Aneurysmal subarachnoid hemorrhage (SAH) is a neurological emergency with high risk of neurological decline and death. Although the presentation of a thunderclap headache or the worst headache of a patient’s life easily triggers the evaluation for SAH, subtle presentations are still missed. The gold standard for diagnostic evaluation of SAH remains noncontrast head computed tomography (CT) followed by lumbar puncture if the CT is negative for SAH. Management of patients with SAH follows standard resuscitation of critically ill patients with the emphasis on reducing risks of rebleeding and avoiding secondary brain injuries.
Key points
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All patients with acute thunderclap headache should be evaluated for subarachnoid hemorrhage.
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Noncontrast computed tomography scanning, the first diagnostic test, is extremely sensitive early after the hemorrhage, but the sensitivity decreases with time.
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Once the diagnosis of subarachnoid hemorrhage has been established, the next steps, which should be coordinated with a neurosurgeon or cerebrovascular specialist, include imaging to define the vascular lesion and identification and prevention of complications such as rebleeding and vasospasm.
Introduction
Subarachnoid hemorrhage (SAH) is simply defined as the extravasation of blood into the subarachnoid space Fig. 1 . Overwhelmingly, the most common cause of SAH is traumatic injury to the brain. Most of the remainder of cases are caused by spontaneous rupture of a blood vessel. The cause of spontaneous SAH can be classified into aneurysmal, nonaneurysmal, and perimesencephalic causes. Because the preponderance of morbidity and mortality related to SAH is from the aneurysmal type, the article focuses on this entity.
Aneurysmal SAH is associated with a 30-day mortality of approximately 45% and 30% of the survivors have significant disabilities. There are few diseases that cause as much difficulty as SAH for emergency physicians. Debate over the recommended diagnostic algorithms exists in the specialties of emergency medicine, neurology, and neurosurgery. Current advances in imaging modalities, fear of invasive diagnostic testing, and a possible debilitating outcome for patients who are misdiagnosed fuel this fervent debate. The low incidence of the disease also complicates matters, because the diagnosis can easily be missed. However, once diagnosed, management of this neurosurgical emergency is less debatable. This article discusses the epidemiology, diagnosis, and management of aneurysmal SAH in the emergency department (ED).
Causes and Incidence
Approximately 80% of nontraumatic SAHs are from a ruptured aneurysm. Other causes of nontraumatic SAH include arteriovenous malformations, moyamoya disease, vasculitis, and amyloid angiopathy. The initial identification of the cause can be important, because the treatments of traumatic SAH and spontaneous nontraumatic SAH can be different. However, this distinction can also be difficult, because the rupture of the aneurysm may have led to the traumatic incident.
The incidence of spontaneous SAH worldwide ranges from 2 to 20 per 100,000 people, with the United States at approximately 10 per 100,000 people or roughly 30,000 patients annually, making it an uncommon disease. SAH is associated with both modifiable and nonmodifiable risk factors ( Table 1 ). Smoking and hypertension are the most widely studied and reported risk factors; however, alcohol abuse (especially recent binge drinking), cocaine use, and caffeine consumption may also play a role. As for nonmodifiable risk factors, female patients and patients with a family history of SAH in a first-degree relative are at increased risk. Some genetic disorders, such as sickle cell disease, alpha1-antitrypsin deficiency, and polycystic kidney disease, can carry an increased risk as well.
| Modifiable Risk Factors | Nonmodifiable Risk Factors |
|---|---|
| Hypertension | Female gender |
| Smoking history | First-degree family member with SAH |
| Alcohol abuse | Autosomal dominant PCKD |
| Cocaine use | Sickle cell disease |
| Caffeine consumption | Alpha1-antitrypsin deficiency |
Symptoms and Clinical Presentation
The classic presentation for SAH is an abrupt onset of severe headache. This single symptom has been reported to be present in up to 97% of people with the diagnosis of SAH. The descriptive terms of abrupt, thunderclap, and worst of life should all elicit concern in emergency physicians when determining the probability of the presence of SAH. Sudden or near-sudden onset, described as maximal pain within minutes, is typical of the headache from SAH.
Depending on the time from headache onset to presentation, the pain may be resolving or even resolved if the initial hemorrhage is small. This so-called sentinel hemorrhage is simply a small leak from an aneurysm. These sentinel hemorrhages can occur 5 to 20 days before the full presentation of the SAH and are reported to be present in 10% to 40% of patients with aneurysmal SAH. Other symptoms of SAH include seizures, loss of consciousness, vomiting, meningismus, or even sudden death. Recent studies report that both seizures and loss of consciousness at the outset of the hemorrhage are associated with a worse prognosis. These patients had a 2.8-fold increase in death or severe disability based on the modified Rankin Scale at 1 year, even when controlling for age, severity at presentation, and aneurysm size.
It is important to recall that the headache, although almost always present, is sometimes overshadowed by other symptoms and this results in misdiagnosis. Prior migraine, present in 12% of the general population, may lead to migraine as an incorrect diagnosis. Facial pain may lead to a misdiagnosis of sinusitis, whereas neck pain may lead to a misdiagnosis of neck strain. Patients with prominent vomiting have been incorrectly diagnosed with gastroenteritis. Increased blood pressure or electrocardiographic abnormalities has resulted in the incorrect diagnosis of hypertensive emergency and resulting fall or trauma can lead the physician to misdiagnose a traumatic SAH. Not working up patients because their headache has responded to various analgesics, including triptans, is another reason for misdiagnosis.
Clinical Decision Rules and Differential Diagnosis
The differential diagnosis for headache, which is one of the most common complaints encountered in the ED, is long (see Ramin R. Tabatabai and Stuart P. Swadron article, “ Headache in the Emergency Department Avoiding Misdiagnosis of Dangerous Secondary Causes ,” in this issue). The description of the headache can be instrumental in the process of determining the next steps in the evaluation of the patient. Like many other chief complaints in the ED, the use of some simple questioning can help to narrow the differential diagnosis and need for further testing. There should always be documentation of the onset, character, severity, and any associated symptoms or findings that accompany the headache. One common mistake is to overlook patients with a chronic headache history who present with a different or more severe headache than the previous headache episodes. In these patients, the history should focus on how well established the chronic headache diagnosis is, and how similar or different the current headache is compared with prior ones.
Historically, the diagnosis of SAH was missed on initial presentation in 20% to 25% of patients. Even recent data specific to the ED suggest that it is missed on the initial presentation about 5% of the time, and this is especially true when the patients are triaged to a lower acuity or seen at a nonacademic hospital. Although SAH should be prioritized on the differential diagnosis of thunderclap headache, other diseases can also present with thunderclap headache, including cerebral or cervical arterial dissection, cerebral venous sinus thrombosis (CVST), and reversible cerebral vasoconstriction syndrome (RCVS) ( Table 2 ).
| Cause | History and Clinical Features |
|---|---|
| Cervical or cerebral artery dissection | Neck pain, abrupt-onset neurologic findings |
| CVST | Hypercoagulable, female gender |
| Meningitis | Fevers, meningismus |
| Acute narrow-angle-closure glaucoma | Painful eye, mid-dilated pupil |
| RCVS | Multiple thunderclap headaches over days, with or without stroke or hemorrhage |
| Hypertensive encephalopathy/Posterior reversible encephalopathy syndrome | Altered mental status with accelerated hypertension, papilledema, or retinal hemorrhages |
| Idiopathic intracranial hypertension | Obesity, papilledema, female gender |
| Pituitary apoplexy | Known pituitary lesion, visual field abnormalities |
Based on the presence, or absence, of certain clinical features, emergency physicians must decide who needs further evaluation for SAH. As stated previously, the incidence of SAH is low and the diagnostic testing can be invasive, leading to some trepidation on the part of emergency physicians to entertain the full work-up. Recent clinical decision rules have been developed and validated to assist in the decision to begin the work-up based on certain clinical features. The most widely studied is the Ottawa SAH Rule ( Box 1 ). Using classic clinical presentations of SAH and follow-up diagnostic testing, the investigators were able to develop a clinical decision rule that was 100% sensitive and 15% specific. The subjects in this study were adult patients greater than 15 years old with no new neurologic deficits, previous history of aneurysm, or recurrent headaches. The presence of any 1 of the following variables (age >40 years, neck stiffness with limited mobility on examination, witnessed loss of consciousness, onset during exertion, and the history of headache with instantly peaking pain) were 100% sensitive for the presence of SAH.
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For alert patients older than 15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour
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Not for patients with new neurologic deficits, previous aneurysms, SAH, brain tumors, or history of recurrent headaches (≥3 episodes over the course of ≥6 months)
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Investigate if 1 or more high-risk variables present:
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Age greater than or equal to 40 years
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Neck pain or stiffness
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Witnessed loss of consciousness
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Onset during exertion
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Thunderclap headache (instantly peaking pain)
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Limited neck flexion on examination
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This rule suggests that all patients with thunderclap headache should undergo work-up for SAH. However, there is no 100% sensitive and specific decision rule to prevent unnecessary diagnostic work-ups, and ultimately the decision to proceed with a diagnostic work-up relies on the clinical gestalt of the treating clinicians.
Clinical Severity Grading Scales
Once the diagnosis of SAH has been confirmed, there are several clinical severity grading scales in use. The most widely used and clinically accepted is the Hunt and Hess Scale ( Box 2 ). Based on characteristics on presentation, this scale is a predictor of mortality to guide surgical risk. The World Federation of Neurological Surgeons has also developed a scale to grade clinical severity of SAH ( Table 3 ). Although this scale also correlates with mortality, it is used more for research purposes and less for clinical outcomes.
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Grade 1: asymptomatic, mild headache
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Grade 2: moderate to severe headache, nuchal rigidity, no focal deficit other than cranial nerve palsy
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Grade 3: mild mental status change (drowsy or confused), mild focal neurologic deficit
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Grade 4: stupor or moderate to severe hemiparesis
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Grade 5: comatose or decerebrate rigidity
Based on initial neurologic examination.
| Grade | Glasgow Coma Scale | Motor Deficit |
|---|---|---|
| 1 | 15 | Absent |
| 2 | 13–14 | Absent |
| 3 | 13–14 | Present |
| 4 | 7–12 | Present or absent |
| 5 | 3–6 | Present or absent |
Introduction
Subarachnoid hemorrhage (SAH) is simply defined as the extravasation of blood into the subarachnoid space Fig. 1 . Overwhelmingly, the most common cause of SAH is traumatic injury to the brain. Most of the remainder of cases are caused by spontaneous rupture of a blood vessel. The cause of spontaneous SAH can be classified into aneurysmal, nonaneurysmal, and perimesencephalic causes. Because the preponderance of morbidity and mortality related to SAH is from the aneurysmal type, the article focuses on this entity.
Aneurysmal SAH is associated with a 30-day mortality of approximately 45% and 30% of the survivors have significant disabilities. There are few diseases that cause as much difficulty as SAH for emergency physicians. Debate over the recommended diagnostic algorithms exists in the specialties of emergency medicine, neurology, and neurosurgery. Current advances in imaging modalities, fear of invasive diagnostic testing, and a possible debilitating outcome for patients who are misdiagnosed fuel this fervent debate. The low incidence of the disease also complicates matters, because the diagnosis can easily be missed. However, once diagnosed, management of this neurosurgical emergency is less debatable. This article discusses the epidemiology, diagnosis, and management of aneurysmal SAH in the emergency department (ED).
Causes and Incidence
Approximately 80% of nontraumatic SAHs are from a ruptured aneurysm. Other causes of nontraumatic SAH include arteriovenous malformations, moyamoya disease, vasculitis, and amyloid angiopathy. The initial identification of the cause can be important, because the treatments of traumatic SAH and spontaneous nontraumatic SAH can be different. However, this distinction can also be difficult, because the rupture of the aneurysm may have led to the traumatic incident.
The incidence of spontaneous SAH worldwide ranges from 2 to 20 per 100,000 people, with the United States at approximately 10 per 100,000 people or roughly 30,000 patients annually, making it an uncommon disease. SAH is associated with both modifiable and nonmodifiable risk factors ( Table 1 ). Smoking and hypertension are the most widely studied and reported risk factors; however, alcohol abuse (especially recent binge drinking), cocaine use, and caffeine consumption may also play a role. As for nonmodifiable risk factors, female patients and patients with a family history of SAH in a first-degree relative are at increased risk. Some genetic disorders, such as sickle cell disease, alpha1-antitrypsin deficiency, and polycystic kidney disease, can carry an increased risk as well.
| Modifiable Risk Factors | Nonmodifiable Risk Factors |
|---|---|
| Hypertension | Female gender |
| Smoking history | First-degree family member with SAH |
| Alcohol abuse | Autosomal dominant PCKD |
| Cocaine use | Sickle cell disease |
| Caffeine consumption | Alpha1-antitrypsin deficiency |
Symptoms and Clinical Presentation
The classic presentation for SAH is an abrupt onset of severe headache. This single symptom has been reported to be present in up to 97% of people with the diagnosis of SAH. The descriptive terms of abrupt, thunderclap, and worst of life should all elicit concern in emergency physicians when determining the probability of the presence of SAH. Sudden or near-sudden onset, described as maximal pain within minutes, is typical of the headache from SAH.
Depending on the time from headache onset to presentation, the pain may be resolving or even resolved if the initial hemorrhage is small. This so-called sentinel hemorrhage is simply a small leak from an aneurysm. These sentinel hemorrhages can occur 5 to 20 days before the full presentation of the SAH and are reported to be present in 10% to 40% of patients with aneurysmal SAH. Other symptoms of SAH include seizures, loss of consciousness, vomiting, meningismus, or even sudden death. Recent studies report that both seizures and loss of consciousness at the outset of the hemorrhage are associated with a worse prognosis. These patients had a 2.8-fold increase in death or severe disability based on the modified Rankin Scale at 1 year, even when controlling for age, severity at presentation, and aneurysm size.
It is important to recall that the headache, although almost always present, is sometimes overshadowed by other symptoms and this results in misdiagnosis. Prior migraine, present in 12% of the general population, may lead to migraine as an incorrect diagnosis. Facial pain may lead to a misdiagnosis of sinusitis, whereas neck pain may lead to a misdiagnosis of neck strain. Patients with prominent vomiting have been incorrectly diagnosed with gastroenteritis. Increased blood pressure or electrocardiographic abnormalities has resulted in the incorrect diagnosis of hypertensive emergency and resulting fall or trauma can lead the physician to misdiagnose a traumatic SAH. Not working up patients because their headache has responded to various analgesics, including triptans, is another reason for misdiagnosis.
Clinical Decision Rules and Differential Diagnosis
The differential diagnosis for headache, which is one of the most common complaints encountered in the ED, is long (see Ramin R. Tabatabai and Stuart P. Swadron article, “ Headache in the Emergency Department Avoiding Misdiagnosis of Dangerous Secondary Causes ,” in this issue). The description of the headache can be instrumental in the process of determining the next steps in the evaluation of the patient. Like many other chief complaints in the ED, the use of some simple questioning can help to narrow the differential diagnosis and need for further testing. There should always be documentation of the onset, character, severity, and any associated symptoms or findings that accompany the headache. One common mistake is to overlook patients with a chronic headache history who present with a different or more severe headache than the previous headache episodes. In these patients, the history should focus on how well established the chronic headache diagnosis is, and how similar or different the current headache is compared with prior ones.
Historically, the diagnosis of SAH was missed on initial presentation in 20% to 25% of patients. Even recent data specific to the ED suggest that it is missed on the initial presentation about 5% of the time, and this is especially true when the patients are triaged to a lower acuity or seen at a nonacademic hospital. Although SAH should be prioritized on the differential diagnosis of thunderclap headache, other diseases can also present with thunderclap headache, including cerebral or cervical arterial dissection, cerebral venous sinus thrombosis (CVST), and reversible cerebral vasoconstriction syndrome (RCVS) ( Table 2 ).
| Cause | History and Clinical Features |
|---|---|
| Cervical or cerebral artery dissection | Neck pain, abrupt-onset neurologic findings |
| CVST | Hypercoagulable, female gender |
| Meningitis | Fevers, meningismus |
| Acute narrow-angle-closure glaucoma | Painful eye, mid-dilated pupil |
| RCVS | Multiple thunderclap headaches over days, with or without stroke or hemorrhage |
| Hypertensive encephalopathy/Posterior reversible encephalopathy syndrome | Altered mental status with accelerated hypertension, papilledema, or retinal hemorrhages |
| Idiopathic intracranial hypertension | Obesity, papilledema, female gender |
| Pituitary apoplexy | Known pituitary lesion, visual field abnormalities |
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