It’s All In Your Head! When Is A Headache Dangerous?

Approximately 2 million patients present to United States emergency departments annually, with a primary headache disorder. This presents 2 challenges to emergency departments. First, immediate life-threatening causes of headaches must be excluded. Second, safe, effective and rapid treatment of the headache must be instituted, leading to a timely discharge and appropriate follow-up. This article will be scoped to acute headache, which accounts for up to 3% acute medical unit admissions and up to 8% of emergency department attendances. The chronic headache will be dealt with by another article in this series.

Differentials for an Acute Headache


An acute headache can result from 1 of 5 categories. These are:
  • Thunderclap Headache
  • Headache + Fever
  • Headache + Focal Neurology
  • New Onset Persistent Headache
  • Chronic Headache presenting for Pain Relief

This article will delve deep into each of these 5 types of acute headaches, and delineate the warning signs, or “red flags” which should prompt urgent medical attention.

Thunderclap Headache & New-Onset Persistent Headache

A thunderclap headache, as its name implies, is a sudden onset, severe headache that has been likened to a thunderclap during a thunderstorm. Patients often describe it as the “worst headache of their lives” and frequently attribute a pain score of 10/10 to it. Classically, thunderclap headaches are caused by intracranial bleeds, of which there are 3 main types. The brain is lined by three membranes – the dura, arachnoid and pia mater. Collectively, these are termed “meninges”. Bleeds that occur within the brain substance (parenchyma) itself are dubbed intra-cerebral hemorrhages.

Bleeds which occur outside of the brain substance, but in between these membranes are dubbed subdural, subarachnoid and epidural bleeds respectively. These bleeds may be caused by a variety of pathologies, including but not limited to ruptured berry aneurysms (outpouching of cerebral vessels), traumatic brain injuries and bleeding diatheses (conditions which make someone prone to bleeding; e.g. Warfarin therapy). Thunderclap headaches should always prompt urgent medical attention regardless. In other words, the thunderclap nature of the headache itself is a major red flag. Similarly, even if a headache is not of the “thunderclap” variant, a new-onset persistence warrants urgent medical attention.

Headache + Fever

Patients who present with a headache and a fever should be considered to have meningitis until proven otherwise. Meningitis results from an infection of the lining of the brain (dura, arachnoid and pia mater). Frequently, this is seen in children, the elderly and patients with a compromised immune system (e.g. patients on chemotherapy, transplant medication, or those with human immunodeficiency virus). Sometimes the meningitis is caused by an off-shoot of an infection occurring elsewhere, such as in the inner ear or in the blood (sepsis). Patients with intra-cranial implants such as a ventriculoperitoneal shunt are also predisposed to an increased risk of meningitis. Rarely, brain tumors can manifest as occult meningitis. Meningitis can be rapidly fatal and has a high degree of morbidity and mortality. Some patients will go on to develop permanent neurological deficits if the meningitis is not rapidly addressed. Furthermore, a prolonged bout of meningitis can lead to the development of intra-cerebral abscesses, which are localized collections of pus. These may need surgical intervention for drainage depending on the size, location, and extent of the abscess.

While many infectious diseases such as the common cold or flu can present with headache and fever, they are often accompanied by other symptoms originating from non-neurological systems. For example, in the context of flu – patients will articulate symptoms involving the upper respiratory tract. In this case, the index of suspicion for meningitis is lower. Patients with a primary presenting complaint of headache who are found to have a high fever should be worked up for meningitis. The red flags for a headache and fever are as follows:

  • Primary Presenting Complaint of Headache
  • High Fever (Typically > 101.3°F)
  • Altered Mental State
  • Neurological Deficits (Numbness/Weakness)

Headache + Focal Neurology

Focal neurology implies a deficit of the central nervous system which can be localized. Common focal neurological deficits are weakness or numbness of the limbs or face. Any focal neurological deficit, especially in the setting of a headache, should be worked up urgently. This is because hemorrhagic strokes often manifest with a headache and a neurological deficit. The “golden window” for the treatment of stroke has been established to be 4 hours. This is so for ischemic strokes, which occur because a clot has impeded the flow of blood in one or more of the cerebral vessels. However, hemorrhagic strokes must be managed immediately by a neurosurgical team.

Regardless of whether the stroke is ischemic or hemorrhagic, all patients who are suspected of having a stroke are indicated for an immediate CT scan to characterize the nature of the stroke. Sometimes, patients who have migraine may experience what is known as an “aura”. An aura is characterized by visual symptoms such as blurring of vision, or zig-zag lines appearing in their field of vision. They may also be characterized by blind-spots (scotoma). However, atypical auras also occur infrequently and are characterized by weakness or numbness of the limbs. In this case, the symptoms may mimic a stroke. Still, patients are strongly advised to seek medical attention, unless they are readily able to recognize these symptoms as an atypical aura.

CH1ER Management

At Community Health 1st ER, our team of specialist board-certified doctors are committed to evaluating, diagnosing and managing your headache regardless of the category it falls into. Indeed, radiological imaging plays a pivotal role in excluding life-threatening causes of headaches, such as strokes, bleeds or tumors. To that end, our state-of-the-art radiological facility is well-equipped to promptly deliver the imaging to patients who need it.