Septic metastatic encephalitis: coexistence of brain damage and repair

Abstract

The coexistence of degenerative processes predominantly in the neocortex and regenerative activity in the hippocampal formation known from bacterial meningitis also characterizes the pathology of SME.

Fungal encephalitis in human autopsy cases is associated with extensive neuronal damage but only minimal repair

“…The severity of axonal injury was in the same range in fungal encephalitis as in septic‐metastatic encephalitis (Figure of the present work compared with figure of Tauber et al . , P = 0.135, Mann–Whitney U ‐test) and bacterial meningitis (figure of Gerber et al . ).…”

HIV encephalopathy: glial activation and hippocampal neuronal apoptosis, but limited neural repair

“…The number of lesions with acute axonal damage (a lesion was defined as a locally restricted accumulation of APP‐positive axons) was converted into a semiquantitative score: 0 points for no damage or just single injured axons, 1 point for mild damage (one or two lesions), 2 points for moderate damage (three or four lesions) and 3 points for severe damage (more than four lesions) [17,22]. Microglial activation as well as astrocytosis in the frontal cortex was categorized in three groups according to the density of immunoreactive cells and converted into a semiquantitative score: 1 point for < 10 Iba‐1‐immunoreactive cells, 2 points for ≥ 10 and < 30 Iba‐1‐positive cells, and 3 points for ≥ 30 Iba‐1‐positive cells at 20x magnification in three random regions in the frontal cortex.…”

“…Accordingly, in patients with HIV encephalitis and HIV‐associated dementia, numerous cortical neurons with active caspase‐3 immunoreactivity were noted, whereas morphological changes associated with apoptosis were infrequent [18]. The human brain possesses a limited capacity to combat neuronal loss by an increase in neurogenesis, which is observed in bacterial meningitis, septic encephalitis and cerebral hypoxia, but not in fungal meningoencephalitis [17,19–22]. The present study was performed to characterize neuronal injury, including apoptosis and neural repair, in HIV encephalopathy.…”

“…Neuronal loss in the hippocampal formation – dentate granule cell apoptosis and hippocampal pyramidal cell necrosis – is a prominent feature of CNS infections in human autopsy cases and experimental animals [14–17]. Accordingly, in patients with HIV encephalitis and HIV‐associated dementia, numerous cortical neurons with active caspase‐3 immunoreactivity were noted, whereas morphological changes associated with apoptosis were infrequent [18].…”

Pre-infection physical exercise decreases mortality and stimulates neurogenesis in bacterial meningitis

“…While acute diseases of the brain regularly cause cell damage and neuronal death, endogenous mechanisms of cell proliferation in neuronal precursor cells and stimulation of neurogenesis in response to brain injury have been observed in several diseases of the central nervous system (CNS), for example, in cerebral ischemia [7,8], in head trauma [9], after epileptic seizures [10], in hypoxic-ischemic encephalopathy [11] and in septic-metastatic encephalitis [12]. Similarly, hippocampal neurogenesis was also increased after bacterial meningitis in experimental models and in a human autopsy study [13-15].…”