From the Guidelines
Narcolepsy is characterized by several distinctive EEG findings, including sleep-onset REM periods (SOREMPs), which are a key diagnostic criterion for the disorder. The most significant EEG finding in narcolepsy is the presence of SOREMPs, where patients enter REM sleep within 15 minutes of falling asleep instead of the normal 90-minute delay 1. Multiple sleep latency tests (MSLT) typically show a mean sleep latency of less than 8 minutes and at least two SOREMPs, which are diagnostic criteria for narcolepsy. Nocturnal polysomnography often reveals fragmented sleep architecture with frequent awakenings, reduced sleep efficiency, and disrupted slow-wave sleep. Patients with narcolepsy may also demonstrate increased alpha intrusions during non-REM sleep and reduced REM sleep latency during overnight studies.
Key EEG Findings in Narcolepsy
- Sleep-onset REM periods (SOREMPs)
- Multiple sleep latency tests (MSLT) with a mean sleep latency of less than 8 minutes and at least two SOREMPs
- Fragmented sleep architecture with frequent awakenings
- Reduced sleep efficiency
- Disrupted slow-wave sleep
- Increased alpha intrusions during non-REM sleep
- Reduced REM sleep latency during overnight studies Type 1 narcolepsy (with cataplexy) shows more pronounced REM sleep abnormalities than Type 2. These EEG patterns reflect the underlying hypocretin/orexin deficiency in the hypothalamus that disrupts normal sleep-wake regulation. The combination of these EEG findings, particularly SOREMPs on MSLT following a full night's polysomnography, provides crucial objective evidence for diagnosing narcolepsy when combined with clinical symptoms 1.
From the Research
Narcolepsy EEG Findings
- Narcolepsy is characterized by excessive daytime sleepiness, cataplexy, sleep paralysis, and hypnagogic/hypnapompic hallucinations 2.
- The diagnosis of narcolepsy is based on clinical information, combined with polysomnography (PSG) and the Multiple Sleep Latency Test (MSLT) 3.
- PSG and MSLT are moderately reliable at diagnosing narcolepsy type 1 (NT1) but unreliable for diagnosing narcolepsy type 2 (NT2) 3.
- The presence of sleep-onset REM periods (SOREMP) in MSLT and PSG is a key diagnostic criterion for narcolepsy 4.
- SOREMP occurred more frequently in narcoleptic vs. non-narcoleptic patients in MSLT and PSG 4.
- The frequency of SOREMP in MSLT and PSG can help to discriminate but not clearly separate narcoleptic from non-narcoleptic patients 4.
- Repeated PSG and MSLT testing can provide a more accurate diagnosis of NT1 and other hypersomnolence disorders 3.
- NT1 patients had stable clinical and electrophysiological presentations over time, suggesting a stable phenotype 3.
- Differential characteristics of repeated PSG and MSLT parameters in NT1 and NT2 patients indicate that NT1 and NT2 are distinct disease phenotypes 5.
EEG Findings in Narcolepsy
- Decreased sleep latency and REM latency in NT1 patients compared to NT2 patients 5.
- Nocturnal SOREMP on PSG was more prevalent in NT1 patients 5.
- Reductions in sleep stage N2 and N3, and increases in wake after sleep onset (WASO) and apnea-hypopnea index (AHI) in NT1 patients on follow-up PSG 5.
- Sleep-stage sequencing of sleep-onset REM periods in MSLT can predict treatment response in patients with narcolepsy 6.