Sustained focal cortical compression reduces electrically-induced seizure threshold

Subdural osteoma in an adolescent patient with epilepsy: an unusual case report and literature review

OBJECTIVE

Subdural osteoma (SO) is a rarely reported benign tumor, and there is no report of SO manifested with epileptic seizures. We aim to further the understanding of SO-related epilepsy.

METHODS

Here, we report a meaningful case of epilepsy secondary to SO. A systematic review of the literature about SO using the electronic database PubMed and Web of science up to December 2022 was conducted.

RESULTS

A 15-year-old girl presented with epileptic seizures for 8 years. Magnetic resonance imaging revealed an irregular lesion with heterogeneous signal in the right frontal convexity. Right frontal craniotomy was performed to remove the lesion. The pathological diagnosis was SO. Histological analysis revealed that the mechanosensitive ion channels Piezo 1/2 were upregulated in the brain tissue compressed by the osteoma, compared with the levels in the osteoma-free region. Seizure freedom was obtained during the 6-month follow-up after the surgery. We identified 24 cases of SO in 23 articles. With our case, a total of 25 cases with 32 SOs was included. Of 25 cases, 24 are adults, and 1 is a child. Seizure has been reported only in our case. Frontal osteoma was found in 76% of the patients. Symptoms were cured in 56% of the patients after surgery.

CONCLUSION

Surgery is a safe and effective approach to the treatment of symptomatic osteoma. Mechanical compression on cerebral cortex may be a predisposing factor of the epileptogenesis caused by the SO.

Association between minimally invasive surgery and late seizures in patients with intracerebral hemorrhage: A propensity score matching study

Purpose

The association between minimally invasive surgery (MIS) for hematoma evacuation and late seizures after intracerebral hemorrhage (ICH) remains uncertain. We aimed to investigate whether MIS increases the risk of late seizures after ICH and identify the risk factors for late seizures in this patient subgroup.

Methods

We retrospectively included consecutive inpatients diagnosed with ICH at two tertiary hospitals in China. The subjects were divided into the MIS group (ICH patients who received MIS including hematoma aspiration and thrombolysis) and conservative treatment group (ICH patients who received conservative medication). Propensity score matching was performed to balance possible risk factors for late seizures between the MIS and conservative treatment groups. Before and after matching, between-group comparisons of the incidence of late seizures were performed between the MIS and conservative treatment groups. Univariate and multivariate logistic regression analyses were used to identify independent risk factors for late seizures in MIS-treated patients.

Results

A total of 241 and 1,689 patients were eligible for the MIS and conservative treatment groups, respectively. After matching, 161 ICH patients from the MIS group were successfully matched with 161 ICH patients from the conservative treatment group (1:1). Significant differences (p < 0.001) were found between the MIS group (31/241, 12.9%) and conservative treatment group (69/1689, 4.1%) in the incidence of late seizures before matching. However, after matching, no significant differences (p = 0.854) were found between the MIS group (17/161, 10.6%) and conservative treatment group (16/161, 9.9%). Multivariate logistic regression analysis revealed that cortical involvement (OR = 2.547; 95% CI = 1.137-5.705; p value = 0.023) and higher National Institutes of Health Stroke Scale (NIHSS) scores (OR = 1.050; 95% CI = 1.008-1.094; p value = 0.019) were independent risk factors for late seizures.

Conclusion

Our study revealed that receiving MIS did not increase the incidence of late seizures after ICH. Additionally, cortical involvement and NIHSS scores were independent risk factors for late seizures in MIS-treated patients.

Increased Expression of Epileptiform Spike/Wave Discharges One Year after Mild, Moderate, or Severe Fluid Percussion Brain Injury in Rats

In this study, we describe increased expression of cortical epileptiform spike/wave discharges (SWD) in rats one year after mild, moderate, or severe fluid percussion traumatic brain injury (fpTBI). Groups of rats consisted of animals that had received mild, moderate, or severe fpTBI, or sham operation one year earlier than electrocorticography (ECoG) recordings. In addition, we included a group of age-matched naïve animals. ECoG was recorded from awake animals using epidural electrodes implanted on the injured hemisphere (right), sham-operated hemisphere (right), or right hemisphere in naïve animals. The SWDs were detected automatically using Fast Fourier Transformation and a novel algorithm for comparing changes in spectral power to control (nonepileptical) ECoG. The fpTBI resulted in increased expression of SWDs one year after injury compared with sham-operated or naïve animals. The number of SWD-containing ECoG epochs recorded in a 1 h recording session were: naïve 12.9 ± 10.3, n = 8, sham 23.6 ± 8.2, n = 10, mild TBI 78.9 ± 23.9, n = 10, moderate TBI 61.3 ± 32.5, n = 12, severe TBI 72.5 ± 28.3, n = 11 (mean ± standard error of the mean). Increased expression of SWDs was not related to injury severity. SWDs were observed to a lesser extent even in sham-operated and naïve animals. The data indicate that fpTBI exacerbates expression of SWDs in the rat and that this increase may be observed at least one year after injury. As others have discussed, the spontaneous occurrence of these epileptiform events in rodents limits the use of this model for investigations of acquired epilepsy, at least of the nonconvulsive type, after TBI.

Histological evaluation of a chronically-implanted electrocorticographic electrode grid in a non-human primate

OBJECTIVE

Electrocorticography (ECoG), used as a neural recording modality for brain-machine interfaces (BMIs), potentially allows for field potentials to be recorded from the surface of the cerebral cortex for long durations without suffering the host-tissue reaction to the extent that it is common with intracortical microelectrodes. Though the stability of signals obtained from chronically implanted ECoG electrodes has begun receiving attention, to date little work has characterized the effects of long-term implantation of ECoG electrodes on underlying cortical tissue.

APPROACH

We implanted and recorded from a high-density ECoG electrode grid subdurally over cortical motor areas of a Rhesus macaque for 666 d.

MAIN RESULTS

Histological analysis revealed minimal damage to the cortex underneath the implant, though the grid itself was encapsulated in collagenous tissue. We observed macrophages and foreign body giant cells at the tissue-array interface, indicative of a stereotypical foreign body response. Despite this encapsulation, cortical modulation during reaching movements was observed more than 18 months post-implantation.

SIGNIFICANCE

These results suggest that ECoG may provide a means by which stable chronic cortical recordings can be obtained with comparatively little tissue damage, facilitating the development of clinically viable BMI systems.

Transplanted Neural Progenitor Cells from Distinct Sources Migrate Differentially in an Organotypic Model of Brain Injury

Brain injury is a major cause of long-term disability. The possibility exists for exogenously derived neural progenitor cells to repair damage resulting from brain injury, although more information is needed to successfully implement this promising therapy. To test the ability of neural progenitor cells (NPCs) obtained from rats to repair damaged neocortex, we transplanted neural progenitor cell suspensions into normal and injured slice cultures of the neocortex acquired from rats on postnatal day 0–3. Donor cells from E16 embryos were obtained from either the neocortex, including the ventricular zone (VZ) for excitatory cells, ganglionic eminence (GE) for inhibitory cells or a mixed population of the two. Cells were injected into the ventricular/subventricular zone (VZ/SVZ) or directly into the wounded region. Transplanted cells migrated throughout the cortical plate with GE and mixed population donor cells predominately targeting the upper cortical layers, while neocortically derived NPCs from the VZ/SVZ migrated less extensively. In the injured neocortex, transplanted cells moved predominantly into the wounded area. NPCs derived from the GE tended to be immunoreactive for GABAergic markers while those derived from the neocortex were more strongly immunoreactive for other neuronal markers such as MAP2, TUJ1, or Milli-Mark. Cells transplanted in vitro acquired the electrophysiological characteristics of neurons, including action potential generation and reception of spontaneous synaptic activity. This suggests that transplanted cells differentiate into neurons capable of functionally integrating with the host tissue. Together, our data suggest that transplantation of neural progenitor cells holds great potential as an emerging therapeutic intervention for restoring function lost to brain damage.

Reversible alterations of the neuronal activity in spontaneous intracranial hypotension

AIM

The aim of this article is to investigate the pathophysiology underlying the alternation of the cognitive function and neuronal activity in spontaneous intracranial hypotension (SIH).

METHODS

Fifteen patients with SIH underwent resting-state functional magnetic resonance imaging and working-memory (WM) test one day before and one month after a surgical operation. Alternation of the cognitive function and spontaneous neuronal activity measured as amplitude of the low-frequency fluctuations (ALFF) and the functional connectivity of the default-mode network (DMN) and frontoparietal networks (FPNs) were evaluated.

RESULTS

WM performance significantly improved post-operatively. Whole-brain linear regression analysis of the ALFF revealed a positive correlation between cognitive performance change and ALFF change in the precuneus while a negative correlation was found in the bilateral orbitofrontal cortices (OFCs) and right medial frontal cortex (MFC). The ALFF changes normalised with the WM performance improvement post-operatively. The FPN activity in the right OFC was also increased pre-operatively. Partial correlation analysis revealed a significant correlation between WM performance and right OFC activity controlled for right FPN activity.

CONCLUSIONS

The abnormal activity of the OFCs and MFC that is not originating from the synchronous intrinsic network activity, together with the decreased activity of the central node of the DMN, could lead to cognitive impairment in SIH that is reversible through restoration of the cerebrospinal fluid.

Reliability of VEP Recordings Using Chronically Implanted Screw Electrodes in Mice

PURPOSE

Visual evoked potentials (VEPs) are widely used to objectively assess visual system function in animal models of ophthalmological diseases. Although use of chronically implanted electrodes is common in longitudinal VEP studies using rodent models, reliability of recordings over time has not been assessed. We compared VEPs 1 and 7 days after electrode implantation in the adult mouse. We also examined stimulus-independent changes over time, by assessing electroencephalogram (EEG) power and approximate entropy of the EEG signal.

METHODS

Stainless steel screws (600-μm diameter) were implanted into the skull overlying the right visual cortex and the orbitofrontal cortex of adult mice (C57Bl/6J, n = 7). Animals were reanesthetized 1 and 7 days after implantation to record VEP responses (flashed gratings) and EEG activity. Brain sections were stained for glial activation (GFAP) and cell death (TUNEL).

RESULTS

Reliability analysis, using intraclass correlation coefficients, showed VEP recordings had high reliability within the same session, regardless of time after electrode implantation and peak latencies and approximate entropy of the EEG did not change significantly with time. However, there was poorer reliability between recordings obtained on different days, and a significant decrease in VEP amplitudes and EEG power. This amplitude decrease could be normalized by scaling to EEG power (within-subjects). Furthermore, glial activation was present at both time points but there was no evidence of cell death.

CONCLUSIONS

These results indicate that VEP responses can be reliably recorded even after a relatively short recovery period but decrease response peak amplitude over time. Although scaling the VEP trace to EEG power normalized this decrease, our results highlight that time-dependent cortical excitability changes are an important consideration in longitudinal VEP studies.

TRANSLATIONAL RELEVANCE

This study shows changes in VEP characteristics over time in chronically implanted mice. Thus, future preclinical longitudinal studies should consider time in addition to amplitude and latency when designing and interpreting research.

NMDA receptor triggered molecular cascade underlies compression-induced rapid dendritic spine plasticity in cortical neurons

Compression causes the reduction of dendritic spines of underlying adult cortical pyramidal neurons but the mechanisms remain at large. Using a rat epidural cerebral compression model, dendritic spines on the more superficial-lying layer III pyramidal neurons were found quickly reduced in 12h, while those on the deep-located layer V pyramidal neurons were reduced slightly later, starting 1day following compression. No change in the synaptic vesicle markers synaptophysin and vesicular glutamate transporter 1 suggest no change in afferents. Postsynaptically, N-methyl-d-aspartate (NMDA) receptor trafficking to synaptic membrane was detected in 10min and lasting to 1day after compression. Translocation of calcineurin to synapses and enhancement of its enzymatic activity were detected within 10min as well. These suggest that compression rapidly activated NMDA receptors to increase postsynaptic calcium, which then activated the phosphatase calcineurin. In line with this, dephosphorylation and activation of the actin severing protein cofilin, and the consequent depolymerization of actin were all identified in the compressed cortex within matching time frames. Antagonizing NMDA receptors with MK801 before compression prevented this cascade of events, including NR1 mobilization, calcineurin activation and actin depolymerization, in the affected cortex. Morphologically, MK801 pretreatment prevented the loss of dendritic spines on the compressed cortical pyramidal neurons as well. In short, we demonstrated, for the first time, mechanisms underlying the rapid compression-induced cortical neuronal dendritic spine plasticity. In addition, the mechanical force of compression appears to activate NMDA receptors to initiate a rapid postsynaptic molecular cascade to trim dendritic spines on the compressed cortical pyramidal neurons within half a day.

Environmental enrichment and the sensory brain: the role of enrichment in remediating brain injury

The brain's life-long capacity for experience-dependent plasticity allows adaptation to new environments or to changes in the environment, and to changes in internal brain states such as occurs in brain damage. Since the initial discovery by Hebb (1947) that environmental enrichment (EE) was able to confer improvements in cognitive behavior, EE has been investigated as a powerful form of experience-dependent plasticity. Animal studies have shown that exposure to EE results in a number of molecular and morphological alterations, which are thought to underpin changes in neuronal function and ultimately, behavior. These consequences of EE make it ideally suited for investigation into its use as a potential therapy after neurological disorders, such as traumatic brain injury (TBI). In this review, we aim to first briefly discuss the effects of EE on behavior and neuronal function, followed by a review of the underlying molecular and structural changes that account for EE-dependent plasticity in the normal (uninjured) adult brain. We then extend this review to specifically address the role of EE in the treatment of experimental TBI, where we will discuss the demonstrated sensorimotor and cognitive benefits associated with exposure to EE, and their possible mechanisms. Finally, we will explore the use of EE-based rehabilitation in the treatment of human TBI patients, highlighting the remaining questions regarding the effects of EE.

Sensory cortex underpinnings of traumatic brain injury deficits

Traumatic brain injury (TBI) can result in persistent sensorimotor and cognitive deficits including long-term altered sensory processing. The few animal models of sensory cortical processing effects of TBI have been limited to examination of effects immediately after TBI and only in some layers of cortex. We have now used the rat whisker tactile system and the cortex processing whisker-derived input to provide a highly detailed description of TBI-induced long-term changes in neuronal responses across the entire columnar network in primary sensory cortex. Brain injury (n = 19) was induced using an impact acceleration method and sham controls received surgery only (n = 15). Animals were tested in a range of sensorimotor behaviour tasks prior to and up to 6 weeks post-injury when there were still significant sensorimotor behaviour deficits. At 8–10 weeks post-trauma, in terminal experiments, extracellular recordings were obtained from barrel cortex neurons in response to whisker motion, including motion that mimicked whisker motion observed in awake animals undertaking different tasks. In cortex, there were lamina-specific neuronal response alterations that appeared to reflect local circuit changes. Hyper-excitation was found only in supragranular layers involved in intra-areal processing and long-range integration, and only for stimulation with complex, naturalistic whisker motion patterns and not for stimulation with simple trapezoidal whisker motion. Thus TBI induces long-term directional changes in integrative sensory cortical layers that depend on the complexity of the incoming sensory information. The nature of these changes allow predictions as to what types of sensory processes may be affected in TBI and contribute to post-trauma sensorimotor deficits.

Cortical excitation and inhibition following focal traumatic brain injury

Cortical compression can be a significant problem in many types of brain injuries, such as brain trauma, localized brain edema, hematoma, focal cerebral ischemia, or brain tumors. Mechanical and cellular alterations can result in global changes in excitation and inhibition on the neuronal network level even in the absence of histologically significant cell injury, often manifesting clinically as seizures. Despite the importance and prevalence of this problem, however, the precise electrophysiological effects of brain injury have not been well characterized. In this study, the changes in electrophysiology were characterized following sustained cortical compression using large-scale, multielectrode measurement of multiunit activity in primary somatosensory cortex in a sensory-evoked, in vivo animal model. Immediately following the initiation of injury at a distal site, there was a period of suppression of the evoked response in the rat somatosensory cortex, followed by hyper-excitability that was accompanied by an increase in the spatial extent of cortical activation. Paired-pulse tactile stimulation revealed a dramatic shift in the excitatory/inhibitory dynamics, suggesting a longer term hyperexcitability of the cortical circuit following the initial suppression that could be linked to the disruption of one or more inhibitory mechanisms of the thalamocortical circuit. Together, our results showed that the use of a sensory-evoked response provided a robust and repeatable functional marker of the evolution of the consequences of mild injury, serving as an important step toward in vivo quantification of alterations in excitation and inhibition in the cortex in the setting of traumatic brain injury.