Acute disseminated encephalomyelitis
GENERAL ASPECTS
Acute disseminated encephalomyelitis (ADME) is a multifocal inflammatory disease that primarily affects myelin. Myelin is the sheath that covers the axons, which are the pathways through which information is transmitted in the central nervous system.
In acute disseminated encephalomyelitis there is simultaneous and acute demyelination and inflammation in different areas, such as the cerebral hemispheres, cerebellum, brainstem and spinal cord. It most frequently affects children, being much less common in adults. There is a higher incidence during the winter and spring months.
What is its cause?
In most cases, it is triggered after an infection. Probably by molecular mimicry mechanisms, that is, by confusion of the immune system between proteins of the infectious agent and myelin proteins, a process of inflammation is initiated in the central nervous system. The viruses most frequently associated with acute disseminated encephalomyelitis are measles, rubella, varicella zoster virus, herpes simplex, Epstein-Barr virus and cytomegalovirus. It can also be related to non-viral agents such as mycoplasma pneumoniae, among others. Other possible triggers, although very infrequent, are vaccinations. It is important to consider at this point the clear benefit of vaccinations in pediatric age versus the residual risk of ADME. In the case of measles vaccination, studies place the risk at 1-2 cases per million vaccinations, considerably lower than the risk of ADME from adult or pediatric measles virus infection. For diphtheria/tetanus/pertussis vaccine, the risk is 0.385 cases per million.
DIAGNOSIS
What are its symptoms?
They are very variable. In many cases it presents with fever, headache and confusional picture or altered level of consciousness. Convulsive epileptic seizures may appear. Focal symptoms may be motor (weakness), gait, speech or visual disturbances. The clinical course usually develops in a rapidly progressive manner, in a matter of hours or days.
How is it diagnosed?
In the presence of a suggestive clinical picture, the neurologist requests a brain MRI and, preferably, also a spinal cord MRI, where multifocal demyelinating lesions are observed. The neuroimaging study is complemented by a complete blood test in which non-specific inflammatory markers such as c-reactive protein or an increase in leukocytes may be elevated. It is advisable to perform a lumbar puncture to analyze the cerebrospinal fluid where, in many cases, there is an increase in cellularity and proteins.
It is important to establish a correct differential diagnosis to rule out other processes such as multiple sclerosis, encephalitis or rheumatologic pathologies. a possible multiple sclerosis. In the case of sequelae, an adequate neurological rehabilitation can help us to improve the damaged functions.
TREATMENT
How is it treated?
Suspicion of acute disseminated encephalomyelitis is a reason for hospital admission and urgent study. Once the diagnosis is established, it is usually treated with high-dose corticosteroids, intravenous immunoglobulins and, in some cases, it may be necessary to consider plasmapheresis. The therapeutic decision should be taken by the neurologist on an individual basis depending on the clinical picture, results of the complementary study and other factors such as possible concomitant pathologies.
FREQUENT QUESTIONS
What is the prognosis?
Although it is a serious pathology, in most cases in pediatric age, if the diagnosis is early and the treatment early, the patient usually recovers completely in a matter of weeks. In some cases sequelae may remain, such as motor deficits or cognitive problems.
Is further follow-up necessary?
Yes, it is important to have an outpatient follow-up in the neurology office, with clinical reviews and MRI controls to rule out new inflammatory outbreaks, which could lead us to suspect a possible multiple sclerosis. In the case of sequelae, an adequate neurological rehabilitation can help us to improve the damaged functions.
Dr. Fernando Pérez Parra
Date of issue: 06/18/2020
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