Makindo Medical Notes

Note: Hypocretin (Orexin) 1 & 2 are hypothalamic neuropeptides critical in maintaining the sleep–wake cycle. Deficiency is central to narcolepsy type 1.

🌙 About

• Narcolepsy is a chronic neurological disorder of REM sleep regulation, leading to disordered nocturnal sleep and excessive daytime sleepiness (EDS). Patients often fall asleep suddenly in inappropriate situations, which may have major psychosocial consequences.

🔑 Classic Tetrad of Symptoms

• 😴 Excessive Daytime Sleepiness (EDS)
• 🛏️ Sleep Paralysis – transient inability to move at sleep onset/waking
• 🎭 Hypnagogic / Hypnopompic Hallucinations – vivid, dream-like experiences when falling asleep or waking
• ⚡ Cataplexy (specific to Type 1) – sudden loss of muscle tone triggered by strong emotions

💡 Cataplexy: Triggered by laughter, stress, or crying. May present with slurred speech or complete collapse, but consciousness is preserved. Episodes last seconds–minutes.

📑 Types of Narcolepsy

• Type 1: Hypocretin deficiency + cataplexy.
• Type 2: Normal hypocretin; no cataplexy.

🧬 Aetiology

• Loss of orexin/hypocretin neurons in the hypothalamus → impaired REM control.
• Low CSF orexin-A is diagnostic for Type 1.
• Associated with HLA-DQB1*0602 allele, but not specific (30% of general population are carriers).
• Autoimmune mechanisms are suspected in pathogenesis.

🧾 Clinical Features

• EDS → irresistible sleep episodes, “sleep attacks” in class, work, or conversations.
• Hypnagogic (sleep-onset) and Hypnopompic (awakening) hallucinations → often frightening.
• Sleep paralysis → inability to move despite awareness.
• Cataplexy → emotion-triggered, loss of tone but preserved awareness.
• Exams: Epworth Sleepiness Scale, confirm with Multiple Sleep Latency Test (MSLT) showing short sleep latency & REM onset.

🔍 Differential Diagnosis

• Obstructive Sleep Apnoea (OSA): Both cause EDS. OSA has snoring, apnoeas, and obesity risk factors.
• Depression or shift-work sleep disorder: Can mimic fatigue & poor sleep regulation.
• Idiopathic hypersomnia: Excess sleepiness without cataplexy or REM dysregulation.

💊 Management

• 🌱 Non-pharmacological: Strict sleep hygiene, scheduled naps, avoidance of sleep deprivation, good lifestyle routines.
• 💊 Pharmacological:
  • Modafinil – first-line for EDS (wakefulness-promoting).
  • Sodium Oxybate – improves cataplexy and sleep quality.
  • Stimulants (e.g., dextroamphetamine, methylphenidate) – reserved for refractory cases.
  • SSRIs/SNRIs – sometimes used to reduce cataplexy by suppressing REM sleep.

📌 Exam Pearls

• EDS is universal in narcolepsy – cataplexy distinguishes Type 1 from Type 2.
• Always rule out OSA before diagnosing narcolepsy.
• Narcolepsy often first presents in adolescence or early adulthood – may be mislabelled as “lazy” or “unmotivated.”

📚 References

• Narcolepsy: A Clinical Review
• NHS UK – Narcolepsy