A Systematic Review of Cases of Meningitis in the Absence of Cerebrospinal Fluid Pleocytosis on Lumbar Puncture

Background: Definitive diagnosis of meningitis is made by analysis of cerebrospinal fluid (CSF) culture or polymerase chain reaction (PCR) obtained from a lumbar puncture (LP), which may take days. A timelier diagnostic clue of meningitis is pleocytosis on CSF analysis. However, meningitis may occur in the absence of pleocytosis on CSF. Areas of Uncertainty: A diagnosis of meningitis seems less likely without pleocytosis on CSF, leading clinicians to prematurely exclude this. Further, there is little available literature on the subject.Methods: Ovid/Medline and Google Scholar search was conducted for cases of CSF culture-confirmed meningitis with lack of pleocytosis. Inclusion criterion was reported cases of CSF culture-positive or PCR positive meningitis in the absence of pleocytosis on LP. Exclusion criteria were pleocytosis on CSF, cases in which CSF cultures/PCR were not performed, and articles that did not include CSF laboratory values.Results: A total of 124 cases from 51 articles were included. Causative organisms were primarily bacterial (99 cases). Outcome was reported in 86 cases, 27 of which died and 59 survived. Mortality in viral, fungal and bacterial organisms was 0, 56 and 31%, respectively. The overall percentage of positive initial CSF PCR/culture for viral, fungal and bacterial organisms was 100, 89 and 82%, respectively. Blood cultures were performed in 79 of the 124 cases, 56 (71%) of which ultimately cultured the causative organism. In addition to bacteremia, concomitant sources of infection occurred in 17 cases.Conclusions: Meningitis in the absence of pleocytosis on CSF is rare. If this occurs, causative organism is likely bacterial. We recommend ordering blood cultures as an adjunct, and, if clinically relevant, concomitant sources of infection should be sought. If meningitis is suspected, empiric antibiotics/antifungals should be administered regardless of initial WBC count on lumbar puncture

Effects of mechanical properties and atherosclerotic artery size on biomechanical plaque disruption - mouse vs. human.

International audienceMouse models of atherosclerosis are extensively being used to study the mechanisms of atherosclerotic plaque development and the results are frequently extrapolated to humans. However, major differences have been described between murine and human atherosclerotic lesions and the determination of similarities and differences between these species has been largely addressed recently. This study takes over and extends previous studies performed by our group and related to the biomechanical characterization of both mouse and human atherosclerotic lesions. Its main objective was to determine the distribution and amplitude of mechanical stresses including peak cap stress (PCS) in aortic vessels from atherosclerotic apoE(-/-) mice, in order to evaluate whether such biomechanical data would be in accordance with the previously suggested lack of plaque rupture in this model. Successful finite element analysis was performed from the zero-stress configuration of aortic arch sections and mainly indicated (1) the modest role of atherosclerotic lesions in the observed increase in residual parietal stresses in apoE(-/-) mouse vessels and (2) the low amplitude of murine PCS as compared to humans. Overall, the results from the present study support the hypothesis that murine biomechanical properties and artery size confer less propensity to rupture for mouse lesions in comparison with those of humans