Acute disseminated encephalomyelitis | |
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Other names | Acute demyelinating encephalomyelitis |
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Fulminating ADEM showing many lesions. The patient survived, but remained in a persistent vegetative state | |
Specialty | Neurology ![]() |
Acute disseminated encephalomyelitis (ADEM), or acute demyelinating encephalomyelitis, is a rare autoimmune disease marked by a sudden, widespread attack of inflammation in the brain and spinal cord. As well as causing the brain and spinal cord to become inflamed, ADEM also attacks the nerves of the central nervous system and damages their myelin insulation, which, as a result, destroys the white matter. The cause is often a trigger such as from viral infection or vaccinations. [1] [2] [3] [4] [5] [6]
ADEM's symptoms resemble the symptoms of multiple sclerosis (MS), so the disease itself is sorted into the classification of the multiple sclerosis borderline diseases. However, ADEM has several features that distinguish it from MS. [7] Unlike MS, ADEM occurs usually in children and is marked with rapid fever, although adolescents and adults can get the disease too. ADEM consists of a single flare-up whereas MS is marked with several flare-ups (or relapses), over a long period of time. Relapses following ADEM are reported in up to a quarter of patients, but the majority of these 'multiphasic' presentations following ADEM likely represent MS. [8] ADEM is also distinguished by a loss of consciousness, coma and death, which is very rare in MS, except in severe cases.
It affects about 8 per 1,000,000 people per year. [9] Although it occurs in all ages, most reported cases are in children and adolescents, with the average age around 5 to 8 years old. [10] [11] [12] [13] The disease affects males and females almost equally. [14] ADEM shows seasonal variation with higher incidence in winter and spring months which may coincide with higher viral infections during these months. [13] The mortality rate may be as high as 5%; however, full recovery is seen in 50 to 75% of cases with increase in survival rates up to 70 to 90% with figures including minor residual disability as well. [15] The average time to recover from ADEM flare-ups is one to six months.
ADEM produces multiple inflammatory lesions in the brain and spinal cord, particularly in the white matter. Usually these are found in the subcortical and central white matter and cortical gray-white junction of both cerebral hemispheres, cerebellum, brainstem, and spinal cord, [16] but periventricular white matter and gray matter of the cortex, thalami and basal ganglia may also be involved.
When a person has more than one demyelinating episode of ADEM, the disease is then called recurrent disseminated encephalomyelitis [17] or multiphasic disseminated encephalomyelitis [18] (MDEM). Also, a fulminant course in adults has been described. [19]
ADEM has an abrupt onset and a monophasic course. Symptoms usually begin 1–3 weeks after infection. Major symptoms include fever, headache, nausea and vomiting, confusion, vision impairment, drowsiness, seizures and coma. Although initially the symptoms are usually mild, they worsen rapidly over the course of hours to days, with the average time to maximum severity being about four and a half days. [20] Additional symptoms include hemiparesis, paraparesis, and cranial nerve palsies. [21]
Neurological symptoms were the main presentation of COVID-19, which did not correlate with the severity of respiratory symptoms. The high incidence of ADEM with hemorrhage is striking. Brain inflammation is likely caused by an immune response to the disease rather than neurotropism. CSF analysis was not indicative of an infectious process, neurological impairment was not present in the acute phase of the infection, and neuroimaging findings were not typical of classical toxic and metabolic disorders. The finding of bilateral periventricular relatively asymmetrical lesions allied with deep white matter involvement, that may also be present in cortical gray-white matter junction, thalami, basal ganglia, cerebellum, and brainstem suggests an acute demyelination process. [22] Additionally, hemorrhagic white matter lesions, clusters of macrophages related to axonal injury and ADEM-like appearance were also found in subcortical white matter. [23]
Since the discovery of the anti-MOG specificity against multiple sclerosis diagnosis [24] it is considered that ADEM is one of the possible clinical causes of anti-MOG associated encephalomyelitis. [25]
About how the anti-MOG antibodies appear in the patients serum there are several theories:
The term ADEM has been inconsistently used at different times. [43] Currently, the commonly accepted international standard for the clinical case definition is the one published by the International Pediatric MS Study Group, revision 2007. [44]
Given that the definition is clinical, it is currently unknown if all the cases of ADEM are positive for anti-MOG autoantibody; in any case, it appears to be strongly related to ADEM diagnosis. [25]
While ADEM and MS both involve autoimmune demyelination, they differ in many clinical, genetic, imaging, and histopathological aspects. [14] [45] Some authors consider MS and its borderline forms to constitute a spectrum, differing only in chronicity, severity, and clinical course, [46] [47] while others consider them discretely different diseases. [6]
Typically, ADEM appears in children following an antigenic challenge and remains monophasic. Nevertheless, ADEM does occur in adults, [8] [12] and can also be clinically multiphasic. [48]
Problems for differential diagnosis increase due to the lack of agreement for a definition of multiple sclerosis. [49] If MS were defined only by the separation in time and space of the demyelinating lesions as McDonald did, [50] it would not be enough to make a difference, as some cases of ADEM satisfy these conditions. Therefore, some authors propose to establish the dividing line as the shape of the lesions around the veins, being therefore "perivenous vs. confluent demyelination". [49] [51]
The pathology of ADEM is very similar to that of MS with some differences. The pathological hallmark of ADEM is perivenous inflammation with limited "sleeves of demyelination". [52] [14] Nevertheless, MS-like plaques (confluent demyelination) can appear [53]
Plaques in the white matter in MS are sharply delineated, while the glial scar in ADEM is smooth. Axons are better preserved in ADEM lesions. Inflammation in ADEM is widely disseminated and ill-defined, and finally, lesions are strictly perivenous, while in MS they are disposed around veins, but not so sharply. [54]
Nevertheless, the co-occurrence of perivenous and confluent demyelination in some individuals suggests pathogenic overlap between acute disseminated encephalomyelitis and multiple sclerosis and misclassification even with biopsy [51] or even postmortem [53] ADEM in adults can progress to MS [12]
When the person has more than one demyelinating episode of ADEM, the disease is then called recurrent disseminated encephalomyelitis or multiphasic disseminated encephalomyelitis [18] (MDEM).
It has been found that anti-MOG auto-antibodies are related to this kind of ADEM [55]
Another variant of ADEM in adults has been described, also related to anti-MOG auto-antibodies, has been named fulminant disseminated encephalomyelitis, and it has been reported to be clinically ADEM, but showing MS-like lesions on autopsy. [19] It has been classified inside the anti-MOG associated inflammatory demyelinating diseases. [56]
Acute hemorrhagic leukoencephalitis (AHL, or AHLE), acute hemorrhagic encephalomyelitis (AHEM), acute necrotizing hemorrhagic leukoencephalitis (ANHLE), Weston-Hurst syndrome, or Hurst's disease, is a hyperacute and frequently fatal form of ADEM. AHL is relatively rare (less than 100 cases have been reported in the medical literature as of 2006 [update] ), [57] it is seen in about 2% of ADEM cases, [20] and is characterized by necrotizing vasculitis of venules and hemorrhage, and edema. [58] Death is common in the first week [59] and overall mortality is about 70%, [57] but increasing evidence points to favorable outcomes after aggressive treatment with corticosteroids, immunoglobulins, cyclophosphamide, and plasma exchange. [29] About 70% of survivors show residual neurological deficits, [58] but some survivors have shown surprisingly little deficit considering the extent of the white matter affected. [59]
This disease has been occasionally associated with ulcerative colitis and Crohn's disease, malaria, [60] sepsis associated with immune complex deposition, methanol poisoning, and other underlying conditions. Also anecdotal association with MS has been reported [61]
Laboratory studies that support diagnosis of AHL are: peripheral leukocytosis, cerebrospinal fluid (CSF) pleocytosis associated with normal glucose and increased protein. On magnetic resonance imaging (MRI), lesions of AHL typically show extensive T2-weighted and fluid-attenuated inversion recovery (FLAIR) white matter hyperintensities with areas of hemorrhages, significant edema, and mass effect. [62]
No controlled clinical trials have been conducted on ADEM treatment, but aggressive treatment aimed at rapidly reducing inflammation of the CNS is standard. The widely accepted first-line treatment is high doses of intravenous corticosteroids, [63] such as methylprednisolone or dexamethasone, followed by 3–6 weeks of gradually lower oral doses of prednisolone. Patients treated with methylprednisolone have shown better outcomes than those treated with dexamethasone. [20] Oral tapers of less than three weeks duration show a higher chance of relapsing, [11] [18] and tend to show poorer outcomes.[ citation needed ] Other anti-inflammatory and immunosuppressive therapies have been reported to show beneficial effect, such as plasmapheresis, high doses of intravenous immunoglobulin (IVIg), [63] [64] mitoxantrone and cyclophosphamide. These are considered alternative therapies, used when corticosteroids cannot be used or fail to show an effect.[ citation needed ]
There is some evidence to suggest that patients may respond to a combination of methylprednisolone and immunoglobulins if they fail to respond to either separately [65] In a study of 16 children with ADEM, 10 recovered completely after high-dose methylprednisolone, one severe case that failed to respond to steroids recovered completely after IV Ig; the five most severe cases – with ADAM and severe peripheral neuropathy – were treated with combined high-dose methylprednisolone and immunoglobulin, two remained paraplegic, one had motor and cognitive handicaps, and two recovered. [63] A recent review of IVIg treatment of ADEM (of which the previous study formed the bulk of the cases) found that 70% of children showed complete recovery after treatment with IVIg, or IVIg plus corticosteroids. [66] A study of IVIg treatment in adults with ADEM showed that IVIg seems more effective in treating sensory and motor disturbances, while steroids seem more effective in treating impairments of cognition, consciousness and rigor. [64] This same study found one subject, a 71-year-old man who had not responded to steroids, that responded to an IVIg treatment 58 days after disease onset.[ citation needed ]
Full recovery is seen in 50 to 70% of cases, ranging to 70 to 90% recovery with some minor residual disability (typically assessed using measures such as mRS or EDSS), average time to recover is one to six months. [15] The mortality rate may be as high as 5–10%. [15] [67] Poorer outcomes are associated with unresponsiveness to steroid therapy, unusually severe neurological symptoms, or sudden onset. Children tend to have more favorable outcomes than adults, and cases presenting without fevers tend to have poorer outcomes. The latter effect may be due to either protective effects of fever, or that diagnosis and treatment is sought more rapidly when fever is present. [68]
ADEM can progress to MS. It will be considered MS if some lesions appear in different times and brain areas [69]
Residual motor deficits are estimated to remain in about 8 to 30% of cases, the range in severity from mild clumsiness to ataxia and hemiparesis. [29]
Patients with demyelinating illnesses, such as MS, have shown cognitive deficits even when there is minimal physical disability. [70] Research suggests that similar effects are seen after ADEM, but that the deficits are less severe than those seen in MS. A study of six children with ADEM (mean age at presentation 7.7 years) were tested for a range of neurocognitive tests after an average of 3.5 years of recovery. [71] All six children performed in the normal range on most tests, including verbal IQ and performance IQ, but performed at least one standard deviation below age norms in at least one cognitive domain, such as complex attention (one child), short-term memory (one child) and internalizing behaviour/affect (two children). Group means for each cognitive domain were all within one standard deviation of age norms, demonstrating that, as a group, they were normal. These deficits were less severe than those seen in similar aged children with a diagnosis of MS. [72]
Another study compared nineteen children with a history of ADEM, of which 10 were five years of age or younger at the time (average age 3.8 years old, tested an average of 3.9 years later) and nine were older (mean age 7.7y at time of ADEM, tested an average of 2.2 years later) to nineteen matched controls. [73] Scores on IQ tests and educational achievement were lower for the young onset ADEM group (average IQ 90) compared to the late onset (average IQ 100) and control groups (average IQ 106), while the late onset ADEM children scored lower on verbal processing speed. Again, all groups means were within one standard deviation of the controls, meaning that while effects were statistically reliable, the children were as a whole, still within the normal range. There were also more behavioural problems in the early onset group, although there is some suggestion that this may be due, at least in part, to the stress of hospitalization at a young age. [74] [75]
The relationship between ADEM and anti-MOG associated encephalomyelitis is currently under research. A new entity called MOGDEM has been proposed. [76]
About animal models, the main animal model for MS, experimental autoimmune encephalomyelitis (EAE) is also an animal model for ADEM. [77] Being an acute monophasic illness, EAE is far more similar to ADEM than MS. [78]
Optic neuritis describes any condition that causes inflammation of the optic nerve; it may be associated with demyelinating diseases, or infectious or inflammatory processes.
Transverse myelitis (TM) is a rare neurological condition wherein the spinal cord is inflamed. The adjective transverse implies that the spinal inflammation (myelitis) extends horizontally throughout the cross section of the spinal cord; the terms partial transverse myelitis and partial myelitis are sometimes used to specify inflammation that affects only part of the width of the spinal cord. TM is characterized by weakness and numbness of the limbs, deficits in sensation and motor skills, dysfunctional urethral and anal sphincter activities, and dysfunction of the autonomic nervous system that can lead to episodes of high blood pressure. Signs and symptoms vary according to the affected level of the spinal cord. The underlying cause of TM is unknown. The spinal cord inflammation seen in TM has been associated with various infections, immune system disorders, or damage to nerve fibers, by loss of myelin. As opposed to leukomyelitis which affects only the white matter, it affects the entire cross-section of the spinal cord. Decreased electrical conductivity in the nervous system can result.
Multiple sclerosis (MS) is an autoimmune disease in which the insulating covers of nerve cells in the brain and spinal cord are damaged. This damage disrupts the ability of parts of the nervous system to transmit signals, resulting in a range of signs and symptoms, including physical, mental, and sometimes psychiatric problems. Specific symptoms can include double vision, vision loss, eye pain, muscle weakness, and loss of sensation or coordination. MS takes several forms, with new symptoms either occurring in isolated attacks or building up over time. In the relapsing forms of MS, between attacks, symptoms may disappear completely, although some permanent neurological problems often remain, especially as the disease advances. In the progressive forms of MS, bodily function slowly deteriorates and disability worsens once symptoms manifest and will steadily continue to do so if the disease is left untreated.
Encephalomyelitis is inflammation of the brain and spinal cord. Various types of encephalomyelitis include:
Neuromyelitis optica spectrum disorders (NMOSD) are a spectrum of autoimmune diseases characterized by acute inflammation of the optic nerve and the spinal cord (myelitis). Episodes of ON and myelitis can be simultaneous or successive. A relapsing disease course is common, especially in untreated patients.
Myelin oligodendrocyte glycoprotein (MOG) is a glycoprotein believed to be important in the myelination of nerves in the central nervous system (CNS). In humans this protein is encoded by the MOG gene. It is speculated to serve as a necessary "adhesion molecule" to provide structural integrity to the myelin sheath and is known to develop late on the oligodendrocyte.
Experimental autoimmune encephalomyelitis, sometimes experimental allergic encephalomyelitis (EAE), is an animal model of brain inflammation. It is an inflammatory demyelinating disease of the central nervous system (CNS). It is mostly used with rodents and is widely studied as an animal model of the human CNS demyelinating diseases, including multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM). EAE is also the prototype for T-cell-mediated autoimmune disease in general.
Multiple sclerosis is an inflammatory demyelinating disease of the CNS in which activated immune cells invade the central nervous system and cause inflammation, neurodegeneration, and tissue damage. The underlying cause is currently unknown. Current research in neuropathology, neuroimmunology, neurobiology, and neuroimaging, together with clinical neurology, provide support for the notion that MS is not a single disease but rather a spectrum.
Multiple sclerosis and other demyelinating diseases of the central nervous system (CNS) produce lesions and glial scars or scleroses. They present different shapes and histological findings according to the underlying condition that produces them.
Susac's syndrome is a very rare form of microangiopathy characterized by encephalopathy, branch retinal artery occlusions and hearing loss. The cause is unknown but it is theorized that antibodies are produced against endothelial cells in tiny arteries which leads to damage and the symptoms related to the illness. Despite this being an extremely rare disease, there are four registries collecting data on the illness; two are the United States, one in Germany, and one in Portugal.
Inflammatory demyelinating diseases (IDDs), sometimes called Idiopathic (IIDDs) due to the unknown etiology of some of them, are a heterogenous group of demyelinating diseases - conditions that cause damage to myelin, the protective sheath of nerve fibers - that occur against the background of an acute or chronic inflammatory process. IDDs share characteristics with and are often grouped together under Multiple Sclerosis. They are sometimes considered different diseases from Multiple Sclerosis, but considered by others to form a spectrum differing only in terms of chronicity, severity, and clinical course.
Baló's concentric sclerosis is a disease in which the white matter of the brain appears damaged in concentric layers, leaving the axis cylinder intact. It was described by József Mátyás Baló who initially named it "leuko-encephalitis periaxialis concentrica" from the previous definition, and it is currently considered one of the borderline forms of multiple sclerosis.
Marburg acute multiple sclerosis, also known as Marburg multiple sclerosis or acute fulminant multiple sclerosis, is considered one of the multiple sclerosis borderline diseases, which is a collection of diseases classified by some as MS variants and by others as different diseases. Other diseases in this group are neuromyelitis optica (NMO), Balo concentric sclerosis, and Schilder's disease. The graver course is one form of malignant multiple sclerosis, with patients reaching a significant level of disability in less than five years from their first symptoms, often in a matter of months.
Research in multiple sclerosis may find new pathways to interact with the disease, improve function, curtail attacks, or limit the progression of the underlying disease. Many treatments already in clinical trials involve drugs that are used in other diseases or medications that have not been designed specifically for multiple sclerosis. There are also trials involving the combination of drugs that are already in use for multiple sclerosis. Finally, there are also many basic investigations that try to understand better the disease and in the future may help to find new treatments.
Tumefactive multiple sclerosis is a condition in which the central nervous system of a person has multiple demyelinating lesions with atypical characteristics for those of standard multiple sclerosis (MS). It is called tumefactive as the lesions are "tumor-like" and they mimic tumors clinically, radiologically and sometimes pathologically.
Malignant multiple sclerosis is used to describe MS patients who reach significant level of disability in a short period of time. Malignant MS cases are not common, less than 5% of patients with MS experience this type of progression.
Current standards for diagnosing multiple sclerosis (MS) are based on the 2018 revision of McDonald criteria. They rely on MRI detection of demyelinating lesions in the CNS, which are distributed in space (DIS) and in time (DIT). It is also a requirement that any possible known disease that produces demyelinating lesions is ruled out before applying McDonald's criteria.
Multiple sclerosis (MS) can be pathologically defined as the presence of distributed glial scars (scleroses) in the central nervous system that must show dissemination in time (DIT) and in space (DIS) to be considered MS lesions.
MOG antibody disease (MOGAD) or MOG antibody-associated encephalomyelitis (MOG-EM) is an inflammatory demyelinating disease of the central nervous system. Serum anti-myelin oligodendrocyte glycoprotein antibodies are present in up to half of patients with an acquired demyelinating syndrome and have been described in association with a range of phenotypic presentations, including acute disseminated encephalomyelitis, optic neuritis, transverse myelitis, and neuromyelitis optica.
Brenda Banwell is Chief of the Division of Neurology and Co-Director of the Neuroscience Center, and Professor of Neurology at Children's Hospital of Philadelphia and holder of the Grace R. Loeb Endowed Chair in Neurosciences. She also holds the title of Professor of Pediatrics and Neurology at the Perelman School of Medicine at the University of Pennsylvania.