Medical and Surgical Management of Intracranial Aneurysms

doi:10.4065/70.2.153

Mayo Clinic Proceedings

Volume 70, Issue 2, February 1995, Pages 153-172

https://doi.org/10.4065/70.2.153 Get rights and content

Objective

To examine the medical and surgical aspects of intracranial aneurysms, including the pathogenesis, clinical manifestations, management of subarachnoid hemorrhage (SAH), and indications for surgical intervention.

Design

This review presents the classification of intracranial aneurysms, defines specific aneurysms, and analyzes the Mayo Clinic experience with surgical treatment of cerebral aneurysms.

Material and Methods

Intracranial aneurysms are classified by cause, size, site, and shape. The clinical grading systems for SAH, the most common manifestation, are as follows: modified Botterell, Hunt and Hess, and World Federation of Neurological Surgeons. Surgical options are direct clipping, interventional neuroradiologic treatment, proximal ligation or trapping of aneurysms, and wrapping or coating of aneurysms. Although the timing of surgical intervention after SAH is controversial, it should be based on the clinical grade, site of the aneurysm, and patient's medical condition.

Results

The frequency of intracranialaneurysms is estimated to be 1 to 8% in the general population, and 90% of patients have SAH. After SAH, 8 to 60% of patients die before they get to a hospital. After hospitalization, the mortality rate is 37%, severe disability is 17%, and outcome is favorable in 47%. The current trend for surgical treatment is early after SAH. The Mayo Clinic experience with 1,947 patients who underwent surgical treatment because of aneu-rysmal SAH or for aneurysmal repair between 1969 and 1990 is as follows: 1,445 had an excellent outcome, 231 had a good outcome, 171 had a poor outcome, and 100 died.

Conclusion

Aggressive management can be beneficial for many patients with severe neurologic injury after SAH by preventing rerupture of the aneurysm, attenuating the severity and sequelae of vasospasm, and decreasing the surgical complications.

Section snippets

PATHOGENESIS

Because the incidence of idiopathic intracranial aneurysms is age dependent²² and reports describe de novo development and growth of aneurysms,23, 24, 25, 26, 27 intracranial aneurysms can be considered acquired lesions.12, 15, 28 In support of this acquired theory is the observation that aneurysms typically develop at branching points of major arteries where the hemodynamic stress forces are greatest. Genetic influences probably contribute to the development of intracranial aneurysms, as

CLINICAL MANIFESTATIONS AND PATHOPHYSIOLOGIC FEATURES

Intracranial aneurysms can manifest in various ways. Aneurysms with no symptoms are termed asymptomatic. Of importance, asymptomatic aneurysms should be distinguished from unruptured aneurysms because aneurysms can cause symptoms even though they do not rupture, and these symptoms are important warning signs that can be useful in detecting an aneurysm before a disastrous hemorrhage. The rate of rupture is higher with symptomatic aneurysms than with asymptomatic aneurysms. In a 5-year follow-up

CLASSIFICATION OF INTRACRANIAL ANEURYSMS

Intracranial aneurysms are classified by the following criteria: (1) cause, (2) size, (3) site, and (4) shape. All these factors are important in determining the appropriate treatment.

Causes.—As reviewed in the preceding paragraphs on pathogenesis, aneurysms can be caused by multiple factors and are classified accordingly.

Idiopathic—Idiopathic aneurysms are related in some way to a combination of abnormalities in the arterial wall, perhaps influenced by both genetic factors and hemodynamic

PRESURGICAL EXAMINATION

General Assessment.—Because cardiac and pulmonary function can be altered by SAH,66, 67, 68 all patients should undergo electrocardiography and arterial blood gas monitoring. In many patients, factors such as pulmonary wedge pressure, central venous pressure, and cardiac output through a Swan-Ganz catheter may need to be monitored. The optic fundi should be examined for the existence of subretinal hemorrhage, which occurs in 10% of patients and may necessitate ophthalmologic care to prevent

SURGICAL INDICATIONS

Many factors are important when determining whether an aneurysm should be surgically treated. Currently, the most pertinent issue is whether the aneurysm has ruptured or whether it is asymptomatic. Other important factors are accessibility of the aneurysm for surgical repair, configuration and size of the aneurysmal neck, presence of thrombus, and relationship of the neck of the aneurysm to the parent artery and perforators. The patient's age and general medical condition are also relevant.

TIMING OF SURGICAL TREATMENT OF RUPTURED INTRACRANIAL ANEURYSMS

The timing of surgical intervention after SAH has been debated during the past 3 decades.70, 71, 76, 77 Currently, the decision to operate should be based on the clinical grade of SAH, the site of the aneurysm, and the patient's medical condition. The advantages and disadvantages of early versus delayed surgical treatment are listed in Table 3.

For patients with a better grade (WFNS grades 1 to 2), several early cooperative studies demonstrated a superior outcome for delayed surgical treatment;

SURGICAL OPTIONS

Surgical techniques for repairing intracranial aneurysms have improved tremendously with the introduction of the operating microscope, microsurgical techniques, and, more recently, interventional radiology. The current treatment options are summarized in the following sections.

Direct Clipping.—Currently, direct clipping is the most routine and definitive treatment of an intracranial aneurysm. With this method, the aneurysmal neck is obliterated by applying a clip that has the strength, shape,

SPECIFIC ANEURYSMS

Giant Aneurysms.—Giant aneurysms occur in about 5% of patients. At our institution, the frequency is approximately 20% because of referral patterns. These aneurysms often manifest with mass effect, although SAH occurs in 35%.¹¹⁷ Giant aneurysms are difficult to treat not only because of their size but also because of their varying pathogenesis. Some giant aneurysms are comparable to fusiform atherosclerotic aneurysms, which occur in the aorta or extracranial carotid artery and have a thick

PERIOPERATIVE MANAGEMENT OF PATIENTS WITH CEREBRAL ANEURYSMS WHO HAVE SAH

Prevention of Rerupture.—After initial medical and neurologic stabilization of the patient, the first issue during the early phase of management is prevention of rerupture. As previously discussed, the greatest risk of rerupture is within the first 24 hours after the initial rupture. The patient should be in a quiet room, and the blood pressure should be maintained at no more than 140 mm Hg. Patients with a poor grade have probable increased intracranial pressure. In these patients, the blood

OUTCOMES ASSOCIATED WITH SURGICAL TREATMENT

The Cooperative Study for Aneurysmal Subarachnoid Hemorrhage¹⁸ described 274 patients with a single intracranial aneurysm treated surgically between 1963 and 1970. Overall mortality was 37%. Most patients (74%) had Hunt and Hess grade 1 or 2, and the mortality rate for this group was 35%, whereas for the smaller group of patients who had Hunt and Hess grade 4 or 5 (14%), the mortality rate was 50%. In this study, “early” operation (within 14 days) led to a mortality rate of 46%, but “late”

MAYO CLINIC EXPERIENCE WITH SURGICAL TREATMENT OF CEREBRAL ANEURYSMS

Study Design.—Patients who came to the Mayo Clinic because of aneurysmal SAH or for aneurysmal repair between 1969 and 1990 were involved in the study. This group included community patients and referral patients from outside the immediate area. Patients who died in the emergency department were excluded. On admission, patients were categorized by clinical grade with use of the modified Botterell classification. For patients with ruptured aneurysms, the day of operation was recorded as the

Acknowledgment

The Mayo series of patients reported herein represents the cumulative experience of Drs. Thoralf M. Sundt, Jr., David G. Piepgras, and Fredric B. Meyer. We are indebted to Nicolee C. Fode for accumulation of the data and to Mary M. Soper for preparation of the submitted manuscript.

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Subject ReviewMedical and Surgical Management of Intracranial Aneurysms

Objective

Design

Material and Methods

Results

Conclusion

Section snippets

PATHOGENESIS

CLINICAL MANIFESTATIONS AND PATHOPHYSIOLOGIC FEATURES

CLASSIFICATION OF INTRACRANIAL ANEURYSMS

PRESURGICAL EXAMINATION

SURGICAL INDICATIONS

TIMING OF SURGICAL TREATMENT OF RUPTURED INTRACRANIAL ANEURYSMS

SURGICAL OPTIONS

SPECIFIC ANEURYSMS

PERIOPERATIVE MANAGEMENT OF PATIENTS WITH CEREBRAL ANEURYSMS WHO HAVE SAH

OUTCOMES ASSOCIATED WITH SURGICAL TREATMENT

MAYO CLINIC EXPERIENCE WITH SURGICAL TREATMENT OF CEREBRAL ANEURYSMS

Acknowledgment

Surg Neurol

Surg Neurol

Surg Neurol

Mayo Clin Proc

Aneurysms in antiquity

Arch Chir Neerl

Surgical Techniques for Saccular and Giant Intracranial Aneurysms

Carotid ligation in sacular intracranial aneurysms

Br J Surg

Intracranial aneurysm of the internal carotid artery: cured by operation

Ann Surg

The dissecting microscope for intracranial vascular surgery

J Neurosurg

Angiographic frequency of anterior circulation intracranial aneurysms

J Neurosurg

Saccular intracranial aneurysms: an autopsy study

J Neurosurg

Incidence, aetiology, and prognosis of primary sub-arachnoid haemorrhage: a study based on 589 cases diagnosed in a defined urban population during a defined period

Acta Neurol ScandSuppI

Origin, growth, and rupture of sacular aneurysms: a review

Neurosurgery

The unchanging pattern of subarachnoid hemorrhage in a community

Neurology

The natural history of aneurysms and arteriovenous malformations

J Neurosurg

Natural history of unruplured intracranial aneurysms: a long-term follow-up study

J Neurosurg

Fatal rupture of intracranial aneurysms: survey of 250 medicolcgal cases

Arch Pathol

Incidence and prognosis of subarachnoid hemorrhage in a Japanese rural community

Stroke

Progress in cerebrovascular disease: management of cerebral aneurysms

Stroke

Cognitive impairment and adjustment in patients without neurological deficits after aneurysmal SAH and early operation

J Neurosurg

Psychiatric sequelae of subarachnoid haemorrhage

BMJ

Observation on the pathology of sacular aneurysms

De novo aneurysm formation following carotid ligation: case report and review of the literature

Neurosurgery

Saccular cerebral aneurysms in rats: a newly developed animal model of the disease

Stroke

Experimentally induced cerebral aneurysms in rats

Surg Neurol

De novo aneurysms: special multiple intracranial aneurysms

Neurosurgery

Rupture of previously documented small asymptomatic sacular intracranial aneurysms: report of three cases

J Neurosurg

Aneurysms and anatomical variation of cerebral arteries

Arch Pathol

The familial incidence of intracranial aneurysms

J Neurol Neurosurg Psychiatry

Familial intracranial aneurysms

J Neurosurg

Occult intracranial aneurysms in polycystic kidney disease: when is cerebral arteriography indicated?

N Engl J Med

Collagen deficiency and ruptured cerebral aneurysms: a clinical and biochemical study

J Neurosurg

Some observations on the pathogenesis and natural history of intracranial aneurysms

J Neurol Neurosurg Psychiatry

Moyamoya disease associated with aneurysm

Subject Review
Medical and Surgical Management of Intracranial Aneurysms