Sleep Diseases

Abstract

In the last four decades, sleep medicine has made spectacular steps of advancement, shifting from a complementary branch of clinical psychophysiology to an autonomous and multidisciplinary specialty. This qualitative leap has been enhanced by the availability of equipment able to distinguish waking from sleep and within the latter REM periods from non-REM (NREM) stages. Furthermore, polysomnography, that is, the simultaneous recording of electrical signals collected from the brain, muscles, and autonomic functions, has allowed to correlate the neurophysiological states to the oscillations of biological activities, quantifying respiratory pauses, limb jerks, and abnormal behaviors and placing them in relation to states of consciousness and vigilance. This is how surprising pathologies have been identified, such as REM behavior disorder, sleep-related hypermotor epilepsy, parasomnias, nocturnal myoclonus, and sleep apneas. Imagine a subject who, while awake, has a regular breathing and perfectly compensated O2 saturation levels and that as soon as he falls asleep, sometimes even in the middle of the day, begins to emit a periodic noise from his mouth (snoring) alternating with prolonged and repetitive phases of respiratory silence (apneas). Events that are almost exclusively associated with the stages of light sleep tend to disappear in the deeper NREM stages and perhaps reappear, longer and disordered, coinciding with REM sleep. A symphony of musical times (allegro, lento, andante con moto) previously unknown or impossible to decipher due to the lack of an objective measurement code. The technological evolution has accelerated in an impressive way the possibility of collecting and analyzing large masses of data, but also the electronic miniaturization has played a decisive role in making easy and rapid the execution of polysomnographic and cardiorespiratory examinations both in the laboratory and at home with portable systems. In parallel, the cognitive boundaries of pharmacological and prosthetic therapy have broadened, definitively conferring a complete clinical status on sleep medicine. Although sleep medicine is considered the child of a minor god, it has managed over the years to produce a complex nosographic corpus with almost 90 clinical entities collected in the international classification (ICSD-3) (American Academy of Sleep Medicine. International classification of sleep disorders, 3rd ed. Darien, IL: American Academy of Sleep Medicine, 2014). This chapter cannot be exhaustive on all coded pathologies but will try to highlight the role of EEG and polysomnography in understanding the pathophysiological mechanisms of the most common and relevant sleep disorders with indications also on the action of drugs and non-pharmacological treatments.