The effects of nuclear DNA mutations on mitochondrial function.

ABSTRACT: The multiple functions of mitochondria, including adenosine triphosphate synthesis, are controlled by the coordination of both the mitochondrial DNA (mtDNA) and the nuclear DNA (nDNA) genomes. Mitochondrial disorders manifest because of impairment of energy metabolism. This article focuses on mutations in two nuclear genes and their effect on mitochondrial function. Mutations in the polymerase gamma, or POLG, gene are associated with multisystemic disease processes, including Alpers Syndrome, a severe childhood-onset syndrome. Mutations in the OPA1 gene are associated with autosomal dominant optic atrophy and other neurologic, musculoskeletal, and ophthalmologic symptoms. When assessing for disorders affecting energy metabolism, sequencing of both the mtDNA genome and the nDNA whole exome sequencing is necessary.

Delineating selective vulnerability of inhibitory interneurons in Alpers' syndrome.

AIMS: Alpers' syndrome is a severe neurodegenerative disease typically caused by bi-allelic variants in the mitochondrial DNA (mtDNA) polymerase gene, POLG, leading to mtDNA depletion. Intractable epilepsy, often with an occipital focus, and extensive neurodegeneration are prominent features of Alpers' syndrome. Mitochondrial oxidative phosphorylation (OXPHOS) is severely impaired with mtDNA depletion and is likely to be a major contributor to the epilepsy and neurodegeneration in Alpers' syndrome. We hypothesised that parvalbumin-positive(+) interneurons, a neuronal class critical for inhibitory regulation of physiological cortical rhythms, would be particularly vulnerable in Alpers' syndrome due to the excessive energy demands necessary to sustain their fast-spiking activity. METHODS: We performed a quantitative neuropathological investigation of inhibitory interneuron subtypes (parvalbumin+, calretinin+, calbindin+, somatostatin interneurons+) in postmortem neocortex from 14 Alpers' syndrome patients, five sudden unexpected death in epilepsy (SUDEP) patients (to control for effects of epilepsy) and nine controls. RESULTS: We identified a severe loss of parvalbumin+ interneurons and clear evidence of OXPHOS impairment in those that remained. Comparison of regional abundance of interneuron subtypes in control tissues demonstrated enrichment of parvalbumin+ interneurons in the occipital cortex, while other subtypes did not exhibit such topographic specificity. CONCLUSIONS: These findings suggest that the vulnerability of parvalbumin+ interneurons to OXPHOS deficits coupled with the high abundance of parvalbumin+ interneurons in the occipital cortex is a key factor in the aetiology of the occipital-predominant epilepsy that characterises Alpers' syndrome. These findings provide novel insights into Alpers' syndrome neuropathology, with important implications for the development of preclinical models and disease-modifying therapeutics.

Clinical and molecular spectrum associated with Polymerase-γ related disorders.

BACKGROUND: POLG pathogenic variants are the commonest single-gene cause of inherited mitochondrial disease. However, the data on clinicogenetic associations in POLG-related disorders are sparse. This study maps the clinicogenetic spectrum of POLG-related disorders in the pediatric population. METHODS: Individuals were recruited across 6 centers in India. Children diagnosed between January 2015 and August 2020 with pathogenic or likely pathogenic POLG variants and age of onset <15 years were eligible. Phenotypically, patients were categorized into Alpers-Huttenlocher syndrome; myocerebrohepatopathy syndrome; myoclonic epilepsy, myopathy, and sensory ataxia; ataxia-neuropathy spectrum; Leigh disease; and autosomal dominant / recessive progressive external ophthalmoplegia. RESULTS: A total of 3729 genetic reports and 4256 hospital records were screened. Twenty-two patients with pathogenic variants were included. Phenotypically, patients were classifiable into Alpers-Huttenlocher syndrome (8/22; 36.4%), progressive external ophthalmoplegia (8/22; 36.4%), Leigh disease (2/22; 9.1%), ataxia-neuropathy spectrum (2/22; 9.1%), and unclassified (2/22; 9.1%). The prominent clinical manifestations included developmental delay (n = 14; 63.7%), neuroregression (n = 14; 63.7%), encephalopathy (n = 11; 50%), epilepsy (n = 11; 50%), ophthalmoplegia (n = 8; 36.4%), and liver dysfunction (n = 8; 36.4%). Forty-four pathogenic variants were identified at 13 loci, and these were clustered at exonuclease (18/44; 40.9%), linker (13/44; 29.5%), polymerase (10/44; 22.7%), and N-terminal domains (3/44; 6.8%). Genotype-phenotype analysis suggested that serious outcomes including neuroregression (odds ratio [OR] 11, 95% CI 2.5, 41), epilepsy (OR 9, 95% CI 2.4, 39), encephalopathy (OR 5.7, 95% CI 1.4, 19), and hepatic dysfunction (OR 4.6, 95% CI 21.3, 15) were associated with at least 1 variant involving linker or polymerase domain. CONCLUSIONS: We describe the clinical subgroups and their associations with different POLG domains. These can aid in the development of follow-up and management strategies of presymptomatic individuals.

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.

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.

Clinical and Radiologic Features, Pathology, and Treatment of Baló Concentric Sclerosis.

OBJECTIVE: To describe clinical, radiologic, and pathologic features of Baló concentric sclerosis (BCS) and assess overlap between BCS and other CNS inflammatory demyelinating diseases. METHODS: Retrospective review of BCS cases from US and Australian tertiary care centers. RESULTS: We identified 40 BCS cases with 38 available MRIs. Solitary MRI lesions were present in 26% (10/38). We saw >1 active concurrent BCS lesion in 45% (17/38). A third (13/38) had multiple sclerosis-suggestive lesions on the index MRI, of which 10 fulfilled Barkhof criteria. In patients with serial MRI performed within 1 month of the index MRI, lesions expanded radially with sequentially increased numbers of T2 hyperintense rings 52% (14/27). Initially nonenhancing or centrally enhancing lesions subsequently developed single or multiple enhancing rings (41%; 9/22) and incomplete enhancing rings (14%; 3/22). Discordance between rings as they appear on apparent diffusion coefficient, diffusion-weighted imaging, and gadolinium-enhanced imaging was observed in 67% (22/33). Aquaporin-4 immunoglobulin G (n = 26) and myelin oligodendrocyte glycoprotein immunoglobulin G (n = 21) were negative in all patients with serum available. Clinical response to steroid treatment was seen in 46% (13/28). A monophasic clinical course was present in 56% (18/32) at last follow-up (median 27.5 months; range 3-100 months). The initial attack was fatal in 10% (4/40). Median time from symptom onset to death was 23 days (range 19-49 days). All 17 patients with pathology available demonstrated typical findings of multiple sclerosis. Patients with active demyelinating lesions all demonstrated oligodendrocytopathy (pattern III). CONCLUSIONS: BCS may be a distinct subtype of multiple sclerosis characterized by pattern III immunopathology.

Valproic acid for myoclonic epilepsy in POLG1 carriers can be fatal.

With interest we read the article by Tarka et al. about the autopsy findings of an 8-year-old female with mitochondrial disorder (MID) due to the compound heterozygous variants c.2243G>C and c.2542G>A in POLG1 [1]. The patient manifested clinically with mental retardation, developmental regression, and myoclonic epilepsy, for which she received valproic acid (VPA) [1]. Neuropathological studies after death from acute pancreatitis and liver failure revealed bilaterally symmetric degenerative lesions of the accessory olivary nuclei in addition to typical features of Alpers-Huttenlocher disease (AHD) [1]. It was concluded that pancreatitis prior to liver failure is unusual [1]. The study is appealing but raises comments and concerns.

MRI signs of CNS demyelinating diseases.

The differential diagnosis of the central nervous system (CNS) demyelinating diseases can be greatly facilitated by visualization and appreciation of pathognomonic radiological signs, visualized on magnetic resonance imaging (MRI) sequences. Given the distinct therapeutic approaches for each of these diseases, a decisive and reliable diagnosis in patients presenting with demyelination-associated symptoms is of crucial value. Multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) are major examples of such conditions, each possessing a number of MRI signs, closely associated with the disorder. This pictorial review aims to describe seventeen pathognomonic MRI signs associated with several CNS demyelinating disorders including MS, NMOSD, myelin oligodendrocyte glycoprotein-associated disease, Baló's concentric sclerosis, metachromatic leukodystrophy, progressive multifocal leukoencephalopathy, and neurosarcoidosis.

Heterogeneity of Baló's concentric sclerosis: a study of eight cases with different therapeutic concepts.

BACKGROUND: Baló's Concentric Sclerosis (BCS) is a rare heterogeneous demyelinating disease with a variety of phenotypes on Magnetic Resonance Imaging (MRI). Existing literature lacks data especially on the therapeutic approach of the disease which we intended to elucidate by means of suggesting a new possible BCS classification and introducing different therapeutic concepts based on each BCS-subgroup characteristics. METHODS: We present a retrospective study of eight treated patients with BCS-type lesions, emphasizing on MRI characteristics and differences on therapeutic maneuvers. RESULTS: Data analysis showed: at disease onset the BCS-type lesion was tumefactive (size ≥2 cm) in 6 patients, with a mean size of 2.7 cm (± 0.80 SD); a coexistence of MS-like plaques on brain MRI was identified in 7 patients of our cohort. The mean age was 26.3 years (±7.3 SD) at disease onset and the mean follow-up period was 56.8 months (range 9-132 months). According to radiological characteristics and response to therapies, we further categorized them into 3 subgroups: a) Group-1; BCS with or without coexisting nonspecific white matter lesions; poor response to intravenous methylprednisolone (IVMP); treated with high doses of immunosuppressive agents (4 patients), b) Group-2; BCS with typical MS lesions; good response to IVMP; treated with MS-disease modifying therapies (2 patients), c) Group-3; BCS with typical MS lesions; poor response to IVMP; treated with rituximab (2 patients). CONCLUSIONS: Our study introduces a new insight regarding the categorization of BCS into three subgroups depending on radiological features at onset and during the course of the disease, in combination with the response to different immunotherapies. Immunosuppressive agents such as cyclophosphamide are usually effective in BCS. However, therapeutic alternatives like anti-CD20 monoclonal antibodies or more classical disease-modifying MS therapies can be considered when BCS has also mixed lesions similar to MS. Future studies with a larger sample size are necessary to further establish these findings, thus leading to better treatment algorithms and improved clinical outcomes.

Global boundedness and stability for a chemotaxis model of Boló's concentric sclerosis.

Baló's concentric sclerosis (BCS) is considered a variant of inflammatory demyelinating disease closely related to multiple sclerosis characterized by a discrete concentrically layered lesion in the cerebal white matter. Khonsari and Calvez (Plos ONE. 2(2007)) proposed a parabolic-elliptic-ODE chemotaxis model for BCS which describes the evolution of the densities of activated macrophages, cytokine and apoptotic oligodendrocytes. Because "classically activated" M1 microglia can produce cytotoxicity, we introduce a linear production term from the activated microglia in the ODE for pro-inflammatory cytotoxic. For the new BCS chemotaxis model, we first investigate the uniform boundedness and global existence of classical solutions, and then get a range of the chemosensitive rate χ where the unique positive equilibrium point is exponentially asymptotically stable.

Distinct microglial and macrophage distribution patterns in the concentric and lamellar lesions in Baló's disease and neuromyelitis optica spectrum disorders.

TMEM119 and purinergic receptor P2Y12 (P2RY12), which are not expressed by recruited peripheral blood macrophages, are proposed to discriminate microglia from macrophages. Therefore, we investigated the distribution patterns of microglia and macrophages in 10 concentric lesions from four autopsied Baló's disease cases and one neuromyelitis optica spectrum disorder (NMOSD) case, using quantitative immunohistochemistry for the markers TMEM119, P2RY12, CD68, CD163 and GLUT5. Three cases with Baló's disease had distal oligodendrogliopathy (DO) showing preferential loss of myelin-associated glycoprotein and early active demyelination in the outermost demyelinating layer (termed DMY-MO). In DMY-MO with DO, TMEM119-positive activated microglia expressing upregulated GLUT5 but markedly downregulated P2RY12 were significantly increased. These activated microglia expressed inducible nitric oxide synthase. Oligodendrocytes and their precursors showed apoptotic-like nuclear condensation in DMY-MO. TMEM119-negative and CD68/CD163-positive macrophages were distributed throughout the lesion center of DMY-MO with DO and these cells demonstrated foamy morphology only in the inner portion but not in the outer portion. In concentric demyelinating lesions from another Baló's case and lamellar demyelinating lesions in an NMOSD case, which had late active demyelination without DO, the densities of TMEM119-, GLUT5- and P2RY12-positive microglia with ramified morphology were significantly increased in myelinated layers but not in demyelinating layers. In particular, in the NMOSD case, TMEM119-positive microglia were confined to the outer portion of the myelinated layers. CD68-positive macrophages with foamy morphology also expressing CD163 accumulated in myelinated as well as in demyelinated layers. These findings suggest that activated microglia expressing TMEM119 and GLUT5, but not P2RY12, are associated with apoptosis of oligodendrocytes in the leading edge of Baló's concentric lesions with DO, whereas TMEM119-, GLUT5- and P2RY12-positive microglia with ramified morphology are associated with myelin preservation in concentric lesions without DO in Baló's disease and NMOSD. These two types of microglia appear to play distinct roles in the formation of concentric lesions.

TSPO PET With 18F-GE-180 to Differentiate Variants of Multiple Sclerosis: Relapsing-Remitting Multiple Sclerosis, Tumefactive Demyelination, and Baló's Concentric Sclerosis.

PET targeting the translocator protein (TSPO) expression is an interesting approach to detect neuroinflammation, as TSPO is upregulated in activated macrophages and microglia. Considering the variable pathophysiology of multiple sclerosis (MS) variants, we compare TSPO PET using F-GE-180 in 3 different demyelinating diseases of the central nervous system: relapsing-remitting MS, tumefactive MS, and Baló's concentric sclerosis. Visualization of neuroinflammation and its PET patterns in addition to MRI may contribute to accurate distinction and monitoring of central nervous system demyelination.

Acute Disseminated Encephalomyelitis with Baló-like Lesion by Scorpion Sting: Case Report.

Acute disseminated encephalomyelitis (ADEM) has been linked to immunizations, viral infections, and occasionally to arthropods stings. Its association with scorpion stings has not been described. A 29-year-old man, who after being stung by a scorpion presented right hemiparesis and language impairment. Brain MRI showed subcortical bihemispheric lesion characteristics of ADEM and a bigger one compatible with Baló concentric sclerosis (BCS). Patient was managed with steroids, showing complete clinical improvement. Magnetic resonance imaging (MRI) after 6 months showed cavitation of the bigger lesion with no new findings. In 2 years of follow-up, there is no clinical relapse or new lesions in MRI. Although cases of ADEM have been reported due to venom of chilopoda and hymenoptera, the scorpion sting can be considered as another new cause; this case being even more relevant due to present a Baló-like lesion in MRI.

Balo's concentric sclerosis: An atypical demyelinating disease in pediatrics.

BACKGROUND: Baló's concentric sclerosis (BCS) is a rare subtype of tumefactive demyelinating disease with characteristic radiological and pathological features. In the medical literature, less than 10 BCS cases have been reported in the pediatric population. CASE: We report the case of a 5-year-old boy who presented to the emergency department with 2 days of left-sided weakness. Magnetic resonance imaging (MRI) revealed 3 tumefactive lesions; further diagnostic studies included MRI spectroscopy, lumbar puncture and biopsy. A final diagnosis of Baló concentric sclerosis was made. He received intravenous methylprednisolone at 30 mg/kg for 5 days, plasma exchange treatment and immunoglobulin G course (2 g/kg/day). The patient was discharged in good condition and asymptomatic; after 8 months of follow-up, he has not presented with new symptoms. CONCLUSION: Baló's concentric sclerosis (BCS) is a rare variant of tumefactive demyelinating disease with only a handful of cases reported in the pediatric population. It poses a diagnostic challenge and therapeutic enigma, since it is difficult to distinguish from a central nervous system (CNS) neoplasm, infection or other CNS lesions on magnetic resonance imaging (MRI). Our case along with those reported in the literature, highlights the importance of considering BCS as a potential differential diagnosis when assessing tumefactive lesions. Distinguishing tumefactive demyelinating lesions from malignancy or infection is critical for proper patient management and to avoid unnecessary medical or surgical interventions.

Antibody signatures in patients with histopathologically defined multiple sclerosis patterns.

Early active multiple sclerosis (MS) lesions can be classified histologically into three main immunopathological patterns of demyelination (patterns I-III), which suggest pathogenic heterogeneity and may predict therapy response. Patterns I and II show signs of immune-mediated demyelination, but only pattern II is associated with antibody/complement deposition. In pattern III lesions, which include Baló's concentric sclerosis, primary oligodendrocyte damage was proposed. Serum antibody reactivities could reflect disease pathogenesis and thus distinguish histopathologically defined MS patterns. We established a customized microarray with more than 700 peptides that represent human and viral antigens potentially relevant for inflammatory demyelinating CNS diseases, and tested sera from 66 patients (pattern I n = 12; II n = 29; III n = 25, including 8 with Baló's), healthy controls, patients with Sjögren's syndrome and stroke patients. Cell-based assays were performed for aquaporin 1 (AQP1) and AQP4 antibody detection. No single peptide showed differential binding among study cohorts. Because antibodies can react with different peptides from one protein, we also analyzed groups of peptides. Patients with pattern II showed significantly higher reactivities to Nogo-A peptides as compared to patterns I (p = 0.02) and III (p = 0.02). Pattern III patients showed higher reactivities to AQP1 (compared to pattern I p = 0.002, pattern II p = 0.001) and varicella zoster virus (VZV, compared to pattern II p = 0.05). In patients with Baló's, AQP1 reactivity was also significantly higher compared to patients without Baló's (p = 0.04), and the former revealed distinct antibody signatures. Histologically, Baló's patients showed loss of AQP1 and AQP4 in demyelinating lesions, but no antibodies binding conformational AQP1 or AQP4 were detected. In summary, higher reactivities to Nogo-A peptides in pattern II patients could be relevant for enhanced axonal repair and remyelination. Higher reactivities to AQP1 peptides in pattern III patients and its subgroup of Baló's patients possibly reflect astrocytic damage. Finally, latent VZV infection may cause peripheral immune activation.

Tumefactive inflammatory leukoencephalopathy in cocaine users: Report of three cases.

BACKGROUND: Cocaine is the most common illicit stimulant drug used in Europe, and it can potentially affect the central nervous system due to a direct effect, or by means of additive drugs. Levamisole has been increasingly used as an additive drug since it extends the stimulating effects of cocaine. This has led to an increase in the detection of levamisole adverse reactions, including levamisole-induced multifocal inflammatory leukoencephalopathy (MIL), a potentially lethal monophasic cerebral demyelinating disease. METHODS: We present three adult patients who developed a MIL with tumefactive demyelinating lesions, leading to encephalopathy and motor manifestations. All these patients had in common a history of chronic or acute use of cocaine. Imaging findings revealed a tumefactive MIL, following a Balo's Concentric Sclerosis (BCS) pattern in two cases. RESULTS: The pathophysiology of levamisole-induced MIL may depend on an immunological mechanism, producing multiple demyelinating lesions affecting the subcortical and periventricular white matter, basal ganglia and/or brainstem. Atypical demyelinating lesions are an unusual finding in levamisole-induced MIL. Specifically, the BCS pattern is a rare finding in these patients: to our knowledge, only two more cases mimicking BCS have been reported in the literature, which have also occurred in chronic cocaine users. CONCLUSIONS: Based on the history and images of our patients and other two similar case reports, we suggest a probable pathophysiological relationship between levamisole-adulterated cocaine use and the occurrence of MIL with atypical demyelinating lesions, even when they present following a BCS imaging pattern.