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Thalamic cavernous malformations pose clinical problems similar to cavernous malformations located in other highly eloquent areas such as the brainstem. Better imaging and continuous refinements of frameless stereotaxy have greatly increased our comfort level in resecting lesions in such critical areas. This report details the contralateral interhemispheric approach, which is very useful in approaching symptomatic cavernous malformations of the thalamus that abut the ependymal surface of the lateral or third ventricles.

The indications for treatment of cavernous malformations of the brain stem have evolved greatly in the past decade. As more experience has been gained with these lesions, it has become evident that surgical excision is possible with acceptable rates of surgical morbidity and mortality. Criteria for surgical indications include a symptomatic lesion that reaches a pial or ependymal surface and that can be reached without the need to traverse eloquent brain stem parenchyma. Advances in frameless stereotactic systems have improved localization and made resection safer, even for ''intrinsic'' symptomatic lesions that are reached through a small incision in ''safe entry-zones'' on the surface of the brain stem. Although with caution, surgical excision should also be considered for selected young asymptomatic patients with relatively large lesions that reach a pial or ependymal surface. This article summarizes the clinical characteristics, indications for surgery, technical surgical pitfalls, and outcomes of surgical resection of brain stem cavernous malformations.

Supratentorial cavernomas account for 75% of all cavernous malformations. These lesions become symptomatic as a result of hemorrhage, seizures, or mass effect. Patients with symptomatic supratentorial cavernomas are candidates for surgical resection. In recent years, resecting cavernous malformations has become safer. The procedure is straightforward utilizing neuronavigation and, when necessary, skull base techniques. This article reviews the basic surgical management of supratentorial cavernous malformations, reflecting the treatment strategies used at our institution.

Atypical cavernous malformations are lesions with distinct anatomic features and locales. This subgroup includes purely extraxial lesions as well as those involving the ventricular system and cranial nerves. The epidemiology, symptoms, surgical approach, and therapeutic implications are unique to each atypical lesion. These features are reviewed, and the indications as well as caveats for successful surgical treatment are offered.

Controversies exist regarding the appropriate initial management of patients with cavernous malformations associated with a seizure disorder. We retrospectively reviewed our experience with simple lesionectomy in the treatment of 82 patients with supratentorial cortical cavernous malformations who presented with seizures. Fifty-five patients had adequate follow up (at least 1 year; mean, 52 months) to assess outcome related to seizure control. Forty (73%) patients had single and 15 (27%) had multiple cavernous malformations. Eighteen (33%) patients underwent surgery within the first 2 months of their initial seizure. Thirty-seven (67%) patients had seizures for more than 6 months before their lesionectomy. All patients were treated with lesionectomy alone as their initial management. Outcomes were evaluated based on Engel's criteria. Seizure outcome was based on the number of seizures pre- and postoperatively, lesion location, and number of lesions. Of the 55 patients with adequate follow up, 69% were seizure free (grade 1) and 13% were almost seizure free (grade II). All 18 patients who were operated on within 2 months of their initial seizure have remained seizure free. Of the patients with chronic epilepsy before surgery, 57% are seizure free, and 17% are almost seizure free. Patients with multiple cavernous malformations and well-localized seizure activity on preoperative testing responded well to lesionectomy. Lesion location was not significant in predicting seizure outcome after surgery. Lesionectomy is a valuable treatment for patients with cavernous malformations associated with epilepsy and represents the best initial treatment option. Patients with chronic epilepsy who fail to become seizure free after lesionectomy may require further epilepsy monitoring and resection. Initial lesionectomy, however, will avoid unnecessary epilepsy surgery in most of these patients.

With the widespread availability of magnetic resonance imaging, spinal cord cavernous malformations are diagnosed frequently, even in patients with mild symptoms. Increasing experience with the surgical resection of these lesions has also led to excellent outcomes in most patients. This article details the indications for surgery and the techniques used to resect spinal cord cavernous malformations.

As many as 25% of all cavernous malformations occur in children, and they are distributed in a bimodal fashion with peaks at 3 and 11 years of age. Cavernous malformations in children pose a unique set of challenges. This article therefore reviews the epidemiology, pathology, clinical characteristics, and management of cavernous malformations of the pediatric central nervous system.

Cavernous malformations are compact lesions composed of sinusoidal vascular channels that resemble dilated capillaries. They are found throughout the central nervous system with an estimated incidence in the general population of about 0.4%. Cavernous malformations occur as a sporadic form in which lesions tend to be solitary and as a familial form characterized by multiple lesions and a strong family history of seizures. The familial forms of this disease are inherited in an autosomal dominant mode. Genetic studies have identified three distinct loci associated with the familial forms of this disease-which have been termed cerebral cavernous malformations (CCM): CCM1 located on the long arm of chromosome 7 (7q21 to 7q22), CCM2 on the short arm of chromosome 7 (7p13-p15), and CCM3 on the long arm of chromosome 3 (3q25 to 3q27). In the CCM population, 40% of families link to CCM1, 20% to CCM2, and 40% to CCM3. Further analysis has demonstrated that mutations in the KRIT1 gene are responsible for CCM1. KRIT1 is a binding protein that interacts with Krev-1/rap1a, a member of the Ras family of GTPases with tumor-suppressing activity for the Ras oncogenes. These findings, along with the evidence from magnetic resonance imaging (MRI) studies that the de novo appearance of new lesions is relatively common, suggest that cavernous malformations should be reclassified as benign vascular tumors.

Ischemia of the posterior circulation related to diseases of the vertebral artery is associated with a significant incidence of delayed stroke and morbidity. Although medical therapies, including anticoagulant and antiplatelet agents, typically are used as the first line of treatment, many surgical techniques are available for the management of refractory cases. Atheroclerosis and compression by fascial bands or osteophytes represent the most frequent types of pathology affecting the vertebral artery. Surgical techniques vary according to the location and type of disease process. Vertebral endarterectomy, transpositions, and bypasses are discussed, and surgical approaches are reviewed in the context of the location and type of disease.

The hallmark feature of neurofibromatosis type 2 (NF2) is bilateral vestibular schwannomas. Vestibular schwannomas associated with NF2 have histologic features that make their resection more difficult, especially when preservation of hearing is a surgical goal. The presence of bilateral lesions complicates the treatment decision-making process. Because of their differences, vestibular schwannomas associated with NF2 merit consideration as a separate clinical entity from sporadic vestibular schwannomas. Understanding these differences and how they affect surgical and radiosurgical outcomes is important in understanding the disease process and related clinical management issues.

Surgical treatment of acoustic neuromas necessitates opening a corridor to the cerebellopontine angle and middle ear. Suboccipital and retrosigmoid craniotomies spare the petrous bone, and these approaches afford sufficient access for the safe and adequate resection of many tumors. These approaches may preserve hearing. Because of their size and extension into the middle ear, however, some acoustic neuromas require more extensive surgical exposure. In these cases, a petrosectomy can be performed. To minimize complications related to a complete petrosectomy, other approaches that remove variable amounts of the petrous bone have been developed. In contrast to suboccipital and retrosigmoid craniotomies, these approaches provide surgeons a wider working angle and more direct exposure of portions of tumor extending into the middle ear. Typically, these advantages are gained at the expense of hearing, however. This article reviews the surgical approaches that use a posterior petrosectomy to access acoustic neuromas: the retrolabyrinthine, translabyrinthine, and transcochlear approaches.

The proper management and treatment of giant intracranial aneurysms require meticulous preoperative and intraoperative planning. The dismal natural history of these lesions necessitates intervention; however, anatomic complexity and the technical difficulty associated with treatment make giant intracranial aneurysms one of the more challenging lesions a neurosurgeon can address. The basic tenants of aneurysm surgery apply to these lesions. Vascular control is crucial and may include measures as drastic as hypothermic circulatory arrest. Wide access with minimal retraction is highly desirable, and selection of the appropriate skull base approach is necessary to achieve this goal. Because the risk of aneurysm rupture is only truly eliminated if the lesion is fully excluded from the circulation, all intraoperative techniques must achieve this goal. If direct clipping of the aneurysm and reconstruction of the vessel lumen are impossible, other techniques, including parent-vessel ligation, aneurysm trapping, and bypass procedures, are important adjuvants in the neurosurgeon's arsenal. This article focuses on the skull base approaches and operative techniques that are essential to giant intracranial aneurysm surgery.

Brain stem cavernous malformations have been recognized increasingly as neuroradiographic techniques have improved. Their natural history can pursue a malignant course, but some lesions can remain clinically silent for years. It is difficult to predict the frequency and severity of each hemorrhage, although conservative or surgical management can be recommended in certain situations. Typically, patients with multiple hemorrhages, progressive deficits, severe mass effect, or lesions that clearly reach a pial surface are considered appropriate surgical candidates. Patients with asymptomatic lesions or with a significant rim of normal tissue should be followed conservatively. This article reviews the natural history of these lesions and elucidates successful preoperative, intraoperative, and postoperative strategies for the management of brain stem cavernous malformations.

Surgery on the brain stem has been associated with mixed results; aggressive approaches have not always resulted in the best outcomes. The evolution of skull base surgery and a better understanding of anatomy have allowed neurosurgeons to forge new frontiers in surgery on the brain stem. The advances largely reflect improvements in technology, including improved optical techniques, frameless stereotactic systems, dissecting instruments, and advances in radiographic techniques. Magnetic resonance imaging now permits superb delineation of anatomic structures and has improved the accuracy of preoperative differential diagnoses. A more aggressive surgical approach can be planned for discrete lesions. This article reviews some of the most common skull base approaches used at our institution to access the brain stem. Technical pearls are discussed as well as basic steps to the surgical approaches. The advantages and disadvantages of each approach are also detailed.

The objective of aneurysm surgery is to exclude the aneurysm from the circulation while preserving blood flow distal to the lesion. A subset of complex large, giant, or fusiform intracranial aneurysms, however, may be unamenable to clipping or clip reconstruction of the parent vessel. In such cases, occlusion of the parent vessel, first described by Hunter, is a treatment option. In many patients, however, sacrifice of the parent artery has an associated risk of ischemic stroke. Therefore, sacrifice of the parent vessel can be supplemented with distal revascularization to provide the necessary distal blood flow while allowing the aneurysm to be trapped. The indications, options, and operative techniques for microvascular bypass are described, and the surgical approaches for revascularization of aneurysms of both the anterior and posterior circulation are detailed.

Between 1990 and 1998, 63 patients (39 men and 24 women) underwent a transfacial approach. Based on the level I through level VI classification scheme developed by the Barrow Neurological Institute Skull Base Team, 83 transfacial procedures were performed: 49 procedures involved a single level, 8 involved a level III approach combined with a level V approach, and 3 involved a level I through III aoproach combined with either a pterional craniotomy or orbitozygomatic craniotomy. Eleven procedures were performed in a staged fashion. Thirty-five different pathologies were addressed: Chordomas (7), angiofibromas (7), and pituitary macroadenomas (5) were most common. One patient (1.6%) died postoperatively. Overall, 29 (46%) patients experienced complications after transfacial surgery. Six (9.5%) patients experienced major complications, and 23 (36.5%) patients experienced minor complications. The transfacial surgeries were without complications in 34 (54%) patients. This large series demonstrates the versatility of transfacial skull base approaches for treating benign and malignant lesions. The procedures are associated with good patient outcomes and an acceptable rate of complications.

A variety of transfacial surgical approaches to midline skull base lesions can be organized in a simple classification scheme of six techniques or levels. Three intracranial approaches use a subfrontal trajectory and variable amounts of transfacial exposure through the nasal and orbital bones. Surgical exposure increases with the amount of bone removed with the facial fragment: supraorbial bar (level 1), supraorbitonasal bar (level II), and orbitonasal bar (level III). Three extracranial approaches use a more inferior trajectory and variable amounts of transfacial exposure through the maxilla. The transnasomaxillary approach (level IV) requires a Le Fort II osteotomy with splitting of the maxillary fragment. The transmaxillary approach (level V) requires a Le Fort l osteotomy with splitting of the palate. The transpalatal approach (level VI) requires circumferential osteotomy and removal of the hard palate. These versatile transfacial approaches, used alone or in combination, have a distinct role in the armamentarium of the skull base surgeon who develops individualized treatment strategies for curative resection of midline skull base lesions.

The transcondylar approach is a skull-base technique that enables neurosurgeons to access the anterior brain stem and foramen magnum region with minimum retraction. This extension of the unilateral suboccipital approach optimizes the surgical treatment of lesions in this region, including benign tumors, bony and locally invasive tumors, and vascular lesions. Many variations of the lateral skull-base approach to the anterior craniovertebral junction, which include variable resection of the condyle, have been published. This article summarizes some of these variations and describes the far-lateral transcondylar approach as performed at our institution. It also reviews the indications, advantages, and disadvantages of the approach.

Petrosectomy is the essential component of many of the important skull base approaches. The transpetrosal approaches enable safe surgical treatment of many petroclival lesions. The combination approaches further increase surgical exposure for more complex lesions. Selecting the best surgical approach requires careful evaluation of lesion location, size, pathology, and the patient's preoperative neurological function. Successful management of these difficult lesions requires a multidisciplinary team that is critically dependent on the neuro-otologist.

Various localizing mechanisms for intraoperative navigation with frameless stereotaxy have been developed, including proprioceptive arms, freehand probes with infrared optical tracking systems, and integrated microscope/stereotactic systems that map the microscope's focal point. During a 5-year period, 1,212 procedures were performed on 1,155 patients using five navigational devices, and the accuracy and clinical performance of the systems were compared. Operative pathology included 193 gliomas, 128 convexity meningiomas, 117 skull-base tumors, 113 epilepsy operations, 106 cavernous malformations, 65 arteriovenous malformations, 6 aneurysms, 25 acoustic neuromas, 25 ventriculoperitoneal shunt procedures, 45 metastases, 338 other or unspecified primary brain tumors, and 51 miscellaneous lesions. The proprioceptive arm was used in 1,112 procedures (mean error, 1.86 mm); the freehand probe (1-dimensional cameras) was used in 29 procedures (mean error, 1.72 mm); the freehand probe (2-dimensional cameras) was used in 40 procedures (mean error, 2.64 mm); the MKM microscope system (Carl Zeiss, Thornwood, NY) was used in 16 procedures (mean error, 3.08 mm); and the SMN microscope system (Carl Zeiss) was used in 15 procedures (mean error, 2.30 mm). According to a survey of performance characteristics and surgeons' preferences, the proprioceptive arm system had the best apparatus, computer software, tracking mechanism, and display. It was accurate, reliable, and the easiest of the five systems to use. Freehand systems are hampered by tracking interference, and integrated microscope systems are still in the early stages of development.

The pterional craniotomy is one of the most versatile approaches in neurosurgery. It is suited not only for vascular pathology arising from the circle of Willis but also for lesions located in or around the cavernous sinus, the sella, and the parasellar and subfrontal regions. When used with other skull base surgical adjuncts, including orbitozygomatic osteotomies and intradural and extradural removal of the clinoid, or combined with other approaches (temporal craniotomy, petrosectomy), a wider area as well as additional structures become accessible. The variations and idiosyncrasies of the pterional craniotomy are many. This article reviews the senior author's techniques for performing this approach.

Various electrophysiological monitoring techniques are available for localizing and protecting cranial nerves and the brain stem during skull-base procedures. Separate neural pathways are used with each method, allowing for the simultaneous monitoring of different cranial nerves and brain stem tracts. Although monitoring of the facial nerve during resection of an acoustic neuroma is considered to be a standard of care, other monitoring techniques, such as tracking motor evoked potentials and visual evoked potentials, have not yet gained wide acceptance with neurosurgeons. This situation is in part attributable to technical factors that create difficulties in interpreting intraoperative changes in these responses. The use of individual techniques is usually based on the surgeon's level of comfort in attacking a given lesion and in his or her perception of the sensitivity and specificity of each type of electrophysiological monitoring.

Patch graft angioplasty is a useful technical alternative for arteriotomy closure. In our experience, patch graft angioplasty has been reserved for patients with recurrent stenosis, those with smaller than normal arteries, and those who have radiation arteriopathy after previous treatment for a malignancy. Patch graft angioplasty is also useful for the repair of smaller caliber vessels such as the vertebral artery. Any closure that decreases the arterial circumference represents an indication for patch graft angioplasty. Various materials, such as autogenous vein or artery and synthetic materials, have been used. This article reviews the advantages and technical aspects of patch angioplasty.

During the last 50 years, the surgical management of extracranial vertebral artery occlusive vascular disease has evolved greatly. A select subset of patients previously unresponsive to medical therapies are now potential candidates for open or endovascular interventions. This article reviews surgical strategies for the treatment of these complex patients.

Atherosclerotic occlusive vascular disease does not affect the vertebrobasilar artery system as often as it does the carotid arteries. When the posterior circulation is affected, however, significant disability and death can result in many of the more advanced cases. In addition to atherosclerotic vascular disease, a number of other pathological conditions can also affect the vertebral arteries and conversely lead to extraluminal occlusive vascular disease and ischemia. The anatomy of the vertebral artery and vascular pathological conditions affecting this vessel are reviewed.