Cerebral perfusion pressure and intracranial pressure in relation to neuropsychological outcome

Dapagliflozin improves diabetic cognitive impairment via indirectly modulating the mitochondria homeostasis of hippocampus in diabetic mice

Cognitive impairment is increasingly recognized as an important comorbidity of diabetes progression; however, the underlying molecular mechanism is unclear. Dapagliflozin, an inhibitor of sodium-glucose co-transporter 2 (SGLT2), has shown promising effects against diabetes in rodent experiments and human clinical assays. This study aimed to determine the underlying mechanism and examine the effect of dapagliflozin on diabetic cognitive impairment. To create an in vivo model of diabetic cognitive impairment, streptozotocin (STZ)-induced diabetic mice were used. Dapagliflozin was administered to mice for 8 weeks. The context fear condition and Morris water maze test was used to evaluate mice's behavioral change. Western blotting was used to evaluate protein expression. Hematoxylin and eosin (HE) and Nissl staining were applied to monitor morphological and structural changes. Congo red staining was performed to identify the formation of senile plaques. Mitochondria morphology was examined using a transmission electron microscope, and blood flow in the mouse cerebral cortex was measured using a laser Doppler imaging assay. Comparison to the diabetes mellitus (DM) group, the dapagliflozin group had lower glucose levels. Behavioral studies have shown that dapagliflozin can restore memory deficits in diabetic mice. The murky cell membrane edges and Nissl bodies more difficult to identify in the DM group were revealed by HE and Nissl staining, which were both improved by dapagliflozin treatment. Dapagliflozin inhibited the progression of Aβ generation and the reduced cerebral blood flow in the DM group was rescued. After dapagliflozin treatment, damaged mitochondria and lack of SGLT2 in the hippocampus and cortex of diabetic mice were repaired. Diabetes-induced cognitive dysfunction was attenuated by dapagliflozin and the effect was indirect rather than direct.

Verbal fluency in three Spanish-English bilingual speakers with TBI

This study investigated differences between healthy bilingual participants and bilingual participants with traumatic brain injury (TBI) on verbal fluency tasks. The performance of three Spanish-English bilingual speakers with traumatic brain injury was compared to the performance of 30 neurotypical bilingual speakers on tasks of category and letter verbal fluency in English and Spanish. Responses were analyzed for total number of correct productions, differences in correct productions between languages, average cluster size, total number of switches, and rates of language choice errors. The data were analyzed using predicted scores from regression equations based on neurotypical data and modified t-tests. Analyses revealed significantly lower total output than predicted by the regression equations for both task types and in both languages for one TBI participant. The same participant demonstrated significantly lower total number of switches than the neurotypical group. Two participants demonstrated higher rates of language choice errors than the neurotypical group. There were no significant differences between TBI participants and the neurotypical group for average cluster size. There were no significant differences between predicted and obtained values for differences between English and Spanish total number correct in each task type. Results are discussed in the context of individual cognitive and linguistic profiles of the TBI participants.

Low brain oxygenation and differences in neuropsychological outcomes following severe pediatric TBI

PURPOSE

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in children. Preventing secondary injury by controlling physiological parameters (e.g. intracranial pressure [ICP], cerebral perfusion pressure [CPP] and brain tissue oxygen [PbtO2]) has a potential to improve outcome. Low PbtO2 is independently associated with poor clinical outcomes in both adults and children. However, no studies have investigated associations between low PbtO2 and neuropsychological and behavioural outcomes following severe pediatric TBI (pTBI).

METHODS

We used a quasi-experimental case-control design to investigate these relationships. A sample of 11 TBI patients with a Glasgow Coma Scale score ≤8 who had PbtO2 and ICP monitoring at the Red Cross War Memorial Children's Hospital underwent neuropsychological evaluation ≥1 year post-injury. Their performance was compared to that of 11 demographically matched healthy controls. We then assigned each TBI participant into one of two subgroups, (1) children who had experienced at least one episode of PbtO2 ≤ 10 mmHg or (2) children for whom PbtO2 > 10 mmHg throughout the monitoring period, and compared their results on neuropsychological evaluation.

RESULTS

TBI participants performed significantly more poorly than controls in several cognitive domains (IQ, attention, visual memory, executive functions and expressive language) and behavioural (e.g. externalizing behaviour) domains. The PbtO2 ≤ 10 mmHg group performed significantly worse than the PbtO2 > 10 mmHg group in several cognitive domains (IQ, attention, verbal memory, executive functions and expressive language), but not on behavioural measures.

CONCLUSION

Results demonstrate that low PbtO2 may be prognostic of not only mortality but also neuropsychological outcomes.

Traumatic brain injury and cognition

Traumatic brain injury (TBI) is a major cause of death and disability, and therefore an important health and socioeconomic problem for our society. Individuals surviving from a moderate to severe TBI frequently suffer from long-lasting cognitive deficits. Such deficits include different aspects of cognition such as memory, attention, executive functions, and awareness of their deficits. This chapter presents a review of the main neuropsychological and neuroimaging studies of patients with TBI. These studies found that patients evolve differently according to the severity of the injury, the mechanism causing the injury, and the lesion location. Further research is necessary to develop rehabilitation methods that enhance brain plasticity and recovery after TBI. In this chapter, we summarize current knowledge and controversies, focusing on cognitive sequelae after TBI. Recommendations from the Common Data Elements are provided, with an emphasis on diagnosis, outcome measures, and studies organization to make data more comparable across studies. Final considerations on neuroimaging advances, rehabilitation approaches, and genetics are described in the final section of the chapter.

Component analysis of verbal fluency performance in younger participants with moderate-to-severe traumatic brain injury

PRIMARY OBJECTIVE

To investigate phonemic and semantic verbal fluency performance in a group of young adult participants with and without traumatic brain injury.

RESEARCH DESIGN

Group comparison.

METHODS AND PROCEDURES

Twenty-five participants with moderate-to-severe TBI and 25 participants with no brain damage (NBD) were given phonemic and semantic verbal fluency tasks. Responses were analysed quantitatively and qualitatively.

MAIN OUTCOMES AND RESULTS

Young participants with moderate-to-severe TBI generated significantly fewer total correct words and sub-categories for both fluency conditions when compared to controls. The total number of correct words generated on the phonemic condition and for the semantic category of animals was positively correlated with the number of category switches produced during the task.

CONCLUSIONS

While young participants with moderate-to-severe TBI produced fewer total correct words on both verbal fluency conditions in comparison to controls, these differences were greater on the phonemic condition. Participants with moderate-to-severe TBI switched less frequently on both fluency tasks and produced smaller cluster sizes only on the phonemic task in comparison to controls. These results are in contrast with previous investigations that have observed greater age-related declines on semantic tasks when compared to phonemic tasks.

Timing of intracranial hypertension following severe traumatic brain injury

BACKGROUND

We asked whether continuous intracranial pressure (ICP) monitoring data could provide objective measures of the degree and timing of intracranial hypertension (ICH) in the first week of neurotrauma critical care and whether such data could be linked to outcome.

METHODS

We enrolled adult (>17 years old) patients admitted to our Level I trauma center within 6 h of severe TBI. ICP data were automatically captured and ICP 5-minute means were grouped into 12-hour time periods from admission (hour 0) to >7 days (hour 180). Means, maximum, percent time (% time), and pressure-times-time dose (PTD, mmHg h) of ICP >20 mmHg and >30 mmHg were calculated for each time period.

RESULTS

From 2008 to 2010, we enrolled 191 patients. Only 2.1% had no episodes of ICH. The timing of maximum PTD20 was relatively equally distributed across the 15 time periods. Median ICP, PTD20, %time20, and %time30 were all significantly higher in the 84-180 h time period than the 0-84 h time period. Stratified by functional outcome, those with poor functional outcome had significantly more ICH in hours 84-180. Multivariate analysis revealed that, after 84 h of monitoring, every 5% increase in PTD20 was independently associated with 21% higher odds of having a poor functional outcome (adjusted odds ratio = 1.21, 95% CI 1.02-1.42, p = 0.03).

CONCLUSIONS

Although early elevations in ICP occur, ICPs are the highest later in the hospital course than previously understood, and temporal patterns of ICP elevation are associated with functional outcome. Understanding this temporal nature of secondary insults has significant implications for management.

Neuropsychologic function three to six months following admission to the PICU with meningoencephalitis, sepsis, and other disorders: a prospective study of school-aged children

OBJECTIVE

To assess short-term neuropsychological function and academic performance in school children following admission to intensive care and to explore the role of critical neurologic and systemic infection.

DESIGN

A prospective observational case-control study.

SETTING

Two PICUs.

SUBJECTS

A consecutive sample of 88 children aged 5-16 years (median age=10.00, interquartile range=6.00-13.00) who were admitted to intensive care between 2007 and 2010 with meningoencephalitis, septic illness, or other critical illnesses. They were assessed 3 to 6 months following discharge, and their performance was compared with that of 100 healthy controls. Patients were without prior neurologic or neurodevelopmental disorder.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Data encompassing demographic and critical illness details were obtained, and children were assessed using tests of intellectual function, memory, and attention. Questionnaires addressing academic performance were returned by teachers. After adjusting for covariates, the children admitted to PICUs significantly underperformed on neuropsychological measures in comparison to healthy controls (p<0.02). Teachers deemed more children admitted to PICUs than controls as performing educationally worse and having problems with school work (ps=0.001), as well as performing below average on aspects of executive function and attention (ps<0.04). Analysis of the effect of illness type on outcome revealed that aspects of neuropsychological function, such as memory function, and teacher-rated academic performance were most reduced in children with meningoencephalitis and septic illness. In the PICU group, multivariable linear regression revealed that worse performance on a composite score of neuropsychologic impairment was more prevalent when children were younger, from a lower social class, and had experienced seizures during their admission (ps<0.02).

CONCLUSIONS

Admission to intensive care is followed by deficits in neuropsychologic performance and educational difficulties, with more severe difficulties noted following meningoencephalitis and septic illness. These results highlight the importance of future studies on cognition and educational outcome incorporating type of illness as a moderating factor.

Early prediction of language impairment following traumatic brain injury

PRIMARY OBJECTIVE

This study investigated which factors collected early in the acute care setting (age, education, cerebral imaging, Glasgow Coma Scale score) would predict initial impairments of language comprehension and expression in patients with traumatic brain injury (TBI) of all severity.

METHODS AND PROCEDURES

Results of language tests carried out during the patients' stay in an acute tertiary trauma centre were obtained. These tests measured performance in the areas of confrontation naming, auditory comprehension, semantic and letter category naming and comprehension of verbal absurdities. Data for the predictive variables were gathered by retrospective chart review. Stepwise multiple linear regressions were carried out on the predictive variables.

MAIN OUTCOMES AND RESULTS

Education and TBI severity as measured with the GCS score were the most significant factors predicting language deficits in the acute care setting.

CONCLUSIONS

These findings will serve to guide health care professionals in predicting prognosis for cognitive-communication deficits post-TBI and in planning for appropriate resources in speech-language pathology to meet these patients' needs.

Evaluation of optimal cerebral perfusion pressure in severe traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability. In the 2000 guidelines, one of the suggestions for TBI treatment was to maintain cerebral perfusion pressure (CPP) < or = 70 mmHg. But in the 2003 guidelines, the suggestion was changed to < or = 60 mmHg. There have been some discrepancies of opinions about this recommendation in recent publications. In this study, we retrospectively reviewed 305 severe TBI (STBI) patients with Glasgow Coma Scales (GCS) < or = 8 between January 1, 2002 and March 31, 2003. The study group was stratified according to use or nonuse of intracranial pressure (ICP) monitoring, ICP levels, ages, and GCS levels in order to test the correlation between CCP and the prognosis. The patients < 50-year-old, with higher GCS level, with ICP monitoring, and with ICP levels < 20 mmHg had lower mortality rates and better prognosis (GOS) (p < 0.05 or 0.001). The patients in the GCS 3-5 subgroup had a significantly lower mortality and better prognosis if the CPP value was maintained higher than 70 mmHg (p < 0.05) The optimal CPP maintained < or = 60 mmHg did not fit in all STBI patients. Our study concludes that it is critical to maintain CPP substantially higher in lower GCS level patients.

Intensive care unit variables and outcome after pediatric traumatic brain injury: a retrospective study of survivors

OBJECTIVE

Traumatic brain injury is a leading cause of death and disability in children. Hypotension has been associated with poor survival and outcome in children after traumatic brain injury, but the effect of acute hypertension is less certain. The objective was to obtain acute physiologic variables during the early hospitalization period in a cohort of children prospectively enrolled in another study.

DESIGN

Retrospective chart reviews.

SETTING

University-affiliated pediatric rehabilitation center.

PATIENTS

Fifty-seven survivors, 5-17 yrs of age, admitted for rehabilitation between 1992 and 1995 after sustaining a traumatic brain injury.

INTERVENTIONS

Standard of care.

MEASUREMENTS AND MAIN RESULTS

Outcomes were assessed at 1 yr postinjury through cognitive testing of the child and parent interview of the child's global functional skills. Cognitive outcome was measured using the Performance IQ from the Wechsler Intelligence Scale for Children, Third Edition. Overall functional outcome was assessed using the Disability Rating Scale.

CONCLUSIONS

This study suggests that early markers of secondary injury after moderate to severe traumatic brain injury in children may be predictive of long-term outcome. This study reinforces the need for longer term, systematic, and more precise measurements of outcomes in children with traumatic brain injury and prospective studies to examine the predictive value of acute management variables on multiple types of outcomes after traumatic brain injury in children.

Prediction of raised intracranial pressure complicating severe traumatic brain injury in children: implications for trial design

OBJECTIVES

To describe current patterns of management of raised intracranial pressure (ICP) in traumatic brain injury relevant to clinician buy-in to possible randomized controlled trials of treatments of raised ICP. To examine the feasibility of early identification of children at sufficient risk of developing raised ICP to permit a uniform approach between centers to the initiation of ICP monitoring. This would permit quantification of ICP elevation and enrollment as appropriate to randomized controlled trials of raised ICP interventions.

DESIGN

Logistic regression modeling of death before pediatric intensive care unit discharge and decision tree and logistic regression of development of raised ICP through analysis of a prospectively collected, standardized, national data set.

SETTING

Pediatric intensive care units in the United Kingdom and Eire.

PATIENTS

Patients were 501 children <16 yrs of age primarily admitted to intensive care unit for management of traumatic brain injury in the United Kingdom and Eire between February 2001 and August 2003.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The data analyzed included demographic, acute physiologic, and cranial imaging variables. Death was associated with both raised ICP and the nonmeasurement of ICP. In a subset of 199 patients, an empirically derived decision rule predicted the development of raised ICP at any point during ICU admission with sensitivity of 73% and specificity of 74% (positive predictive value 82% and negative predictive value 63%). Logistic regression modeling performed comparably. The decision rule also predicted raised ICP in 20% of children not undergoing ICP monitoring.

CONCLUSIONS

Simple models based on early clinical data may predict the development of raised ICP sufficiently well to encourage a consistent approach between centers to initiation of ICP monitoring. We estimate studies designed to detect reductions in ICU mortality will require >320 children per arm, although this figure may be higher if more conservative assumptions are made.

A Meta-Analytic Review of Verbal Fluency Performance in Patients With Traumatic Brain Injury

A meta-analysis of 30 studies with 1,269 participants was conducted to investigate the sensitivity of tests of verbal fluency to the presence of traumatic brain injury (TBI). As has been found for patients with focal frontal lobe injuries (but not for patients with focal temporal lobe lesions), TBI patients were comparably impaired on tests of phonemic and semantic fluency. The phonemic fluency deficit could not be accounted for by patients' level of premorbid or current verbal IQ and was also substantially (although not significantly) in excess of the deficit on a measure of psychomotor speed. Phonemic fluency was also significantly more sensitive to the presence of TBI than was the Wisconsin Card Sorting Test.

Influence of Extraneurological Insults on Ventricular Enlargement and Neuropsychological Functioning after Moderate and Severe Traumatic Brain Injury

Extraneurological insults secondary to TBI such as hypotension or hypoxia have been associated with mortality and morbidity. The purpose of this study was to investigate the influence of systemic complications on both neuropsychological outcome and cerebral atrophy. Fifty-seven patients selected from 122 consecutive admissions were studied. Data on the type and severity of injury as well as other systemic insults were collected prior to and during the first 3 days of hospitalization. These data included the presence or absence of a hypoxic episode during the pre-hospital period, the presence and degree of hypoxia, hypercapnia, anemia, hypotension and intracranial hypertension, pupillary reactivity, Glasgow Coma Scale score and coma duration. From the last control CT scan image, performed 6 months post-injury, four different indexes of ventricular dilatation were calculated. Neuropsychological assessment at 6 months included tests of verbal and visual memory, visuoconstructive functions, fine motor speed, and frontal lobe functions. Our results showed that hypoxia and hypotension were related to neuropsychological outcome and long-term ventricular enlargement. Hypoxic episodes prior to hospitalization were related to third ventricle dilatation and to adverse neurological and cognitive outcomes, especially to attention, motor speed, mental flexibility, fluency and verbal memory impairments, suggesting fronto-striatal and hippocampal dysfunction. We conclude that the effect of extraneurological insults on brain structure and function may be as important as the severity of the primary injury.

Extrapolation to zero-flow pressure in cerebral arteries to estimate intracranial pressure

BACKGROUND

Cerebral perfusion pressure (CPP) is commonly calculated from the difference between arterial blood pressure (AP) and intracranial pressure (ICP). ICP can be considered the effective downstream pressure of the cerebral circulation. Consequently, cerebral circulatory arrest would occur when AP equals ICP. Estimation of AP for zero-flow pressure (ZFP) may thus allow estimation of ICP. We estimated ZFP from cerebral pressure-flow velocity relationships so that ICP could be measured by transcranial Doppler sonography.

METHODS

We studied 20 mechanically ventilated patients with severe head injury, in whom ICP was monitored by epidural pressure transducers. AP was measured with a radial artery cannula. Blood flow velocity in the middle cerebral artery (V(MCA)) ipsilateral to the site of ICP measurement was measured with a 2 MHz transcranial Doppler probe. All data were recorded by a microcomputer from analogue-digital converters. ZFP was extrapolated by regression analysis of AP-V(MCA) plots and compared with simultaneous measurements of ICP.

RESULTS

ZFP estimated from AP-V(MCA) plots was linearly related to ICP over a wide range of values (r=0.93). There was no systematic difference between ZFP and ICP. Limit of agreement (2 SD) was 15.2 mm Hg. Short-term variations in ICP were closely followed by changes in ZFP.

CONCLUSION

Extrapolation of cerebral ZFP from instantaneous AP-V(MCA) relationships enables detection of severely elevated ICP and may be a useful and less invasive method for CPP monitoring than other methods.

Early predictors of mortality and morbidity after severe closed head injury

Mortality and morbidity of 158 patients with severe head injury were studied in relation to age, and early (24-h) clinical and computed tomography data. For comparison of outcome data in survivors, a group of 32 patients with traumatic injuries to parts of the body other than the head was used as controls. Within the head-injured group, the mortality rate was 51%. Logistic regression analyses combined 13 out of 16 predictors into a model with an accuracy of 93%, a sensitivity of 90%, and a specificity of 95%. These include age, Glasgow Coma Scale (GCS) score, pupillary reactivity, blood pressure, intracranial pressure, blood glucose, platelet count, body temperature, cerebral lactate, and subdural, intracranial, subarachnoid, and ventricular hemorrhage. At 6 months postinjury, head-injury survivors and trauma controls were evaluated with the Glasgow Outcome Scale (GOS), a neuropsychological test battery and the Sickness Impact Profile (SIP). Head-injury survivors had a higher proportion of disabilities and neuropsychological dysfunctions than trauma controls. They also report more quality of life-related functional limitations on the SIP scales for mobility, intellectual behavior, communication, home management, eating, and work. Linear regression analysis resulted in age being the only important predictor of outcome on the GOS, the GCS score being the best predictor of neuropsychological functioning, and pupillary reactivity being the most predictive for self-reported quality of life as measured by SIP. Those factors important for predicting mortality (clinical variables such as ICP or blood glucose level, and CT observations) failed to show any significant relationship with morbidity.