OVERVIEW

What is Acute Disseminated Encephalomyelitis?

Acute disseminated encephalomyelitis (ADEM) is an acute idiopathic inflammatory demyelinating disease that extensively affects the brain and spinal cord.

It is more common in children and young adults, typically occurring after infections, rashes, or vaccinations, and is referred to as post-infectious, post-exanthem, or post-vaccination encephalomyelitis. Its fulminant form is also known as acute necrotizing hemorrhagic encephalomyelitis.

ADEM involves widespread lesions, and patients may present with fever, headache, limb weakness, incontinence, psychiatric symptoms, impaired consciousness, seizures, and other diverse clinical manifestations. The disease progresses rapidly, and some patients have a poor prognosis.

Is Acute Disseminated Encephalomyelitis Common?

ADEM is clinically uncommon, and its exact incidence is unclear. The disease often occurs secondary to infections, vaccinations, or immunotherapy. Its onset is age-related, with higher incidence in children, though it is rare in infants under 3 years old. Children are more likely to develop acute disseminated encephalitis, but adults can also be affected.

What Are the Types of Acute Disseminated Encephalomyelitis?

ADEM can be classified into monophasic, recurrent, and multiphasic types based on clinical course, with monophasic being the most common:

• Monophasic: Refers to a single acute inflammatory demyelinating event.
• Recurrent: Occurs when a new demyelinating event happens more than 3 months after the initial episode, with symptoms, signs, and imaging findings identical to the previous episode.
• Multiphasic: Refers to new demyelinating events occurring more than 3 months after the initial episode, with new lesions that may cause different symptoms and signs.

SYMPTOMS

What are the manifestations of acute disseminated encephalomyelitis?

• Typical acute disseminated encephalomyelitis is often preceded by a history of infection within the past month, such as cold, fever, rash, vaccination history, or exposure to cold, rain, childbirth, and surgery.
• Acute disseminated encephalomyelitis can cause widespread multifocal damage to the brain and spinal cord, so the clinical manifestations vary depending on the location of the lesions. Based on clinical symptoms and lesion location, it can be classified into encephalitis type, myelitis type, and encephalomyelitis type:
• Encephalitis type: Patients often present with fever, headache, hemiplegia, aphasia, visual field defects (e.g., hemianopia), rapidly progressing visual impairment (e.g., bilateral optic neuritis), cranial nerve palsy, ataxia, extrapyramidal motor disorders, impaired consciousness, and psychiatric abnormalities, often accompanied by seizures. Severe cases may rapidly progress to coma and decerebrate rigidity.
• Myelitis type: Patients may exhibit partial or complete paraplegia or quadriplegia, limb numbness, progressively ascending limb weakness and sensory disturbances, and varying degrees of bladder and rectal dysfunction.
• Encephalomyelitis type: Combines features of both encephalitis and myelitis.
• Acute disseminated encephalomyelitis also includes two variants: acute hemorrhagic encephalomyelitis and acute disseminated encephalomyelitis with peripheral nervous system involvement.

In which populations does acute disseminated encephalomyelitis commonly occur? How does it progress?

Acute disseminated encephalomyelitis mostly affects children and young adults, with an incubation period of 4–30 days (average 7–14 days) after a preceding infection. The onset is usually acute, with symptoms peaking within days. Symptoms may progress gradually, and the condition can be severe, with some cases being life-threatening. The course may last for weeks or months.

What conditions should acute disseminated encephalomyelitis be differentiated from?

Acute disseminated encephalomyelitis needs to be differentiated from other diseases that can cause acute brain and spinal cord lesions.

This includes multiple sclerosis, neuromyelitis optica, viral encephalitis, primary central nervous system intravascular lymphoma, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections, cerebral thrombophlebitis, hypoxic encephalopathy, or acute toxic hepatic encephalopathy (Reye syndrome), among others.

CAUSES

What are the causes of acute disseminated encephalomyelitis?

The etiology and pathogenesis of acute disseminated encephalomyelitis are not yet fully understood. Typical cases often have a history of preceding infections, most commonly measles, rubella, or chickenpox. It is hypothesized that viral infections or vaccinations may mediate immune abnormalities in the body, thereby triggering demyelinating lesions in the central nervous system.

DIAGNOSIS

How is acute disseminated encephalomyelitis diagnosed?

The diagnosis is primarily based on the patient's history of preceding infection or vaccination, followed by acute manifestations of brain and spinal cord impairment (such as headache, psychiatric symptoms, seizures, limb weakness or numbness, urinary/bowel dysfunction, etc.). It is confirmed through lumbar puncture, imaging studies, and by ruling out other diseases.

What tests are required for patients with acute disseminated encephalomyelitis, and why?

• Hematological tests: Complete blood count, erythrocyte sedimentation rate, and immune marker screening help identify infections or immune abnormalities and exclude other systemic immune disorders.
• Lumbar puncture: Cerebrospinal fluid analysis supports diagnosis, excludes other infectious diseases, and detects oligoclonal bands to differentiate from multiple sclerosis.
• Electroencephalogram (EEG): For patients with brain involvement, EEG often shows widespread moderate or severe abnormalities, aiding in assessing disease severity and detecting epileptic waves in cases of seizures.
• Imaging studies (CT or MRI): Crucial for determining lesion location and extent. Contrast-enhanced MRI also helps differentiate from other central nervous system disorders.

TREATMENT

Which department should I visit for acute disseminated encephalomyelitis?

Neurology.

Can acute disseminated encephalomyelitis heal on its own?

No.

Does acute disseminated encephalomyelitis require hospitalization?

Yes.

How is acute disseminated encephalomyelitis treated?

Currently, there is a lack of large-scale, reliable clinical studies on the treatment of acute disseminated encephalomyelitis. The main treatments include two categories:

• Immunotherapy:
  • High-dose intravenous methylprednisolone followed by a tapering regimen is a widely used treatment. Early administration can reduce brain and spinal cord edema, protect the blood-brain barrier, and inhibit inflammatory demyelination. If there is a history of viral infection in the days before onset, antiviral drugs such as ganciclovir may be administered intravenously alongside methylprednisolone.
  • High-dose intravenous immunoglobulin can be used alone or in combination with glucocorticoids.
  • Plasma exchange may be attempted if high-dose steroid therapy is ineffective.
• Symptomatic and supportive treatment: Supportive care during the acute phase of acute disseminated encephalomyelitis is crucial. Physical cooling and hibernation therapy may be used for patients with high fever or coma. Intracranial pressure can be managed with dehydrating agents. It is also important to control infections and seizures, provide nutritional support, maintain fluid and electrolyte balance, and strengthen nursing care for patients with limb paralysis or coma to prevent complications such as bedsores and hypostatic pneumonia.

DIET & LIFESTYLE

What should patients with acute disseminated encephalomyelitis pay attention to in their diet?

Patients with acute disseminated encephalomyelitis should focus on strengthening nutrition, replenishing energy, and supplementing with fluids and vitamins in their diet.

What should patients with acute disseminated encephalomyelitis pay attention to in daily life?

• During the acute phase, patients require hospitalization and should maintain quiet rest, avoiding emotional anxiety, agitation, catching cold, or constipation.
• If limb paralysis occurs, patients should perform active or assisted movements of the affected limbs to prevent muscle atrophy and lower limb thrombosis, promoting recovery.
• For bedridden patients, caregivers should turn them regularly and pat their backs to reduce complications like bedsores and hypostatic pneumonia.
• If limb paralysis persists after the acute phase, rehabilitation training should be intensified while avoiding accidents such as falls.
• For patients with secondary epilepsy, regular and timely use of antiepileptic drugs is essential. Avoid stimulant beverages, flashing lights, and solitary activities like mountain climbing or swimming.

Does acute disseminated encephalomyelitis require follow-up examinations? How?

Yes, follow-up imaging is needed to monitor lesion progression, along with clinical observation of symptom changes.

Can patients with acute disseminated encephalomyelitis fly, engage in strenuous exercise, or travel to high-altitude areas?

It is not recommended before the disease is effectively treated.

PREVENTION

Can acute disseminated encephalomyelitis be prevented?

The pathogenesis of this disease is not yet clear. Avoiding infections and improving physical fitness may help reduce the occurrence of infection-induced acute disseminated encephalomyelitis.

What is the prognosis for patients with acute disseminated encephalomyelitis?

The prognosis of patients with acute disseminated encephalomyelitis depends on the cause. Patients with post-measles acute disseminated encephalomyelitis have a poor prognosis, with a mortality rate of up to 20%, while those caused by rubella or chickenpox have a relatively better prognosis. Approximately 70% of patients with non-specific infection-induced acute disseminated encephalomyelitis can fully recover.

Some patients may retain neurological signs, intellectual impairment, or behavioral abnormalities, and rare cases may experience recurrence.