Murray valley encephalitis mimicking herpes simplex encephalitis

doi:10.1016/j.jocn.2004.10.010

Journal of Clinical Neuroscience

Volume 12, Issue 7, September 2005, Pages 822-824

https://doi.org/10.1016/j.jocn.2004.10.010 Get rights and content

Summary

We describe a patient with serologically proven Murray Valley encephalitis (MVE), whose presentation was clinically and radiologically characteristic of Herpes simplex encephalitis (HSE). The reports of MRI abnormalities in MVE, and the closely related Japanese Encephalitis and West Nile virusii are mostly of bilateral thalamic or grey matter involvement. The MRI scan findings in this case instead showed the typical temporal lobe changes of HSE. Our case report highlights that MVE can mimic HSE, both clinically and radiologically. Therefore it is important to collect an accurate and detailed travel history from patients where there is a risk of exposure to MVE virus. If suspected, antibody testing of serum and CSF, and CSF for MVE-RNA if available, should be undertaken. This case also highlights the potential under-diagnosis of Murray Valley encephalitis.

Introduction

Murray Valley encephalitis virus (MVEV) is a mosquito-borne flavivirus that is closely related to Japanese encephalitis virus (JEV), Kunjin virus (KUNV) and West Nile virus (WNV). The majority of infections are asymptomatic or non-specific, with only about 1:500 to 1:1000 developing encephalitis.¹ Mortality from encephalitis is about 12% in adults and 25% in children, with neurological residua in 40% of survivors.² The clinical presentation is often nonspecific with fever and convulsions in children, and headache, fever and altered mental state in adults.[1], [3]

We describe a patient with a clinical and radiological syndrome characteristic of Herpes simplex encephalitis (HSE), who was subsequently shown to have Murray Valley encephalitis.

Section snippets

Case report

A 26 year old man had been resident in the Northern Territory and had been camping for a week in the bush southeast of Darwin four weeks prior to presentation, after which he returned to Darwin. One week later he left to drive to Perth over three days, and during that time camped in the north eastern Kimberley, in the southwest Kimberley and then in the Pilbara region. On presentation to hospital he gave a three day history of increasing left fronto-temporal headache and a one day history of

Discussion

This patient had serologically confirmed encephalitis due to MVEV. The absence of MVE-RNA in the CSF by PCR does not exclude infection, as it is found in less than 50% of patients, even within the first few days of illness (DW Smith, unpublished data). It is highly likely that he was infected when camping in the Kimberley as surveillance data indicated MVEV in that area, but not in the Northern Territory or Pilbara regions.⁶ His presentation was within the described incubation period of seven

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Citation Excerpt :
Cranial nerve palsies, tremors or rigidity are signs of the deep grey matter involvement typical of flavivirus encephalitis,34 consistent with the thalamic changes classically seen on MRI and occasionally on CT scan.35 However, not all cases have these features, and some may present, for example, with clinical and imaging findings suggestive of herpes simplex encephalitis.36 Involvement of the cervical spine and nerve roots may also occur.
Australia is a climatically diverse country varying from a tropical climate in the north to arid central desert and grassland regions, and to temperate climates in the south. There are many viral infections found in Australia that are common to developed countries worldwide, but this article will focus on those that pose a special risk for travellers to Australia, especially the mosquito-borne viruses. The commonest are the members of the alphavirus genus, particularly Ross River virus and Barmah Forest virus, which cause predominantly arthralgia with or without fever or rash. Less frequent but more serious illness is seen with the encephalitic flaviviruses, Murray Valley encephalitis virus, and the Kunjin strain of West Nile virus. In addition dengue occurs intermittently on the northern part of Queensland, and in recent years Japanese encephalitis virus has been found in the Torres Strait Islands and the tip of far north Queensland. Also of interest, but with a much lower risk, are the bat-borne viruses, Hendra virus and Australian bat lyssavirus, that have caused a small number of human infections. However, it is important to remember that most tourists pass through other countries in the Asia/Pacific region on their way to and from Australia and may therefore have acquired infections prior to or after leaving Australia.
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Case reportMurray valley encephalitis mimicking herpes simplex encephalitis

Summary

Introduction

Section snippets

Case report

Discussion

J Virol Methods

J Neurol Sci

Lancet

Australian encephalitis in Western Australia 1978–1991

Med J Aust

Murray Valley encephalitis in Western Australia in 2000, with evidence of southerly spread

Commun Dis Intell (Australia)

Australian encephalitis in the Northern Territory: clinical and epidemiological features, 1987–1996

Aust N Z J Med

Diagnosis and reporting of arbovirus infections in Australia

Comm Dis Intell

Case report
Murray valley encephalitis mimicking herpes simplex encephalitis