An Overview of Laboratory Diagnosis of Central Nervous System Viral Infections

Central nervous system (CNS) infection is a serious illness that can lead to death. CNS infections include meningitis, encephalitis, brain abscesses and myelitis. These diseases are caused by causative agents like bacteria, fungi, parasites, and protozoa, but most commonly by viral infections. To combat this issue, accurate diagnosis of etiological agents at an early stage is crucial for appropriate treatment, control of the disease and prevent from becoming life-threatening to the patients. This review paper summarises the main laboratory diagnostic methods for CNS infections caused by viruses ranging from conventional to molecular methods. Conventional isolation methods are considered the 'gold standard' as they provide accurate evidence, but require highly skilled personnel, are time-consuming, critical in cell type selection and are useless for non-cultivable viruses. Electron microscopy allows recognition of viral morphology and ultrastructural details as the principle of virus identification through negative staining or thin section technique (suitable for tissue or cell specimens). However, it offers low sensitivity and requires at least 106 virions per millilitre or milligram in the specimen to be detectable by microscopy. Immunological-based methods have been extensively applied for viral diagnosis by detecting the antiviral antibodies or viral antigens in clinical samples. While these methods provided high sensitivity and specificity, the incubation and window period of an infection may give false-negative results. Lastly, molecular detections have many advantages such as high sensitivity, specificity, rapid, require a small amount of sample, simultaneous detection of multiple different viruses, and produce both qualitative and quantitative results.