Magnetic resonance imaging with gadolinium DTPA enhancement in patients with acute head injury

Brain injury-induced dysfunction of the blood brain barrier as a risk for dementia

The blood-brain barrier (BBB) is a complex and dynamic physiological interface between brain parenchyma and cerebral vasculature. It is composed of closely interacting cells and signaling molecules that regulate movement of solutes, ions, nutrients, macromolecules, and immune cells into the brain and removal of products of normal and abnormal brain cell metabolism. Dysfunction of multiple components of the BBB occurs in aging, inflammatory diseases, traumatic brain injury (TBI, severe or mild repetitive), and in chronic degenerative dementing disorders for which aging, inflammation, and TBI are considered risk factors. BBB permeability changes after TBI result in leakage of serum proteins, influx of immune cells, perivascular inflammation, as well as impairment of efflux transporter systems and accumulation of aggregation-prone molecules involved in hallmark pathologies of neurodegenerative diseases with dementia. In addition, cerebral vascular dysfunction with persistent alterations in cerebral blood flow and neurovascular coupling contribute to brain ischemia, neuronal degeneration, and synaptic dysfunction. While the idea of TBI as a risk factor for dementia is supported by many shared pathological features, it remains a hypothesis that needs further testing in experimental models and in human studies. The current review focusses on pathological mechanisms shared between TBI and neurodegenerative disorders characterized by accumulation of pathological protein aggregates, such as Alzheimer's disease and chronic traumatic encephalopathy. We discuss critical knowledge gaps in the field that need to be explored to clarify the relationship between TBI and risk for dementia and emphasize the need for longitudinal in vivo studies using imaging and biomarkers of BBB dysfunction in people with single or multiple TBI.

Cyclooxygenase-1 and -2 differentially modulate lipopolysaccharide-induced blood-brain barrier disruption through matrix metalloproteinase activity

Cyclooxygenases (COX) -1 and -2 are key regulators of innate immune responses. We recently demonstrated that the expression of proinflammatory cytokines and chemokines is reduced in COX-1 null ((-/-)), and increased in COX-2(-/-) mice compared with their respective wild type controls during lipopolysaccharide (LPS)-induced innate immune activation. As chemokines are involved in leukocyte recruitment into the inflamed brain, we hypothesized that COX-1 and COX-2 deletion will differentially modulate blood-brain barrier (BBB) permeability in response to LPS. In the present study, using quantitative magnetic resonance imaging, we found that LPS-induced BBB disruption was exacerbated in COX-2(-/-) versus COX-2(+/+) mice. In the hippocampus and cortex of LPS-treated mice, matrix metalloproteinase (MMP)-3 activity was significantly decreased in COX-1(-/-) mice, whereas in COX-2(-/-) mice the activity of both MMP-9 and MMP-3, known to mediate BBB breakdown, was increased. Brain mRNA expression of the leukocyte attracting chemokine Cxcl10, the intercellular interaction molecule Icam-1, the pan-leukocyte marker Cd45 was increased in COX-2(-/-) versus COX-2(+/+) mice, whereas Cxcl10 and Cd45 mRNA expression was decreased in COX-1(-/-) versus COX-1(+/+) mice after LPS. Altogether, these results indicate that COX-2 activity modulates MMP-9 and-3 activities and is necessary to maintain BBB integrity during toll-like receptor 4-dependent innate immune activation.

The acute management of head injury

The management of traumatic brain injury has undergone extensive revision as the results of large collaborative outcome studies have cast doubt on many traditional 'common sense' practices. The primary goal of identifying and treating intracranial hypertension has given way to a focus on secondary brain ischemia, in which cerebral perfusion pressure and oxygen delivery have gained new importance. With the exception of impending herniation, the routine use of hyperventilation and high-dose barbiturates is no longer recommended. Hypertonic saline, given as intermittent boluses, has joined mannitol as an effective means of reducing cerebral edema. Preliminary results from a large multi-center study have cast doubt on the benefit of the broad application of hypothermia in improving outcome in traumatic brain injury.

[Strategies diagnosis of polytraumatized adult patients with coma]

OBJECTIVE

To review the diagnostic strategy of management of multiple trauma patient during the first hours.

DATA SOURCES

Extraction from Pubmed database of French and English articles on the management of multiple trauma patient published for ten years.

DATA SELECTION

The collected articles were reviewed and selected according to their quality and originality. The more recent data were selected.

DATA SYNTHESIS

The first hours of management of multiple trauma patients are a particular challenge. The first dilemma is to drive the patient toward an adequate structure. In case of poor haemodynamic tolerance, the patient will be drive in the nearest hospital. When haemodynamic parameters are restored, multiple trauma patient has to be receive in a high level hospital by a trained medical team with an anesthesiologist, intensivist, neurosurgeon, general surgeon and radiologist. The initial assessment may have two priorities: quality and speed. The total body CT scan is actually the answer to these priorities.

How useful is magnetic resonance imaging in predicting severity and outcome in traumatic brain injury?

Major advances have been made in the ever-expanding field of magnetic resonance imaging and related technologies, such as magnetic resonance spectroscopy, haemodynamic and functional imaging. Although these magnetic resonance modalities are of great research interest, it is still questionable as to how useful these investigations are in the clinical setting. All of these modalities strive to define a few variables that might dominate the heterogeneous but common aetiopathology of traumatic brain injury. Recent studies have found that the use of various magnetic resonance imaging techniques at early and delayed time points can provide useful information with regard to the severity and clinical outcome of patients following traumatic brain injury. These new observations offer opportunities for improved clinical management in such patients.