What Are the Types of Narcolepsy? Sleep Experts Explain the Differing Presentations of This Sleep Disorder

One type features episodes of muscle weakness; a second type is more difficult to diagnose.

Narcolepsy, a perplexing sleep disorder, has often been misrepresented and trivialized in film and entertainment, failing to accurately portray its diverse presentations and multifaceted symptoms, as noted by the nonprofit Project Sleep. To rectify this distortion, it is crucial to shed light on the true nature of narcolepsy. With an estimated 200,000 individuals affected in the United States and the potential for many more undiagnosed cases, narcolepsy stands as a significant health concern, elucidated by the National Institute of Neurological Disorders and Stroke (NINDS).

A cornerstone symptom of both narcolepsy types, excessive daytime sleepiness, underscores the challenges faced by those living with this condition. Alongside this pervasive drowsiness, narcolepsy encompasses a spectrum of symptoms, including cataplexy, sleep paralysis, hallucinations, fragmented sleep, and automatic behaviors. These markers of the disorder are most likely to manifest in childhood or early adulthood, although narcolepsy can emerge at any stage of life.

In the following exploration, we unravel the intricate web of narcolepsy, discerning between its two primary types—type 1 and type 2—and delving into the rare form associated with brain injury. Additionally, we navigate the diagnostic journey and the array of treatment options offered by sleep specialists.

Demystifying Narcolepsy: An Overview of Its Types

Narcolepsy is classified into two main types—type 1 and type 2—along with a less common third type triggered by brain injury, specifically affecting the hypothalamus region, as elucidated by the Division of Sleep Medicine at Harvard Medical School.

Type 1 Narcolepsy: The Classic Presentation

Type 1 narcolepsy represents the most prevalent and well-known form of the disorder. In addition to the overarching symptoms shared by all narcoleptics, individuals with this variant experience cataplexy, a hallmark characteristic.

Cataplexy is described by Dr. Athanasios Kaditis, MD, an adjunct clinical assistant professor of Child Health at the University of Missouri School of Medicine, as “an abrupt, bilateral, complete or partial loss of muscle tone.” It is typically triggered by intense emotional experiences such as laughter or anger, with episodes lasting from a few seconds to several minutes. These episodes can manifest as physical changes, including head drooping and slurred speech. Importantly, the frequency of cataplexy episodes varies widely, with some individuals experiencing multiple daily episodes, while others encounter only one or two annually.

Beyond cataplexy, individuals with narcolepsy type 1 exhibit low levels of hypocretin-1, a chemical essential for regulating wakefulness. While the precise cause of this hypocretin deficit remains elusive, researchers speculate that it may result from an autoimmune response. In this scenario, the immune system mistakenly targets the brain cells containing hypocretin, as posited by NINDS.

It is worth noting that while cataplexy is a strong indicator of narcolepsy type 1, approximately 30% of cases present with cataplexy-like symptoms due to conditions such as Niemann-Pick Disease Type C and Angelman Syndrome, as revealed in a 2019 review in Sleep Medicine.

Diagnosis of narcolepsy type 1 involves an overnight sleep study, coupled with a next-day nap test. A polysomnogram records various parameters, including eye movement and brain activity, while also assessing whether REM (rapid eye movement) sleep occurs earlier than usual, as stipulated by NINDS. Subsequently, a multiple sleep latency test (MSLT) is conducted, monitoring individuals as they take scheduled naps. This test measures the time taken to fall asleep and the onset of REM sleep, offering valuable diagnostic insights. Furthermore, hypocretin-1 levels in the cerebrospinal fluid, often assessed via a spinal tap, can confirm the diagnosis of narcolepsy type 1, with levels below 110 picograms per milliliter considered diagnostic, as detailed by Dr. Alex Dimitriu, MD, a double board-certified expert in psychiatry and sleep medicine.

Type 2 Narcolepsy: The Elusive Diagnosis

In contrast to narcolepsy type 1, type 2 narcolepsy lacks cataplexy and exhibits normal hypocretin levels. Diagnosing type 2 narcolepsy can be challenging due to the absence of these defining features, and symptoms are typically milder. Moreover, the primary symptom—excessive daytime sleepiness—can result from a variety of other sleep disorders, such as sleep apnea, further complicating the diagnostic process.

Individuals with type 2 narcolepsy may experience delayed diagnosis, with Dr. Chelsie Rohrschieb, PhD, a leading neuroscientist and sleep specialist for Wesper, explaining that doctors often commence by ruling out underlying health conditions, including anemia, chronic fatigue syndrome, hypothyroidism, cancer, and mental illness. Subsequently, a sleep study is employed to exclude sleep apnea, which is relatively easier to diagnose. Once these conditions are eliminated as potential causes, a sleep specialist may conduct an overnight sleep study and a daytime nap study, mirroring the diagnostic process for narcolepsy type 1. This approach considers shorter latency periods for falling asleep and entering REM sleep as key indicators, as highlighted by Dr. Dimitriu. Notably, some researchers theorize that narcolepsy type 2 may serve as a precursor to narcolepsy type 1, suggesting a continuum of narcoleptic disorders.

The American Academy of Sleep Medicine acknowledges that individuals with low hypocretin levels, even without cataplexy, may be classified as having narcolepsy type 1.

Secondary Narcolepsy: An Underlying Cause

Distinct from narcolepsy types 1 and 2, secondary narcolepsy arises from a precise and identifiable cause: damage to the hypothalamus, a critical brain region regulating sleep. This variant of narcolepsy emerges when the hypothalamus is injured due to various factors, as outlined by Dr. Rohrschieb. These factors encompass:

1. Head Trauma: Traumatic injuries to the head can precipitate secondary narcolepsy.

2. Brain Tumor: The presence of a brain tumor can disrupt the hypothalamus, leading to this condition.

3. Multiple Sclerosis: Individuals grappling with multiple sclerosis may develop secondary narcolepsy.

4. Brain Inflammation: Conditions characterized by brain inflammation, such as encephalitis, can result in the destruction of signaling pathways responsible for promoting wakefulness.

In addition to experiencing typical narcolepsy symptoms, individuals with secondary narcolepsy often require an extensive amount of sleep, often exceeding ten hours per day. They may also contend with severe neurological issues, underscoring the complexity of this condition.

Treatment for secondary narcolepsy must address both the underlying cause of brain injury and the narcoleptic symptoms. In terms of symptom management, the approach aligns with the strategies employed for narcolepsy types 1 and 2.

Navigating the Path to Diagnosis and Treatment

Upon suspecting narcolepsy, individuals embark on a diagnostic journey guided by sleep specialists. This journey typically encompasses a multifaceted approach, encompassing lifestyle modifications and pharmacological interventions.

Behavioral Treatment: Lifestyle modifications are integral to managing narcolepsy. Behavioral strategies recommended by NINDS include:

• Regular napping: Scheduled short naps throughout the day can alleviate daytime sleepiness.
• Consistent sleep schedule: Adhering to a regular sleep routine fosters improved sleep quality.
• Physical activity: Engaging in regular exercise can enhance wakefulness.
• Avoidance of alcohol and nicotine before bedtime: These substances can disrupt sleep patterns and exacerbate narcoleptic symptoms.

Dr. Rohrschieb underscores the importance of good sleep hygiene and emphasizes the significance of adhering to a consistent sleep schedule for individuals with narcolepsy.

Medication: Pharmacological interventions constitute a pivotal component of narcolepsy management. Medications recommended by Mayo Clinic include:

• Stimulants: These medications help individuals combat daytime sleepiness, allowing them to remain alert.
• Selective serotonin reuptake inhibitors (SSRIs): SSRIs can mitigate REM sleep disturbances.
• Tricyclic antidepressants: This class of medications effectively addresses cataplexy.
• Sodium oxybate (Xyrem): Administered at night, this medication proves efficacious in managing cataplexy.

Treatment plans are highly individualized, tailored to the specific needs and symptoms of each patient. Following a narcolepsy diagnosis, sleep specialists collaborate with patients to determine the optimal combination of lifestyle adjustments and medications, aiming to enhance their quality of life and mitigate the disruptive effects of this complex sleep disorder.

In conclusion, narcolepsy defies the stereotypes perpetuated by popular culture, necessitating a comprehensive understanding of its diverse presentations and the nuances that distinguish its various types. By acknowledging the distinctions between narcolepsy types 1 and 2, along with the rare secondary narcolepsy arising from brain injury, we can illuminate the diagnostic path and the array of treatment options available to those grappling with this condition. Furthermore, this increased awareness fosters empathy and support for individuals navigating the complexities of narcolepsy, ultimately improving their quality of life and well-being.