Progress in neurological surgery最新文献

Gamma Knife radiosurgery (GKRS) of cerebral arteriovenous malformations (AVM) is an accepted treatment option that has been performed for more than 40 years. The goal of AVM GKRS is nidus obliteration to eliminate the risk of intracranial hemorrhage while minimizing the risk of short- and long-term adverse radiation effects (ARE). Nidus obliteration typically occurs between 1 and 5 years after GKRS. The most important factor associated with nidus obliteration is the prescribed radiation dose. The chance of obliteration ranges from 60 to 70% for margin doses of 15-16 Gy to 90% or more for margin doses of 20-25 Gy. Neurologic decline after GKRS can occur from either hemorrhage or ARE. Numerous studies have shown that the risk of AVM bleeding is either unchanged or decreased following GKRS. Advances in neuroimaging and dose-planning software have reduced the incidence of early ARE to <4%. Volume-staged procedures can be safely performed for large-volume AVM that were previously considered too large for GKRS. Late ARE (generally cyst formation) are common in patients who develop early MRI imaging changes (areas of high T2 signal) after GKRS, but most cases can be managed with either observation or resection of the thrombosed AVM.

Vestibular schwannomas (VS) are benign tumors predominantly originating from the balance portion of cranial nerve VIII. These tumors have an incidence of 1-2 per 100,000 people. The growth of these tumors is approximately 1-2 mm per year. A VS can result in significant neurologic dysfunction from continued growth or the management paradigms designed to control this predominantly benign tumor. The impacts on the critical space within the auditory canal and cerebellopontine angle can lead to hearing deficits, tinnitus, vestibular dysfunction, facial nerve deficits, and brain stem compression.

Radiosurgery is an effective treatment approach for the management of type 1 trigeminal neuralgia (TN), comparable to other ablative techniques. Also, radiosurgery can effectively treat TN secondary to other causes, including multiple sclerosis, tumor-related TN, as well as other craniofacial neuralgias in select cases with minimal complications. An increasing number of patients favor radiosurgery over other more invasive approaches in order to avoid a general anesthetic, a prolonged hospital stay, and a higher risk of complications.

Since its first reported use in 1976 in Sweden, Gamma Knife (GK) radiosurgery has become an accepted treatment option for intracranial meningioma, either upfront, in combination with planned subtotal resection, or as adjuvant/salvage treatment. Initially, GK was used in patients unfit for a major surgical procedure or for high-risk meningiomas adjacent to critical neurovascular structures. However, with the availability of larger and increasingly long-term follow-up studies, the proven durability of GK in the treatment of meningiomas means that it has become a treatment option for younger patients who want to avoid the risks of open surgery. Here we review the current indications, radiobiology, and patient outcomes following GK for intracranial meningioma 50 years on from its inception.

The classification of central neurocytoma (CN) by the WHO was upgraded to grade 2 in 1993 as it was recognized that at least some of these tumors can exhibit more aggressive behavior. Currently, as of 2016, CN is classified as WHO grade 2. Indeed, some atypical variants have been reported and residual postsurgical tumor is believed to have the potential for malignant transformation. Although gross total resection is usually curative for CN (5-year survival rate 99%), it is achieved in nearly 30-50% of cases due to its central location. Adjuvant treatments should be deliberately considered for the optimal management of CN. Recently, stereotactic radiosurgery is increasingly proposed as an adjuvant treatment for CN.

Pineal region tumors represent a heterogeneous group of different histologic entities, for which the management can be a significant challenge, due to their critical location and frequent aggressive behavior. Traditional management includes surgical resection, fractionated radiation therapy, and chemotherapy. Stereotactic radiosurgery (SRS) is being increasingly used in the treatment of these tumors. It is used as primary therapy for pineocytomas and papillary tumors of the pineal region, as an adjuvant radiation boost in combination with radiation or chemotherapy for pineoblastomas and germ cell tumors, or in the context of tumor recurrence. The reported morbidity is low, consisting in transient oculomotor disturbance in most cases. As a non-invasive alternative to microsurgical resection, SRS should always be considered when discussing these challenging cases.

Intracranial dural arteriovenous fistulas (DAVFs) are abnormal arteriovenous connections within the dura, in which meningeal arteries shunt blood directly into the dural sinus or leptomeningeal veins. Among all the treatment options for the treatment of DAVFs, stereotactic radiosurgery (SRS) is a safe and effective modality. SRS provides a minimally invasive therapy for patients who harbor less aggressive DAVFs without cortical vein drainage (CVD), but who suffer from intolerable headache, bruit, or ocular symptoms. For more aggressive DAVFs with CVD associated with immediate risks of hemorrhage, initial treatment with endovascular embolization or surgery for the prompt elimination of the aggressive components of DAVFs is necessary. In such cases, radiosurgery may serve as a secondary treatment for further management of residual nidus after initial intervention. The latent period for the effects of radiation to occur and the longer time for cure compared to surgery and endovascular therapy remains a major drawback for radiosurgery. However, the gradual obliteration of a DAVF after radiosurgery can avoid the immediate risk of aggravated venous hypertension or infarction, which sometimes complicates endovascular embolization and surgery.

For more than 65 years localization of brain targets suitable for stereotactic radiosurgery has been performed after application of an intracranial guiding device to the cranial vault. After imaging and dose planning the same frame is used to secure the target at the focus of the intersection of the ionizing radiation beams that create the radiobiological effect. Non-invasive immobilization systems first proposed for linear accelerator or proton radiation technologies have now been developed for the Leksell Gamma Knife ICON radiosurgical system. The ICON technology adds a cone-beam computed tomography (CBCT) scan to the original Perfexion radiosurgical device in order to define the brain stereotactic space. Marketed since 2015, the ICON can be used for standard radiosurgical procedures, most of which remain frame based, but also coupled with a non-invasive thermoplastic mask for carefully selected patients who undergo standard single-session radiosurgical procedures, as well as multisession procedures using repeat mask fixation. Both at UPMC as well as worldwide, mask immobilization has to date been used for approximately 10% of patients with specific characteristics: relatively simple dose plans, short radiation delivery times, and non-anxious patients, most of whom have metastatic or primary brain cancers. In certain cases, multisession radiosurgery is also performed using the mask. The workflow of frame versus frameless procedures is often altered, and is reliant on high-definition imaging, mostly MRI, done prior to dose planning. Since each CBCT takes 10-12 min to set up and acquire, co-register, and review with the treatment plan, and two CBCT scans are necessary to initiate the treatment plan, this workflow must be added to the beam on time. Although frame-based immobilization remains the predominant method to secure target fixation for problems suitable for single-session radiosurgery, the advent of a mask immobilization technique has proven valuable for a select group of patients. It also provides a non-invasive method to perform multisession or fractionated radiation in patients for whom traditional single-session radiosurgery is not feasible.