Abstract
This chapter covers the diagnosis and management of spontaneous subarachnoid hemorrhage due to rupture of intracranial aneurysms. At the end of the chapter we also discuss unruptured intracranial aneurysms. Much SAH management is not based on good-quality evidence. Much of what is recommended here comes from published practice guidelines and what is commonly practiced. Options for therapy might be limited by the availability and experience of persons performing surgery, endovascular therapy, and neurointensive care.
This chapter covers the diagnosis and management of spontaneous subarachnoid hemorrhage due to rupture of intracranial aneurysms. At the end of the chapter we also discuss unruptured intracranial aneurysms. Much SAH management is not based on good-quality evidence. Much of what is recommended here comes from published practice guidelines and what is commonly practiced.1 Options for therapy might be limited by the availability and experience of persons performing surgery, endovascular therapy, and neurointensive care.
Definition
Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space around the brain. Trauma is the most common cause of SAH. We do not discuss traumatic SAH in this chapter. This chapter covers spontaneous SAH, 80% of which are due to intracranial saccular aneurysms.
Epidemiology
3% of all strokes but 5% of stroke deaths.
Incidence 10–15 per 100 000 person-years in the USA, with higher risk among African-Americans. Worldwide, higher incidence reported in Japan and Scandinavia.2
Females have higher incidence (60% of patients are female).
Modifiable risk factors: hypertension, tobacco use, oral contraceptives, alcohol, and stimulants.
Non-modifiable risk factors: older age (peak is 50–60 years old), female sex.
Other diseases associated with aneurysms: polycystic kidney disease, Marfan syndrome, Ehlers–Danlos syndrome, coarctation of the aorta, fibromuscular dysplasia.
Location: 30% anterior communicating, 25% posterior communicating, 20% MCAs, 10% basilar, 5% vertebral, and 25% have multiple aneurysms.
Presentation
Diagnosis
As this condition is potentially life-threatening, diagnostic evaluation should be done emergently.
Diagnosis of Subarachnoid Hemorrhage
CT of the head without contrast
▪ In the first 6 hours, the sensitivity of non-contrast CT is 100%. By 72 hours, it is > 97% and, by day 5, it goes down to about 50%.
▪ If head CT is normal, but you have a high clinical suspicion for SAH, you must do a lumbar puncture, because CT can miss small or subtle SAHs, especially if more than 72 hours has passed since the ictus.3
Lumbar puncture
▪ Don’t forget to personally examine the fluid for xanthochromia. Compare the color to water. Measure red blood cells in first and last tube collected. Also, it is often helpful to personally deliver the tubes of CSF to the lab to make sure that they are processed quickly.
▪ The other parameters in the CSF (glucose, protein, WBC) will help you rule out meningitis.
MRI brain
Diagnosis of Intracranial Aneurysms
Digital subtraction angiography (DSA) – the gold standard. If the DSA is negative and the suspicion for aneurysm is high, repeating the DSA in a few days can increase the yield by 10%.
CT angiography (CTA) – sensitivity 98%, but depends on CT equipment. Difficult to see aneurysms near bones.
MR angiography (MRA) – fair test for screening for unruptured aneurysms > 5 mm.
Causes of SAH Other Than Intracranial Aneurysms
Perimesencephalic SAH – blood limited to anterior to midbrain (or pons) and can reach the medial aspects of the sylvian fissures. Angiogram is negative for aneurysms. The cause of the bleed is unknown (venous?). It carries a good prognosis and a benign course.
Arteriovenous malformation (AVM) – it classically causes intraparenchymal hemorrhage, but it can lead to SAH. DSA will help in diagnosis.
Arterial dissection (vertebral artery usually) – arterial dissection that extends from the extracranial to the intracranial portion of an artery or is limited to the intracranial artery can lead to SAH. This can occur spontaneously or it may be post-traumatic. DSA and MRI can be helpful in visualizing the abnormality.
Arteriovenous fistula – can be seen only with careful DSA.
Pituitary apoplexy – MRI is helpful in making the diagnosis.
Sympathetic mimetic agents (e.g., cocaine) – can lead to SAH, ICH, or cerebral ischemia.
Trauma – detailed history or external head examination may suggest trauma as the primary cause. Often located along convexities or in association with subdural hematoma.
Vasculitis – difficult to diagnose, since DSA is neither sensitive nor specific and brain biopsy is specific but insensitive.
Management of Ruptured Aneurysms
Goals
Prevention of rebleeding.
Treatment of the aneurysm itself: clipping or coiling.
Prevention and treatment of complications: hydrocephalus, seizure, cardiac ischemia or arrhythmia, vasospasm, hyponatremia, infections, DVTs.
Rehabilitation.
Prevention of Rebleeding
Rebleeding is maximal in the first 24 hours after SAH (4%). It carries a high mortality.
Securing the aneurysm with coiling or clipping as early as possible is the single most important preventive measure against rebleeding.
Independent predictors of rebleeding are: pre-existing hypertension, basilar artery location of the aneurysm, size ≥ 9 mm, acute hydrocephalus, and presence of ICH.4
The following measures are often taken, but without much evidence:
▪ Blood-pressure control is important before definitive treatment to reduce rebleeding. MAP goal is 70–100 mmHg, significantly lower than with other stroke syndromes.
▪ Bed rest in ICU with monitoring.
▪ Prevention of pain, nausea/vomiting, straining/constipation, dyssynchrony with the ventilator.
Antifibrinolytic drugs (epsilon-aminocaproic acid, tranexamic acid) reduce rebleeding but promote ischemic/thromboembolic complications, and therefore their use is usually limited to 72 hours or until the aneurysm gets treated. These drugs are rarely used, because of their complications.
Treatment of the Aneurysm Itself
This should be done as early as possible, especially in patients with mild to moderate clinical deficits, since the goal is to prevent rebleeding.
1. Surgical Clipping
Craniotomy and placement of a metal clip takes the aneurysm out of the arterial circulation.
It is believed to be the best way to prevent aneurysmal bleeding long-term.
More advantageous than coiling if:
a. the aneurysm has a wide neck (high neck-to-dome ratio).
b. the aneurysm is either large (> 15 mm) or giant (> 24 mm).
c. the SAH is associated with an intraparenchymal clot that needs evacuation.
d. the aneurysm is located too distally and is therefore not accessible by endovascular means.
e. multiple aneurysms need treatment.
Drawbacks of the procedure:
a. Aneurysms in the posterior circulation are not easily amenable to open surgery.
b. Requires general anesthesia, and therefore patients with comorbidities may not be good candidates.
c. Carries higher mortality/morbidity rate than coiling.
2. Endovascular Coiling
Coiling has become the alternative treatment. When you fill the aneurysm with coils, it thromboses, and effectively takes the aneurysm out of the arterial circulation.
Advantages:
a. Subsequent rebleed rate is not as low as with surgical clipping, but pretty close.
b. Can address posterior circulation aneurysms.
c. Less invasive and carries less mortality/morbidity than clipping.
Disadvantages:
a. Not as durable as clipping. Long-term data are not available.
b. Complete obliteration of the aneurysm is not always achieved initially and may require repeat intervention. Higher rate of rebleeding than clipping.
c. Some aneurysms are not amenable to coiling due to distal location or shape (wide neck). Having said that, new technologies such as stent-assisted coiling and flow-diversion devices have allowed treatment of wide-necked and complex or large/giant aneurysms endovascularly.
3. Clipping or Coiling?
That is the big question. Cases should be individualized based on clinical features, anatomy, and expertise of local surgical and endovascular personnel.
ISAT was a randomized multicenter trial comparing the two methods:5
a. 23.7% of coiled versus 30.6% of clipped patients were dependent or dead at 1 year (absolute risk reduction of a bad outcome: 6.9%).
b. For this trial, the patients were required to be good candidates for both procedures (~60% were treated outside the trial). 88% of patients had mild SAH (WFNS grade 1 or 2 – see Appendix 7). Therefore, the results may not be generalizable to the entire population of SAH patients.
c. Locations: 51% were ACA or anterior communicating artery (AcomA) and 33% were ICA or posterior communicating artery (PcomA) aneurysms. Only 14% were MCA aneurysms and 2.7% were posterior circulation aneurysms.
d. Presumably, most MCA aneurysms were clipped and posterior circulation aneurysms coiled outside of the study.
Based on ISAT, the preferred treatment of many ruptured ACA, ICA, AcomA, or PcomA aneurysms is coiling, but, as already stated, the approach must be individualized based on many factors that are beyond the scope of this text (Figure 13.1). Expert multidisciplinary consultation is needed, which underscores the need for these patients to be managed at specialized referral centers.
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