Symptoms of narcolepsy
The core symptoms are excessive daytime sleepiness and cataplexies. The majority of narcolepsy patients start with the symptom of excessive daytime sleepiness. Cataplexies can follow after months and years. About 20% of all narcoleptic patients do not have cataplexies.
Excessive daytime sleepiness
EDS can occur at any time throughout the day, particularly in monotoneous situations. Sleep episodes are typically irresistible and usually short and refreshing. They are often associated with dreaming and restore wakefulness for up to several hours. These short naps have a refreshing capacity in the majority of patients in contrast to hypersomnias of other origins and therefore it serves as a tool for differential diagnosis. I have to say that I do not fully agree. They are more common in narcolepsy but not very important for the differentiation from other hypersomnia’s.
Narcolepsy is better characterized by an inability to remain awake than by an increased of sleep.
Cataplexy is the best diagnostic marker of the disease. It is characterized by a sudden drop of muscle tone triggered by strong emotions, that are mainly by positive (e.g. laughter, surprise, positive anticipation etc.). Cataplexies can appear in many different forms. Sometimes they are limited to facial muscles, dropping of the head, jaw tremor, slurred speech, or the affect the arms or legs with dropping of objects, or unlocking of the knees.The severest cataplexies include falls.
The duration of cataplexies varies from seconds to several minutes. The frequency of cataplexies varies from less than one episode per year to several episodes per day. Cataplexies can be provoked by watching funnies or by being tickled by a person that is in close relationship. It often does not show in the doctors office, and is released when leaving the office.
Hallucinations can appear while falling asleep (hypnagogic) or on awakening (hypnopompic) and can be auditory, visual or sensory (feeling something creeping under the cover, feeling of being touched, smelling something is burning etc.). The term hallucinations is actually not quite correct as it implicates being convinced that this is true. The narcoleptic patient can easily distinguish this symptom from a real perception in the moment of wakefulness.
Sleep paralysis is an inability to perform voluntary movements while falling asleep or on awakening. During these episodes patients are mentally awake. Sleep paralysis can be associated with hypnagogic hallucinations. Sleep paralysis can last from a few seconds up to several minutes in rare cases.
Automatic behaviours are characterized by continuation of an activity despite sleepiness or falling asleep. Patients can not recall what happened during these episodes that are called “microsleep” in other disorders that are associated with hypersomnia due to different reasons. Whether automatic behaviour is caused by microsleep or cognitive impairment when drowsy is unknown.
Sleep latency is typically short. Fragmented sleep
The sleep disturbance of nocturnal sleep often develops later in the course of narcolepsy and is characterized by frequent awakenings that last minutes to hours. The total sleep time in the 24 hour period is not prolonged.
Increased body weight
Patients with narcolepsy often present with increased body-mass indices. Some, especially children, gain weight after the onset of narcolepsy despite intake of less calories than healthy control persons.
An increased frequency of non-insulin dependent Diabetes mellitus has been observed among narcoleptic patients. Both observations regarding metabolic changes suggest a direct pathophysiological link.
Associations with other sleep disorders
NREM parasomnias (sleepwalking, sleep terror and sleeptalking) and REM parasomnias (REM sleep behaviour disorder in which patients physically enact their dreams) have been recorded in 20-60% of all narcoleptic patients. Many patients also suffer from sleep apnea (intermittent nocturnal breathing pauses of 10 seconds to several minutes), periodic limb movement in sleep (repetitive, stereotyped movement of feet and toes) and some have restless legs syndrome (an urge to move the feet during wakefulness and sleep associated with unpleasant feelings of the limbs that are relieved by moving the feet).