Inflammation of the choroid plexus and ependymal layer of the ventricle following intraventricular hemorrhage.

Intraventricular hemorrhage (IVH), which afflicts thousands of people of all ages every year, frequently results in the development of communicating hydrocephalus. Classically, IVH-induced hydrocephalus has been attributed to reduced resorption of cerebrospinal fluid (CSF) due to dysfunction of arachnoid granulations, but this explanation may be incomplete. We hypothesized that IVH would cause inflammation of the choroid plexus and of the ependymal lining of the ventricles, resulting in dysfunction of these barrier cells. Barrier dysfunction, in turn, would be expected to cause an increase in production of abnormal protein-rich CSF and transependymal migration of CSF. We tested this hypothesis using a rat model of IVH, in which 160 µl of autologous blood was infused into the lateral ventricle, resulting in a twofold increase in ventricular size 48 h later. In this model, we found significant activation of nuclear factor κB (NF-κB) signaling by the CSF barrier cells of the choroid plexus and ependymal lining. Moreover, these inflammatory changes were associated with abnormal uptake of serum-derived IgG by the barrier cells, a phenomenon closely linked to abnormal permeability of the blood-brain barrier. We conclude that inflammation marked by NF-κB signaling is a prominent feature after IVH and may account for certain pathophysiological sequelae associated with IVH.

Rodent model of direct cranial blast injury.

Traumatic brain injury resulting from an explosive blast is one of the most serious wounds suffered by warfighters, yet the effects of explosive blast overpressure directly impacting the head are poorly understood. We developed a rodent model of direct cranial blast injury (dcBI), in which a blast overpressure could be delivered exclusively to the head, precluding indirect brain injury via thoracic transmission of the blast wave. We constructed and validated a Cranium Only Blast Injury Apparatus (COBIA) to deliver blast overpressures generated by detonating .22 caliber cartridges of smokeless powder. Blast waveforms generated by COBIA replicated those recorded within armored vehicles penetrated by munitions. Lethal dcBI (LD(50) ∼ 515 kPa) was associated with: (1) apparent brainstem failure, characterized by immediate opisthotonus and apnea leading to cardiac arrest that could not be overcome by cardiopulmonary resuscitation; (2) widespread subarachnoid hemorrhages without cortical contusions or intracerebral or intraventricular hemorrhages; and (3) no pulmonary abnormalities. Sub-lethal dcBI was associated with: (1) apnea lasting up to 15 sec, with transient abnormalities in oxygen saturation; (2) very few delayed deaths; (3) subarachnoid hemorrhages, especially in the path of the blast wave; (4) abnormal immunolabeling for IgG, cleaved caspase-3, and ß-amyloid precursor protein (ß-APP), and staining for Fluoro-Jade C, all in deep brain regions away from the subarachnoid hemorrhages, but in the path of the blast wave; and (5) abnormalities on the accelerating Rotarod that persisted for the 1 week period of observation. We conclude that exposure of the head alone to severe explosive blast predisposes to significant neurological dysfunction.