Causes and mechanisms of development
The disease is autoimmune in nature, in which the immune system begins to attack its own myelin within the structures of the brain and spinal cord.
Clinical symptoms do not appear spontaneously: they usually develop within a few hours or days after exposure to a specific provoking factor. The main triggers include:
- Viral infections: the most common cause. ADEM is classically associated with prior measles, rubella, or chickenpox.
- Vaccination: development of symptoms following vaccine administration.
- Bacterial infections: act as a trigger much less frequently than viruses.
Clinical presentation and diagnostics
External manifestations of acute disseminated encephalomyelitis are virtually identical to the symptoms of an multiple sclerosis relapse. Patients may experience paresis, sensory disturbances, and other neurological deficits.
The primary instrumental method to confirm the diagnosis is MRI. Tomograms reveal focal changes in the central nervous system that visually closely resemble the demyelinating pattern characteristic of multiple sclerosis.
Treatment regimen
Since the pathogenesis of the disease is close to other demyelinating processes, basic ADEM therapy follows the same protocols as the treatment of multiple sclerosis relapses.
- Corticosteroids (first-line drugs). Pulse therapy is used, followed by a transition to oral formulations:
- Methylprednisolone is administered intravenously by drip at a high dosage: from 500 to 1000 mg per day for 3–7 days.
- Then the patient is switched to oral administration of the drug at a dose of 60–80 mg per day for 5–7 days.
- Withdrawal of the drug must be strictly gradual: the dosage is reduced by 5 mg every 2 days until complete cessation.
- Plasmapheresis. This is a reserve method and is used less frequently than hormone therapy.
- Cytostatics. Drugs of this group (e.g., cyclophosphamide) are prescribed only in severe cases when standard corticosteroid therapy has proven ineffective.
Prognosis and differential diagnosis
The main task in establishing a diagnosis is to distinguish ADEM from the onset of multiple sclerosis.
The fundamental difference lies in the nature of the course: acute disseminated encephalomyelitis is a monophasic disease. This means that after a past episode of ADEM, repeated relapses do not occur in most cases.
Prognosis for patients is considered favorable. The overwhelming majority of patients not only survive but also demonstrate good recovery of lost neurological functions after completing the course of treatment.
Symptomatic therapy of concomitant syndromes
Since the clinical picture of ADEM and multiple sclerosis is similar, general approaches to symptom management can be used during periods of pronounced neurological deficit.
Management of spasticity When significant spastic paresis or paralysis develops, antispastic drugs are prescribed (the dose is always titrated individually):
- Baclofen (Lioresal) — starting dose is 10 mg/day.
- Tizanidine (Sirdalud) — starting dose 4–6 mg/day.
Urological disorders For urination disorders, regulation of the drinking regimen and strict emptying of the bladder by the clock are important.
- For urinary retention, urinary catheterization is indicated.
- For urinary incontinence caused by detrusor hyperreflexia, drugs that reduce its activity are used: tolterodine (2–4 mg/day) or oxybutynin (5–10 mg/day).
Briefly: answers to topical questions
What changes are detected on brain MRI in acute disseminated encephalomyelitis?
Brain MRI in ADEM reveals large diffuse lesions with blurred margins, predominantly in the white matter and subcortically. Lesions are usually larger than 1–2 cm; deep gray matter structures, including the thalamus and basal ganglia, may also be involved, especially in children. T1-hypointense lesions are atypical for ADEM. Unlike multiple sclerosis, where lesions are typically smaller and have distinct margins, ADEM lesions are larger and poorly demarcated. MRI changes may appear with a delay of more than a month or be absent throughout the disease, so a normal MRI does not exclude the diagnosis. In approximately 50% of cases, new lesions appear or existing ones enlarge within the first 3 months; after more than 3 months, monophasic ADEM is not associated with the appearance of new lesions.
What cerebrospinal fluid changes are characteristic of acute disseminated encephalomyelitis?
The provided sources do not contain direct data on characteristic cerebrospinal fluid changes specifically in ADEM. It is only indicated that the absence of oligoclonal bands in the CSF is an indication for testing for aquaporin-4 antibodies in differential diagnosis.
What neurological symptoms are included in the clinical picture of acute disseminated encephalomyelitis?
The clinical picture of ADEM includes encephalopathy and polyfocal (multifocal) neurological deficit. Encephalopathy manifests as altered levels of consciousness (stupor, lethargy) or behavioral disturbances that cannot be explained by fever, systemic illness, or a postictal period. Symptoms develop subacutely, over several days, following a prodromal phase lasting 1–3 weeks, and represent nonspecific multifocal manifestations. The clinical picture generally resembles a multiple sclerosis relapse. New focal symptoms—optic neuritis, myelitis—may appear within the first 3 months without a period of complete remission between them.
ADEM is «mono-sclerosis»: clinical presentation and treatment are like multiple sclerosis, but it repeats only once in a lifetime.
Class and exam questions
What is the main difference between ADEM and multiple sclerosis?
In the absence of relapses. ADEM is a single acute episode, after which repeated exacerbations typically do not occur.
Is it permissible to abruptly discontinue corticosteroids after a course of treatment?
Categorically no. After a course of intravenous infusions and oral intake, the dose must be smoothly tapered by 5 mg every 2 days until complete discontinuation.
What is the prognosis for patients with ADEM?
The prognosis is favorable. Most patients survive and recover lost neurological functions well.
What else to study on this topic
- Prevention of relapses of demyelinating diseases (avoiding infections, sun exposure, physical overexertion)
- Contraindications in demyelinating processes: why thermal procedures and balneotherapy are dangerous
- Features of the course of demyelinating diseases during pregnancy and the postpartum period
- Mechanism of action of cytostatics in autoimmune disorders of the CNS
- Differential diagnosis of MRI lesions in various demyelinating pathologies
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Other topics in the section "Chapter 22. Multiple Sclerosis. Acute Disseminated Encephalomyelitis"
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