This article reviews the current status of surgical treatment of epilepsy and introduces the ongoing challenges. Seizure outcome of resective surgery for focal seizures associated with focal lesions is satisfactory. Particularly for mesial temporal lobe epilepsy, surgical treatment should be considered from the earlier stage of the disease. Meanwhile, surgical outcome in nonlesional extratemporal lobe epilepsy is still to be improved using various approaches. Disconnective surgeries reduce surgical complications of extensive resections while achieving equivalent or better seizure outcomes. Multiple subpial transection is still being modified expecting a better outcome by transection to the vertical cortices along the sulci- and multi-directional transection from a single entry point. Hippocampal transection is expected to preserve memory function while interrupting the abnormal epileptic synchronization. Proper selection or combination of subdural and depth electrodes and a wide-band analysis of electroencephalography may improve the accurate localization of epileptogenic region. Patients for whom curative resective surgery is not indicated because of generalized or bilateral multiple nature of their epilepsies, neuromodulation therapies are options of treatment which palliate their seizures.
Awake craniotomy is the only established way to assess patients’ language functions intraoperatively and to contribute to their preservation, if necessary. Recent guidelines have enabled the approach to be used widely, effectively, and safely. Non-invasive brain functional imaging techniques, including functional magnetic resonance imaging and diffusion tensor imaging, have been used preoperatively to identify brain functional regions corresponding to language, and their accuracy has increased year by year. In addition, the use of neuronavigation that incorporates this preoperative information has made it possible to identify the positional relationships between the lesion and functional regions involved in language, conduct functional brain mapping in the awake state with electrical stimulation, and intraoperatively assess nerve function in real time when resecting the lesion. This article outlines the history of awake craniotomy, the current state of pre- and intraoperative evaluation of language function, and the clinical usefulness of such functional evaluation. When evaluating patients’ language functions during awake craniotomy, given the various intraoperative stresses involved, it is necessary to carefully select the tasks to be undertaken, quickly perform all examinations, and promptly evaluate the results. As language functions involve both input and output, they are strongly affected by patients’ preoperative cognitive function, degree of intraoperative wakefulness and fatigue, the ability to produce verbal articulations and utterances, as well as perform synergic movement. Therefore, it is essential to appropriately assess the reproducibility of language function evaluation using awake craniotomy techniques.
There has been a paradigm shift in the understanding of brain function. The intrinsic architecture of neuronal connections forms a key component of the cortical organization in our brain. Many imaging studies, such as noninvasive magnetic resonance imaging (MRI) studies, have now enabled visualization of the white matter fiber tracts interconnecting the functional cortical areas in the living brain. Although such a structural connectome is essential for understanding of cortical function, the anatomical information alone is not sufficient. Practically, few techniques allow the investigation of the excitatory and inhibitory mechanisms of the cortex in vivo in humans. Several attempts have been made to track neuronal connectivity by applying direct electrical stimuli to the brain in order to stimulate subdural and/or depth electrodes and record responses from the functionally connected cortex. In vivo single-pulse electrical stimulation (SPES) and/or cortico-cortical evoked potential (CCEP) were recently introduced to track various brain networks. This article reviews the concepts, significance, methods, mechanisms, limitations, and clinical applications of CCEP in the analysis of these dynamic connections.
A growing number of papers have pointed out the relationship between aggressive resection of gliomas and survival prognosis. For maximum resection, the current concept of surgical decision-making is in “information-guided surgery” using multimodal intraoperative information. With this, anatomical information from intraoperative magnetic resonance imaging (MRI) and navigation, functional information from brain mapping and monitoring, and histopathological information must all be taken into account in the new perspective for innovative minimally invasive surgical treatment of glioma. Intraoperative neurofunctional information such as neurophysiological functional monitoring takes the most important part in the process to acquire objective visual data during tumor removal and to integrate these findings as digitized data for intraoperative surgical decision-making. Moreover, the analysis of qualitative data and threshold-setting for quantitative data raise difficult issues in the interpretation and processing of each data type, such as determination of motor evoked potential (MEP) decline, underestimation in tractography, and judgments of patient response for neurofunctional mapping and monitoring during awake craniotomy. Neurofunctional diagnosis of false-positives in these situations may affect the extent of resection, while false-negatives influence intra- and postoperative complication rates. Additionally, even though the various intraoperative visualized data from multiple sources contribute significantly to the reliability of surgical decisions when the information is integrated and provided, it is not uncommon for individual pieces of information to convey opposing suggestions. Such conflicting pieces of information facilitate higher-order decision-making that is dependent on the policies of the facility and the priorities of the patient, as well as the availability of the histopathological characteristics from resected tissue.
Pediatric epilepsy has a wide variety of etiology and severity. A recent epidemiological study suggested that surgery might be indicated in as many as 5% of the pediatric epilepsy population. Now, we know that effective epilepsy surgery can result in seizure freedom and improvement of psychomotor development. Seizure control is the most effective way to improve patients neurologically and psychologically. In this review, we look over the recent evidence related to pediatric epilepsy surgery, and try to establish the optimal surgical timing for patients with intractable epilepsy. Appropriate surgical timing depends on the etiology and natural history of the epilepsy to be treated. The most common etiology of pediatric intractable epilepsy patients is malformation of cortical development (MCD) and early surgery is recommended for them. Patients operated on earlier than 12 months of age tended to improve their psychomotor development compared to those operated on later. Recent progress in neuroimaging and electrophysiological studies provide the possibility of very early diagnosis and comprehensive surgical management even at an age before 12 months. Epilepsy surgery is the only solution for patients with MCD or other congenital diseases associated with intractable epilepsy, therefore physicians should aim at an early and precise diagnosis and predicting the future damage, consider a surgical solution within an optimal timing.
Vagus nerve stimulation (VNS) provides palliation of seizure reduction for patients with medically refractory epilepsy. VNS is indicated for symptomatic localization-related epilepsy with multiple and bilateral independent foci, symptomatic generalized epilepsy with diffuse epileptogenic abnormalities, refractory idiopathic generalized epilepsy, failed intracranial epilepsy surgery, and other several reasons of contraindications to epilepsy surgery. Programing of the parameters is a principal part in VNS. Output current and duty cycle should be adjusted to higher settings particularly when a patient does not respond to the initial setting, since the pivotal randomized trials performed in the United States demonstrated high stimulation made better responses in seizure frequency. These trials revealed that a ≥ 50% seizure reduction occurred in 36.8% of patients at 1 year, in 43.2% at 2 years, and in 42.7% at 3 years in 440 patients. Safety of VNS was also confirmed because side effects including hoarseness, throat discomfort, cough, paresthesia, and headache improved progressively during the period of 3 years. The largest retrospective study with 436 patients demonstrated the mean seizure reduction of 55.8% in nearly 5 years, and also found 75.5% at 10 years in 65 consecutive patients. The intermediate analysis report of the Japan VNS Registry showed that 60% of 164 cases got a ≥ 50% seizure reduction in 12 months. In addition to seizure reduction, VNS has positive effects in mood and improves energy level, memory difficulties, social aspects, and fear of seizures. VNS is an effective and safe option for patients who are not suitable candidates for intracranial epilepsy surgery.
The use of electrical stimulation to treat pain in human disease dates back to ancient Rome or Greece. Modern deep brain stimulation (DBS) was initially applied for pain treatment in the 1960s, and was later used to treat movement disorders in the 1990s. After recognition of DBS as a therapy for central nervous system (CNS) circuit disorders, DBS use showed drastic increase in terms of adaptability to disease and the patient’s population. More than 100,000 patients have received DBS therapy worldwide. The established indications for DBS are Parkinson’s disease, tremor, and dystonia, whereas global indications of DBS expanded to other neuronal diseases or disorders such as neuropathic pain, epilepsy, and tinnitus. DBS is also experimentally used to manage cognitive disorders and psychiatric diseases such as major depression, obsessive-compulsive disorder (OCD), Tourette’s syndrome, and eating disorders. The importance of ethics and conflicts surrounding the regulation and freedom of choice associated with the application of DBS therapy for new diseases or disorders is increasing. These debates are centered on the use of DBS to treat new diseases and disorders as well as its potential to enhance ability in normal healthy individuals. Here we present three issues that need to be addressed in the future: (1) elucidation of the mechanisms of DBS, (2) development of new DBS methods, and (3) miniaturization of the DBS system. With the use of DBS, functional neurosurgery entered into the new era that man can manage and control the brain circuit to treat intractable neuronal diseases and disorders.
To date, deep brain stimulation (DBS) has already been performed on more than 120,000 patients worldwide and in more than 7,000 patients in Japan. However, fundamental understanding of DBS effects on the pathological neural circuitry remains insufficient. Recent studies have specifically shown the importance of cortico-striato-thalamo-cortical (CSTC) loops, which were identified as functionally and anatomically discrete units. Three main circuits exist in the CSTC loops, namely, the motor, associative, and limbic circuits. From these theoretical backgrounds, it is determined that DBS sometimes influences not only motor functions but also the cognitive and affective functions of Parkinson’s disease (PD) patients. The main targets of DBS for PD are subthalamic nucleus (STN) and globus pallidus interna (GPi). Ventralis intermedius (Vim)-DBS was found to be effective in improving tremor. However, Vim-DBS cannot sufficiently improve akinesia and rigidity. Therefore, Vim-DBS is seldom carried out for the treatment of PD. In this article, we review the present state of DBS, mainly STN-DBS and GPi-DBS, for PD. In the first part of the article, appropriate indications and practical effects established in previous studies are discussed. The findings of previous investigations on the complications caused by the surgical procedure and on the adverse events induced by DBS itself are reviewed. In the second part, we discuss target selection (GPi vs. STN) and the effect of DBS on nonmotor symptoms. In the final part, as issues that should be resolved, the suitable timing of surgery, symptoms unresponsive to DBS such as on-period axial symptoms, and the related postoperative programing of stimulation parameters, are discussed.
Microvascular decompression (MVD) is a highly effective surgical treatment for trigeminal neuralgia (TN). Although there is little prospective clinical evidence, accumulated observational studies have demonstrated the benefits of MVD for refractory TN. In the current surgical practice of MVD for TN, there have been recognized patterns and variations in surgical anatomy and various decompression techniques. Here we provide a stepwise description of surgical procedures and relevant anatomical characteristics, as well as procedural options.
Awake surgery could be a useful modality for lesions locating in close proximity to the eloquent areas including primary motor cortex and pyramidal tract. In case with supplementary motor area (SMA) lesion, we often encounter with intraoperative motor symptoms during awake surgery even in area without positive mapping. Although the usual recovery of the SMA syndrome has been well documented, rare cases with permanent deficits could be encountered in the clinical setting. It has been difficult to evaluate during surgery whether the intraoperative motor symptoms lead to postoperative permanent deficits. The purpose of this study was to demonstrate the intraoperative motor symptoms could be reversible, further to provide useful information for making decision to continue surgical procedure of tumor resection. Eight consecutive patients (from July 2012 to June 2014, six men and two women, aged 33–63 years) with neoplastic lesions around the SMA underwent an awake surgery. Using a retrospective analysis of intraoperative video records, intraoperative motor symptoms during tumor resection were investigated. In continuous functional monitoring during resection of SMA tumor under awake conditions, the following motor symptoms were observed during resection of the region without positive mapping: delayed motor weakness, delay of movement initiation, slowness of movement, difficulty in dual task response, and coordination disturbance. In seven patients hemiparesis observed immediately after surgery recovered to preoperative level within 6 weeks. During awake surgery for SMA tumors, the above-mentioned motor symptoms could occur in area without positive mapping and might be predictors for reversible SMA syndrome.