What is Thunderclap Headache (Severe Sudden Headache)?
The term ‘thunderclap headache’ or TCH was first used by Day and Raskin. It stems from a 1986 case study about a 42-year-old woman who talked about a severe sudden headache, saying it felt like a “hammer hitting” her head. From this, they inferred that a possible cause of such a headache could be bleeding in the wall of a brain aneurysm, even before it ruptures.
In the third edition of the International Classification of Headache Disorders (ICHD-3), a ‘thunderclap headache’ is listed under ‘other primary headache disorders’. It’s described as a severe headache that comes on suddenly. It feels much like the pain from a ruptured brain aneurysm, yet occurs without any noticeable abnormalities in the brain. However, ICHD-3 mentions that there is limited evidence to conclusively prove that ‘thunderclap headaches’ exist as an independent condition, emphasizing the need for quick and thorough investigations to identify any possible underlying causes.
What sets ‘thunderclap headaches’ apart from other types of headaches isn’t the intensity of the pain, but how quickly the pain reaches its peak. These headaches are often linked to potentially life-threatening causes like a subarachnoid hemorrhage (a type of stroke), making it a medical emergency.
What Causes Thunderclap Headache (Severe Sudden Headache)?
According to a study that looked into the causes of a sudden and severe headache (thunderclap headache), there are over 100 causes of such headaches other than brain aneurysm. Of these, the two most common reasons are subarachnoid hemorrhage (bleeding in the space surrounding the brain) and reversible cerebral vasoconstriction syndrome (a condition characterized by narrowing of the blood vessels in the brain).
Other possible causes of thunderclap headaches can include:
- Bleeding within the brain or under the skull
- Dissecting cervical artery (tearing of the wall of an artery in the neck)
- Stroke or a blood clot in a vein of the brain
- Drop in brain pressure (spontaneous intracranial hypotension), or a sudden increase in blood pressure
- Severe skull infection or complicated sinusitis
- Brain tumor, cyst in the third ventricle of the brain, or pituitary apoplexy (bleeding into or impaired blood supply of the pituitary gland)
- Posterior reversible encephalopathy syndrome (a condition where parts of the brain have difficulty functioning properly due to damage).
Risk Factors and Frequency for Thunderclap Headache (Severe Sudden Headache)
Thunderclap headaches, or TCH, are a bit of a mystery. This type of severe headache is not well understood, partly because we don’t have a lot of data on how common they are. The best information we have comes from studies of specific populations. For instance, a Swedish study found that each year, about 43 out of every 100,000 adults over the age of 18 experience a thunderclap headache.
Separately, an Italian study found that 0.3% of men and women aged 55 to 94 have had a thunderclap headache at some point in their lives. Thunderclap headaches are extremely rare in children, but one study found that just 0.8% of kids aged 6 to 18 who visited a pediatric emergency department were diagnosed with the condition.
Thunderclap headaches can also be tied to other medical conditions, highlighting its complexity. For example, they’re found in 11 to 25% of subarachnoid hemorrhage cases, 5 to 10% of other intracranial hemorrhages, 20% of cervical artery dissection cases, 2 to 16% of cerebral venous thrombosis cases, 15% of intracranial hypotension cases, and 2% of meningitis cases (either bacterial or viral).
This is further complicated by a condition called Reversible Cerebral Vasoconstriction Syndrome (RCVS), which is a group of conditions characterized by severe headaches and brain blood vessel narrowing, with a sudden, intense thunderclap headache being the most common symptom. Because RCVS can cause a variety of different health problems, it’s tough to pin down the true incidence of thunderclap headaches.
Signs and Symptoms of Thunderclap Headache (Severe Sudden Headache)
Thunderclap headaches are serious and potentially life-threatening, often associated with conditions like subarachnoid hemorrhage. They’re seen as a medical emergency, so it’s important to quickly understand the patient’s medical history and physical health. Patients often describe these headaches as the worst they’ve ever had.
A thorough history and neurological exam can help set thunderclap headaches apart from other types of headaches. Thunderclap headaches are unique in the way they rapidly hit their worst level of pain. The key criteria to diagnose them include:
- Sudden onset of severe head pain
- Peak pain intensity reached within a minute
- Headache lasting for at least 5 minutes
- The headache isn’t better explained by another diagnosis
The two most common causes of thunderclap headaches are subarachnoid hemorrhage and reversible cerebral vasoconstriction syndrome (RCVS). Potential triggers for RCVS could include certain drugs, alcohol, injury to blood vessels, and strenuous physical exertion among others.
Multiple severe, brief thunderclap headaches over a few days or weeks often hint at RCVS. On the other hand, a subarachnoid hemorrhage usually happens during everyday activities or even at rest, and may include symptoms like neck pain, sensitivity to light, vomiting, altered mental status, and fainting.
The following are symptoms that could indicate other secondary causes of thunderclap headaches:
- Headaches followed by seizures, altered consciousness, neck pain, fever, sinus pressure, confusion, or vision loss could be due to multiple causes such as brain hemorrhage, artery dissection, venous thrombosis, low brain pressure, meningitis, sinusitis, cysts in brain ventricles, pituitary gland issues, or posterior reversible encephalopathy syndrome.
- Preferring to avoid certain postures such as lying flat or standing up could indicate venous thrombosis or spontaneous intracranial hypotension.
The neurological examination can be categorized using the Hunt Hess scale or the World Federation of Neurological Surgeons scale.
Testing for Thunderclap Headache (Severe Sudden Headache)
If you don’t have other symptoms and your physical exam is normal, that doesn’t mean you can rule out a serious cause of Thunderclap Headaches (TCH). Many conditions can cause TCH, and doctors need to be aware of them because many are severe and can lead to serious health complications.
There are specific steps doctors follow to diagnose causes of TCH, but generally, the first step is a noncontrast head CT scan after the doctor performs a physical exam and takes a detailed medical history. This type of scan assesses for Subarachnoid Hemorrhage (SAH), a condition that can cause TCH. This CT scan can also uncover signs of other brain-related causes of TCH. If needed, they may also use a head and neck CT scan with contrast, which can provide more detail, especially if a neck artery tear or RCVS is suspected.
The timing of the CT scan matters. In the first 6 to 12 hours right after the headache starts, the noncontrast head CT scan can detect SAH with up to 100% accuracy. However, after that, the accuracy declines, reaching only about 50 to 60% after five days. Since TCH could be caused by a brain lesion, before doctors perform a spinal tap, they require brain imaging.
Doctors usually diagnose SAH with a noncontrast head CT scan but may perform a spinal tap if the CT scan is negative but they still suspect SAH. If a CT scan is completed within 6 hours of the headache start, using the Ottawa SAH rule to interpret the scan results in a 95% sensitivity and 100% specificity for SAH. If it’s uncertain after a CT, doctors may use a type of x-ray imaging called digital subtraction catheter angiography (DSA) with 3-dimensional reconstruction, considered the best method for detecting aneurysms.
If a spinal tap is needed, it should be done as soon as possible after the head CT scan. The results are more reliable if performed at least six hours after symptoms start. During the spinal tap, the doctor measures the pressure level, since high pressure could suggest CVT and low pressure might suggest SIH. The doctor also checks the levels of white and red blood cells, protein, glucose, and looks for a condition called xanthochromia. If it’s available, spectrophotometry is preferred, as looking for xanthochromia has a high rate of false negatives. It can also help in avoiding false positives. Spectrophotometry is very sensitive for detecting SAH if the spinal fluid is obtained between 12 hours and 2 weeks after the SAH. Additional tests might be performed for infections of the brain and spinal cord.
If the noncontrast head CT and cerebrospinal fluid tests don’t provide a clear diagnosis, the doctor may order other imaging tests. These could include a brain MRI with contrast, head and neck CT scan with contrast, or a head and neck MRI with contrast. DSA might be used for definitive imaging when RCVS is strongly suspected, or the patient’s condition worsens, and noninvasive methods have been unremarkable.
Treatment Options for Thunderclap Headache (Severe Sudden Headache)
There are only a handful of case studies about primary TCH treatment, and the claim that TCH is a primary disorder lacks strong proof. Therefore, the strategies to treat and manage the condition are mostly targeting secondary TCH. Once the diagnosis is confirmed, the management for secondary TCH should be determined based on the root cause of the condition.
What else can Thunderclap Headache (Severe Sudden Headache) be?
According to the International Classification of Headache Disorders (ICHD-3), in the early stages of Reversible Cerebral Vasoconstriction Syndrome (RCVS), signs of narrowed blood vessels may not be immediately evident. Hence, a diagnosis of probable primary thunderclap headache should not be made hastily or without further investigation.
There are quite a series of other conditions that may exhibit the same symptoms as primary thunderclap headaches. These include primary cough headaches, exercise-induced headaches, and headaches associated with sexual activity. The two most common conditions that could result in secondary thunderclap headaches are Subarachnoid Hemorrhage (SAH) and RCVS.
Other conditions to consider might include bleeding inside the brain, accumulation of blood on the surface of the brain, tearing in the large blood vessels supplying the brain, stroke, cerebral venous thrombosis, spontaneous intracranial hypotension, severe surges in blood pressure, infections within the brain, sinusitis complications, brain tumors, fluid-filled sacs in the third ventricle of the brain (colloid cyst), sudden bleeding into the pituitary gland (pituitary apoplexy), and posterior reversible encephalopathy syndrome (PRES).
What to expect with Thunderclap Headache (Severe Sudden Headache)
Deciding what causes secondary TCH can be tricky due the many potential causes, but the two most frequently seen are SAH and RCVS. We’ll also touch on how this affects children.
Sadly, between 10 to 18% of people suffering from SAH pass away before they can get to a hospital. Within a year, the mortality rate increases to between 35 to 65%. Moreover, 25 to 33% of those who survive experience a decline in their daily activities, overall quality of life, and may also suffer from neurological disabilities.
It’s crucial to understand that “reversible” in RCVS mainly refers to the treatability of the blood vessel tightening, and not necessarily the symptoms. In fact, more than half of patients still experience headaches years after their diagnosis. However, most of the patients with RCVS see their symptoms improve by themselves within days to weeks. The tightening of the blood vessels generally eases off within three months. Luckily, more than 90% of RCVS patients tend to have excellent long-term outcomes.
According to a recent US study, certain factors such as old age, being female, having a stroke, brain edema, irregular heartbeats, and kidney disease can lead to a poor outcome or death in patients with RCVS. Interestingly, being exposed to glucocorticoids can also worsen the outcomes of the disease.
TCH in kids is rare. A study monitoring kids aged 6 to 18 years over a span of 3 years found that all diagnosed cases of TCH followed a harmless course.
Possible Complications When Diagnosed with Thunderclap Headache (Severe Sudden Headache)
Secondary TCH, a type of brain injury, can lead to a variety of complications. These issues often depend on the exact cause of the injury. Such injuries might be due to bleeding within the brain, excessively high pressure inside the skull, the buildup of fluid in the brain (hydrocephalus), brain clots, or delayed loss of blood supply to the brain. Even routine medical complications can have a major impact on patient outcomes, and may include fever, infections in the bloodstream, lung infections from inhaling foreign material (like vomit), heart problems, low red blood cell count (anemia), low sodium in the blood, high blood sugar, and blood clots in deep veins.
In the case of RCVS, a disorder that affects the blood vessels in the brain, one to two-thirds of patients may experience a brain lesion, which is a type of brain damage. This can be an ischemic lesion (caused by lack of blood flow) or hemorrhagic lesion (caused by sudden, spontaneous bleeding), or a combination of both. However, most people with RCVS recover well and regain their independence. While the long-term likelihood of RCVS happening again is low, and if it does it’s typically not severe, it’s worth noting that related anxiety or depression can decrease quality of life.
Preventing Thunderclap Headache (Severe Sudden Headache)
The complexity and variability of conditions that could be causing secondary TCH mean that prevention efforts and patient education depend on the specific diagnosis. Some of the most common causes are linked to the nervous system and blood vessels. Therefore, patients should be made aware of factors they can change to lower their risk for vascular diseases. These include aspects like physical activity, cholesterol levels, diet, blood pressure, weight, diabetes, and smoking.
There are certain groups who might benefit from screening for ruptured aneurysms, a type of blood vessel disorder in the brain. This includes people who have two or more close family members who have had aneurysms, and people with a genetic kidney disorder called autosomal dominant polycystic kidney disease. Before deciding to get a brain scan for aneurysms, it’s essential that patients get enough information to understand whether the screening is right for them.
