Progress in neurological surgery最新文献

Aggressive resection of intracranial gliomas has a positive impact on patients' prognosis, but is associated with a risk of neurological complications. For preservation of brain functions and avoidance of major postoperative morbidity various methods of intraoperative neurophysiological monitoring have been introduced into clinical practice. At present, somatosensory evoked potentials (SSEP), motor evoked potentials (MEP), visual evoked potentials (VEP), brainstem auditory evoked potentials (BAEP), and electrocorticography (ECoG) are used routinely during neurosurgical procedures. To maximize the efficacy of these neurophysiological techniques, it is most preferable to apply total intravenous anesthesia with continuous infusion of propofol and opioids and avoidance of long-acting muscle relaxants. Surgery for brainstem gliomas requires specific mapping with direct electrical stimulation (DES), corticobulbar tract MEP monitoring, and free-running electromyography (EMG) of the various muscles innervated by the cranial nerves. Awake craniotomy and intraoperative mapping of language and sensorimotor functions with DES allow precise identification of the functionally important neuronal structures and have become standard techniques for removal of cerebral neoplasms affecting eloquent cortical areas and subcortical pathways. Overall, contemporary neurophysiology plays a very important role in guidance of brain tumor surgery, in which it helps to maximize the extent of resection and to minimize the risk of permanent neurological morbidity.

Gliomas encompass a wide spectrum of various histopathological entities with different management strategies and associated prognoses. In many cases, initial biopsy of the brain lesion is required, since definitive diagnosis forms the foundation for treatment decision-making. Tissue sampling can be attained during stereotactic, open, or endoscopic procedures and, overall, provides >90% diagnostic yield, while it may be significantly lower (60-70%) in small (<1 cm3) and/or heterogeneous lesions. In the majority of the modern series, the morbidity rates do not exceed 2.5%. In experienced hands biopsy can be safely attained in any regions of the brain, including eloquent cortex, deep-seated structures, and the brainstem.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is the reference technique in Parkinson's disease (PD) at different stages of complications. Some patients cannot afford DBS due to anticoagulation or comorbidities or due to pecuniary reasons. Radiosurgery is a minimally invasive stereotactic technique, with no craniotomy and subsequently no risk of bleeding or infection. Its good safety efficacy profile has been established in the treatment of tremor, and the postoperative care issues are simple with a much shorter hospital stay (mean 48 h). The application of radiosurgery to STN target in PD as an alternative to DBS is being debated. The lesion of the STN is presumed to induce hemiballism. Experimental works suggest a potential lower risk of hemiballism in animal models of PD. However, radiofrequency ablation of the STN is associated with a significant rate of severe dyskinesia, sometimes permanent and severe enough to request salvage pallidotomies. The positive experience of VIM radiosurgery in tremor and its capacity to create precise, accurate and well-controlled lesions provides reasonable rationale for the evaluation of this technique when applied to STN in PD. Preliminary results till date have shown the absence of severe permanent dyskinesia. Prospective controlled trials are mandatory to evaluate the safety efficacy of this technique in PD.

Movement disorders are common and functionally disabling neurologic diseases. Studies over the last decades have investigated the pathophysiology of these diseases in considerable detail, leading to significant insights into their generation of motor disability. While genetically and clinically heterogeneous, most of them are accompanied by prominent and characteristic changes in firing rates and patterns in the basal ganglia, thalamus, and cortex. In recent years, researchers have placed increasing emphasis on the importance of oscillatory changes in firing in these structures, and have discovered that brain areas that were previously considered to be remote from the basal ganglia (such as the cerebellum and the pedunculopontine nucleus) are also highly significant in these disorders. The evolving pathophysiologic concepts have important implications for improving our understanding of the biology of these disorders, and for the development of more effective pharmacologic and surgical therapies with fewer side effects than seen with the currently available treatments. In this chapter, the known pathophysiology of three common movement disorders, Parkinson's disease, dystonia, and essential tremor, is reviewed.

Low-grade gliomas (LGG), corresponding to WHO grades I and II, are an uncommon and heterogeneous group of tumors, which include several distinct histopathological types and subtypes. Because of their rarity, acquiring adequate data on which to base therapeutic decisions in such cases is difficult. According to present knowledge, it is reasonable to consider radiosurgery (in particular, Gamma Knife surgery) as a therapeutic option for some LGG. Nevertheless, there is a clear need for multicenter cooperation in order to augment the currently scanty data.

Angiogenesis plays a critical pathologic role in malignant gliomas. In the past few years, numerous studies using bevacizumab (BEV), a humanized monoclonal antibody against vascular endothelial growth factor (VEGF), have been conducted in patients with brain tumors. Current evidence suggests that such treatment produces favorable results in patients with recurrent glioblastoma multiforme (GBM), but is not associated with any benefits in newly diagnosed GBM and recurrent WHO grade III gliomas. Initial experience using BEV for management of central nervous system radiation necrosis demonstrated radiographic improvement in the majority of cases, but optimal dose and treatment duration in such cases still remain in question. The results of clinical trials on other antiangiogenic agents in patients with malignant gliomas were generally disappointing. Future therapeutic approaches should include strategies that targets different angiogenic pathways, block tumor invasiveness, and inhibit GBM stem cells. Evaluation of validated biomarkers and novel imaging parameters may eventually allow better selection of patients who will likely benefit from treatment with VEGF inhibitors.

Boron neutron capture therapy (BNCT) is a promising modality for biochemically targeted, highly selective radiation treatment of various cancers, including malignant gliomas. Currently available results demonstrate the beneficial effect of such therapy on survival of patients with both recurrent and newly diagnosed glioblastomas. The main drawback of BNCT in cases of previously irradiated neoplasms is high rates of symptomatic pseudoprogression and radiation necrosis. For prevention of these complications, concurrent administration of bevacizumab may be helpful. Further studies are needed to establish the optimal therapeutic protocols and to define the exact role of this management option in multimodality treatment strategies. Recent technological developments of accelerator-based neutron sources may simplify placement of the device for BNCT within clinical facilities and lead to wider application of this technique in cases of various cancers.

Recently, the clinical applications of photodynamic therapy (PDT) in the management of malignant brain tumors have attracted significant attention. Meta-analysis of the observational studies on this treatment in high-grade gliomas (Eljamel, 2010) included more than 1,000 patients and reported median survival in cases of newly diagnosed and recurrent glioblastoma multiforme (GBM) of 16.1 and 10.3 months, respectively. In some series, increase in the long-term survival rates was also observed. Few controlled trials demonstrated statistically significant impact of PDT on prolongation of survival in patients with GBM in comparison to conventional management. The main treatment-related adverse event is short-lasting excessive photosensitivity of the skin and retina after photosensitizer administration, but its negative consequences can be easily avoided with appropriate protective measures. Overall, PDT may be considered to be a safe and effective adjuvant therapeutic option for patients with newly diagnosed and recurrent malignant gliomas. Aggressive tumor resection seems to be an important prerequisite to maximize treatment efficacy.

Cytokines are a heterogeneous group of soluble small polypeptides or glycoproteins, which exert pleiotropic and redundant effects that promote growth, differentiation, and activation of cells. Cytokine production plays a profound role in the modulation of the tumor microenvironment, including the host of heterogeneous neoplastic cells, immune cells, and extracellular matrix, which is essential for progression of the neoplasm. Depending on specific conditions, the cytokines can either upregulate or downregulate anti-inflammatory and immunosuppressive activities. The crosstalk between cytokines and their receptors in the tumor microenvironment constitutes the target for various types of cytokine therapies that have been tested until now for treatment of patients with intracranial glioma.

Gliomas are the most common primary intracranial neoplasms, which cause significant mortality and morbidity that is disproportionate to their relatively rare incidence. Many potential risk factors for glioma have been studied to date, but only few provide explanation for the number of brain tumor cases identified. The most significant findings include increased risk due to exposure to ionizing radiation and decreased risk with the history of allergy or atopic diseases. The potential effect of the cellular phone usage has been evaluated extensively, but the results remain inconclusive. A very small proportion of gliomas can be attributed to inherited genetic disorders. Additionally, recent analyses using the genome-wide association study design have identified several inherited genomic risk variants.