Brain-Eating Amoebae: Predilection Sites in the Brain and Disease Outcome

Abstract

Acanthamoeba spp. and Balamuthia mandrillaris are causative agents of granulomatous amoebic encephalitis (GAE), while Naegleria fowleri causes primary amoebic meningoencephalitis (PAM). PAM is an acute infection that lasts a few days, while GAE is a chronic to subacute infection that can last up to several months. Here, we present a literature review of 86 case reports from 1968 to 2016, in order to explore the affinity of these amoebae for particular sites of the brain, diagnostic modalities, treatment options, and disease outcomes in a comparative manner.

Keywords: brain; central nervous system infections; free-living amoebae; meningoencephalitis.

FIG 1

Sites of infection of GAE due to Acanthamoeba spp. The majority of cases involved the cerebral cortices, with the frontal lobe and the temporal lobe being most affected, followed by the parietal lobe and the occipital lobe. Among extracortical sites, the cerebellum and the corticomedullary junction were the most favored sites. Hydrocephalus, which results from blockage of CSF drainage, was observed in a few cases. Other affected sites included the thalamus, the caudate nucleus, and the brainstem. Infection can also present as normal findings in early neuroimaging.

FIG 2

Sites of infection of GAE due to Balamuthia mandrillaris. Involvement of the temporal lobe was observed in most cases, followed by involvement of the frontal, parietal, and occipital lobes. Among extracortical sites, the thalamus was most affected, followed by the corticomedullary junction, the cerebellum, and the basal ganglia.

FIG 3

Sites of infection of PAM due to Naegleria fowleri. More cases involved the frontal lobe, followed by the parietal lobe and the corticomedullary junction. Hydrocephalus was observed in 27% of cases.