Non-24-HourSleep-WakeSyndrome(780.55-2)
SynonymsandKeyWords:Free-runningpattern,incrementalasynchronyrelative to typical environmental pattern, periodic insomnia, periodic excessive sleepiness,blindness,hypernycthemeralsyndrome.
EssentialFeatures:
Non-24-hour sleep-wake syndromeconsists of a chronic steady pattern comprising one- to two-hour daily delays in sleep onset and wake times in anindividuallivinginsociety.
Patients with non-24-hour sleep-wake syndrome exhibit a sleep-wake pattern that is reminiscent of that found in normal individuals living without environmentaltimecues(i.e.,sleep-onsetandwaketimesoccurataperiodofaboutevery25hours).Attimes,oneormorenon-circadian(longerthan27hours)sleep-wake cycles may occur in the patient with the non-24-hour syndrome, similar to the phenomenon of internal desynchrony observed in some time-isolation experiments. Such individuals are literally sleeping “around the (24-hour) clock,” despite the presence of 24-hour social and environmental time cues. In the long run, their sleep phase periodically travels in and out of phase with the conventionalsocialhoursforsleep.When“inphase,”thepatientmayhavenosleepcom- plaint,anddaytimealertnessisnormal.Asincrementalphasedelaysinsleep occur,thecomplaintwillconsistofdifficultyinitiatingsleepatnightcoupledwith oversleeping into the daytime hours or inability to remain awake in the daytime. Therefore, over long periods of time, patients alternate between being symptomatic and asymptomatic, depending on the degree of synchrony between their internalbiologicalrhythmandthe24-hourworld.
Some individuals with this condition intermittently or permanently give up attemptingtosynchronizetheirsleepwithconventionalhours.Inthesepatients,a sleep-wake diary or log will appear similar to that of the free-running pattern of time-isolated healthy individuals. Most patients, however, attempt to sleep and wake at conventionalsocialtimes.Theseattemptsproduceprogressivelylesssleep,withsecondarydaytimesleepinessinterferingwithfunctioningatworkorschool.Inaddition, sleep may be skipped for 24 to 40 hours, followed by sleeping for 14 to 24 hourswithoutawakening.Unlikepatientswiththedelayedsleep-phasesyndrome, who share some of the above symptoms, the patient with a non-24-hour disorder does not achieve a stable pattern of normal sleep at a delayed phase during vacationsfromworkorschool.
Associated Features:Typically, individuals with this condition are partially or totally unable to function in scheduled social activities on a daily basis, and most areunabletoworkatconventionaljobs.Mostofthepatientsdescribedinthemedical literature have been blind, either congenitally or on an acquired basis, and somehavebeencognitively impairedaswell.Lesscommonly,aseverelyschizoidor avoidantpersonalitydisordermayaccompanythecondition.Onepatientwhowas initiallydescribed,ashavingthisdisorderwaslaterdiscoveredtohavealargepituitaryadenomathatinvolvedtheopticchiasma.
Efforts to induce sleep at conventional times in these patients often include the use of, and dependency on, hypnotic and analeptic medication, at times in very largedoses. Ahistorythatsuchmedicationsalternatebetweenapparentefficacy andprogressivelossofefficacywithnochangeindosesuggeststhatthenon-24-hour syndrome may be the underlying cause of the patient’s sleep-wake symptoms.
Course:Dependingmostlyonassociatedconditions,thenon-24-hoursyndrome maybechronicandintractableormayrespondwelltotheinstitutionofstrictand regular24-hourtimecues.Someblindindividuals,mostlyininstitutionalizedset- tings, have responded to strict 24-hour scheduling, consisting of strong social timecues.
PredisposingFactors:SeeAssociatedFeatures.
Prevalence:Thisdisorderisapparentlyrareinthegeneralpopulation.Although theprevalenceintheblindisunknown,onesurveyofblindindividualsrevealed a high incidence of sleep-wake complaints, with 40% of the respondents having recognizedthattheirsymptomsoccurredinacyclicpattern.
AgeofOnset:Thesyndromehasbeendescribedincongenitallyblindinfantsas well as in blind middle-aged and elderly individuals. Onset in normal-sighted individualsappearsvariable.
SexRatio:Notknown.
FamilialPattern:Noneknown.
Pathology:Variouscausesofblindnessinvolvingtheopticchiasmaorprechiasmatic visual structures have been present in blind patients with the non-24-hour syndrome,suggestingthattheblindnessitselfunderliesthesyndrome,ratherthan beingthecauseofthesyndrome. Thistheoryisinkeepingwiththelikelihood that the environmental light-dark cycle, acting through the retinohypothalamic tractonthesuprachiasmaticnucleusofthehypothalamus,isamajorsourceof24- hour time information for humans as well as lower animals. Blindness deprives the endogenous circadian timing system of this crucial information, and, particularly when other brain abnormalities are present, social zeitgebers may be ineffective. In sighted individuals, a suprachiasmatic tumor may have been the cause of the syndrome in one case, but personality factors appear to be paramount. In such cases, the conscious or unconscious disregard of entraining cues may serve anadaptive,albeitapathologic,functionforthepatient.
Complications:Thecomplicationsrelatetoimpairedpsychosocialfunctioning.
PolysomnographicFeatures:Little specific information is available. Recordingsdoneatfixedtimes overseveralsuccessivedayswouldbe expectedto showprogressivelylongersleeplatenciesandprogressivelylesstotalsleep,butnormal age-related sleep-stage architecture across the period of study. Electroencephalographic abnormalities, such as reduced sleep spindles and K- complexes,maybepresentinbrain-damagedorcognitively impairedpatients.
OtherLaboratory TestFeatures:Sightedindividuals,aswellasthosewith blindness of unknown etiology, should undergo a neurologic evaluation that includes imaging of the suprasellar region (computed tomographic scan or magneticresonanceimagingscan)
DifferentialDiagnosis:Acarefullykeptsleep-wakelogthatisrecordedfora lengthy period of time is essential to making this diagnosis. Non-24-hour sleep- wake syndrome should be differentiated from delayed sleep-phase syndrome and irregularsleep-wakepattern.Inthedelayedsleep-phasesyndrome,stableentrainmenttoa24-hourschedulewithsleepatadelayedphasefromconventionalhours is present during vacations. Patients with the non-24-hour sleep-wake syndrome continueinapatternofprogressivedelaysofsleep. Thediagnosisshouldbesuspectedinanyblindindividualwithsleeporsomnolencecomplaints.
DiagnosticCriteria:Non-24-HourSleep-WakeSyndrome(780.55-2)
A.Thepatienthasaprimarycomplaintofeitherdifficultyinitiatingsleepor difficultyinawakening.
B.Sleeponsetandoffsetareprogressivelydelayed,withthepatientunableto maintainstableentrainmenttoa24-hoursleep-wakepattern.
C.Thesleeppatternhasbeenpresentforatleastsixweeks.
D.Progressivesequentialdelayofthesleepperiodisdemonstratedbyoneof thefollowingmethods:
1. Polysomnographyperformedoverseveralconsecutivedaysonafixed
24-hourbedtimeandwaketimeschedule
2. Continuous24-hourtemperaturemonitoringoveratleastfivedaysthat showsaprogressivedelayofthetemperaturenadir
E. Thesymptomsdonotmeetthecriteriaforanyothersleepdisordercausing inabilitytoinitiatesleeporexcessivesleepiness.
Note: If the sleep disorder is believed to be socially or environmentally induced,state and code as non-24-hour sleep-wake syndrome (extrinsic type). If there is evidence that the sleep disorder is due to an abnormal circadian pacemakeroritsentrainmentmechanism,stateandcodeasnon-24-hoursleep- wakesyndrome(intrinsictype).
MinimalCriteria:AplusBplusC.
SeverityCriteria:
Mild:Mildinsomniaormildexcessivesleepiness,asdefinedonpage23;usuallyassociatedwithamildimpairmentofsocialoroccupationalfunctioning.
Moderate: Moderate insomnia or moderate excessive sleepiness, as defined on page 23; usually associated with a moderate impairment of social or occupationalfunctioning.
Severe: Severe insomnia or severe excessive sleepiness, as defined on page 23; usually associated with a severe impairment of social or occupational functioning.
DurationCriteria:
Acute:6monthsorless.
Subacute:Morethan6monthsbutlessthan1year.
Chronic:1yearorlonger.
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MilesLE,RaynalDM,WilsonMA.Blindmanlivinginnormalsocietyhascircadianrhythmsof24.9 hours.Science1973;198:421–423.
MilesLE,WilsonMA.Highincidenceofcyclicsleep-wakedisordersintheblind.SleepRes1977;6:192. OkawaM.Sleep-wakingrhythmanditscentralmechanisminhumans:Studiesofbiologicalrhythm,com-
putedtomographyandautopsyofseverelybrain-damagedchildren.AdvNeurol1985;29:346–365. OkawaM,NanamiT,WadaS,etal.Fourcongenitallyblindchildrenwithcircadiansleep-wakerhythm
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