Helpful Idiopathic Hypersomnia (IH) words to know

Cataplexy (in Narcolepsy)

A sudden, brief loss of muscle control brought on by a strong emotion or emotional response, such as a hearty laugh, excitement, surprise, or anger. Although this may cause collapse, the patient remains fully conscious. The episode lasts from a few seconds to as long as several minutes.

CNS

Central nervous system.

CSF

Cerebrospinal fluid.

EDS

Excessive daytime sleepiness; the inability to stay awake and alert during the day, resulting in periods of irrepressible need for sleep or unintended lapses into drowsiness or sleep.

ESS

Epworth Sleepiness Scale; a short, self-administered questionnaire designed to measure sleep propensity in a simple, standardized way (8 questions on a total scale of 0 to 24).

GABA

Gamma-aminobutyric acid.

IHSS

Idiopathic Hypersomnia Severity Scale; a brief, self-report instrument designed to measure the severity of key symptoms of hypersomnolence and their consequences.

MSL

Mean sleep latency; determined using a multiple sleep latency test (MSLT).

MSLT

Multiple sleep latency test; a sleep test to measure the physiological tendency to fall asleep in quiet situations. The MSLT consists of five 20-minute nap opportunities at 2-hour intervals. The 2 parameters of most interest are the mean sleep latency (MSL) and the number of SOREMPs.

Orthostatic hypotension

A drop in blood pressure upon standing up.

OSA

Obstructive sleep apnea.

PSG

Polysomnogram; a multiparametric sleep test used to determine sleep latency, sleep time, sleep efficiency, arousals, and the time spent in each phase of sleep.

Raynaud’s phenomenon

Discoloration of the fingers and/or toes after exposure to changes in temperature.

REM

Rapid eye movement.

Sleep efficiency

Percentage of total time in bed actually spent in sleep, calculated as sum of Stage N1, Stage N2, Stage N3, and REM sleep, divided by the total time in bed and multiplied by 100. Sleep efficiency gives an overall sense of how well the patient slept, but it does not distinguish frequent, brief episodes of wakefulness.

Sleep inertia, also known as “sleep drunkenness”

The severe inability to wake up in the morning. It has been characterized as being caught between sleep and wake states, with effects lasting anywhere from minutes to hours.

SOREMPs

Sleep-onset rapid eye movement periods that occur within 15 minutes of sleep onset.