Neuromelioidosis
Neuromelioidosis is a central nervous system infection caused by the gram-negative bacterium, Burkholderia pseudomallei. The route of transmission commonly occurs through skin abrasion or by inhalation of contaminated water or soil. Risk factors include diabetes mellitus, alcohol intake, chronic renal disease, lung disease, and immunosuppression .
Melioidosis can involve multiple body systems but central nervous system infection has a mortality rate of approximately 25% and survivors have significant morbidity .
Clinical presentation
Neuromelioidosis has varying clinical presentation including headaches, altered level of consciousness, seizures, cerebellar signs, cranial nerve palsies, limb weakness and hemiparesis.
Epidemiology
The disease is endemic to areas of northern Australia and regions of southeast Asia during the wet seasons.
Pathology
Burkholderia pseudomallei has been demonstrated in recent microbiology studies to demonstrate axonal spread of disease by penetrating the nasopharyngeal mucosa with spread along the trigeminal and olfactory nerves in infected mice . This is an important finding as the bacteria can gain direct access to the CNS bypassing the blood-brain barrier.
Culture medium
Culture on blood agar / Ashdown's medium or Columbia Horse blood agar (Biomerieux, Australia), incubated in air at 37°.
Radiographic features
MRI
Neuromelioidosis manifests as enhancing microabscesses oriented along white matter tracts such as the corticospinal tract or corpus callosum .
Cranial nerve involvement is frequently seen with trigeminal and vestibulocochlear nerves. Contiguous spread of infection along the cranial nerves invariable result in brainstem abscess and rhombencephalitis .
Extra-axial disease can manifest as
- extradural brain/spinal abscess
- skull osteomyelitis
- scalp abscesses
Treatment and prognosis
Melioidosis can involve multiple body systems but central nervous system infection has a mortality rate of approximately 25% and survivors have significant morbidity .
Intravenous ceftazidime or imipenem for the eradication phase followed by oral maintenance therapy with either trimethoprim/sulfamethoxazole or doxycycline for at least six to eight months
or
Ceftazidime or meropenem alone or with the addition of co-trimoxazole as the most active regime.
History and etymology
The term neuromelioidosis was coined by the Australian physician Charlie Chia-Tsong Hsu et al. in 2013 .
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