Abnormal cortical metabolism in acute disseminated encephalomyelitis

Post-infectious encephalomyelitis

The term post-infectious encephalomyelitis (PIEM) is frequently used interchangeably with acute disseminated encephalomyelitis (ADEM), although technically PIEM occurs after a known infection whereas with ADEM there is no antecedent infection. PIEM represents one of the primary demyelinating disorders of the central nervous system, along with multiple sclerosis and Devic's disease. There is no specific diagnostic test for any of these conditions and at onset it may be difficult to differentiate between ADEM and the first attack of multiple sclerosis. However, there are clinical and magnetic resonance imaging features that allow differentiation between PIEM/ADEM and a relapsing disease such as multiple sclerosis. Some patients improve spontaneously; most improve with methylprednisolone. If that fails, plasma exchange or intravenous immunoglobulin may be effective.

Acute disseminated encephalomyelitis: a review of 18 cases in childhood

OBJECTIVE

Acute disseminated encephalomyelitis (ADEM) is a treatable inflammatory demyelinating disorder seen more commonly in children than in adults. It typically presents to general paediatricians, often, like encephalitis, with non-specific cerebrospinal fluid findings. The brain computerized tomography scan is usually normal, so is falsely reassuring and delays the diagnosis, which might result in considerable morbidity. The present study was initiated to report on the various modes of presentation and raise the awareness of the diagnosis of ADEM among general paediatricians.

METHODS

A retrospective review of the case notes of 18 children with a diagnosis of ADEM established in a tertiary referral centre from 1995 to 2000 was undertaken with particular reference to clinical features, investigations and treatment.

RESULTS

The most common presenting features were ataxia (10 cases), followed by headache (eight cases) and weakness (five cases). Magnetic resonance imaging (MRI) of the brain was needed to confirm the diagnosis in all 18 children. Treatment usually included a course of intravenous methylprednisolone followed by a tapering dose of oral prednisolone over several weeks. Although the outcome for most of the children was generally good, two relapsed after cessation of steroids and five children had ongoing disabilities.

CONCLUSIONS

The investigation of choice for establishing the diagnosis of ADEM was MRI of the brain. Other investigations were seldom helpful in reaching the diagnosis. Early diagnosis and prompt treatment of ADEM will probably reduce morbidity.

Postinfectious encephalomyelitis

Postinfectious forms of encephalomyelitis, also termed acute disseminated encephalomyelitis (ADEM), form one of several categories of inflammatory demyelinating disorders of the central nervous system (CNS). Recent large, retrospective case series have refined our understanding of the clinical, laboratory, and neuroimaging characteristics of ADEM. The differences between childhood and adult ADEM, risks of development of multiple sclerosis, and the contributions of recent studies to refining the nosology of CNS demyelinating syndromes are discussed.

Postinfectious encephalomyelitis: etiologic and diagnostic trends

Fifty cases of postinfectious encephalomyelitis admitted to our Pediatric Department during the period 1980 to 1997 were consecutively collected and reviewed. There were 28 males and 22 females. The age of onset ranged from 9 months to 14 years. The antecedent infections included measles (6 cases), rubella (5 cases), mumps (4 cases), chicken pox (4 cases), Epstein-Barr virus infection (11 cases), mycoplasma infection (6 cases), and unknown etiology (14 cases). The cessation of measles, rubella, and mumps as causes for encephalomyelitis in our patients corresponds with the introduction of a measles-mumps-rubella nationwide vaccination program in Taiwan commencing in 1992. The main clinical symptoms were fever, headache, and/or vomiting, seizure, and motor weakness. The presenting signs included altered consciousness, meningeal signs, cranial nerve palsy, brainstem signs, involuntary movement, and cerebellar signs. Computed tomography scans were abnormal for 14 (56%) of 25 patients studied, whereas magnetic resonance imaging (MRI) disclosed lesions in 14 (82%) of 17 patients, with abnormal signals in various parts of the cerebral hemisphere, as well as in the basal ganglion, diencephalon, midbrain, brain stem, and cerebellum. Of the three patients with negative MRI findings, an abnormal finding on somatosensory evoked potential was noted for one patient, and a focal decrease in tracer uptake on single photon emission computed tomography (SPECT) was found for the other two patients. This study demonstrates that the causative agents of postinfectious encephalomyelitis in Taiwan have changed from those of traditional exanthematous diseases to nonspecific respiratory infections and suggests that this may also be the case in other parts of the world. MRI remains the imaging method of choice, whereas other neurofunctional studies such as evoked potentials and SPECT are complementary for the diagnosis.

Pathogenesis, diagnosis, and treatment of acute disseminated encephalomyelitis

Acute disseminated encephalomyelitis is considered a monophasic, inflammatory demyelinating disorder of the central nervous system. A temporal relationship usually exists between the onset of neurologic symptoms and an infection or a vaccination. A viral exanthem facilitates the diagnosis. Some heterogeneity exists with regard to etiology and clinical course of this disease. Immunosuppression is considered the treatment of choice.