Case Report
Early Diagnosis of Herpes Encephalopathy Using Fluid-Attenuated Inversion Recovery Pulse Sequence

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Abstract

This study describes the usefulness of fluid-attenuated inversion recovery (FLAIR) pulse sequence for early diagnosis and treatment of herpes encephalitis. An 8-year-old boy with suspected herpes simplex encephalitis was examined by magnetic resonance imaging at 3 days post-symptom onset. Lesions in the right thalamus and insular cortex were detected by conventional T2-weighted images and images from FLAIR pulse sequence. Bilateral temporal lesions, however, were only detected by FLAIR images.

Introduction

Herpes simplex virus (HSV) type 1 is known as the cause of acute necrotizing encephalitis, which is typically seen in the temporal lobe lesions 1, 2of the cerebral cortex. Patients with HSV encephalitis frequently present with a rapid onset of neurologic symptoms and with rapid progression from confusion to coma within a few days 1, 2, 3. Antiviral therapy must be started during the acute stage to achieve any clinical benefit [4]. Magnetic resonance imaging (MRI) is a more sensitive noninvasive test for early diagnosis of herpes simplex encephalitis (HSE) than computed tomography (CT) 4, 5, 6. However, some patients have been observed to suffer from HSE that caused temporal lesions that were not clearly detectable in the acute stage after onset of seizures using conventional T1-weighted images and T2-weighted images [7]. Recently, fluid-attenuated inversion recovery (FLAIR) imaging has proven very useful in differentiating between normal tissues and pathologic tissues in brain diseases in childhood 8, 9, 10, 11, 12. The current study suggests that FLAIR pulse sequence allows for earlier detection of temporal lesions caused by HSE. The advantage of early diagnosis of temporal lesions is the possibility of starting early antiviral therapy for HSE and preventing the development of necrotizing lesions.

Section snippets

Case Report

An 8-year-old boy was admitted with a 2-day reported history of headache, numbed fingers and legs, fever of 38°C, and a 1-day history of vomiting. This patient did not ever have a past or recent history of mucocutaneous eruption that was suggestive of herpes. Tonic-clonic seizures and left hemiparalysis were observed on medical examination. The test of cerebrospinal fluid (CSF) revealed 40 white blood cells with 40% segmented neutrophils and 60% lymphocytes, no xanthochromia, contained

Discussion

Because early diagnosis is a key point regarding initiation of HSE therapy, several imaging techniques 3, 6, 15, EEG [2], biochemical examinations in serum and CSF 16, 17, 18for early diagnosis, and therapeutic monitoring of HSE have been reported. The morbidity and mortality of HSE remain high, however, despite antiviral therapy with Acyclovir. Therefore, all clinical and laboratory data should be considered before making a decision to withhold or discontinue antiviral therapy with Acyclovir.

Acknowledgements

The authors thank Marilyn Fairchild for her detailed editing; Tetsuo Ueno, Ryuji Takanashi, and Hiroshi Oba for their technical support; and Oto Kumi, Yo Umeda, and Yoji Iikura for their clinical support.

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