Subarachnoid Hemorrhage Surgery
- Author: Joseph C Watson, MD; Chief Editor: Brian H Kopell, MD more...
Surgery for subarachnoid hemorrhage (SAH) is used to prevent the extravasation of blood into the subarachnoid space between the pial and arachnoid membranes, which has a detrimental effect on both local and global brain function and leads to high morbidity and mortality rates. Excluding trauma, the most common cause of SAH is an intracranial aneurysm; therefore, the surgeries discussed will focus primarily on treating aneurysms. An estimated 15-30% of patients with aneurysmal SAH die before reaching the hospital, and approximately 25% of patients die within 24 hours, with or without medical attention. The mortality rate at the end of 1 week approaches 40%. Half of all patients die in the first 6 months, and only half of the patients who make it to the hospital return to their previous level of functioning.
Subarachnoid hemorrhage comprises half of spontaneous atraumatic intracranial hemorrhages (usually as the result of aneurysmal or arteriovenous malformation [AVM] leakage or rupture), with the other half consisting of bleeding that occurs within the brain parenchyma.
Ancient Greek, Egyptian, and Arabic literature all have references to intracranial aneurysms, but the first successful treatment was reported in the early 19th century. However, such positive outcomes did not become routine until the advent of modern neurosurgical techniques.
Walter Dandy performed the first successful clipping of an aneurysm in 1937, using a vascular clip designed by Harvey Cushing. In the following years, advancements in microneurosurgical techniques, including the operating microscope, microsurgical instruments, better anesthesia, and improved management of subarachnoid hemorrhage complications, led to significant improvements in surgical outcomes.
Endovascular therapy for the treatment of intracranial aneurysms was pioneered in the mid-1970s by Serbinenko at the Moscow Institute of Neurosurgery. This initial approach, which attempted to achieve parent vessel occlusion using latex balloons, was moderately successful in a limited subset of cases. However, it never gained widespread applicability.
Other balloon devices, including detachable silicon and latex balloons, were subsequently developed in the United States, Europe, and Japan. The success of balloon embolization has been tempered by the associated complications of deflation and aneurysmal rupture.
Arguably, the most significant recent development in endovascular therapy occurred in 1990, when Guglielmi and colleagues at the University of California Los Angeles Medical Center developed the Guglielmi detachable coil (GDC) system.
The GDC is a radiopaque platinum coil that is delivered through a microcatheter into an aneurysm, which then is detached by electrolysis. In 1995, GDCs gained approval by the US Food and Drug Administration for treatment of aneurysms that have the potential for high surgical morbidity and mortality.
In Europe, GDCs have been used as a first-line intervention in lieu of surgical treatment for patients without contraindications to endovascular therapy. In the last decade, endovascular coiling has become first-line treatment for aneurysms at most centers in the United States.
Other endovascular techniques
Other endovascular techniques include stenting and liquid embolic agents. As endovascular occlusive techniques evolve, it seems likely that they will play a larger role in the management of SAH.
Rupture of "berry," or saccular, aneurysms of branch points of the basal vessels of the brain comprises over three quarters of nontraumatic subarachnoid hemorrhage cases.
Circle of Willis
Most aneurysms occur at bifurcations of the intracranial arteries, and the location with the most branch points is the circle of Willis. The circle of Willis is in close proximity to the ventral surface of the brain in the suprasellar cistern and is adjacent to the optic nerves and tracts. It extends from the superior border of the pons to the longitudinal fissure between the cerebral hemispheres.
The circle of Willis is an anastomotic circle of the important arteries that supply the brain from the heart: the 2 vertebral and the 2 internal carotid arteries in the neck. It can be divided into anterior and posterior sections.
Anterior portion of the circle of Willis
The anterior portion of the circle of Willis consists of the internal carotid arteries, the posterior communicating artery, the proximal middle cerebral artery, the anterior cerebral artery, and the anterior communicating artery, as follows:
The right common carotid artery originates from the brachiocephalic trunk, the first branch of the aorta, and gives rise to the right internal carotid artery.
The left common carotid artery, the second branch of the aorta, branches into the left internal carotid artery.
The cerebral portion of the internal carotid artery gives off its first anastomotic branch, the posterior communicating artery, shortly after it enters the head. It then divides into the anterior and middle cerebral arteries at the medial end of the lateral sulcus.
The anterior communicating artery is a short segment that connects the 2 anterior cerebral arteries and forms the anterior border of the circle of Willis.
Posterior portion of the circle of Willis
The posterior segment of the circle of Willis consists of the basilar apex and the proximal portions of the posterior cerebral arteries and the paired posterior communicating arteries, as follows:
The basilar artery is formed by the union of the 2 vertebral arteries, each of which begins as a branch of the first part of the subclavian artery and runs through bony foramina in the cervical spine.
The 2 posterior cerebral arteries arise from the terminal bifurcation of the basilar artery.
The posterior communicating arteries connect the internal carotid and the posterior cerebral arteries and form the posterior-lateral borders of the circle of Willis.
Location of aneurysm rupture
Approximately 85% of saccular aneurysms occur in the anterior circulation. The most common sites of rupture are as follows:
The internal carotid artery, including the posterior communicating junction (30-40%)
The anterior communicating artery/anterior cerebral artery (30-40%)
The middle cerebral artery (20%)
The vertebral-basilar arteries (4-10%)
Other arteries, such as pericallosal and anterior choroidal (1-5%)
Clinical Grading Systems
Clinical assessment of subarachnoid hemorrhage (SAH) severity commonly utilizes grading scales. The 2 clinical scales most often employed are the Hunt and Hess and the World Federation of Neurological Surgeons (WFNS) grading systems. A third, the Fischer scale, classifies subarachnoid hemorrhage (SAH) based on computed tomography (CT) scan appearance and quantification intracranial blood.
The Hunt and Hess and the WFNS grading systems have been shown to correlate well with patient outcome. The Fischer classification has been used successfully to predict the likelihood of symptomatic cerebral vasospasm, one of the most important complications of aneurysmal SAH.
All 3 grading systems are useful in determining the indications for and timing of surgical management. For an accurate assessment of subarachnoid hemorrhage (SAH) severity, these grading systems must be used in concert with the patient's overall general medical condition and the location and size of the ruptured aneurysm.
The Hunt and Hess grading system is as follows :
Grade 1 – Asymptomatic or mild headache
Grade 2 – Moderate to severe headache, nuchal rigidity, and no neurologic deficit other than possible cranial nerve palsy
Grade 3 – Mild alteration in mental status (confusion, lethargy), mild focal neurologic deficit
Grade 4 – Stupor and/or hemiparesis
Grade 5 – Comatose and/or decerebrate rigidity
The WFNS scale is as follows:
Grade 1 – Glasgow Coma Score (GCS) of 15, motor deficit absent
Grade 2 – GCS of 13-14, motor deficit absent
Grade 3 – GCS of 13-14, motor deficit present
Grade 4 – GCS of 7-12, motor deficit absent or present
Grade 5 – GCS of 3-6, motor deficit absent or present
The Fischer scale (CT scan appearance) is as follows:
Group 1 – No blood detected
Group 2 – Diffuse deposition of subarachnoid blood, no clots, and no layers of blood greater than 1 mm
Group 3 – Localized clots and/or vertical layers of blood 1 mm or greater in thickness
Group 4 – Diffuse or no subarachnoid blood, but intracerebral or intraventricular clots are present
Surgical methods for treatment of subarachnoid hemorrhage have improved dramatically with the advent of modern microsurgical techniques and even more dramatically with the success of endovascular therapy.
Current surgical options include direct aneurysmal clipping and endovascular exclusion. (See Surgical Clipping or Coil Embolization for the specific indications for treating an aneurysm surgically, endovascularly, or both).
Direct aneurysmal clipping
Direct aneurysmal clipping is no longer considered first-line treatment of aneurysmal subarachnoid hemorrhage in the United States, since most aneurysms are treatable by endovascular means. The principal of “open” aneurysm surgery is to clip the aneurysmal neck to occlude it without compromising flow to the parent artery. Clips are available in various sizes and shapes and are MRI compatible. Giant aneurysms or aneurysms with a calcified neck may require specialized clips with added strength (tandem or booster clips).
Of the various endovascular options currently available, Guglielmi detachable coils (GDCs) have had the largest influence with respect to treatment of subarachnoid hemorrhage; GDCs are first-line therapy in Europe.
These coils are soft, flexible, and can be contoured to the configuration of the aneurysm. Sizes range from 2 to 20 mm in diameter and 2 to 30 cm in length. In limited clinical trials, GDCs have been reported to achieve excellent rates of aneurysmal occlusion combined with a low complication rate in appropriate patients. Two experimental coils, the bidimensional GDC and the 3-dimensional (3-D) GDC may have even better potential for aneurysm occlusion than the current generation of GDCs, but further study is needed.
Balloon embolization is efficacious in selected patients, but it has a higher incidence of complications than coil embolization.
Other surgical options
Proximal ligation of the parent artery or trapping of aneurysms with or without bypass: Proximal ligation is effective for giant aneurysms. Trial balloon occlusion can be used to assess which cases necessitate a bypass graft during the trapping procedure.
Wrapping or coating of aneurysms may be the only option in rare cases of dissecting or fusiform aneurysms.
Indications for Surgical Clipping or Coil Embolization
Emergent neurosurgical consultation should be obtained in all cases of suspected aneurysmal subarachnoid hemorrhage.
The indications for surgery in patients with subarachnoid hemorrhage can be stratified based on clinical grade (see Clinical Grading Systems). Other factors, such as overall medical condition of the patient, aneurysm size and location, accessibility of the aneurysm for surgical repair, patient preference of open surgery versus coiling, and the presence or absence of thrombus or aneurysm wall calcification, are also important.
Clinical grade and surgical intervention
For patients with a mild- or intermediate-grade subarachnoid hemorrhage(Hunt and Hess/World Federation of Neurological Surgeons [WFNS] grades 1-3), early treatment is strongly recommended, because the risks of complications from this condition greatly exceed the risk of complications of intervention. Most aneurysms will be amenable to coiling or clipping. Based on the European experience,[4, 5] the complication rate will be lower in these patients with endovascular treatment. Frankly, most patients will choose an endovascular approach over a craniotomy when given the option.
For patients with a poor grade of subarachnoid hemorrhage (Hunt and Hess/WFNS grades 4-5), the decision whether to operate is controversial and largely depends on the institution. The threshold for endovascular treatment is still low, as the procedure tends to be less risky for a “sick” patient. The overall outcome is poor, with or without surgical intervention.
Patients with a higher grade of subarachnoid hemorrhage or poor medical status that does not qualify for early surgery or endovascular treatment may be candidates for delayed surgery or endovascular obliteration of the aneurysm.
Other indications for surgical intervention
The indications that favor open surgical management primarily have to do with factors associated with mass effect or elevated intracranial pressure from a focal source. Only surgery will allow for reduction in mass effect. Specific factors are as follows:
Mass effect or hematoma associated with the aneurysm. Large hematomas, especially those in the temporal lobe, need to be evacuated to prevent or treat uncal herniation. If the risk of an open craniotomy is already accepted for the decompression, aneurysm clipping at the same time is indicated. However, endovascular options may still be entertained perioperatively if clipping is not manageable.
Large and giant aneurysm. Some aneurysms cause symptoms related to their size and the pressure exerted on adjacent structures. Surgical clipping will typically deflate the aneurysm and relieve this pressure. Common sites where this is found include the periophthalmic aneurysms that may compress the optic nerves and the posterior communicating aneurysms that may exert pressure on the third nerve.
Wide-necked aneurysms. A large neck-to-dome ratio makes acute endovascular coiling of wide-necked aneurysms more difficult. Because this same anatomy complicates clipping as well, open surgery is often a better choice.
Vessels emanating from the aneurysm dome. Such aneurysms cannot be excluded without occluding distal vessels from its dome. Open surgery may provide the option of bypass or vessel reconstruction with clips.
Recurrent aneurysm after coil embolization. Although partial recanalization of a coiled aneurysm is fairly common (10% or so) and this recurrence is typically handled with a recoiling, open options may exist for these cases.
Indications for endovascular treatment
Endovascular therapy (eg, coil embolization) has expanded dramatically in the past 10 years, with excellent results. Credible data exist that compare the traditional treatment modality (aneurysmal clipping) with newer endovascular techniques, and these data favor endovascular therapy. Before this study and others that have followed supporting it, coiling was the primary treatment for nearly all posterior circulation aneurysms.
In general, endovascular treatment of aneurysms is favored over open surgery in the following situations:
Posterior circulation aneurysms, especially basilar apex. This is due to the high surgical morbidity encountered with open clipping from harm to brainstem perforators.
Patients with poor clinical grade (ie, Hunt and Hess/WFNS grades 4-5).
Patients who are medically unstable.
Symptomatic cavernous aneurysms.
Small-neck aneurysms in the posterior fossa.
Patients with vasospasm.
Cases in which the aneurysm lacks a defined surgical neck (although these are also difficult to "coil")
Patients with multiple aneurysms in different arterial territories if the surgical risk is high
Surgery remains the standard reference for therapy and is favored over endovascular treatment when surgical risk is low or equal to that of endovascular therapy (see above). However, many patients may be treated adequately with either method, and the ultimate choice of intervention often is guided by the patient (or family) and by physician and institution preference.
A combined approach may benefit a particular subset of patients, for example, those with a poor clinical grade and an aneurysm that cannot be occluded completely by endovascular therapy.
Surgical Indications for Unruptured Aneurysms
The surgical indications for unruptured, symptomatic aneurysms as well as asymptomatic aneurysms are briefly discussed below.
Unruptured, symptomatic aneurysms
Aneurysms may be identified before rupture by virtue of their mass effect or by sudden growth that can cause headaches or occult leakage of blood. Treatment is indicated in patients with symptomatic unruptured aneurysms, because the rate of subsequent rupture is high. Most symptomatic aneurysms tend to be large or even giant. Patients with giant aneurysms face an increased treatment risk; however, this risk usually is less than the morbidity and mortality associated with aneurysm rupture.
Recommendations for the treatment of incidentally discovered aneurysms was plagued for decades by lack of prospective data on the natural history of the aneurysms. Such data now exist and influence greatly how we recommend treatment. The risk of aneurysmal rupture is greatly dependent on its size and location.
Specifically from the prospective Lancet data, the cumulative 5-year rupture rates for patients (without a history of subarachnoid hemorrhage) with aneurysms located in the internal carotid artery, anterior communicating artery or anterior cerebral artery, and middle cerebral artery were 0%, 2.6%, 14.5%, and 40% for aneurysms less than 7 mm, 7-12 mm, 13-24 mm, and 25 mm or greater, respectively. For the same categories involving the posterior circulation and posterior communicating arteries, the rates were 2.5%, 14.5%, 18.4%, and 50%, respectively.
Most physicians, therefore, will recommend treatment of larger or enlarging asymptomatic aneurysms on the basis of the risk-to-benefit ratio provided by these data. For example, a young healthy person with a 7-mm posterior communicating aneurysm (14.5% 5-year rupture rate) should be treated, while an elderly person with a 3-mm middle cerebral artery aneurysm would be managed conservatively.
Timing of Surgical Intervention
The timing of surgery for subarachnoid hemorrhage has been a topic of debate for over 3 decades. In the late 1980's, a very large study helped demonstrate that outcomes were equivalent for early versus late surgery. These points will be iterated below. Such a study has not been updated in our current era of vastly improved endovascular options.
Early surgery (0-3 days) has the following advantages:
Prevention of rebleeding, which is associated with a high mortality rate.
Facilitate treatment of ischemic complications (vasospasm). Permissive hypertension or even induced hypertension is a pillar of treatment for vasospasm and is relatively contraindicated if the aneurysm is not secured.
Decreased duration of hospitalization (from incorporating surgical recovery in the medical management period).
Possible prophylaxis against vasospasm by removal of subarachnoid clot (not really possible).
The following are among the disadvantages of early surgery for subarachnoid hemorrhage:
Technical problems associated with edematous brain tissue.
High risk of intraoperative rupture of fragile aneurysm.
Higher surgical morbidity and mortality rates.
Higher rates of perforator infarct due to mechanical manipulation and vasospasm.
Delayed surgery for subarachnoid hemorrhage (>10 days posthemorrhage) has the following advantages:
Less edematous brain tissue
Lower risk of intraoperative aneurysm rupture
Lower surgical morbidity and mortality rates
Flexibility of scheduling
Lower chance of vasospasm complications.
The disadvantages of delayed surgery are as follows:
Increased rate of morbidity and mortality due to rebleeding.
Fear of inducing rerupture during treatment of vasospasm.
Technical difficulties due to adhesions around the aneurysm.
Published findings on early vs delayed surgery and SAH clinical grade
Findings from the International Cooperative Study on Timing of Aneurysm Surgery include the following[7, 8] :
Surgical outcomes are usually superior with delayed surgery; however, the increased morbidity and mortality rate associated with delay (as high as 30% in some studies for patients with low-grade subarachnoid hemorrhage) negated these results
Overall results were comparable for early and delayed surgery with the exception that patients with low-grade subarachnoid hemorrhage (Hunt and Hess/World Federation of Neurological Surgeons [WFNS] grades 1-2) had a better outcome with early surgery
Subsequently, many centers have published favorable results with early surgery for low-grade subarachnoid hemorrhage, and it now is a common treatment decision
For patients with an intermediate-grade of subarachnoid hemorrhage (Hunt and Hess/WFNS grade 3), the published results are less conclusive, as follows:
Several studies showed no difference in morbidity and mortality rates between early and delayed surgery
A study in Japan suggested that early surgery is beneficial in this group of patients
Greater microsurgical experience and advances in neuroanesthesia and neurointensive management are likely to improve the outcomes for early surgery in this group of patients
The timing of surgical management for patients with high-grade subarachnoid hemorrhage (Hunt and Hess/WFNS grades 4-5) must be individualized depending on the following criteria:
Admission clinical examination findings and Glasgow Coma Score
Computed tomography scan evidence of brain destruction
Intracranial pressure (ICP) measurement
Concurrent medical problems
Presence of absence of cerebral vasospasm
Data suggest that some patients with an initial GCS less than 5 can have good outcomes if the following occur:
A ventricular drain is placed emergently
ICP does not exceed 30 mm Hg
Angiography shows normal intracranial filling
Patients with significant evidence of brain destruction, increased ICP, and an angiogram revealing poor intracranial filling have a universally poor outcome regardless of treatment.
The overall outcome in patients with high-grade subarachnoid hemorrhage is poor with or without surgical intervention; however; because surgical treatment seems to benefit some patients, many authors suggest an aggressive approach to management.
The presurgical examination in a patient with subarachnoid hemorrhage (SAH) should consist of a general assessment, a neurologic assessment, and a radiologic assessment.
Cardiac and pulmonary function can decline with subarachnoid hemorrhage; therefore, all patients should undergo electrocardiographic (ECG) and arterial blood gas (ABG) monitoring. Hemodynamic status should be monitored in patients who show evidence of compromise.
A funduscopic examination should be performed. As many as 10% of patients with subarachnoid hemorrhage have vitreous or retinal hemorrhage (Terson syndrome), which can lead to loss of vision.
Serial neurologic examinations should be performed until the time of surgery for early detection of complications. Minor changes in mood, mentation, or focal neurologic function can be an early indicator of an impending complication, such as progressive hydrocephalus and/or arterial vasospasm.
Computed tomography scanning, CT angiography, magnetic resonance imaging (MRI), and cerebral angiography ultrasonography are briefly discussed below. It is important to note that performing formal angiography may result in a life-threatening delay in treatment, therefore, evaluate the patient's overall medical condition and neurologic status when considering this procedure.
CT scanning is the preferred imaging modality for the initial diagnosis of subarachnoid hemorrhage because it is very sensitive for detecting SAH, intracerebral hemorrhage (ICH), subdural hematomas (SDH), and hydrocephalus and requires very little time. It is not sensitive for detecting ischemia. Furthermore, when SAH is detected, a CT arteriogram (CTA) may be performed by giving IV contrast. This is particularly important in the unstable patient or in the patient with a large life-threatening intracerebral or subdural hematoma who must undergo surgery immediately but there is insufficient time for formal arteriography. CT may detect calcification of the aneurysmal dome and neck, as well as the presence of thrombus. This information can have important surgical implications.
Formal cerebral angiography is the gold standard for defining the presence of intracerebral aneurysms and their anatomy. It can provide important information about the size, shape, and configuration of the aneurysmal dome and neck, as well as the relationship of the parent vessel and perforators. Furthermore, it provides information regarding dynamic blood flow that cannot be obtained from CT angiography or MR angiography. Multiple views, including 3D, should be obtained to best delineate the anatomy of the aneurysmal neck.
During diagnostic angiography, a trial balloon occlusion of the parent artery can be performed and may help to guide preoperative surgical planning. This can be important in giant and fusiform aneurysms that may need to be "trapped," because they lack a defined neck for surgical clipping. A trial balloon occlusion also may provide important information about collateral blood flow.
If cerebral angiography findings are negative (10-20%), a repeat test should be performed 10 days to 2 weeks later. Patients with subarachnoid hemorrhage and a negative cerebral angiography may have an improved prognosis. A false-negative study finding can result from aneurysm obliteration secondary to clotting or focal vasospasm. Hemorrhage secondary to a ruptured arteriovenous malformation (AVM) or spinal cord aneurysm may be present despite a negative finding on cerebral angiogram. Perimesencephalic subarachnoid hemorrhage is a subset of angio-negative SAH. Such patients do not need repeat formal cerebral arteriography as a rule.
Follow-up angiogram is also useful postsurgically to detect the presence of aneurysmal obliteration and to evaluate for possible cerebral vasospasm.
In summary, cerebral angiography can provide the following important surgical information in the setting of subarachnoid hemorrhage:
Cerebrovascular anatomy and dynamic blood flow.
Aneurysm location and source of bleeding.
Aneurysm size and shape, as well as orientation of the aneurysm dome and neck.
Relation of the aneurysm to the parent artery and perforating arteries.
Presence of multiple or mirror aneurysms (identically placed aneurysms in both the left and right circulations).
Transcranial Doppler ultrasonographic studies are a noninvasive method of detecting and following the course of arterial vasospasm. Typically, they may be performed at the bedside with instant results.
MRI scanning is the best radiographic method for evaluating cerebral ischemia. The incidence of cerebral ischemia after aneurysms is very high and correlates with the Hunt and Hess grade. Ischemic damage may be seen on MRI that is clinically undetected. Even after intervention with coiling or clipping, new ischemic damage is common: 10-60% in the open surgical setting[10, 11, 12] ; and with endovascular treatment, a prospective MRI study found ischemic lesions in 37 of 40 patients.
MR angiography is also very sensitive at evaluating aneurysms, but its value is decreased after surgical clip placement. Modern aneurysm clips are all MRI compatible, but the clips do create a focal artifact. MR angiography may also be used for the initial diagnosis of an aneurysm in a patient with SAH and an IV contrast dye allergy. MR angiography also has value in the diagnosis of vasospasm. MRI is used for angio-negative SAH when the suspicion is high for an aneurysm, as a thrombosed or partially thrombosed aneurysm may be seen.
An MRI can help delineate the degree of intramural thrombus in these occult aneurysms or in giant aneurysms.
Intraoperative details of surgical clipping for aneurysmal subarachnoid hemorrhage (SAH) are briefly reviewed below.
Most anterior circulation aneurysms can be approached from the pterion. Exceptions include: (1) aneurysms arising from the division of the anterior cerebral artery into the pericallosal and callosal marginal branches and (2) small, distal mycotic aneurysms.
Posterior circulation aneurysms are less accessible, and a number of approaches are used. The most basic is the retromastoid, retrosigmoid craniectomy. This provides access to the entire ipsilateral vertebral and the midline basilar artery as long as there is minimal brain swelling. It is technically easier in older patients because of some brain atrophy.
The modified pterional approach can be employed for aneurysms arising from the basilar apex where the neck is above the dorsum sellae.
The subtemporal approach is used for aneurysms that initiate at the head of the basilar artery in which the bifurcation of the basilar artery is below the dorsum sellae. A posterior subtemporal approach can be used for most aneurysms arising from the trunk of the basilar artery.
A far lateral inferior approach can be used for certain lower basilar trunk and midline vertebral artery aneurysms. A midline suboccipital approach can be utilized for aneurysms extending from the vertebral artery where it pierces the dura. The midline suboccipital approach may also be used for aneurysms that arise from the distal posterior inferior communicating artery.
The first principle of vascular surgery is proximal control. This is also true for cerebrovascular surgery. Presurgical planning involves an understanding of the intracranial access to the proximal feeding vessels. In cases of proximal ICA aneurysms, such as periophthalmic aneurysms or proximal posterior communicating aneurysms, careful consideration must be made about control of the internal carotid artery in the neck, either with a surgical cutdown or with an intravascular balloon.
Skillful brain retraction is paramount in aneurysm surgery, with care taken to minimize tissue and vessel damage. This typically requires draining the CSF in the basilar cisterns or with a ventricular catheter if there is hydrocephalus. For the rare pericallosal aneurysm approached with an interhemispheric approach, access to the basal cisterns is not available, in which case a ventriculostomy or even a lumbar drain may be used for CSF drainage.
Use of one blade only of a self-retaining retractor (eg, Yasargil, Greenburg, Sugita, Budde) is usually sufficient for adequate exposure of most saccular aneurysms and allows for the compensatory expansion and displacement of nonretracted areas of the brain, thus minimizing tissue trauma. Care must be taken not to rupture the aneurysms while retracting the brain. Therefore, for a posterior communicating aneurysm, the frontal lobe is retracted first over the opticofrontal cistern (away from the aneurysm), and for an anterior communicating aneurysm, the retraction would be more posterior at the frontotemporal junction over the opticocarotid cistern. Temporal tip and sylvian bridging vein may be taken without harm.
Dissection is undertaken to identify the parent arteries for possible temporary clipping in the event of aneurysmal rupture or during difficult dissection. The basilar cisterns are opened by incision of the arachnoid, typically with careful sharp dissection. The sylvian fissure is split to provide access as needed to the proximal arteries.
Dissection of the aneurysm itself is the most technically demanding portion of the operation, since the aneurysm is prone to rupture. Most surgeons prefer to expose the neck only and place the clip before dissecting the dome. Care must be taken to identify perforating arteries and dissect them away from the clip placement if possible.
Mobilization of the aneurysm in all directions is necessary for visualization of any perforating vessels that might inadvertently be incorporated by clip misplacement. However, this may not be possible for large aneurysms or without risking rupture by mobilizing the dome.
Occlusion of the aneurysm is accomplished with an appropriately sized clip placed across the neck. Use of a clip that is as small as possible helps facilitate the visualization of perforating vessels during clip placement. Care must be taken not to occlude the parent vessels by the clip. Confirming patency post-clip placement is performed by micro-Doppler and or indocyanine green (ICG) angiography. Formal intraoperative angiography (DSA) is the gold standard but is more invasive, expensive, and risky. With high-risk aneurysms, such as complicated middle cerebral artery aneurysms, intraoperative angiography with ICG or DSA is crucial, because there is up to 20% clip readjustment.
Large intracerebral hematomas should be removed at the time of craniotomy to lessen the complications associated with increased ICP. With large temporal lobe hematomas and likely MCA stroke syndrome, a decompressive craniectomy may also be used.
Endovascular treatment of aneurysms requires skillful embolization of the aneurysm while maintaining the patency of the parent vessels. Coil embolization is the mainstay of the treatment strategy, but success requires the use of stents, balloons, and sometimes glue. Successful treatment also requires early recognition and treatment of complications, including rupture and arterial embolization.
General anesthesia is required to ensure adequate airway protection, oxygenation, sedation, blood pressure management, and intracranial pressure management.
After the femoral artery puncture and initial angiogram, anticoagulation is initiated with heparin. The risk of thromboembolic events during the procedure in patients with acute subarachnoid hemorrhage eclipses the risk of hemorrhage.
A guide catheter (6F) is placed in the internal carotid or vertebral artery. This allows for the passage of the microcatheter and facilitates contrast injection for angiograms and road mapping. Road mapping is a computer-generated technique that allows for real-time visualization of endovascular equipment superimposed over a map of the intracranial arteries.
The size of the aneurysm must be approximated before embolization by estimation based on the size of the adjacent intracranial arteries, by using objects such as coins for reference, or by use of a guiding catheter with a known size.
The clinician should find the projection that allows for optimal visualization of the parent artery in relation to the aneurysm; this usually requires views in multiple planes.
The plastic microcatheter tip and the Micro-Guide wire are shaped according to the configuration of the aneurysm.
Catheterization and coil placement
The aneurysm is catheterized with the microcatheter and guide wire using road mapping. The microcatheter should not touch the walls of the aneurysm.
When the microcatheter is in the desired position within the aneurysm, the first GDC can be delivered. The first coil should be slightly smaller than the diameter of the aneurysm, and it should cross the neck of the aneurysm several times to form a receptacle.
After placement of the first coil, the aneurysm is filled with coils of decreasing size until densely packed. Complete packing of the aneurysmal sac and neck usually is possible with small aneurysms. In some larger aneurysms, the neck cannot be occluded completely. These aneurysms have a higher risk of recurrence. Often, aneurysms with larger necks can be treated successfully with a balloon or stent-assisted techniques. There is some reluctance to use stents in the setting of acute SAH, because patients are required to be on antiplatelet agents.
The microcatheter is withdrawn cautiously from the aneurysm, and a final angiogram is obtained.
Heparinization is reversed with protamine, the femoral sheath is removed, and the patient is transferred to the neurologic intensive care unit.
Postoperative Monitoring and Complications
The postoperative management of subarachnoid hemorrhage is directed at prophylaxis and treatment of the complications, including the following:
Vasospasm (see below)
Seizures: Some patients may require steroid and/or anticonvulsant therapy as outpatients; oral nimodipine therapy is often continued for 3 weeks after subarachnoid hemorrhage
Patients with neurologic deficits may require outpatient rehabilitation. Cognitive and psychologic rehabilitation is often needed.
Cerebral vasospasm is the delayed narrowing of the large capacitance vessels at the base of the brain, is a leading cause of morbidity and mortality in survivors of nontraumatic subarachnoid hemorrhage. Vasospasm is reported to occur in as many as 70% of patients with subarachnoid hemorrhage and is clinically symptomatic in as many as 30% of patients. Most commonly, this occurs 4-14 days after the hemorrhage. Vasospasm can lead to impaired cerebral autoregulation and may progress to cerebral ischemia and infarction. Most often, the terminal internal carotid artery or the proximal portions of the anterior and middle cerebral arteries are involved. The arterial territory involved is not related to the location of the ruptured aneurysm.
If vasospasm becomes symptomatic, most authors advocate the use of hypertensive, hypervolemic, and hemodilutional (HHH) therapy. Although the efficacy of HHH therapy still is subject to debate, a number of studies have demonstrated improved cerebral blood flow and resolution of the ischemic effects of vasospasm.
Initiation of HHH therapy requires placement of a central venous catheter in order to guide volume expansion and to safely administer inotropic or vasopressor therapy. This therapy should be reserved for patients with aneurysms secured by surgical clipping or endovascular techniques in order to reduce the risk of rebleeding.
Transluminal balloon angioplasty is recommended for treatment of vasospasm after failure of conventional therapy. One study reported improved neurologic outcome in 70% of patients with symptomatic vasospasm after transluminal angioplasty. Case series reports have indicated that angioplasty appears to be effective in treating vasospasm of large proximal vessels. It is not effective in direct treatment of vasospasm of more distal vessels; however, distal blood flow may be increased as a result of increased proximal vessel diameter. The potential complications of angioplasty itself include vessel rupture, dissection, or occlusion, as well as intracerebral hemorrhage.
Nonspecific postcraniotomy problems include the following:
Jaw pain and stiffness due to temporalis muscle dissection
Atrophy or wasting of the temporalis muscle
Paralysis of the frontalis muscle if an ostoplastic craniotomy is used
Deranged or absent sense of smell due to intraoperative traction on the olfactory tract
Complications of surgical clipping include the following:
Ischemic complications (stroke)
Damage to parent artery or perforating arteries
Acute or delayed neurologic deficits from iatrogenic trauma
Nonspecific postsurgical syndrome similar to postconcussive syndrome (eg, headache, dizziness, blurred vision, poor concentration, poor short-term memory, emotional lability, insomnia, fatigue)
Common complications of endovascular therapy include the following:
Thromboembolism with acute or delayed neurologic deficit (stroke)
Coil displacement or compaction
Nonspecific access complications such as groin hematoma or arterial dissection
Outcome and Prognosis
Mortality and morbidity are influenced by the magnitude of the bleed, the age of the patient, the presence or absence of comorbid conditions, and the occurrence of medical complications.
Despite advances in medical and surgical therapy, the mortality rate for aneurysmal subarachnoid hemorrhage remains 50% at 1 year.
Survival is inversely proportional to subarachnoid hemorrhage grade upon presentation (see Clinical Grading Systems). Reported data demonstrate an approximate 70% survival rate for Hunt and Hess grade 1, 60% for grade 2, 50% for grade 3, 20% for grade 4, and 10% for grade 5.
Approximately 25% of survivors have persistent neurologic deficits. Most survivors have either a transient or a permanent cognitive deficit.
Future and Controversies
The future of subarachnoid hemorrhage management most likely will revolve around the continuing development and refinement of minimally invasive endovascular techniques.
Controversy remains regarding the question of which aneurysms are appropriate for surgical or endovascular treatment; rigorous studies coupled with additional clinical experience will help with the formation of guidelines. Some aneurysms may require a combined approach.
Although detachable coil therapy is, to date, the most promising development in the realm of endovascular methodologies for subarachnoid hemorrhage, the future almost certainly will provide materials that are even safer and more efficacious in occluding aneurysms.
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