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ObjectiveAcute organophosphate (OP) intoxication affects a significant number of individuals worldwide. Those who survive OP-induced cholinergic crisis, which includes status epilepticus, often develop neurological morbidities. Here, we provide a rigorous characterization of the acute and delayed electrophysiological responses to OP intoxication with the goal of identifying early electrophysiological changes that predict later brain changes, including spontaneous recurrent seizures (SRS).MethodsMale and female rats were implanted with electroencephalographic (EEG) and intracranial EEG electrodes prior to acute intoxication with diisopropylfluorophosphate (DFP). All animals received standard of care therapeutics and were recorded continuously for 70 min post-DFP, then again for 5 min at 180 min post-DFP, 1 day postexposure (DPE), 3 DPE, and 7 DPE. Between 7 and 14 DPE, animals were recorded continuously.ResultsIn both sexes, acute DFP intoxication produced rapid and robust elevations in broadband power that were reduced but not terminated by midazolam (MDZ). Theta-delta ratio (TDR) was reduced immediately following DFP exposure and was further depressed by MDZ intervention. In the days that followed, broadband power and TDR recovered toward baseline. From 7 to 14 DPE, electrographic spiking was observed in all animals, and 80% developed SRS. Increased broadband power during status epilepticus was positively correlated with spike rate and SRS frequency. Slower recovery of broadband power to baseline in the days following exposure also correlated with increased SRS burden. Finally, a higher acute TDR correlated with increased spike rates at 3 and 7 DPE.SignificanceThe data presented in this study provide a rigorous characterization of post-DFP electrographic sequelae that significantly extends the field's current understanding of electrophysiological shifts caused by acute OP intoxication. Critically, we identified potential EEG-based biomarkers that may identify at-risk patients in a clinical setting.

The mechanisms of cognitive decline after intraventricular hemorrhage (IVH) in some patients continue to be poorly understood. Multiple rodent models of intraventricular or subarachnoid hemorrhage have only shown mild or even no cognitive impairment on subsequent behavioral testing. In this study, we show that intraventricular hemorrhage only leads to a significant spatial memory deficit in the Morris water maze if it occurs in the setting of an elevated intracranial pressure (ICP). Histopathological analysis of these IVH + ICP animals did not show evidence of neuronal degeneration in the hippocampal formation after 2 weeks but instead showed significant microglial activation measured by lacunarity and fractal dimensions. RNA sequencing of the hippocampus showed distinct enrichment of genes in the IVH + ICP group but not in IVH alone having activated microglial signaling pathways. The most significantly activated signaling pathway was the classical complement pathway, which is used by microglia to remove synapses, followed by activation of the Fc receptor and DAP12 pathways. Thus, our study lays the groundwork for identifying signaling pathways that could be targeted to ameliorate behavioral deficits after IVH.

Our previous studies demonstrated that traumatic brain injury (TBI) and ventricular administration of thrombin caused hippocampal neuron loss and cognitive dysfunction via activation of Src family kinases (SFKs). Based on SFK localization in brain, we hypothesized SFK subtypes Fyn and c-Src, as well as SFK downstream molecule Rho-associated protein kinase (ROCK), contribute to cell death and cognitive dysfunction after TBI. We administered nanoparticle wrapped small interfering RNA (siRNA)-Fyn and siRNA-c-Src, or ROCK inhibitor Y-27632 to adult rats subjected to moderate lateral fluid percussion (LFP)-induced TBI. Spatial memory function was assessed from 12 to 16 days, and NeuN stained hippocampal neurons were assessed 16 days after TBI. The combination of siRNA-Fyn and siRNA-c-Src, but neither alone, prevented hippocampal neuron loss and spatial memory deficits after TBI. The ROCK inhibitor Y-27632 also prevented hippocampal neuronal loss and spatial memory deficits after TBI. The data suggest that the combined actions of three kinases (Fyn, c-Src, ROCK) mediate hippocampal neuronal cell death and spatial memory deficits produced by LFP-TBI, and that inhibiting this pathway prevents the TBI-induced cell death and memory deficits.

The interaction of age, sex, and outcomes of children with head injury remains incompletely understood and these factors need rigorous evaluation in prognostic models for pediatric head injury. We leveraged our large institutional pediatric TBI population to evaluate age and sex along with a series of predictive factors used in the acute care of injury to describe the response and outcome of children and adolescents with moderate to severe injury. We hypothesized that younger age at injury and male sex would be associated with adverse outcomes and that a novel GCS-based scale incorporating pupillary response (GCS-P) would have superior performance in predicting 6-month outcome. GCS and GCS-P along with established CT scan variables associated with neurologic outcomes were retrospectively reviewed in children (age birth to 18 years) with moderate or severe head injury. GOS-E was prospectively collected 6 months after injury; 570 patients were enrolled in the study, 520 with TBI and 50 with abusive head trauma, each analyzed separately. In the TBI cohort, the median age of patients was 8 years and 42.7% had a severe head injury. Multiple predictors of outcome were identified in univariate analysis; however, based on a multivariate analysis, the GCS was identified as most reliable, outperforming GCS-P, pupil score, and other clinical and CT scan predictors. After stratifying patients for severity of injury by GCS, no age- or sex-related effects were observed in our patient population, except for a trend toward worse outcomes in the neonatal group. Patients with abusive head trauma were more likely to have severe injury on presentation, increased mortality rate, and unfavorable outcome. Additionally, there was clear evidence that secondary injuries, including hypoxia, hypotension, and hypothermia were significantly associated with lower GCS and higher mortality in both AHT and TBI populations. Our findings support the use of GCS to guide clinical decision-making and prognostication in addition to emphasizing the need to stratify head injuries for severity when undertaking outcome studies. Finally, secondary injuries are a clear predictor of poor outcome and how we record and manage these events need to be considered moving forward.

Traumatic brain injury (TBI) causes acute and lasting impacts on the brain, driving pathology along anatomical, cellular, and behavioral dimensions. Rodent models offer an opportunity to study the temporal progression of disease from injury to recovery. Transcriptomic and epigenomic analysis were applied to evaluate gene expression in ipsilateral hippocampus at 1 and 14 days after sham (n = 2 and 4, respectively per time point) and moderate lateral fluid percussion injury (n = 4 per time point). This enabled the identification of dynamic changes and differential gene expression (differentially expressed genes; DEGs) modules linked to underlying epigenetic response. We observed acute signatures associated with cell death, astrocytosis, and neurotransmission that largely recovered by 2 weeks. Inflammation and immune signatures segregated into upregulated modules with distinct expression trajectories and functions. Whereas most down-regulated genes recovered by 14 days, two modules with delayed and persistent changes were associated with cholesterol metabolism, amyloid beta clearance, and neurodegeneration. Differential expression was paralleled by changes in histone H3 lysine residue 4 trimethylation at the promoters of DEGs at 1 day post-TBI, with the strongest changes observed for inflammation and immune response genes. These results demonstrate how integrated genomics analysis in the pre-clinical setting has the potential to identify stage-specific biomarkers for injury and/or recovery. Though limited in scope here, our general strategy has the potential to capture pathological signatures over time and evaluate treatment efficacy at the systems level.

Over one-third of patients with temporal lobe epilepsy are refractory to medication. In addition, anti-epileptic drugs often exacerbate cognitive comorbidities. Neuromodulation is an FDA treatment for refractory epilepsy, but patients often wait >20 years for a surgical referral for resection or neuromodulation. Using a rodent model, we test the hypothesis that 2 weeks of theta stimulation of the medial septum acutely following exposure to pilocarpine will alter the course of epileptogenesis resulting in persistent behavioral improvements. Electrodes were implanted in the medial septum, dorsal and ventral hippocampus, and the pre-frontal cortex of pilocarpine-treated rats. Rats received 30 min/day of 7.7 Hz or theta burst frequency on days 4-16 post-pilocarpine, prior to the development of spontaneous seizures. Seizure threshold, spikes, and oscillatory activity, as well as spatial and object-based learning, were assessed in the weeks following stimulation. Non-stimulated pilocarpine animals exhibited significantly decreased seizure threshold, increased spikes, and cognitive impairments as compared to vehicle controls. Furthermore, decreased ventral hippocampal power (6-10 Hz) correlated with both the development of spikes and impaired cognition. Measures of spikes, seizure threshold, and cognitive performance in both acute 7.7 Hz and theta burst stimulated animals were statistically similar to vehicle controls when tested during the chronic phase of epilepsy, weeks after stimulation was terminated. These data indicate that modulation of the septohippocampal circuit early after pilocarpine treatment alters the progression of epileptic activity, resulting in elevated seizure thresholds, fewer spikes, and improved cognitive outcome. Results from this study support that septal theta stimulation has the potential to serve in combination or as an alternative to high frequency thalamic stimulation in refractory cases and that further research into early intervention is critical.

Preclinical efforts to improve medical countermeasures against organophosphate (OP) chemical threat agents have largely focused on adult male models. However, age and sex have been shown to influence the neurotoxicity of repeated low-level OP exposure. Therefore, to determine the influence of sex and age on outcomes associated with acute OP intoxication, postnatal day 28 Sprague-Dawley male and female rats were exposed to the OP diisopropylfluorophosphate (DFP; 3.4 mg/kg, s.c.) or an equal volume of vehicle (∼80 µL saline, s.c.) followed by atropine sulfate (0.1 mg/kg, i.m.) and pralidoxime (2-PAM; 25 mg/kg, i.m.). Seizure activity was assessed during the first 4 h post-exposure using behavioral criteria and electroencephalographic (EEG) recordings. At 1 d post-exposure, acetylcholinesterase (AChE) activity was measured in cortical tissue, and at 1, 7, and 28 d post-exposure, brains were collected for neuropathologic analyses. At 1 month post-DFP, animals were analyzed for motor ability, learning and memory, and hippocampal neurogenesis. Acute DFP intoxication triggered more severe seizure behavior in males than females, which was supported by EEG recordings. DFP caused significant neurodegeneration and persistent microglial activation in numerous brain regions of both sexes, but astrogliosis occurred earlier and was more severe in males compared to females. DFP males and females exhibited pronounced memory deficits relative to sex-matched controls. In contrast, acute DFP intoxication altered hippocampal neurogenesis in males, but not females. These findings demonstrate that acute DFP intoxication triggers seizures in juvenile rats of both sexes, but the seizure severity varies by sex. Some, but not all, chronic neurotoxic outcomes also varied by sex. The spatiotemporal patterns of neurological damage suggest that microglial activation may be a more important factor than astrogliosis or altered neurogenesis in the pathogenesis of cognitive deficits in juvenile rats acutely intoxicated with OPs.

Aneurysmal intraventricular hemorrhage (IVH) survivors may recover with significant deficits in learning and memory. The goal of this study was to investigate the mechanism of memory decline after intraventricular aneurysm rupture. We developed an aneurysmal IVH rat model by injecting autologous, arterial blood over the period of two minutes into the right lateral ventricle. We also evaluated the effects of a volume-matched artificial cerebrospinal fluid (CSF) control, thrombin and the mode of delivery (pulsed hand injection versus continuous pump infusion). We performed magnetic resonance brain imaging after 1 and 5 weeks to evaluate for hydrocephalus and histological analysis of the dentate gyrus after 6 weeks. Only animals which underwent a whole blood pulsed hand injection had a spatial memory acquisition and retention deficit 5 weeks later. These animals had larger ventricles at 1 and 5 weeks than animals which underwent a continuous pump infusion of whole blood. We did not find a decline in dentate gyrus granule cell neurons or an impairment in dentate gyrus neurogenesis or differentiation 6 weeks after IVH. Rapid injections of blood or volume resulted in microglial activation in the dentate gyrus. In conclusion, our results point to mechanical injury as the predominant mechanism of memory decline after intraventricular aneurysmal rupture. However, volume-matched pulsed injections of artificial CSF did not create a spatial memory deficit at 5 weeks. Therefore, whole blood itself must play a role in the mechanism. Further research is required to evaluate whether the viscosity of blood causes additional mechanical disruption and hydrocephalus through a primary injury mechanism or whether the toxicity of blood causes a secondary injury mechanism that leads to the observed spatial memory deficit after 5 weeks.

Whether from a fall, sports concussion, or even combat injury, there is a critical need to identify when an individual is able to return to play or work following traumatic brain injury (TBI). Electroencephalogram (EEG) and local field potentials (LFP) represent potential tools to monitor circuit-level abnormalities related to learning and memory: specifically, theta oscillations can be readily observed and play a critical role in cognition. Following moderate traumatic brain injury in the rat, lasting changes in theta oscillations coincide with deficits in spatial learning. We hypothesized, therefore, that theta oscillations can be used as an objective biomarker of recovery, with a return of oscillatory activity corresponding with improved spatial learning. In the current study, LFP were recorded from dorsal hippocampus and anterior cingulate in awake, behaving adult Sprague Dawley rats in both a novel environment on post-injury days 3 and 7, and Barnes maze spatial navigation on post-injury days 8-11. Theta oscillations, as measured by power, theta-delta ratio, peak theta frequency, and phase coherence, were significantly altered on day 3, but had largely recovered by day 7 post-injury. Injured rats had a mild behavioral phenotype and were not different from shams on the Barnes maze, as measured by escape latency. Injured rats did use suboptimal search strategies. Combined with our previous findings that demonstrated a correlation between persistent alterations in theta oscillations and spatial learning deficits, these new data suggest that neural oscillations, and particularly theta oscillations, have potential as a biomarker to monitor recovery of brain function following TBI. Specifically, we now demonstrate that oscillations are depressed following injury, but as oscillations recover, so does behavior.

Traumatic brain injury (TBI) can result in persistent cognitive, behavioral and emotional deficits. However, the vast majority of patients are not chronically hospitalized; rather they have to manage their disabilities once they are discharged to home. Promoting recovery to pre-injury level is important from a patient care as well as a societal perspective. Electrical neuromodulation is one approach that has shown promise in alleviating symptoms associated with neurological disorders such as in Parkinson's disease (PD) and epilepsy. Consistent with this perspective, both animal and clinical studies have revealed that TBI alters physiological oscillatory rhythms. More recently several studies demonstrated that low frequency stimulation improves cognitive outcome in models of TBI. Specifically, stimulation of the septohippocampal circuit in the theta frequency entrained oscillations and improved spatial learning following TBI. In order to evaluate the potential of electrical deep brain stimulation for clinical translation we review the basic neurophysiology of oscillations, their role in cognition and how they are changed post-TBI. Furthermore, we highlight several factors for future pre-clinical and clinical studies to consider, with the hope that it will promote a hypothesis driven approach to subsequent experimental designs and ultimately successful translation to improve outcome in patients with TBI.

Traumatic brain injury (TBI) often results in persistent attention and memory deficits that are associated with hippocampal dysfunction. Although deep brain stimulation (DBS) is used to treat neurological disorders related to motor dysfunction, the effectiveness of stimulation to treat cognition remains largely unknown. In this study, adult male Harlan Sprague-Dawley rats underwent a lateral fluid percussion or sham injury followed by implantation of bipolar electrodes in the medial septal nucleus (MSN) and ipsilateral hippocampus. In the first week after injury, there was a significant decrease in hippocampal theta oscillations that correlated with decreased object exploration and impaired performance in the Barnes maze spatial learning task. Continuous 7.7 Hz theta stimulation of the medial septum significantly increased hippocampal theta oscillations, restored normal object exploration, and improved spatial learning in injured animals. There were no benefits with 100 Hz gamma stimulation, and stimulation of sham animals at either frequency did not enhance performance. We conclude, therefore, that there was a theta frequency-specific benefit of DBS that restored cognitive function in brain-injured rats. These data suggest that septal theta stimulation may be an effective and novel neuromodulatory therapy for treatment of persistent cognitive deficits following TBI.

AimTo study the risks and benefits of intracerebroventricular (ICV) opiate pumps for the management of benign head and face pain.MethodsSSix patients with refractory trigeminal neuralgia and/or cluster headaches were evaluated for implantation of an ICV opiate infusion pump using either ICV injections through an Ommaya reservoir or external ventricular drain. Four patients received morphine ICV pumps and two patientS received a hydromorphone pump. Of the Four patients with morphine ICV pumps, one patient had the medication changed to hydromorphone. Preoperative and post-operative visual analog scores (VAS) were obtained. Patients were evaluated post-operatively for a minimum of 3 mo and the pump dosage was adjusted at each outpatient clinic visit according to the patient's pain level.ResultsAll 6 patients had an intracerebroventricular opiate injection trial period, using either an Ommaya reservoir or an external ventricular drain. There was an average VAS improvement of 75.8%. During the trial period, no complications were observed. Pump implantation was performed an average of 3.7 wk (range 1-7) after the trial injections. After implantation, an average of 20.7 ± 8.3 dose adjustments were made over 3-56 mo after surgery to achieve maximal pain relief. At the most recent follow-up (26.2 mo, range 3-56), VAS scores significantly improved from an average of 7.8 ± 0.5 (range 6-10) to 2.8 ± 0.7 (range 0-5) at the final dose (mean improvement 5.0 ± 1.0, P < 0.001). All patients required a stepwise increase in opiate infusion rates to achieve maximal benefit. The most common complications were nausea and drowsiness, both of which resolved with pump adjustments. On average, infusion pumps were replaced every 4-5 years.ConclusionThese results suggest that ICV delivery of opiates may potentially be a viable treatment option for patients with intractable pain from trigeminal neuralgia or cluster headache.

Objective: Acute organophosphate (OP) intoxication affects a significant number of individuals worldwide. Those who survive OP-induced cholinergic crisis, which includes status epilepticus, often develop neurological morbidities. Here, we provide a rigorous characterization of the acute and delayed electrophysiological responses to OP intoxication with the goal of identifying early electrophysiological changes that predict later brain changes, including spontaneous recurrent seizures (SRS)., Methods: Male and female rats were implanted with electroencephalographic (EEG) and intracranial EEG electrodes prior to acute intoxication with diisopropylfluorophosphate (DFP). All animals received standard of care therapeutics and were recorded continuously for 70 min post-DFP, then again for 5 min at 180 min post-DFP, 1 day postexposure (DPE), 3 DPE, and 7 DPE. Between 7 and 14 DPE, animals were recorded continuously., Results: In both sexes, acute DFP intoxication produced rapid and robust elevations in broadband power that were reduced but not terminated by midazolam (MDZ). Theta-delta ratio (TDR) was reduced immediately following DFP exposure and was further depressed by MDZ intervention. In the days that followed, broadband power and TDR recovered toward baseline. From 7 to 14 DPE, electrographic spiking was observed in all animals, and 80% developed SRS. Increased broadband power during status epilepticus was positively correlated with spike rate and SRS frequency. Slower recovery of broadband power to baseline in the days following exposure also correlated with increased SRS burden. Finally, a higher acute TDR correlated with increased spike rates at 3 and 7 DPE., Significance: The data presented in this study provide a rigorous characterization of post-DFP electrographic sequelae that significantly extends the field's current understanding of electrophysiological shifts caused by acute OP intoxication. Critically, we identified potential EEG-based biomarkers that may identify at-risk patients in a clinical setting., (© 2025 The Author(s). Epilepsia published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.)