Claudio Aldaz

The situations that are associated with the acts of sleeping and dreaming have not been taken into account by medicine, with the attention that was due to them, until after the second half of the 20th century. Only then, a hasty rescue of lost time begins in the investigation of what happens while sleeping, both healthy and sick.

It has been repeatedly said that sleep is a third of our life. Consequently, we must insist that data about sleep and dream habits and disorders should be routinely incorporated into the medical history of all medical specialties. In this context, the patient's complaint about her sleep or her way of sleeping must be properly addressed. Since doctors are concerned with trying to solve health disorders, we must assume that it is closely related to the variations of two capital states: wakefulness and sleep.

Since always when talking about semiology and the preparation of the clinical history, the good questioning of the patient is hierarchized and in this particular anamnesis is perhaps the main clinical diagnostic tool when it comes to a sleep disorder, because here a good questioning guides At diagnosis, and provides much of the information, but not the physical examination that in most patients with sleep disorders is within normal limits.

Sleep disorders

When understanding sleep pathology, diseases that affect multiple medical specialties, numerous classifications have been proposed; This chapter presents and summarizes the most recent one prepared by the American Academy of Sleep Medicine in 2005.

The classification divides sleep disorders into seven groups depending on the reason for the consultation or main symptom: insomnia, hypersomnias, respiratory disorders , parasomnias, heart rhythm disturbances, abnormal movements and isolated disorders.


It is the repetitive presence of difficulty in falling asleep or maintaining sleep, waking up early, or feeling of poor or restful sleep. All this happens despite having adequate sleep conditions and produces in the patient, at least, one of the following daytime complaints: fatigue or feeling of general discomfort; attention, concentration or memory difficulties; changes in school or work partner performance; mood or character disturbances, drowsiness; propensity to make mistakes at work or driving vehicles; somatic symptoms such as muscle tension or headache; and concerns, obsessions, or fears related to sleep. A first etiopathogenic approach distinguishes between primary insomnia (isolated or in itself) and secondary (manifestation of an organic or mental illness,

The types of primary insomnia are:

  • ACUTE INSOMNIA: It is closely related to an identifiable stressful event. This can be of a psychological, psychosocial, interpersonal, physical or environmental nature. Its duration is usually less than three months, resolving when the stressful event disappears or when the subject manages to adapt to it.
  • PSYCHOPHYSIOLOGICAL INSOMNIA:  It is the conditioned difficulty to fall asleep and / or extreme ease to wake up, for a period of more than a month. It deals with at least one of the following conditions or complaints: anxiety or excessive concern about sleep; Difficulty getting to sleep; intrusive thoughts or inability to cease mental activity that keeps the subject awake and excessive somatic tension in bed, which prevents relaxation and sleep.
  • PARADOXIC INSOMNIA OR PSEUDOINSOMNIO:  It is characterized by a subjective complaint of severe insomnia and of at least one month of evolution. Without daytime repercussion and without being able to objectify a disorder of the same magnitude by means of diagnostic tests, such as polysomnography or actigraphy.
  • IDIOPATHIC INSOMNIA:  It appears during childhood or the first years of youth without a precipitating factor or a justifying cause being recognized. It is a chronic insomnia, of persistent course and without periods of remission.

Types of secondary insomnia include:

  • INSOMNIA DUE TO MENTAL DISORDERS: In this case, insomnia is but one more manifestation of the underlying mental illness and there is a temporary relationship with the mental disorder and it is not uncommon that it appears even weeks before the other psychic symptoms emerge.
  • INSONMIA DUE TO INADEQUATE SLEEP HYGIENE: They are practices that, being under the voluntary control of the person, favor a state of hypertension (consumption of alcohol or caffeine routinely before bedtime; development of intense mental, physical or emotional activities before from lying down or inappropriate light and noise conditions), or prevent a correct structuring of sleep (frequent naps during the day, or large variations in the hours of going to bed or getting up).
  • INSOMNIA DUE TO DRUGS OR TOXICS: Sleep interruption or suspension is related to the consumption of drugs, drugs, caffeine, alcohol or exposure to an environmental toxic. It appears during periods of consumption or exposure and also during periods of withdrawal or withdrawal.
  • INSOMNIA DUE TO MEDICAL PROBLEMS: It is caused by a coexisting organic disease, so it starts with this problem and varies according to fluctuations or changes in its course.

Insomnia Assessment

The choice of complementary tests in insomnia depends on the context

  • The sleep schedule is useful in the initial diagnosis and in the follow-up after cognitive behavioral treatment.
  • The different sleep questionnaires collaborate in the diagnosis of the type of insomnia and associated factors.
  • Psychological tests are always useful in the case of chronic insomnia and circadian disorders.
  • Actigraphy is a simple and objective method of diagnosis.
  • Polysomnography is both an instrument for evaluating the continuity and architecture of sleep and electrophysiological and research records.


In central sleep apnea syndromes, respiratory movement is decreased or absent in an intermittent or cyclical manner. They are included in this subgroup:

  • PRIMARY CENTRAL APNEA: Ventilation and respiratory movements cease simultaneously and repetitively during sleep, causing frequent awakenings with a dramatic sensation of suffocation.
  • CHEYNE-STOKES RESPIRATORY PATTERN: It is characterized by the appearance of at least 10 apneas and hypo-apneas of central origin per hour of sleep, with gradual fluctuation of the respiratory tidal volume.
  • OTHER TYPES OF CENTRAL APNEA: Those that appear in the adaptation period to high altitudes and secondary to drugs or other substances.
  • OBSTRUCTIVE SLEEP APNEA:There is an obstruction to the air flow in the airway, so that despite the existence of vigorous respiratory movements to try to overcome the obstruction, there is inadequate ventilation. This syndrome is defined by the presence of more than 10 respiratory events per hour of sleep consisting of a decrease in flow of more than 90% (apnea) or 50% (hypo apnea) for more than 10 seconds. A frequently associated sign is the intense snoring that usually occurs between or at the end of the apnea. The activity of the dilating muscles of the pharynx is reduced during sleep. A decrease in the area of ​​the upper airway due to an excessive volume of surrounding soft tissue, craniofacial anatomical peculiarities.
  • CENTRAL ALVEOLAR HYPOVENTILATION SYNDROME OR ONDINE SYNDROME: It is caused by a failure in the anatomical control of breathing.


These are the diseases whose main characteristic is excessive daytime sleepiness (SDE)

  • NARCOLEPSIA - CATAPLEXIA OR GELINEAU SYNDROME: Characterized by BDS and cataplexy. The first is manifested by sudden entries of sleep during the day, even in unsuspected situations. Cataplexy consists of a sudden, localized or generalized loss of muscle tone. It is triggered by strong, usually positive emotions.
    Other symptoms typical of this disorder are sleep paralysis, hypnagogic hallucinations, disorganized sleep or automatic behaviors during it. Sleep paralysis characterized by a transient and general inability to move or speak occurs primarily during the sleep-wake transition. Hypnagogic hallucinations occur at the onset of sleep and consist of visual, tactile, or auditory phenomena.
    Narcolepsy without cataplexy and secondary narcolepsy with hypothalamic lesions or paraneoplastic syndromes should also be considered.
  • RECURRENT HYPERSOMNIA: If the main paradigm is Kleine-Levin syndrome, it is characterized by the appearance of 1 to 10 episodes of hypersomnia annually. These can last from a few days to several weeks. It is associated with SDE in hyperphagia, hypersexuality, irritability, aggressiveness, confusion, etc.
  • IDIOPATHIC HYPERSOMNIA: It takes constant SDE throughout the day. Nighttime sleep lasts more than 10 hours with few or no awakenings. Long, non-repairing naps are common. To all this is added a great difficulty to wake up and get up in the morning.
  • SLEEP FAILURE SYNDROME: This is due to chronic sleep deprivation. This is voluntary but not intentional, since it derives from behaviors or social or cultural circumstances that prevent reaching the amount of sleep to maintain adequate vigilance.
  • OTHER HYPERSOMNIAS: they are due to medical pathologies such as Parkinson's disease or hypothalamic lesions, hypothyroidism, hepatic encephalopathy or kidney failure, etc.


  • SLEEP PHASE ADVANCE: Reconciliation and awakening times are early.
  • SLEEP PHASE DELAY: There is a delay of at least 2 hours in the reconciliation and waking times in relation to conventional times.
  • HYPERNICTAMERAL SYNDROME: The rhythm does not coincide with the 24-hour pattern, being longer (frequently in blind people or subjected lto visual sensory isolation).
  • TRANSMERIDIAN JET LAG PER FLIGHT: consists of a mismatch between the endogenous circadian rhythm of wakefulness - sleep and the exogenous pattern of a given geographical area.
  • OTHER CIRCADIAN DISORDERS: Such as that due to rotating shift work, are common in developed societies.


They are conduct disorders or abnormal behaviors during sleep.

    • Confusional awakening characterized by brief confusional symptoms with bradypsychia, disorientation, inattention, amnesia and aggressiveness.
    • Sleepwalking: A sequence of complex behaviors (usually including walking) during the deep sleep phases in the first half of the night.
    • Night terrors: Episodes of crying or screaming that appear suddenly during deep sleep in the first half of the night. They occur with a facial expression of intense fear and with significant autonomic discharge.
    • Rem sleep behavior disorders: Rem sleep muscular atony is replaced by abnormal movements or behaviors acting the person sleep.
    • Isolated sleep paralysis: As in the Rem phase, there can be a complete and brief loss of muscle tone.
    • Nightmares: they are reveries of unpleasant content. They occur in the Rem phase, prevailing in the second half of the night.
  • OTHER PARASOMNIAS are dissociative sleep disorders, enuresis, catatrenia or nightly moan, cephalic burst syndrome, sleep hallucinations, and eating disorders during sleep.


They should not be confused with sleep disorders associated with motor control diseases.

  • INQUIET LEG SYNDROME: Appears in wakefulness, and is characterized by an uncomfortable, sometimes painful sensation in the legs and less frequently in the arms. Patients have an overwhelming and irresistible need to move their limbs to calm this sensation. It worsens at the end of the day, and with rest, making it difficult to fall asleep at the beginning of the night or after waking up at night.
  • PERIODIC MOVEMENTS OF THE MEMBERS: They are rhythmic, slow and prolonged movements (2 to 6 seconds), occur in phase 1 and 2 of slow sleep and generate micro-awakenings.
  • NIGHT CRAMPS: These are sudden, painful, involuntary contractions of one or more lower limb muscles during sleep.
  • BRUXISM: Masseter, pterygoid, and temporal muscle contractions that cause a vigorous closure of the jaw. It can be isolated and sustained (tonic contraction) or repetitive and rhythmic. If it is very intense, it produces the grinding noise known as bruxism.
  • RHYTHMIC MOVEMENTS OR MOTOR RHYTHMS: They are stereotyped, rocking the head (jactatio capitis) or the whole body. They are common in children 1 to 5 years old and are not serious.

Study methodology

The development of technologies and instruments applicable to the study of night's sleep allowed the advancement of research in all possible aspects and in all imaginable normal and pathological situations. Electroencephalography required the incorporation of the polygraphic record to explore not only brain activity, but also respiratory, cardiac and motor activity, functions that undergo very significant changes during sleep and allow clarification of previously unsuspected clinical conditions. In this way, a new modality of the study of night or day sleep, polysomnography, was configured.

The installation of laboratories specially prepared for the study of normal and pathological sleep is one more step in the history of sleep research. The procedure par excellence for the study of sleep is the polysomnogram that consists of the recording of the electroencephalogram (EEG) and of the different physiological activities that occur during sleep and that can be collected in graphic form, electrooculogram (EOG), chin and limb electromyogram (EMG), electrocardiogram (ECG), naso-buccal air flow, thoracic and abdominal excursion, snoring record and oxygen saturation levels among other variables.

The analysis of the dream is based on the examination "epoch" by "epoch". The epoch is defined as a time interval (usually 30 seconds) of a polygraphic plot, to titrate each segment according to the Rechtschaffen and Kales manual in stage 0, 1, 2, 3, 4 and state of movements, in this way the hypnogram of the night or the day is achieved according to the case studied.

Another very useful complementary test, particularly in hypersomnias, is the Multiple Sleep Latency Test, developed from the following postulate: "a subject falls asleep faster when he is more drowsy".

It is recorded for 20 - 30 minutes every 2 hours from 10am in 4 or 5 periods and following nocturnal PSG. Thus, we evaluated the degree of drowsiness in severe, moderate, mild or null, and if there are numbness in paradoxical sleep or REM (useful in diagnosing narcolepsy).

Another simple evaluation technique is full indication actigraphy in the study of circadian disorders. It is an outpatient method for several days and where the patient uses a device similar to a wristwatch that will record the periods of rest and activity of the patient during the 24 hours.

Finally, it can be affirmed that the set of all sleep disorders is wide and diverse. They can be classified according to the reason for consultation or main symptom or according to the predominant physiopathogenic mechanism. Therefore, it is not surprising that there are variations or disagreements between the different proposed classifications and among the experts themselves, and it is almost certain that future classifications will introduce new modifications. All this is only a matter of form. As it is an area that covers multiple and diverse medical specialties, it is logical that discrepancies arise easily and that modifications are proposed more frequently than in other fields of medicine.

The disease groups proposed in the current classification take into account the main symptom. It should also be noted that although the groups seem well differentiated, the association of disorders is not uncommon and it is also possible to classify some of them into several groups.

The current classification facilitates the study and understanding of sleep disorders and should be taken as a diagnostic aid and not as a rigid and definitive classification, being very useful in clinical practice.