Balo concentric sclerosis

Baló's concentric sclerosis is a disease in which the white matter of the brain appears damaged in concentric layers, leaving the axis cylinder intact.^[1] It was described by József Mátyás Baló who initially named it "leuko-encephalitis periaxialis concentrica" from the previous definition,^[2] and it is currently considered one of the borderline forms of multiple sclerosis.

Baló's concentric sclerosis is classified as an inflammatory demyelinating disorder of the central nervous system, distinguished from classical multiple sclerosis by the characteristic formation of concentric rings of demyelination alternating with preserved myelin.^[2] Although earlier reports suggested that the prognosis resembled that of Marburg variant multiple sclerosis, more recent case series and reviews have described patients experiencing more favorable outcomes, including asymptomatic periods, spontaneous remission, or prolonged disease stability.^[3][4][5]

Cases of Baló's concentric sclerosis have been observed to follow a range of courses, with the majority showing a single acute phase, while others demonstrate either a relapsing-remitting pattern or progression similar to aggressive forms of multiple sclerosis.^[6] Although historically considered rare, with fewer than 1% of multiple sclerosis cases showing the characteristic ring-shaped demyelination pattern,^[7][8] Baló's concentric sclerosis is now recognized globally, rather than being geographically confined to Asian populations as once believed.^[9]

The concentric ring appearance is not specific to Baló's concentric sclerosis. Concentric lesions have also been reported in patients with neuromyelitis optica, standard multiple sclerosis, progressive multifocal leukoencephalopathy, cerebral autosomal dominant arteriopathy with subcortical infarcts, leukoencephalopathy, concomitant active hepatitis C and human herpes virus 6.^[4]