White Matter Disorders Research Articles

Synthetic MR: Clinical applications in neuroradiology.

Synthetic MR is a quantitative MRI method that measures tissue relaxation times and generates multiple contrast-weighted images using suitable algorithms. The present article principally discusses the multiple dynamic multiple echo (MDME) technique of synthetic MR and briefly describes other quantitative MR sequences. Using illustrative cases, various applications of the MDME sequence in neuroradiology are explained. The MDME sequence allows rapid quantification of tissue relaxation times in a scan duration of 5-7 minutes for full brain coverage. It also has the additional advantages of myelin quantification and automatic segmentation of brain volumes. Applications including reducing scan time, improved detection of demyelinating plaques in Multiple Sclerosis (MS), objective assessment and follow-up for brain atrophy in neurodegenerative MS and dementia cases, and applications in stroke imaging and neuro-oncology are discussed. Uses in the pediatric population, including assessment of brain development and progression of myelination in children, evaluation of white matter disorders, and evaluation of pediatric and adult epilepsy, are elaborated. Quantitative evaluation by synthetic MR is discussed, which allows homogenization and objectification of the radiology data and can serve as a valuable source for artificial intelligence and future multicentre studies. A brief discussion on the technique, other quantitative MR methods, and limitations of the MDME sequence is also presented. The article intends to provide an explicit and comprehensive review of the applications of synthetic MR in neuroradiology, exploring its potential as a routine sequence in daily neuroimaging practice.

Magnetic Resonance Spectroscopy Findings in The Variable Pediatric White Matter Disorders in Suez Canal Area

Magnetic Resonance Spectroscopy Findings in The Variable Pediatric White Matter Disorders in Suez Canal Area

Clinical and MRI Evaluation of Children with Leukodystrophies

Introduction: Leukodystrophies are a diverse group of rare, inherited neurodegenerative disorders affecting the brain’s white matter, leading to progressive neurological impairment. Magnetic Resonance Imaging (MRI) plays a crucial role in diagnosing these conditions, offering detailed insight into white matter abnormalities and aiding in distinguishing various leukodystrophies. Objective: This study aims to evaluate children with leukodystrophies using MRI, establish accurate diagnoses, assess the severity and extent of white matter lesions, and demonstrate the different patterns of abnormal myelination. Methods: This prospective observational study was conducted in the Department of Radiodiagnosis and Imaging at Sher-I-Kashmir Institute of Medical Sciences, Srinagar, from June 2022 to June 2024. All children suspected of having white matter disorders based on clinical features and biochemical tests were included. MRI was performed to identify patterns of white matter involvement, and findings were correlated with clinical data. Results: A total of 29 children (age range: 2 months to 18 years) were evaluated. MRI findings revealed that demyelinating leukodystrophies were the most common, with symmetrical white matter involvement. Hypomyelinating disorders showed diffuse white matter changes with sparing of the U-fibers. Specific patterns, such as tigroid appearance in metachromatic leukodystrophy and posterior fossa involvement in Alexander disease, were identified. MRI was instrumental in narrowing down differential diagnoses and identifying characteristic patterns for various leukodystrophies. Conclusion: MRI is an invaluable tool in the diagnosis and management of leukodystrophies in children. It allows for early identification of disease patterns, which is critical for appropriate clinical management and potential therapeutic interventions. Further research is needed to explore the genetic basis of these disorders in the Kashmiri population.

Spectrum of Leukodystrophy and Genetic Leukoencephalopathy in Indian Population Diagnosed by Clinical Exome Sequencing and Clinical Utility.

Next-generation sequencing (NGS) has expedited the diagnostic process and unearthed many rare disorders in leukodystrophy (LD) and genetic leukoencephalopathy (gLE). Despite the progress in genomics, there is a paucity of data on the distribution of genetic white matter disorders (WMDs) and the diagnostic utility of NGS-based assays in a clinical setting. This study was initiated to explore the clinical, radiologic, and genetic spectrum of LD and gLE in the Indian population and also to estimate the diagnostic yield of clinical exome sequencing (CES). This is a retrospective descriptive analysis of patients with a diagnosis of genetic WMDs from a single tertiary referral center who had CES performed as part of the diagnostic evaluation between January 2016 and December 2021. The demographic, clinical, radiologic, and genetic data were collected. The variants were classified using the American College of Medical Genetics and Genomics criteria. Pathogenic and likely pathogenic variants were included in the calculation of the diagnostic yield. In the study period, 138 patients were clinically diagnosed with either LD or gLE, of which 86 patients underwent CES. Pathogenic variants, likely pathogenic variants, and variants of uncertain significance with phenotype match were seen in 40 (41.8%), 13 (29.1%), and 15 (15.2%) patients, respectively. The mean age at onset in these 68 patients was 6.35 years (range 1 month-39 years), and 38 (55.9%) were male. LDs and gLE were diagnosed in 31 and 37 patients, respectively. 56 patients (71.8%) had autosomal recessive inheritance. The common clinical presentations were developmental delay (23.5%), psychomotor regression (20.6%), progressive myoclonic epilepsy syndrome (19.1%), and spastic ataxia (14.7%). Myelin disorders (48.5%) and leuko-axonopathies (41.2%) were the commonest type of disorders. The most frequently identified genes were ARSA, CLN5, ABCD1, CLN6, TPP1, HEXA, and L2HGDH. The diagnostic yield of the study was 61.6% (53/86), which increased to 79.1% when VUS with phenotype match were included. This study demonstrated a high diagnostic yield from proband-only CES in the evaluation of genetic WMDs and should be considered as a first-line investigation for genetic diagnosis. This study provides Class IV evidence that proband-only clinical exome sequencing is a useful "first-line investigation" for patients with genetic white matter disorders.

Role of clinicoradiological correlation in evaluation of various demyelinating disorders: A Systematic review

Background: There are mainly three types of white matter disorders resulting from defective myelination (dysmyelinating), destruction of myelin (demyelination) and decreased myelination (hypomyelinating). Each of these disorders require MRI and specific imaging for diagnosis. However, diagnosis of white matter disorders cannot solely rely on imaging. Objective: In this review we aim to correlate clinical presentation, history, laboratory investigations, and imaging as a tool rather than diagnostic modality to highlight the importance of clinical and radiological collaboration to diagnose the exact disease process. We would specifically discuss variants of multiple sclerosis, acute disseminated encephalomyelitis, neuromyelitis Optica spectrum disorder, progressive multifocal leuckoencephalothy, and osmotic demyelination syndrome. This study also includes specific signs of different demyelination white matter disorders on MRI which are characteristic of that disease process. However, we also highlight what clinical correlation and investigations may further aid to confirm the diagnosis, prognosis and extent of disease progression. Methods: In this review article we used Prisma guidelines we extracted studies where there was evidence of better patient outcome in terms of clinicoradiological collaboration in diagnosing various demyelinating white matter disorders. Results: We found that timely diagnosis and better patient outcomes can be achieved if clinicians also take in accord their own clinical judgement and based on that order relevant radiological investigations resulting better clinician to clinician communication, judicious use of hospital resources and overall better outcome in disease process. Conclusion: Our study concludes that solid clinical judgement, laboratory investigations along with radiological features of disease process would enhance clinical outcomes in terms of timely diagnosis, specific treatment and tracking disease prognosis.

Anything is better than nothing’: exploring attitudes towards novel therapies in leukodystrophy clinical trials

Background/AimLeukodystrophies comprise a group of genetic white matter disorders that lead to progressive motor and cognitive impairment. Recent development of novel therapies has led to an increase in clinical trials for leukodystrophies. To enable recruitment of individuals with a leukodystrophy into clinical trials, clinical trial acceptability should be ascertained. We sought therefore, to identify the motivations for and barriers to clinical trial participation in addition to clinical trial features that may be of concern to individuals with a leukodystrophy and/or their carers.MethodsAdults with a leukodystrophy and parents/carers of individuals with a leukodystrophy were recruited through the Australian Leukodystrophy Registry and through online advertisements. Qualitative semi-structured interviews were used to explore participants views on what clinical trials involve, the perceived risks and benefits of clinical trials, their desire to participate in clinical trials and their personal experience with leukodystrophy. Thematic analysis of data was performed with co-coding of interview transcripts.Results5 interviews were held with parents of children with leukodystrophy, 4 with parents of adults with leukodystrophy and 3 with adults diagnosed with leukodystrophy. Motivations for clinical trial enrolment include access to potentially lifesaving novel treatments and improved prognostic outcomes. Participants were concerned about adverse clinical trial outcomes, including side effects and exacerbation of illness. Despite this, majority of participants were willing to try anything in clinical trials, demonstrating a high tolerance for first in human trials and trials utilising invasive treatment options.ConclusionsInterviewees communicated a strong desire to participate in interventional clinical trials involving novel therapies. To support enrolment into future leukodystrophy clinical trials we suggest the provision of transparent information regarding clinical trial treatments, consideration of alternative trial control measures, and inclusion of treating clinicians in the trial recruitment process. Clinicians play an integral role in initiating transparent conversations regarding trial risks and adverse outcomes.

An extensive in silico analysis of missense mutations of the human AIMP2 gene

HLD17 (Hypomyelinating Leukodystrophy 17) is an inherited white matter disorder characterized by insufficient myelin production due to biallelic loss of function mutations in the aminoacyl-tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2) gene. In silico analysis of SNVs (single nucleotide variants) in the AIMP2 gene is an efficient and cost-effective method for analyzing and predicting the impact of mutations on protein function and disease pathophysiology.The study used dbSNP and Ensembl databases to obtain data on 343 nonsynonymous single nucleotide variants (nsSNVs) in the human AIMP2 gene. Six prediction algorithm tools were used to assess the effects of these nsSNVs on AIMP2's functions and structures. Results showed that 18 nsSNVs were located within functional domains, while 10 nsSNVs led to decreased protein stability. The structural and functional properties of the AIMP2 protein were investigated using databases such as Predict Protein, Mutpred2, and HOPE. ConSurf analysis provided information about conserved nsSNVs. GeneMANIA and STRING software tools were used to predict interactions between gene-gene and protein-protein, respectively. Phyre2 and I-TASSER web servers were used to predict the 3D structures of wild-type and mutant proteins.In addition, having the challenge of probable post-translational modification sites in the AIMP2, we made predictions using various bioinformatics tools. Consecuently, three minor mutations (L138Q, V161E, and I188N) and five major mutations (C23S, D121G, I122S, P128S, and W268S) were found to affect the AIMP2 protein's structure or function. Anyway, These mutations need to be further studied and confirmed through experimental investigation and GWAS studies.

Glial Origins of Inherited White Matter Disorders.

Inherited white matter disorders (IWMDs) are a phenotypically and genotypically heterogeneous group of disorders affecting the central nervous system (CNS) with or without peripheral neuropathy. They are classified either as leukodystrophies (LDs), with primary glial abnormalities, or genetic leukoencephalopathies (gLEs), where other CNS cells are involved. As a group, these disorders are common, with an incidence of 1 in 7500 births. However, IWMDs often go undiagnosed or suffer delayed or misdiagnosis due to their heterogeneous presentation. Many of these disorders present with lethal secondary manifestations that can be prevented through early disease recognition, periodic surveillance, and preventative management. Emerging therapeutics, including gene therapy trials for metachromatic leukodystrophy (MLD) and adrenoleukodystrophy (ALD), suggest disease progression may be slowed or even prevented if treated early. Therapies for IWMDs that target glial cells or the peripheral immune system may provide novel insights for treating acquired disorders of white matter.

Hypomyelination Leukodystrophy 16 (HLD16)-Associated Mutation p.Asp252Asn of TMEM106B Blunts Cell Morphological Differentiation.

Transmembrane protein 106B (TMEM106B), which is a type II transmembrane protein, is believed to be involved in intracellular dynamics and morphogenesis in the lysosome. TMEM106B is known to be a risk factor for frontotemporal lobar degeneration and has been recently identified as the receptor needed for the entry of SARS-CoV-2, independently of angiotensin-converting enzyme 2 (ACE2). A missense mutation, p.Asp252Asn, of TMEM106B is associated with hypomyelinating leukodystrophy 16 (HLD16), which is an oligodendroglial cell-related white matter disorder causing thin myelin sheaths or myelin deficiency in the central nervous system (CNS). However, it remains to be elucidated how the mutated TMEM106B affects oligodendroglial cells. Here, we show that the TMEM106B mutant protein fails to exhibit lysosome distribution in the FBD-102b cell line, an oligodendroglial precursor cell line undergoing differentiation. In contrast, wild-type TMEM106B was indeed localized in the lysosome. Cells harboring wild-type TMEM106B differentiated into ones with widespread membranes, whereas cells harboring mutated TMEM106B failed to differentiate. It is of note that the output of signaling through the lysosome-resident mechanistic target of rapamycin (mTOR) was greatly decreased in cells harboring mutated TMEM106B. Furthermore, treatment with hesperetin, a citrus flavonoid known as an activator of mTOR signaling, restored the molecular and cellular phenotypes induced by the TMEM106B mutant protein. These findings suggest the potential pathological mechanisms underlying HLD16 and their amelioration.

Macrophage transplantation rescues RNASET2-deficient leukodystrophy by replacing deficient microglia in a zebrafish model

RNASET2-deficient leukodystrophy is a rare infantile white matter disorder mimicking a viral infection and resulting in severe psychomotor impairments. Despite its severity, there is little understanding of cellular mechanisms of pathogenesis and no treatments. Recent research using the rnaset2 mutant zebrafish model has suggested that microglia may be the drivers of the neuropathology, due to their failure to digest apoptotic debris during neurodevelopment. Therefore, we developed a strategy for microglial replacement through transplantation of adult whole kidney marrow-derived macrophages into embryonic hosts. Using live imaging, we revealed that transplant-derived macrophages can engraft within host brains and express microglia-specific markers, suggesting the adoption of a microglial phenotype. Tissue-clearing strategies revealed the persistence of transplanted cells in host brains beyond embryonic stages. We demonstrated that transplanted cells clear apoptotic cells within the brain, as well as rescue overactivation of the antiviral response otherwise seen in mutant larvae. RNA sequencing at the point of peak transplant-derived cell engraftment confirms that transplantation can reduce the brain-wide immune response and particularly, the antiviral response, in rnaset2-deficient brains. Crucially, this reduction in neuroinflammation resulted in behavioral rescue-restoring rnaset2 mutant motor activity to wild-type (WT) levels in embryonic and juvenile stages. Together, these findings demonstrate the role of microglia as the cellular drivers of neuropathology in rnaset2 mutants and that macrophage transplantation is a viable strategy for microglial replacement in the zebrafish. Therefore, microglia-targeted interventions may have therapeutic benefits in RNASET2-deficient leukodystrophy.

Prevalence and Characteristics of Patients with Both White Matter Disorders and Peripheral Neuropathy Due to Inherited Versus Acquired Causes (P4-4.009)

Prevalence and Characteristics of Patients with Both White Matter Disorders and Peripheral Neuropathy Due to Inherited Versus Acquired Causes (P4-4.009)

From wernicke-korsakoff to central pontine myelinolysis: the potentially irreversible risks of alcohol use

Introduction Sustained alcohol intake, when combined with incomplete treatment, can result in chronic structural changes in the Central Nervous System, including generalized cortical and cerebellar atrophy, amnesic syndromes like Korsakoff’s syndrome, and white matter disorders such as Central Pontine Myelinolysis and Marchiafava-Bignami syndrome. It is crucial to prevent these complications due to their potential for irreversible and debilitating consequences. For Wernicke-Korsakoff syndrome, early recognition and thiamine administration for prevention are paramount, as it arises from thiamine deficiency due to malnutrition caused by persistent alcohol use. In the case of Central Pontine Myelinolysis, which is caused by abrupt fluctuations in serum osmolality, controlled sodium correction is essential.ObjectivesThrough a clinical case and a review of published literature, this study aims to reflect on the importance of preventing neurological injuries associated with chronic alcohol consumption, specifically Wernicke-Korsakoff Syndrome and Central Pontine Myelinolysis.Methods A literature review was conducted by searching for articles on PubMed using the terms “Alcohol Use Disorder,” “Wernicke-Korsakoff syndrome,” and “Central pontine myelinolysis.” A clinical case is presented, featuring a 50-year-old patient with alcohol use disorder who developed Wernicke-Korsakoff syndrome and Central Pontine Myelinolysis. Considering this case, we reflect on the primary approaches that could have been beneficial in preventing these complications and propose a straightforward method for doing so.Results A 50-year-old patient presented with poor general condition, characterized by low weight, significant loss of strength in the limbs and arms, and incoherent speech with anterograde amnesia and confabulation. This condition had progressed to a point where the patient could no longer walk, perform basic self-care tasks such as bathing, dressing, and eating independently, underscoring the severity of his condition. The diagnoses of Wernicke-Korsakoff syndrome and Central Pontine Myelinolysis were established based on clinical manifestations and the presence of hyperintense lesions observed in the central pons on T2/FLAIR axial MRI scans. This clinical case highlights the importance of proper and precocious prevention of complications in patients with alcohol use disorder. The foremost step in preventing these complications is to treat alcohol dependence effectively, even when faced with patient resistance. It’s vital to remain vigilant about potential complications and implement suitable prophylactic measures.ConclusionsThe devastating effects of complications arising from Alcohol Use Disorder, such as Wernicke-Korsakoff syndrome and Central Pontine Myelinolysis, underscore the importance of enhanced attention that clinicians should provide when approaching these patients at all clinical interactions.Disclosure of InterestNone Declared

Dominant CST3 variants cause adult onset leukodystrophy without amyloid angiopathy.

Leukodystrophies are rare genetic white matter disorders that have been regarded as mainly occurring in childhood. This perception has been altered in recent years, as a growing number of leukodystrophies have been described as having an onset in adulthood. Still, many adult patients presenting with white matter changes remain without a specific molecular diagnosis. We describe a novel adult onset leukodystrophy in 16 patients from eight families carrying one of four different stop-gain or frameshift dominant variants in the CST3 gene. Clinical and radiological features differ markedly from the previously described Icelandic cerebral amyloid angiopathy found in patients carrying p.Leu68Asn substitution in CST3. The clinical phenotype consists of recurrent episodes of hemiplegic migraine associated with transient unilateral focal deficits and slowly progressing motor symptoms and cognitive decline in mid to older adult ages. In addition, in some cases acute onset clinical deterioration led to a prolonged episode with reduced consciousness and even early death. Radiologically, pathognomonic changes are found at typical predilection sites involving the deep cerebral white matter sparing a periventricular and directly subcortical rim, the middle blade of corpus callosum, posterior limb of the internal capsule, middle cerebellar peduncles, cerebral peduncles and specifically the globus pallidus. Histopathologic characterization in two autopsy cases did not reveal angiopathy, but instead micro- to macrocystic degeneration of the white matter. Astrocytes were activated at early stages and later displayed severe degeneration and loss. In addition, despite the loss of myelin, elevated numbers of partly apoptotic oligodendrocytes were observed. A structural comparison of the variants in CST3 suggests that specific truncations of cystatin C result in an abnormal function, possibly by rendering the protein more prone to aggregation. Future studies are required to confirm the assumed effect on the protein and to determine pathophysiologic downstream events at the cellular level.

Primary Microgliopathy Presenting as Degenerative Dementias: A Case Series of Novel Gene Mutations from India

Introduction: Microglia exert a crucial role in homeostasis of white matter integrity, and several studies highlight the role of microglial dysfunctions in neurodegeneration. Primary microgliopathy is a disorder where the pathogenic abnormality of the microglia causes white matter disorder and leads to a neuropsychiatric disease. Triggering receptor expressed on myeloid cells (TREM2), TYRO protein tyrosine kinase binding protein (TYROBP) and colony-stimulating factor 1 receptor (CSF1R) are genes implicated in primary microgliopathy. The clinical manifestations of primary microgliopathy are myriad ranging from neuropsychiatric syndrome, motor disability, gait dysfunction, ataxia, pure dementia, frontotemporal dementia (FTD), Alzheimer’s dementia (AD), and so on. It becomes imperative to establish the diagnosis of microgliopathy masquerading as degenerative dementia, especially with promising therapies on horizon for the same. We aimed to describe a case series of subjects with dementia harbouring novel genes of primary microgliopathy, along with their clinical, neuropsychological, cognitive profile and radiological patterns. Methods: The prospective study was conducted in a university referral hospital in South India, as a part of an ongoing clinico-genetic research on dementia subjects, and was approved by the Institutional Ethics Committee. All patients underwent detailed assessment including sociodemographic profile, clinical and cognitive assessment, pedigree analysis and comprehensive neurological examination. Subjects consenting for blood sampling underwent genetic testing by whole-exome sequencing (WES). Results: A total of 100 patients with dementia underwent genetic analysis using WES and three pathogenic variants, one each of TREM2, TYROBP, and CSF1R and two variants of uncertain significance in CSF1R were identified as cause of primary microgliopathy. TREM2 and TYROBP presented as frontotemporal syndrome whereas CSF1R presented as frontotemporal syndrome and as AD. Conclusion: WES has widened the spectrum of underlying neuropathology of degenerative dementias, and diagnosing primary microglial dysfunction with emerging therapeutic options is of paramount importance. The cases of primary microgliopathy due to novel mutations in TREM2, TYROBP, and CSF1R with the phenotype of degenerative dementia are being first time reported from Indian cohort. Our study enriches the spectrum of genetic variants implicated in degenerative dementia and provides the basis for exploring complex molecular mechanisms like microglial dysfunction, as underlying cause for neurodegeneration.

Magnetic resonance fingerprinting-based myelin water fraction mapping for the assessment of white matter maturation and integrity in typical development and leukodystrophies.

A quantitative biomarker for myelination, such as myelin water fraction (MWF), would boost the understanding of normative and pathological neurodevelopment, improving patients' diagnosis and follow-up. We quantified the fraction of a rapidly relaxing pool identified as MW using multicomponent three-dimensional (3D) magnetic resonance fingerprinting (MRF) to evaluate white matter (WM) maturation in typically developing (TD) children and alterations in leukodystrophies (LDs). We acquired DTI and 3D MRF-based R1, R2 and MWF data of 15 TD children and 17 LD patients (9 months-12.5 years old) at 1.5 T. We computed normative maturation curves in corpus callosum and corona radiata and performed WM tract profile analysis, comparing MWF with R1, R2 and fractional anisotropy (FA). Normative maturation curves demonstrated a steep increase for all tissue parameters in the first 3 years of age, followed by slower growth for MWF while R1, R2R2 and FA reached a plateau. Unlike FA, MWF values were similar for regions of interest (ROIs) with different degrees of axonal packing, suggesting independence from fiber bundle macro-organization and higher myelin specificity. Tract profile analysis indicated a specific spatial pattern of myelination in the major fiber bundles, consistent across subjects. LD were better distinguished from TD by MWF rather than FA, showing reduced MWF with respect to age-matched controls in both ROI-based and tract analysis. In conclusion, MRF-based MWF provides myelin-specific WM maturation curves and is sensitive to alteration due to LDs, suggesting its potential as a biomarker for WM disorders. As MRF allows fast simultaneous acquisition of relaxometry and MWF, it can represent a valuable diagnostic tool to study and follow up developmental WM disorders in children.

Chapter 7 - White matter disorders with cerebral calcification in adulthood

This chapter provides a comprehensive overview of adult-onset leukoencephalopathies with cerebral calcification (CC), emphasizing the importance of age at presentation, systemic clinical features, and neuroimaging patterns for accurate diagnosis. CC is a multifaceted phenomenon associated with various neurologic, developmental, metabolic, and genetic conditions, as well as normal aging. Here, we explore the distinction between primary familial brain calcification (PFBC) and secondary forms, including metabolic and mitochondrial causes. We discuss genetic causes, e.g., SLC20A2, XPR1, PDGFB, PDGFRB, MYORG, NAA60 and JAM2, in the context of autosomal dominant and recessive PFBC and other inherited conditions. The chapter delineates the diagnostic approach involving family history, clinical assessments, and detailed investigations of calcium-phosphate metabolism. Neuroimaging modalities, including computed tomography and magnetic resonance imaging, are crucial for assessing calcification patterns and localizations. Genetic testing, especially next-generation sequencing, plays a pivotal role in providing a final molecular diagnosis. The management of patients with CC encompasses symptomatic treatment and cause-specific approaches, requiring a multidisciplinary care approach. In conclusion, this chapter highlights the complexity of leukoencephalopathies with CC, emphasizing the need for integrated and evolving management to optimize patient care.

Chapter 15 - Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia

Adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is an adult-onset, inherited white matter disorder encompassing two previously identified clinicopathologically similar entities: pigmentary orthochromatic leukodystrophy (POLD) and hereditary diffuse leukoencephalopathy with spheroids (HDLS). In this chapter, we discuss how advances in our genetic understanding of the condition have further delineated three distinct clinical entities within ALSP, namely CSF1R-related ALSP, AARS2-related leukoencephalopathy (AARS2-L), and AARS (HDLS-S). We provide descriptions of the clinical, radiologic, pathologic, and pathophysiologic findings in each entity, detailing their similarities and differences, and discuss current and future treatment options where available.

Chapter 22 - Adult inflammatory leukoencephalopathies

Inflammatory white matter disorders may commonly mimic genetic leukoencephalopathies. These include atypical presentations of common conditions, such as multiple sclerosis, together with rare inflammatory disorders. A structured approach to such cases is essential, together with judicious use of the many available diagnostic biomarkers. The potential for such conditions to respond to immunotherapy emphasizes the importance of an accurate and prompt diagnosis in improving patient outcomes.

Chapter 6 - Childhood-inherited white matter disorders with calcification

Intracranial calcification (ICC) occurs in many neurologic disorders both acquired and genetic. In some inherited white matter disorders, it is a common or even invariable feature where the presence and pattern of calcification provides an important pointer to the specific diagnosis. This is particularly the case for the Aicardi-Goutières syndrome (AGS) and for Coats plus (CP) and leukoencephalopathy with calcifications and cysts (LCC), which are discussed in detail in this chapter. AGS is a genetic disorder of type 1 interferon regulation, caused by mutations in any of the nine genes identified to date. In its classic form, AGS has very characteristic clinical and neuroimaging features which will be discussed here. LCC is a purely neurologic disorder caused by mutations in the SNORD118 gene, whereas CP is a multisystem disorder of telomere function that may result from mutations in the CTC1, POT1, or STN genes. In spite of the different pathogenetic basis for LCC and CP, they share remarkably similar neuroimaging and neuropathologic features. Cockayne syndrome, in which ICC is usually present, is discussed elsewhere in this volume. ICC may occur as an occasional feature of many other white matter diseases, including Alexander disease, Krabbe disease, X-ALD, and occulodentodigital dysplasia.

Chapter 1 - Neuropathology of white matter disorders

The hallmark neuropathologic feature of all leukodystrophies is depletion or alteration of the white matter of the central nervous system; however increasing genetic discoveries highlight the genetic heterogeneity of white matter disorders. These discoveries have significantly helped to advance the understanding of the complexity of molecular mechanisms involved in the biogenesis and maintenance of healthy white matter. Accordingly, genetic discoveries and functional studies have enabled us to firmly establish that multiple distinct structural defects can lead to white matter pathology. Leukodystrophies can develop not only due to defects in proteins essential for myelin biogenesis and maintenance or oligodendrocyte function, but also due to mutations encoding myriad of proteins involved in the function of neurons, astrocytes, microglial cells as well as blood vessels. To a variable extent, some leukodystrophies also show gray matter, peripheral nervous system, or multisystem involvement. Depending on the genetic defect and its role in the formation or maintenance of the white matter, leukodystrophies can present either in early childhood or adulthood. In this chapter, the classification of leukodystrophies will be discussed from the cellular defect point of view, followed by a description of known neuropathologic alterations for all leukodystrophies.