Aim To assess the role of imaging in the early management of encephalitis and the agreement on findings in a well-defined cohort of suspected encephalitis cases enrolled in the Prospective Aetiological Study of Encephalitis conducted by the Health Protection Agency (now incorporated into Public Health England). Materials and methods Eighty-five CT examinations from 68 patients and 101 MRI examinations from 80 patients with suspected encephalitis were independently rated by three neuroradiologists blinded to patient and clinical details. The level of agreement on the interpretation of images was measured using the kappa statistic. The sensitivity, specificity, and negative and positive predictive values of CT and MRI for herpes simplex virus (HSV) encephalitis and acute disseminated encephalomyelitis (ADEM) were estimated. Results The kappa value for interobserver agreement on rating the scans as normal or abnormal was good (0.65) for CT and moderate (0.59) for MRI. Agreement for HSV encephalitis was very good for CT (0.87) and MRI (0.82), but only fair for ADEM (0.32 CT; 0.31 MRI). Similarly, the overall sensitivity of imaging for HSV encephalitis was ∼80% for both CT and MRI, whereas for ADEM it was 0% for CT and 20% for MRI. MRI specificity for HSV encephalitis between 3–10 days after symptom onset was 100%. Conclusion There is a subjective component to scan interpretation that can have important implications for the clinical management of encephalitis cases. Neuroradiologists were good at diagnosing HSV encephalitis; however, agreement was worse for ADEM and other alternative aetiologies. Findings highlight the importance of a comprehensive and multidisciplinary approach to diagnosing the cause of encephalitis that takes into account individual clinical, microbiological, and radiological features of each patient.
Bibliographical noteFunding Information:
We gratefully acknowledge the patients and their next of kin for providing consent to participate; the staff at participating centres; the Department of Health for funding; the UK Clinical Virology Network; and the Encephalitis Society. This report is independent research commissioned and funded by the Department of Health Policy Research Programme (Enhanced Diagnostic and Management Strategies to Improve the Identification and Outcome of Individuals with Encephalitis, 047/1084 ). The views expressed in this publication are those of the author(s) and not necessarily those of the Department of Health. M.L. receives research grants from Action Medical Research , DES society , GOSH charity , NIHR , MS Society , SPARKS charity and; receives research support grants from the London Clinical Research Network and Evelina Appeal ; has received consultation fees from CSL Behring ; received travel grants from Merck Serono ; and awarded educational grants to organize meetings by Novartis , Biogen-Idec , Merck Serono and Bayer . N.D. has received an educational grant from Biogen-Idec .
© 2016 The Royal College of Radiologists
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