Often coined as the “worst headache ever”, a thunderclap headache is an intense form of rapid-onset headache disorder.¹ Thunderclap headaches cause excruciating and debilitating pain, and can sometimes be a symptom of life-threatening conditions such as an intracranial haemorrhage or aneurysm. Therefore, it is essential to recognise a thunderclap headache quickly and seek immediate medical help to prevent severe, possibly fatal complications. The article aims to shed light on what thunderclap headaches are, what can cause them, and how they can be diagnosed and treated. 

Characteristics of thunderclap headaches 

Sudden onset

One of the hallmark signs of thunderclap headaches is how suddenly the pain appears. Normally, the pain becomes its most intense within 60 seconds, and can last anywhere from five minutes to a few hours.² Some patients have described the fast onset of a thunderclap headache as a “sudden explosion” or like a “hammer hitting my head”.¹ It’s different to other types of headaches such as migraines as these usually take some time to build up in intensity. 

Pain intensity 

Another symptom of a thunderclap headache is the intensity of the pain. The discomfort of a thunderclap headache is often extremely intense and debilitating and requires immediate medical attention. 

Other symptoms 

A thunderclap headache is often associated with an array of symptoms, including:²

• Nausea 
• Vomiting 
• Speech problems 
• Sensitivity to light and sound 
• Numbness 
• Weakness 
• Confusion 
• Seizures 

What are the potential causes of thunderclap headaches? 

Whilst a thunderclap headache can be benign, it is critical to seek medical attention as they are usually symptoms of life-threatening medical events. 

All headaches have either a primary or a secondary cause. A primary headache is head pain that is not caused by an underlying condition and is not accompanied by any other symptoms. In terms of thunderclap headaches, some of the primary causes could be a coughing fit or heavy exercise. This form of thunderclap headache is not dangerous and will go away on its own. 

On the other hand, a secondary cause headache is the result of an underlying condition, and is often accompanied by other symptoms. In terms of thunderclap headaches, some of the underlying second causes could include conditions associated with intracranial bleeding. A secondary thunderclap headache is a cause for concern as it can potentially be life-threatening.²

As it’s difficult to identify whether the thunderclap headache is primary or secondary, it is essential to seek immediate medical help. Some of the causes of secondary thunderclap headaches can include: 

Subarachnoid haemorrhage

A subarachnoid haemorrhage causes bleeding between the brain and the surrounding membrane (layer which protects the brain). This is usually due to a ruptured blood vessel from an aneurysm or head trauma. It's the most common secondary cause of a thunderclap headache. This type of headache will also be associated with a stiff neck, loss of consciousness and neurological deficits. A subarachnoid haemorrhage is a life-threatening condition. 

Reversible cerebral vasoconstriction syndrome (RCVS)

RCVS causes the temporary narrowing of the brain's blood vessels. The blood vessels narrow following a spasm, causing them to constrict and disrupt the blood flow into parts of the brain. RCVS-caused thunderclap headaches are often also associated with light and sound sensitivity, nausea, confusion and sometimes seizures - symptoms which are often shared with other causes of thunderclap headaches. RCVS requires immediate medical attention, as prolonged deficiency of blood into areas of the brain can result in severe complications such as ischaemic stroke or white matter disease. 

Cerebral venous sinus thrombosis (CVST)

During CVST, a blood clot forms in the venous sinuses of the brain - preventing the blood from exiting the brain and causing a buildup of pressure. This pressure can cause thunderclap headaches, but can also rupture blood vessels and cause a haemorrhage. CVST, in addition to a headache, is also associated with blurred vision, loss of consciousness, trouble with movement, seizures and even coma. 

Pituitary apoplexy

Pituitary apoplexy causes abnormal blood circulation within the pituitary gland, either due to impaired blood supply or sudden bleeding. Pituitary apoplexy is often caused by another condition, such as a pituitary tumour. Thunderclap headaches associated with pituitary apoplexy are also associated with vision problems due to the pituitary’s close proximity to nerves associated with vision. These symptoms include double vision, drooping eyelids, and partial or full vision loss in either/both eyes. 

Brain aneurysm and head injury: both of these traumas can induce a ruptured blood vessel within the brain, leading to blood loss and associated thunderclap headaches. 

Hypertensive crisis

An extremely high blood pressure may cause damage to blood vessels, including those in the brain, leading to blood vessel rupture and associated thunderclap headache. 

Meningitis and encephalitis

Meningitis and encephalitis infections induce inflammation of the brain membranes and can be also associated with bouts of thunderclap headaches. 

Diagnosis and treatment of thunderclap headaches

Following obtaining a detailed patient history and performing a physical evaluation, imaging techniques such as a CT scan or an MRI will be performed. If a doctor suspects you are having thunderclap headaches, a CT scan would be the imaging test used to detect any bleeding and potential structural abnormalities, allowing a rapid assessment of life-threatening conditions. An MRI scan may be prescribed to obtain more details about a specific blood vessel or brain tissue.¹

Patients may also undergo lumbar puncture to see whether there is blood present in the cerebral fluid, which would indicate internal bleeding. An angiography may also be performed to visualise blood vessels in the brain to pick up aneurysms, vasoconstriction or clots. 

The underlying cause of a thunderclap headache needs to be diagnosed rapidly due to minimise associated complications. Diagnosing the cause of the headache can then determine what treatment will be required on a case-to-case basis. Below are some of the treatment options for the three main causes of thunderclap headaches - subarachnoid haemorrhage, RCVS and CVST: 

Subarachnoid haemorrhage

As this is a life-threatening condition, it typically requires immediate admission to the ICU (intensive care unit). Some of the methods to alleviate bleeding and build-up pressure in the brain include placement of a drainage tube for pressure alleviation, administration of medication to decrease swelling in the skull and medications to control blood pressure. Surgery may be required to remove collected blood in the brain if the haemorrhage was caused by an injury or repair the aneurysm if the haemorrhage was caused by its rupture. 

Reverse cerebral vasoconstriction syndrome (RCVS)

This condition can be resolved by targeting what is causing the vasospasm. One of the most common treatment options for RCVS is the administration of calcium channel blockers. This type of drug prevents the smooth muscle cells lining the blood vessels of interest from flexing, thus preventing a spasm and constriction. 

Cerebral venous sinus thrombosis (CVST)

To treat CVST, doctors may administer anticoagulants to prevent clot formation and thrombolytics to dissolve the already-formed clots. Furthermore, the patient requires close monitoring in the hospital for pressure inside the head and brain activity to prevent further complications. In some cases, surgery is required to manually remove the clot that is blocking the vein. 

Targeting the secondary cause of a thunderclap headache will alleviate the headache itself. Primary cause thunderclap headaches often go away on their own, but medical attention and monitoring are still required to ensure swift recovery and prevent complications. 

Summary

Thunderclap headaches are associated with rapid onset and debilitating pain. Whilst they can be a result of mere overexertion in daily life from intense exercise or a bout of cough, they also can be caused by a serious and life-threatening underlying issue in the brain, often associated with a blood leak.

Regardless of the cause, thunderclap headaches are a medical emergency and require immediate medical attention to prevent grave consequences. Following initial diagnosis via imaging techniques, medical professionals will determine the treatment plan based on the underlying cause of a thunderclap headache.