Acute Disseminated Encephalomyelitis

Acute Disseminated Encephalomyelitis (ADE)

Overview

Demyelinating disorder of the CNS that seems to be immune mediated.
Pathogenesis is not known.
Virus usually is not isolated from the nervous system, an allergic or autoimmune reaction is most likely.
Usually preceded by a viral syndrome or vaccinations.
Usually monophasic, but recurrent episodes may occur.
Diseases that may trigger the demyelination:
- measles, rubella, Varicella-zoster, smallpox, mumps, influenza, parainfluenza, infectious mononucleosis, typhoid, mycoplasma infections, upper respiratory and other febrile disease
- vaccination against measles, mumps, rubella, influenza, and rabies.
Most common overall cause: Nonspecific upper respiratory infections and Varicella infections.

Pathology

No change occurs in the external appearance of the brain or spinal cord.
Loss of myelin, with relative sparing of the axon.
Microscopic: perivenular lymphocytic and mononuclear cell infiltration and demyelination.

Symptoms and Signs

Meningeal signs are common early.
Subsequent symptoms and signs: related to the portion of the nervous system that is most severely damaged.
Any part of CNS may be affected.

Clinical testing

CSF pressure may be slightly elevated.
- WBC: mild to moderate increase: 15 to 250 cells/mm3 with lymphocytes predominating.
- Protein: normal or slightly elevated (35 to 150 mg/dl).
- Glucose: normal
- Oligoclonal bands are usually negative
- Myelin basic protein level is usually increased.
EEG: abnormal in most cases, with slow frequency of 4 to 6 Hz and high voltage. The abnormalities persist for several weeks after apparent clinical recovery.
CT head: After several days, the CT scan may show diffuse or scattered low-density lesions in the white matter, some of which may enhance with contrast.
MRI: increased signal intensity on T2 -weighted images.

Treatment

Several reports suggest that adrenocorticotropic hormone or corticosteroids reduces the severity of the neurologic defects.
Isolated case reports: plasmapharesis or IVIG used.

Prognosis

In patients who survive, the neurologic signs usually improve considerably, with about 90% having complete recovery.
The exception is measles, in which sequelae may occur in 20 to 50% of patients.

Further Readings

Acute disseminated encephalitis - Baylor
Kanter. DS. Plasmapheresis in fulminant acute disseminated encephalitis. Neurology. 1995;45:824-827
Kepes JJ. Large focal tumor-like demyelinating lesions of the brain: intermediate entity between multiple sclerosis and acute disseminated encephalomyelitis? A study of 31 patients. Ann Neurol 1993;33:18-27.
Kanter DS, Horensky D, Sperling RA, Kaplan JD, Malachowski ME, Churchill WH. Plasmapheresis in fulminant acute disseminated encephalomyelitis. Neurology 1995;45:824-827.