Theoretical comparison of surgery and radiosurgery in cerebral arteriovenous malformations

Microsurgery or Radiosurgery for Cerebral Arteriovenous Malformations? A Study of Two Paired Series

OBJECTIVE

To detect parameters that may augment the therapeutic strategy in patients with a cerebral arteriovenous malformation (AVM) that is considered equally suitable for treatment by neurosurgery or radiosurgery, we compared the efficacy and risks of these two methods in a paired series with similar patient and AVM characteristics.

PATIENTS AND METHODS

Two series of patients with AVM were studied, including a series of 39 patients treated using microsurgery (MS) and another series of 39 patients treated via radiosurgery (RS). These series were paired for age and sex, initial symptoms, size, location and Spetzler-Martin grade, and presence of embolization preceding treatment. We compared the posttreatment outcome in the two groups with respect to obliteration rate, neurological status, mortality rate, and recurrent bleeding. Statistical analysis was performed using paired Student's t test.

RESULTS

The Glasgow Outcome Scale values and Modified Rankin Scores measured at discharge and 12 to 24 months were significantly better in the RS series than in the MS series. The obliteration rate tended to be higher in the MS series (91% versus 81%; P = 0.10, not significant), whereas the rate of neurological deficit was higher in the MS series than in the RS series(P < 0.001). The mortality rate was not significantly different in the two series, but the rate of recurrent bleeding was higher in the RS group (10% versus 0%; P = 0.04).

CONCLUSIONS

Although the rate of cure was similar for patients treated with MS and RS, neurological morbidity was higher after MS and recurrent bleeding was more frequent after RS.

Simulation of the natural history of cerebral aneurysms based on data from the International Study of Unruptured Intracranial Aneurysms

Object

Despite recent publications of large-scale study data, controversy over the management of unruptured cerebral aneurysms continues. The low rupture rates in the International Study of Unruptured Intracranial Aneurysms (ISUIA) apparently contradicted surgeons’ experiences with ruptured aneurysms. In the present study, based on data from the ISUIA, a mathematical model describing the natural history of cerebral aneurysms was developed. With this model, the author aimed to examine the validity of data from the ISUIA and to provide a better treatment guideline for unruptured aneurysms.

Methods

The author made a computer simulation of the natural history of cerebral aneurysms that was used to calculate such figures as the prevalence of unruptured aneurysms, incidence of subarachnoid hemorrhage (SAH), and age and size distribution of both unruptured and ruptured aneurysms. The lifetime lesion rupture probability for individual patients with various ages and aneurysm sizes was also computed, thereby providing a useful index to help patients in the medical decision-making process.

The computer model produced a sample of unruptured aneurysms in the general population with a prevalence of 4.2% and a median diameter of 5.8 mm. These unruptured aneurysms—affected by the rupture rate reported in the ISUIA—had a yearly SAH incidence of 19.6 per 100,000 persons. The median diameter of these aneurysms was 9.4 mm.

Conclusions

Findings in the present study validated the results of the ISUIA by showing that the seemingly low rupture rates could explain the statistical data for ruptured aneurysms. With the featured model, the author calculated the lifetime probability of lesion rupture—a useful measure for deciding on the optimal treatment for unruptured aneurysms.

Decompressive Hemicraniectomy for Poor-grade Aneurysmal Subarachnoid Hemorrhage Patients with Associated Intracerebral Hemorrhage: Clinical Outcome and Quality of Life Assessment

OBJECTIVE:

Decompressive hemicraniectomy has been proposed as a potential treatment strategy in patients with poor-grade aneurysmal subarachnoid hemorrhage presenting with focal intracerebral hemorrhage causing significant mass effect. Although hemicraniectomy improves overall survival rates, the long-term quality of life (QoL) for survivors in this patient population has not been reported.

METHODS:

Using adjudicated outcome assessments, we compare long-term clinical outcomes and QoL between a group of patients with poor-grade aneurysmal subarachnoid hemorrhage receiving decompressive hemicraniectomy (n = 12) and a control group of similar patients managed more conservatively (n = 10).

RESULTS:

Patients receiving decompressive hemicraniectomy experienced a statistically insignificant decrease in short-term mortality compared with controls (25 versus 42%); however, long-term QoL in hemicraniectomy survivors was generally poor. Furthermore, hemicraniectomy patients did not experience an increase in mean quality-adjusted life years over control patients (2.31 versus 2.22 yr).

CONCLUSION:

Decompressive hemicraniectomy prolongs short-term survival in patients with poor-grade aneurysmal subarachnoid hemorrhage with associated intracerebral hemorrhage; however, this trend is not statistically significant, and the overall QoL experienced by survivors is poor. Decompressive hemicraniectomy may be indicated if performed early in a select subset of patients. On the basis of our preliminary data, large prospective studies to investigate this issue further may not be warranted.

Surgical decision-making on cerebral cavernous malformations

This study is an attempt to clarify surgical decision-making on cerebral cavernous malformations based on the data available in the literature. Using a mathematical model, we calculated the morbidity-free survival curves of the patients harboring cerebral cavernous malformations. Using these survival curves, we calculated the morbidity-free life expectancies of the patients at certain age undergoing either natural course or surgery. For superficially located lesions, permissible surgical risks were very small ranging from 0.4 to 2.8 percent of combined morbidity and mortality. The surgical gain of morbidity free life expectancy was also very small (0.0-1.1 years) irrespective of patient's age or eloquence of the location. For deep lesions, the permissible risk of surgery was very large, ranging from 64.1% for a 20-year-old and 31.4% for a 60-year-old patient. The gain of morbidity-free life expectancy was also large for younger patients (17-25 years for 20-year-old patients), but this gain rapidly decreased as the patient's age grew older, becoming 1.1 to 3.1 years for 60-year-old patients. Surgery seems to be justified for younger patients with deep lesions. There seems to be little indication for surgery of superficial lesions as far as the risk of bleeding is concerned.

Functional and topographical considerations in the surgical management of cerebral vascular malformations

Cerebral vascular malformations with potential surgical consequences mainly consist of arteriovenous malformations (AVM) and cavernous malformations. The standard preoperative workup of these lesions includes basic neuroradiological investigation, such as computed tomography, magnetic resonance imaging (MRI), and magnetic resonance angiography, and conventional angiography, to assess the exact neurotopographical relationships of the nidus, arterial feeding pedicles, and venous drainage. In cases where lesions are located near or within eloquent areas, precise documentation of the anatomy can be obtained using various functional tests including functional MRI, activated positron emission tomoqraphy, and magnetoencephalography (MEG), which may then be integrated into a neuronavigational system allowing for selective, image-guided surgery, thus potentially reducing surgical morbidity. Preoperative embolization may in certain cases improve the surqical excision by reducinq blood flow throuqh the AVM. Cavernous malformations may also be removed with minimally invasive and highly selective techniques.

Stereotactic radiosurgery of cerebral arteriovenous malformations with a multileaf collimator and a single isocenter

OBJECTIVE

To prospectively demonstrate the safety and efficacy of stereotactic radiosurgery for arteriovenous malformations (AVMs) of the brain with a linear accelerator fitted with a multileaf collimator.

METHODS

A novel radiosurgery system was developed at the University of Michigan Medical Center with a standard multileaf collimator and a computer-controlled radiotherapy system. Data were accumulated prospectively on all patients undergoing treatment with this system since treatment began in 1995.

RESULTS

Thirty-six patients with 37 AVMs have undergone treatment to date. At more than 3 years since treatment, 15 of 16 AVMs with a volume of less than 10 cc were proven to be obliterated by angiography or magnetic resonance imaging, and one was considered a treatment failure. At more than 24 months since therapy, all four AVMs with a volume of 10 to 25 cc were obliterated. Four patients with AVMs with a volume of more than 25 cc have undergone staged therapy, treating the entire volume to 10 Gy twice, but none has been followed long enough to demonstrate a final outcome. There were four transient and no permanent complications.

CONCLUSION

Our early data indicate that stereotactic radiosurgery of cerebral AVMs with a linear accelerator and a multileaf collimator is safe and effective. Large AVMs may be especially suitable for this mode of therapy. Staged treatment of very large AVMs seems to be a promising addition to standard treatment, but longer follow-up is necessary to confirm that complete obliteration can be achieved.

New concepts in adult brain arteriovenous malformations

Brain arteriovenous malformations are currently attracting increasing attention among clinicians as modern brain imaging techniques facilitate both diagnostic and follow-up evaluation. Their frequent presentation in young individuals, at times with flagrant clinical effects caused by cerebral hemorrhages or seizure disorders, keeps clinicians alert to any improvement in treatment strategies. Recent technical advances in surgical, endovascular, and radiation therapy add to the constantly accumulating data on clinical features, natural course, and treatment outcome in adult arteriovenous malformation patients. This review focuses on new concepts in arteriovenous malformation etiology, classification, treatment, and study approaches.