Balo concentric sclerosis

Balo concentric sclerosis (BCS) is a rare and severe monophasic demyelinating disease, considered a subtype of multiple sclerosis, appearing as a rounded lesion with alternating layers of hyper and hypoattenuation giving it a characteristic 'bullseye' or 'onion bulb' appearance 1,9.

Although BCS is a rare disorder it is most common among people of Han Chinese and Filipino descent, although multiple sclerosis in these populations is less common than in caucasians 10.

Presentation can be similar to other forms of multiple sclerosis, although it is usually monophasic, but most closely resembles acute Marburg type multiple sclerosis, with rapid progression and sometimes fulminant course 4,8,9.

Concentric layers of alternating demyelination and preserved myelin are seen, resulting in the characteristic imaging appearance, although the exact mechanism remains unclear 8.

The characteristic feature is the development of alternating bands of demyelinated and myelinated white matter, which is seen as concentric rings or irregular stripes of high or low signal depending on the sequence 9.

  • T1
    • irregular concentric areas of iso and low signal
  • T2
    • irregular concentric areas alternating iso/hypointense and hyperintense signal 4,9
  • T1 C+ (Gd)
    • typically peripheral ring of enhancement in the area of active demyelination 9
  • DWI
    • some restricted diffusion in the outer ring 7

As with other forms of multiple sclerosis, corticosteroid have been used. The condition tends to have a rapidly progressive course but not necessarily fatal 1,4,6,8.

It was first described by J Balo in 1928 2.

Imaging differential considerations include:

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Article information

rID: 9575
Section: Pathology
Synonyms or Alternate Spellings:
  • Balo concentric sclerosis (BCS)
  • Balo's concentric sclerosis
  • BCS
  • Balo concentric sclerosis
  • Concentric sclerosis of Balo
  • Balo's concentric sclerosis (BCS)
  • Balo disease
  • Balo's disease
  • Leukoencephalitis periaxialis concentrica

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Cases and figures

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    Case 1: possible Balo concentric sclerosis
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    Case 2: possible Balo concentric sclerosis
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