What Is Hemicrania Continua

Introduction to hemicrania continua

Hemicrania continua is a relatively uncommon primary headache disorder. This disorder is well-defined and can have a profound impact on those who suffer from it. Characterised by continuous, one-sided head pain, often accompanied by autonomic symptoms, this condition is a unique form of chronic headache. Autonomic symptoms arise when there is dysfunction in the autonomic nervous system that regulates a range of involuntary body functions such as blood pressure, breathing and digestion.¹

Due to the continuous nature of this condition, it can massively affect an individual’s quality of life, leading to emotional and physical exhaustion alongside the pain caused by the condition itself.  

Hemicrania continua is considered rare in comparison to more prevalent headache disorders like migraines and tension headaches. While precise global prevalence figures are limited, studies suggest that it accounts for a small fraction of all headache cases, approximately 1-2% of headache cases assessed in specialized headache centres.^2,3

Hemicrania continua can affect individuals of various ages, genders, and demographics. However, it has been observed that this headache disorder more commonly appears during adulthood, typically affecting those aged between 30 and 50, and is more likely to affect those assigned female at birth in nearly a 2:1 ratio.^3,4

Symptoms of hemicrania continua

Hemicrania continua exhibits distinctive symptoms, including

• Continuous Headache: The most prominent symptom is a chronic, constant, and unremitting headache that doesn't go away.³
• One-Sided Pain: The headache pain is typically felt on just one side of the head, either the left or the right
• Variable Intensity: While it's constant, the pain can vary in intensity. It may be mild at times and then become very severe.³ 
• Other Autonomic Symptoms: There might be other symptoms on the same side as the headache, such as;
  • Nasal congestion³ 
  • Runny nose 
  • Ptosis (droopy eyelid)³  
  • Redness in the eye
  • Eye pain³ 
  • Light and sound sensitivity
  • Nausea and vomiting^2,3

Like some other primary headaches, some people with hemicrania continua report that specific triggers can begin an attack or worsen symptoms. This can include factors such as stress, weather changes, or consuming certain foods/drinks.²

These symptoms can be quite debilitating and greatly affect daily life, making it important to seek medical attention for proper diagnosis and treatment. 

Diagnosis of hemicrania continua

Clinical evaluation

Clinical evaluation for hemicrania continua involves a doctor examining symptoms against diagnostic criteria.³ These criteria include

1. Headache that has lasted over three months
2. Exhibits at least one autonomic feature.
3. There is a significant improvement within 72 hours of taking indomethacin (an anti-inflammatory drug). This is known as the Indomethacin test and is used to confirm diagnosis. 

Role of imaging and other tests:

Imaging and other tests are used to confirm the diagnosis by ruling out other possible causes of the headache. This can include; 

• Brain scans (MRI or CT): This helps in the identification of structural abnormalities, such as tumours, which could be causing the headache.³
• Blood Tests: These are used to rule out other underlying conditions or infections. 
• Indomethacin Test: As previously mentioned, Indomethacin is given to a patient to confirm the diagnosis of hemicrania continua A positive result is characterised by a strong positive response to the medication.³ 

Differential diagnosis

Differential diagnosis of hemicrania continua involves ruling out other forms of headaches which can cause similar symptoms. These include:

• Migraines: Whilst migraines can be mistaken for hemicrania continua, migraines are typically episodic attacks, not continual.³  
• Cluster Headaches: These headaches involve similar one-sided pain. However, these headaches are typically intense and episodic with times of remission.³  
• Other primary headaches: Tension headaches or primary stabbing headaches can mimic symptoms similar to hemicrania continua but ultimately exhibit different diagnostic characteristics.³ 
• Secondary headaches: These headaches are caused by other underlying conditions or medication usage.³ 

Subtypes of hemicrania continua

Typical hemicrania continua

Typical hemicrania continua is the most common subtype of hemicrania continua. In this subtype, people experience continuous, one-sided head pain along with autonomic symptoms on the same side of the head.⁴ The pain responds positively to indomethacin, a non-steroidal anti-inflammatory drug (NSAID), which is often used for diagnosis and treatment.⁴

Atypical hemicrania continua

This subtype is less common and doesn't follow all the classic patterns of typical hemicrania continua. It might involve less prominent autonomic symptoms or may not respond well to indomethacin, making it more challenging to diagnose.⁴ Atypical cases may require different treatment approaches.

These subtypes help medical professionals to tailor treatment plans to individual patients and ensure the most effective management of hemicrania continua.⁵ 

Aetiology and risk factors

Whilst the exact cause of hemicrania continua is unknown, it's believed through research that this disorder could be related to abnormalities in certain brain structures. 

While the risk factors for hemicrania continua aren't well-established, there are some factors that might make certain individuals more susceptible. These include:

Traumatic brain injury,

Concussion, or other traumatic brain injuries that have been shown to be a potential cause of hemicrania continua.⁶ In some reports of hemicrania continua, research has identified an increased occurrence of this headache disorder as a result of lesional pathology within the brain tissue.⁶ However, this is a rare cause of the disorder.

Genetic predisposition

To date, there is no confirmation that this headache disorder has a familial genetic link, meaning it is not known to be hereditary. However, there are cases of immediate family members having the disorder, such as parents and children. This may suggest a familial genetic link to developing the disorder, but it has yet to be proven.⁷

As such, more research is required to fully understand the causes and risk factors of hemicrania continua.

Treatment options

The choice of treatment depends on individual patient factors and their response to different therapies so a patient can receive the most suitable treatment plan.

Indomethacin therapy

Indomethacin therapy is the primary and most effective treatment for hemicrania continua. It's a non-steroidal anti-inflammatory drug (NSAID) that often provides significant relief and studies have shown its effectiveness in managing hemicrania continua symptoms.

In some cases, individuals may not respond well to this primary treatment and may experience side effects. These can include fatigue, depression and mood changes, gastrointestinal issues, and nausea.

Alternative medications 

In cases where indomethacin isn't tolerated or effective, other medications including, topiramate, celecoxib, or gabapentin may be considered.³ Treatment may also include antidepressants, such as Tricyclic antidepressants.⁴ This can elevate the psychological strain that this condition can cause. 

Non-pharmacological interventions

Non-pharmacological approaches such as relaxation techniques, biofeedback, or physical therapy may be helpful in managing pain and improving the quality of life for some individuals with hemicrania continua. Clinical trials specifically focused on these approaches are limited but can be considered in conjunction with medical treatment.

Outlook

Pain caused by hemicrania continua can relapse and remit, so it can go and come back throughout an individual's life. Living with this condition may seem difficult due to its impacts on daily life; however, this condition is manageable with treatment. 

This chronic headache disorder requires long-term treatment, with continual management of to help aid and alleviate symptoms. This includes:

• Continuous medication
• Regular follow-up with healthcare providers for monitoring of the disorder. 
• Psychological support due to the disorder’s impacts on mental health
• Management of coexisting conditions, such as stress, anxiety, and depression, alongside headache treatment. 
• Patient education of potential headache triggers, allowing for lifestyle modification to limit potential episodes.
• Exploration of alternative treatments.

Continuing medical care is important when suffering from this condition and is very effective for individuals, with most reporting little to no pain while taking preventative medications. 

Summary

Hemicrania continua is a rare but distinct chronic headache condition characterized by continuous one-sided head pain which is responsive to indomethacin. Autonomic symptoms, like a stuffy nose or droopy eyelid, often accompany the pain. Diagnosis often involves an "indomethacin test" to see if the pain improves with this medication. While this disorder poses challenges, proper diagnosis and management can significantly improve the quality of life for those affected.

If you or someone you know is experiencing symptoms of hemicrania continua, seeking medical care is crucial. Hemicrania continua is a treatable condition, and early diagnosis and proper treatment can provide relief from persistent pain. 

FAQ

How common is hemicrania continua?

It is very rare; in 2018, less than 1000 cases had been reported in scientific journals.³

How is hemicrania continua different from a migraine or a normal headache?

The primary difference between hemicrania continua and other headache conditions is that it is constant, whilst most other headache conditions will have episodes or flare-ups. The other main difference is that hemicrania continua always affects just one side of the head/face, which is unusual in other headaches. It is also accompanied by autonomic symptoms such as a runny nose or eye pain.

Can I inherit hemicrania continua?

Whilst there have been some recorded cases of hemicrania continua running in families, there is currently no genetic evidence to suggest that it can be passed on from parent to child.

What causes hemicrania continua?

Currently, it is not known for certain what causes hemicrania continua, but there is some evidence that the structure of the brain may play a role. Like other headache disorders, it is thought to be made worse by certain triggers, including flashing lights, certain smells or particular foods and drinks, but these tend to be different with each patient.