Hemicrania Continua: Symptoms, Types, Causes and Treatment

Hemicrania continua is a unique and often misunderstood primary headache disorder. While it is less common than migraines or cluster headaches, its distinct clinical features and dramatic response to specific treatments make it vital for clinicians and patients to recognize. In this article, we’ll explore the symptoms, types, causes, and treatment options for hemicrania continua, backed by up-to-date research findings.

Symptoms of Hemicrania Continua

Hemicrania continua is defined by its hallmark symptom: a continuous, strictly one-sided headache. However, the full spectrum of symptoms is more nuanced and can include a variety of sensory and autonomic disturbances that impact daily life.

Symptom	Description	Frequency/Notes	Source(s)
Unilateral Pain	Continuous, one-sided head pain	Side-locked in most cases	1 2 3 5 6
Pain Exacerbations	Severe pain spikes superimposed on baseline	Often rated 6.5–10/10 in severity	1 2 3 5
Cranial Autonomic	Tearing, nasal congestion, ptosis, flushing	73–97% have at least one autonomic sign	1 2 3 5
Sensory Symptoms	Photophobia, phonophobia, motion sensitivity	Present in majority of patients	1 2 3 5
Migraine-like	Nausea, restlessness, agitation	Common during exacerbations	1 2 3 5

Table 1: Key Symptoms of Hemicrania Continua

Continuous Unilateral Headache

The core symptom is a steady, moderate pain that remains on one side of the head—most often described as "side-locked," meaning it stays on the same side for long periods. In rare cases, the pain may alternate sides, but this is unusual 1 2 3 5 6.

Pain Exacerbations

Superimposed on the constant baseline pain are episodes of much more intense headaches. These exacerbations can be excruciating, with almost all patients rating these spikes as severe to very severe (often 6.5–10/10 on pain scales) 1 2 3. These periods of increased pain may last from minutes to days.

Cranial Autonomic Features

During exacerbations, most patients experience cranial autonomic symptoms, such as:

• Tearing (lacrimation)
• Nasal congestion or rhinorrhea
• Conjunctival injection (red eye)
• Ptosis (drooping eyelid)
• Facial flushing or swelling

Over 70% of patients report at least one such feature, and nearly all experience some autonomic involvement during pain spikes 1 2 3 5.

Sensory and Migrainous Symptoms

Additional symptoms frequently include:

• Sensitivity to light (photophobia) and sound (phonophobia), sometimes affecting only the side of the pain
• Motion sensitivity, restlessness, and sometimes agitation or aggression during severe attacks
• Occasional nausea akin to migraine symptoms 1 2 5

Other Notable Features

• The pain can affect any part of the head or neck, though it is most often felt around the eye, temple, or forehead 5.
• Physical exams and imaging are typically normal, making clinical diagnosis crucial 5.

Types of Hemicrania Continua

While hemicrania continua is defined by its consistent one-sided pain, there are recognized subtypes based on how the disorder behaves over time. Understanding these types can help guide treatment and prognosis.

Type	Defining Feature	Prevalence/Notes	Source(s)
Chronic	Unremitting, continuous from onset	Most common (82%)	1 2 3 5 6
Remitting	Episodes with pain-free intervals	Less common	2 3 5 6
Evolving	Starts remitting, then becomes chronic	Intermediate frequency	2 3 6

Table 2: Types of Hemicrania Continua

Chronic (Unremitting) Type

The majority of patients experience continuous pain from the very beginning, with no extended pain-free periods. This form is sometimes referred to as "hemicrania continua vera" 1 2 3 5 6.

Remitting Type

A minority of patients have episodes of continuous pain that last for weeks or months, followed by complete remissions that can last for days, weeks, or even longer. This pattern is less common 2 3 5 6.

Evolving Type

Some individuals initially experience remitting headaches, which eventually transform into the chronic, non-remitting pattern. This evolution may provide clues about underlying mechanisms and progression 2 3 6.

Diagnostic Importance

Crucially, all types are defined by their absolute response to indomethacin, a nonsteroidal anti-inflammatory drug (NSAID). Without this response, the diagnosis is questioned and alternative explanations should be considered 1 4 6.

Causes of Hemicrania Continua

The exact cause of hemicrania continua remains elusive, but research has uncovered several important clues about potential mechanisms, risk factors, and secondary forms.

Cause/Factor	Description	Notes/Associations	Source(s)
Primary (Idiopathic)	No identifiable cause; most cases	Likely central pain system dysfunction	5 6 7
Genetic Predisposition	Familial cases reported	May share genetic risk with other primary headaches	11
Head Trauma	Onset after injury in some cases	Rare but documented	8
Analgesic Rebound	Overuse of painkillers can trigger HC	Symptoms resolve after withdrawal	10
Secondary Causes	Tumors, structural lesions, systemic disease	Indomethacin response may still occur	9 12

Table 3: Causes and Risk Factors for Hemicrania Continua

Primary (Idiopathic) Hemicrania Continua

Most cases arise without an identifiable cause. HC is considered a primary headache disorder, likely related to dysfunction in central pain processing areas, possibly involving the trigeminal–autonomic reflex and hypothalamic regions 5 6 7.

Genetic and Familial Factors

Although rare, familial clustering of HC has been reported, suggesting that genetic factors may contribute, especially in families with histories of migraine or other primary headaches 11. However, the genetic basis is not yet well defined.

Head Trauma and Secondary Forms

Though uncommon, there are cases where HC appears after head injury (posttraumatic HC) or in association with other conditions:

• Tumors impinging on pain-processing pathways (e.g., paravertebral neurogenic tumor, lung neoplasm)
• Sympathetic chain involvement leading to autonomic dysfunction 8 9 12

In these cases, the headache may resolve when the underlying cause is treated, though indomethacin responsiveness can still help confirm the diagnosis.

Analgesic Overuse (Rebound)

Rarely, chronic overuse of painkillers can lead to a hemicrania continua–like syndrome, which resolves after stopping the offending medications 10.

Pathophysiology Insights

• Activation of trigeminal–autonomic reflexes and hypothalamic involvement are key features in pathophysiology 5 7.
• HC is grouped with trigeminal autonomic cephalalgias (TACs) due to overlapping symptoms and mechanisms 5 7.

Treatment of Hemicrania Continua

The treatment of hemicrania continua is unique in the world of headache medicine because of its absolute and often dramatic responsiveness to indomethacin. However, not all patients can tolerate this medication, and alternative strategies are sometimes necessary.

Treatment Option	Description	Effectiveness/Notes	Source(s)
Indomethacin	NSAID, oral or injectable	Complete relief in most cases	1 2 3 4 5 6 13
COX-2 Inhibitors	Celecoxib, rofecoxib	Effective in some patients	15 16
Other NSAIDs	Piroxicam, others	May help if indomethacin fails	15
Antiepileptics	Topiramate, gabapentin	Used in some cases, variable results	15
Nerve Blocks	Occipital/supraorbital/trochlear blocks	Partial or temporary relief	17
Occipital Nerve Stimulation	Implanted device for severe cases	Effective in indomethacin-intolerant patients	14

Table 4: Treatment Options for Hemicrania Continua

Indomethacin: The Gold Standard

Indomethacin is both a diagnostic and therapeutic agent for HC:

• Absolute response: Nearly all patients experience complete pain resolution, often within days 1 2 3 4 5 6 13.
• Dosing: Initial doses range from 25 to 300 mg/day, with most patients requiring around 84–136 mg/day. Over time, the required dose may decrease 13.
• Safety: Long-term use is generally well tolerated, though gastrointestinal side effects are common; prophylactic acid suppressants (e.g., ranitidine) can help 13.

Alternatives to Indomethacin

Not all patients can tolerate indomethacin due to side effects or contraindications:

• COX-2 inhibitors: Celecoxib and rofecoxib have shown efficacy in some patients, offering a safer GI profile 15 16.
• Other NSAIDs: Drugs like piroxicam or celecoxib may help, though less consistently than indomethacin 15.
• Antiepileptics: Topiramate and gabapentin may be options for prolonged treatment, especially when NSAIDs are unsuitable 15.

Nerve Blocks and Neuromodulation

• Peripheral nerve blocks: Local anesthetic or corticosteroid injections in the greater occipital, supraorbital, or trochlear nerves can provide relief, especially in patients with tenderness in these regions. Benefits may last from weeks to months 17.
• Occipital nerve stimulation (ONS): For medically intractable cases, implantable devices can offer substantial and sustained pain relief, with most patients reporting significant improvement and minimal side effects 14.

Multidisciplinary and Supportive Care

• Exclude secondary causes: Imaging and evaluation for underlying tumors or structural lesions are vital if the clinical picture is atypical or if there are concerning signs 12.
• Medication withdrawal: In cases of analgesic rebound, stopping the offending drugs can result in complete resolution 10.

Conclusion

Hemicrania continua is a uniquely treatable but often under-recognized primary headache disorder. Its diagnosis and management hinge on clinical vigilance and an understanding of its hallmark features.

Key takeaways:

• Hemicrania continua presents as a continuous, strictly one-sided headache with severe exacerbations and frequent autonomic symptoms.
• Most patients experience the chronic (unremitting) type, while remitting and evolving forms are less common.
• The exact cause is unknown, but central pain system dysfunction, genetic factors, trauma, medication overuse, and secondary lesions may all play a role.
• Indomethacin is both diagnostic and therapeutic—its dramatic efficacy sets HC apart from other headaches.
• Alternatives such as COX-2 inhibitors, nerve blocks, and neuromodulation exist for indomethacin-intolerant patients.
• Multidisciplinary evaluation is crucial, especially to rule out secondary causes in atypical cases.

By recognizing hemicrania continua’s distinct features and applying evidence-based treatments, patients and clinicians can achieve significant improvements in quality of life.