Mustafa Q. Hameed

Ceftriaxone Treatment after Traumatic Brain Injury Restores Expression of the Glutamate Transporter, GLT-1, Reduces Regional Gliosis, and Reduces Post-Traumatic Seizures in the Rat

Excessive extracellular glutamate after traumatic brain injury (TBI) contributes to excitotoxic cell death and likely to post-traumatic epilepsy. Glutamate transport is the only known mechanism of extracellular glutamate clearance, and glutamate transporter 1 (GLT-1) is the major glutamate transporter of the mammalian brain. We tested, by immunoblot, in the rat lateral fluid percussion injury TBI model whether GLT-1 expression is depressed in the cortex after TBI, and whether GLT-1 expression after TBI is restored after treatment with ceftriaxone, a well-tolerated β-lactam antibiotic previously shown to enhance GLT-1 expression in noninjured animals. We then tested whether treatment with ceftriaxone mitigates the associated regional astrogliosis, as reflected by glial fibrillary acid protein (GFAP) expression, and also whether ceftriaxone treatment mitigates the severity of post-traumatic epilepsy. We found that 7 days after TBI, GLT-1 expression in the ipsilesional cortex was reduced by 29% (n=7/group; p<0.01), relative to the contralesional cortex. However, the loss of GLT-1 expression was reversed by treatment with ceftriaxone (200 mg/kg, daily, intraperitoneally). We found that ceftriaxone treatment also decreased the level of regional GFAP expression by 43% in the lesioned cortex, relative to control treatment with saline (n=7 per group; p<0.05), and, 12 weeks after injury, reduced cumulative post-traumatic seizure duration (n=6 rats in the ceftriaxone treatment group and n=5 rats in the saline control group; p<0.001). We cautiously conclude that our data suggest a potential role for ceftriaxone in treatment of epileptogenic TBI.

VEGF, which is elevated in the CSF of patients with hydrocephalus, causes ventriculomegaly and ependymal changes in rats

Hydrocephalus is a condition characterized primarily by excessive accumulation of fluid in the ventricles of the brain for which there is currently no effective pharmacological treatment. Surgery, often accompanied by complications, is the only current treatment. Extensive research in our laboratory along with work from others has suggested a link between hydrocephalus and vascular function. We hypothesized that vascular endothelial growth factor (VEGF), the major angiogenic factor, could play a role in the pathogenesis of hydrocephalus. We tested this hypothesis by examining two predictions of such a link: first, that VEGF is present in many cases of clinical hydrocephalus; and second, that exogenous VEGF in an animal model could cause ventricular enlargement and tissue changes associated with hydrocephalus. Our results support the idea that VEGF elevation can potentiate hydrocephalus. The clinical relevance of this work is that anti-angiogenic drugs may be useful in patients with hydrocephalus, either alone or in combination with the currently available surgical treatments.

A rapid lateral fluid percussion injury rodent model of traumatic brain injury and post-traumatic epilepsy.

Traumatic brain injury is a leading cause of acquired epilepsy. Initially described in 1989, lateral fluid percussion injury (LFPI) has since become the most extensively used and well-characterized rodent traumatic brain injury and post-traumatic epilepsy model. Universal findings, particularly seizures that reliably develop after an initial latent period, are evident across studies from multiple laboratories. However, the LFPI procedure is a two-stage process, requiring initial surgical attachment of a skull fluid cannula and then reanesthesia for delivery of the epidural fluid pressure wave. We now describe a modification of the original technique, termed ‘rapid lateral fluid percussion injury’ (rLFPI), which allows for a one-stage procedure and thus shorter operating time and reduced anesthesia exposure. Anesthetized male Long–Evans rats were subjected to rLFPI through a length of plastic tubing fitted with a pipette tip cannula with a 4-mm aperture. The cannula opening was positioned over a craniectomy of slightly smaller diameter and exposed dura such that the edges of the cannula fit tightly when pressed to the skull with a micromanipulator. Fluid percussion was then delivered immediately thereafter, in the same surgery session. rLFPI resulted in nonlethal focal cortical injury in all animals. We previously demonstrated that the rLFPI procedure resulted in post-traumatic seizures and regional gliosis, but had not examined other histopathologic elements. Now, we show apoptotic cell death confined to the perilesional cortex and chronic pathologic changes such as ipsilesional ventriculomegaly that are seen in the classic model. We conclude that the rLFPI method is a viable alternative to classic LFPI, and – being a one-stage procedure – has the advantage of shorter experiment turnaround and reduced exposure to anesthetics.

Transcranial Magnetic and Direct Current Stimulation in Children

Promising results in adult neurologic and psychiatric disorders are driving active research into transcranial brain stimulation techniques, particularly transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), in childhood and adolescent syndromes. TMS has realistic utility as an experimental tool tested in a range of pediatric neuropathologies such as perinatal stroke, depression, Tourette syndrome, and autism spectrum disorder (ASD). tDCS has also been tested as a treatment for a number of pediatric neurologic conditions, including ASD, attention-deficit/hyperactivity disorder, epilepsy, and cerebral palsy. Here, we complement recent reviews with an update of published TMS and tDCS results in children, and discuss developmental neuroscience considerations that should inform pediatric transcranial stimulation.

Trajectory of Parvalbumin Cell Impairment and Loss of Cortical Inhibition in Traumatic Brain Injury

Abstract Many neuropsychiatric symptoms that follow traumatic brain injury (TBI), including mood disorders, sleep disturbance, chronic pain, and posttraumatic epilepsy (PTE) are attributable to compromised cortical inhibition. However, the temporal trajectory of cortical inhibition loss and its underlying mechanisms are not known. Using paired‐pulse transcranial magnetic stimulation (ppTMS) and immunohistochemistry, we tracked functional and cellular changes of cortical inhibitory network elements after fluid‐percussion injury (FPI) in rats. ppTMS revealed a progressive loss of cortical inhibition as early as 2 weeks after FPI. This profile paralleled the increasing levels of cortical oxidative stress, which was accompanied by a gradual loss of parvalbumin (PV) immunoreactivity in perilesional cortex. Preceding the PV loss, we identified a degradation of the perineuronal net (PNN)—a specialized extracellular structure enwrapping cortical PV‐positive (PV+) inhibitory interneurons which binds the PV+ cell maintenance factor, Otx2. The trajectory of these impairments underlies the reduced inhibitory tone, which can contribute to posttraumatic neurological conditions, such as PTE. Taken together, our results highlight the use of ppTMS as a biomarker to track the course of cortical inhibitory dysfunction post‐TBI. Moreover, the neuroprotective role of PNNs on PV+ cell function suggests antioxidant treatment or Otx2 enhancement as a promising prophylaxis for post‐TBI symptoms.

Hippocampal immediate early gene transcription in the rat fluid percussion traumatic brain injury model.

Traumatic brain injury (TBI) is one of the leading causes of neurological disability and death in the USA across all age groups, ethnicities, and incomes. In addition to the short-term morbidity and mortality, TBI leads to epilepsy and severe neurocognitive symptoms, both of which are referenced to post-traumatic hippocampal dysfunction, although the mechanisms of such hippocampal dysfunction are incompletely understood. Here, we study the temporal profile of the transcription of three select immediate early gene (IEG) markers of neuronal hyperactivation, plasticity, and injury, c-fos, brain-derived neurotrophic factor (BDNF), and Bax, in the acute period following the epileptogenic lateral fluid percussion injury in a rodent TBI model. We found that lateral fluid percussion injury leads to enhanced expression of the selected IEGs within 24 h of TBI. Specifically, BDNF and c-fos increase maximally 1–6 h after TBI in the ipsilesional hippocampus, whereas Bax increases in the hippocampus bilaterally in this time window. Antagonism of the N-methyl-D-aspartate-type glutamate receptor by MK801 attenuates the increase in BDNF and Bax, which underscores a therapeutic role for N-methyl-D-aspartate-type glutamate receptor antagonism in the acute post-traumatic time period and suggests a value to a hippocampal IEG readout as an outcome after injury or acute therapeutic intervention.

Excess HB-EGF, which promotes VEGF signaling, leads to hydrocephalus.

Heparin binding epidermal growth factor-like growth factor (HB-EGF) is an angiogenic factor mediating radial migration of the developing forebrain, while vascular endothelial growth factor (VEGF) is known to influence rostral migratory stream in rodents. Cell migratory defects have been identified in animal models of hydrocephalus; however, the relationship between HB-EGF and hydrocephalus is unclear. We show that mice overexpressing human HB-EGF with β-galactosidase reporter exhibit an elevated VEGF, localization of β-galactosidase outside the subventricular zone (SVZ), subarachnoid hemorrhage, and ventriculomegaly. In Wistar polycystic kidney rats with hydrocephalus, alteration of migratory trajectory is detected. Furthermore, VEGF infusions into the rats result in ventriculomegaly with an increase of SVZ neuroblast in rostral migratory stream, whereas VEGF ligand inhibition prevents it. Our results support the idea that excess HB-EGF leads to a significant elevation of VEGF and ventricular dilatation. These data suggest a potential pathophysiological mechanism that elevated HB-EGF can elicit VEGF induction and hydrocephalus.

Noninvasive Thermal Evaluation of Ventriculoperitoneal Shunt Patency and Cerebrospinal Fluid Flow Using a Flow Enhancing Device

BACKGROUND While a noninvasive flow determination would be desirable in the diagnosis of cerebrospinal fluid shunt malfunction, existing studies have not yet defined a role for thermal flow detection. OBJECTIVE To evaluate a revised test protocol using a micropumper designed to transiently enhance flow during thermal testing to determine whether thermal detection of flow is associated with progression to shunt revision surgery. METHODS Eighty-two unique tests were performed in 71 shunts. The primary outcome, need for revision within 7 d of testing, was compared with results of micropumper-augmented thermal flow detection. Statistical analysis was based on blind interpretation of test results and raw temperature data recorded during testing. RESULTS The test was sensitive (73%) and specific (68%) in predicting need for revision, with 5.6-fold higher probability of revision when flow was not detected. Negative predictive value in our sample was 94.2%. The probability of not requiring revision increased with increasing total temperature drop. Analysis of various possible thresholds showed that the optimal temperature cutoff may be lower than suggested by the manufacturer (0.125°C vs 0.2°C). CONCLUSION This is the first study to report a strong association between thermal flow evaluation and a clinical impression that a shunt is not malfunctioning. The current recommended threshold may increase the false positive rate unnecessarily, and as clinicians gain experience with the method, they may find value in examining the temperature curves themselves. Multicenter studies are suggested to further define a role for this diagnostic test.

Insights Into Pediatric Brain Stimulation Protocols From Preclinical Research

Abstract Brain stimulation in children requires consideration of the unique biology of the immature brain, and insights into molecular and synaptic distinctions between the developing and mature brain come largely from preclinical experiments in rodents. While the published literature contains few examples of brain stimulation in immature animals, an extensive library of rodent neurodevelopmental research can contribute to the design of pediatric brain stimulation protocols. In particular, preclinical studies identify that GABA-mediated inhibition is reduced and glutamate-mediated excitation is enhanced in the developing brain. These observations, coupled with susceptibility of children to seizures, raise a safety concern in pediatrics. Similarly, capacities for synaptic plasticity differ with age, and warrant consideration in brain stimulation protocol design. Also, beyond differences attributable to age, prevalent neurodevelopmental syndromes, such as epilepsy and autism spectrum disorders, are associated with dysmature brain biology, and thus aspects of brain immaturity should be considered even in some older subjects.