Thunderclap headaches: Warning signs and causes


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In the article “Thunderclap headaches: Warning signs and causes,” the experts at UCLA Health shed light on a concerning phenomenon known as reversible cerebral vasoconstriction syndrome (RCVS). This condition can be triggered by various substances, including cannabis, and is characterized by sudden and severe headaches, referred to as “thunderclap headaches.” The article discusses the potential causes, symptoms, and complications associated with RCVS, emphasizing the importance of seeking immediate medical attention for anyone experiencing these symptoms. Furthermore, it addresses the legal implications and limited research surrounding cannabis, urging individuals with severe symptoms to take a break from its use and consult a healthcare provider.

Overview of Thunderclap Headaches


Thunderclap headaches are a specific type of headache characterized by a sudden and severe onset of pain. The pain is often described as explosive or like a thunderclap, hence the name. These headaches can be extremely intense and debilitating, causing significant discomfort and distress for those experiencing them.


In addition to the sudden and severe pain, thunderclap headaches may also be accompanied by other symptoms. These can include nausea and vomiting, sensitivity to light, blurred vision, muscle weakness, and confusion. The intensity and duration of the headache can vary, with some lasting only a few minutes and others lasting several hours.


Thunderclap headaches are relatively rare, accounting for only a small percentage of all headaches. However, they can occur in people of all ages and genders. It is important to note that while thunderclap headaches can occur in isolation, they can also be a symptom of an underlying medical condition or injury.

Warning Signs of Thunderclap Headaches

Sudden and severe headache

One of the key warning signs of a thunderclap headache is the sudden and severe onset of pain. The pain is often described as intense and explosive, reaching its peak intensity within seconds or minutes. This sudden onset can be alarming and may lead individuals to seek immediate medical attention.

Nausea and vomiting

Many individuals experiencing a thunderclap headache may also experience nausea and vomiting. These symptoms can be debilitating and can further contribute to the overall discomfort and distress associated with the headache. It is important to note that not all individuals experiencing a thunderclap headache will experience these symptoms.

Sensitivity to light

Another common warning sign of a thunderclap headache is sensitivity to light, also known as photophobia. This means that individuals may find bright lights or sunlight particularly bothersome and may experience discomfort or pain when exposed to them. It is important to protect the eyes and seek a darkened environment when experiencing this symptom.

Blurred vision

Blurred vision can also be a warning sign of a thunderclap headache. Individuals may notice that their vision becomes hazy or out of focus during a headache episode. This can further contribute to the overall discomfort and may impair daily activities or tasks that require clear vision.

Muscle weakness

Muscle weakness can occur during a thunderclap headache and may affect different parts of the body. Individuals may experience weakness in their limbs, making it difficult to perform everyday tasks. This symptom can add to the overall debilitation associated with the headache.


Confusion is another common warning sign of a thunderclap headache. This can manifest as difficulty concentrating, disorientation, or a general feeling of mental fog. Individuals may find it challenging to think clearly or remember things during a headache episode.

Causes of Thunderclap Headaches

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Reversible cerebral vasoconstriction syndrome (RCVS)

One potential cause of thunderclap headaches is a condition called reversible cerebral vasoconstriction syndrome (RCVS). RCVS is characterized by the sudden constriction (narrowing) of blood vessels in the brain. This constriction can lead to a decrease in blood flow, resulting in the intense pain and other symptoms associated with thunderclap headaches.

Physical changes during and after pregnancy

Certain physical changes that occur during and after pregnancy can also trigger thunderclap headaches. Hormonal fluctuations, changes in blood volume, and alterations in blood flow can all contribute to the development of these headaches. It is important for individuals who are pregnant or have recently given birth to be aware of the risk of thunderclap headaches and seek medical attention if symptoms arise.

Substance triggers

Certain substances, including prescription medications, caffeine, nicotine, illicit drugs, and cannabis, can also trigger thunderclap headaches. These substances can cause changes in blood flow and blood vessel constriction, leading to the development of intense headaches. It is important to be aware of the potential triggers and to avoid or limit their use if thunderclap headaches occur.

Risk Factors for Thunderclap Headaches

Family history of thunderclap headaches

Having a family history of thunderclap headaches can increase an individual’s risk of developing them. There may be genetic factors that predispose certain individuals to the condition. If you have a family history of thunderclap headaches, it is important to be vigilant for any warning signs and seek medical attention if necessary.

Previous history of thunderclap headaches

If you have previously experienced a thunderclap headache, you may be at an increased risk of having another one in the future. It is important to monitor for any recurring symptoms and seek medical attention if they occur.

History of certain medical conditions or procedures

Certain medical conditions and procedures can also increase the risk of developing thunderclap headaches. These can include conditions such as high blood pressure, cardiovascular disease, and certain neurological disorders. Additionally, procedures such as spinal taps or angiograms may also increase the risk. It is important to disclose any relevant medical history to your healthcare provider.

Diagnosing Thunderclap Headaches

Diagnosing thunderclap headaches typically involves a comprehensive evaluation by a healthcare provider. The following are commonly used methods and tests:

Physical exam

During a physical exam, your healthcare provider will assess your overall health and perform a neurological examination to check for any abnormalities.

Medical history

You will be asked about your medical history, including any previous headaches, relevant medical conditions, and exposure to potential triggers.

Family history

Your family’s medical history, especially regarding thunderclap headaches, will be taken into account.

Review of medications and substances used

Your healthcare provider will review any medications and substances you are currently taking or have recently used. This can help identify potential triggers or interactions.

Imaging scans

Imaging scans, such as computed tomography (CT) scans or magnetic resonance imaging (MRI), may be ordered to examine the brain and blood vessels for any abnormalities.

Blood flow and organ function tests

Various blood tests and other diagnostic tests may be conducted to assess blood flow, organ function, and other factors that could contribute to thunderclap headaches.

It is important to undergo a thorough evaluation to accurately diagnose thunderclap headaches and determine any underlying causes or associated conditions.

Complications and Associated Conditions

If left untreated or undiagnosed, thunderclap headaches can potentially lead to various complications and associated conditions. These can include:

Severely high blood pressure

Thunderclap headaches can be a symptom of severely high blood pressure, also known as hypertensive emergency. If left untreated, this condition can lead to organ damage and other serious health issues.

Bleeding in the brain

In rare cases, thunderclap headaches can be a result of bleeding in the brain, such as a subarachnoid hemorrhage. This is a medical emergency that requires immediate attention.

Breach in an artery in the neck

A thunderclap headache can sometimes be a sign of a breach in an artery in the neck, such as a dissection. This can lead to reduced blood flow to the brain and potentially cause a stroke.

Viral or bacterial meningitis

Meningitis is an infection of the membranes surrounding the brain and spinal cord. Thunderclap headaches can be a symptom of this condition, particularly in cases of bacterial or viral meningitis.

Risk of stroke

Thunderclap headaches can indicate an increased risk of stroke, especially if associated with underlying causes such as vasoconstriction or cardiovascular disease. It is important to address the underlying causes and manage the risk factors to prevent stroke.

Treatment Options for Thunderclap Headaches

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Treatment for thunderclap headaches typically involves a combination of supportive care, medication, and management of underlying conditions. The following treatment options may be recommended:

Supportive care

Supportive care measures can include rest in a quiet, darkened room, applying cold or warm compresses to the head or neck, and practicing relaxation techniques. These measures can help alleviate symptoms and promote overall comfort during a headache episode.

Intravenous fluids

In certain cases, intravenous fluids may be administered to ensure adequate hydration and promote blood flow. This can be especially beneficial if dehydration is identified as a contributing factor.

Migraine medication

Medications commonly used to treat migraines, such as triptans or nonsteroidal anti-inflammatory drugs (NSAIDs), may be prescribed to relieve pain and alleviate other symptoms associated with thunderclap headaches.

Calcium channel blockers

Calcium channel blockers can help relax the blood vessels and reduce constriction, potentially alleviating the intense pain associated with thunderclap headaches.

Blood pressure management

If high blood pressure is identified as a contributing factor, medications or lifestyle modifications to manage blood pressure may be recommended. This can help reduce the risk of complications and prevent future thunderclap headaches.

It is important to work closely with a healthcare provider to determine the most appropriate treatment plan based on individual needs and underlying causes.

Legal and Regulatory Considerations for Cannabis Use

Legal status of cannabis

The legal status of cannabis varies by jurisdiction. While some states have legalized the recreational use of cannabis, it remains a Schedule 1 controlled substance under federal law in the United States. This discrepancy between state and federal regulations can have implications for individuals using cannabis and the associated research and medical guidelines.

Constraints on research

The classification of cannabis as a Schedule 1 controlled substance has imposed significant constraints on research into its potential health effects. This has limited the availability of robust scientific evidence and hindered the development of evidence-based guidelines for cannabis use.

Increasing potency of cannabis strains

There is growing concern about the increasing potency of cannabis strains, particularly those high in tetrahydrocannabinol (THC). Higher potency strains may pose a greater risk for adverse effects, including thunderclap headaches. It is important for individuals using cannabis to be aware of the potential risks and to use with caution.

Advice for Individuals Experiencing Thunderclap Headaches

If you are experiencing thunderclap headaches or have any concerns, the following advice may be helpful:

Seek immediate medical attention

Thunderclap headaches can be a symptom of serious underlying conditions, such as high blood pressure or bleeding in the brain. If you experience a sudden and severe headache, it is important to seek immediate medical attention to rule out any life-threatening conditions.

Temporary cessation of cannabis use

For individuals who suspect that cannabis may be triggering their thunderclap headaches, temporary cessation of cannabis use may be advised. This can help determine if there is a correlation between cannabis use and the occurrence of the headaches. However, it is important to consult with a healthcare provider before making any changes to medication or substance use.

Consultation with a healthcare provider

If you are experiencing thunderclap headaches, it is important to consult with a healthcare provider for a comprehensive evaluation and diagnosis. They can assess your individual situation, provide appropriate treatment, and offer guidance on managing the headaches and any underlying conditions.

It is always recommended to seek professional medical advice and follow the recommendations of qualified healthcare providers when dealing with thunderclap headaches or any health concerns.


Thunderclap headaches are a distinct type of headache characterized by sudden and severe pain. They can be a warning sign of various underlying conditions and should not be ignored. Seeking immediate medical attention, managing risk factors, and following a personalized treatment plan are crucial for individuals experiencing thunderclap headaches. By understanding the causes, warning signs, and treatment options, individuals can take proactive steps to address and manage this debilitating condition.



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