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A 27 year old woman developed a vesicular genital rash and cerebellar dysfunction with progressive neurological deterioration suggesting brain stem encephalitis. Respiratory support was required. Magnetic resonance imaging (MRI) of [...]

It is established that patients hospitalised with COVID-19 often have ongoing morbidity affecting activity of daily living (ADL), employment, and mental health. However, little is known about the relative outcomes in patients with COVID-19 neurological or psychiatric complications. We conducted a UK multicentre case-control study of patients hospitalised with COVID-19 (controls) and those who developed COVID-19 associated acute neurological or psychiatric complications (cases). Among the 651 patients, [362 (55%) cases and 289 (45%) controls], a higher proportion of cases had impairment in ADLs (199 [68.9%] vs 101 [51.8%], OR 2.06, p < 0.0002) and reported symptoms impacting employment (159 [58.2%] vs 69 [35.6%] OR 2.53, p < 0.0001). There was no significant difference in the proportion with depression or anxiety between case and control groups overall. For cases, impairment of ADLs was associated with increased risk in female sex, age > 50 years and hypertension (OR 5.43, p < 0.003, 3.11, p = 0.02, 3.66, p = 0.04). Those receiving either statins or angiotensin converting enzyme (ACE) inhibitors had a lower risk of impairment in ADLs (OR 0.09, p = 0.0006, 0.17, p = 0.03). Patients with neurological or psychiatric complications of COVID-19 had worse functional outcomes than those with respiratory COVID-19 alone in terms of ADLs and employment. Female sex, age > 50 years, and hypertension were associated with worse outcomes, and statins or ACE inhibitors with better outcomes., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Introduction: Human T-cell lymphotropic virus type 1 (HTLV-1) may cause spinal cord inflammation, leading to HTLV-1-associated myelopathy (HAM). HAM is a chronic and progressive neurological disorder that is associated with increased mortality and impaired quality of life. There are limited data on the incidence of HAM, with higher rates seen in Latin America and the Caribbean compared to Japan. We investigated the incidence of HAM in a cohort of initially asymptomatic people with HTLV-1 in the United Kingdom (UK)., Methods: This is a longitudinal retrospective observational study of people with confirmed HTLV-1 infection who first attended the National Centre for Human Retrovirology in London, UK, between 1st March 1991 and 31st March 2024. Clinical records were analysed to calculate the incidence rate and cumulative incidence of HAM. A secondary analysis was conducted to assess HAM incidence in people living with HTLV-1 and HIV coinfection. At the first visit, the HTLV-1 proviral load was compared between incident cases and those who remained asymptomatic during follow-up., Results: In a cohort with up to 33 years of follow-up of individuals living with HTLV-1 in the UK, the cumulative incidence of HTLV-1-associated myelopathy (HAM) was found to be 1.35% (4/297), with an incidence rate of 1.98 per 1,000 person-years. All people who developed HAM had a high proviral load at the first clinic visit. No cases of incident HAM were observed among individuals who had HIV-HTLV-1 coinfection during the study period., Discussion: The incidence of HAM in the UK cohort is comparable to the rates reported in Latin America and the Caribbean and is higher than reported in other high-income countries. High proviral load of HTLV-1 predates the development of HAM., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2025 Rosadas, Baylon, Greiller, Adonis, Dhasmana, Davies and Taylor.)

Reproducible and standardised neurological assessment scales are important in quantifying research outcomes. These scales are often performed by non-neurologists and/or non-clinicians and must be robust, quantifiable, reproducible and comparable to a neurologist's assessment. COVID-CNS is a multi-centre study which utilised the Neurological Impairment Scale (NIS) as a core assessment tool in studying neurological outcomes following COVID-19 infection. We investigated the strengths and weaknesses of the NIS when used by non-neurology clinicians and non-clinicians, and compared performance to a structured neurological examination performed by a neurology clinician. Through our findings, we provide practical advice on how non-clinicians can be readily trained in conducting reproducible and standardised neurological assessments in a multi-centre study, as well as illustrating potential pitfalls of these tools., Competing Interests: Declaration of competing interest T.S. is the Director of The Pandemic Institute which has received funding from Innova and CSL Seqirus and Aviva and DAM Health. T.S. was an advisor to the GSK Ebola Vaccine programme and the Siemens Diagnostic Programme. T.S. Chaired the Siemens Healthineers Clinical Advisory Board. T.S. Co-Chaired the WHO Neuro-COVID task force and sat on the UK Government Advisory Committee on Dangerous Pathogens, and the Medicines and Healthcare Products Regulatory Agency (MHRA) Expert Working Group on Covid-19 vaccines. T.S. Advised to the UK COVID-19 Therapeutics Advisory Panel (UK-TAP). T.S. was a Member of COVID-19 Vaccines Benefit Risk Expert Working Group for the Commission on Human Medicines (CHM) committee of the Medicines and Healthcare products Regulatory Agency (MHRA). T.S. has been a member of the Encephalitis Society since 1998 and President of the Encephalitis Society since 2019., (Copyright © 2024. Published by Elsevier Ltd.)

Encephalitis affects people across the lifespan, has high rates of mortality and morbidity, and results in significant neurological sequelae with long-term consequences to quality of life and wider society. The true incidence is currently unknown due to inaccurate reporting systems. The disease burden of encephalitis is unequally distributed across the globe being highest in low- and middle-income countries where resources are limited. Here countries often lack diagnostic testing, with poor access to essential treatments and neurological services, and limited surveillance and vaccination programs. Many types of encephalitis are vaccine preventable, whereas others are treatable with early diagnosis and appropriate management. In this viewpoint, we provide a narrative review of key aspects of diagnosis, surveillance, treatment, and prevention of encephalitis and highlight priorities for public health, clinical management, and research, to reduce the disease burden., Competing Interests: Potential conflicts of interest. T. S. reports royalties for text and non-fiction books from Oxford University Press, Elsevier, Liverpool University Press, and Cambridge University Press; consulting fees from Medicines and Healthcare products Regulatory Agency (MHRA); a pending patent for bacterial meningitis test (no. GB1606537); participation on a Data Safety Monitoring Committee for GSK; participation on advisory boards for GSK (advisor to Ebola Vaccine Programme and Siemens Diagnostic Programme), Siemens (Healthineers Chair), WHO (Neruro-COVID Task force co-chair), UK Government (Dangerous Pathogens Committee), MHRA (Expert Working Group on COVID-19 vaccines), UK COVID-19 Therapeutics Panel, Commission on Human Medicines Committee of the Medicines and Healthcare products Regulatory Agency (COVID-19 Vaccines Benefit Risk Expert Working Group); and previously held shares of Medefer Solutions. NWSD reports participation as Chair of the external review panel for Encephlg trial (IRAS ID 280904) and Chair of the Scientific Advisory Panel for the Encephalitis Society. J. G. reports contracts with a range of clients through their consultancy business and has in the past received consultancy fees from the Encephalitis Society. A. E. is the CEO of The Encephalitis Society and reports society-received charitable grants from Pfizer, CSL Behring, Bavarian Nordic, Snofi, UC, and Valneva; royalties from an authored book; institutional payments for speaking engagements from Valneva, Pfizer, and Eurolmmun. B. D. M. reports honoraria for presentations at SCRIPPS and University of Massachusetts; payment for expert testimony for Midicolegal work; and a role as Vice Chair of the Scientific Advisory Panel for the Encephalitis Society. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Awareness of neurological sequelae of dengue fever is increasing. However, as this case illustrates, there is a diagnostic conundrum in determining whether certain features are in keeping with dengue encephalopathy or dengue encephalitis. Further consensus is required., Competing Interests: Potential conflicts of interest. All authors: No reported conflicts., (© The Author(s) 2023. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)

Objectives: Encephalitis, brain inflammation and swelling, most often caused by an infection or the body's immune defences, can have devastating consequences, especially if diagnosed late. We looked for clinical predictors of different types of encephalitis to help clinicians consider earlier treatment., Methods: We conducted a multicentre prospective observational cohort study (ENCEPH-UK) of adults (> 16 years) with suspected encephalitis at 31 UK hospitals. We evaluated clinical features and investigated for infectious and autoimmune causes., Results: 341 patients were enrolled between December 2012 and December 2015 and followed up for 12 months. 233 had encephalitis, of whom 65 (28%) had HSV, 38 (16%) had confirmed or probable autoimmune encephalitis, and 87 (37%) had no cause found. The median time from admission to 1st dose of aciclovir for those with HSV was 14 hours (IQR 5-50); time to 1st dose of immunosuppressant for the autoimmune group was 125 hours (IQR 45-250). Compared to non-HSV encephalitis, patients with HSV more often had fever, lower serum sodium and lacked a rash. Those with probable or confirmed autoimmune encephalitis were more likely to be female, have abnormal movements, normal serum sodium levels and a cerebrospinal fluid white cell count < 20 cells x106/L, but they were less likely to have a febrile illness., Conclusions: Initiation of treatment for autoimmune encephalitis is delayed considerably compared with HSV encephalitis. Clinical features can help identify patients with autoimmune disease and could be used to initiate earlier presumptive therapy., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Defres et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Cognitive impairment and chronic pain are amongst the most prevalent neurological sequelae of HIV infection, yet little is understood about the potential bidirectional relationship between the two conditions. Cognitive dysfunction can occur in chronic pain populations whilst those with cognitive impairment can display modified responses to experimentally induced painful stimuli. To date, this has not been explored in HIV cohorts.This study aimed to identify any contribution of chronic pain to cognitive impairment in HIV and to determine differences in pain characteristics between those with and without cognitive dysfunction.This was an observational cohort study involving people living with HIV ( n  = 148) in the United Kingdom. Participants underwent validated questionnaire-based measurement of pain severity, interference and symptom quality as well as conditioned pain modulation and quantitative sensory testing. All participants completed a computer-based cognitive function assessment.Fifty-seven participants met the criteria for cognitive impairment and 73 for chronic pain. The cognitive impairment group had a higher prevalence of chronic pain ( p  = 0.004) and reported more neuropathic symptoms ( p  = 0.001). Those with chronic pain performed less well in emotional recognition and verbal learning domains. The interaction identified between chronic pain and cognitive dysfunction warrants further exploration to identify causal links or shared pathology.

Encephalitis describes inflammation of the brain parenchyma, typically caused by either an infectious agent or through an autoimmune process which may be postinfectious, paraneoplastic or idiopathic. Patients can present with a combination of fever, alterations in behaviour, personality, cognition and consciousness. They may also exhibit focal neurological deficits, seizures, movement disorders and/or autonomic instability. However, it can sometimes present non-specifically, and this combined with its many causes make it a difficult to manage neurological syndrome. Despite improved treatments in some forms of encephalitides, encephalitis remains a global concern due to its high mortality and morbidity. Prompt diagnosis and administration of specific and supportive management options can lead to better outcomes. Over the last decade, research in encephalitis has led to marked developments in the understanding, diagnosis and management of encephalitis. In parallel, the number of autoimmune encephalitis syndromes has rapidly expanded and clinically characteristic syndromes in association with pathogenic autoantibodies have been defined. By focusing on findings presented at the Encephalitis Society's conference in December 2021, this article reviews the causes, clinical manifestations and management of encephalitis and integrate recent advances and challenges of research into encephalitis., (© The Author(s) 2022. Published by Oxford University Press on behalf of Postgraduate Medical Journal.)

Purpose of Review: Vaccinations have been pivotal in lowering the global disease burden of vaccine-preventable encephalitides, including Japanese encephalitis, tick-borne encephalitis, measles encephalitis, and rabies encephalitis, among others., Recent Findings: Populations vulnerable to vaccine-preventable infections that may lead to encephalitis include those living in endemic and rural areas, military members, migrants, refugees, international travelers, younger and older persons, pregnant women, the immunocompromised, outdoor, healthcare and laboratory workers, and the homeless. There is scope for improving the availability and distribution of vaccinations, vaccine equity, surveillance of vaccine-preventable encephalitides, and public education and information., Summary: Addressing these gaps in vaccination strategies will allow for improved vaccination coverage and lead to better health outcomes for those most at risk for vaccine-preventable encephalitis., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Painful HIV-associated neuropathy (HIV-SN) is a prevalent co-morbidity of HIV infection. Sensory phenotyping, using quantitative sensory testing (QST) could allow for improved stratification to guide personalized treatment. However, previous methods of QST interpretation have demonstrated limited association with self-reported pain measures. This study sought to identify differences in self-reported pain measures between composite QST-derived sensory phenotypes, and to examine any differences in participants reporting multi-site, multi-etiology chronic pain. In this cross-sectional observational study of participants with HIV (n = 133), individuals were allocated to neuropathy and neuropathic pain groups through clinical assessment and nerve conduction testing. They completed symptom-based questionnaires and underwent standardized QST. Participants were assigned, by pre-determined algorithm, to a QST-derived sensory phenotype. Symptoms were compared between sensory phenotypes. Symptom characteristics and Neuropathic Pain Symptom Inventory scores differed between QST-derived sensory phenotypes: 'sensory loss' was associated with more paroxysmal and paraesthetic symptoms compared to 'thermal hyperalgesia' and 'healthy' phenotypes (P = .023-0.001). Those with painful HIV-SN and additional chronic pain diagnoses were more frequently allocated to the 'mechanical hyperalgesia' phenotype compared to those with painful HIV-SN alone (P = .006). This study describes heterogeneous sensory phenotypes in people living with HIV. Differences in self-reported pain outcomes between sensory phenotypes has the potential to guide future stratified trials and eventually more targeted therapy. PERSPECTIVE: This article presents quantitative sensory testing derived phenotypes, thought to reflect differing pathophysiological pain mechanisms and relates them to self-reported pain measures in people with HIV infection. This could help clinicians stratify patients to individualize analgesic interventions more effectively., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

SARS-CoV-2 is associated with new-onset neurological and psychiatric conditions. Detailed clinical data, including factors associated with recovery, are lacking, hampering prediction modelling and targeted therapeutic interventions. In a UK-wide cross-sectional surveillance study of adult hospitalized patients during the first COVID-19 wave, with multi-professional input from general and sub-specialty neurologists, psychiatrists, stroke physicians, and intensivists, we captured detailed data on demographics, risk factors, pre-COVID-19 Rockwood frailty score, comorbidities, neurological presentation and outcome. A priori clinical case definitions were used, with cross-specialty independent adjudication for discrepant cases. Multivariable logistic regression was performed using demographic and clinical variables, to determine the factors associated with outcome. A total of 267 cases were included. Cerebrovascular events were most frequently reported (131, 49%), followed by other central disorders (95, 36%) including delirium (28, 11%), central inflammatory (25, 9%), psychiatric (25, 9%), and other encephalopathies (17, 7%), including a severe encephalopathy ( n  = 13) not meeting delirium criteria; and peripheral nerve disorders (41, 15%). Those with the severe encephalopathy, in comparison to delirium, were younger, had higher rates of admission to intensive care and a longer duration of ventilation. Compared to normative data during the equivalent time period prior to the pandemic, cases of stroke in association with COVID-19 were younger and had a greater number of conventional, modifiable cerebrovascular risk factors. Twenty-seven per cent of strokes occurred in patients <60 years. Relative to those >60 years old, the younger stroke patients presented with delayed onset from respiratory symptoms, higher rates of multi-vessel occlusion (31%) and systemic thrombotic events. Clinical outcomes varied between disease groups, with cerebrovascular disease conferring the worst prognosis, but this effect was less marked than the pre-morbid factors of older age and a higher pre-COVID-19 frailty score, and a high admission white cell count, which were independently associated with a poor outcome. In summary, this study describes the spectrum of neurological and psychiatric conditions associated with COVID-19. In addition, we identify a severe COVID-19 encephalopathy atypical for delirium, and a phenotype of COVID-19 associated stroke in younger adults with a tendency for multiple infarcts and systemic thromboses. These clinical data will be useful to inform mechanistic studies and stratification of patients in clinical trials., (© The Author(s) (2021). Published by Oxford University Press on behalf of the Guarantors of Brain.)

Preliminary clinical data indicate that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is associated with neurological and neuropsychiatric illness. Responding to this, a weekly virtual coronavirus disease 19 (COVID-19) neurology multi-disciplinary meeting was established at the National Hospital, Queen Square, in early March 2020 in order to discuss and begin to understand neurological presentations in patients with suspected COVID-19-related neurological disorders. Detailed clinical and paraclinical data were collected from cases where the diagnosis of COVID-19 was confirmed through RNA PCR, or where the diagnosis was probable/possible according to World Health Organization criteria. Of 43 patients, 29 were SARS-CoV-2 PCR positive and definite, eight probable and six possible. Five major categories emerged: (i) encephalopathies (n = 10) with delirium/psychosis and no distinct MRI or CSF abnormalities, and with 9/10 making a full or partial recovery with supportive care only; (ii) inflammatory CNS syndromes (n = 12) including encephalitis (n = 2, para- or post-infectious), acute disseminated encephalomyelitis (n = 9), with haemorrhage in five, necrosis in one, and myelitis in two, and isolated myelitis (n = 1). Of these, 10 were treated with corticosteroids, and three of these patients also received intravenous immunoglobulin; one made a full recovery, 10 of 12 made a partial recovery, and one patient died; (iii) ischaemic strokes (n = 8) associated with a pro-thrombotic state (four with pulmonary thromboembolism), one of whom died; (iv) peripheral neurological disorders (n = 8), seven with Guillain-Barré syndrome, one with brachial plexopathy, six of eight making a partial and ongoing recovery; and (v) five patients with miscellaneous central disorders who did not fit these categories. SARS-CoV-2 infection is associated with a wide spectrum of neurological syndromes affecting the whole neuraxis, including the cerebral vasculature and, in some cases, responding to immunotherapies. The high incidence of acute disseminated encephalomyelitis, particularly with haemorrhagic change, is striking. This complication was not related to the severity of the respiratory COVID-19 disease. Early recognition, investigation and management of COVID-19-related neurological disease is challenging. Further clinical, neuroradiological, biomarker and neuropathological studies are essential to determine the underlying pathobiological mechanisms that will guide treatment. Longitudinal follow-up studies will be necessary to ascertain the long-term neurological and neuropsychological consequences of this pandemic., (© The Author(s) (2020). Published by Oxford University Press on behalf of the Guarantors of Brain.)

Background: Concerns regarding potential neurological complications of COVID-19 are being increasingly reported, primarily in small series. Larger studies have been limited by both geography and specialty. Comprehensive characterisation of clinical syndromes is crucial to allow rational selection and evaluation of potential therapies. The aim of this study was to investigate the breadth of complications of COVID-19 across the UK that affected the brain., Methods: During the exponential phase of the pandemic, we developed an online network of secure rapid-response case report notification portals across the spectrum of major UK neuroscience bodies, comprising the Association of British Neurologists (ABN), the British Association of Stroke Physicians (BASP), and the Royal College of Psychiatrists (RCPsych), and representing neurology, stroke, psychiatry, and intensive care. Broad clinical syndromes associated with COVID-19 were classified as a cerebrovascular event (defined as an acute ischaemic, haemorrhagic, or thrombotic vascular event involving the brain parenchyma or subarachnoid space), altered mental status (defined as an acute alteration in personality, behaviour, cognition, or consciousness), peripheral neurology (defined as involving nerve roots, peripheral nerves, neuromuscular junction, or muscle), or other (with free text boxes for those not meeting these syndromic presentations). Physicians were encouraged to report cases prospectively and we permitted recent cases to be notified retrospectively when assigned a confirmed date of admission or initial clinical assessment, allowing identification of cases that occurred before notification portals were available. Data collected were compared with the geographical, demographic, and temporal presentation of overall cases of COVID-19 as reported by UK Government public health bodies., Findings: The ABN portal was launched on April 2, 2020, the BASP portal on April 3, 2020, and the RCPsych portal on April 21, 2020. Data lock for this report was on April 26, 2020. During this period, the platforms received notification of 153 unique cases that met the clinical case definitions by clinicians in the UK, with an exponential growth in reported cases that was similar to overall COVID-19 data from UK Government public health bodies. Median patient age was 71 years (range 23-94; IQR 58-79). Complete clinical datasets were available for 125 (82%) of 153 patients. 77 (62%) of 125 patients presented with a cerebrovascular event, of whom 57 (74%) had an ischaemic stroke, nine (12%) an intracerebral haemorrhage, and one (1%) CNS vasculitis. 39 (31%) of 125 patients presented with altered mental status, comprising nine (23%) patients with unspecified encephalopathy and seven (18%) patients with encephalitis. The remaining 23 (59%) patients with altered mental status fulfilled the clinical case definitions for psychiatric diagnoses as classified by the notifying psychiatrist or neuropsychiatrist, and 21 (92%) of these were new diagnoses. Ten (43%) of 23 patients with neuropsychiatric disorders had new-onset psychosis, six (26%) had a neurocognitive (dementia-like) syndrome, and four (17%) had an affective disorder. 18 (49%) of 37 patients with altered mental status were younger than 60 years and 19 (51%) were older than 60 years, whereas 13 (18%) of 74 patients with cerebrovascular events were younger than 60 years versus 61 (82%) patients older than 60 years., Interpretation: To our knowledge, this is the first nationwide, cross-specialty surveillance study of acute neurological and psychiatric complications of COVID-19. Altered mental status was the second most common presentation, comprising encephalopathy or encephalitis and primary psychiatric diagnoses, often occurring in younger patients. This study provides valuable and timely data that are urgently needed by clinicians, researchers, and funders to inform immediate steps in COVID-19 neuroscience research and health policy., Funding: None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Click here to listen to the Podcast 'Query encephalitis' is a common neurological consultation in hospitalised patients. Identifying the syndrome is only part of the puzzle. Although historically encephalitis has been almost synonymous with infection, we increasingly recognise parainfectious or postinfectious as well as other immune-mediated causes. We must also distinguish encephalitis from other causes of encephalopathy, including systemic infection, metabolic derangements, toxins, inherited metabolic disorders, hypoxia, trauma and vasculopathies. Here, we review the most important differential diagnoses (mimics) of patients presenting with an encephalitic syndrome and highlight some unusual presentations (chameleons) of infectious encephalitis., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Human T-cell lymphotropic virus (HTLV)-1-associated myelopathy (HAM) is well described. Clinical features are predominantly consistent with cord pathology, though imaging and autopsy studies also demonstrate brain inflammation. In general, this is subclinical; however, six cases have previously been reported of encephalopathy in HTLV-1-infected patients, without alternative identified aetiology. We describe three further cases of encephalitis in the UK HAM cohort (n = 142), whereas the annual incidence of acute encephalitis in the general population is 0.07-12.6 per 100,000. Clinical features included reduced consciousness, fever/hypothermia, headaches, seizures, and focal neurology. Investigation showed: raised CSF protein; pleocytosis; raised CSF:peripheral blood mononuclear cell HTLV-1 proviral load ratio; and MRI either normal or showing white matter changes in brain and cord. Four of the six previous case reports of encephalopathy in HTLV-infected patients also had HAM. Histopathology, reported in three, showed perivascular predominantly CD8+ lymphocytic infiltrates in the brain. One had cerebral demyelination, and all had cord demyelination. We have reviewed the existing six cases in the literature, together with our three new cases. In all seven with HAM, the spastic paraparesis deteriorated sub-acutely preceding encephalitis. Eight of the nine were female, and four of the seven treated with steroids improved. We propose that HTLV-associated encephalopathy may be part of the spectrum of HTLV-1-induced central nervous system disease.

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., (Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)