title: Neuroimaging in encephalitis: analysis of imaging findings and interobserver agreement.
abstract: OBJECTIVE
  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).
  
  
  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%.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Virus Reference Department, Public Health England, London, UK. Electronic address: juliagranerod@hotmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Granerod
authors.affiliation: Department of Neurology, Chelsea and Westminster Hospital, London, UK.
authors.forename: N W S
authors.initials: NWS
authors.lastname: Davies
authors.affiliation: Department of Neuroradiology, Derriford Hospital, Plymouth, UK.
authors.forename: W
authors.initials: W
authors.lastname: Mukonoweshuro
authors.affiliation: Department of Imaging, Charing Cross Hospital, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Mehta
authors.affiliation: Neuroradiology Department, The Walton Centre for Neurology and Neurosurgery, Liverpool, UK.
authors.forename: K
authors.initials: K
authors.lastname: Das
authors.affiliation: Children Neurosciences Centre, Evelina London Children's Hospital, Kings Health Partners Academic Health Science Centre, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Lim
authors.affiliation: Institute of Infection and Global Health, University of Liverpool, Walton Centre NHS Foundation Trust, and NIHR Health Protection Research Unit in Emerging and Zoonotic Infections, Liverpool, UK.
authors.forename: T
authors.initials: T
authors.lastname: Solomon
authors.affiliation: Neuroradiology Department, The Walton Centre for Neurology and Neurosurgery, Liverpool, UK.
authors.forename: S
authors.initials: S
authors.lastname: Biswas
authors.affiliation: Public Health Ontario, Toronto, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Rosella
authors.affiliation: Virus Reference Department, Public Health England, London, UK; Influenza and Measles Laboratory, Instituto Oswaldo Cruz, Fundacao Oswaldo Cruz, Rio de Janeiro, Brazil.
authors.forename: D W G
authors.initials: DWG
authors.lastname: Brown
authors.affiliation: Public Health Ontario, Toronto, Canada; University of Toronto Dalla Lana School of Public Health and Laboratory Medicine and Pathobiology, Toronto, Canada.
authors.forename: N S
authors.initials: NS
authors.lastname: Crowcroft
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging; D002648:Child; D002675:Child, Preschool; D020803:Encephalitis, Herpes Simplex / Q000000981:diagnostic imaging*; D004673:Encephalomyelitis, Acute Disseminated / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D059906:Neuroimaging / Q000379:methods*; D015588:Observer Variation; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult