What Is Thunderclap Headache

Overview

Thunderclap headache, as the name suggests, is an explosive headache that occurs spontaneously and reaches a point of incredible intensity within seconds.^1,2 The condition is often described by people as being the “worst headache ever” and can act as a potential warning sign of deadly damage that occurs within the brain.^1,2 Thunderclap headaches should always be treated as a medical emergency, as until their cause has been confidently identified, they may pose life-threatening.^1,2

Causes of thunderclap headache

The causes of thunderclap headaches are numerous; however, as a general rule, they can be split into either primary or secondary.^1,2,3 This is used to describe whether there is another physical cause (secondary cases) that accounts for the headache, as opposed to whether the cause is unknown or ‘idiopathic’ in primary cases.^1,2,3

Primary – Although primary thunderclap headache is the source of conjecture, there is some belief that in rare cases, thunderclap headache may present despite no clear physical cause.^1,2 In primary cases, the headache may mimic that seen in secondary disease but proves difficult to define as there is no obvious physical cause which would account for this pain.^1,2,3 This is a subject of debate as there is a real risk of being labelled as a primary or ‘benign’ headache, as other secondary causes that may not appear apparent at first can be linked with serious long-term damage to health. 

Secondary – It is understood that thunderclap headaches are most commonly defined as secondary.^1,2 Secondary causes are numerous and may include conditions such as stroke, brain haemorrhages, low pressure within the brain, brain tumours, or problems with the blood vessels supplying the brain.^1,2 The specific cause must be investigated thoroughly as some of these have the potential to be life-threatening, requiring rapid treatment. Two of the most notable secondary causes include:

Subarachnoid haemorrhage (SAH) – This involves potentially catastrophic bleeding from within the brain.^1,2,4 This condition is usually caused by either the rupture of an aneurysm (a weakened area of a blood vessel) or by traumatic damage itself.^1,2,4 Both of these conditions ultimately lead to bleeding within the layers surrounding the brain known as the meninges (specifically the arachnoid membrane and the pia mater).^1,2,4 SAH has the potential to be grave and, therefore, must be identified and treated promptly to preserve life.^1,2,4 

Reversible cerebral vasoconstriction syndrome (RCVS) – This headache may present as a one-off occurrence or may be implicated in repeated episodes over a short period.^{1,2,5,6,7, The Walton Centre}, This cause of this headache may not strictly appear as imminent danger in the same way as a SAH; however, RCVS is linked to potential longer-term complications and may be very distressing to people affected.^1,2,5,6,7, ^{The Walton Centre} RCVS, as the name suggests, involves constriction of the vessels supplying blood to the brain.^{1,2,5,6,7, The Walton Centre} This constriction or ‘squeezing’ affects small portions of these important blood vessels and may be brought on by a variety of factors.^{1,2,5,6,7, The Walton Centre}

Risk factors

Risk factors for thunderclap headaches are numerous and will depend on the specific cause as above.(1,2,3,4,5,6,7) It is important to be mindful of potential triggers in RCVS and primary headache, which may include coughing, exercise, straining whilst on the toilet or exertion during sexual activity.^{1,2,3,4,5,6,7} As well as these triggers, RCVS may also present following exposure to certain medications such as antidepressants (SSRIs), migraine medications (triptans), decongestants used for blocked sinuses, as well as the illicit drugs cocaine and cannabis.^{1,2,3,4,5,6,7, The Walton Centre} Additional risk factors that may be linked to RCVS or SAH may include high blood pressure, high cholesterol, smoking, drinking alcohol, diabetes, family history of aneurysms, or recent childbirth (for those assigned female at birth).^{1,2,4,5, The Walton Centre}

Identifying any specific triggers or events in the run-up to your headache may prove valuable for your medical team in identifying the likely cause of the headache. As well as this, an improved understanding of these triggers may help you prevent your symptoms from recurring, especially in primary cases of thunderclap headaches.³

Signs and symptoms of thunderclap headache

The most obvious symptom, as mentioned throughout, is a severe headache that appears out of nowhere and reaches its maximum intensity in less than 1 minute.^1,2 Thunderclap headaches may also be seen alongside a number of additional symptoms.^{1,2,4,5,8, The Walton Centre} The likes of which will depend on your specific cause of headache:

• Nausea and vomiting
• Sensitivity to light is known as photophobia
• Seizures
• Stiffness in your neck
• Changes in vision
• Neurological changes such as reduced consciousness or difficulty moving limbs 

Diagnosis

The International Classification of Headache Disorders 3rd edition (ICHD-3) is a commonly used diagnostic tool for thunderclap headaches and outlines the major criteria for its diagnosis. It defines a thunderclap headache as being a severe pain that occurs very suddenly and reaches a peak intensity within 1 minute. The headache lasts at least 5 minutes or longer and, most importantly, cannot be better explained as being any other headache outlined in the ICHD-3 guidance.

There is, unfortunately, a lot of overlap in symptoms for the numerous causes of thunderclap headache, and although some of these will show no apparent changes in scans or blood tests, the specialist investigations outlined below must be explored to confidently diagnose and elucidate a cause:^{1,2,5,6,7, The Walton Centre}

• CT scan of your brain as a whole is used to observe whether there is any bleeding within the brain for a diagnosis of SAH.^(1,2,8)  
• Visualisation of blood vessels supplying the brain by either MRA (magnetic resonance
• Angiography or DSA (digital subtraction angiography).^{1,2,4,5,6,7,8, The Walton Centre} These scans help to identify whether there is any damage, malformations (an aneurysm) or any areas of blood vessel constriction.^{1,2,4,5,6,7,8, The Walton Centre} RCVS can be described as having a ‘string of beads’ appearance.^{7, The Walton Centre}  
• CT venogram, a scan used to visualise venous blood vessels surrounding the brain, can help identify whether there is an area of blockage or a clot.⁹  
• A lumbar puncture or ‘spinal tap’ may be used to analyse cerebrospinal fluid removed from your spinal canal. Changes in its colour, known as xanthochromia, may identify that bleeding into the subarachnoid space has occurred (SAH).^{(3,4,8, The Walton Centre)}  

Management and treatment for a thunderclap headache

Management of thunderclap headaches will ultimately depend on their specific cause. As the causes can be numerous, following an accurate diagnosis, your medical team will be able to advise on your most appropriate course of treatment going forward.

For primary causes of a thunderclap headache, treatment may involve several different approaches. Combined use of supportive measures may include medications to help with any pain or sickness you may experience.^2,3 However, it has been argued that the evidence for long-term use of pain relief is limited in chronic bouts of these headaches.^2,3 In addition to these, it has been proposed that the use of some long-term medications may help manage thunderclap headaches either by expediting their resolution or preventing them from recurring. Examples that may be used include the anti-inflammatory medication indomethacin, the blood pressure medication propranolol or the medication to reduce the spasm of problem blood vessels, nimodipine.^2,3

However, in the case of the two most notable causes of secondary thunderclap headaches, management may involve:

SAH – The medications nimodipine or tranexamic acid may be used to try to stabilise your condition, as there is some evidence that these medications may prevent further bleeding of the aneurysm.⁸ However, the most recognised form of treatment involves surgery.^8,10 This surgery can involve a number of different approaches and plays a pivotal role in treatment to stem the bleeding, minimise the damage caused by the bleeding and prevent further ‘rebleeding’ as can often be the case in SAH.^8,10 A common surgical technique called endovascular coiling may be used.10 This involves both a specialist neurosurgeon and an interventional radiologist inserting multiple strands of platinum wire, which help to ‘block off’ the aneurysm and prevent further bleeding from the area.¹⁰  

RCVS – Treatment for RCVS will usually involve a number of supportive medications to help alleviate your symptoms. There is no definitive outline for treatment; over the years, medications which appear to show benefit include nimodipine, as well as other calcium channel blockers, nifedipine or verapamil, which work by causing relaxation of the culprit blood vessels.^{1,2,3, The Walton Centre} As well as these, due to the severe intense pain you may experience, you will be offered pain relief, which may include ibuprofen, paracetamol or stronger medications such as morphine for short periods if needed.^{1,2,3, The Walton Centre}

As with either of the above secondary causes of thunderclap headache, they may be associated with complications such as seizures or stroke (RCVS specifically), and these would require their own appropriate treatment plans and associated medications. 

Complications

Complications of thunderclap headache will depend on its specific cause and may involve a host of ramifications for your long-term health. 

In primary causes, recurrent severe headaches may impact your emotions, your relationships with others or your ability to work and carry out normal activities of your daily living.^11,12 It is then only understandable that this could have a negative effect on your mental well-being.^11,12

Complications from secondary causes of a thunderclap headache may have the real potential to be devastating and long-lasting. Depending on the cause, i.e. RCVS or SAH, major complications could include:^{1,8,13,The Walton Centre}

• Seizures
• Stroke from a clot forming
• Difficulties with speech, cognition, movement, memory and general functioning
• Repeated episodes of aneurysmal bleeding in SAH or bleeding events in RCVS
• Changes in mood or increased anxiety surrounding the event 
• Permanent brain damage

Summary

Thunderclap headache is a very distinctive condition, one that merits immediate medical attention. If you are unfortunate enough to experience the symptoms described above, then the rapid assessment by your medical team will be essential in ruling out a potentially deadly cause. The accurate diagnosis and prompt management of your condition are vital to try and minimise any risks of lasting damage to your health. Depending on the specific cause of your pain, your medical team will be able to outline potential options for your care by a combination of symptomatic management, active treatment of the cause, as well as potential advice, intervention or medication to reduce the risk of recurrence.