OBJECTIVES:SLC4A4 encodes electrogenic sodium bicarbonate cotransporter NBCe1, prominently expressed in kidney and brain. Recessive loss-of-function variants in SLC4A4 cause proximal renal tubular acidosis, no brain edema. In the brain, NBCe1 is expressed by astrocytes, where it regulates pH and mediates astrocyte volume changes. Here we describe a novel dominant variant in SLC4A4 in patients with brain edema and investigate how it affects NBCe1 function. METHODS:Genetic studies identified a novel gene variant in three unrelated pediatric patients with the same MRI pattern of cerebral subcortical white matter signal abnormality and swelling, and medulla lesions. Immunohistochemical and electrophysiological experiments were performed to determine the localization of the transporter in the brain and the functional consequence of the patient variant. RESULTS:The same heterozygous variant in SLC4A4 was found in all three patients and one parent. The children displayed infantile-onset progressive macrocephaly, motor and cognitive impairment, autism, epilepsy, and recurrent episodes of increased intracranial pressure. Bicarbonate treatment of two patients led to clinical and MRI improvement. Immunohistochemistry revealed that brain NBCe1 is mainly present in astrocytes, more in cortex than white matter. Functional experiments revealed impaired transporter activity of mutant NBCe1 due to reduced membrane expression and a prominent depolarizing ion leak. INTERPRETATION:The most likely pathomechanism of this novel SLC4A4-related disease is that a depolarizing leak in NBCe1 disrupts astrocyte pH regulation, promoting swelling and impairing volume control. These findings uncover a previously unrecognized mechanism of genetic brain edema and establish NBCe1 as a critical modulator of astrocyte homeostasis.

Globoid cell leukodystrophy (GLD) is a progressive neurodegenerative disease caused by galactocerebrosidase deficiency. Juvenile phenotypes—onset between ages 3 and 16—account for up to 25

BACKGROUND AND OBJECTIVES:Cerebral adrenoleukodystrophy (CALD) is a common manifestation of adrenoleukodystrophy (ALD) in men. Early detection of CALD lesions through MRI screening is critical to allow for therapeutic action preventing severe disability and death. While the frequency of brain MRI monitoring has been addressed by international recommendations, no consensus currently exists regarding which MRI sequences should be used in a real-world setting for screening and follow-up of CALD lesions. The aim of this study was to establish guidelines for the MRI protocol in clinical practice and to identify priority sequences for research use, thereby promoting intercenter harmonization. METHODS:A modified Delphi procedure was used to achieve consensus on MRI protocols for ALD screening, lesion monitoring, and research applications among experts with experience in brain imaging in ALD. Questionnaires allowed experts to indicate whether they considered sequences as core, optional, or research, or to express agreement (5-point scale ranging from completely disagree to completely agree) with specific statements. Topics where no agreement was reached were discussed during online consensus meetings. RESULTS:Thirty experts from 9 countries participated and agreed that the core screening protocol for ALD in adults and children should include at least 3D T1-weighted, spin-echo T2-weighted, 3D fluid-attenuated inversion recovery, and diffusion-weighted imaging (DWI). Postcontrast T1-weighted imaging should be performed systematically in specific clinical scenarios. Experts supported using DWI alongside the Loes score and postcontrast imaging to assess lesion progression. A research protocol was defined, prioritizing diffusion tensor imaging, MR perfusion, and quantitative volumetric analyses. DISCUSSION:This international project harmonizes the ALD MRI protocol, thus offering a practical framework to screen and monitor lesions, which will improve clinical decision making. It also identifies MRI sequences that should be prioritized in future research. Future research on MRI in ALD should focus on topics where no consensus has yet been reached in this project.

Background and ObjectivesCerebral adrenoleukodystrophy (CALD) is a common manifestation of adrenoleukodystrophy (ALD) in men. Early detection of CALD lesions through MRI screening is critical to allow for therapeutic action preventing severe disability and death. While the frequency of brain MRI monitoring has been addressed by international recommendations, no consensus currently exists regarding which MRI sequences should be used in a real-world setting for screening and follow-up of CALD lesions. The aim of this study was to establish guidelines for the MRI protocol in clinical practice and to identify priority sequences for research use, thereby promoting intercenter harmonization.MethodsA modified Delphi procedure was used to achieve consensus on MRI protocols for ALD screening, lesion monitoring, and research applications among experts with experience in brain imaging in ALD. Questionnaires allowed experts to indicate whether they considered sequences as core, optional, or research, or to express agreement (5-point scale ranging from completely disagree to completely agree) with specific statements. Topics where no agreement was reached were discussed during online consensus meetings.ResultsThirty experts from 9 countries participated and agreed that the core screening protocol for ALD in adults and children should include at least 3D T1-weighted, spin-echo T2-weighted, 3D fluid-attenuated inversion recovery, and diffusion-weighted imaging (DWI). Postcontrast T1-weighted imaging should be performed systematically in specific clinical scenarios. Experts supported using DWI alongside the Loes score and postcontrast imaging to assess lesion progression. A research protocol was defined, prioritizing diffusion tensor imaging, MR perfusion, and quantitative volumetric analyses.DiscussionThis international project harmonizes the ALD MRI protocol, thus offering a practical framework to screen and monitor lesions, which will improve clinical decision making. It also identifies MRI sequences that should be prioritized in future research. Future research on MRI in ALD should focus on topics where no consensus has yet been reached in this project.

Genetic pain loss disorders represent a heterogeneous group of rare diseases mainly characterized by defective nociception. Understanding the underlying molecular mechanism is fundamental to improve the treatment of patients affected by these rare disorders. Feline Leukemia Virus Subgroup C Receptor 1 (FLVCR1) is one of the genes previously associated with sensory neuropathy that requires further investigation. Here, we report on two additional patients with novel disease-causing variants in FLVCR1 and introduce a zebrafish model of the disease. The analyses of patient-derived fibroblasts show that distinct FLVCR1 variants compromised all the known functions associated with FLVCR1, thus affecting choline levels, heme biosynthesis and mitochondrial Ca2+ handling. Furthermore, we provide evidence that the alteration of these processes impairs the TCA cycle and OXPHOS, and induces lipid peroxidation. Our data points to the alterations of energetic metabolism as a potential driving pathomechanism in FLVCR1-associated sensory neuropathy.

BACKGROUND:Adult adrenoleukodystrophy is a rare X linked disorder with heterogeneous phenotypes, complicating prognosis and trial design. We characterised phenotype and natural history in a large single-centre nationwide cohort and contextualised findings with prior reports. METHODS:We performed a combined retrospective-prospective observational study of adults (≥18 years) with confirmed ABCD1 variants evaluated at Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan (January 2004-June 2023), with reassessments between July and December 2023. Clinical, genetic, biochemical, MRI and neurophysiological data were analysed. RESULTS:The cohort comprised 140 patients (64 males, 76 females) from 58 families, carrying 50 ABCD1 variants, including 11 novel mutations. Adrenomyeloneuropathy (AMN) predominated in males, with low mortality (<10%) and rare cerebral progression (7%) across 18 years, suggesting protective factors. An intermediate phenotype, adrenoleukomyeloneuropathy (ALMN), showed earlier onset, demyelinating MRI changes without cerebral symptoms at baseline and higher mortality than AMN (HR 4.75, 95% CI 1.60 to 14.11). In females, symptom prevalence increases with age, affecting 57% over 60, although only 37% required walking aids. Males had higher very long-chain fatty acid (VLCFA) levels than females, but intrasex correlations with phenotype were absent. Brainstem auditory evoked potentials (BAEPs) were consistently abnormal, whereas nerve conduction studies were abnormal in ~half of male patients (less often in females). CONCLUSIONS:Adult adrenoleukodystrophy comprises distinct phenotypes with variable prognosis. Recognition of ALMN as an intermediate form and the low cerebral progression rate in Italian AMN refine disease classification. Sex-related VLCFA differences may influence severity, although standard assays lack sensitivity. Neurophysiological testing, particularly BAEPs, can support differential diagnosis in patients with hereditary spastic paraplegias. TRIAL REGISTRATION NUMBER:NCT04880356.

OBJECTIVES:The gold standard for distinguishing epileptic seizures (ES) from non-epileptic events is video-EEG monitoring. In some cases, video alone might suffice, leading to increased utilization of home videos, to support the diagnosis. This study aimed to assess the feasibility of such practice and its accuracy compared to video-EEG, to identify key signs and symptoms of functional seizure (FS) and to establish if self-reported questionnaires would improve diagnostic accuracy. METHODS:All consecutive patients ≥14 years presenting to six Italian epilepsy centers with either recurrent paroxysmal events of uncertain nature or with confirmed ES were enrolled. Subjects had to record home videos of the events and to respond to ad-hoc questionnaires. De-identified data were randomly assigned to pairs of evaluators blinded to the gold standard diagnosis, one epileptologist and one neurologist, to predict the correct diagnosis in two steps: Step 1 (home video alone) and Step 2 (patient's and witness' questionnaires). RESULTS:Ninety-four videos (48 ES; 45 FS; 1 other), obtained from 36 patients, were independently evaluated by the 16 reviewers, providing a total of 188 assessments. Diagnostic accuracy for the whole group was 55.3% among epileptologists and 48.9% among neurologists (p = 0.6892) but was significantly higher in the FS subgroup (71.1%) compared to ES (41.7%) (p = 0.0043). SIGNIFICANCE:Diagnostic accuracy was moderate, without significant differences between epileptologists and neurologists, while it was higher for FS compared to ES. The addition of questionnaires did not improve accuracy. Eye closure for FS and abrupt ending for ES emerged as the only diagnostic signs. Thus, homemade videos have a role in differentiating these disorders. PLAIN LANGUAGE SUMMARY:This study aimed to assess if home videos can distinguish epileptic seizures from functional seizures. Patients over 14 years from six Italian centers recorded videos of their episodes and answered questionnaires. Data were evaluated by epileptologists and neurologists. Results showed moderate diagnostic accuracy, with higher accuracy for functional seizures compared to epileptic seizures. Key diagnostic signs included eye closure for functional seizures and abrupt endings for epileptic seizures. Questionnaires did not improve accuracy. In conclusion, home videos can help differentiate these events.

BACKGROUND:Mitochondrial aminoacyl tRNA synthetase (mt-ARS) related disorders represent a widely heterogeneous group of diseases affecting the efficiency of mitochondrial protein synthesis. AARS2 and DARS2 biallelic mutations are associated with clinical syndromes prominently characterized by diffuse leukoencephalopathy with a highly variable age of onset, ranging from early infancy to adulthood. Preliminary in vitro results on patients' fibroblasts and some anecdotal reports on patients affected by mt-ARS related disease have suggested a possible benefit of supplementation with the specific substrate amino acid of the defective mt-ARS. METHODS:We recruited 6 adult patients affected by AARS2 (n = 2) and DARS2 (n = 4) related leukoencephalopathies and started an oral supplementation with alanine and aspartate, respectively, for a total duration of 2 years. Therapeutic efficacy and safety were assessed through clinical examinations, standardized scales, functional tests, quality of life (QoL) scores, brain MRI, and laboratory analyses. RESULTS:Overall, the treatment was safe and well tolerated by all patients, but efficacy endpoints were not met as no significant improvements were observed in global, cognitive, or motor scores.; nonetheless, all patients but one remained clinically stable. CONCLUSIONS:Despite inherent limitations of this pivotal trial, our findings suggest that specific amino acid supplementation is a safe intervention but do not yield a clear symptomatic benefit; nevertheless, we cannot exclude a potential role in stabilizing the clinical condition in adult patients with DARS2-related disorders.

Vanishing white matter (VWM) is a rare disorder, characterized by degeneration of CNS white matter, clinically often exacerbated by stressors such as fever and minor head trauma. VWM is caused by biallelic pathogenic variants in the EIF2B1-5 genes, causing reduced activity of eukaryotic initiation of translation factor 2B, resulting in dysregulation of the integrated stress response (ISR). New scientific insights and increased clinical trials in experimental therapies highlight the need for clinical guidelines to improve and standardize care for patients with VWM worldwide. Standardized care is important for therapy development, as it lessens clinical variability of trial participants at study entry, enabling more sensitive evaluation of treatment outcomes. The aim of this study was to develop expert consensus-based recommendations for diagnosis and management of VWM. A real-time Delphi process with a multidisciplinary expert panel was conducted to formulate consensus-based recommendations. A literature review was performed to determine the strength of available evidence supporting each recommendation. The consensus yielded 43 recommendations on diagnosis, including genetic and MRI criteria, and on clinical management concerning disease progression, acute and long-term care, and preventive strategies. All known pathogenic and likely pathogenic EIF2B1-5 variants were identified from the literature and Amsterdam Leukodystrophy Center laboratory. An overview of these EIF2B1-5 variants was composed to facilitate diagnosis. Clinically used drugs may activate the ISR, posing a risk in VWM, or have no effect on or suppress the ISR, being probably safe in VWM. A second literature search explored the effects of clinically frequently used drugs on the ISR. Drugs were categorized into those likely to activate the ISR, suppress it, and have no likely effects on the ISR. Final judgment was achieved in a consensus meeting of experts. A patient management card was developed with input from clinical experts and patient advocates to provide information on these consensus-based recommendations in lay language and bridge the gap between scientific evidence and expert opinion on one side and the practical needs of clinicians and families on the other side. This study contributes to improving and standardizing VWM care based on scientific and expert insights, while highlighting key areas for future research.

BACKGROUND:Adult-onset neurogenetic diseases (NGDs) with white matter abnormalities are rare and often misdiagnosed as Multiple Sclerosis (MS) due to overlapping clinical and radiological features. Misdiagnosis can lead to unnecessary immunosuppressive treatments and delayed genetic counseling. This study combines a retrospective multicenter analysis with a systematic review of the literature to assess the characteristics of patients with NGDs misdiagnosed as MS (Mis-MS) or with coexisting MS (NGD-MS), with the goal of improving diagnostic accuracy. METHODS:The retrospective study was conducted across seven tertiary MS centers in Europe and North America. Patients with confirmed NGDs initially misdiagnosed as MS or with coexisting MS were included. Clinical, radiological, and genetic data were analyzed. Brain MRIs were evaluated for MS-consistent and atypical features using standardized criteria. A systematic literature review of NGDs mimicking MS was also performed. RESULTS:The retrospective study included 46 patients (37 Mis-MS, 9 NGD-MS). Common NGDs in Mis-MS were Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) (22 %), Adult-onset Leukoencephalopathy with Axonal Spheroids and Pigmented Glia (ALSP) (8 %), and Adult-onset Alexander Disease (AOAD) (5 %). NGD-MS cases were primarily mitochondrial disorders (67 %). The median diagnostic delay for NGDs was nine years. Despite 80 % of Mis-MS patients showing atypical MRI features, 41 % met MS dissemination in space and 20 % dissemination in time criteria. CSF oligoclonal bands were absent in 92 % of Mis-MS patients but present in 83 % of NGD-MS patients. Literature review identified 81 Mis- MS and 22 NGD-MS cases, with Fabry disease and CADASIL most frequently involved. DISCUSSION:Diagnosing NGDs that mimic MS is challenging. CADASIL, ALSP, and AOAD were the most commonly misdiagnosed neurogenetic diseases as MS. Vasculopathies like CADASIL are challenging to differentiate from MS due to similar clinical and imaging features, including remitting course and gadolinium enhancement. Recognizing atypical MRI patterns and integrating clinical and genetic evaluations can improve diagnostic accuracy and patient care by preventing unnecessary MS treatment and enabling timely genetic counseling.

A 40-year-old man with adult-onset spastic-ataxia and tremor showed a leukoencephalopathy with a hypomyelinating pattern on brain MRI. Whole-exome sequencing identified two novel likely pathogenic variants in KIF1C, a gene associated with spastic-ataxia type 2 (SPAX2). This case supports including KIF1C among the causes of adult-onset hypomyelinating leukodystrophies and highlights the diagnostic overlap between spastic-ataxia, hereditary spastic paraplegia, and hypomyelinating leukodystrophies, underscoring the limitations of current nomenclature.

Alexander disease (ALXDRD) is a rare neurodegenerative disorder of astrocytes resulting from pathogenic variants in the GFAP gene. The genotype-phenotype correlation remains elusive due to the variable expressivity of clinical manifestations. In an attempt to clarify the effects of GFAP variants in ALXDRD, numerous studies were collected and analyzed. In particular, we systematically searched for GFAP variants associated with ALXDRD and collected information on the location within the gene and protein, prediction of deleteriousness/pathogenicity, occurrence, sex and country of origin of patients, DNA source, genetic testing, and clinical signs. To identify possible associations, statistical analyses and meta-analyses were applied, thus revealing a higher than expected percentage of adult patients with ALXDRD. Furthermore, substitution of Arginine, the most frequently altered residue among the 550 predominantly missense causative GFAP variants collected, were mostly de novo and more prevalent in early-onset forms of ALXDRD. The effect of defective splicing in modifying the impact of GFAP variants on the age of onset of ALXDRD was also postulated after evaluating the distribution of the corresponding deleterious predictive values. In conclusion, not only previously unrecognized genotype-phenotype correlations were revealed in ALXDRD, but also subtle mechanisms could explain the variable manifestations of the ALXDRD clinical phenotype.