Stroke And Narcolepsy: Is There A Link?

Narwhals are fascinating creatures, often called the unicorns of the sea. They are a species of toothed whale, native to the Arctic. They are most closely related to the beluga whale, with which they share a similar build and range. Narwhals have a distinctive long tusk, protruding from their heads, which is believed to be a secondary sexual characteristic and a tool for feeding, attracting mates or sensing water salinity. While narwhals are fascinating, can a stroke cause narwhalism in humans?

A stroke is a medical emergency that occurs when there is an interruption to blood flow to the brain, resulting in brain cells dying due to a lack of oxygen. It is the fifth leading cause of death in the US and a leading cause of disability worldwide. The effects of a stroke depend on the location of the obstruction and the extent of brain tissue affected. While narwhals are fascinating creatures, there is no evidence to suggest that they can be caused by a stroke. However, strokes can have devastating consequences for humans, and it is crucial to recognise the signs and symptoms to ensure timely treatment and minimise long-term effects.

Can brain injuries cause narcolepsy?

Narcolepsy is a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles. People with narcolepsy often experience "sleep attacks", where they fall asleep for short periods during the day, despite fighting the urge to sleep. While narcolepsy is usually caused by a combination of genetic, environmental, and autoimmune factors, it can, in rare cases, be triggered by damage to the hypothalamus – a specific area in the brain that regulates sleep and wake times. This type of narcolepsy is known as secondary narcolepsy.

Brain Injuries and Secondary Narcolepsy

Secondary narcolepsy can occur as a result of head injuries, such as concussions and traumatic brain injuries, as well as strokes, brain tumours, and other conditions affecting the brain. In these cases, damage to the hypothalamus disrupts the normal sleep-wake cycle, leading to excessive daytime sleepiness and other symptoms associated with narcolepsy.

Symptoms of Narcolepsy

The four main symptoms of narcolepsy are:

• Excessive daytime sleepiness (EDS): This is a hallmark of narcolepsy and occurs in all people with the condition. EDS involves a sudden, irresistible urge to sleep that can happen multiple times throughout the day.
• Sudden muscle weakness (cataplexy): This can range from mild effects, such as a slight drooping of the eyelids, to severe episodes where the person collapses. Cataplexy is often triggered by strong emotions, especially positive ones like laughter and excitement.
• Sleep-related hallucinations: These can be vivid and frightening, and usually occur when falling asleep or just after waking up.
• Sleep paralysis: The person wakes up but is unable to move or speak, while still being fully conscious. This can be extremely scary and is often accompanied by hallucinations.

Other common symptoms include automatic movements, amnesia or forgetfulness, and sudden outbursts around sleep attacks.

Diagnosis and Treatment

Narcolepsy is diagnosed through a combination of detailed medical history, sleep tests, and a spinal fluid test that checks levels of hypocretin, a key neurotransmitter involved in narcolepsy. While there is no cure for narcolepsy, medications and lifestyle adaptations can help manage the condition. Treatments focus on improving symptoms, reducing risks, and enhancing quality of life.

Can narcolepsy be inherited?

While narcolepsy is not caused by a single gene or genetic variation, it can be inherited. Most cases of narcolepsy are sporadic, with no family history of the disorder. However, in some instances, narcolepsy does cluster in families, indicating that certain forms of the disease may have a strong genetic association.

Narcolepsy is a chronic sleep disorder that disrupts the normal sleep-wake cycle, causing excessive daytime sleepiness. It affects about 1 in 2,000 people in the US and Western Europe, but the worldwide prevalence varies. The disorder likely results from a combination of genetic and environmental factors. Changes in several genes have been associated with narcolepsy, particularly influencing the risk of developing the condition.

The HLA-DQB1 gene, for example, has been strongly linked to narcolepsy, specifically the HLA-DQB1*06:02 variation. This gene is part of the human leukocyte antigen (HLA) complex, which helps the immune system distinguish between the body's proteins and those of foreign invaders. While this variation is present in most people with narcolepsy, it is also found in about 20% of people without the disorder. Therefore, while this gene likely plays a role, it is not the sole cause, and not everyone carrying this variant will develop narcolepsy.

In addition to HLA-DQB1, variations in several other genes have been associated with an increased risk of narcolepsy. Many of these genes are believed to play a role in immune system function. However, it is important to note that these genetic variations likely contribute only a small part to the overall risk of developing the disorder. Other genetic and environmental factors are also at play.

First-degree relatives (parents, siblings, and children) of people with narcolepsy with cataplexy have a 40 times greater risk of developing the condition compared to the general population. This further highlights the potential genetic link, as certain forms of narcolepsy tend to run in families. However, it is worth mentioning that narcolepsy does not follow a clear pattern of inheritance.

What are the symptoms of narcolepsy?

Narcolepsy is a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles. It is a lifelong problem that does not worsen with age, and its symptoms can partially improve over time, but they will never disappear completely.

The symptoms of narcolepsy include:

• Excessive daytime sleepiness (EDS): All individuals with narcolepsy experience EDS, and it is often the most obvious symptom. EDS is characterised by persistent sleepiness, regardless of how much sleep an individual gets at night. This sleepiness is more like a "sleep attack", where an overwhelming sense of sleepiness comes on quickly.
• Cataplexy: This sudden loss of muscle tone while a person is awake leads to weakness and a loss of voluntary muscle control. It is often triggered by sudden, strong emotions such as laughter, fear, anger, stress, or excitement. The symptoms of cataplexy may appear weeks or even years after the onset of EDS.
• Sleep paralysis: The temporary inability to move or speak while falling asleep or waking up usually lasts only a few seconds or minutes and is similar to REM-induced inhibitions of voluntary muscle activity. Sleep paralysis resembles cataplexy, except it occurs at the edges of sleep. As with cataplexy, people remain fully conscious.
• Hallucinations: Very vivid and sometimes frightening images can accompany sleep paralysis and usually occur when people are falling asleep or waking up. Most often, the content is primarily visual, but any of the other senses can be involved.
• Fragmented sleep and insomnia: Individuals with narcolepsy are very sleepy during the day and usually experience difficulties staying asleep at night. Sleep may be disrupted by insomnia, vivid dreaming, sleep apnea, acting out while dreaming, and periodic leg movements.
• Automatic behaviours: Individuals with narcolepsy may experience temporary sleep episodes that can be very brief, lasting no more than a few seconds at a time. A person falls asleep during an activity (e.g., eating, talking) and automatically continues the activity for a short time without conscious awareness of what they are doing.

It is important to note that not everyone with narcolepsy experiences the same symptoms, and the symptoms can develop slowly over a number of years or suddenly over a few weeks.

How is narcolepsy treated?

While there is no cure for narcolepsy, its symptoms can be treated with medications and lifestyle changes.

Medications

• Modafinil is a central nervous system stimulant that is usually the first line of treatment as it is less addictive and has fewer side effects than older stimulants.
• Amphetamine-like stimulants such as methylphenidate can be prescribed in cases where modafinil is not effective. However, these medications must be carefully monitored because they can have side effects.
• Antidepressants such as tricyclics (including imipramine, desipramine, clomipramine, and protriptyline) and selective serotonin and noradrenergic reuptake inhibitors (including venlafaxine, fluoxetine, and atomoxetine) have proven effective in controlling cataplexy.
• Sodium oxybate (also known as gamma hydroxybutyrate or GHB) has been approved by the U.S. Food and Drug Administration (FDA) to treat cataplexy and excessive daytime sleepiness in individuals with narcolepsy. However, due to safety concerns, the distribution of sodium oxybate is tightly restricted.
• Pitolisant is the only non-scheduled product approved by the FDA for treating excessive daytime sleepiness or cataplexy in adults and children aged 6 years and older with narcolepsy. Common adverse reactions in adults include insomnia, nausea, and anxiety, while in children, they include headaches and insomnia.

Lifestyle Changes

• Take short, regularly scheduled naps throughout the day.
• Maintain a strict bedtime routine by going to bed and waking up at the same time every day.
• Avoid caffeine, alcohol, and smoking before bed.
• Exercise daily, leaving at least 2 hours between finishing exercise and going to bed.
• Avoid large, heavy meals before bed.
• Relax before bed with activities such as a warm bath.
• Ensure your bedroom is a comfortable temperature, quiet, and free from distractions.

Can you prevent narcolepsy?

While narcolepsy is not preventable, there are ways to manage the condition and adapt to its effects.

Narcolepsy is a chronic neurological disorder that affects the brain's ability to control sleep-wake cycles. It is a lifelong problem that can greatly affect daily activities. People with narcolepsy may unwillingly fall asleep during the day, even if they are in the middle of an activity. They may also experience sudden muscle weakness (cataplexy), vivid hallucinations, and sleep paralysis.

Although there is no cure for narcolepsy, its symptoms can be treated through a combination of medication and lifestyle changes. Here are some ways to prevent narcolepsy from interfering with your daily life:

• Take short naps: Taking short, scheduled naps throughout the day can help manage excessive daytime sleepiness. A sleep specialist can help you plan a nap schedule that fits your daily routine.
• Maintain a regular sleep schedule: Sticking to a consistent bedtime and wake-up time, even on weekends, can improve sleep quality.
• Avoid caffeine, alcohol, and smoking before bed: Refrain from consuming caffeine, alcohol, or tobacco products before bedtime, as these substances can disrupt your sleep.
• Exercise daily: Engaging in at least 20 minutes of daily exercise, preferably at least four to five hours before bedtime, can improve sleep quality and help maintain a healthy weight.
• Avoid large meals before bed: Eating a heavy meal close to bedtime can disrupt sleep. Opt for a light snack instead if you feel hungry.
• Relax before bed: Incorporating relaxing activities, such as a warm bath, into your bedtime routine can promote sleepiness.
• Take safety precautions: Suddenly falling asleep can be dangerous, especially when driving or operating heavy machinery. Always ensure your safety and the safety of those around you.
• Workplace accommodations: Speak with your employer about potential accommodations, such as flexible work hours or planned naps, to help manage your condition at work.
• Connect with support groups: Reach out to local or national narcolepsy support groups, such as Narcolepsy UK, to seek advice and connect with others living with narcolepsy.
• Medication: Consult with your healthcare provider about potential medications, such as wakefulness medications or stimulants, that can help reduce excessive daytime sleepiness and improve alertness.

Frequently asked questions