Narcolepsy | CSMA - Greater Houston and Austin

Central Nervous System Causes of Daytime Sleepiness: Narcolepsy and Idiopathic Hypersomnolence

Narcolepsy is a neurological disorder characterized by an abnormal regulation of sleep and wakefulness, primarily affecting Rapid Eye Movement (REM) sleep. In addition to excessive daytime sleepiness, narcolepsy, usually but not always, presents with several distinct clinical features:

1. Sleep paralysis: A brief inability to move or speak upon waking.

2. Hypnagogic or hypnopompic hallucinations: Vivid, dream-like experiences occurring while falling asleep (hypnagogic) or upon waking (hypnopompic).

3. Fragmented sleep: Frequent nighttime awakenings that disrupt sleep continuity.

A subset of narcolepsy patients also experience cataplexy, a sudden loss of muscle tone triggered by strong emotions such as laughter, surprise, fear or anger. This distinguishes narcolepsy type 1 (with cataplexy) from narcolepsy type 2 (without cataplexy).

Since narcolepsy is fundamentally a disorder of REM sleep regulation, patients tend to enter REM sleep more rapidly than normal. Diagnosis is established through a Multiple Sleep Latency Test (MSLT), a daytime sleep study conducted after an overnight sleep study. The MSLT consists of four or five scheduled nap opportunities at two-hour intervals, during which sleep onset latency (time to fall asleep) is measured:

Severe: Less than 5 minutes
Moderate: 5 to 10 minutes
Mild: 10 to 15 minutes

A diagnosis of narcolepsy requires the patient to enter REM sleep within 15 minutes in at least two of the nap sessions. If the overnight sleep study reveals other conditions contributing to sleepiness, such as sleep apnea, these must be addressed (treated) first.

Treatment for narcolepsy involves various medications tailored to the patient's needs, often requiring a combination approach. CSMA is actively engaged in clinical research to develop new treatments for narcolepsy.

Idiopathic Hypersomnolence (IH)

IH is a neurologic condition consisting of an increased tendency (pressure) to fall asleep, similar to narcolepsy, but it is not associated with an increased tendency to go into REM sleep. If an overnight sleep study rules out other causes of excessive daytime sleepiness (e.g., sleep apnea) and the MSLT confirms daytime sleepiness without REM onset in at least two naps, the patient is diagnosed with IH. Like narcolepsy, this condition is treated with medication, and CSMA is involved in ongoing research to explore new therapeutic options to treat this condition.