Diffusion abnormality in Balo's concentric sclerosis: clues for the pathogenesis

Magnetic Resonance Characteristics of Baló Concentric Sclerosis in Children

BACKGROUND

Baló concentric sclerosis is a rare demyelinating disease with characteristic magnetic resonance appearance of multilayered ringlike lesions of demyelination. This disease is extremely rare in children. We present the clinical data, radiological appearance, and development of lesions in eight children.

METHODS

We analyzed the clinical information of eight patients diagnosed between 2012 and 2020. Magnetic resonance brain and spinal cord examinations with contrast medium administration were performed using a 1.5-T scanner.

RESULTS

All patients presented at least one typical Baló lesion on brain imaging. Four patients additionally had typical multiple sclerosis plaques. All primary Baló lesions had a characteristic appearance of concentric hyperintense rings on T2-weighted imaging and were round or ovoid. Cerebrospinal fluid analysis was performed in all patients. Oligoclonal bands were present in seven patients, and four of them had multiple sclerosis plaques on baseline brain magnetic resonance imaging.

CONCLUSION

Baló concentric sclerosis in children is characterized by acute and severe onset with hemiparesis as a predominant symptom. The size, contrast enhancement, and restricted diffusion depend on the phase of the disease.

Baló's concentric sclerosis - A rare entity within the spectrum of demyelinating diseases

Baló's concentric sclerosis (BCS) is a rare, inflammatory demyelinating disease of the central nervous system (CNS). Historically, BCS was thought to be uniformly fatal and diagnosis was based on postmortem findings. With advances in modern neuroimaging, BCS is currently defined by the presence of concentric layered patterns composed of alternating rings of varying intensity. They are best appreciated on gadolinium-enhanced T1-weighted sequences and predominantly occur in the supratentorial cerebral white matter with sparing of cortical U-fibers. The lamellar pattern of the lesions likely reflects bands of demyelination and relative myelin preservation with minimal axonal loss. While BCS falls within the spectrum of atypical demyelinating diseases, there is ongoing debate over whether BCS is a phenotypical variant of multiple sclerosis (MS) or a separate entity. Corticosteroids comprise first-line therapy but there is ongoing controversy regarding appropriate maintenance therapy. First-line MS disease-modifying therapies such as interferon beta-1a are appropriate for patients who fulfill diagnostic criteria for relapsing-remitting MS. Fingolimod should likely be avoided as Baló-like lesions have been reported during its administration or after withdrawal. Monoclonal antibodies such as natalizumab and rituximab are potentially effective at reducing BCS relapses, but alemtuzumab may be relatively ineffective because humoral immunity does not play a central role in BCS pathogenesis.

From Baló's concentric sclerosis to multiple sclerosis: a series of 6 patients

INTRODUCTION

Baló's concentric sclerosis (BCS) is a rare CNS disorder characterized by alternating bands of demyelination on MRI. One of the main issues is its relationship with multiple sclerosis (MS).

OBJECTIVES

To describe 6 BCS patients. To review the risk of developing MS in BCS patients.

METHODS

We retrospectively recorded clinical and radiological findings of 6 BCS patients and performed a review of the literature.

RESULTS

Six patients (5 women) with a mean age of 25 years old were included. Main symptoms were hemiparesis/hemihypoesthesia. On MRI, two patients had a single BCS lesion and four had additional MS-like lesions. Alternating bands were usually more visible on DWI. A patient had reduced central perfusion and SWI hypointensity suggestive of a central vein. Oligoclonal bands were identified in 5/6 patients. After 7 years of follow-up, all patients achieved MS criteria with mild disability (mean EDSS 1.75; 0-4). Our literature review included 65 BCS patients from 30 studies: although CSF oligoclonal bands and the presence of additional MS lesions were associated with subsequent relapses, this was not significant.

DISCUSSION/CONCLUSION

Our series allows a detailed MRI description in BCS and gives a new insight into BCS evolution and its strong relationship with MS.

Balo’s concentric sclerosis in a patient with spontaneous remission based on magnetic resonance imaging: A case report and review of literature

Balo’s concentric sclerosis (BCS) is a rare monophasic demyelinating disease known as multiple sclerosis subtype and seen as a round lesion with variable hyper and hypo-detoxification layers. Characteristic appearance can be seen as “bulb eye” or “onion bulb”. The initial terminology for this neurological disorder was leukoencephalitis periaxialis concentrica; this is defined as a disease in which the white matter of the brain is destroyed in concentric layers in such a way as to leave the axial cylinders intact. This report presents a case of BCS with spontaneous healing of the patient and a mass lesion with concentric rings adjacent to the left lateral ventricle and the posterior portion of the corpus callosum with peripheral vasogenic edema. The neurological lesion of the patient was similar to the magnetic resonance imaging and clinical findings of the BCS.

Balo’s concentric sclerosis: an update and comprehensive literature review

Balo’s concentric sclerosis (BCS) is considered a variant of multiple sclerosis characterized by concentric lamella of alternating demyelinated and partially myelinated tissues. It is a rare and a relatively acute condition. Attacks may proceed rapidly over weeks or months, typically without remission, like Marburg’s variant, resulting in death or severe disability. However, the majority of cases have a more benign, self-limiting course with spontaneous remission. Magnetic resonance imaging is a primary imaging modality in the diagnosis of BCS. Treatment with intense immunosuppression may be indicated in patients with more aggressive form. New reports reveal more evidence regarding the pathophysiology and treatment strategies.

Why Is This Auntminnie a Diagnostic Conundrum?: A Knowledge-Based Approach to Balo's Concentric Sclerosis From Reports of 3 Cases and Pooled Data From 68 Other Patients in the Literature

INTRODUCTION

We came across 3 cases of Balo's concentric sclerosis (BCS). The first of these patients presented to an outside hospital and was transferred to our institution due to complications resulting from a biopsy. The other 2 patients, despite having a characteristic imaging appearance and despite insistence on our part on the diagnosis of BCS, underwent a surgical procedure, which could have been prevented. This led us to review the available literature on BCS.

MATERIAL AND METHODS

A total of 68 patients diagnosed with BCS between 1995 and 2015 were studied and the data collected for the clinical presentation and course, imaging, spinal fluid analysis, treatment, and clinical and imaging outcome.

CONCLUSIONS

A 25% surgery rate (biopsy or resection) was found in the study. We concluded that this relatively high surgery rate in this auntminnie nonsurgical disease is multifactorial; and includes factors like nonfamiliarity with the disease, anxiety on the part of patients and physicians, due to a sometimes rapidly deteriorating clinical picture; and resemblance of the disease with other entities such as tumor and infection. However, characteristic imaging appearance combined with acute or subacute presentation and dramatic improvement in clinical status after high-dose steroid chemotherapy; are highly suggestive of the disease, and can prevent unnecessary surgery.

Eccentric development of Balo's concentric sclerosis: detected by magnetic resonance diffusion-weighted imaging and magnetic resonance spectroscopy

BACKGROUND

The concentricity of BCS has captured wide attention; the findings of the current study may provide useful information on the centrifugal pathogenesis of BCS.

OBJECTIVE

This study aims to evaluate the performance of MRI, DWI and MRS in elucidating the pathogenesis of Balo's lesions expanding.

METHODS

Six clinically diagnosed BCS cases were reviewed, and the findings obtained by MRI, DWI and MRS were analyzed. DWI data were available for six patients, with the DWI and ADC imaging locations being central and peripheral layers of the index lesion. At TE 144ms, we calculated metabolite ratios of MRS at different depths of the demyelinating lesions and compared with the lesion on the opposite normal side for two patients.

RESULTS

The ADC values of 18 typical concentric lesions revealed that the central lesion had the highest ADC value, followed by the internal ring, and the outermost layer had the lowest ADC value. The reduction in NAA/Cr and the increase in Cho/Cr were more evident in the central lesion than in the internal and outermost ring.

CONCLUSION

The findings of DWI and MRS indicate Balo's concentric rings develop gradually and centrifugally. Of course, this hypothesis remains to be proved by further experimental studies.

Baló's concentric sclerosis

Baló's concentric sclerosis is often regarded as a rare variant of multiple sclerosis. Patients with this disorder present with acute or subacute neurological deterioration, with MRI showing one or more concentrically multilayered ring-like lesions usually in the cerebral white matter. Historically, Baló's concentric sclerosis was thought fatal in all cases. However, the availability of MRI has led to a better appreciation of the variable natural history of patients presenting with radiologically evident Baló lesions and the clinical association with multiple sclerosis and, less often, with other neurological disorders. Important advances have increased understanding of the immunopathogenic mechanisms associated with the formation of Baló lesions. However, how to treat an acute lesion and when or whether to start treatment are less well understood, although for patients with Baló lesions who also fulfil standard diagnostic criteria for multiple sclerosis, our opinion is that treatment with multiple sclerosis disease-modifying therapy would seem reasonable.

Atypical idiopathic inflammatory demyelinating lesions (IIDL): conventional and diffusion-weighted MR imaging (DWI) findings in 42 cases

INTRODUCTION

The purpose of this study was to evaluate MR imaging characteristics with conventional and advanced MR imaging techniques in patients with IIDL.

METHODS

MR images of the brain in 42 patients (20 male, 22 female) with suspected or known multiple sclerosis (MS) from four institutions were retrospectively analyzed. Lesions were classified into five different subtypes: (1) ring-like lesions; (2) Balo-like lesions; (3) diffuse infiltrating lesions; (4) megacystic lesions; and (5) unclassified lesions. The location, size, margins, and signal intensities on T1WI, T2WI, and diffusion-weighted images (DWI), and the ADC values/ratios for all lesions, as well as the contrast enhancement pattern, and the presence of edema, were recorded.

RESULTS

There were 30 ring-like, 10 Balo-like, 3 megacystic-like and 16 diffuse infiltrating-like lesions were detected. Three lesions were categorized as unclassified lesions. Of the 30 ring-like lesions, 23 were hypointense centrally with a hyperintense rim. The mean ADC, measured centrally, was 1.50 ± 0.41 × 10(-3) mm(2)/s. The mean ADC in the non-enhancing layers of the Balo-like lesions was 2.29 ± 0.17 × 10(-3) mm(2)/s, and the mean ADC in enhancing layers was 1.03 ± 0.30 × 10(-3) mm(2)/s. Megacystic lesions had a mean ADC of 2.14 ± 0.26 × 10(-3)mm(2)/s. Peripheral strong enhancement with high signal on DWI was present in all diffuse infiltrating lesions. Unclassified lesions showed a mean ADC of 1.43 ± 0.13 mm(2)/s.

CONCLUSION

Restriction of diffusion will be seen in the outer layers of active inflammation/demyelination in Balo-like lesions, in the enhancing part of ring-like lesions, and at the periphery of infiltrative-type lesions.

Diffusion-weighted imaging characteristics of biopsy-proven demyelinating brain lesions

OBJECTIVES

To describe lesional diffusion-weighted imaging characteristics in a cohort of patients with biopsy-proven CNS inflammatory demyelinating disease (IDD) and compare diffusion characteristics of ring-enhancing CNS IDD lesions vs abscesses and tumors.

METHODS

Forty prebiopsy apparent diffusion coefficient (ADC) maps were reviewed from 30 patients with CNS IDD. Lesions were analyzed for size, T2-weighted (T2W) hypointense rim, enhancement, and ADC pattern. ADC patterns of CNS IDD ring-enhancing lesions were compared with a published cohort of 35 patients with ring-enhancing tumors and abscesses.

RESULTS

IDD lesions displayed a spectrum of peripheral ADC patterns at the lesion edge: restricted diffusion (low ADC), 33%; increased diffusion (high ADC), 60%; and normal diffusion (homogeneously isointense), 7%. Of biopsied lesions, 93% enhanced (ring, 52%; heterogeneous, 34%; homogeneous, 7%). A hypointense T2W rim was observed in 53%. A ring pattern on ADC (isointense or dark) was associated with T2W hypointense rims (p = 0.02) but not with ring enhancement. On serial imaging, 4 of 7 (57%) patients demonstrated changes in ADC patterns. Peripheral restriction was more common in IDD (p = 0.006) than in tumors or abscesses, whereas central restriction was only observed in abscesses. Restricted lesions in the same stage were more common in the non-IDD cohort (42% vs 20%), with a uniform restricted pattern seen only in abscesses.

CONCLUSIONS

In ring-enhancing lesions, peripheral diffusion restriction is more common in IDD than in tumors/abscesses, whereas central restriction is more common among abscesses. Rapid ADC pattern changes in IDD probably reflect dynamic lesion evolution and may distinguish IDD from tumors.

[Recent progress in multiple sclerosis research: astrocytopathy in demyelinating diseases]

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) while neuromyelitis optica (NMO) is an inflammatory disease of the CNS that selectively affects the optic nerves and spinal cord. Recently, a specific IgG against NMO, designated NMO-IgG, was discovered, and the relevant antigen was found to be aquaporin 4 (AQP4), one of the major water channel proteins in the CNS. The sensitivity of NMO-IgG/anti-AQP4 antibodies for NMO varies from 30% to 80%, while specificity is 90-100%. Pathological studies on NMO patients have revealed perivascular immune complex (IgM, IgG and C9neo) deposition and extensive loss of AQP4 in active lesions, while myelin basic protein (MBP) staining was relatively preserved. IgG from NMO-IgG-seropositive NMO patients induces astrocyte death in culture in the presence of complement, and reproduces astrocyte loss in vivo when MBP-specific T cells are co-transferred to cause experimental autoimmune encephalomyelitis. Therefore, it is postulated that the complement-activating anti-AQP4 antibodies have a pivotal role in the development of NMO lesions through astrocyte necrosis, and that demyelination is a secondary event. Baló's disease is characterized by alternating rings of demyelination and preserved myelin. As additional MS-like lesions often coexist in Baló's cases, Baló's disease is regarded as a variant of MS. However, Baló's concentric rings are also observed in NMO cases and in Asian opticospinal MS patients in the cerebral white matter, spinal cord and optic chiasm. In demyelinated areas, many hypertrophic astrocytes are present, in close contact with oligodendrocytes that often show apoptotic features. In the outermost layer of preserved myelin, stress proteins involved in tissue preconditioning are abundant in oligodendrocytes. The peri-plaque white matter is thus assumed resistant to subsequent attack, thereby leaving a layer of preserved myelin. In some patients, Baló's concentric rings develop systematically in a centrifugal direction, while other patients show simultaneous enhancement of multiple rings. Therefore, tissue preconditioning and successive ring formation does not fully explain the mechanism of the disease. We recently reported that AQP4 was extensively lost in glial fibrillary acidic protein-positive hypertrophic astrocytes, both in demyelinated and myelinated layers of all actively demyelinating lesions in four Filipino Baló's patients. None of six other patients with magnetic resonance imaging-confirmed Baló's disease was seropositive for anti-AQP4 antibodies. I therefore propose that AQP4 astrocytopathy, in the absence of anti-AQP4 antibodies, is characteristic of Baló's disease. Since a similar loss of AQP4 without perivascular deposition of immunoglobulin and complement is also observed in autopsied CNS tissues from NMO and MS cases, I consider that autoantibody-independent astrocytopathy may widely occur in human CNS demyelinating diseases, including Baló's disease, MS and NMO.

Astrocytopathy in Balo's disease

Baló's disease is characterized by alternating rings of demyelination and preserved myelin. As additional multiple sclerosis (MS)-like lesions often coexist in Baló's cases, Baló's disease is regarded as a variant of MS. In demyelinated areas, many hypertrophic astrocytes are present in close contact with oligodendrocytes, which often show apoptotic features. In the outermost layer of preserved myelin, stress proteins involved in tissue preconditioning are abundant in oligodendrocytes. The peri-plaque perimeter is thus assumed resistant to subsequent attack, thereby leaving a layer of preserved myelin. In some cases, Baló's concentric rings develop step by step in a centrifugal direction, whereas many other cases show simultaneous enhancement of multiple rings. Therefore tissue preconditioning and successive ring formation does not fully describe the mechanism of the disease. We recently reported that in four Filipino Baló's patients, aquaporin-4 (AQP4) was extensively lost in glial fibrillary acidic protein-positive hypertrophic astrocytes, both in demyelinated and myelinated layers of all actively demyelinating lesions. None of six further patients with MRI-confirmed Baló's disease were seropositive for anti-AQP4 antibody. I propose that AQP4 astrocytopathy, in the absence of anti-AQP4 antibody, is characteristic of Baló's disease. This hypothesis should be tested in future experimental studies.

Aquaporin-4 astrocytopathy in Baló's disease

Baló's concentric sclerosis (BCS) is considered to be a rare variant of multiple sclerosis and characterized by alternating rings of demyelinated and preserved myelin layers. The mechanism underlying BCS remains to be elucidated. Recently, occurrence of concentric rings of Baló was described in the brainstem of a patient with neuromyelitis optica (NMO). Because selective loss of aquaporin-4 (AQP4) and vasculocentric deposition of complement and immunoglobulins are characteristic in NMO, we aimed to assess AQP4 expression in the concentric demyelinating lesions of BCS patients. We evaluated AQP4 expression relative to expression of another astrocytic marker (glial fibrillary acidic protein), the extent of demyelination, lesion staging and perivascular deposition of complement and immunoglobulin in four cases with BCS, and 30 individuals with other neurological diseases. All cases with BCS demonstrated extensive AQP4 loss in both demyelinated and myelinated layers of all actively demyelinating lesions, with perivascular lymphocytic cuffing of T cells, but no deposition of immunoglobulins or complement around vessels. These findings suggest that AQP4 loss occurs in heterogeneous demyelinating conditions, namely NMO and BCS. Furthermore, acute BCS lesions are characterized by extensive AQP4 loss without vasculocentric deposition of complement or immunoglobulin.

What insights have new imaging techniques given into aggressive forms of MS--different forms of MS or different from MS?

"Aggressive" multiple sclerosis (MS) is still a challenging diagnosis, in spite of the relevant progresses concerning the comprehension of the disease mechanisms, especially through pathology studies and the advent of conventional magnetic resonance imaging (MRI). Some reviews have been already published on their clinical and therapeutical aspects, but no systematic review is available in literature about the neuroradiological features, using both conventional and advanced techniques. In particular, advanced MRI techniques, namely diffusion-weighted and tensor imaging, magnetization transfer imaging, and proton magnetic resonance spectroscopy, are giving new insights to find specific and appropriate radiological parameters that can help in targeting the diagnosis. We report a review of literature on the neuroradiological findings of aggressive forms of MS, focusing specifically on the role of advanced MRI techniques in the diagnostic phase and during follow-up.

Serial proton MR spectroscopy and diffusion tensor imaging in infantile Balo's concentric sclerosis

Introduction

Proton magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) yield different parameters for characterizing the evolution of a demyelinating white matter disease. The purpose was to elucidate biochemical and microstructural changes in Balo’s concentric sclerosis lesions and to correlate the findings with the clinical course.

Methods

Localized short-echo time MRS and DTI were performed over 6 years in a left occipital lesion of a female patient (age at onset 13.8 years) with Balo’s concentric sclerosis. A right homonym hemianopsia persisted.

Results

Metabolite patterns were in line with initial active demyelination followed by gliosis and partial recovery of neuroaxonal metabolites. Fractional anisotropy and mean diffusivity of tissue water remained severely altered. Fiber tracking confirmed a disruption in the geniculo-calcarine tract as well as involvement of the corpus callosum.

Conclusion

MRS and DTI depict complementary parameters, but DTI seems to correlate better with clinical symptoms.

Technology insight: can neuroimaging provide insights into the role of ischemia in Baló's concentric sclerosis?

Baló's concentric sclerosis (BCS) has long been considered to be a variant of multiple sclerosis. Although BCS was initially described over 100 years ago, relatively few antemortem cases have been identified, and the exact pathogenesis remains unknown. Inflammatory protective ischemic preconditioning has recently been suggested as a mechanism by which the typical concentric rings of the BCS lesion are formed. Advanced neuroimaging can provide important in vivo markers of disease progression that can assist in the diagnosis and management of patients with BCS. In this Review, we discuss evidence from longitudinal neuroimaging studies that supports the role of ischemic preconditioning in BCS.

Idiopathic inflammatory-demyelinating diseases of the central nervous system

Idiopathic inflammatory-demyelinating diseases (IIDDs) include a broad spectrum of central nervous system disorders that can usually be differentiated on the basis of clinical, imaging, laboratory and pathological findings. However, there can be a considerable overlap between at least some of these disorders, leading to misdiagnoses or diagnostic uncertainty. The relapsing-remitting and secondary progressive forms of multiple sclerosis (MS) are the most common IIDDs. Other MS phenotypes include those with a progressive course from onset (primary progressive and progressive relapsing) or with a benign course continuing for years after onset (benign MS). Uncommon forms of IIDDs can be classified clinically into: (1) fulminant or acute IIDDs, such as the Marburg variant of MS, Baló's concentric sclerosis, Schilder's disease, and acute disseminated encephalomyelitis; (2) monosymptomatic IIDDs, such as those involving the spinal cord (transverse myelitis), optic nerve (optic neuritis) or brainstem and cerebellum; and (3) IIDDs with a restricted topographical distribution, including Devic's neuromyelitis optica, recurrent optic neuritis and relapsing transverse myelitis. Other forms of IIDD, which are classified clinically and radiologically as pseudotumoral, can have different forms of presentation and clinical courses. Although some of these uncommon IIDDs are variants of MS, others probably correspond to different entities. MR imaging of the brain and spine is the imaging technique of choice for diagnosing these disorders, and together with the clinical and laboratory findings can accurately classify them. Precise classification of these disorders may have relevant prognostic and treatment implications, and might be helpful in distinguishing them from tumoral or infectious lesions, avoiding unnecessary aggressive diagnostic or therapeutic procedures.

The origins of concentric demyelination: self-organization in the human brain

Baló's concentric sclerosis is a rare atypical form of multiple sclerosis characterized by striking concentric demyelination patterns. We propose a robust mathematical model for Baló's sclerosis, sharing common molecular and cellular mechanisms with multiple sclerosis. A reconsideration of the analogies between Baló's sclerosis and the Liesegang periodic precipitation phenomenon led us to propose a chemotactic cellular model for this disease. Rings of demyelination appear as a result of self-organization processes, and closely mimic Baló lesions. According to our results, homogeneous and concentric demyelinations may be two different macroscopic outcomes of a single fundamental immune disorder. Furthermore, in chemotactic models, cellular aggressivity appears to play a central role in pattern formation.