What is Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing (SUNCT)?
Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing, commonly abbreviated as SUNCT, is a rare primary headache disorder classified within the group of trigeminal autonomic cephalalgias (TACs). Characterized by brief, severe, unilateral head pain attacks accompanied by prominent cranial autonomic symptoms such as conjunctival injection (eye redness) and lacrimation (tearing), SUNCT represents a distinct clinical entity that poses diagnostic and therapeutic challenges.
Table of Contents
Definition of SUNCT
Short-lasting unilateral neuralgiform headache attacks with conjunctiva injection and tearing ( SUNCT) is a rare headache disorder that is characterized by short, intense episodes of pain on one side of the head, along with eye-related symptoms such as conjunctival injection and tearing. The pain associated with SUNCT is often described as excruciating and can last for seconds to a few minutes at a time, with episodes occurring multiple times per day.
Etiology of SUNCT
The exact causes of Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing (SUNCT) remain largely unknown, and the condition is generally considered a primary headache disorder, meaning it arises without an identifiable underlying structural lesion. However, growing evidence suggests that SUNCT involves dysfunction of the trigeminal-autonomic reflex pathways. This reflex connects the trigeminal nerve, which mediates facial pain and sensation, to the parasympathetic nervous system through structures such as the superior salivatory nucleus and the sphenopalatine ganglion. Hyperactivation of this reflex results in the hallmark unilateral head pain coupled with prominent autonomic symptoms like conjunctival injection and tearing. Functional neuroimaging studies have consistently demonstrated abnormal activity in the posterior hypothalamus during SUNCT attacks, implicating this brain region in the pathogenesis. The hypothalamus plays a central role in modulating pain and autonomic functions, and its dysregulation may trigger the intense, short-lasting attacks characteristic of SUNCT.
Although SUNCT is primarily idiopathic, secondary causes have been documented in some cases, emphasizing the need for thorough investigation. Structural lesions compressing or irritating the trigeminal nerve, such as vascular loops, tumors, or arteriovenous malformations, have been identified as possible triggers. These lesions may provoke abnormal trigeminal nerve excitability and subsequent activation of the trigeminal-autonomic reflex. Additionally, inflammatory or demyelinating diseases affecting the central nervous system, including multiple sclerosis, have occasionally been associated with SUNCT-like headaches. Rarely, infections or other intracranial pathologies may present with similar symptoms.
Overall, while the exact causes of SUNCT are not fully understood, it is believed to be a complex disorder that may have multiple underlying factors, including abnormalities in the trigeminal nerve, blood vessels in the brain, neurotransmitters, and genetics.(alert-passed)
Pathophysiology of SUNCT
The precise pathophysiology of SUNCT remains incompletely understood but is believed to involve activation of the trigeminal-autonomic reflex pathway. This reflex connects the trigeminal nerve — responsible for facial sensation and pain — to parasympathetic outflow via the superior salivatory nucleus and sphenopalatine ganglion, resulting in the characteristic cranial autonomic symptoms.
Functional imaging studies have shown activation in the posterior hypothalamic region during SUNCT attacks, similar to other TACs like cluster headache. The hypothalamus likely plays a central role in modulating trigeminal nociceptive and autonomic pathways. Neurovascular compression of the trigeminal nerve root has also been implicated in some cases, suggesting a possible secondary cause.
Overall, SUNCT is considered a disorder of trigeminal nerve hyperexcitability combined with dysregulated autonomic control.
Signs and Symptoms of SUNCT
SUNCT, or Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing, is characterized by a distinctive pattern of clinical signs and symptoms that set it apart from other headache disorders.
The hallmark symptom is the presence of brief, intense, unilateral head pain typically localized around the eye, temple, or forehead. These pain attacks are sharp, stabbing, or electric shock-like in quality and last only seconds to a few minutes, often ranging between 1 and 600 seconds. Despite their short duration, the attacks can be extremely frequent, occurring dozens of times per day, which can cause significant distress and functional impairment. Unlike some other headache syndromes, the pain in SUNCT does not follow a predictable cyclical pattern but tends to cluster in bouts, with periods of remission and exacerbation.
In addition to the severe unilateral pain, SUNCT is uniquely associated with prominent ipsilateral cranial autonomic symptoms that occur simultaneously with the headache attacks. The most consistent and defining autonomic features are conjunctival injection, which causes redness of the affected eye, and excessive tearing (lacrimation). Patients may also experience nasal congestion or rhinorrhea on the same side as the pain, as well as eyelid edema, ptosis (drooping eyelid), and a sensation of fullness or pressure around the eye. These autonomic signs help differentiate SUNCT from other neuralgiform headaches such as trigeminal neuralgia, which typically lacks such prominent autonomic features.
Patients with SUNCT usually do not report significant neurological deficits between attacks, and the neurological examination is generally normal. However, the intensity and frequency of attacks can severely affect quality of life, leading to sleep disturbances, anxiety, and depression. Importantly, the attacks often occur spontaneously without clear triggers, although in some cases, minor stimuli such as touching the face or head movements may precipitate attacks. Overall, the combination of short-lasting, severe unilateral pain with ipsilateral conjunctival injection and tearing is the hallmark clinical presentation of SUNCT.
Complications of SUNCT
Although SUNCT (Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing) is not life-threatening, it can have profound and debilitating effects on a patient’s quality of life, mental health, and functional ability. The recurrent, severe nature of the headaches, which can occur multiple times per day, often leads to significant distress and disruption.
One of the most important complications is the impact on mental health. Chronic severe pain is well-known to contribute to psychiatric conditions such as anxiety and depression. Patients with frequent SUNCT attacks may develop mood disorders, exacerbated by the unpredictability and intensity of pain episodes. The psychological burden can impair social relationships, reduce coping abilities, and lower overall life satisfaction. Clinical guidelines emphasize the importance of addressing these mental health issues as part of a comprehensive management plan.
The functional impairment caused by SUNCT is another major complication. The severe pain and its frequent recurrence can interfere with daily activities, including employment, education, and social participation. Many patients report missed workdays or decreased productivity, which can result in financial difficulties and social isolation. These social consequences often compound the psychological impact, creating a vicious cycle of suffering.
Another clinically significant complication is medication overuse headache (MOH). Due to the intense pain, patients often rely heavily on acute pain medications such as analgesics or triptans. Overuse of these medications can paradoxically lead to rebound headaches that worsen the headache disorder and complicate treatment. MOH requires careful management, including patient education and sometimes detoxification strategies under medical supervision.
Finally, SUNCT is a rare and frequently under-recognized disorder, leading to a high risk of misdiagnosis or delayed diagnosis. Misdiagnosis can result in inappropriate or ineffective treatments, prolonged patient suffering, and unnecessary healthcare utilization. Delays in diagnosis also postpone the initiation of targeted therapies that can reduce attack frequency and severity. Early recognition and accurate diagnosis by headache specialists improve prognosis and reduce complications. Complications of SUNCT
Although SUNCT (Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing) is not life-threatening, it can have profound and debilitating effects on a patient’s quality of life, mental health, and functional ability. The recurrent, severe nature of the headaches, which can occur multiple times per day, often leads to significant distress and disruption.
One of the most important complications is the impact on mental health. Chronic severe pain is well-known to contribute to psychiatric conditions such as anxiety and depression. Patients with frequent SUNCT attacks may develop mood disorders, exacerbated by the unpredictability and intensity of pain episodes. The psychological burden can impair social relationships, reduce coping abilities, and lower overall life satisfaction. Clinical guidelines emphasize the importance of addressing these mental health issues as part of a comprehensive management plan.
The functional impairment caused by SUNCT is another major complication. The severe pain and its frequent recurrence can interfere with daily activities, including employment, education, and social participation. Many patients report missed workdays or decreased productivity, which can result in financial difficulties and social isolation. These social consequences often compound the psychological impact, creating a vicious cycle of suffering.
Another clinically significant complication is medication overuse headache (MOH). Due to the intense pain, patients often rely heavily on acute pain medications such as analgesics or triptans. Overuse of these medications can paradoxically lead to rebound headaches that worsen the headache disorder and complicate treatment. MOH requires careful management, including patient education and sometimes detoxification strategies under medical supervision.
Finally, SUNCT is a rare and frequently under-recognized disorder, leading to a high risk of misdiagnosis or delayed diagnosis. Misdiagnosis can result in inappropriate or ineffective treatments, prolonged patient suffering, and unnecessary healthcare utilization. Delays in diagnosis also postpone the initiation of targeted therapies that can reduce attack frequency and severity. Early recognition and accurate diagnosis by headache specialists improve prognosis and reduce complications.
Clinical Diagnosis of SUNCT
The diagnosis of Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing (SUNCT) is primarily clinical, relying on a detailed patient history and characteristic symptoms. SUNCT is classified under the trigeminal autonomic cephalalgias (TACs) group and is distinguished by brief, unilateral, severe head pain attacks that typically involve the orbital, periorbital, or temporal regions. These attacks are accompanied by prominent ipsilateral cranial autonomic symptoms such as conjunctival injection (eye redness) and lacrimation (tearing), which occur simultaneously with the headache episodes. The attacks last from 1 second to 10 minutes and may occur dozens or even hundreds of times daily. Patients often describe the pain as stabbing, electric shock-like, or burning.
Diagnostic Criteria
The International Classification of Headache Disorders, 3rd edition (ICHD-3) provides standardized diagnostic criteria for SUNCT to facilitate accurate diagnosis and differentiation from other headache disorders. According to the ICHD-3, the diagnostic criteria for SUNCT include:
🔹 At least 20 attacks fulfilling the following features:
✔ Moderate or severe unilateral orbital, supraorbital, or temporal pain lasting 1–600 seconds.
✔ Attacks occur with a frequency ranging from 3 to 200 per day.
🔹 During attacks, at least one ipsilateral cranial autonomic symptom must be present, including conjunctival injection and/or lacrimation. Other autonomic features like nasal congestion, eyelid edema, or ptosis may also occur, but are not required for diagnosis.
🔹 Attacks are not better accounted for by another diagnosis.
These criteria emphasize the unique combination of short-lasting, unilateral pain and autonomic signs as essential to the diagnosis.
Differential Diagnosis and Investigations
Since SUNCT shares features with other trigeminal autonomic cephalalgias (such as SUNA—Short-lasting Unilateral Neuralgiform headache attacks with Autonomic symptoms, cluster headache) and trigeminal neuralgia, thorough evaluation is necessary to exclude other causes. Trigeminal neuralgia typically lacks the prominent autonomic symptoms of SUNCT, while cluster headaches have longer attack durations and less frequent but more prolonged episodes.
Neuroimaging, preferably magnetic resonance imaging (MRI) of the brain and brainstem with attention to the posterior fossa and trigeminal pathways, is recommended to exclude secondary causes such as vascular compression, tumors, or other structural lesions that may mimic SUNCT or trigger similar symptoms. Although most cases are idiopathic, identifying secondary causes is crucial, as it may alter treatment.
SUNCT diagnosis is predominantly clinical, guided by ICHD-3 criteria emphasizing very short-lasting, frequent, unilateral head pain with ipsilateral conjunctival injection and tearing. Careful history-taking, neurological examination, and neuroimaging are essential to confirm the diagnosis and exclude secondary causes. Early and accurate diagnosis is important for appropriate management and improving patient outcomes.(alert-passed)
Treatment of SUNCT
SUNCT is a rare and challenging headache disorder characterized by frequent, severe, brief attacks of unilateral head pain with prominent autonomic symptoms. Effective management requires a tailored approach focused on both aborting acute attacks and reducing their frequency and severity through preventive strategies.
A. Acute Management
Unlike other headache types, such as migraine or cluster headache, the extremely brief and high-frequency nature of SUNCT attacks makes traditional abortive treatments less effective or impractical. The rapid onset and short duration (seconds to minutes) mean that many medications cannot be administered quickly enough to provide relief during an attack.
🔹 Intravenous Lidocaine is considered one of the most effective options for acute management. Administered under hospital supervision, IV lidocaine infusion can rapidly suppress attacks and is often used for short-term relief during severe exacerbations or in hospital settings. However, due to its need for monitoring and potential side effects, it is not suitable for routine outpatient use.
🔹 Other acute treatments, such as subcutaneous sumatriptan or oxygen therapy, commonly effective in cluster headaches, have generally shown limited or no benefit in SUNCT attacks due to their very short duration.
Because abortive options are limited, much emphasis is placed on preventive management to reduce attack frequency and severity.
B. Preventive Management
Preventive treatment is the cornerstone of SUNCT management, aiming to decrease the number and intensity of attacks and improve quality of life. Multiple pharmacological agents have been tried, although there is no universally effective therapy and response varies among patients.
1. Lamotrigine
Lamotrigine, an anticonvulsant that stabilizes neuronal membranes and inhibits glutamate release, is considered the first-line preventive treatment for SUNCT. Clinical case series and reports have demonstrated a significant reduction in attack frequency and severity in many patients. It is usually started at a low dose and gradually titrated to minimize side effects like rash.
2. Topiramate
Another anticonvulsant, topiramate, has also shown efficacy in some SUNCT patients. It acts through multiple mechanisms, including modulation of voltage-gated ion channels and enhancement of GABAergic inhibition. It may be used alone or in combination with other agents.
3. Gabapentin and Pregabalin
These calcium channel modulators have been used with variable success, primarily aimed at neuropathic pain mechanisms.
4. Other Medications
🔹 Indomethacin: Although a hallmark of paroxysmal hemicrania, indomethacin is usually ineffective in SUNCT and helps differentiate these conditions diagnostically.
🔹 Verapamil: Widely used in cluster headaches, verapamil may have limited benefit in SUNCT but is often trialed due to its relative safety profile.
🔹 Carbamazepine: Sometimes effective but often less so than lamotrigine, with potential for side effects.
C. Interventional Treatments
In refractory cases unresponsive to medications, neuromodulation techniques have been explored:
🔹 Greater occipital nerve block: Some patients experience temporary relief with nerve blocks.
🔹 Sphenopalatine ganglion stimulation or deep brain stimulation: Experimental approaches in specialized centers have shown promise in select cases but are not standard therapy.
D. Non-Pharmacological and Supportive Care
Supportive measures include patient education about the disorder, management of comorbidities, and psychological support due to the impact on quality of life. Since SUNCT attacks can be disabling, multidisciplinary care involving neurologists, pain specialists, and mental health professionals is often beneficial.
It is important to note that the effectiveness of preventive measures can vary from person to person, and a combination of different therapies may be needed to effectively manage SUNCT. It is also recommended to work closely with a healthcare provider to determine the most appropriate treatment plan based on the individual's specific symptoms and medical history.
The treatment of SUNCT focuses on preventive pharmacotherapy with lamotrigine as the preferred first-line agent. Acute attack management options are limited, with intravenous lidocaine reserved for severe cases. For refractory cases, neuromodulatory interventions may be considered. Because SUNCT is a rare and complex disorder, treatment is often individualized and requires careful monitoring for efficacy and side effects.(alert-passed)
Prognosis of SUNCT
SUNCT is a rare but disabling primary headache disorder that presents with extremely frequent and severe unilateral head pain attacks accompanied by autonomic symptoms. The prognosis can vary widely among patients, influenced by factors such as disease duration, treatment response, and comorbid conditions.
Natural Course and Duration
SUNCT often begins abruptly and may persist for months to years. The natural history is variable; some patients experience spontaneous remission or significant improvement after a few years, while others continue to suffer from frequent attacks for extended periods, sometimes lifelong. The episodic versus chronic nature of SUNCT is not as well-defined as in cluster headache, but many cases tend to be chronic with fluctuating intensity and frequency.
Impact on Quality of Life
Despite not being life-threatening, SUNCT can severely impair quality of life. The extreme frequency and severity of attacks—sometimes hundreds per day—lead to significant disability. Patients often report interference with work, sleep, social activities, and emotional well-being. Chronic pain and the unpredictability of attacks increase the risk of anxiety and depression. Thus, SUNCT carries a substantial psychosocial burden even when physical health is otherwise preserved.
Response to Treatment and Long-Term Outcomes
The prognosis is closely linked to treatment responsiveness. While some patients achieve good control with preventive medications like lamotrigine or topiramate, many have partial or poor responses, necessitating ongoing adjustments or use of adjunct therapies. For patients with refractory SUNCT, the disorder remains a chronic challenge.
Interventional therapies, including nerve blocks or neuromodulation, have improved outcomes for a subset of difficult cases, but these are not universally available.
Mortality and Morbidity
SUNCT itself is not associated with increased mortality. However, the disease’s disabling nature and its impact on mental health can lead to secondary morbidity. The risk of medication overuse, headache, or adverse effects from long-term drug therapy should be monitored carefully.
SUNCT’s prognosis is highly variable. While not fatal, it is often chronic and can profoundly affect quality of life due to frequent, severe pain episodes. Early diagnosis and aggressive preventive treatment improve outcomes, but many patients require long-term management. Psychological support and multidisciplinary care are essential components of improving the overall prognosis for those affected.(alert-passed)
