Acute Disseminated Encephalomyelitis and Acute Hemorrhagic Leukoencephalitis Following COVID-19: Systematic Review and Meta-synthesis

BACKGROUND AND OBJECTIVES

Since the onset of the COVID-19 pandemic, a growing number of reports have described cases of acute disseminated encephalomyelitis (ADEM) and acute hemorrhagic leukoencephalitis (AHLE) following infection with COVID-19. Given their relatively rare occurrence, the primary objective of this systematic review was to synthesize their clinical features, response to treatments, and clinical outcomes to better understand the nature of this neurologic consequence of COVID-19 infection.

METHODS

Patients with a history of COVID-19 infection were included if their reports provided adequate detail to confirm a diagnosis of ADEM or AHLE by virtue of clinical features, radiographic abnormalities, and histopathologic findings. Cases purported to be secondary to vaccination against COVID-19 or occurring in the context of a preexisting relapsing CNS demyelinating disease were excluded. Case reports and series were identified via PubMed on May 17, 2021, and 4 additional cases from the authors' hospital files supplemented the systematic review of the literature. Summary statistics were used to describe variables using a complete case analysis approach.

RESULTS

Forty-six patients (28 men, median age 49.5 years, 1/3 >50 years old) were analyzed, derived from 26 case reports or series originating from 8 countries alongside 4 patient cases from the authors' hospital files. COVID-19 infection was laboratory confirmed in 91% of cases, and infection severity necessitated intensive care in 67%. ADEM occurred in 31 cases, whereas AHLE occurred in 15, with a median presenting nadir modified Rankin Scale score of 5 (bedridden). Anti-MOG seropositivity was rare (1/15 patients tested). Noninflammatory CSF was present in 30%. Hemorrhage on brain MRI was identified in 42%. Seventy percent received immunomodulatory treatments, most commonly steroids, IV immunoglobulins, or plasmapheresis. The final mRS score was ≥4 in 64% of patients with adequate follow-up information, including 32% who died.

DISCUSSION

In contrast to ADEM cases from the prepandemic era, reported post-COVID-19 ADEM and AHLE cases were often advanced in age at onset, experienced severe antecedent infection, displayed an unusually high rate of hemorrhage on neuroimaging, and routinely had poor neurologic outcomes, including a high mortality rate. Findings are limited by nonstandardized reporting of cases, truncated follow-up information, and presumed publication bias.

Imagerie de l'encéphalomyélite aiguë disséminée: étude de 22 cas

L'Encéphalomyélite aiguë disséminée (ADEM) est une cause rare d'encéphalite de l'adulte, caractérisée par des lésions inflammatoires de la substance blanche du système nerveux central (SNC). Le tableau clinique initial peut mimer un tableau sévère d'infection du SNC avec fièvre, encéphalopathie, crises convulsives, ou un tableau de sclérose en plaque. Le but de notre travail est de rapporter les caractéristiques épidémiologiques, cliniques, radiologiques, thérapeutiques et évolutives de l'ADEM, aussi évaluer l'apport des séquences IRM dans le diagnostic, le suivi et le pronostic de la maladie. Il s'agit d'une étude rétrospective des dossiers cliniques et radiologiques d'ADEM sur 11 ans (janvier 2006-janvier 2017) portant sur 22 cas suivis au service de neurologie et explorés au niveau du service d'imagerie médicale de l'Hôpital Militaire d'Instruction Mohammed V de Rabat. L'âge moyen des patients était de 35 ans [12-57ans]. Une notion d'infection récente était retrouvée dans 31%, une vaccination récente dans 4%. La symptomatologie était dominée par un déficit neurologique focal avec un pourcentage de 72%. La TDM était normale dans 78%. L'IRM a montré un hyper signal FLAIR de la SB sus et sous tentoriel dans 70%, sans restriction de la diffusion dans la totalité des cas, avec rehaussement des lésions dans 27%, l'atteinte de la moelle cervicale estimait à 68%. L'évolution clinique et radiologique était favorable dans la totalité des cas.

An Adult Case of Recurrent Guillain-Barré Syndrome with Anti-galactocerebroside Antibodies

A 79-year-old woman with a history of Guillain-Barré syndrome (GBS) developed somnolence and tetraparesis after pneumonia. Based on clinical and laboratory findings, she was diagnosed with complications of acute inflammatory demyelinating polyneuropathy (AIDP) and acute disseminated encephalomyelitis (ADEM). Anti-galactocerebroside (Gal-C) IgG antibodies were detected in her serum. Cases of recurrent GBS in patients who are positive for this antibody are extremely rare. The anti-Gal-C IgG antibodies likely played an important role in the pathogenesis of the AIDP and ADEM.

An Adult Case of Anti-Myelin Oligodendrocyte Glycoprotein (MOG) Antibody-associated Multiphasic Acute Disseminated Encephalomyelitis at 33-year Intervals

Acute disseminated encephalomyelitis (ADEM) followed by optic neuritis (ON) has been reported as a distinct phenotype associated with anti-myelin oligodendrocyte protein (MOG) antibody. We herein report the case of a 37-year-old woman who was diagnosed with ADEM at 4 years old of age and who subsequently developed ON followed by recurrent ADEM 33 years after the initial onset. A serum analysis showed anti-MOG antibody positivity. This phenotype has only previously been reported in pediatric cases. Neurologists thus need to be aware that the phenotype may occur in adult patients, in whom it may be assumed to be atypical multiple sclerosis.

Early rehabilitative treatment for pediatric acute disseminated encephalomyelitis: case report

Although the diagnosis of and therapy for acute disseminated encephalomyelitis (ADEM) have been extensively investigated, the role of rehabilitation in modifying its functional outcome has received little attention in the literature so far. We report a case of pediatric ADEM who showed complete functional recovery following early rehabilitative treatment, started in the Intensive Care Unit.

[Pathogenetic mechanisms of demyelinating diseases of the central nervous system in children]

OBJECTIVE

To study cerebrospinal fluid and protein indices characterizing the permeability of the hematoencephalitic barrier and intrathecal immunoglobulin synthesis in children with different course and outcome of demyelinating diseases of the central nervous system.

MATERIAL AND METHODS

We examined 72 children with demyelinating diseases of the central nervous system and 16 children of a control group (without neuroinfections).

RESULTS

Differences in the concentration of myelin basic protein, immunoglobulin G, albumin and immunoglobulin indices in the cerebrospinal fluid were determined depending on acute, prolonged, chronic course of disseminated encephalitis and multiple sclerosis in children. The maximum value of the immunoglobulin index and the intrathecal immunoglobulin synthesis index was identified in multiple sclerosis. The correlations of cerebrospinal fluid indicators and protein factors in the acute period of demyelinating diseases and the formation of neurologic deficiency in the disease outcome were determined that can be used for prognostic purpose.

CONCLUSION

The alterations in the indices obtained in this study can be included in the algorithm of laboratory examination. The results prove the involvement of various mechanisms in the pathogenesis of demyelinating diseases of the central nervous system in children.

Autonomic dysreflexia in acute disseminated encephalomyelitis

Autonomic dysreflexia occurs in patients with spinal cord injury, and is characterized by unbalanced sympathetic discharge, precipitated by noxious stimuli from a site below the spinal cord lesion. An 11-year-old boy with acute disseminated encephalomyelitis and spinal cord involvement manifested episodes of intense flushing and sweating, confined to the head and neck region, and associated with hypertension and tachycardia. His signs improved after changing a partly blocked bladder catheter. The clinical features suggested autonomic dysreflexia. Early recognition of autonomic dysreflexia is important because removal of the trigger precipitating the event may be life-saving.

Meningitis-retention syndrome: first case of urodynamic follow-up

The combination of acute urinary retention and aseptic meningitis has not been well recognized. This combination can be referred to as meningitis-retention syndrome (MRS), when accompanied by no other abnormalities. However, the responsible site of lesions for urinary retention in MRS remains obscure, despite the areflexic detrusor at the time of urinary retention. We recently encountered a man with MRS in whom a urodynamic study was performed twice. In that case, an initially areflexic detrusor became overactive after a 4-month period, suggesting an upper motor neuron bladder dysfunction.

Acute encephalopathy and encephalitis caused by influenza virus infection

PURPOSE OF REVIEW

Influenza-associated acute encephalopathy/encephalitis (IAE) is an uncommon but serious complication with high mortality and neurological sequelae. This review discusses recent progress in IAE research for a better understanding of the disease features, populations, outcomes, diagnosis, and pathogenesis.

RECENT FINDINGS

In recent years, many IAE cases were reported from many countries, including Japan, Canada, Australia, Austria, The Netherlands, United States, Sweden, and other countries and regions. During the novel influenza A/H1N1 pandemic, many IAE cases with A/H1N1 infection in children were reported, particularly in those hospitalized with influenza infection. Pathogenesis of IAE is not fully understood but may involve viral invasion of the CNS, proinflammatory cytokines, metabolic disorders, or genetic susceptibility. An autosomal dominant viral acute necrotizing encephalopathy (ANE) was recently found to have missense mutations in the gene Ran-binding 2 (RANBP2). Another recurrent ANE case following influenza A infection was also reported in a genetically predisposed family with an RANBP2 mutation.

SUMMARY

Although IAE is uncommon, compared with the high incidence of influenza infection, it is severe. However, this complication is not duly recognized by health practitioners. Recent advances highlight the threat of this complication, which will help us to have a better understanding of IAE.

[Background of the new definitions for pediatric multiple sclerosis]

The characteristics of pediatric multiple sclerosis (MS), especially with the onset below ten years of age, are different from those of adult-onset MS. Polysymptomatic and encephalopathic features are frequently observed in pediatric MS. The MRI findings in a half of pediatric MS do not fulfill the McDonald criteria. There are different opinions on the prognosis of pediatric MS. Pediatric patients with the biphasic inflammatory demyelination and the good prognosis has been reported, which was previously classified in MS. For the purpose of distinguishing transient demyelinating syndromes from the lifelong disease, the new definitions for pediatric MS and related disorders were proposed. The surveillance of pediatric MS using the new definitions has been started in Japan.

[Multiple sclerosis or recurrent disseminated encephalomyelitis?]

Two cases of acute demyelinization with recurrent course are described. The problem of differentiation between acute disseminated encephalomyelitis and multiple sclerosis is discussed. Clinical presentations with the prevalence of memory and praxis impairment and large MRI lesions in the subcortical white matter support the diagnosis of acute disseminated encephalomyelitis.

Acute disseminated encephalomyelitis presenting as acute psychotic disorder

A 5 year old boy and a 10 year old girl presented with acute onset of psychotic disorder, which occurred one week after an upper respiratory infection. MRI images of brain were consistent with the diagnosis of acute disseminated encephalomyelitis (ADEM) in both cases. ADEM is one of the differential diagnoses to be considered when acute psychotic disorder occurs during childhood.

[Acute disseminated encephalomyelitis: study of factors involved in a possible development towards multiple sclerosis]

Acute disseminated encephalomyelitis (ADEM) is an uncommon disease characterized by inflammation and demyelination of the central nervous system (CNS). It typically occurs after a viral infection or vaccination and is more frequent in children. Its immediate and longterm prognosis is expected to be good (20% of cases with sequelae). Although ADEM is typically monophasic, occasional relapses may occur. Differential diagnosis, mostly in the early phases, is established with multiple sclerosis (MS), a chronic inflammatory demyelinating disease of the CNS that may have worse prognosis. Traditionally it has been believed that 10% of ADEM patients develop MS. However, this percentage could be higher according to several recently published clinical series. Some clinical and paraclinical patterns are considered to confer risk of developing MS when present in ADEM patients. Our study has aimed to: a) describe a series of 29 patients (22 children and 9 adults) admitted in our hospital and diagnosed of ADEM between 1990 and 2005; b) study those patients considered to have risk patterns of developing MS, and c) compare the child and adult populations of our series. After a median 55 month follow-up, 6 children (27%) and no adults developed MS. In our series, risk patterns for developing MS predicted conversion to MS more accurately in children than in adults. Eight patients (6 children and 2 adults) had sequelae, cognitive in 6 of them. Our work supports that also observed in recent publications: that both conversion to MS or presence of sequelae after an episode of ADEM are more frequent than traditionally considered.

Acute disseminated encephalomyelitis: a report of two fulminant cases and review of literature

Although the prognosis of acute disseminated encephalitis (ADEM) has generally been reported as favorable, in a small subset of patients, fulminant cerebral edema requiring critical care and surgical management may develop. This article presents a 56-year-old woman who developed ADEM and died of central brain herniation secondary to medically intractable cerebral edema. Following this experience, we encountered a 32-year-old man who also developed central brain herniation despite best medical management. We performed an urgent decompressive hemicraniectomy and frontal lobectomy followed by intensive intracranial pressure management. Few recommendations are available to guide neurologists and neurosurgeons in the management of medically intractable cerebral edema of ADEM. In this report, we present our experience with two severe cases of ADEM, review the pertinent literature, and discuss options for improved management of fulminant cases.

A case of acute disseminated encephalomyelitis presenting with vertigo

We report a 37-year-old woman with acute disseminated encephalomyelitis (ADEM) who presented with progressive vertigo. A central nervous system disorder was initially suspected because gaze-evoked torsional nystagmus was observed and electrical nystagmography (ENG) revealed abnormal eye movements with saccadic ocular pursuit and pathological optokinetic nystagmus. Finally ADEM was diagnosed by the clinical symptoms and the characteristic patterns of brain MRI. It is rare for otolaryngologists to examine patients with ADEM. ADEM takes an acute course and can present a grave state and therefore needs early diagnosis, early treatment. We have to keep ADEM in mind in the diagnosis of vertigo.

Acute Disseminated Encephalomyelitis

Acute disseminated encephalomyelitis (ADEM) is a monophasic, demyelinating disease of the central nervous systemthat predominately affects prepubertal children. It is typically characterized by an abrupt onset of neurologic symptoms preceded by an infection or recent immunization. ADEM is a diagnosis of exclusion in many cases, though the differential diagnosis is extensive. An adult female diagnosed with ADEMrepresents an atypical presentation; she was subsequently treated successfully with high-dose steroids. Nursing considerations for patients with ADEM include teaching patients and families about the disease, its clinical course, treatment, and prognosis.

Comparative immunopathogenesis of acute disseminated encephalomyelitis, neuromyelitis optica, and multiple sclerosis

PURPOSE OF REVIEW

Advanced immunopathological techniques hold promise for more precise diagnosis of idiopathic demyelinating diseases of the central nervous system. We review recent progress in differentiating and understanding the disease mechanisms of acute disseminated encephalomyelitis, neuromyelitis optica, and classical multiple sclerosis.

RECENT FINDINGS

Four distinct immunopathological patterns have been described in multiple sclerosis patients, potentially implicating different inflammatory, demyelinating, and apoptotic mechanisms. A specific serum biomarker, neuromyelitis optica immunoglobulin G, is strongly associated with neuromyelitis optica and identifies patients with severe optic nerve and spinal cord lesions with specific pathological features such as eosinophilic and neutrophilic inflammatory infiltrates, necrosis, vascular hyalinization, and extensive vasculocentric immunoglobulin and complement deposition. This biomarker targets the water channel aquaporin-4, which is lost in neuromyelitis optica lesions. Acute disseminated encephalomyelitis still has no validated clinical diagnostic criteria but its perivenous pathological findings distinguish it from multiple sclerosis and neuromyelitis optica.

SUMMARY

The clinically heterogeneous group of idiopathic inflammatory demyelinating diseases of the central nervous system is characterized by several immunopathological patterns that suggest the involvement of diverse pathogenic effector mechanisms. Future advances in experimental pathology, immunology, molecular genetics, and neuroimaging, as well as the discovery of specific biomarkers, will more precisely define these disorders and lead to better targeted therapies.

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

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated inflammatory disorder of the CNS characterized by a widespread demyelination that predominantly involves the white matter of the brain and spinal cord. The condition is usually precipitated by a viral infection or vaccination. The presenting features include an acute encephalopathy with multifocal neurologic signs and deficits. Children are preferentially affected. In the absence of specific biologic markers, the diagnosis of ADEM is still based on the clinical and radiologic features. Although ADEM usually has a monophasic course, recurrent or multiphasic forms have been reported, raising diagnostic difficulties in distinguishing these cases from multiple sclerosis (MS). The International Pediatric MS Study Group proposes uniform definitions for ADEM and its variants. We discuss some of the difficulties in the interpretation of available literature due to the different terms and definitions used. In addition, this review summarizes current knowledge of the main aspects of ADEM, including its clinical and radiologic diagnostic features, epidemiology, pathogenesis, and outcome. An overview of ADEM treatment in children is provided. Finally, the controversies surrounding pediatric MS and ADEM are addressed.

Central brain herniation secondary to fulminant acute disseminated encephalomyelitis: implications for neurosurgical management

✓ Acute disseminated encephalomyelitis (ADEM), also known as postinfectious encephalomyelitis, is an immunologically mediated demyelinating disorder affecting the central nervous system that typically occurs after infection or vaccination. The prognosis of ADEM is generally favorable. In a small subset of patients with ADEM, however, fulminant cerebral edema requiring neurosurgical intervention will develop. Few recommendations are available to help the neurosurgeon in dealing with such cases. In this report, the authors present the case of a patient with ADEM in whom central brain herniation developed secondary to medically intractable cerebral edema. The authors review the salient features of the disease and suggest a role for neurosurgeons in cases of fulminant ADEM.

Evolution of stimulus-induced rhythmic EEG discharges in three patients with encephalopathy

Stimulus-induced rhythmic EEG discharges (SIRDs) is a recently reported phenomenon in critically ill patients and little is known about their evolution. We found SIRDs in three patients with encephalopathy and followed them with serial EEGs. SIRDs appeared between 4 and 13 days after the onset of illness and persisted for 2-3 days. The discharges were elicited by tactile or nociceptive stimuli and lasted for 20-120 s. They were detected in 2/6, 1/3 and 2/11 EEGs performed between 9 and 32, 2 and 4 and 3 and 15 days, respectively, after the onset of illness. Their morphology varied: blunt triphasic waves, rhythmic delta activity and rhythmic sharp wave complexes. The background EEG activity was slowed or suppressed in all. One patient had acute disseminated encephalomyelitis (ADEM) with good recovery and the other two had fatal hypoxic ischemic encephalopathy. SIRDs appear to be a transient phenomena occurring in patients with encephalopathy, appearing hours to few days after the onset of illness. This is the first report of SIRDs in ADEM. Serial EEGs and repeated testing of EEG response to tactile and nociceptive stimuli is required for their detection. Larger number of patients with SIRDs need to be studied to assess their prognostic significance.

Spectrum of neurological diseases associated with antibodies to minor gangliosides GM1b and GalNAc-GD1a

The authors reported the neurological disease spectrum associated with autoantibodies against minor gangliosides GM1b and GalNAc-GD1a. IgG and IgM antibody reactivity against gangliosides GM1, GM2, GM1b, GD1a, GalNAc-GD1a and GQ1b was investigated in sera from 7000 consecutive patients who had various neurological conditions. The clinical diagnoses for 456 anti-GM1b-positive patients were Guillain-Barré syndrome (GBS, 71%), atypical GBS with preserved deep tendon reflexes (12%), Fisher syndrome (10%), Bickerstaff's brainstem encephalitis (2%), ataxic GBS (2%) and acute ophthalmoparesis (1%). For 193 anti-GalNAc-GD1a-positive patients, the diagnoses were GBS (70%), atypical GBS (16%), Fisher syndrome (10%) and Bickerstaff's brainstem encephalitis (3%). Of the patients with GBS or atypical GBS, 28% of 381 anti-GM1b-positive and 31% of 166 anti-GalNAc-GD1a-positive patients had neither anti-GM1 nor anti-GD1a antibodies. Of those patients with Fisher syndrome, Bickerstaff's brainstem encephalitis, ataxic GBS or acute ophthalmoparesis, 33% of 67 anti-GM1b-positive, and 52% of 25 anti-GalNAc-GD1a-positive patients had no anti-GQ1b antibodies. Autoantibodies against GM1b and GalNAc-GD1a are associated with GBS, Fisher syndrome and related conditions. These antibodies should provide useful serological markers for identifying patients who have atypical GBS with preserved deep tendon reflexes, ataxic GBS, Bickerstaff's brainstem encephalitis or acute ophthalmoparesis, especially for those who have no antibodies to GM1, GD1a or GQ1b. A method to prepare GM1b was developed.

Infection-associated encephalopathies: their investigation, diagnosis, and treatment

Reduced level of consciousness is a common clinical finding in acutely sick patients. In the majority of cases a cause for the encephalopathy is readily identifiable,whilst in a minority the aetiology is more difficult to ascertain. Frequently the onset of encephalopathy is associated with, or follows, infection. The mechanisms through which infection leads to encephalopathy are diverse. They range from direct microbial invasion of the brain or its supporting structures, to remote, infection-triggered mechanisms such as acute disseminated encephalomyelitis. Most common however, is the encephalopathy caused through a remote effect of systemic sepsis-septic encephalopathy. This article discusses the clinical presentation and underlying pathogeneses of the acute encephalopathies associated with infection, aiming to aid both their recognition and treatment.

Aseptic meningo-radiculo-encephalitis presenting initially with urinary retention: a variant of acute disseminated encephalomyelitis

We report three male patients with aseptic meningoencephalo- radiculitis presenting with acute urinary retention. Viral antibody titers for herpes types I and II and the PCR studies were negative. The cerebrospinal fluid revealed elevated myelin basic protein. The serum antibodies against a panel of gangliosides, some of which are known to be associated with acquired demyelinating neuropathies, were all negative. The magnetic resonance imaging (MRI) studies revealed spotty T2 high intensities in the basal ganglia, thalamus and brainstem in two patients. In one patient,meningeal gadolinium enhancement of the conus and cauda equina of the spinal cord was recognized. On urodynamic studies, all patients showed features of atonic bladder with or without detrusor hyperactivity. They were treated conservatively without using steroids or immunoglobulins, and made a remarkable functional recovery with the disappearance of abnormal MRI findings.However, all three were left with erectile dysfunction, and two continued to use self-intermittent catheterization at more than 3-year follow-up. There was no recurrence of symptoms. The underlying causes remain unclear, though they may represent a variant of acute disseminated encephalomyelitis.

The differential diagnosis of acute transverse myelitis

The clinical and paraclinical characteristics of acute transverse myelitis (ATM) were analyzed in 31 patients. In some patients there was clinical evidence of complete transection, in others of only partial lesions. Magnetic resonance imaging (MRI) in the acute phase in the first group was normal, but showed cord atrophy subsequently. It is probable that the clinical picture was due to parenchymatous neuronal lesions, analogous to those of axonal polyneuropathy. In the patients with incomplete transverse lesions, the most common finding was demyelination. In the patients with circumscribed demyelinating lesions, the symptoms and MRI were suggestive of clinically isolated syndromes (CIS) predictive of multiple sclerosis (MS). Extensive demyelination was indicative of acute disseminated encephalomyelitis (ADEM) due to hyperergic vasculopathy or various forms of chronic vasculitis. In two patients with variable clinical symptoms, a vascular malformation was the cause of the clinical presentation, and in one patient demyelination was due to the disc compression.

"Burst and slow complexes" in nonconvulsive epileptic status

Generalized 1Hz, burst-and-slow-wave complexes were observed in a comatosed patient with acute disseminated encephalomyelitis (ADEM) when she showed extremely intractable, generalized convulsions and fragmented myoclonus in the whole body. Two types of short-latency SEPs were obtained separately during the burst and slow phase of the EEG (SEP-burst and SEP-slow, respectively), which showed a two fold greater amplitude of N20 in the former than in the latter. This suggests enhanced responsiveness to the peripheral stimuli during the burst phase as compared with the slow phase. CSF and serum were positive for autoantibodies to NMDA receptors. The "burst and slow complexes" reported here are considered to be an atypical EEG pattern of a generalized epileptic phenomenon.

The pathology of multiple sclerosis: evidence for heterogeneity

The idiopathic inflammatory demyelinating diseases (IIDDs) consist of a broad spectrum of disorders that vary in their clinical course, regional distribution, and pathology. Though pathology of these demyelinating disorders demonstrates extensive interindividual heterogeneity, there is notable homogeneity within individual patients. The relation between the diverse underlying pathology of IIDDs and the various clinical, paraclinical, and radiological findings is unclear. Finding less-invasive clinical or paraclinical surrogate markers, which accurately and reliably predict the underlying distinct pathologies within the family of IIDDs, can potentially guide future therapies that better target specific pathogenic mechanisms.

Postinfectious inflammatory disorders: Subgroups based on prospective follow-up

BACKGROUND

Acute disseminated encephalomyelitis (ADEM) refers to a monophasic acute multifocal inflammatory CNS disease. However, both relapsing and site-restricted variants, possibly associated with peripheral nervous system (PNS) involvement, are also observed, and a systematic classification is lacking.

OBJECTIVE

To describe a cohort of postinfectious ADEM patients, to propose a classification based on clinical and instrumental features, and to identify subgroups of patients with different prognostic factors.

METHODS

Inpatients of a Neurologic and Infectious Disease Clinic affected by postinfectious CNS syndrome consecutively admitted over 5 years were studied.

RESULTS

Of 75 patients enrolled, 60 fulfilled criteria for ADEM after follow-up lasting from 24 months to 7 years. Based on lesion distribution, patients were classified as encephalitis (20%), myelitis (23.3%), encephalomyelitis (13.3%), encephalomyeloradiculoneuritis (26.7%), and myeloradiculoneuritis (16.7%). Thirty patients (50%) had a favorable outcome. Fifteen patients (25%) showed a relapsing course. Poor outcome was related with older age at onset, female gender, elevated CSF proteins, and spinal cord and PNS involvement. All but two patients received high-dose steroids as first-line treatment, with a positive response in 39 (67%). Ten of 19 nonresponders (53%) benefited from high-dose IV immunoglobulin; 9 of 10 had PNS involvement. The data were not controlled.

CONCLUSIONS

A high prevalence of "atypical variants" was found in this series, with site-restricted damage or additional peripheral nervous system (PNS) involvement. Prognosis and response to steroids were generally good, except for some patient subgroups. In patients with PNS involvement and steroid failure, a favorable effect of IV immunoglobulin was observed.

Role of microglia in multiple sclerosis

Microglia are the resident macrophages of the nervous system. They serve to protect and preserve neuronal cells from pathogens and facilitate recovery from metabolic insults. In addition, they appear to play a role in the neuropathology of noninfectious inflammatory disorders of the central nervous system, especially those that are autoimmune. Presentation of neural autoantigens to autoreactive T cells by microglia and the attendant secretion of proinflammatory cytokines are thought to facilitate the inflammatory process in diseases such as multiple sclerosis. They also serve as scavengers of damaged myelin following death of oligodendrocytes and the destruction of myelin and may, therefore, promote recovery of myelin damaged by the inflammatory insult. This review examines the current controversies on the pathology of multiple sclerosis and the role played by microglia in the development of central nervous system demyelination.

[Acute disseminated encephalomyelitis. Pathogenesis, diagnosis, treatment, and prognosis]

Acute disseminated encephalomyelitis (ADEM) is typically a monophasic, demyelinating disease of the CNS that predominantly affects children. Typically, its clinical symptoms follow an infection or vaccination. In this regard, numerous viral and bacterial pathogens as well as several vaccinations have been associated with ADEM. Studies from animal models suggest that primary and secondary autoimmune responses may contribute to CNS inflammation and demyelination in ADEM. The diagnosis of ADEM is strongly suggested by a close temporal relationship between a viral infection or immunization and the onset of neurologic symptoms, and it is supported by extensive, multifocal, subcortical white-matter disease on brain magnetic resonance imaging. While mild lymphocytic pleocytosis and elevated proteins are detectable in the CSF in ADEM, oligoclonal bands are not always present. Treatment of this disorder consists of anti-inflammatory and immunosuppressive therapies, and the prognosis is generally considered favorable.

Postinfectious immune-mediated encephalitis after pediatric herpes simplex encephalitis

We report a 3-year-old patient who presented a secondary acute neurological deterioration clinically characterized by a partial Kluver-Bucy syndrome, 1 month after the onset of herpes simplex encephalitis. This episode is unlikely due to continuation or resumption of cerebral viral replication but might be related to an immune-inflammatory process. In children, postinfectious immune-mediated encephalitis occurring after HSE are usually clinically characterized by choreoathetoid movements. This type of movement disorder was, however, not observed in this patient. On the basis of this case and a review of the literature, we hypothesize the existence of a spectrum of secondary immune-mediated process triggered by herpes simplex virus cerebral infection ranging from asymptomatic cases with diffuse white matter involvement to secondary acute neurological deteriorations with or without extrapyramidal features.

Childhood acute disseminated encephalomyelitis presenting as Foix-Chavany-Marie syndrome

A 10-year-old boy presented with anarthria and bilateral central faciolinguovelopharyngeomasticatory paralysis with "automatic voluntary dissociation" suggestive of Foix-Chavany-Marie syndrome or anterior opercular syndrome following a nonspecific upper respiratory infection. Brain magnetic resonance imaging revealed bilateral subcortical perisylvian demyelination in addition to multiple subcortical white-matter demyelination. The clinicoradiologic picture suggested acute disseminated encephalomyelitis. The child recovered completely following intravenous methylprednisolone and intravenous immunoglobulin therapy. This is the first report of anterior opercular syndrome in childhood acute disseminated encephalomyelitis.

Evidence of axonal damage in human acute demyelinating diseases

Substantial axon damage, detected by immunostaining for beta amyloid precursor protein (betaAPP) has been demonstrated in acute demyelinating lesions in multiple sclerosis.

AIMS

The present study aimed to determine if this was also the case in the other human acute demyelinating diseases, acute hemorrhagic leucoencephalitis (AHLE), acute disseminated encephalomyelitis (ADEM) and central pontine myelinolysis (CPM).

METHODS

BetaAPP immunostaining was used as a marker of axonal damage in autopsy material from these conditions.

RESULTS

Axonal damage was detected in all these conditions. Its extent varied within and between them. Axonal damage was largely confined to tissue adjacent to veins and venules in AHLE and ADEM but was unrelated to proximity to these vessels in CPM.

CONCLUSION

Substantial axon damage occurs in fatal cases of AHLE, ADEM and CPM.