Stephen Ashwal

Predicting outcomes of traumatic brain injury by imaging modality and injury distribution.

Early prediction of outcomes after traumatic brain injury (TBI) is often difficult. To improve prognostic accuracy soon after trauma, we compared different radiological modalities and anatomical injury distribution in a group of adult TBI patients. The four methods studied were computed tomography (CT), magnetic resonance imaging (MRI) with T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR) imaging, and susceptibility weighted imaging (SWI). The objective of this study was to identify which modality and anatomic model best predict outcome. The patient population consisted of 38 adults admitted between February 2001 and May 2003. Early CT, T2WI, FLAIR, and SWI were obtained for each patient as well as a Glasgow Outcome Score (GOS) between 0.1 and 22 months (mean 9.2 months) after injury. Using a semi-automated computer method, intraparenchymal lesions were traced, measured, and converted to lesion volumes based on slice thickness and pixel size. Lesions were assigned to zones and regions. Outcomes were dichotomized into good (GOS 4-5) and poor (GOS 1-3) outcome groups. Brain injury detected by imaging was analyzed by median total lesion volume, median volume per lesion, and median number of lesions per outcome group. T2WI and FLAIR imaging most consistently discriminated between good and poor outcomes by median total lesion volume, median volume per lesion, and median number of lesions. In addition, T2WI and FLAIR imaging most consistently discriminated between good and poor outcomes by zonal distribution. While SWI rarely discriminated by outcome, it was very sensitive to intraparenchymal injury and its optimal use in evaluating TBI is unclear. SWI and other new imaging modalities should be further studied to fully evaluate their prognostic utility in TBI evaluation.

Animal Models of Perinatal Hypoxic-Ischemic Brain Damage

Animal models are often presumably the first step in determining mechanisms underlying disease, and the approach and effectiveness of therapeutic interventions. Perinatal brain damage, however, evolves over months of gestation, during the rapid maturation of the fetal and newborn brain. Despite marked advances in our understanding of these processes and technologic advances providing an improved window on the timing and duration of injury, neonatal brain injury remains a moving target regarding our ability to mimic its processes in an animal model. Moreover, interfering with normal processes of development as part of a therapeutic intervention may do more harm than good. Hence, controversy continues over which animal model can reflect human disease states. Numerous models have provided information regarding the pathophysiology of brain damage in term and preterm infants. Our challenges consist of identifying infants at greatest risk for permanent injury, identifying the timing of injury, and adapting therapies that provide more benefit than harm. A combination of appropriately suitable animal models to conduct these studies will bring us closer to understanding human perinatal damage and the means to treat it.

Diffusion-weighted imaging improves outcome prediction in pediatric traumatic brain injury.

Diffusion-weighted imaging (DWI) and consequent apparent diffusion coefficient (ADC) maps have been used for lesion detection and as a predictor of outcome in adults with traumatic brain injury (TBI), but few studies have been reported in children. We evaluated the role of DWI and ADC for outcome prediction after pediatric TBI (n=37 TBI; n=10 controls). Fifteen regions of interest (ROIs) were manually drawn on ADC maps that were grouped for analysis into peripheral gray matter, peripheral white matter, deep gray and white matter, and posterior fossa. All ROIs excluded areas that appeared abnormal on T2-weighted images (T2WI). Acute injury severity was measured using the Glasgow Coma Scale (GCS) score, and 6-12-month outcomes were assessed using the Pediatric Cerebral Performance Category Scale (PCPCS) score. Patients were categorized into five groups: (1) controls; (2) all TBI patients; (3) mild/moderate TBI with good outcomes; (4) severe TBI with good outcomes; and (5) severe TBI with poor outcomes. ADC values in the peripheral white matter were significantly reduced in children with severe TBI with poor outcomes (72.8+/-14.4x10(-3) mm2/sec) compared to those with severe TBI and good outcomes (82.5+/-3.8x10(-3) mm2/sec; p<0.05). We also found that the average total brain ADC value alone had the greatest ability to predict outcome and could correctly predict outcome in 84% of cases. Assessment of DWI and ADC values in pediatric TBI is useful in evaluating injury, particularly in brain regions that appear normal on conventional imaging. Early identification of children at high risk for poor outcome may assist in aggressive clinical management of pediatric TBI patients.

Animal models of neonatal stroke.

Neonatal stroke occurs in approximately 1 in 4,000 to 1 in 10,000 newborns, and more than 80% involve the vascular territory supplied by the middle cerebral artery. Neonatal stroke is associated with many acquired and genetic prothrombotic factors, and follow-up studies indicate that as many as two thirds of neonates develop neurologic deficits. In the past two decades unilateral carotid occlusion with 8% hypoxia has been used to study focal and global ischemia in the newborn, and recently a filament model of middle cerebral artery occlusion has been developed. This review describes the results of studies in these two newborn models covering aspects of the injury cascade that occurs after focal ischemia. A likely requirement is that therapeutic efforts be directed less at using thrombolytic therapy and more toward treatment of events associated with reperfusion injury, the inflammatory cascade, and apoptosis. Additional areas of research that have received attention in the past year include inhibition of nitric oxide and free-radical formation, use of iron chelating agents, the potential role of hypoxia-inducible factors and mediators of caspase activity, use of growth factors, hypothermia, and administration of magnesium sulfate.

Temporal and regional evolution of aquaporin-4 expression and magnetic resonance imaging in a rat pup model of neonatal stroke.

Edema formation can be observed using magnetic resonance imaging (MRI) in patients with stroke. Recent studies have shown that aquaporin-4 (AQP4), a water channel, is induced early after stroke and potentially participates in the development of brain edema. We studied whether induction of AQP4 correlated with edema formation in a rat pup filament stroke model using high field (11.7-Tesla) MRI followed by immunohistochemical investigation of AQP4 protein expression. At 24 h, we observed increased T2 values and decreased apparent diffusion coefficients (ADC) within injured cortical and striatal regions that reflected the edema formation. Coincident with these MR changes were significant increases in AQP4 expression on astrocytic end-feet in the border regions of injured tissues. Striatal imaging findings were still present at 72 h with a slow normalization of AQP4 expression in the border regions. At 28 d, AQP4 expression normalized in the border while in this region ADC values increased. We show that induction of AQP4 is increased during the period of active edema formation in the border region without regional correlation with edema. Finally, induction of AQP4 on astrocyte end-feet could participate in tissue preservation after ischemia in the immature rat brain.

Variability in pediatric brain death determination and documentation in southern California.

OBJECTIVES. Because the concept of brain death is difficult to define and to apply, we hypothesized that significant variability exists in pediatric brain death determination and documentation. METHODS. Children (0–18 years of age) for whom death was determined with neurologic criteria between January 2000 and December 2004, in southern California, were included. Medical charts were reviewed for documented performance of 14 specific elements derived from the 1987 brain death guidelines and confirmatory testing. RESULTS. A total of 51.2% of children (142 of 277 children) referred to OneLegacy became organ donors. Care locations varied, including PICUs (68%), adult ICUs (29%), and other (3%). One patient was <7 days, 6 were 7 days to 2 months, 22 were 2 months to 1 year, and 113 were >1 year of age. The number of brain death examinations performed was 0 (4 patients), 2 (122 patients), 3 (14 patients), or 4 (2 patients). Recommended intervals between examinations were followed for 18% of patients >1 year of age and for no younger patients. A mean of only 5.5 of 14 examination elements were completed by neurologists and pediatric intensivists and 5.8 by neurosurgeons. No apnea testing was recorded in 60% of cases, and inadequate Paco2 increase occurred in more than one half. Cerebral blood flow determination was performed as a confirmatory test 74% of the time (83 of 112 cases), compared with 26% (29 of 112 cases) for electroencephalography alone. CONCLUSIONS. Children suffering brain death are cared for in various locations by a diverse group of specialists. Clinical practice varies greatly from established guidelines, and documentation is incomplete for most patients. Physicians rely on cerebral blood flow measurements more than electroencephalography for confirmatory testing. Codifying clinical and testing criteria into a checklist could lend uniformity and enhance the quality and rigor of this crucial determination.

Magnetic resonance imaging in cerebral ischemia: Focus on neonates

Magnetic resonance imaging (MRI) has dramatically changed our ability to diagnose and treat stroke as well as follow its evolution and response to treatment. Early stroke and ischemia can be visualized using diffusion-weighted imaging (DWI), which utilizes proton diffusion within tissues as a reporter for evolving neuropathology that reflects cytotoxic edema, particularly during the first several days after injury. Historically, T2-weighted imaging (T2WI) has been used for evaluation of vasogenic edema and also is a reliable indicator of injured tissue late after injury. While visual analysis of MR data can provide information about the evolution of injury, quantitative analyses allow definitive and objective evaluations of injury size and location and the effectiveness of novel therapeutic strategies. We review the clinical basis of imaging for stroke and ischemia diagnosis and the methods for post-processing of MR data that could provide novel insights into the evolution and pathophysiology of stroke in the newborn.

Relationship Between Opioid Therapy, Tissue-Damaging Procedures, and Brain Metabolites as Measured by Proton MRS in Asphyxiated Term Neonates

To examine the effects of opioid and tissue-damaging procedures (TDPs) [i.e. procedures performed in the neonatal intensive care unit (NICU) known to result in pain, stress, and tissue damage] on brain metabolites, we reviewed the medical records of 28 asphyxiated term neonates (eight opioid-treated, 20 non–opioid treated) who had undergone magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (MRS) within the first month of life as well as eight newborns with no clinical findings of asphyxial injury. We found that lower creatine (Cr), myoinositol (Ins), and N-acetylaspartate (NAA)/choline (Cho) (p ≤ 0.03) and higher Cho/Cr and glutamate/glutamine (Glx) Cr (p ≤ 0.02) correlated with increased TDP incidence in the first 2 d of life (DOL). We also found that occipital gray matter (OGM) NAA/Cr was decreased (p = 0.03) and lactate (Lac) was present in a significantly higher amount (40%; p = 0.03) in non–opioid-treated neonates compared with opioid-treated neonates. Compared with controls, untreated neonates showed larger changes in more metabolites in basal ganglia (BG), thalami (TH), and OGM with greater significance than treated neonates. Our data suggest that TDPs affect spectral metabolites and that opioids do not cause harm in asphyxiated term neonates exposed to repetitive TDPs in the first 2–4 DOL and may provide a degree of neuroprotection.

Developmental Outcomes After Pediatric Heart Transplantation

BACKGROUNDnPediatric heart transplantation has now been successfully performed for more than 20 years. As survival rates have improved, more attention is now focused on long-term outcomes.nnnMETHODSnThis report reviews the literature on developmental outcomes after pediatric heart transplantation.nnnRESULTSnPediatric patients undergoing heart transplantation generally can be expected to have developmental outcomes in the low-normal range, consistent with outcomes seen in other children with complex congenital heart disease requiring surgical intervention. When these children reach school age, or return to school, most can be expected to function reasonably well in mainstream school settings. A significant minority will require additional educational assistance. Approximately 10% will have significant neurologic impairment. In school, particular attention should be paid to evaluating the child for deficits in arithmetic and verbal skills. Performance may be better than predicted from IQ testing. Behavioral issues are common, with depression, concerns about social competence, and attention difficulties most frequently endorsed. This may pre-date transplantation in those who undergo transplantation during childhood and may improve with time. Parents more often report problem behaviors than teachers. Family resources and family coping skills are also strongly correlated with the childs emotions and coping skills.nnnCONCLUSIONnThe pediatric heart transplant recipients ability to transition from childhood into a happy and productive adult life can be significantly affected by his or her cognitive abilities, learning experiences, sense of self, and emotions. Attention to these factors is an important part of caring for these children.

Albumin reduces blood-brain barrier permeability but does not alter infarct size in a rat model of neonatal stroke.

Human serum albumin therapy confers neurobehavioral and histopathologic neuroprotection in adult stroke models. We investigated whether albumin might also be neuroprotective in ischemic brain injury using a transient filament middle cerebral artery occlusion (tfMCAO) model in 10-d-old rat pups treated with 0.25% albumin or saline 1 h after reperfusion. We performed serial neurobehavioral and magnetic resonance imaging (MRI) assessments immediately after tfMCAO (day 0) and on 1, 3, 7, 14, and 28 d. IgG staining to assess blood-brain barrier (BBB) integrity and standard histology was obtained on 1, 3, and 28 d. Hemispheric infarct volumes from MRI were similar in saline and albumin groups (0 h: 39% and 44%; d 1: 46% and 55%; and d 28:10% and 24%) as were neurobehavioral assessments. IgG staining at 3 d post-ischemia showed loss of BBB integrity that was significantly reduced after albumin. Elevated T2 values suggesting vasogenic edema was seen in albumin compared with saline-treated animals, as was increased water mobility (i.e. increased apparent diffusion coefficient (ADC) reflecting cytotoxic edema. The reasons why albumin was not neuroprotective in neonatal stroke compared with adults remain uncertain. Effective strategies in adult models need to be reassessed in the neonate.