ACUTE HAEMORRHAGIC LEUKOENCEPHALITIS
This is a rare demyelinating disease. It is regarded as a very acute form of postinfectious/acute disseminated encephalomyelitis.
Clinical picture: Antecedent viral infection, depression of conscious level and multifocal signs and symptoms. Focal features may suggest a mass lesion or even herpes simplex encephalitis.
The diagnosis is only really possible at biopsy or autopsy, but elevated CSF pressure, lymphocytosis and erythrocytes in CSF and xanthochromic appearance of fluid are all suggestive. Pathology: Perivascular polymorph infiltration. Microscopic and macroscopic haemorrhage. Perivascular dcmyelination and necrotising changes in vessels.
Treatment: Steroids in high dosage should be used though evidence of value in this rare condition is scant.
This is a demyelinative disease occurring in association with systemic illness in which cell-mediated and occasionally humoral immunity is depressed, e.g. AIDS (4% of cases), lymphoma, sarcoidosis, systemic lupus erythematosus. The disorder is due to reactivation of previous papavirus (SV40 or JC virus) infection. Clinical picture: Features of diffuse process — personality change, hcmiparcsis, cortical visual loss, seizures, etc. Duration of illness: 3-6 months. Non-remitting and fatal.
Pathology: Demyelination without inflammatory response, especially in subcortical white matter. Electron microscopy - papovavirus in oligodendroglia.
Diagnosis: CT scanning and MRI reveal widespread multifocal white matter damage. Definitive diagnosis is made from brain biopsy. Virus can be isolated by inoculation on to glial tissue culture. Treatment: Interferon - alpha and cytosine arabinoside may slow progression.
Inborn errors of metabolism may affect the normal development of myelin. These genetic disorders usually present in infancy or childhood but occasionally produce their first manifestations in adult life. 3 specific types are recognised
- Metachromatic leukodystrophy
- Globoid cell leukodystrophy
- Adrenomyeloneuropathy or adrenoleukodystrophy (ADL).
The last condition is sex linked, characterised by adrenal insufficiency and disordered myelin in brain, spinal cord and peripheral nerve. The clinical picture is highly variable and results from a defect in beta oxidation of very long chain fatty acids (VLCFA) which build up in blood and skin fibroblasts. Dietary treatments (Lorenjo's oils) lower these and may slow progression of this fatal disorder. Heterozygote female carriers may become symptomatic with a late onset progressive myelopathy.
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