Narcolepsy is a chronic neurologic disorder with abnormality in regulating the wake-sleep cycle with patients falling asleep inappropriately during the day. Cataplexy is defined as the sudden and transient episode of loss of muscle tone, often triggered by emotions such as laughing, crying, terror that exists in 70% of patients with narcolepsy. Narcolepsy is typically the result of genetic predisposition and abnormal neurotransmitter function and sensitivity. Patients with narcolepsy present with excessive daytime sleepiness and falling asleep inappropriately while in the middle of a conversation or behind the wheel, and/or watching TV, hypnagogic hallucinations, and sleep paralysis. If cataplexy present then the patient looses muscle tone and collapses without loss of consciousness.
Narcolepsy diagnosis begins with clinical presentation and confirmed with a multi-sleep latency test where two or more REM onsets naps are documented. Other diagnostic tools include genetic testing or a lumbar puncture to look for markers in the CSF.
The treatment of narcolepsy includes Armodafinil (Nuvigil) and Modafinil (Provigil). Alternative medications include stimulants (Adderall and Ritalin and others). Cataplexy on the other hand is treated with certain antidepressants such as imipramine, clomipramine, protriptyline venlafaxine, fluoxetine, paroxetine, sertraline, or citalopram. Another medication that is commonly used to treat cataplexy if the above options fail is sodium oxybate (Xyrem); which is highly regulated due to the side effect profile .
REM sleep behavior disorder (RBD):
RBD is characterized by loss of normal voluntary muscle atonia (loss of muscle tone) during REM associated with complex motor behavior while dreaming. Patients are naturally paralyzed during REM sleep to avoid acting out their dreams. In this disorder, patients are not paralyzed and therefore they act out their dreams. This disorder can be very detrimental to the family where patients injure themselves and/or family members while asleep. RBD disorder can be primary where there is no cause can be identified or secondary where it can be related to other neurologic or metabolic disorders such as vascular lesions, brain stem cancer, demyelinating disease and MS, or autoimmune disorders.
The diagnosis of RBD is typically based on the clinical history. However an attended overnight sleep study can aid in the diagnosis documenting the movements on video and increase muscle tone during REM sleep. At times, imaging of the brain and metabolic workup might be necessary in ruling out secondary causes.
The treatment typically starts with patient and family education about safety during the night. Medications used include clonazepam, melatonin, or Pramipexole.