Cataplexy

Specialty: Neurology.

• cataplexy
• sudden loss of muscle tone due to emotions

Why it occurs

• Narcolepsy type 1 (selective loss of hypocretin-producing neurons in the lateral hypothalamus with dysregulation of the REM sleep transition)
• Paraneoplastic or autoimmune encephalitis (with involvement of the diencephalon, anti-Ma2 antibodies)
• Hypothalamic destructive structural lesions (tumors such as craniopharyngioma or midline gliomas)
• Niemann-Pick disease type C (autosomal recessive lysosomal storage disorder with cataplexy and vertical gaze palsy)
• Rebound effect due to sudden withdrawal of serotonin reuptake inhibitor antidepressants

Initial workup

Multiple Sleep Latency Test (TLMS) that demonstrates average sleep latency < 8 minutes and presence of at least two episodes of REM sleep (SOREMPs); lumbar puncture to measure hypocretin-1 (orexin-1) concentration in CSF (levels less than 110 pg/mL are confirmatory of type 1 narcolepsy); Brain MRI to exclude hypothalamic tumor pathology.

Standard management

• Sodium oxybate — 4.5-9 g/night divided into two doses, considered the most effective drug to drastically reduce the frequency and severity of cataplexy
• Venlafaxine — 75-150 mg/day, selective serotonin and norepinephrine reuptake inhibitor that suppresses REM sleep
• Clomipramine — 25-75 mg/day
• Pitolisant (9-36 mg/day, histamine H3 receptor antagonist/inverter).