Acute Subarachnoid Hemorrhage

Earn CME/CE in your profession:

Continuing Education Activity

Subarachnoid hemorrhages are true emergencies that demand prompt treatment. Subarachnoid hemorrhages result from a medical aneurysmal rupture or traumatic head injury, resulting in bleeding in the subarachnoid space that exists between the arachnoid membrane and the pia mater that surrounds the brain. Unfortunately, subarachnoid hemorrhages are often associated with poor outcomes. Nearly half of patients presenting with a subarachnoid hemorrhage caused by an underlying aneurysm die within 30 days and a third of those who survive have complications. This activity reviews the etiology, pathophysiology, evaluation, and treatment of subarachnoid hemorrhages and highlights the role of interprofessional teams in caring for patients with subarachnoid hemorrhages.


  • Identify the differential diagnosis for subarachnoid hemorrhage.
  • Explain how to evaluate a patient with suspected subarachnoid hemorrhage.
  • Describe treatment considerations for patients with subarachnoid hemorrhages.
  • Summarize the roles of various interprofessional team members in caring for patients with subarachnoid hemorrhages and improving chances for survival and recovery.


A subarachnoid hemorrhage (SAH) results from medical aneurysmal rupture or traumatic head injury.[1] SAH occurs in the subarachnoid space between the arachnoid membrane and the pia mater that surrounds the brain.[1] Patients typically present complaining of a severe headache; however, only 10% of patients presenting to the emergency department complaining of a thunderclap headache end up having a SAH.[1] Associated symptoms may include neck pain, nausea/vomiting, and photophobia.[2] Other similarly presenting diseases include meningitis, migraines, acute narrow-angle closure glaucoma, cerebral venous sinus thrombosis, and non-SAH intracerebral hemorrhage.[2]


Although head trauma causes some cases of SAH, up to 85% is the result of a ruptured saccular aneurysm.[3] These aneurysms often occur within the Circle of Willis and its branches. Other precipitators of a SAH include cocaine abuse, sickle cell anemia, anticoagulation disorders, and dissection of a vertebral artery.[3]

Anyone with a family history consisting of two or more first-degree relatives who have had an aneurysmal SAH will require preventative screening. Additionally, autosomal dominant polycystic kidney disease (ADPKD) is known to be associated with cerebral aneurysms in up to 8% of patients.[3] Therefore, patients with ADPKD also require screening if they have even one family member with a history of a ruptured aneurysm.[3]

Surgical correction of cerebral aneurysms was first introduced in the 1930s, and by the 1990s coiling, and clipping became popular less-invasive treatment options for patients with a SAH. The International Study of Unruptured Intracranial Aneurysms (ISUIA) has established prognostic data for patients with a history of a prior SAH or patients who were found to have an aneurysm as an incidental finding on brain imaging. They have concluded that aneurysms that are smaller than 10 mm or an aneurysm that has never bled are very unlikely to have a SAH and may not require surgical repair as a preventative measure.[4]


Spontaneous SAH happens in about one per 10,000 people per year.[5] Females are more commonly affected than males.[5] Although this clinical entity is more common with older age, about 55% of patients with an SAH present under age 55.[5] Patients are at an increased risk of SAH if they have a history of smoking, hypertension, or excessive alcohol consumption.[6] Up to 10% of patients with a SAH report a history of bending over, lifting heavy objects, or performing other strenuous activities, at the onset of their symptoms.[5]


Saccular aneurysms account for most cases of SAH.[7] These intracranial aneurysms are thin-walled protrusions from an intracranial artery that often has a thin (or absent) tunica media as well as an absent internal elastic lamina.[7] Often hemodynamic stress leads to excessive wear on the wall of these arteries leading to turbulent blood flow within the vessel, which causes structural fatigue and aneurysm development.[7] Hypertension, cigarette smoking, and a variety of connective tissue diseases can also contribute to arterial wall breakdown.[6]

Fusiform aneurysms are caused by dilation of the entire circumference of the vessel, often formed as a result of atherosclerosis.[7] Mycotic (infected) aneurysms often result from emboli due to infective endocarditis.[7] However, these forms of aneurysms are less likely to rupture and cause an SAH than a saccular aneurysm.

Traumatic SAH usually occurs near the site of a skull fracture and intracerebral contusion. Radiologic clues of a traumatic origin include localized bleeding in a superficial sulcus, an adjacent skull fracture, and a cerebral contusion with external evidence of traumatic injury.[8]

History and Physical

Patients presenting with a SAH classically present with a “thunderclap” headache (characterized as a severe rapidly progressing headache that develops within seconds to minutes and has a maximal intensity at its onset), neck stiffness, vomiting, decreased level of consciousness, hemiparesis, and occasionally, seizures.[2] The typical headache pattern is described as a pulsatile pain that propagates towards the occiput.[2] Seizures are more common if an aneurysm causes the SAH, and a SAH in a patient with a history of seizures is often diagnostic of a cerebral arteriovenous malformation.[2]

Neck stiffness typically does not occur until about 6 hours after the onset of a SAH. Asymmetrical pupil size and loss of the pupillary light reflex may indicate brain herniation caused by rising intracranial pressure. Terson syndrome (vitreous hemorrhage as a result of a severe SAH) occurs in anywhere from 3% to 13% of cases.[2] Increased intracranial pressure can lead to a sympathetic surge due to activation of the descending sympathetic nervous system at the medulla, which causes a local release of inflammatory mediators that activate the sympathetic system in the peripheral circulation.[9] This sympathetic surge may lead to an increase in blood pressure, cardiac arrhythmias, and/or cardiac arrest.[9] Electrocardiographic changes may include large U waves, T wave abnormalities, QT prolongation, Q waves, high R waves, cardiac dysthymias, and ST changes (elevation or depression).[9] Neurogenic pulmonary edema may occur if fluid from the pulmonary capillaries leaks into the alveoli as a result of increased pressure within the pulmonary circulation.[9]

Patients may report a history of a head injury before the onset of symptoms or a known history of a cerebral aneurysm. Other risk factors include high blood pressure, smoking, family history, and drug/alcohol abuse.

Patients may also report having a history of a prior severe headache and/or a history of a small bleed with resolving symptoms within the past month. This is considered to be a sentinel bleed, which often precedes a more severe SAH. A headache from a sentinel bleed is extremely difficult to diagnose, as CT and LP can be unreliable in these cases.

Some physical exam findings include an oculomotor abnormality/palsy, which may indicate the posterior communicating artery as the source of the bleed.[2] The patient may demonstrate neck stiffness on examination if there is meningeal irritation from the SAH.[2] In this case, Kernig sign (inability to fully extend the knees when the thigh is flexed at the hip and knee is at 90-degree angles) and Brudinski sign (hip and knee flexion with passive neck flexion) may also be positive.[2]


Generally, if a non-contrast head CT is obtained within 6 hours of symptom onset, the diagnosis can be determined based on this imaging.[10] Almost 99% of cases are picked up on head CT if performed within this 6-hour window.[10] However, MRI is considered to be more sensitive than head CT as time goes on.[1][11]

If the non-contrast head CT is indeterminate, or if the patient presents outside of the 6-hour window, a lumbar puncture (LP) should be discussed with patients.[12] Lumbar puncture has been found in some studies to show evidence of hemorrhage in 3% of patients with a normal head CT.[12] Conversely, a recent study concluded that LP, in their cohort of neurologically intact CT-negative emergency department headache patients, did not identify any cases of aneurysmal SAH but was associated with serious complications, a significant false-positive rate, and extended emergency department length of stay.[12] Thus, attempts to investigate SAH (or sentinel bleeds from a presumed small aneurysmal leak) with CT scan and lumbar puncture should be discussed with patients in a shared decision-making approach with informed consent/refusal.

With regards to laboratory testing, consistently elevated red blood cell counts in all cerebrospinal fluid (CSF) tubes may indicate a SAH. The CSF can also be examined for xanthochromia (yellow appearance to the centrifugate fluid) by spectrophotometry or visual examination.[12] Additionally, the presence of bilirubin within the CSF may also indicate a SAH; however, it takes a minimum of 12 hours for hemoglobin to be metabolized so this method can only reliably detect a SAH 12 hours after its onset.[12]

Lastly, cerebral angiography or CT angiography can be used to identify an aneurysmal source of the bleed. [12]

In 1968, Hunt and Hess established a SAH severity scale based on symptoms at presentation.[13] The Fisher Grade was later created in 1980 to classify the appearance of the SAH based on the appearance of the CT scan.[13] In 1988, the World Federation of Neurosurgeons classification was developed to include the patient’s Glasgow coma score (GCS) and focal neurological deficits to gauge symptom severity.[13] In 1998, Ogilvy and Carter created a comprehensive classification system to help predict outcomes and gauge therapy for patients with a SAH.[14] Lastly, Claassen modified the Fisher Grade scale in 2001 to incorporate the additive risk from a concomitant intraventricular hemorrhage.[13]

Treatment / Management

The first step in the management of a SAH is to stabilize the patient and to get an emergent neurosurgical evaluation.[12] Patients presenting with a decreased GCS may require intubation for airway protection.[15] Blood pressure, pulse, respiratory rate, and GCS must frequently be monitored.[12] Pain control and antiemetics are often required for symptom control.[12]

Once the diagnosis of a SAH is made, most patients will be admitted to a neurosurgical intensive care unit as up to 15% of these patients may have worsening bleeding during their admission.[15][16][15] An external ventricular drain (EVD) may be indicated if the patient has a poor clinical grade on admission, acute neurological deterioration, or progressive ventricular enlargement on CT.[15] This EVD may be used to remove CSF or blood that can cause increased intracranial pressure.[15]

Patients with a large hematoma, decreased level of consciousness, or any focal neurological deficits may require surgical removal of the blood and/or occlusion of the bleeding site.[12] If a cerebral aneurysm is identified on angiography, clipping or coiling can be used to reduce the risk of further bleeding. Clipping requires a craniotomy to visualize and place clips around the neck of the aneurysm. Coiling is an endovascular technique that locates and deploys coils within the aneurysm from a catheter that is inserted into the femoral artery.[17] Aneurysms of the middle cerebral artery tend to be amenable to clipping, whereas those of the basilar artery and posterior cerebral artery are typically more accessible by endovascular coiling.[17] The International Subarachnoid Aneurysm Trial (ISAT) demonstrated a better prognosis from the endovascular coiling of the anterior cerebral artery and anterior communicating artery aneurysms than with clipping. However, coiling carries a slightly increased risk of aneurysm recurrence, so these patients are typically followed for several years with repeat angiography for monitoring purposes.[17]

Early predictors of rebleeding include high systolic blood pressure, the presence of hematoma within the brain or ventricles, poor Hunt-Hess grade, posterior circulation aneurysms, and any aneurysm greater than 10 mm in size.[18] Systolic blood pressure should be kept below 140 to 160 mm Hg to prevent rebleeding.[12] Labetalol is commonly used for this purpose.[12] 

Calcium channel blockers such as nimodipine or nicardipine are often used to prevent vasospasm.[12] Vasospasm can lead to ischemic brain injury (delayed ischemia) as a result of the restricted blood flow caused by vessel constriction.[12] Delayed ischemia often presents with new neurological symptoms and is confirmed by transcranial Doppler or cerebral angiography.[12] A blood flow velocity of more than 120 centimeters per second on transcranial Doppler suggests vasospasm.[19] Up to one-third of patients with a SAH have vasospasm, and about half of these patients have permanent deficits as a result.[19] Nimodipine has been shown to improve patient outcomes if given between the fourth and twenty-first day after bleeding from an aneurysmal SAH. [19] However, nimodipine has not been shown to affect long-term outcomes in traumatic SAH and is therefore not recommended in these cases.

Differential Diagnosis

  • Meningoencephalitis
  • Cluster headache
  • Adult seizures
  • Intracranial hemorrhage
  • Ischemic cerebrovascular accident
  • Migraine
  • Transient ischemic attack


Unfortunately, SAH is often associated with a poor outcome.[20] Nearly half of patients presenting with a SAH caused by an underlying aneurysm die within 30 days, and a third of those who survive have complications. Roughly half of the patients who have had a SAH suffer from some neurocognitive impairment that impacts their quality of life.[21] Over 60% report ongoing and recurring headaches.[21]


Cerebral vasospasm typically occurs after the third day of onset and typically reaches its peak on the fifth to the seventh day.[22][19] Blood products released from the SAH stimulate the tyrosine kinase pathway, which results in smooth muscle contraction of the cerebral arteries leading to vasospasm.[22] If vasospasm does occur, it can be treated with intravenous fluids to achieve a state of hypertension, hypervolemia, and hemodilution.[22] This triad is often referred to as “Triple H.”[22] However, to date, no randomized controlled trials have been conducted to support its utility. If vasospasm continues despite this medical management, angiography may be attempted to identify the site of spasms and administer intra-arterial vasodilator medication or angioplasty with balloon stenting.[22]

Other reported complications of SAH include hydrocephalus, hypopituitarism, cardiac decompensation, fluctuations in blood pressure and electrolyte levels, and seizures.[23][24] It has been reported that seizures occur in up to a third of SAH hospitalizations.[20][17] Although antiepileptic drugs are often given to prevent seizure occurrence, research has yet to show any benefit from its administration.[20] Some studies have suggested a worse prognosis and increased risk of gastric hemorrhage associated with these medications, but the etiology of these findings remains unclear.[20]

Enhancing Healthcare Team Outcomes

SAH is a severe life-threatening emergency that demands prompt treatment. The majority of patients present to the emergency department; thus, the emergency department team must know how to assess the patient and order the appropriate tests. Neurology and a neurosurgical consultation are mandatory. In addition, the intensivist and Neurology ICU nurses must be familiar with the management of these patients. Unfortunately, the disorder carries mortality over 50% irrespective of treatment. Even those who survive are left with severe complications that are disabling. Thus, an ethics team should be involved early on to discuss with the family the options of DNR.[25]

(Click Image to Enlarge)
CT head Subarachnoid Hemorrhage
CT head Subarachnoid Hemorrhage
Contributed by Scott Dulebohn, MD

(Click Image to Enlarge)
STAR sign subarachnoid hemorrhage
STAR sign subarachnoid hemorrhage
Contributed from Liam Flynn and Peter JD Andrews (CC By S.A. 4.0

(Click Image to Enlarge)
Diffuse SAH
Diffuse SAH
Contributed by Sunil Munakomi, MD
Article Details

Article Author

Norah Kairys

Article Author

Joe M Das

Article Editor:

Manish Garg


8/27/2021 9:58:15 AM



Toth G,Cerejo R, Intracranial aneurysms: Review of current science and management. Vascular medicine (London, England). 2018 Jun     [PubMed PMID: 29848228]


Shea AM,Reed SD,Curtis LH,Alexander MJ,Villani JJ,Schulman KA, Characteristics of nontraumatic subarachnoid hemorrhage in the United States in 2003. Neurosurgery. 2007 Dec     [PubMed PMID: 18162891]


Rabinstein AA,Lanzino G, Aneurysmal Subarachnoid Hemorrhage: Unanswered Questions. Neurosurgery clinics of North America. 2018 Apr     [PubMed PMID: 29502715]


Amount of blood on computed tomography as an independent predictor after aneurysm rupture., Brouwers PJ,Dippel DW,Vermeulen M,Lindsay KW,Hasan D,van Gijn J,, Stroke, 1993 Jun     [PubMed PMID: 8506552]


Incidence of subarachnoid haemorrhage: a systematic review with emphasis on region, age, gender and time trends., de Rooij NK,Linn FH,van der Plas JA,Algra A,Rinkel GJ,, Journal of neurology, neurosurgery, and psychiatry, 2007 Dec     [PubMed PMID: 17470467]


Smoking and elevated blood pressure are the most important risk factors for subarachnoid hemorrhage in the Asia-Pacific region: an overview of 26 cohorts involving 306,620 participants., Feigin V,Parag V,Lawes CM,Rodgers A,Suh I,Woodward M,Jamrozik K,Ueshima H,, Stroke, 2005 Jul     [PubMed PMID: 15933249]


Shipman KE,Ramalingam SK,Dawson CH,Yasear ZA, Subarachnoid haemorrhage. Clinical medicine (London, England). 2019 Jan;     [PubMed PMID: 30651258]


Hostettler IC,Werring DJ, Acute convexity subarachnoid hemorrhage: what the neurosurgeon needs to know. World neurosurgery. 2018 Dec 20;     [PubMed PMID: 30580060]


Chatterjee S, ECG Changes in Subarachnoid Haemorrhage: A Synopsis. Netherlands heart journal : monthly journal of the Netherlands Society of Cardiology and the Netherlands Heart Foundation. 2011 Jan     [PubMed PMID: 22020856]


Fragata I,Canhão P, Imaging predictors of outcome in acute spontaneous subarachnoid hemorrhage: a review of the literature. Acta radiologica (Stockholm, Sweden : 1987). 2019 Feb     [PubMed PMID: 29792042]


Nelson SE,Sair HI,Stevens RD, Magnetic Resonance Imaging in Aneurysmal Subarachnoid Hemorrhage: Current Evidence and Future Directions. Neurocritical care. 2018 Oct     [PubMed PMID: 29633155]


Guidelines for the management of aneurysmal subarachnoid hemorrhage: a statement for healthcare professionals from a special writing group of the Stroke Council, American Heart Association., Bederson JB,Connolly ES Jr,Batjer HH,Dacey RG,Dion JE,Diringer MN,Duldner JE Jr,Harbaugh RE,Patel AB,Rosenwasser RH,, Stroke, 2009 Mar     [PubMed PMID: 19164800]


Development and validation of outcome prediction models for aneurysmal subarachnoid haemorrhage: the SAHIT multinational cohort study., Jaja BNR,Saposnik G,Lingsma HF,Macdonald E,Thorpe KE,Mamdani M,Steyerberg EW,Molyneux A,Manoel ALO,Schatlo B,Hanggi D,Hasan D,Wong GKC,Etminan N,Fukuda H,Torner J,Schaller KL,Suarez JI,Stienen MN,Vergouwen MDI,Rinkel GJE,Spears J,Cusimano MD,Todd M,Le Roux P,Kirkpatrick P,Pickard J,van den Bergh WM,Murray G,Johnston SC,Yamagata S,Mayer S,Schweizer TA,Macdonald RL,, BMJ (Clinical research ed.), 2018 Jan 18     [PubMed PMID: 29348138]


A proposed comprehensive grading system to predict outcome for surgical management of intracranial aneurysms., Ogilvy CS,Carter BS,, Neurosurgery, 1998 May     [PubMed PMID: 9588539]


Okazaki T,Kuroda Y, Aneurysmal subarachnoid hemorrhage: intensive care for improving neurological outcome. Journal of intensive care. 2018     [PubMed PMID: 29760928]


Wang A,Ortega-Gutierrez S,Petersen NH, Autoregulation in the Neuro ICU. Current treatment options in neurology. 2018 May 17     [PubMed PMID: 29770889]


Nathan SK,Brahme IS,Kashkoush AI,Anetakis K,Jankowitz BT,Thirumala PD, Risk Factors for In-Hospital Seizures and New-Onset Epilepsy in Coil Embolization of Aneurysmal Subarachnoid Hemorrhage. World neurosurgery. 2018 Jul     [PubMed PMID: 29689391]


Predictors of excellent functional outcome in aneurysmal subarachnoid hemorrhage., Pegoli M,Mandrekar J,Rabinstein AA,Lanzino G,, Journal of neurosurgery, 2015 Feb     [PubMed PMID: 25495745]


The relation of cerebral vasospasm to the extent and location of subarachnoid blood visualized by CT scan: a prospective study., Kistler JP,Crowell RM,Davis KR,Heros R,Ojemann RG,Zervas T,Fisher CM,, Neurology, 1983 Apr     [PubMed PMID: 6682190]


Time Course of Cerebrovascular Reactivity in Patients Treated for Unruptured Intracranial Aneurysms: A One-Year Transcranial Doppler and Acetazolamide Follow-Up Study., Bøthun ML,Haaland ØA,Logallo N,Svendsen F,Thomassen L,Helland CA,, BioMed research international, 2018     [PubMed PMID: 29854773]


Prediction of delayed cerebral ischemia, rebleeding, and outcome after aneurysmal subarachnoid hemorrhage., Hijdra A,van Gijn J,Nagelkerke NJ,Vermeulen M,van Crevel H,, Stroke, 1988 Oct     [PubMed PMID: 3176085]


Prediction of symptomatic vasospasm after subarachnoid hemorrhage: the modified fisher scale., Frontera JA,Claassen J,Schmidt JM,Wartenberg KE,Temes R,Connolly ES Jr,MacDonald RL,Mayer SA,, Neurosurgery, 2006 Jul     [PubMed PMID: 16823296]


Initial and recurrent bleeding are the major causes of death following subarachnoid hemorrhage., Broderick JP,Brott TG,Duldner JE,Tomsick T,Leach A,, Stroke, 1994 Jul     [PubMed PMID: 8023347]


Pituitary dysfunction and association with fatigue in stroke and other acute brain injury., Booij HA,Gaykema WDC,Kuijpers KAJ,Pouwels MM,den Hertog HM,, Endocrine connections, 2018 May 10     [PubMed PMID: 29748174]


Ikawa F,Michihata N,Matsushige T,Abiko M,Ishii D,Oshita J,Okazaki T,Sakamoto S,Kurogi R,Iihara K,Nishimura K,Morita A,Fushimi K,Yasunaga H,Kurisu K, In-hospital mortality and poor outcome after surgical clipping and endovascular coiling for aneurysmal subarachnoid hemorrhage using nationwide databases: a systematic review and meta-analysis. Neurosurgical review. 2019 Apr 2;     [PubMed PMID: 30941595]