Elsevier

Acta Tropica

Volume 74, Issues 2–3, 5 February 2000, Pages 145-151
Acta Tropica

Neurological melioidosis

https://doi.org/10.1016/S0001-706X(99)00064-9Get rights and content

Abstract

Neurological abnormalities have long been recognised in animals with melioidosis, including laboratory rodents and sheep in the first Australian outbreak in 1949. Autopsies in animals have shown microabscesses and lymphocytic infiltration to be present on occasion in the same animal, but Burkholderia pseudomallei is usually able to be grown from central nervous system (CNS) tissue. In humans CNS melioidosis is unusual, but both macroscopic brain abscesses and encephalitis occur. There has been a recently recognised syndrome of meningoencephalitis with varying involvement of brainstem, cerebellum and spinal cord. The prospective melioidosis study at Royal Darwin Hospital has documented 12 cases of CNS melioidosis over 9 years out of a total of 232 cases of melioidosis (5%). Prominent features on presentation were unilateral limb weakness (6), predominant cerebellar signs (2), mixed cerebellar and brainstem features with peripheral weakness (2) and flaccid paraparesis (2). Eight patients had unilateral VIIth nerve palsy and six bulbar palsy, with five requiring prolonged ventilation. Brain CT scans are usually normal initially, but MRI shows dramatic changes. Three patients died and only three made a full recovery. In two patients with predominant mononuclear CSF pleocytosis, B. pseudomallei was cultured from CSF and autopsy in one of these showed necrotising encephalitis with microabscesses. Although it has been postulated that a neurotropic exotoxin may account for melioidosis encephalomyelitis, the recent findings and comparison with the animal data suggest that direct organism spread within the CNS may be primarily responsible. Preliminary molecular typing of isolates shows no evidence of a specific strain of B. pseudomallei responsible for CNS melioidosis and further studies are required to determine if the apparent higher rate of CNS disease in Australia is due to true regional differences or is from increased ascertainment.

Section snippets

Neurological melioidosis in animals and humans

Neurological abnormalities in melioidosis have long been recognised in both animals and humans, although the rate of such abnormalities has usually been low. Early mouse models of infection with Burkholderia pseudomallei demonstrated hind-limb weakness (Dannenberg and Scott, 1958). It was subsequently noted in case reports from animals that there was a predilection for neurological melioidosis in animals to affect the brainstem and spinal cord (Omar, 1963), which was particularly notable in two

Neurologic melioidosis in the Royal Darwin Hospital Prospective Study

Royal Darwin Hospital (RDH) is the referral hospital for the Top End, with a population of around 140 000 (Australian Bureau of Statistics, Canberra 1997). All cases of melioidosis in the Top End are managed under the direction of the Division of Medicine at RDH, with most being admitted to RDH but some being managed in the regional hospitals in Katherine, 300 km to the south of Darwin or Gove to the east. Over the 9-year period from 1989 to 1998, there were 232 cases treated for melioidosis,

Discussion

It is now evident that at least some of the cases presenting with classical neurological melioidosis with involvement of brainstem, cerebellum and spinal cord have direct invasion of the CNS. There are many similarities with the animal case reports and animal studies, where extensive cultures and histology often find evidence of the organism in the CNS and where in a single animal there can be a mixed picture of microabscesses and lymphocytic infiltration.

The predominant mononuclear pleocytosis

Acknowledgements

We would like to acknowledge the expert assistance of Gary Lum, Brian Dwyer and the Microbiology staff of RDH and our medical and nursing colleagues throughout the Top End. In addition, the skills and enthusiasm of our Infectious Diseases registrars is much appreciated as is the support from laboratory staff at the Menzies School of Health Research. Peter Blumbergs provided expert neuropathological opinion on the autopsy tissue.

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