Paediatrics: Acute disseminated encephalomyelitis

Acute disseminated encephalomyelitis

ADEM is an immune mediated disease. It usually occurs following a viral infection, but may follow other infections or vaccination. It involves auto-immune demyelination, it is similar to multiple sclerosis- although mono-phasic. ADEM produces multiple inflammatory lesions in the brain and spinal cord, particularly in the white matter. Usually these are found in the subcortical/central white matter and cortical gray-white junction of both cerebral hemispheres, cerebellum, brainstem, and spinal cord, but other areas including the basal ganglia may also be involved.

Presentation

·  The average age around 5–8yrs old.

·  Abrupt onset and a monophasic course.

·  Symptoms usually begin 1–3wks after infection or vaccination and include fever, headache, drowsiness, coma, and seizures.

·  Average time to maximum severity about four and a half days.

·  Additional symptoms include hemiparesis, paraparesis, and cranial nerve palsies.

Diagnosis

This is based on finding typical changes on MRI- as above in the subcor-tical/central white matter, cortical gray-white junction, cerebellum, brain-stem, and spinal cord. The basal ganglia may also be involved (Fig. 14.3). CSF may show a mild lymphocytosis, with normal glucose, but there may be a mild rise in protein.

Treatment

It is important to exclude other causes of encephalopathy. Then supportive measures such as hydration/feeding, bulbar func-tion and respiration should be instituted. Pulsed intravenous methylpred-nisolone is widely recommended as definitive treatment, and is normally associated with improvement within days.

ADEM may relapse once or twice, it is then called M(ultiple)DEM. Multiple Sclerosis rarely occurs in childhood, but becomes more common as children approach adulthood. It presents with demyelinating plaques, which differ from ADEM in their distribution- more periventricu-lar white matter, and with much less encephalopathy, seizures, and coma, but more focal neurological signs.