Charu Venkatesan

Chronic upregulation of activated microglia immunoreactive for galectin-3/Mac-2 and nerve growth factor following diffuse axonal injury

BackgroundDiffuse axonal injury in patients with traumatic brain injury (TBI) can be associated with morbidity ranging from cognitive difficulties to coma. Magnetic resonance imaging scans now allow early detection of axonal injury following TBI, and have linked cognitive disability in these patients to white matter signal changes. However, little is known about the pathophysiology of this white matter injury, and the role of microglial activation in this process. It is increasingly recognized that microglia constitute a heterogeneous population with diverse roles following injury. In the present studies, we tested the hypothesis that following diffuse axonal injury involving the corpus callosum, there is upregulation of a subpopulation of microglia that express the lectin galectin-3/Mac-2 and are involved in myelin phagocytosis.MethodsAdult mice were subject to midline closed skull injury or sham operation and were sacrificed 1, 8, 14 or 28 days later. Immunohistochemistry and immunofluorescence techniques were used to analyze patterns of labelling within the corpus callosum qualitatively and quantitatively.ResultsActivated microglia immunoreactive for galectin-3/Mac-2 were most abundant 1 day following injury. Their levels were attenuated at later time points after TBI but still were significantly elevated compared to sham animals. Furthermore, the majority of galectin-3/Mac-2+ microglia were immunoreactive for nerve growth factor in both sham and injured animals.ConclusionsOur results suggest that galectin-3/Mac-2+ microglia play an important role in the pathogenesis of diffuse axonal injury both acutely and chronically and that they mediate their effects, at least in part by releasing nerve growth factor.

KCNQ2 encephalopathy: Features, mutational hot spots, and ezogabine treatment of 11 patients

Objective: To advance the understanding of KCNQ2 encephalopathy genotype–phenotype relationships and to begin to assess the potential of selective KCNQ channel openers as targeted treatments. Methods: We retrospectively studied 23 patients with KCNQ2 encephalopathy, including 11 treated with ezogabine (EZO). We analyzed the genotype–phenotype relationships in these and 70 previously described patients. Results: The mean seizure onset age was 1.8 ± 1.6 (SD) days. Of the 20 EEGs obtained within a week of birth, 11 showed burst suppression. When new seizure types appeared in infancy (15 patients), the most common were epileptic spasms (n = 8). At last follow-up, seizures persisted in 9 patients. Development was delayed in all, severely in 14. The KCNQ2 variants identified introduced amino acid missense changes or, in one instance, a single residue deletion. They were clustered in 4 protein subdomains predicted to poison tetrameric channel functions. EZO use (assessed by the treating physicians and parents) was associated with improvement in seizures and/or development in 3 of the 4 treated before 6 months of age, and 2 of the 7 treated later; no serious side effects were observed. Conclusions: KCNQ2 variants cause neonatal-onset epileptic encephalopathy of widely varying severity. Pathogenic variants in epileptic encephalopathy are clustered in “hot spots” known to be critical for channel activity. For variants causing KCNQ2 channel loss of function, EZO appeared well tolerated and potentially beneficial against refractory seizures when started early. Larger, prospective studies are needed to enable better definition of prognostic categories and more robust testing of novel interventions. Classification of evidence: This study provides Class IV evidence that EZO is effective for refractory seizures in patients with epilepsy due to KCNQ2 encephalopathy.

Pediatric Endocarditis and Stroke: A Single Center Retrospective Review of Seven Cases

The acute management of strokes in children with infective endocarditis is limited by the paucity of published data on their clinical course and outcomes. Our retrospective study at an urban tertiary-care academic center characterized the clinical course of seven pediatric patients with endocarditis and subsequent cerebral infarcts. Among 115 patients with endocarditis, a stroke occurred in seven. Four patients manifested congenital heart disease. In six patients, the stroke occurred in the distribution of the middle cerebral artery, with no preference for the left or right hemisphere. The most common presenting sign was focal weakness. Three patients manifested mycotic aneurysms, all of which were successfully repaired. Two patients received aspirin therapy, with no adverse effects. All patients survived, but neurologic recovery was variable. The two youngest patients (aged 3 and 14 weeks) demonstrated the longest periods of hospitalization, with the most severe neurologic impairment. These findings suggest that children may have better outcomes than adults after a stroke secondary to bacterial endocarditis. Routine surveillance for mycotic aneurysms in patients with new neurologic deficits, and the use of aspirin, should be considered in the medical management.

ALBUMIN CAUSES INCREASED MYOSIN LIGHT CHAIN KINASE EXPRESSION IN ASTROCYTES VIA P38 MITOGEN ACTIVATED PROTEIN KINASE

Myosin light chain kinase (MLCK) plays an important role in the reorganization of the cytoskeleton, leading to disruption of vascular barrier integrity in multiple organs, including the blood–brain barrier (BBB), after traumatic brain injury (TBI). MLCK has been linked to transforming growth factor (TGF) and rho kinase signaling pathways, but the mechanisms regulating MLCK expression following TBI are not well understood. Albumin leaks into the brain parenchyma following TBI, activates glia, and has been linked to TGF‐β receptor signaling. We investigated the role of albumin in the increase of MLCK in astrocytes and the signaling pathways involved in this increase. After midline closed‐skull TBI in mice, there was a significant increase in MLCK‐immunoreactive (IR) cells and albumin extravasation, which was prevented by treatment with the MLCK inhibitor ML‐7. Using immunohistochemical methods, we identified the MLCK‐IR cells as astrocytes. In primary astrocytes, exposure to albumin increased both isoforms of MLCK, 130 and 210. Inhibition of the TGF‐β receptor partially prevented the albumin‐induced increase in both isoforms, which was not prevented by inhibition of smad3. Inhibition of p38 MAPK, but not ERK, JNK, or rho kinase, also prevented this increase. These results are further evidence of a role of MLCK in the mechanisms of BBB compromise following TBI and identify astrocytes as a cell type, in addition to endothelium in the BBB, that expresses MLCK. These findings implicate albumin, acting through p38 MAPK, in a novel mechanism by which activation of MLCK following TBI may lead to compromise of the BBB.

Early‐life epileptic encephalopathy secondary to SZT2 pathogenic recessive variants

Advances in genetic testing have led to the identification of increasing numbers of novel gene mutations that underlie infantile-onset epileptic encephalopathies. Recently, a mutagenesis screen identified a novel gene, SZT2, with no known protein function that has been linked to epileptogenesis in mice. Thus far, two clinical reports have identified children with different recessive mutations in SZT2 and varying clinical phenotypes. One case report described patients with epileptic encephalopathy and the other noted patients with cognitive deficiencies, but normal MRI and no epilepsy. This case report identifies novel mutations (a compound heterozygous frameshift and a nonsense variant) in the SZT2 gene with distinct clinical and radiographic findings relative to those previously reported. Our patient presented with intractable epilepsy at 2 months of age. Seizures were refractory to numerous antiepileptic medications and the patient finally achieved seizure cessation at age 3 years with a combination of divalproex and lamotrigine. Our patient had similar facial dysmorphisms (macrocephaly, high forehead, and down-slanted palpebral fissures) to a previous case with truncating mutation. While developmental delay and cognitive deficiencies were present, our case had unique MRI findings suggesting migrational abnormalities not previously reported in other cases.

A treatable metabolic cause of encephalopathy: Cobalamin C deficiency in an 8-year-old male

Neurologic regression in a previously healthy child may be caused by metabolic or neurodegenerative disorders, many of which have no definitive treatment. We report a case of a previously healthy 8-year-old boy who presented with a month-long history of waxing and waning encephalopathy and acute regression, followed by seizures. Evaluation for a metabolic disorder revealed methylmalonic acidemia and hyperhomocysteinemia of the cobalamin C type due to a single, presumed homozygous pathogenic c.394 C>T mutation in the MMACHC gene. With the appropriate diet restrictions and vitamin replacement, he improved significantly and returned to his premorbid level of behavior. This case illustrates an unusual presentation of a treatable metabolic disorder and highlights the need to consider cobalamin defects in the differential diagnosis of healthy children with neurologic regression.

Epilepsy Following Neonatal Seizures Secondary to Hemorrhagic Stroke in Term Neonates

Intracranial hemorrhage accounts for about 50% of all pediatric stroke. Studies of term infants with intracranial hemorrhage have shown favorable motor and cognitive outcome. The goal of this study was to examine the risk of developing epilepsy in full-term infants with intracranial hemorrhage. A retrospective study was performed of term neonates (greater than or equal to 37 weeks gestation) with intracranial hemorrhage and confirmed seizures. Fifteen patients with intracranial hemorrhage and neonatal seizures were identified. Four patients did not have follow-up information beyond the neonatal period (1 death, 3 lost to follow-up after initial clinic visit). The average follow-up period for the remaining 11 patients was approximately 22 months. Ten out of the 11 patients (91%) who were followed were seizure-free and off antiepileptic medications. One patient required a ventriculoperitoneal shunt and subsequently developed infantile spasms. The authors found that overall outcome was favorable with respect to development of epilepsy.

Case Report: Intravenous and Oral Pyridoxine Trial for Diagnosis of Pyridoxine-Dependent Epilepsy

Pyridoxine-dependent epilepsy is a rare, autosomal recessive, treatable cause of neonatal seizures. Genetic testing can confirm mutations in the ALDH7A1 gene, which encodes antiquitin. To avoid delays in initiating treatment while awaiting confirmatory genetic testing, it is recommended that all neonates with unexplained seizures should receive trial of intravenous (IV) pyridoxine to assess for responsiveness. However, oral pyridoxine is not commonly continued in the absence of the typical EEG changes. Two cases are presented that highlight the potential inadequacy of this single-step approach. One neonate ultimately diagnosed with pyridoxine-dependent seizures had no EEG changes after administration of IV pyridoxine. In contrast, another neonate who did not have this diagnosis had profound EEG changes after pyridoxine administration. We present 2 cases that highlight the difficulties in using initial EEG response to IV pyridoxine in establishing a diagnosis of pyridoxine-dependent seizures in the neonate. Given the availability of biochemical markers and gene testing, we suggest that oral pyridoxine treatment should be continued until biochemical and/or genetic testing has confirmed the presence or absence of pyridoxine-dependent epilepsy.