Chapter 96 Other Parasomnias
As mentioned in the preceding two chapters, parasomnias may conveniently be divided into two major categories: Primary parasomnias are those due to disorders of sleep per se, and the secondary parasomnias are those that result from dysfunction of other organ systems and that take advantage of the sleeping state to declare themselves. By far, the primary sleep parasomnias are the most common; they are usually the rapid eye movement (REM) sleep behavior disorder if from REM sleep or disorders of arousal if from non-REM sleep. There remains a large group of other parasomnias, many of which are poorly understood, that can cause impressive and distressing activities arising from the sleep period but that are unrelated to disorders of arousal or REM sleep behavior disorder. This last chapter on parasomnias discusses these less-common but fascinating phenomena.
Sleep paralysis likely represents the persistence of REM sleep atonia into wakefulness and is extremely common in patients who are not narcoleptic, occurring in more than 33% of the general population. It may be familial, and it is more common in the setting of sleep deprivation and being in the supine position. When occurring in isolation, it can lead to erroneous diagnoses such as cardiac disease or seizures or to unwarranted psychiatric diagnoses. Rarely, episodes of periodic paralysis arising from the sleep period may be confused with true sleep paralysis. Management is reassurance that this is a normal phenomenon.
Prominent vivid dreamlike mentation can occur at sleep onset, during light NREM sleep, and even during relaxed wakefulness.1 As with sleep paralysis, such sleep onset and sleep offset hallucinatory phenomena are quite common in the nonnarcoleptic population, and they may be combined with sleep paralysis (often referred to as the “old hag” phenomenon).2 As a matter of fact, the original meaning of the word nightmare referred not to the current use of the term (a dream anxiety attack arising from the sleep period) but rather to a combination of sleep paralysis and hypnagogic hallucinations occurring at sleep onset.3 Patients can be reassured that these hallucinations are normal sleep phenomena and not symptoms of psychiatric disease.
Sleep starts are experienced by many normal persons during the transition between wake and sleep. The most common is the motor sleep start, a sudden jerk of all or part of the body, occasionally awakening the victim or bed partner. These are so prevalent as to rarely result in neurologic consultation.4 However, variations on this theme can result in neurologic consultation. These include visual (flashes of light, fragmentary visual hallucinations), auditory (loud bangs, snapping noises) or somesthetic (pain, tingling, floating, something flowing through the body) sleep starts. These sensory phenomena can occur without the body jerk.5
Sleep starts represent a normal (although not understood) physiologic event, and they should not be confused with seizures or other neurologic conditions. Explosive tinnitus, characterized by a loud crashing or banging noise occurring during sleep most likely represents an auditory sleep start.6 It is also likely that the exploding head syndrome (see later discussion) is a variant of a sensory sleep start. Sleep starts may be repetitive, and they should not be confused with epileptic phenomena. Familiarity with nonmotor sleep starts should eliminate unnecessary testing and pharmacologic treatment. There is a single case report of an auditory sleep start associated with insomnia due to a brainstem lesion.7 Management is simply reassurance.
Groaning during sleep has been termed catathrenia (Video 96-1).8 The groans occur intermittently during either REM or NREM sleep and are characterized by prolonged, often very loud, often socially disruptive groaning sounds during expiration. Catathrenia often begins in childhood, but generally it does not come to medical attention until the person plans to sleep in a dormitory environment, such as in college or the military, or when he or she begins to share a bed with another. It is poorly understood, and there is no known effective treatment. Although there have been some reports of a possible relationship with obstructive sleep apnea and response to treatment with nasal continuous positive airway pressure (CPAP), and there have clearly been a number of cases that did not respond to nasal CPAP.9 There is absolutely no evidence that catathrenia is related to any underlying psychological or psychiatric problems.
Enuresis was formerly classified as a disorder of arousal, implying a relationship with slow-wave sleep.10 However, enuresis can occur during either NREM or REM sleep, and the sleep of enuretic children is normal.11 Enuresis is very common in childhood, and it much more prevalent in adolescence and adulthood than generally appreciated (1% to 2% of 18 year-olds and 0.5% of adults).12,13 Many etiologies have been suggested, including genetic,14 behavioral and psychological, bladder size or reactivity abnormalities, lack of vasopressin release during sleep, and delayed development.15 Despite considerable literature, the causes of enuresis remain enigmatic. Local urologic abnormalities account for only 2% to 4% of pediatric cases.16 No specific psychopathology has been identified, and there is overwhelming evidence that enuretic children have no more behavioral or psychological problems than nonenuretic children and that genetic factors are important.17
Formal urologic evaluation is usually not indicated, and simple reassurance and understanding on the part of both the child and the parents are often sufficient. Conditioning with a bell-and-pad device is effective but may be transient.18 Psychotherapy is generally ineffective and indicated only if obvious psychopathology is present.12 Tricyclic antidepressants (imipramine or desipramine) are effective and may be employed for short-term treatment, but long-term pharmacologic treatment is to be discouraged. Their mechanism of action is not known, but it appears not to involve peripheral anticholinergic effects.19 Desmopressin, an intranasally administered vasopressin analogue, has been reported to be of benefit.20
Enuresis may be the sole manifestation of nocturnal seizures and can accompany obstructive sleep apnea or other primary sleep disorders.21 Formal polysomnographic study with a full seizure montage and enuresis detector is indicated in patients with atypical histories or failure to respond to conventional therapy.
Rhythmic movement disorder (RMD), formerly termed jactatio capitis nocturna, refers to a group of actions characterized by stereotyped movements (rhythmic oscillation of the head or limbs, head-banging or body-rocking during sleep) seen most commonly in childhood (Videos 96-2 and 96-3). Its persistence into adulthood is not uncommon. It is familial in some cases. RMD can arise from all stages of sleep, including REM sleep, and it can occur during the transition from wake to sleep.22 Significant injury from repetitive pounding can result.23
The etiology of RMD is unknown, and no systematic studies of pharmacologic or behavioral treatment have been reported, although tricyclic antidepressants and benzodiazepines, particularly clonazepam, may be effective.24 Preliminary data suggest that the use of a waterbed can improve the rhythmic actions,25 as can controlled sleep restriction.26 Hypnosis was effective in a single case.27 Posttraumatic cases involving only the foot have been reported.28 Rarely, RMD is the sole manifestation of a seizure29 or is associated with REM sleep behavior disorder.30
Propriospinal myoclonus is a spinal cord–mediated movement disorder, occasionally associated with acquired spinal cord lesions. It is characterized by repetitive jerks occurring during the transition from wake to sleep.31 Propriospinal myoclonus may be confused with restless legs syndrome or periodic limb movements in sleep, and it can serve to shed light on the pathophysiology of these two disorders.32 It has been described in various neurologic conditions such as restless legs syndrome, paraneoplastic syndromes, and cervical disk herniation, and in extreme cases it can result in life-threatening respiratory compromise.33–36 The movements can appear during relaxation and can result in severe insomnia, particularly at sleep onset.37 Clonazepam or anticonvulsant medications may be effective in alleviating these movements.31 Propriospinal myoclonus may be related to segmental myoclonus, both spinal and palatal.38
The secondary phenomena are parasomnias representing abnormal or excessive autonomic or physiologic events arising from specific organ systems and occurring preferentially during the sleep period. These can be approached by the offending organ system.
Although some headaches have historically been referred to as “vascular headaches,” there is now overwhelming evidence that the etiology of this headache type is not vascular, but rather a primary neurologic phenomenon.42 Many headache syndromes are sleep related.43 The headache symptoms of cluster headache, chronic paroxysmal hemicrania, and possibly migraines, in some cases, tend to be related to REM sleep, explaining the common report of sleep-related headaches in these conditions.44 This fact explains the worsening of these symptoms following the discontinuation of REM sleep–suppressing agents (which results in a rebound of REM sleep) such as tricyclic antidepressants, monoamine oxidase inhibitors, clonidine, alcohol, and amphetamines. Circadian rhythm abnormalities can play a role in cluster headache and chronic paroxysmal hemicrania.45,46 Episodic paroxysmal hemicrania might respond to calcium channel blockers or topiramate.47,48 Sleep-disordered breathing can serve as a risk factor for headaches in some persons with cluster headaches.49
Although morning headaches may be more prevalent in persons with sleep complaints in general, headaches are not a reliable marker for sleep-disordered breathing.50 However, in some susceptible persons, obstructive sleep apnea can trigger cluster headaches, which respond to bilevel positive airway pressure (BiPAP).51 Headaches associated with sleep-disordered breathing are more commonly seen in patients with neuromuscular disease who experience REM sleep–related hypoventilation, with hypercapnia-induced migraines arising from the sleep period. Carbon monoxide poisoning must never be overlooked as a cause of morning headaches.