Shaye I. Moskowitz, MD, PhD
DESCRIPTION 
An intracerebral bleed in which blood is primarily between the arachnoid and pial layers. This is not necessarily limited to this space and can be associated with subdural, intraparenchymal, or intraventricular blood. This type of nontraumatic bleed is most classically and most commonly associated with a ruptured cerebral aneurysm.
EPIDEMIOLOGY
Incidence
Incidence: Subarachnoid hemorrhage (SAH) occurs in an estimated 6–16 per 100,000 people. Approximately 30,000 cases occur in the USA per year.
Prevalence
Cerebral aneurysms occur in an estimated 1–9% of the population on the basis of limited autopsy and imaging studies. Most, however, do not become clinical significant.
RISK FACTORS
- Both controllable and uncontrollable factors exist.
- Smoking, heavy alcohol use, and certain street drugs contribute. Poorly controlled hypertension is a risk factor as well.
- Family and personal history of SAH, female gender, aneurysm details including size, location, and morphology.
Genetics
Aneurysms themselves have a familial link as do their rupture. This is an active area of research. Specific genes are not well understood at this time.
PATHOPHYSIOLOGY
The rupture of an aneurysm results in the release of blood into the subarachnoid space temporarily. Continuous bleeding is ultimately not possible in a confined space and as such results in rapid death. Should the bleeding be brief, potentially stemmed by the sudden rise in intracranial pressure, the patient may survive to present for medical attention. Rerupture is possible and often fatal.
ETIOLOGY
The etiology of aneurysms in general is not completely well known. Most do not rupture and most likely never are identified. It remains unknown why some ultimately progress to rupture, though considerations may be flow dynamics into the aneurysm and stress on the vascular wall.
COMMONLY ASSOCIATED CONDITIONS
Aneurysms are associated with certain collagen vascular diseases, including Ehlers–Danlos and Marfans, and with polycystic kidney disease. Rupture specifically has not yet been associated with any diseases.
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HISTORY
- The classic presentation for a SAH is headache. This is often described as the “worst headache in my life.” Headaches can be varying in intensity however and may be a reflection of the patient and size of the hemorrhage.
- Seizure, loss of consciousness, and focal findings are possible as well, though should be differentiated from many other neurological disorders.
PHYSICAL EXAM
- Neurological findings often include meningismus, as a result of the irritation from the blood in the subarachnoid space.
- Findings are varied and range from normal to comatose with focal findings.
- A normal exam with an acute cranial nerve 3 palsy is potentially a sign for a posterior communicating artery aneurysm.
DIAGNOSTIC TESTS AND INTERPRETATION
Lab
Initial Lab Tests
- Routine lab work including serology and chemistries and coagulation profiles are standard. No specific finding is pathognomonic.
- Lumbar puncture when performed should reveal xanthochromia on spun samples. Additionally, continued high red cell counts through multiple tubes may be a reflection of a SAH as well.
Follow-Up & Special Considerations
- Monitoring for serum sodium levels is important in the care of these patients as cerebral salt wasting is common, resulting in hyponatremia.
- Additional hospital-acquired infections and medical complications are common, and surveillance is critical.
Imaging
Initial Approach
- A non-contrast enhanced CT scan is usually definitive with a clear pattern of blood in the basal cisterns. An MRI may similarly be definitive, though is not the usual first image mode considered.
- Hydrocephalus should be a focus on these tests as well, as this is common.
- Vascular imaging to evaluate for an aneurysm follows. This can include a CT-, an MR-, or a formal catheter angiogram.
Follow-Up & Special Considerations
- Serial CT scans to monitor for delayed or progressive hydrocephalus are routine. This may be performed with or without clinical symptoms.
- Transcranial Doppler ultrasonography is performed to detect or monitor for cerebral vasospasm, usually occurring between 4 and 14 days post-ictus. Imaging tests including catheter angiography, CT, or MR angiography may be considered as well.
Diagnostic Procedures/Other
Catheter angiography may be needed for aneurysm evaluation and for consideration of treatment options. With improving noninvasive imaging modes, this is not necessarily required.
DIFFERENTIAL DIAGNOSIS
- Many headaches can present with acute severe headache, including most commonly thunderclap headaches. Evaluation however may not reveal a SAH or aneurysm on imaging or xanthochromia on lumbar puncture.
- The severity of the diagnosis of SAH often prompts very extensive evaluations of other headaches.
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MEDICATION
First Line
- Initial management is directed at neurological and hemodynamic stabilization. Critical care is standard. Reversal of any coagulopathy and antiplatelet regimen is standard.
- Aggressive blood pressure control into a normal range is standard.
Second Line
- Nimodipine is routinely used in the care of SAH patients continuously in the management of cerebral vasospasm.
ADDITIONAL TREATMENT
General Measures
Supportive care in a critical care unit is appropriate for the many systemic complications possible during their care.
Issues for Referral
A neurosurgeon should be immediately consulted.
COMPLEMENTARY AND ALTERNATIVE THERAPIES
- Alternative therapies are not appropriate for SAH.
- Placing patients in a relaxing and quiet environment is considered standard. It is not known whether this reduces the risk of rerupture.
SURGERY/OTHER PROCEDURES
- Early definitive treatment is standard. Options include craniotomy for surgical clipping and endovascular coil embolization.
- Many considerations impact the treatment mode of choice, and decisions should be made with a neurosurgeon and endovascular interventionalist in concert.
- Monitoring of intracranial pressure with a ventriculostomy or bolt may be needed.
- Many additional modes of brain monitoring may be applied, including tissue oxygenation, though are less common and require specialized neurological units.
IN-PATIENT CONSIDERATIONS
Initial Stabilization
- Blood pressure and hemodynamic control are standard. Cardiac stunning is common as well and may result in significant hemodynamic variability. Hypertension as a result of intracranial hypertension may occur as well and should be controlled.
- Respiratory support with ventilator assistance is appropriate for the patient with a depressed level of consciousness and lost airway control.
- Placement of a ventriculostomy for treatment of hydrocephalus is important and should be performed early if possible.
Admission Criteria
Patients with the diagnosis or presumed diagnosis should be admitted to the hospital for evaluation and management.
IV Fluids
- Adequate hydration is less important at the initial phase of management.
- However, delayed cerebral vasospasm is worsened by inadequate hydration. It is therefore common to maintain adequate hydration for all patients.
Nursing
- Many aspects of the patient require monitoring, and a skilled nursing team is needed. Frequent neurological exams are critical for detecting subtle changes suggestive of problems is standard, and often relies on well-trained neurological nurses.
- Systemic and intracranial catheters and intravascular monitors are routine and require standard precautions and care. Intracranial monitors similarly require specialized training and handling.
Discharge Criteria
- Discharge occurs when the patient is no longer at risk for the development of cerebral vasospasm and systemic and neurological issues have stabilized.
- Individual patients may be discharged home or to a longer care or rehabilitation facility depending upon their physical and neurological condition.
- Hospital courses routinely at 1–3 weeks.
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FOLLOW-UP RECOMMENDATIONS
- Follow-up for the aneurysm is routine to evaluate for recurrence or development of additional aneurysms. This is not well understood and many practice patterns exist.
- Aneurysms treated with coil embolization should be followed more aggressively than clipped aneurysms for recurrence, though no standard exists.
DIET
No special diet is required, though formal swallow evaluations are reasonable and should be performed for all stroke patients.
PATIENT EDUCATION
- Importance of smoking cessation should be emphasized.
- Follow-up care and aneurysm reimaging are important to prevent missing a recurrence.
PROGNOSIS
- SAH is fatal in
of all patients at the time of the ictus, never presenting to medical attention for care. - Of those who present, die during the hospital course, survive with significant neurological injury, and return to full function.
- Rerupture is fatal in the majority of the time.
COMPLICATIONS
- Systemic and neurological complications are common.
- Delayed hydrocephalus is common as well.
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