Acute Disseminated Encephalomyelitis

What is ADEM?

Acute Disseminated Encephalomyelitis (ADEM) is a rare inflammatory disorder that affects the central nervous system (CNS), leading to widespread inflammation and damage to the myelin sheath surrounding nerve fibers in the brain and spinal cord. ADEM is often triggered by a preceding viral or bacterial infection, and in some cases, it can follow vaccinations. While it shares similarities with multiple sclerosis (MS), ADEM usually occurs as a single episode and does not typically lead to ongoing neurological deterioration.

Who is affected?

ADEM can occur in individuals of any age but is more common in children. It is estimated that about 80% of cases occur in children under the age of 10, and it is slightly more prevalent in boys than in girls. Though rare, ADEM can also affect adults. The condition is more frequently associated with viral infections, particularly measles, as well as vaccinations such as those for rabies, pertussis, and influenza.

Symptoms of ADEM

Symptoms of ADEM typically develop rapidly and may include:

   • Fever
   • Headache
   • Nausea and vomiting
   • Stiff neck
   • Fatigue and irritability
   • Difficulty walking or loss of coordination (ataxia)
   • Weakness or paralysis on one side of the body (hemiparesis)
   • Visual disturbances, including vision loss due to optic neuritis
   • Altered mental state, confusion, or delirium
   • Seizures in some cases

The severity of symptoms varies, and in extreme cases, ADEM can lead to coma. The duration of symptoms also varies, with most cases resolving within a few weeks to a few months. Rarely, a more severe form called Acute Hemorrhagic Leukoencephalopathy (AHLE) can develop, which is associated with brain hemorrhages.

Diagnosis of ADEM

Diagnosis of ADEM is based on clinical presentation, medical history, and diagnostic tests, which may include:

  • Magnetic Resonance Imaging (MRI): Identifies characteristic white matter lesions in the brain and spinal cord, which help differentiate ADEM from MS and other neurological disorders.
  • Lumbar Puncture (Spinal Tap): Analyzes cerebrospinal fluid (CSF) for signs of inflammation and helps rule out infections such as bacterial meningitis.
  • Electroencephalogram (EEG): Detects abnormal brain activity, particularly in cases where seizures are present.
  • Blood Tests: Help rule out other causes of neurological symptoms and check for signs of infection or immune responses.


Prognosis and Long-Term Effects

Most individuals with ADEM recover well, especially with early treatment. Symptoms typically improve within weeks, although some cases may take months for complete resolution. About one-third of patients may experience lingering neurological symptoms, such as mild cognitive or motor difficulties, for up to a year. Unlike MS, ADEM is usually a one-time event, though in rare cases, individuals may experience a second episode.

Causes and Triggers

The exact cause of ADEM is not fully understood, but it is believed to be an autoimmune response triggered by infections or, less commonly, vaccinations. The immune system mistakenly attacks the myelin sheath, causing inflammation and damage. ADEM most often occurs 1-3 weeks after a viral or bacterial infection, and in very rare cases, it can follow vaccinations, particularly the measles-mumps-rubella (MMR) vaccine.

Treatment

The primary treatment for ADEM involves reducing inflammation and suppressing the immune response. Common treatments include:

   • High-Dose Corticosteroids (e.g., Methylprednisolone): Given intravenously to rapidly reduce inflammation and improve symptoms.
   • Intravenous Immunoglobulin (IVIG) or Plasma Exchange (PLEX): Used in severe cases or when corticosteroids are ineffective.
   • Anticonvulsants: Prescribed if seizures occur.
   • Supportive Care: Includes physical therapy, occupational therapy, and rehabilitation to help recover motor function and coordination.

Early diagnosis and treatment are crucial to improve outcomes and prevent long-term complications. While most people recover fully, some may have residual neurological deficits.