Narcolepsy

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Narcolepsy is a central disorder of sleep–wake regulation rather than simply fatigue. Sleep pressure intrudes into wakefulness and REM phenomena intrude at sleep–wake transitions. Onset is often in adolescence or young adulthood, but diagnostic delay is common because sleepiness is attributed to lifestyle, school, depression or epilepsy. Ask separately about propensity to fall asleep, low energy and weakness: they are not interchangeable. Quantify naps, unintentional sleep, near misses, shift pattern and nocturnal sleep opportunity.

Cataplexy is the most specific historical feature. Laughter, surprise, excitement or anger triggers bilateral weakness, awareness remains intact and recovery is rapid without post-ictal confusion. Focal weakness, prolonged unresponsiveness, tonic movement or events unrelated to emotion suggest seizure, syncope, drop attack or functional episodes. Children may show facial hypotonia, tongue protrusion or complex movements before the classic adult pattern emerges.

Diagnosis belongs in a sleep service because test validity depends on preparation. Sleep diary and sometimes actigraphy document adequate opportunity and stable timing. Overnight polysomnography identifies sleep apnoea, periodic movements and sufficient sleep and is followed by MSLT. REM-suppressing antidepressants, stimulants, cannabis and withdrawal can alter results, but stopping medicines abruptly may be unsafe; the sleep specialist plans any washout. Treatment is individual and long term, with medicine benefit measured against sleep attacks, cataplexy, adverse effects and function.

Key points

Narcolepsy causes persistent excessive daytime sleepiness with irresistible sleep episodes; brief naps are often refreshing but do not prevent recurrence later the same day.
Type 1 narcolepsy is defined by cataplexy and/or documented hypocretin deficiency, whereas type 2 lacks cataplexy and requires objective sleep findings after competing causes are excluded.
Cataplexy is sudden emotion-triggered loss of muscle tone with preserved awareness, ranging from jaw sag or slurred speech to knee buckling or collapse and usually lasting seconds to minutes.
Sleep paralysis, vivid hypnagogic or hypnopompic hallucinations, fragmented nocturnal sleep and automatic behaviour support the diagnosis but occur outside narcolepsy and are not individually diagnostic.
Exclude chronic sleep restriction, shift work, obstructive sleep apnoea, circadian disorder, sedating medicines, alcohol or drugs, depression and neurological disease before interpreting a multiple sleep latency test.
A valid MSLT follows adequate documented sleep and attended overnight polysomnography, typically showing short mean sleep latency and at least two sleep-onset REM periods under accepted criteria.
Management combines regular sleep scheduling, planned brief naps, education and specialist wake-promoting or anticataplectic medicines selected around occupation, cardiovascular, psychiatric and reproductive risks.
Excessive sleepiness creates immediate driving and workplace hazards; apply current DVLA notification and licensing standards and advise the person not to drive while symptoms are uncontrolled.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Hypocretin-neuron autoimmunity

Type-one narcolepsy usually reflects selective loss of hypothalamic hypocretin-producing neurons, probably through immune-mediated injury in a genetically susceptible person.

Type-two narcolepsy

The cause is less clear when cataplexy and documented hypocretin deficiency are absent, making exclusion of other sleepiness disorders especially important.

Secondary hypothalamic disease

Rarely, tumour, inflammation, trauma or genetic disease damages hypothalamic sleep–wake systems and produces a narcolepsy-like syndrome.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Loss of wake-state stabilisation
Hypocretin normally sustains arousal networks; deficiency permits unwanted transitions from wakefulness into sleep during daytime activities.
2
REM-state intrusion
Boundaries between wake and REM sleep become unstable, producing sleep-onset REM, vivid hallucinations and sleep paralysis.
3
Cataplexy
Emotion triggers REM-like loss of skeletal-muscle tone during wakefulness while awareness remains preserved, ranging from facial weakness to collapse.
4
Fragmented sleep architecture
Night sleep also becomes disrupted, so excessive daytime sleepiness reflects unstable state control rather than simply insufficient time in bed.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Excessive sleep propensity

Unintended sleep during passive and sometimes active situations, refreshing short naps and repeated sleep attacks distinguish physiological sleepiness from vague tiredness.

Classic cataplexy

Emotion produces brief bilateral jaw, neck, facial or limb weakness while consciousness and memory remain intact and breathing is usually preserved.

REM intrusion

Vivid dream-like experiences and temporary inability to move on falling asleep or waking can be frightening but become more informative when combined with sleepiness and cataplexy.

Nocturnal fragmentation

Despite daytime sleepiness, night sleep may be broken by frequent awakening, vivid dreams, movement, apnoea or parasomnia.

Automatic behaviour

A person may continue writing, travelling or another familiar task with poor awareness and later amnesia during severe sleepiness.

Paediatric presentation

Irritability, hyperactivity, declining school performance, long naps, obesity or unusual cataplexy-like facial movements can precede recognition in children.

Red flags requiring action

Sleepiness while driving, operating machinery, working at height or caring alone for a child requires immediate activity restriction and occupational risk planning.
New hypersomnolence with focal neurology, headache, endocrine disturbance or rapid weight change requires assessment for secondary hypothalamic, inflammatory or structural disease.
Prolonged loss of consciousness, injury, exertional collapse, palpitations or post-event confusion is not typical cataplexy and needs cardiac or seizure assessment.
Pregnancy or pregnancy planning while taking modafinil requires urgent specialist and contraceptive review because of congenital malformation risk and reduced steroid contraceptive effectiveness.
Combining sodium oxybate with alcohol, opioids or other respiratory depressants can cause severe sedation and respiratory compromise.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Sleep history and diaryFirst step
Why
Document sleep opportunity, timing, naps, shift work and symptom consistency before objective testing.
Interpretation and limitations
Chronic restriction or unstable circadian timing can produce a false-positive sleepy MSLT and should be corrected before diagnostic testing where safe.
02
Actigraphy
Why
Objectively estimate sleep timing and duration over one or more weeks when diary reliability or circadian disorder is uncertain.
Interpretation and limitations
Movement is a proxy rather than a direct sleep measure; interpret alongside diary, work schedule and light exposure.
03
Overnight polysomnography
Why
Exclude obstructive sleep apnoea and other sleep disruption and verify adequate sleep before MSLT.
Interpretation and limitations
Untreated apnoea, insufficient sleep or a nocturnal sleep-onset REM period affects the next-day interpretation and may require treatment or repeat testing.
04
Multiple sleep latency test
Why
Measure physiological sleep propensity and the occurrence of sleep-onset REM across scheduled daytime nap opportunities.
Interpretation and limitations
A mean latency of 8 minutes or less with at least two sleep-onset REM periods supports narcolepsy in the correct protocol and clinical setting; it is not diagnostic in isolation.
05
CSF hypocretin-1
Why
Confirm hypocretin deficiency when type 1 narcolepsy is strongly suspected but cataplexy or MSLT information is atypical or unavailable.
Interpretation and limitations
Use a specialist laboratory and accepted threshold; lumbar puncture invasiveness means this is not required for every classic presentation.
06
Respiratory sleep testing
Why
Assess obstructive sleep apnoea when snoring, witnessed apnoea, obesity or morning headache accompanies sleepiness.
Interpretation and limitations
Narcolepsy and sleep apnoea can coexist; improvement after airway treatment does not erase persistent cataplexy or objective REM dysregulation.
07
Cause-directed blood or brain investigation
Why
Evaluate anaemia, thyroid disease, medication toxicity or a hypothalamic lesion when the history is atypical.
Interpretation and limitations
Routine imaging is not required for every primary narcolepsy case; rapid onset, neurological or endocrine signs justify MRI and broader work-up.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Sleep deprivation or shift work

Documented insufficient or mistimed sleep explains daytime sleepiness without characteristic cataplexy or valid sleep-onset REM findings.

Obstructive sleep apnoea

Snoring, witnessed apnoea and fragmented overnight sleep support sleep-disordered breathing, which should be addressed before interpreting daytime latency testing.

Idiopathic hypersomnia

Long unrefreshing sleep and severe sleep inertia without cataplexy or repeated sleep-onset REM favour idiopathic hypersomnia.

Seizure or syncope

Cataplexy preserves awareness and follows emotion; altered consciousness, post-event confusion or cardiovascular prodrome suggests epilepsy or syncope.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01SLEEPYPersistent daytime sleepinessFirst stepSleep attacks or unintended sleep occur repeatedly for at least several months.

1Distinguish sleepiness from fatigue and record night duration, shift work, snoring, apnoea, restless legs, medicines, alcohol, mood and medical illness.
2Ask specifically about emotion-triggered weakness, sleep paralysis, hallucinations, refreshing naps and safety-critical near misses.
3Correct inadequate sleep and obvious sedative contributors safely, screen for obstructive sleep apnoea and refer persisting unexplained sleepiness to a sleep service.
4Advise against driving or hazardous work while sleep attacks remain uncontrolled and apply current DVLA and occupational requirements.

02TESTPrepare valid objective testingThe sleep specialist considers narcolepsy or idiopathic hypersomnia after clinical assessment.

1Document adequate regular sleep with diary and actigraphy as indicated and stabilise shift or circadian disruption before testing.
2Review stimulants, sedatives, antidepressants and recreational drugs and plan any safe washout with the prescriber rather than stopping abruptly.
3Perform attended overnight polysomnography followed by protocol-standard MSLT when sufficient sleep and untreated apnoea do not invalidate it.
4Integrate latency and REM results with cataplexy and the clinical history and repeat or use CSF hypocretin only when uncertainty justifies it.

03TREATConfirmed narcolepsyClinical and objective evidence establishes type 1 or type 2 narcolepsy.

1Agree a stable sleep schedule, planned short naps, school or workplace adjustments, exercise and strategies for meals, meetings and travel.
2Select wake-promoting therapy and, when needed, cataplexy treatment with the sleep specialist after cardiovascular, psychiatric, interaction and reproductive review.
3Measure unintentional sleep, cataplexy, function and adverse effects after each change rather than titrating solely to a questionnaire score.
4Revisit driving only when symptom control and licensing requirements are met and document advice clearly.

04PREGNANCYConception or pregnancy planningA person who could become pregnant uses modafinil or another narcolepsy medicine and is planning pregnancy or has a positive test.

1Arrange prompt sleep-medicine and obstetric or preconception review and assess the immediate risk from untreated sleep attacks and cataplexy.
2AlternativeDo not use modafinil during pregnancy and review a safe discontinuation and alternative plan under current MHRA and product guidance.
3AlternativeExplain that modafinil can reduce hormonal contraceptive effectiveness and use an effective alternative during treatment and for the specified period after stopping.
4Plan work, driving, infant-care and postpartum sleep support because fragmented sleep can worsen symptoms even without medicine exposure.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

Promotes wakefulness and reduces excessive daytime sleepiness in adult narcolepsy as part of behavioural and safety management.

Modafinil

A common adult specialist regimen is 200 mg daily, given in the morning or divided morning and midday, with adjustment up to 400 mg daily only when response is insufficient. Reduce the dose by half in severe hepatic impairment; people over 65 should usually start at 100 mg daily.

Avoid in pregnancy; use effective contraception during treatment and for 2 months after stopping, recognising reduced steroidal-contraceptive effectiveness. It is contraindicated in uncontrolled moderate-to-severe hypertension and cardiac arrhythmias. Evidence is inadequate to define safe dosing in renal impairment; monitor blood pressure, psychiatric or serious skin reactions and interactions.

Histamine H3-receptor inverse agonism can improve daytime sleepiness and cataplexy in selected adults with narcolepsy.

Pitolisant

Start and titrate once daily in the morning using the licensed weekly schedule, hepatic or renal adjustments and maximum selected by the specialist service.

Review QT prolongation, interacting CYP medicines, severe hepatic impairment and contraceptive effectiveness; avoid unsupervised rapid escalation.

Improves cataplexy, nocturnal sleep consolidation and daytime sleepiness in carefully selected narcolepsy patients.

Sodium oxybate

Use a specialist-titrated total nightly dose divided into two doses, one at bedtime and one 2.5–4 hours later, exactly as the controlled-drug product and service protocol specify. The starting dose must be halved in every patient with hepatic impairment and subsequent increments monitored closely.

It is a potent CNS depressant: alcohol must be avoided, concomitant opioids or barbiturates are contraindicated, and major depression is also a contraindication; assess sleep-disordered breathing, review every other sedative, and plan secure storage and reliable night dosing. In renal impairment, account for the product's sodium load and consider dietary sodium reduction.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Driving and workplace injury

Irresistible sleep and automatic behaviour can cause collisions, machinery accidents and occupational restriction when symptoms are uncontrolled.

Cataplexy-related trauma

Sudden loss of tone causes falls, head injury and avoidance of laughter, exercise or social interaction.

Educational and psychosocial harm

Sleepiness impairs concentration, attendance and relationships and may be misinterpreted as laziness, depression or poor motivation.

Treatment-related risk

Wake-promoting and anticataplectic medicines can affect cardiovascular, psychiatric, reproductive and sleep physiology, requiring specialist review throughout treatment.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Track unintended sleep, planned naps, cataplexy frequency, sleep paralysis, nocturnal quality and functional goals after treatment changes.
Measure blood pressure and pulse and review weight, appetite, mood, anxiety, psychosis and skin reactions according to the selected medicine.
Review sleep duration, shift pattern and coexisting obstructive sleep apnoea because behavioural relapse can mimic medicine failure.
Check prescription, over-the-counter, contraception and recreational drug interactions at each structured medicine review.
Confirm driving status and DVLA advice and revisit occupational risk after any recurrence or medicine interruption.
For children and young people, follow growth, school function, mental health and transition to adult sleep services.
During pregnancy planning or postpartum care, review medication exposure and practical safety around feeding, night waking and infant handling.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Cataplexy preserves awareness

The person can usually hear and remember events during weakness, which helps distinguish typical attacks from syncope and many seizures.

Narcolepsy disrupts night sleep

Severe daytime sleepiness does not guarantee prolonged consolidated sleep overnight; fragmentation is part of the disorder.

Test preparation is diagnostic work

Sleep restriction, circadian misalignment and medication withdrawal can create false REM findings, so the preceding weeks determine MSLT validity.

HLA is not a confirmation test

The associated HLA type is common in the general population and lacks the specificity to diagnose narcolepsy routinely.

Naps are planned treatment

A short scheduled nap before a predictable vulnerable period may improve function more safely than repeatedly escalating stimulant exposure.

Contraception interaction matters

Modafinil can reduce steroid contraceptive effectiveness in addition to its pregnancy risk, requiring proactive alternative contraception advice.

11Common pitfallsFrequent interpretation and management errors.

01
Do not equate fatigue, low motivation or depression automatically with physiological excessive sleepiness.
02
Do not diagnose cataplexy when consciousness is lost, events are prolonged or there is post-ictal confusion without specialist review.
03
Do not order or interpret MSLT after chronic sleep restriction, untreated apnoea or an unsafe unplanned antidepressant withdrawal.
04
Do not use HLA status as a standalone diagnosis or reassurance test.
05
Do not prescribe modafinil without pregnancy, contraception, interaction, cardiovascular and psychiatric review.
06
Do not combine sodium oxybate with alcohol, opioids or sedating medicines.
07
Do not allow apparent medicine response to replace DVLA notification, licensing and workplace safety requirements.