Balo concentric sclerosis
| Balo concentric sclerosis | |
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| Typical aspects of Baló's concentric sclerosis. (a) Original case of Baló; several anastomoses are located in the lower half of the lesion. (b) Lesion centered by a veinule showing ring fragmentation in a constrained area. (c) Lesion. (d) Progress of the pathologic process from a center located in a constrained area, showing formation of bands. Loyez staining (myelin in black, destroyed areas in white); scale bars: 1 cm. | |
| Classification and external resources | |
| Specialty | neurology |
| ICD-10 | G37.5 |
| ICD-9-CM | 341.1 |
| DiseasesDB | 11849 |
| MeSH | D002549 |
Balo concentric sclerosis is a disease in which the white matter of the brain appears damaged in concentric layers, leaving the axis cylinder intact. It was described by Joszef Balo who initially named it "leuko-encephalitis periaxialis concentrica" from the previous definition, and it is currently considered one of the borderline forms of multiple sclerosis.
Balo concentric sclerosis is a demyelinating disease similar to standard multiple sclerosis, but with the particularity that the demyelinated tissues form concentric layers. Scientists used to believe that the prognosis was similar to Marburg multiple sclerosis, but now they know that patients can survive, or even have spontaneous remission and asymptomatic cases.
It is also common that the clinical course is primary progressive, but a relapsing-remitting course has been reported. It seems that the course gets better with prednisone therapy, although evidence of this is anecdotal and such conclusions are difficult to accept given that there are cases where patients spontaneously recover whether the patient was on steroid therapy or not.
The lesions of the Balo sclerosis belong to the MS lesion pattern III (distal oligodendrogliopathy). Balo concentric sclerosis is now believed to be a variant of pattern III multiple sclerosis.
According with Dr. Lucchinetti investigations, in Balo's concentric sclerosis, the rings may be caused by a physiological hypoxia (similar to that caused by some toxins or viruses) in the lesion, which is in turn countered by expression of stress proteins at the border. This expression and counter-expression forms rings of preserved tissue within the lesion and rings of demyelinated tissue just beyond where the previous attack had induced the protective stress proteins. Hence, subsequent attacks form concentric rings.
Some other researchers maintain that, as in pattern III MS, the mitochondrial respiratory chain complex IV activity is reduced and this could be the culprit of glutamate-mediated axonal injury.
Other two propossed mechanisms are the presence of granulation tissue in old lesions, which is rich in capillaries and could act as an energy reservoir, and the small adherent bands of myelinated tissue. These two mechanisms are proposed based in the assumption of a hypoxic causation principle
Ultimately, this expanding lesion causes the progressive picture typically seen. However, in some patients, the pathology underlying the disease appears to burn out and hence the disease may halt, hence the patients who spontaneously recover. The mechanisms triggering attacks and recovery remain uncertain.
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