Diagnosing secondary sudden onset (thunderclap) headaches
Similar to primary thunderclap headaches, secondary thunderclap headaches are defined as sudden onset headaches that achieve maximal intensity within one minute. They are severe, occur suddenly, and persist for hours. Thunderclap headaches may be associated with photosensitivity, phonosensitivity, neck stiffness, and nausea with vomiting.
Usually, these are recognized by a patient’s declaring, “this is the worst headache of my life.”
Severe causes of secondary thunderclap headaches
Serious causes of secondary thunderclap headaches include subarachnoid hemorrhage (SAH), cervical artery dissection, stroke, and a hypertensive crisis.
Severe and sudden onset headache may indicate subarachnoid hemorrhage due to aneurysmal rupture or a sentinel bleed from a leaking aneurysm. Intraparenchymal bleeds into the brain tissue also often present with headache.
As we learned earlier, the thunderclap headache syndrome can also be a primary headache type. The primary headache is indistinguishable clinically from thunderclap headache secondary to a subarachnoid hemorrhage.
Rupture of a berry aneurysm
The most common cause of subarachnoid hemorrhage is rupture of a berry aneurysm producing a severe headache which can be associated with loss of consciousness.
Brain CT without contrast is diagnostic if done in the first 12 hours but the sensitivity decreases after that. A lumbar puncture must be done if the patient presents more than 12 hours after onset.
Subdural hematoma is often preceded by trauma, but the hematoma may develop slowly, such that sometimes the inciting event is not recalled. Epidural hematoma is also caused by trauma, but is rapid in development and the incident is very evident.
Cervical artery dissection
Cervical artery dissection most commonly presents with headache and neck pain. The headache usually develops over a 24-hour period. However, in one out of five patients, it presents as a thunderclap headache. The headache often precedes the later, focal, stroke-like neurological symptoms. It occurs ipsilateral to the vessel which is dissecting.
Both ischemic and hemorrhagic stroke may produce a thunderclap headache which can precede other stroke symptoms. The severity and location depends on the location and severity of the ischemia or hemorrhage.
For these reasons, in most cases of thunderclap headache, a formal study of the cervical vasculature is indicated, with CT or MR angiography.
Those patients who suffer from migraine may be more prone to headache as an accompaniment to stroke.
A hypertensive crisis can precipitate a thunderclap headache. Most often the headaches are posterior in location.
Posterior reversible leukoencephalopathy syndrome (PRES) is a consequence of uncontrolled hypertension. It is associated with thunderclap headache, vision loss, altered mental state, and, possibly, seizures. Focal neurological signs and nausea and vomiting also occur.
Benign causes of secondary thunderclap headache
It is important to rule out the more serious causes of a thunderclap headache first, but there are also benign causes such as low cerebrospinal fluid (CSF) pressure, rapid onset migraine, post-coital headache, and exertional headaches.
Low cerebrospinal fluid pressure
Physicians are usually familiar with post lumbar puncture headaches caused by low CSF pressure. This can happen if there is CSF leakage at the puncture site.
Cerebrospinal fluid leaks can also occur spontaneously. The hallmark is a positional headache which occurs and worsens when a patient is upright. Half of all patients who have CSF low pressure headaches will present with a thunderclap headache elicited by assuming an upright posture. This can be steady or throbbing and may be associated with nausea and vomiting, dizziness, visual changes, and neck pain.
Perhaps ironically, a lumbar puncture should be done in the setting of a thunderclap headache to rule out a subarachnoid hemorrhage.
The opening pressure is measured during a lumbar puncture and a low opening pressure is diagnostic of a cerebrospinal fluid leak.
MRI with enhancement often will show diffuse meningeal enhancement.
Rapid onset migraine
Rapid onset migraine is often referred to a crash migraine and the primary feature is the rapidity with which the headache reaches maximal intensity. This diagnosis should not be considered unless the patient has a clear history of migraine headache and other causes of thunderclap headache have been excluded.
Remember to also include in your list of differentials post-coital headache, a thunderclap-like primary headache disorder, which can occur before or with orgasm. These headaches are usually bilateral. Be aware that subarachnoid hemorrhage can also occur with orgasm, so the patient should be evaluated for an aneurysmal bleed upon initial presentation with this type of headache.
Exertional headaches are a primary headache disorder, with a thunderclap-type presentation, precipitated by any type of exercise or high-level physical activity. The headache is pulsating or throbbing and may last anywhere from a few minutes up to 48 hours.
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