Adult Leukodystrophies: A Step-by-Step Diagnostic Approach

Burden of illness and mortality in men with Adrenomyeloneuropathy: a retrospective cohort study

BACKGROUND

Adrenomyeloneuropathy (AMN) is a neurodegenerative disease phenotype of X-linked adrenoleukodystrophy (ALD), resulting in progressive myeloneuropathy causing spastic paraparesis, sensory ataxia, and bowel/bladder symptoms. We conducted a retrospective cohort study using two large administrative databases to characterize mortality and the burden of illness in adult men with AMN in the US.

RESULTS

Healthcare resource use was assessed using a national commercial insurance claims database (2006-2021). Males with AMN ages 18-64 years and no evidence of cerebral ALD or other peroxisomal disorders were included and 1:4 matched on demographic characteristics to individuals without AMN. All study participants were followed for as long as observable. Patients with AMN were also identified in the Medicare Limited Dataset (2017-2022); mortality and age at death were compared with all Medicare enrollees. We identified 303 commercially insured men with AMN. Compared with non-AMN, individuals with AMN had significantly more inpatient hospital admissions (0.44 vs. 0.04 admissions/patient/year), outpatient clinic (8.88 vs. 4.1 visits/patient/year), outpatient hospital (5.33 vs. 0.99 visits/patient/year), and home healthcare visits (4.66 vs. 0.2 visits/patient/year), durable medical equipment claims (0.7 vs. 0.1 claims/patient/year), and prescription medication fills (18.1 vs. 5.4 fills/patient/year) (all p < 0.001). Average length-of-stay per hospitalization was also longer in AMN (8.88 vs. 4.3 days; p < 0.001). Rates of comorbidities were significantly more common in AMN compared to controls, including peripheral vascular disease (4.6% vs. 0.99%), chronic pulmonary disease (6.3% vs. 2.6%), and liver disease (5.6% vs. 0.88%), all p < 0.001. Among individuals age < 65 with Medicare disability coverage, mortality rates were 5.3x higher for adult AMN males (39.3% vs. 7.4%) and the age at death significantly younger (47.0 ± 11.3 vs. 56.5 ± 7.8 years), both p < 0.001. Among Medicare beneficiaries ages ≥ 65 mortality rates were 2.2x higher for men with AMN vs. those without AMN (48.6% vs. 22.4%), p < 0.001.

CONCLUSION

AMN imposes a substantial and underrecognized health burden on men, with higher healthcare utilization, greater medical comorbidity, higher mortality rates, and younger age at death.

Brainstem Chipmunk Sign: A Diagnostic Imaging Clue across All Subtypes of Alexander Disease

BACKGROUND AND PURPOSE

While classic brain MR imaging features of Alexander disease have been well-documented, lesional patterns can overlap with other leukodystrophies, especially in the early stages of the disease or in milder phenotypes. We aimed to assess the utility of a new neuroimaging sign to help increase the diagnostic specificity of Alexander disease.

MATERIALS AND METHODS

A peculiar bilateral symmetric hyperintense signal on T2-weighted images affecting the medulla oblongata was identified in an index patient with type I Alexander disease. Subsequently, 5 observers performed a systematic MR imaging review for this pattern by examining 55 subjects with Alexander disease and 74 subjects with other leukodystrophies. Interobserver agreement was assessed by the κ index. Sensitivity, specificity, and receiver operating characteristic curves were determined.

RESULTS

The identified pattern was present in 87% of subjects with Alexander disease and 14% of those without Alexander disease leukodystrophy (P < .001), 3 with vanishing white matter, 4 with adult polyglucosan body disease, and 3 others. It was found equally in both type I and type II Alexander disease (28/32, 88% versus 18/21, 86%; P = .851) and in subjects with unusual disease features (2/2). Sensitivity (87.3%; 95% CI, 76.0%-93.7%), specificity (86.5%; 95% CI, 76.9%-92.5%), and interobserver agreement (κ index = 0.82) were high.

CONCLUSIONS

The identified pattern in the medulla oblongata, called the chipmunk sign due to its resemblance to the face of this rodent, is extremely common in subjects with Alexander disease and represents a diagnostic tool that can aid in early diagnosis, especially in subjects with otherwise atypical MR imaging findings and/or clinical features.

Differential diagnosis between multiple sclerosis and leukodystrophies - A scoping review

Multiple Sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS) characterized by damage to the myelin sheaths of oligodendrocytes. Currently, there is no specific biomarker to identify the disease; however, a diagnostic criterion has been established based on patient's clinical, laboratory, and imaging characteristics, which assists in identifying this condition. The primary method for diagnosing MS is the McDonald criteria, first described in 2001 and revised in the years 2005, 2012, and 2017. These criteria have been continuously reviewed to enhance specificity and sensitivity in the diagnosis of MS, thereby reducing errors in its differential diagnosis. An important differential diagnosis that shares overlapping features with MS, mainly the progressive forms, are leukodystrophies with demyelination as underlying pathology. Leukodystrophies comprise a rare group of genetically determined disorders that lead to either demyelination or hypomyelination of the central nervous system that can result neuroimaging changes as well as clinical findings similar to those observed in MS. Thus, systematic evaluation encompassing clinical presentation, neuroimaging findings, and laboratory metrics proves indispensable for a differential diagnosis. As such, this study aimed to establish, clearly and objectively, the similarities and differences between MS and the main demyelinating leukodystrophies. The study analyzed the parameters of the McDonald criteria, including clinical, laboratory, and magnetic resonance imaging aspects, as found in patients with leukodystrophies through scoping literature review. The data were compared with the determinations of the revised 2017 McDonald criteria to facilitate the differential diagnosis of these diseases in clinical practice.

Leukodystrophy Imaging: Insights for Diagnostic Dilemmas

Leukodystrophies, a group of rare demyelinating disorders, mainly affect the CNS. Clinical presentation of different types of leukodystrophies can be nonspecific, and thus, imaging techniques like MRI can be used for a more definitive diagnosis. These diseases are characterized as cerebral lesions with characteristic demyelinating patterns which can be used as differentiating tools. In this review, we talk about these MRI study findings for each leukodystrophy, associated genetics, blood work that can help in differentiation, emerging diagnostics, and a follow-up imaging strategy. The leukodystrophies discussed in this paper include X-linked adrenoleukodystrophy, metachromatic leukodystrophy, Krabbe's disease, Pelizaeus-Merzbacher disease, Alexander's disease, Canavan disease, and Aicardi-Goutières Syndrome.

Triple Genetic Diagnosis in a Patient with Late-Onset Leukodystrophy and Mild Intellectual Disability

We describe the complex case of a 44-year-old man with polycystic kidney disease, mild cognitive impairment, and tremors in the upper limbs. Brain MRI showed lesions compatible with leukodystrophy. The diagnostic process, which included clinical exome sequencing (CES) and chromosomal microarray analysis (CMA), revealed a triple diagnosis: autosomal dominant polycystic kidney disease (ADPKD) due to a pathogenic variant, c.2152C>T-p.(Gln718Ter), in the PKD1 gene; late-onset phenylketonuria due to the presence of two missense variants, c.842C>T-p.(Pro281Leu) and c.143T>C-p.(Leu48Ser) in the PAH gene; and a 915 Kb duplication on chromosome 15. Few patients with multiple concurrent genetic diagnoses are reported in the literature; in this ADPKD patient, genome-wide analysis allowed for the diagnosis of adult-onset phenylketonuria (which would have otherwise gone unnoticed) and a 15q11.2 duplication responsible for cognitive and behavioral impairment with incomplete penetrance. This case underlines the importance of clinical genetics for interpreting complex results obtained by genome-wide techniques, and for diagnosing concurrent late-onset monogenic conditions.

Case 318: Adult Polyglucosan Body Disease

HISTORY

A 72-year-old man sought care for a cognitive deterioration over the past 5 years. There was a documented decline in his performance on the Mini-Mental State Examination (30 of 30 in 2016, 23 of 30 in 2021), with mainly episodic memory impairment. A more detailed history revealed a gait problem, paresthesia in both feet, and nocturnal urinary frequency. Clinical examination findings were suggestive of a length-dependent polyneuropathy. In addition, a right-sided Babinski sign was noted. Electromyography and a nerve conduction study corroborated a peripheral axonal sensorimotor neuropathy. MRI of the brain was performed.

Adult-onset Alexander disease with brainstem and cervical cord enhancing lesions

Leukodystrophies are a group of genetic diseases with diverse clinical features and prominent involvement of the central nervous system white matter. We describe a 27-year-old man who presented with a progressive neurological disease, and striking involvement of the brainstem and symmetrical white matter lesions on MR scanning. Having excluded several other causes of leukodystrophy, we confirmed Alexander disease when a genetic panel showed a probable pathogenic variant in GFAP: p.Leu359Pro. Clinicians should suspect Alexander disease in people with a progressive neurological motor decline who has pyramidal and bulbar signs and compatible neuroimaging.

Case 317: Adult-Onset Leukoencephalopathy with Axonal Spheroids and Pigmented Glia

HISTORY

A 44-year-old previously healthy man with a 9-month history of progressive cognitive decline, depression, urinary incontinence, and inability to perform tasks of daily living presented to the emergency department with worsening cognitive and neuropsychiatric symptoms. He had become more distressed, and his family noticed him departing the house without closing doors, leaving water faucets running, and sending his children to school on Sundays. History taken from the patient's wife revealed that his brother had passed away in his late 30s after a slowly progressing functional and cognitive decline over the course of 5 years. No further detailed family history could be obtained. The review of systems was negative; he had no prior medical, psychiatric, or surgical history; and he denied any history of recent travel, camping, hiking, or vaccination. The patient was not taking any dietary supplements, nor was he taking any over-the-counter or prescription medication. Examination revealed vital signs were within normal limits. Neurocognitive assessment revealed a conscious, coherent, and alert patient with impaired memory and concentration. He showed poor attention, depressed mood, and restricted affect. He was unable to spell the word world forward, nor was he able to understand a request to spell it backward. The rest of the physical and neurologic examination revealed no abnormalities. Extensive laboratory work-up was conducted and included the following: toxicology screening; screening for HIV-1, HIV-2, and syphilis treponemal antibodies; COVID-19 polymerase chain reaction; and measurement of B1 and B12 levels. The results of screening were negative. Cerebrospinal fluid (CSF) assays, including CSF oligoclonal bands and CSF flow cytometry, revealed values within normal limits. CT of the brain without intravenous contrast material was performed in the emergency department to rule out acute intracranial abnormality. Multiplanar multisequence MRI of the brain without and with intravenous contrast material was ordered for further assessment. CT images of chest, abdomen, and pelvis were unremarkable (images not shown).

Clinical, genetic, and molecular characteristics in a central-southern Chinese cohort of genetic leukodystrophies

OBJECTIVE

Leukodystrophies are a diverse group of rare inherited disorders that affect the white matter of the central nervous system with a wide phenotypic spectrum. We aimed to characterize the clinical and genetic features of leukodystrophies in a central-southern Chinese cohort.

METHODS

A cohort of 16 Chinese probands with leukodystrophy was recruited and performed genetic analysis by targeted panels or whole-exome sequencing. Further functional analysis of identified mutations in the colony stimulating factor 1 receptor (CSF1R) gene was explored.

RESULTS

A total of eight pathogenic variants (3 novel, 5 documented) were identified in genes including AARS2, ABCD1, CSF1R, and GALC. Common symptoms of leukodystrophy such as cognitive decline, behavioral symptoms, bradykinesia, and spasticity were observed in mutation carriers as well as other rare features (e.g., seizure, dysarthric, and vision impairment). Overexpressing CSF1R mutants p.M875I and p.F971Sfs*7 in vitro showed pronounced cleavage CSF1R and suppressed protein expression, respectively, and reduced transcripts of both mutants were observed. CSF1 treatment revealed deficient and suppressed CSF1R phospho-activation with the mutants. In contrast to the plasma membrane and endoplasmic reticulum (ER) localized wild-type CSF1R, M875I mutant showed much less membrane association and greater detainment in the ER, whereas F971Sfs*7 mutation led to aberrant non-ER localization. Both mutations caused suppressed cell viability, which was partially resulted from deficient/suppressed CSF1R-ERK signaling.

INTERPRETATION

In summary, our findings expand the mutation spectrum of these genes in leukodystrophies. Supported by in vitro validation of the pathogenicity of heterozygous CSF1R mutations, our data also provide insights into the pathogenic mechanisms of CSF1R-related leukodystrophy.

Recurrent Ischemic Strokes due to Monogenic COL4A1 Mutation: The First Case Report from Latin America

Introduction. Monogenic mutations as the cause of recurrent ischemic cerebral small-vessel disease with leukodystrophy are rare. COL4A1 gene mutations are a relatively new etiology of cerebrovascular lesions in young adults; however, any patient has been reported from Latin America. Case Presentation. We presented a Mexican young female with leukodystrophy and recurrent stroke secondary to COL4A1 monogenic mutation. Discussion/Conclusion. COL4A1 monogenic mutations are associated with cerebral small-vessel disease and other systemic manifestations. To date, there is little evidence to justify the treatment and prevention of recurrent strokes in patients with this mutation.

Extension of the Clinicoradiologic Spectrum of Newly Described End-Truncating LAMB1 Variations

Objectives

To refine the clinical spectrum of a very recently identified phenotype associated with LAMB1 end-truncating pathogenic variations.

Methods

Detailed clinical, neuropsychological, and MRI investigation of 6 patients from 2 unrelated families segregating end-truncating LAMB1 variations.

Results

All patients harbored a LAMB1 end-truncating pathogenic variation. The specific association of a hippocampal type episodic memory dysfunction and a diffuse leukoencephalopathy was observed in all 4 patients aged older than 50 years, slightly worsening over time in 2 patients with several years of follow-up. Additional unspecific neurologic symptoms are reported, such as episodes of numbness, language troubles, or faintness in these 4 patients and the 2 younger ones.

Discussion

The association of an extensive leukoencephalopathy with an episodic memory dysfunction of the hippocampal type is strongly suggestive of a LAMB1 end-truncating variation in adults older than 50 years. Early cognitive complaints and imaging abnormalities might exist decades before. Additional transient manifestations can be observed, and this association should lead to LAMB1 screening to avoid unnecessary invasive investigations.

Spinal muscular atrophy-like phenotype in a mouse model of acid ceramidase deficiency

Mutations in ASAH1 have been linked to two allegedly distinct disorders: Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). We have previously reported FD-like phenotypes in mice harboring a single amino acid substitution in acid ceramidase (ACDase), P361R, known to be pathogenic in humans (P361R-Farber). Here we describe a mouse model with an SMA-PME-like phenotype (P361R-SMA). P361R-SMA mice live 2-3-times longer than P361R-Farber mice and have different phenotypes including progressive ataxia and bladder dysfunction, which suggests neurological dysfunction. We found profound demyelination, loss of axons, and altered sphingolipid levels in P361R-SMA spinal cords; severe pathology was restricted to the white matter. Our model can serve as a tool to study the pathological effects of ACDase deficiency on the central nervous system and to evaluate potential therapies for SMA-PME.

Solving inherited white matter disorder etiologies in the neurology clinic: Challenges and lessons learned using next-generation sequencing

Introduction

Rare neurodevelopmental disorders, including inherited white matter disorders or leukodystrophies, often present a diagnostic challenge on a genetic level given the large number of causal genes associated with a range of disease subtypes. This study aims to demonstrate the challenges and lessons learned in the genetic investigations of leukodystrophies through presentation of a series of cases solved using exome or genome sequencing.

Methods

Each of the six patients had a leukodystrophy associated with hypomyelination or delayed myelination on MRI, and inconclusive clinical diagnostic genetic testing results. We performed next generation sequencing (case-based exome or genome sequencing) to further investigate the genetic cause of disease.

Results

Following different lines of investigation, molecular diagnoses were obtained for each case, with patients harboring pathogenic variants in a range of genes including TMEM106B, GJA1, AGA, POLR3A, and TUBB4A. We describe the lessons learned in reaching the genetic diagnosis, including the importance of (a) utilizing proper multi-gene panels in clinical testing, (b) assessing the reliability of biochemical assays in supporting diagnoses, and (c) understanding the limitations of exome sequencing methods in regard to CNV detection and region coverage in GC-rich areas.

Discussion

This study illustrates the importance of applying a collaborative diagnostic approach by combining detailed phenotyping data and metabolic results from the clinical environment with advanced next generation sequencing analysis techniques from the research environment to increase the diagnostic yield in patients with genetically unresolved leukodystrophies.

Clinical Reasoning: A Young Man With Subacute Onset of Spastic Paraparesis

Leukodystrophies are a group of rare neurodegenerative disorders, usually presenting in infancy with a variable combination of cognitive, motor, and coordination impairment. Adult-onset cases are even more rare, often representing a diagnostic challenge even for experienced neurologists. Here, we present a case of a 44-year-old man with subacute and rapidly progressive spastic paraplegia, whose brain MRI revealed white matter abnormalities compatible with a diagnosis of leukodystrophy. We discuss how to apply a simplified diagnostic algorithm to distinguish acquired leukoencephalopathies from leukodystrophies and how to delve into the maze of genetic testing for white matter diseases. In our patient, we reached the diagnosis of a treatable disorder, whose early recognition is essential to prevent severe neurologic deterioration.

Recognizing early MRI signs (or their absence) is crucial in diagnosing metachromatic leukodystrophy

OBJECTIVES

Metachromatic leukodystrophy (MLD) has characteristic white matter (WM) changes on brain MRI, which often trigger biochemical and genetic confirmation of the diagnosis. In early or pre-symptomatic disease stages, these typical MRI changes might be absent, hampering early diagnosis. This study aims to describe the characteristics of MRI WM abnormalities at diagnosis, related to clinical presentation.

METHODS

We retrospectively reviewed brain MRIs of MLD patients followed in 2 centers at the time of diagnosis regarding MLD MRI score and presence of tigroid pattern. In addition, MLD subtype, symptom status, CNS/PNS phenotype, motor/cognitive/mixed phenotype, and the presence of CNS symptoms were evaluated.

RESULTS

We included 104 brain MRIs from patients with late-infantile (n = 43), early-juvenile (n = 24), late-juvenile (n = 20) and adult (n = 17) onset. Involvement of the corpus callosum was a characteristic early MRI sign and was present in 71% of the symptomatic late-infantile patients, 94% of the symptomatic early-juvenile patients and 100% of the symptomatic late-juvenile and adult patients. Symptomatic early-juvenile, late-juvenile and adult patients generally had WM abnormalities on MRI suggestive of MLD. By contrast, 47% of the early-symptomatic late-infantile patients had no or only mild WM abnormalities on MRI, even in the presence of CNS symptoms including pyramidal signs.

INTERPRETATION

Patients with late-infantile MLD may have no or only mild, nonspecific abnormalities at brain MRI, partly suggestive of 'delayed myelination', even with clear clinical symptoms. This may lead to significant diagnostic delay. Knowledge of these early MRI signs (or their absence) is important for fast diagnosis.

ABCD1 Gene Mutations: Mechanisms and Management of Adrenomyeloneuropathy

Pathogenic variants in the ABCD1 gene on the X chromosome may result in widely heterogenous phenotypes, including adrenomyeloneuropathy (AMN). Affected males typically present in their third or fourth decade of life with progressive lower limb weakness and spasticity, and may develop signs and symptoms of adrenal insufficiency and/or cerebral demyelination. Heterozygous females may be asymptomatic, but may develop a later-onset and more slowly progressive spastic paraparesis. In this review, we describe the clinical presentation of AMN, as well as its diagnosis and management. The role of rehabilitative therapies and options for management of spasticity are highlighted.

Case Report: Novel CSF1R Variant in a Patient With Behavioral Variant Frontotemporal Dementia Syndrome With Prodromal Repetitive Scratching Behavior

CSF1R-related leukoencephalopathy is an autosomal dominant neurodegenerative disease caused by mutations in the tyrosine kinase domain of the colony stimulating factor 1 receptor (CSF1R). Several studies have found that hematogenic stem cell transplantation is an effective disease modifying therapy however the literature regarding prodromal and early symptoms CSF1R-related leukoencephalopathy is limited. We describe a 63-year-old patient with 4 years of repetitive scratching and skin picking behavior followed by 10 years of progressive behavioral, cognitive, and motor decline in a pattern suggesting behavioral variant of frontotemporal dementia. Brain MRI demonstrated prominent frontal and parietal atrophy accompanied by underlying bilateral patchy white matter hyperintensities sparing the U fibers and cavum septum pellucidum. Whole-exome sequencing revealed a novel, predicted deleterious missense variant in a highly conserved amino acid in the tyrosine kinase domain of CSF1R (p.Gly872Arg). Given this evidence and the characteristic clinical and radiological findings this novel variant was classified as likely pathogenic according to the American College of Medical Genetics standard guidelines. Detailed description of the prodromal scratching and skin picking behavior and possible underlying mechanisms in this case furthers knowledge about early manifestations of CSF1R-related leukoencephalopathy with the hope that early detection and timely administration of disease modifying therapies becomes possible.

The Primary Microglial Leukodystrophies: A Review

Primary microglial leukodystrophy or leukoencephalopathy are disorders in which a genetic defect linked to microglia causes cerebral white matter damage. Pigmented orthochromatic leukodystrophy, adult-onset orthochromatic leukodystrophy associated with pigmented macrophages, hereditary diffuse leukoencephalopathy with (axonal) spheroids, and adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) are different terms apparently used to designate the same disease. However, ALSP linked to dominantly inherited mutations in CSF1R (colony stimulating factor receptor 1) cause CSF-1R-related leukoencephalopathy (CRP). Yet, recessive ALSP with ovarian failure linked to AARS2 (alanyl-transfer (t)RNA synthase 2) mutations (LKENP) is a mitochondrial disease and not a primary microglial leukoencephalopathy. Polycystic membranous lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL; Nasu–Hakola disease: NHD) is a systemic disease affecting bones, cerebral white matter, selected grey nuclei, and adipose tissue The disease is caused by mutations of one of the two genes TYROBP or TREM2, identified as PLOSL1 and PLOSL2, respectively. TYROBP associates with receptors expressed in NK cells, B and T lymphocytes, dendritic cells, monocytes, macrophages, and microglia. TREM2 encodes the protein TREM2 (triggering receptor expressed on myeloid cells 2), which forms a receptor signalling complex with TYROBP in macrophages and dendritic cells. Rather than pure microglial leukoencephalopathy, NHD can be considered a multisystemic “immunological” disease.

Case Report: MRI, Clinical, and Pathological Correlates of Bromethalin Toxicosis in Three Dogs

Bromethalin toxicosis is an increasingly common clinical presentation in dogs that may be fatal depending on the extent of intoxication. Antemortem diagnosis of bromethalin toxicosis was achieved in three dogs by demonstration of the active metabolite desmethylbromethalin in fat or serum. Magnetic resonance imaging (MRI) findings were consistent with a diffuse leukoencephalopathy with restricted diffusion and prominent involvement of the corticospinal motor tracts on T2-weighted and diffusion-weighted sequences. Imaging findings were confirmed in one non-surviving dog at necropsy. Resolution of MRI abnormalities was demonstrated in one surviving dog that was consistent with the associated resolution of clinical signs. Initial findings in these dogs support further investigation of specific MRI patterns in cases of leukoencephalopathy to aid differential diagnosis. While antemortem detection of bromethalin and its metabolites confirms exposure, quantitation may be informative as a prognostic biomarker.

Neuroimaging phenotypes of CSF1R-related leukoencephalopathy: Systematic review, meta-analysis, and imaging recommendations

Colony-stimulating factor 1 receptor (CSF1R)-related leukoencephalopathy is a rare but fatal microgliopathy. The diagnosis is often delayed due to multifaceted symptoms that can mimic several other neurological disorders. Imaging provides diagnostic clues that help identify cases. The objective of this study was to integrate the literature on neuroimaging phenotypes of CSF1R-related leukoencephalopathy. A systematic review and meta-analysis were performed for neuroimaging findings of CSF1R-related leukoencephalopathy via PubMed, Web of Science, and Embase on 25 August 2021. The search included cases with confirmed CSF1R mutations reported under the previous terms hereditary diffuse leukoencephalopathy with spheroids, pigmentary orthochromatic leukodystrophy, and adult-onset leukoencephalopathy with axonal spheroids and pigmented glia. In 78 studies providing neuroimaging data, 195 cases were identified carrying CSF1R mutations in 14 exons and five introns. Women had a statistically significant earlier age of onset (p = 0.041, 40 vs 43 years). Mean delay between symptom onset and neuroimaging was 2.3 years. Main magnetic resonance imaging (MRI) findings were frontoparietal white matter lesions, callosal thinning, and foci of restricted diffusion. The hallmark computed tomography (CT) finding was white matter calcifications. Widespread cerebral hypometabolism and hypoperfusion were reported using positron emission tomography and single-photon emission computed tomography. In conclusion, CSF1R-related leukoencephalopathy is associated with progressive white matter lesions and brain atrophy that can resemble other neurodegenerative/-inflammatory disorders. However, long-lasting diffusion restriction and parenchymal calcifications are more specific findings that can aid the differential diagnosis. Native brain CT and brain MRI (with and without a contrast agent) are recommended with proposed protocols and pictorial examples are provided.

Adult-Onset Leukoencephalopathy With Axonal Spheroids and Pigmented Glia: Review of Clinical Manifestations as Foundations for Therapeutic Development

A comprehensive review of published literature was conducted to elucidate the genetics, neuropathology, imaging findings, prevalence, clinical course, diagnosis/clinical evaluation, potential biomarkers, and current and proposed treatments for adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), a rare, debilitating, and life-threatening neurodegenerative disorder for which disease-modifying therapies are not currently available. Details on potential efficacy endpoints for future interventional clinical trials in patients with ALSP and data related to the burden of the disease on patients and caregivers were also reviewed. The information in this position paper lays a foundation to establish an effective clinical rationale and address the clinical gaps for creation of a robust strategy to develop therapeutic agents for ALSP, as well as design future clinical trials, that have clinically meaningful and convergent endpoints.

Functional electrical stimulation to aid walking in patients with adrenomyeloneuropathy: A case study and observational series

Adrenomyeloneuropathy (AMN) is a rare inherited condition where affected individuals develop slowly progressive spastic paraparesis with a gradual decline in walking ability. There is no cure for AMN and treatment focuses on supportive measures and aids. One treatment option is functional electrical stimulation (FES), a treatment, approved by The National Institute for Health and Care Excellence (NICE), for managing foot drop in upper motor neuron disorders. Limited evidence exists for its use in AMN patients. We describe the effects of FES in an individual case and more broadly within a cohort of 21 patients successfully treated with FES. Patients with AMN referred for FES typically report frequent falls (71%) and foot drop (57%) as the most common barriers to walking. When using FES, walking speed at baseline (0.70 m/s [SD = 0.2]) was maintained at the 2-year review (0.68 m/s [SD = 0.2]) with a persistent orthotic effect (improvement in walking speed when device on vs. off) seen from wearing FES over the same 2-year period (11%-19%). Patient walking satisfaction (visual analogue scale: 0 - very dissatisfied; 10 - very satisfied) was also greater when comparing no-FES versus FES over the same period (Year 1: 2.5 vs. 7.7; Year 2: 2.1 vs. 6.1). FES is not effective in all patients. Twelve patients referred found no benefit from the device; although there was no clear evidence, this was related to the degree of AMN associated peripheral neuropathy. However, FES is a safe, cost-effective treatment option and should be considered, along with assessment in a multidisciplinary clinic, for all AMN patients with walking difficulties.

Inborn Errors of Metabolism Screening in Neonates: Current Perspective with Diagnosis and Therapy

Inborn errors of metabolism (IEMs) are rare hereditary or acquired disorders resulting from an enzymatic deformity in biochemical and metabolic pathways influencing proteins, fats, carbohydrate metabolism, or hampered some organelle function. Even though individual IEMs are uncommon, together, they represent a diverse class of genetic diseases, with new issues and disease mechanisms being portrayed consistently. IEM includes the extraordinary multifaceted nature of the fundamental pathophysiology, biochemical diagnosis, molecular level investigation, and complex therapeutic choices. However, due to the molecular, biochemical, and clinical heterogeneity of IEM, screening alone will not detect and diagnose all illnesses included in newborn screening programs. Early diagnosis prevents the emergence of severe clinical symptoms in the majority of IEM cases, lowering morbidity and death. The appearance of IEM disease can vary from neonates to adult people, with the more serious conditions showing up in juvenile stages along with significant morbidity as well as mortality. Advances in understanding the physiological, biochemical, and molecular etiologies of numerous IEMs by means of modalities, for instance, the latest molecular-genetic technologies, genome engineering knowledge, entire exome sequencing, and metabolomics, have prompted remarkable advancement in detection and treatment in modern times. In this review, we analyze the biochemical basis of IEMs, clinical manifestations, the present status of screening, ongoing advances, and efficiency of diagnosis in treatment for IEMs, along with prospects for further exploration as well as innovation.

How to detect late-onset inborn errors of metabolism in patients with movement disorders - A modern diagnostic approach

We propose a modern approach to assist clinicians to recognize and diagnose inborn errors of metabolism (IEMs) in adolescents and adults that present with a movement disorder. IEMs presenting in adults are still largely unexplored. These disorders receive little attention in neurological training and daily practice, and are considered complicated by many neurologists. Adult-onset presentations of IEMs differ from childhood-onset phenotypes, which may lead to considerable diagnostic delay. The identification of adult-onset phenotypes at the earliest stage of the disease is important, since early treatment may prevent or lessen further brain damage. Our approach is based on a systematic review of all papers that concerned movement disorders due to an IEM in patients of 16 years or older. Detailed clinical phenotyping is the diagnostic cornerstone of the approach. An underlying IEM should be suspected in particular in patients with more than one movement disorder, or in patients with additional neurological, psychiatric, or systemic manifestations. As IEMs are all genetic disorders, we recommend next-generation sequencing (NGS) as the first diagnostic approach to confirm an IEM. Biochemical tests remain the first choice in acute-onset or treatable IEMs that require rapid diagnosis, or to confirm the metabolic diagnosis after NGS results. With the use of careful and systematic clinical phenotyping combined with novel diagnostic approaches such as NGS, the diagnostic yield of late-onset IEMs will increase, in particular in patients with mild or unusual phenotypes.

Distinctive diffusion-weighted imaging features in late-onset genetic leukoencephalopathies

Genetic leukoencephalopathies are inherited disorders characterized by progressive white matter involvement. Although most are paediatric conditions, late-onset adult leukoencephalopathies are being increasingly recognized. Adult leukoencephalopathies may present as neurodegenerative diseases with cognitive decline and motor symptoms. Similar to their paediatric counterparts, different adult leukoencephalopathies often have distinctive MRI appearances. In particular, DWI has been recently shown to demonstrate specific patterns of persistent diffusion restriction in several adult-onset leukoencephalopathies. As such, DWI may provide important clues to the diagnosis of adult-onset leukoencephalopathy. The purpose of this review is to discuss characteristic DWI features in some late-onset leukoencephalopathies.

Seizures and early onset dementia: D2HGA1 inborn error of metabolism in adults

D‐2‐hydroxyglutaric aciduria type 1 (D2HGA1) is a rare inherited metabolic disorder usually manifesting in infancy/early childhood with seizures and significant central nervous system involvement. We report two siblings with D2HGA1 presenting with mild intellectual disability, and the onset of seizures in adulthood. One of them was misdiagnosed as tuberous sclerosis due to her presentation and the presence of subependymal nodules on brain imaging. Both further developed early onset dementia. This report expands the phenotype of D2HGA1 to include late‐onset seizures and early onset dementia in adults.

Sensitivity to myelin using model-free analysis of the water resonance line-shape in postmortem mouse brain

PURPOSE

Dysmyelinating diseases are characterized by abnormal myelin formation and function. Such microstructural abnormalities in myelin have been demonstrated to produce measurable effects on the MR signal. This work examines these effects on measurements of voxel-wise, high-resolution water spectra acquired using a 3D echo-planar spectroscopic imaging (EPSI) pulse sequence from both postmortem fixed control mouse brains and a dysmyelination mouse brain model.

METHODS

Perfusion fixed, resected control (n = 5) and shiverer (n = 4) mouse brains were imaged using 3D-EPSI with 100 µm isotropic resolution. The free induction decay (FID) was sampled every 2.74 ms over 192 echoes, for a total sampling duration of 526.08 ms. Voxel-wise FIDs were Fourier transformed to produce water spectra with 1.9 Hz resolution. Spectral asymmetry was computed and compared between the two tissue types.

RESULTS

The water resonance is more asymmetrically broadened in the white matter of control mouse brain compared with dysmyelinated white matter. In control brain, this is modulated by and consistent with previously reported orientationally dependent effects of white matter relative to B₀ . Similar sensitivity to orientation is observed in dysmyelinated white matter as well; however, the magnitude of the resonance asymmetry is much lower across all directions.

CONCLUSION

Results demonstrate that components of the spectra are specifically differentially affected by myelin concentration. This suggests that water proton spectra may be sensitive to the presence of myelin, and as such, could serve as a MRI-based biomarker of dysmyelinating disease, free of mathematical models.

[Multifocal brain lesions]

Despite the current laboratory and instrumental approaches to the diagnosis, a patient with multiple brain lesions remains a difficult one. The reason is that these lesions can be caused by a variety of disorders, including rare ones and atypical forms. Distinguishing neoplastic lesions from non-neoplastic CNS disorders is crucial due to different treatment options. The authors report the case of a patient with multiple brain lesions, present a literature review of diseases to be differentially diagnosed with multifocal brain lesions and suggest a simple algorithm for the differential diagnosis. Timely clinical evaluation and a multidisciplinary approach are required for making a definitive diagnosis that is extremely important to start the appropriate therapy.

Artificial Intelligence System Approaching Neuroradiologist-level Differential Diagnosis Accuracy at Brain MRI

Background Although artificial intelligence (AI) shows promise across many aspects of radiology, the use of AI to create differential diagnoses for rare and common diseases at brain MRI has not been demonstrated. Purpose To evaluate an AI system for generation of differential diagnoses at brain MRI compared with radiologists. Materials and Methods This retrospective study tested performance of an AI system for probabilistic diagnosis in patients with 19 common and rare diagnoses at brain MRI acquired between January 2008 and January 2018. The AI system combines data-driven and domain-expertise methodologies, including deep learning and Bayesian networks. First, lesions were detected by using deep learning. Then, 18 quantitative imaging features were extracted by using atlas-based coregistration and segmentation. Third, these image features were combined with five clinical features by using Bayesian inference to develop probability-ranked differential diagnoses. Quantitative feature extraction algorithms and conditional probabilities were fine-tuned on a training set of 86 patients (mean age, 49 years ± 16 [standard deviation]; 53 women). Accuracy was compared with radiology residents, general radiologists, neuroradiology fellows, and academic neuroradiologists by using accuracy of top one, top two, and top three differential diagnoses in 92 independent test set patients (mean age, 47 years ± 18; 52 women). Results For accuracy of top three differential diagnoses, the AI system (91% correct) performed similarly to academic neuroradiologists (86% correct; P = .20), and better than radiology residents (56%; P < .001), general radiologists (57%; P < .001), and neuroradiology fellows (77%; P = .003). The performance of the AI system was not affected by disease prevalence (93% accuracy for common vs 85% for rare diseases; P = .26). Radiologists were more accurate at diagnosing common versus rare diagnoses (78% vs 47% across all radiologists; P < .001). Conclusion An artificial intelligence system for brain MRI approached overall top one, top two, and top three differential diagnoses accuracy of neuroradiologists and exceeded that of less-specialized radiologists. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Zaharchuk in this issue.