Clinical Application of Machine Learning Models for Brain Imaging in Epilepsy: A Review

Epilepsy is a common neurological disorder characterized by recurrent and disabling seizures. An increasing number of clinical and experimental applications of machine learning (ML) methods for epilepsy and other neurological and psychiatric disorders are available. ML methods have the potential to provide a reliable and optimal performance for clinical diagnoses, prediction, and personalized medicine by using mathematical algorithms and computational approaches. There are now several applications of ML for epilepsy, including neuroimaging analyses. For precise and reliable clinical applications in epilepsy and neuroimaging, the diverse ML methodologies should be examined and validated. We review the clinical applications of ML models for brain imaging in epilepsy obtained from a PubMed database search in February 2021. We first present an overview of typical neuroimaging modalities and ML models used in the epilepsy studies and then focus on the existing applications of ML models for brain imaging in epilepsy based on the following clinical aspects: (i) distinguishing individuals with epilepsy from healthy controls, (ii) lateralization of the temporal lobe epilepsy focus, (iii) the identification of epileptogenic foci, (iv) the prediction of clinical outcomes, and (v) brain-age prediction. We address the practical problems and challenges described in the literature and suggest some future research directions.

The use of simultaneous stereo-electroencephalography and magnetoencephalography in localising the epileptogenic focus in refractory focal epilepsy

Both magnetoencephalography and stereo-electroencephalography are used in presurgical epilepsy assessment, with contrasting advantages and limitations. It is not known whether simultaneous stereo-electroencephalography-magnetoencephalography recording confers an advantage over both individual modalities, in particular whether magnetoencephalography can provide spatial context to epileptiform activity seen on stereo-electroencephalography. 24 adult and paediatric patients who underwent stereo-electroencephalography study for pre-surgical evaluation of drug-resistant focal epilepsy, were recorded using simultaneous stereo-electroencephalography-magnetoencephalography, of which 14 had abnormal interictal activity during recording. The 14 patients were divided into two groups; those with detected superficial (n = 7) and deep (n = 7) brain interictal activity. Interictal spikes were independently identified in stereo-electroencephalography and magnetoencephalography. Magnetoencephalography dipoles were derived using a distributed inverse method. There was no significant difference between stereo-electroencephalography and magnetoencephalography in detecting superficial spikes (p = 0.135) and stereo-electroencephalography was significantly better at detecting deep spikes (p = 0.002). Mean distance across patients between stereo-electroencephalography channel with highest average spike amplitude and magnetoencephalography dipole was 20.7+/- 4.4 mm. for superficial sources, and 17.8 +/- 3.7 mm. for deep sources, even though for some of the latter (n = 4) no magnetoencephalography spikes were detected and magnetoencephalography dipole was fitted to a stereo-electroencephalography interictal activity triggered average. Removal of magnetoencephalography dipole was associated with 1 year seizure freedom in 6/7 patients with superficial source, and 5/6 patients with deep source. Although stereo-electroencephalography has greater sensitivity in identifying interictal activity from deeper sources, a magnetoencephalography source can be localised using stereo-electroencephalography information, thereby providing useful whole brain context to stereo-electroencephalography and potential role in epilepsy surgery planning.In the largest case series to date, Vivekananda et al. perform simultaneous magnetoencephalography and stereo-electroencephalography in refractory focal epilepsy patients. They demonstrate that for deep brain epileptogenic foci, magnetoencephalography dipoles could be derived from average stereo-electroencephalography data, thereby overcoming a traditional limitation of magnetoencephalography of reduced sensitivity for deep sources.

The Role of ASIC1a in Epilepsy: A Potential Therapeutic Target

Background: Epilepsy represents one of the most common brain diseases among humans. Tissue acidosis is a common phenomenon in epileptogenic foci. This said, its roles in epileptogenesis remain unclear. Acid-sensing ion channel-1a (ASIC1a) represents a potential way to assess new therapies. ASIC1a, mainly expressed in the mammalian brain, is a type of protein-gated cation channel. It has been shown to play an important role in the pathological mechanism of various diseases, including stroke, epilepsy, and multiple sclerosis. Methods: Data were collected from Web of Science, Medline, PubMed, through searching for these keywords: "Acid-sensing ion channels 1a" or "ASIC1a" and "epilepsy" or "seizure". Results: The role of ASIC1a in epilepsy remains controversial; it may represent a promising therapeutic target of epilepsy. Conclusion:This review is intended to provide an overview of the structure, trafficking, and molecular mechanisms of ASIC1a in order to further elucidate the role of ASIC1a in epilepsy.

Surgical treatment of epilepsy at the Russian Children’s Clinical Hospital: substrates and imaging aspects

Introduction. MRI revealing the epileptogenic foci is the central part of the presurgical evaluation of children with focal-resistant epilepsy. Besides that, MRI seems to be a reliable instrument of treatment optimization and good prognosis. Aim. To identify epileptogenic lesions in children with resistant focal epilepsy by high resolution (HR) MRI and comparing obtained data with postsurgical morphology. Materials and methods. We assessed the results of neuroimaging, EEG, clinical neurological status, and postsurgical morphological data in 65 children with focal epilepsy who had undergone antiepileptic surgery in Russian State Children Hospital, neurosurgery department (Moscow, Russia) from 2016 to 2020. Results. The broad spectrum of epileptogenic lesions was revealed by HR MRI, including focal and diffuse cortical dysplasias (44.6%), cortical post hypoxic gliosis (27.7%), glial tumors (7.7%), Rasmussen encephalitis (10.8%), tuberous sclerosis, and Sturge-Weber syndrome (3%), small angiodysplasias (4.6%) and other. Focal cerebral dysplasia had an obvious superiority as the main etiological factor in focal epilepsy and was approved in 33.8% of all patients. In all cases, epilepsy is characterized by frequent and resistant seizures, inflicting motor arrest, and psycho-emotional deterioration. Conclusion. HR MRI and multidisciplinary investigation have to be unchangeable standards in the presurgical evaluation of children with focal epilepsy. This approach’s effectiveness has reassuring confirmation by high level (95.2%) of total coincidence MRI and morphological results.

Pediatric Epilepsy Surgery in Focal and Generalized Epilepsy: Current Trends and Recent Advancements

For a subset of children with medically intractable epilepsy, surgery may provide the best chances of seizure freedom. Whereas the indications for epilepsy surgery are commonly thought to be limited to patients with focal epileptogenic foci, modern imaging and surgical interventions frequently permit successful surgical treatment of generalized epilepsy. Resection continues to be the only potentially curative intervention; however, the advent of various neuromodulation interventions provides an effective palliative strategy for generalized or persistent seizures. Although the risks and benefits vary greatly by type and extent of intervention, the seizure outcomes appear to be uniformly favorable. Advances in both resective and nonresective surgical interventions provide promise for improved seizure freedom, function, and quality of life. This review summarizes the current trends and recent advancements in pediatric epilepsy surgery from diagnostic workup and indications through surgical interventions and postoperative outcomes.

Arteriovenous malformation presenting with epilepsy: a multimodal approach to diagnosis and treatment

Arteriovenous malformation (AVM) presenting with epilepsy significantly impacts patient quality of life, and it should be considered very much a seizure disorder. Although hemorrhage prevention is the primary treatment aim of AVM surgery, seizure control should also be at the forefront of therapeutic management. Several hemodynamic and morphological characteristics of AVM have been identified to be associated with seizure presentation. This includes increased AVM flow, presence of long pial draining vein, venous outflow obstruction, and frontotemporal location, among other aspects. With the advent of high-throughput image processing and quantification methods, new radiographic attributes of AVM-related epilepsy have been identified. With respect to therapy, several treatment approaches are available, including conservative management or interventional modalities; this includes microsurgery, radiosurgery, and embolization or a combination thereof. Many studies, especially in the domain of microsurgery and radiosurgery, evaluate both techniques with respect to seizure outcomes. The advantage of microsurgery lies in superior AVM obliteration rates and swift seizure response. In addition, by incorporating electrophysiological monitoring during AVM resection, adjacent or even remote epileptogenic foci can be identified, leading to extended lesionectomy and improved seizure control. Radiosurgery, despite resulting in reduced AVM obliteration and prolonged time to seizure freedom, avoids the risks of surgery altogether and may provide seizure control through various antiepileptic mechanisms. Embolization continues to be used as an adjuvant for both microsurgery and radiosurgery. In this study, the authors review the latest imaging techniques in characterizing AVM-related epilepsy, in addition to reviewing each treatment modality.

Cingulate gyrus epilepsy: semiology, invasive EEG, and surgical approaches

OBJECTIVEThe semiology of cingulate gyrus epilepsy is varied and may involve the paracentral area, the adjacent limbic system, and/or the orbitofrontal gyrus. Invasive electroencephalography (iEEG) recording is usually required for patients with deeply located epileptogenic foci. This paper reports on the authors’ experiences in the diagnosis and surgical treatment of patients with focal epilepsy originating in the cingulate gyrus.METHODSEighteen patients (median age 24 years, range 5–53 years) with a mean seizure history of 23 years (range 2–32 years) were analyzed retrospectively. The results of presurgical evaluation, surgical strategy, and postoperative pathology are reported, as well as follow-up concerning functional morbidity and seizures (median follow-up 7 years, range 2–12 years).RESULTSPatients with cingulate gyrus epilepsy presented with a variety of semiologies and scalp EEG patterns. Prior to ictal onset, 11 (61%) of the patients presented with aura. Initial ictal symptoms included limb posturing in 12 (67%), vocalization in 5, and hypermotor movement in 4. In most patients (n = 16, 89%), ictal EEG presented as widespread patterns with bilateral hemispheric origin, as well as muscle artifacts obscuring the onset of EEG during the ictal period in 11 patients. Among the 18 patients who underwent resection, the pathology revealed mild malformation of cortical development in 2, focal cortical dysplasia (FCD) Ib in 4, FCD IIa in 4, FCD IIb in 4, astrocytoma in 1, ganglioglioma in 1, and gliosis in 2. The seizure outcome after surgery was satisfactory: Engel class IA in 12 patients, IIB in 3, IIIA in 1, IIIB in 1, and IVB in 1 at the 2-year follow-up.CONCLUSIONSIn this study, the authors exploited the improved access to the cingulate epileptogenic network made possible by the use of 3D electrodes implanted using stereoelectroencephalography methodology. Under iEEG recording and intraoperative neuromonitoring, epilepsy surgery on lesions in the cingulate gyrus can result in good outcomes in terms of seizure recurrence and the incidence of postoperative permanent deficits.