found in scientific journals. Specifically, the chapters on fragmentary myoclonus, propriospinal myoclonus, cathatrenia, and sleep-related leg cramps, are particularly noteworthy.

Although this book has a number of strengths, there are a few limitations. First, as happens with chapters written by various authors with varying styles, sometimes there are repetitions among chapters, and some chapters are not completely homogeneous with the rest of the work either in angle or style used. Second, despite the book's strength of providing a review of many often-uncovered areas, some chapters on major conditions could elaborate more on subtopics, even if that would, perhaps, be difficult within the space available. Lastly, a few chapters recapitulate the research in a list-like manner rather than providing a cohesive opinion, leaving the reader without the expert's definitive conclusions.

Parasomnias are common disorders, often overlooked, and with potentially serious consequence. This book provides much needed, enjoyable reading on the subject, covering major and common disorders with enough depth for sleep medicine novices but also offering intriguing information on rarer, often neglected conditions for more expert readers.