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  • Updated 10.29.2025
  • Released 06.28.1996
  • Expires For CME 10.29.2028

Balo concentric sclerosis

Authors
Jikku Zachariah DO, Thomas Scott MD
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Editor
Anthony T Reder MD
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Cite this article

Introduction

Overview

Balo concentric sclerosis is often thought of as a distinct demyelinating syndrome and an atypical variant of multiple sclerosis. The author argues that no absolute evidence differentiates Balo concentric sclerosis from other acute, aggressive forms of multiple sclerosis. However, there are many indications that a district pathology may become clear in the future. This article discusses how the spectrum of Balo concentric sclerosis has evolved with the discovery of nonfatal cases using MRI. Additionally, it describes the spectrum of symptoms and provides an overview of the current concepts behind the formation of its rings. The author speculates that much can be inferred about the mechanism of tissue destruction in multiple sclerosis from pathological observations in Balo concentric sclerosis. This update includes the most recent descriptions of MRI findings, comparing Balo concentric sclerosis to prototypic multiple sclerosis.

Key points

• The hallmark of Balo concentric sclerosis is alternating bands of demyelinated and relatively preserved myelin that create a distinctive target-like “concentric ring” or “onion bulb” pattern on MRI and pathology.

• The concentric ring pattern of Balo concentric sclerosis may be explained by activated microglia and macrophages migrating centrifugally and concentrating in rings. These cells release nitric oxide and oxygen radicals leading to failure of energy production and cell death.

• Balo concentric sclerosis shares features with other forms of acute demyelination, including multiple sclerosis, neuromyelitis optica spectrum disorders, and myelin oligodendrocyte glycoprotein–associated demyelinating disease.

• There is growing consensus that Balo concentric sclerosis represents a distinct hyperacute multiple sclerosis variant with pattern III immunopathology (oligodendrocytopathy).

• The clinical spectrum of Balo concentric sclerosis ranges from monophasic self-limiting disease to relapsing-remitting patterns.

Many cases with a Balo concentric sclerosis pattern noted by magnetic resonance imaging do not progress to multiple sclerosis and have a limited course. Modern case series show a much more favorable prognosis than historically reported.

• IV methylprednisolone is recommended as the first-line treatment for an acute attack. Emerging data on B-cell depleting therapies (rituximab, ocrelizumab) show remarkable clinical and radiological long-term remission.

Historical note and terminology

Balo concentric sclerosis is a CNS disease characterized by pathological and MRI features consisting of alternating concentric rings of demyelinated and relatively myelinated tissue. The evidence that the MRI pattern is tantamount to Balo concentric sclerosis by pathological criteria is based on biopsied cases. The unusual and puzzling pattern has led to a distinctive place in multiple sclerosis nosology following its description by Balό (05). When Balό gave this rare pattern the name “leukoencephalitis periaxialis concentrica,” it became inevitable that future neurologists would link his name to the entity. Nonetheless, the first description of this pathological pattern should be attributed to Marburg who wrote about it 21 years earlier as part of the spectrum of changes found in acute multiple sclerosis (48).

Currently, whether Balo concentric sclerosis is a distinct entity is somewhat controversial. A few reviewers have lumped Balo leukoencephalitis periaxialis, Schilder encephalitis periaxialis diffusa, and Marburg encephalitis periaxialis scleroticans under the single term “concentric sclerosis” (16). The distinction between Balo concentric sclerosis, tumefactive multiple sclerosis, and prototypic multiple sclerosis has been described as overlapping syndromes (24). Because about half of the published cases occur in the setting of typical multiple sclerosis (31), Balo concentric sclerosis has frequently been thought to be a variant of multiple sclerosis. A large case series followed 10 patients with Balo concentric sclerosis from a multiple sclerosis clinic monitoring 2600 patients with multiple sclerosis between 2013 and 2024 (17). All patients had a positive type-2 pattern of oligoclonal bands (unique IgG bands in the CSF that are not present in serum), and the most common symptoms were limb weakness and paresthesia. This study supports the classification of Balo concentric sclerosis as a variant of multiple sclerosis due to overlapping characteristics. Because a significant number of patients with Balo concentric sclerosis lesions have severe and disabling attacks, this view suggests that Balo concentric sclerosis occurs when unfavorable pathological factors are found in a small portion of patients, many of whom progress to multiple sclerosis. Importantly, not all patients with a Balo-like presentation subsequently develop multiple sclerosis.

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