Alexandra Taylor

High-frequency oscillations in epilepsy and surgical outcome. A meta-analysis

High frequency oscillations (HFOs) are estimated as a potential marker for epileptogenicity. Current research strives for valid evidence that these HFOs could aid the delineation of the to-be resected area in patients with refractory epilepsy and improve surgical outcomes. In the present meta-analysis, we evaluated the relation between resection of regions from which HFOs can be detected and outcome after epilepsy surgery. We conducted a systematic review of all studies that related the resection of HFO-generating areas to postsurgical outcome. We related the outcome (seizure freedom) to resection ratio, that is, the ratio between the number of channels on which HFOs were detected and, among these, the number of channels that were inside the resected area. We compared the resection ratio between seizure free and not seizure free patients. In total, 11 studies were included. In 10 studies, ripples (80–200 Hz) were analyzed, and in 7 studies, fast ripples (>200 Hz) were studied. We found comparable differences (dif) and largely overlapping confidence intervals (CI) in resection ratios between outcome groups for ripples (dif = 0.18; CI: 0.10–0.27) and fast ripples (dif = 0.17; CI: 0.01–0.33). Subgroup analysis showed that automated detection (dif = 0.22; CI: 0.03–0.41) was comparable to visual detection (dif = 0.17; CI: 0.08–0.27). Considering frequency of HFOs (dif = 0.24; CI: 0.09–0.38) was related more strongly to outcome than considering each electrode that was showing HFOs (dif = 0.15; CI = 0.03–0.27). The effect sizes found in the meta-analysis are small but significant. Automated detection and application of a detection threshold in order to detect channels with a frequent occurrence of HFOs is important to yield a marker that could be useful in presurgical evaluation. In order to compare studies with different methodological approaches, detailed and standardized reporting is warranted.

Noninvasive Spinal Cord Stimulation: Technical Aspects and Therapeutic Applications.

Electrical and magnetic trans‐spinal stimulation can be used to increase the motor output of multiple spinal segments and modulate cortico‐spinal excitability. The application of direct current through the scalp as well as repetitive transcranial magnetic stimulation are known to influence brain excitability, and hence can also modulate other central nervous system structures, including spinal cord.

Minimal hepatic encephalopathy: A review

Minimal hepatic encephalopathy (MHE) is the earliest form of hepatic encephalopathy and can affect up to 80% of patients with liver cirrhosis. By definition, MHE is characterized by cognitive function impairment in the domains of attention, vigilance and integrative function, but obvious clinical manifestation are lacking. MHE has been shown to affect daily functioning, quality of life, driving and overall mortality. The diagnosis can be achieved through neuropsychological testing, recently developed computerized psychometric tests, such as the critical flicker frequency and the inhibitory control tests, as well as neurophysiological procedures. Event related potentials can reveal subtle changes in patients with normal neuropsychological performances. Spectral analysis of electroencephalography (EEG) and quantitative analysis of sleep EEG provide early markers of cerebral dysfunction in cirrhotic patients with MHE. Neuroimaging, in particular MRI, also increasingly reveals diffuse abnormalities in intrinsic brain activity and altered organization of functional connectivity networks. Medical treatment for MHE to date has been focused on reducing serum ammonia levels and includes non-absorbable disaccharides, probiotics or rifaximin. Liver transplantation may not reverse the cognitive deficits associated with MHE. We performed here an updated review on epidemiology, burden and quality of life, neuropsychological testing, neuroimaging, neurophysiology and therapy in subjects with MHE.

Canine degenerative myelopathy: a model of human amyotrophic lateral sclerosis

Canine degenerative myelopathy (CDM) represents a unique naturally occurring animal model for human amyotrophic lateral sclerosis (ALS) because of similar clinical signs, neuropathologic findings, and involvement of the superoxide dismutase 1 (SOD1) mutation. A definitive diagnosis can only be made postmortem through microscopic detection of axonal degeneration, demyelination and astroglial proliferation, which is more severe in the dorsal columns of the thoracic spinal cord and in the dorsal portion of the lateral funiculus. Interestingly, the muscle acetylcholine receptor complexes are intact in CDM prior to functional impairment, thus suggesting that muscle atrophy in CDM does not result from physical denervation. Moreover, since sensory involvement seems to play an important role in CDM progression, a more careful investigation of the sensory pathology in ALS is also warranted. The importance of SOD1 expression remains unclear, while oxidative stress and denatured ubiquinated proteins appear to play a crucial role in the pathogenesis of CDM. In this updated narrative review we performed a systematic search of the published studies on CDM that may shed light on the pathophysiological mechanisms of human ALS. A better understanding of the factors that determine the disease progression in CDM may be beneficial for the development of effective treatments for ALS.

Variability Issues in Automated Hippocampal Segmentation: A Study on Out-of-the-Box Software and Multi-rater Ground Truth

In automated hippocampus segmentation, issues related to ground truth rater variability, subject variability and variability of software segmentation accuracy are investigated in the context of 3 publicly available, out-of-the-box software packages. Ground truth variability among three manual raters is controlled using a majority voting based label fusion scheme and observed subject variability underpins the importance of availability of large scale ground truth.

Pathology-Related Automated Hippocampus Segmentation Accuracy

Hippocampal segmentation accuracy of out-of-the-box software tools (FreeSurfer, AHEAD, BrainParser) is analysed wrt. potential variability in populations with different pathologies. Findings confirm variabilities wrt. different pathologies but also human rater ground truth and single pathologies exhibit significant variability as well.

Effects of theta burst stimulation on referred phantom sensations in patients with spinal cord injury.

To further explore the mechanisms underlying cortical reorganization in patients with phantom sensations after deafferentation, a repetitive transcranial magnetic stimulation study was carried out in two patients with referred phantom sensations (RPS) after incomplete spinal cord injury at the thoracic level. We delivered continuous (inhibitory), intermittent (excitatory), and placebo theta burst stimulation to the contralateral primary motor cortex (M1), primary somatosensory cortex (S1), and secondary somatosensory cortex (S2). Perception of RPS was significantly and transiently disrupted by inhibitory theta burst stimulation applied over S1 and, to a lesser extent, S2. This study supports the hypothesis that RPS depend on remapping in the somatosensory cortex and provides further electrophysiological evidence in vivo that cortical reorganizational processes are critically modulated by GABAergic mechanisms. Enhancement of GABAergic activity may block cortical reorganization, leading to RPS in spinal cord injury patients.

Potential years lost and life expectancy in adults with newly diagnosed epilepsy

Studies using relative measures, such as standardized mortality ratios, have shown that patients with epilepsy have an increased mortality. Reports on more direct and absolute measure such as life expectancy are sparse. We report potential years lost and how life expectancy has changed over 40 years in a cohort of patients with newly diagnosed epilepsy.