What is acute disseminated encephalomyelitis (ADEM)?

Acute Disseminated Encephalomyelitis: Current Perspectives

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated central nervous system (CNS) disorder, characterized by polyfocal symptoms, encephalopathy and typical magnetic resonance imaging (MRI) findings, that especially affects young children. Advances in understanding CNS neuroimmune disorders as well as the association of myelin oligodendrocyte glycoprotein antibody (MOG-Ab) with both monophasic and recurrent forms of ADEM have led to new insights into its definition, management and outcome. In this review, we aim to provide an update based on current epidemiologic, clinical, radiological and immunopathological aspects and clinical outcome of ADEM.

Experimental Models of Autoimmune Demyelinating Diseases in Nonhuman Primates

Human idiopathic inflammatory demyelinating diseases (IIDD) are a heterogeneous group of autoimmune inflammatory and demyelinating disorders of the central nervous system (CNS). These include multiple sclerosis (MS), the most common chronic IIDD, but also rarer disorders such as acute disseminated encephalomyelitis (ADEM) and neuromyelitis optica (NMO). Great efforts have been made to understand the pathophysiology of MS, leading to the development of a few effective treatments. Nonetheless, IIDD still require a better understanding of the causes and underlying mechanisms to implement more effective therapies and diagnostic methods. Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model to study the pathophysiology of IIDD. EAE is principally induced through immunization with myelin antigens combined with immune-activating adjuvants. Nonhuman primates (NHP), the phylogenetically closest relatives of humans, challenged by similar microorganisms as other primates may recapitulate comparable immune responses to that of humans. In this review, the authors describe EAE models in 3 NHP species: rhesus macaques ( Macaca mulatta), cynomolgus macaques ( Macaca fascicularis), and common marmosets ( Callithrix jacchus), evaluating their respective contribution to the understanding of human IIDD. EAE in NHP is a heterogeneous disease, including acute monophasic and chronic polyphasic forms. This diversity makes it a versatile model to use in translational research. This clinical variability also creates an opportunity to explore multiple facets of immune-mediated mechanisms of neuro-inflammation and demyelination as well as intrinsic protective mechanisms. Here, the authors review current insights into the pathogenesis and immunopathological mechanisms implicated in the development of EAE in NHP.

Multiple Sclerosis

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) characterized by loss of motor and sensory function that results from immune-mediated inflammation, demyelination, and subsequent axonal damage.

Clinically, most MS patients experience recurrent episodes (relapses) of neurological impairment, but in most cases (60–80%) the course of the disease eventually becomes chronic and progressive, leading to cumulative motor, sensory, and visual disability, and cognitive deficits.

The course of the disease is largely unpredictable and its clinical presentation is variable, but its predilection for certain parts of the CNS, which includes the optic nerves, the brain stem, cerebellum, and cervical spinal cord, provides a characteristic constellation of signs and symptoms. Several variants of MS have been nowadays defined with variable immunopathogenesis, course and prognosis. Many new treatments targeting the immune system have shown efficacy in preventing the relapses of MS and have been introduced to its management during the last decade.

The diagnosis of multiple sclerosis and the various related demyelinating syndromes: a critical review

Multiple sclerosis (MS), is a chronic disease of the central nervous system (CNS) characterized by loss of motor and sensory function, that results from immune-mediated inflammation, demyelination and subsequent axonal damage. MS is one of the most common causes of neurological disability in young adults. Several variants of MS (and CNS demyelinating syndromes in general) have been nowadays defined in an effort to increase the diagnostic accuracy, to identify the unique immunopathogenic profile and to tailor treatment in each individual patient. These include the initial events of demyelination defined as clinically or radiologically isolated syndromes (CIS and RIS respectively), acute disseminated encephalomyelitis (ADEM) and its variants (acute hemorrhagic leukoencephalitis-AHL, Marburg variant, and Balo's concentric sclerosis), Schilder's sclerosis, transverse myelitis, neuromyelitis optica (NMO and NMO spectrum of diseases), recurrent isolated optic neuritis and tumefactive demyelination. The differentiation between them is not only a terminological matter but has important implications on their management. For instance, certain patients with MS and prominent immunopathogenetic involvement of B cells and autoantibodies, or with the neuromyelitic variants of demyelination, may not only not respond well but even deteriorate under some of the first-line treatments for MS. The unique clinical and neuroradiological features, along with the immunological biomarkers help to distinguish these cases from classical MS. The use of such immunological and imaging biomarkers, will not only improve the accuracy of diagnosis but also contribute to the identification of the patients with CIS or RIS who, are at greater risk for disability progression (worse prognosis) or, on the contrary, will have a more benign course. This review summarizes in a critical way, the diagnostic criteria (historical and updated) and the definitions/characteristics of MS of the various variants/subtypes of CNS demyelinating syndromes.

Multiple sclerosis in children

The onset of multiple sclerosis (MS) in childhood and adolescence is being increasingly recognized. Relative to MS in adults, little is known about the diagnostic evaluation, clinical course, outcome, and management of MS in children. To remedy some of these deficiencies, pediatric MS clinics have been created in several countries to provide specialized care to, and to study, affected children. Research is currently underway to investigate the pathobiologic features of childhood-onset MS, to study the mechanisms of myelin inflammation and repair, to evaluate patient outcomes collaboratively between the different clinics, and to increase knowledge of pediatric MS for children living with the disease. It is hoped that, through an understanding of the earliest aspects of the MS disease process, critical insights will be gained about the genesis of MS.

Paediatric UK demyelinating disease longitudinal study (PUDDLS)

Background

There is evidence that at least 5% of Multiple sclerosis (MS) cases manifest in childhood. Children with MS present with a demyelinating episode involving single or multiple symptoms prior to developing a second event (usually within two years) to then meet criteria for diagnosis. There is evidence from adult cohorts that the incidence and sex ratios of MS are changing and that children of immigrants have a higher risk for developing MS. A paediatric population should reflect the vanguard of such changes and may reflect trends yet to be observed in adult cohorts. Studying a paediatric population from the first demyelinating event will allow us to test these hypotheses, and may offer further valuable insights into the genetic and environmental interactions in the pathogenesis of MS.

Methods/Design

The Paediatric UK Demyelinating Disease Longitudinal Study (PUDDLS) is a prospective longitudinal observational study which aims to determine the natural history, predictors and outcomes of childhood CNS inflammatory demyelinating diseases. PUDDLS will involve centres in the UK, and will establish a cohort of children affected with a first CNS inflammatory demyelinating event for long-term follow up by recruiting for approximately 5 years. PUDDLS will also establish a biological sample archive (CSF, serum, and DNA), allowing future hypothesis driven research. For example, the future discovery of a biomarker will allow validation within this dataset for the evaluation of novel biomarkers. Patients will also be requested to consent to be contacted in the future. A secondary aim is to collaborate internationally with the International Paediatric Multiple Sclerosis Study Group when future collaborative studies are proposed, whilst sharing a minimal anonymised dataset. PUDDLS is the second of two jointly funded studies. The first (UCID-SS) is an epidemiological surveillance study that already received ethical approvals, and started on the 1st September 2009. There is no direct patient involvement, and UCID-SS aims to determine the UK and Ireland incidence of CNS inflammatory demyelinating disorders in children under 16 years.

Discussion

A paediatric population should reflect the vanguard of MS epidemiological changes and may reflect trends yet to be observed in adult MS cohorts. The restricted window between clinical expression of disease and exposure to environmental factors in children offers a unique research opportunity. Studying a paediatric population from the first demyelinating event will allow us to investigate the changing epidemiology of MS, and may offer further valuable insights into the genetic and environmental interactions in the pathogenesis of MS.

Lethal acute demyelinization with encephalo-myelitis as a complication of cured Cushing's disease

Cushing's disease is usually associated with higher mortality rate, especially from cardiovascular causes. Development or exacerbation of autoimmune or inflammatory diseases is known to occur in patients with hypercortisolism after cure. We report for the first time a 34-year old woman with a psychiatric background, who developed four months after the surgical cure of Cushing's disease an acute disseminated encephalomyelitis (ADEM) presenting initially as a psychiatric illness. We hypothesize that the recent correction of hypercortisolism triggered ADEM and that the atypical presentation, responsible for diagnosis delay, led to the death of this patient.

Fatigue and depression in children with multiple sclerosis and monophasic variants

BACKGROUND

Fatigue is an important symptom in adult multiple sclerosis (MS) and it is likely to occur in children with MS. It is currently unknown whether children who experienced a monophasic inflammatory demyelinating event of the central nervous system in the past also suffer from fatigue.

METHODS

We studied the presence and severity of fatigue in 32 children (18 boys, 14 girls) between 11-17 years old (mean: 14 years, 10 months) with a monophasic inflammatory demyelinating disease (n=22) or definite MS (n=10). This was measured with the Checklist Individual Strength. A score of >or=40 on the severity of fatigue subscale indicated the presence of severe fatigue. We also examined the relation between fatigue and depression (assessed by the Child Depression Inventory). Additionally we measured the health-related quality of life (HRQoL), using the TNO-AZL Child Quality of Life child form. We compared the scores of the MS and monophasic patients with the scores of healthy Dutch children.

RESULTS

The highest scores on the fatigue scales subjective fatigue and physical activity were found in the children with MS. Only 1 of the monophasic patients suffered from severe fatigue in contrast to 4 of the MS patients. In the MS group fatigue and depression were correlated. MS patients experienced a lower HRQoL on the scales locomotor functioning, cognitive functioning and interaction with peers.

CONCLUSION

The occurrence of fatigue is very rare after a monophasic inflammatory demyelinating event in the past. As expected, fatigue occurs more frequent in paediatric MS patients.

Evaluation of the cases with acute disseminated encephalomyelitis

OBJECTIVE

We aimed to describe the epidemiologic, clinical, laboratory features, neuroimaging, treatment, and outcome of children with acute disseminated encephalomyelitis in a cohort study.

METHODS

In this study, twelve children who were diagnosed as acute disseminated encephalomyelitis were reviewed retrospectively. All of the cases were reevaluated with systemic and neurological examinations, serologic tests, cerebrospinal fluid investigations, magnetic resonance imaging.

RESULT

Their age ranged between 2.5 and 16 years. Five of the cases had initial infections. Patients presented most often with motor deficits (75%), secondly with loss of conscious (33%), and seizures (33%). Spinal fluid abnormalities occurred in 41.6%. Cranial, and spinal magnetic resonance imaging (MRI) revealed hyperintense signal changes mainly in basal ganglia and thalamus (58%), cortical and subcortical areas (33) in T2 weighted images. Myelitis was determined in two cases. Six patients were treated with steroid, and 3 were treated with intravenous immunoglobulin. Ten patients recovered completely. We observed relapse in one case and recurrence in two cases. These cases responded well to high dose intravenous prednisolone followed by oral prednisolone for 6 months.

CONCLUSION

Outlook recovery is generally good in acute disseminated encephalomyelitis. Recurrence and neurological deficits are rarely seen. Early treatment of prednisolone is one of the most important factors to determine the prognosis in this disease.

Acute disseminated encephalomyelitis in children: focus on relapsing patients

This study investigated the possible prognostic factors for relapse, and the diagnostic criteria for multiple sclerosis and related disorders, in pediatric acute disseminated encephalomyelitis. The study population comprised 24 Italian children with a mean age at onset of 6.9 years, and a mean follow-up time of 52.8 months (range, 12-180). Clinical, neurophysiologic, spinal-fluid, neuroradiologic, and outcome features were investigated. All patients but 2, who were reclassified as exhibiting clinically isolated syndromes, fulfilled the new classification criteria for acute disseminated encephalomyelitis recently proposed by the International Pediatric Multiple Sclerosis Study Group. Three patients relapsed after 3 months, 2 years, and 8 years, respectively. By the second attack, the diagnosis of multiple sclerosis, as well as of multiphasic disseminated encephalomyelitis, could be rendered using the revised criteria of McDonald et al. Long-term follow-up seemed to confirm a chronic disease course in 2 children. We could not identify features at onset to predict outcomes of patients. However, early in follow-up, the appearance of oligoclonal immunoglobulin G bands in spinal fluid and the persistence of visual-evoked potential abnormalities were associated with poor outcomes.

Probable acute disseminated encephalomyelitis due to Haemophilus influenzae meningitis

We report the case of a 17-year-old male on long-term steroid therapy for minimal lesion glomerulopathy who, after an upper respiratory infection, presented with Haemophilus influenzae type b meningitis. Twenty-four hours later he developed depression of consciousness which progressed to coma and left hemiparesis. Brain magnetic resonance imaging (MRI) revealed multiple lesions (hyperintense on T2 and slightly hypointense on Tl) involving mainly white matter suggestive of inflammation. MRI features were compatible with acute disseminated encephalomyelitis (ADEM), although a differential diagnosis included cerebritis or vasculitis, secondary to bacterial meningitis. The patient was treated with high-dose steroids which resulted in a gradual improvement followed by complete clinical recovery. We propose a diagnosis of ADEM was the best diagnosis because of the radiological features and response to steroids. The occurrence of ADEM associated with acute meningitis, however rare, represents an important diagnostic challenge for the clinician.

Recurrent pseudotumoral hemicerebellitis: neuroimaging findings

We present the case of a 13-year-old girl with pseudotumoral hemicerebellitis that recurred 22 months after the first episode together with conventional MR imaging findings and diffusion-weighted imaging and MR spectroscopy findings. A mirror pattern of involvement was present with the contralateral hemisphere affected in the second episode. Recurrent hemicerebellitis is unique and recognition of the radiological findings allows accurate diagnosis that can be a challenge clinically.

Multiple sclerosis in children: clinical diagnosis, therapeutic strategies, and future directions

The onset of multiple sclerosis (MS) in childhood poses diagnostic and therapeutic challenges, particularly if the symptoms of the first demyelinating event resemble acute disseminated encephalomyelitis (ADEM). MRI is an invaluable diagnostic tool but it lacks the specificity to distinguish ADEM from the first attack of MS. Advanced MRI techniques might have the required specificity to reveal whether the loss of integrity in non-lesional tissue occurs as a fundamental feature of MS. Although the onset of MS in childhood typically predicts a favourable short-term prognosis, some children are severely disabled, either physically or cognitively, and more than 50% are predicted to enter the secondary-progressive phase of the disease by the age of 30 years. Immunomodulatory therapies for MS and their safe application in children can improve long-term prognosis. Genetic and environmental factors, such as viral infection, might be uniquely amenable to study in paediatric patients with MS. Understanding the immunological consequences of these putative exposures will shed light on the early pathological changes in MS.

Acute disseminated encephalomyelitis: an acute hit against the brain

PURPOSE OF REVIEW

In this review, the possible etiology, clinical characteristics, diagnosis, and treatment of acute disseminated encephalomyelitis (ADEM) are discussed. ADEM is a para- or postinfectious autoimmune demyelinating disease of the central nervous system and has been considered a monophasic disease. The highest incidence of ADEM is observed during childhood.

RECENT FINDINGS

Over the last decade, many cases of multiphasic ADEM have been reported. The occurrence of relapses potentially poses a diagnostic dilemma for the treating physician, as it may be difficult to distinguish multiphasic ADEM from multiple sclerosis (MS). Many retrospective patient studies have thus focused on the clinical and paraclinical features of ADEM and have attempted to define specific diagnostic criteria. Additionally, several experimental models have provided insight with respect to the pathogenic relation of an infectious event and subsequent demyelinating autoimmunity.

SUMMARY

Capitalizing on experience based on a large body of well characterized patient data collected both cross-sectionally and longitudinally, pharmacotherapy has been improved and mortality and comorbidities due to ADEM have been reduced. Unfortunately, the pathogenic events that trigger the initial clinical attack, and possibly pave the way for ongoing relapsing disease, remain unknown. Clinically applicable diagnostic criteria are still lacking.

Acute disseminated encephalomyelitis cohort study: prognostic factors for relapse

To date, there is no available epidemiological study about prognostic factors of acute disseminated encephalomyelitis (ADEM) in children, using a cohort of patients with homogenous inclusion criteria. We aimed to evaluate prognostic factors for relapse after ADEM in children. A total of 132 children from the French National KIDSEP Neuropediatric Cohort (mean age at onset: 6+/-3.3 years; mean follow-up: 5.4+/-3.3 years; lost to follow-up: 10%). ADEM diagnosis was considered in a previously healthy patient acutely presenting more than one neurological deficit, change in mental state and MRI alterations including white matter changes. We used multivariate survival analysis (Cox model) evaluating the prognostic value of baseline clinical, biological and MRI covariates, for the occurrence of a second attack. Twenty-four (18%) of included patients had a second attack. An increased risk of relapse was associated with optic neuritis (hazard ratio, 5.23; 95% CI, 2-13.65), familial history of central nervous system inflammatory demyelination (7.79; 1.54-39.5), Barkhof multiple sclerosis (MS) criteria on MRI (2.52; 1.04-6.12) and no neurological sequelae after first attack (3.79; 1.12-12.85). Clinical and MRI prognostic factors for relapse in ADEM may contribute to an early distinction between monophasic and relapsing disease, which may be related to MS.

Acute disseminated encephalomyelitis mimicking late CNS relapse of acute lymphoblastic leukaemia: case report

Background

Acute encephalomyelopathy occurring after an allogeneic bone marrow transplant for leukaemia is a diagnostic emergency. The diagnosis can be challenging since there is a wide set of alternative diagnoses, including opportunistic infections and relapse of the leukaemia.

Case presentation

A 13-year old girl presented with a severe acute myelopathy and encephalopathy. She was in prolonged remission from a central nervous system and bone marrow relapse of an acute lymphoblastic leukaemia, treated with allogeneic bone marrow transplantation. Neuroimaging showed multifocal grey and white matter lesions of demyelinating appearance in the brain and entire spine. Immunophenotyping and cytogenetic investigations of the girl's cerebrospinal fluid lymphocytosis excluded a late central nervous system relapse of her leukaemia. The diagnosis was acute disseminated encephalomyelitis. With standard immunosuppressive therapy, the girl had early cerebral recovery but a prolonged period of recovery from her myelopathy.

Conclusion

Acute disseminated encephalomyelitis should be considered in the differential diagnosis of acute encephalomyelopathy after bone marrow transplantation for leukaemia. Demyelinating syndromes such as acute disseminated encephalomyelitis may be late sequelae of bone marrow transplantation.

Primary necrotizing lymphocytic central nervous system vasculitis due to perforin deficiency in a four-year-old girl

We report the case of a 4-year-old girl who presented with headaches, ataxia, and visual disturbances. Cranial magnetic resonance imaging showed multiple supra- and infratentorial lesions with peripheral contrast enhancement and central necrosis. Brain biopsy revealed necrotizing lymphocytic vasculitis of undetermined etiology. Perforin expression was found to be significantly reduced in the patient's peripheral blood cells, and sequence analysis of the patient's perforin gene showed a compound heterozygous state with 1 nonsense mutation and 2 missense alterations in exon 2. Central nervous system (CNS) vasculitis was thus attributed to the perforin deficiency, and the patient was successfully treated by transplantation of stem cells from an HLA-identical brother. The findings described herein indicate that, even in the absence of classic non-neurologic symptoms of hemophagocytic lymphohistiocytosis, measurement of perforin expression should be one of the diagnostic tests used to identify the cause of unexplained CNS vasculitis, since this may have profound implications regarding therapy.

Acute myelitis in a child: current hypotheses

This report presents the case of a child with atopic dermatitis, who developed progressive muscular weakness and hypotonia of the four limbs. The cervical spinal cord magnetic resonance imaging revealed a C(4) lesion (T(2)-weighted images); the cerebrospinal fluid findings were normal. Treatment with intravenous immunoglobulins and methylprednisolone obtained rapid clinical improvement, and approximately 1 month later the small C(4) lesion disappeared. Various diagnostic hypotheses are discussed: acute myelitis by infective agents, acute disseminated encephalomyelitis, multiphasic disseminated encephalomyelitis, multiple sclerosis, and isolated postinfective myelitis. Another hypothesis relates to atopic myelitis, a form recently described in the Japanese literature, associated with atopic dermatitis, hyperIgEemia, and high levels of specific immunoglobulin E to Dermatophagoides farinae and Dermatophagoides pteronyssinus. This diagnosis is difficult to confirm without biopsy evidence of eosinophilic inflammation.

Isolated bilateral optic neuritis in acute disseminated encephalomyelitis

PURPOSE

We present a 4-year-old girl with isolated visual loss related to a bilateral oedematous optic neuropathy of unknown origin, occurring after an episode of viral illness.

METHODS

A cerebral MRI was performed, showing bilateral enhancement of the optic nerves and bilateral, diffuse, cerebral white matter lesions.

RESULTS

The MRI scan suggested acute disseminated encephalomyelitis. Treatment with intravenous steroids and immunoglobulins resulted in favourable visual recovery.

CONCLUSIONS

Bilateral isolated optic neuritis in childhood may be the only presenting symptom in acute disseminated encephalomyelitis, which requires appropriate evaluation and therapeutic management.

Devastating epileptic encephalopathy in school-aged children (DESC): A pseudo encephalitis

PURPOSE

To describe the characteristics of a previously overlooked devastating epileptic encephalopathy that presents as intractable bilateral perisylvian epilepsy starting with prolonged status epilepticus (SE) in normally developing school-aged children.

METHODS

Retrospective study over 7 years of all normally developing children admitted in our institution for a prolonged SE following non-specific febrile illness with at least one seizure recorded on EEG.

RESULTS

Fourteen children were included at a median age of 7.5 years (4-11) (median follow-up of 4 years (1-7)). Intractable SE lasted 4-60 days (median 30). CSF cell count was normal in five cases and moderately increased in the others. During SE, seizures were recorded in 11 patients and involved temporal lobes in 7; the other 4 patients exhibited perisylvian clinical features with secondary generalization. Intractable epilepsy followed SE in all cases without any latent period. Persisting seizures were recorded in 10 patients and involved temporo-perisylvian regions in 8, frontal regions in 2; 3 others had perisylvian ictal semiology. Spiking was bilateral in 10 cases. MRI showed bilateral hippocampal hypersignal and/or atrophy in 10 cases (extended to the neocortex in 3). All children had major cognitive sequelae. When feasible (six patients), detailed neuropsychology suggested fronto-temporal impairment.

CONCLUSIONS

Among so called grey matter encephalitis patients, we identified a recognizable pattern we propose to call Devastating Epileptic encephalopathy in School-age Children (DESC) that begins with prolonged SE triggered by fever of unknown cause, and persists as intractable perisylvian epilepsy with severe cognitive deterioration.

Treatment of Pediatric Multiple Sclerosis

An increasing number of children and adolescents with multiple sclerosis (MS) are being identified and treated with disease-modifying therapies. Yet, there currently is little experience to guide clinicians. As more rapid diagnosis is made possible with magnetic resonance imaging, the number of pediatric MS patients requiring treatment will increase with time. This review draws on information from adult and pediatric neurology sources and summarizes current available data. Additional research is clearly needed. Nonetheless, there are several treatment principles: 1) establishing the diagnosis by differentiating MS from acute disseminated encephalomyelitis or recurrent acute disseminated encephalomyelitis; 2) emphasizing that there are parallels between adult and pediatric MS regarding the clinical presentation, disease course, and ability to tolerate therapy (the more extensive experience in adult MS can be applied to most pediatric cases); 3) explaining the importance of starting treatment early in the disease course and that these therapies seem well-tolerated in children; 4) providing reassurance that the family is not alone; as approximately 5% of the MS population has symptom onset before age 18 years (experience with pediatric MS is growing and centers with pediatric MS programs exist in other countries and are developing within the United States); and 5) reviewing symptom management and addressing issues such as academic performance that are unique to the pediatric MS subpopulation.