Steffi Dreha-Kulaczewski

Folate receptor alpha defect causes cerebral folate transport deficiency: a treatable neurodegenerative disorder associated with disturbed myelin metabolism.

Sufficient folate supplementation is essential for a multitude of biological processes and diverse organ systems. At least five distinct inherited disorders of folate transport and metabolism are presently known, all of which cause systemic folate deficiency. We identified an inherited brain-specific folate transport defect that is caused by mutations in the folate receptor 1 (FOLR1) gene coding for folate receptor alpha (FRalpha). Three patients carrying FOLR1 mutations developed progressive movement disturbance, psychomotor decline, and epilepsy and showed severely reduced folate concentrations in the cerebrospinal fluid (CSF). Brain magnetic resonance imaging (MRI) demonstrated profound hypomyelination, and MR-based in vivo metabolite analysis indicated a combined depletion of white-matter choline and inositol. Retroviral transfection of patient cells with either FRalpha or FRbeta could rescue folate binding. Furthermore, CSF folate concentrations, as well as glial choline and inositol depletion, were restored by folinic acid therapy and preceded clinical improvements. Our studies not only characterize a previously unknown and treatable disorder of early childhood, but also provide new insights into the folate metabolic pathways involved in postnatal myelination and brain development.

Inspiration is the major regulator of human CSF flow.

The mechanisms behind CSF flow in humans are still not fully known. CSF circulates from its primary production sites at the choroid plexus through the brain ventricles to reach the outer surface of the brain in the subarachnoid spaces from where it drains into venous bloodstream and cervical lymphatics. According to a recent concept of brain fluid transport, established in rodents, CSF from the brain surface also enters the brain tissue along para-arterial routes and exits through paravenous spaces again into subarachnoid compartments. This unidirectional flow is mainly driven by arterial pulsation. To investigate how CSF flow is regulated in humans, we applied a novel real-time magnetic resonance imaging technique at high spatial (0.75 mm) and temporal (50 ms) resolution in healthy human subjects. We observed significant CSF flow exclusively with inspiration. In particular, during forced breathing, high CSF flow was elicited during every inspiration, whereas breath holding suppressed it. Only a minor flow component could be ascribed to cardiac pulsation. The present results unambiguously identify inspiration as the most important driving force for CSF flow in humans. Inspiratory thoracic pressure reduction is expected to directly modulate the hydrostatic pressure conditions for the low-resistance paravenous, venous, and lymphatic clearance routes of CSF. Furthermore, the experimental approach opens new clinical opportunities to study the pathophysiology of various forms of hydrocephalus and to design therapeutic strategies in relation to CSF flow alterations.

Cerebral involvement in axonal Charcot-Marie-Tooth neuropathy caused by mitofusin2 mutations.

Mutations in the mitofusin 2 (MFN2) gene are a major cause of primary axonal Charcot- Marie-Tooth (CMT) neuropathy. This study aims at further characterization of cerebral white matter alterations observed in patients with MFN2 mutations. Molecular genetic, magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and diffusion tensor imaging (DTI) investigations were performed in four unrelated patients aged 7 to 38 years with early onset axonal CMT neuropathy. Three distinct and so far undescribed MFN2 mutations were detected. Two patients had secondary macrocephaly and mild diffuse predominantly periventricular white matter alterations on MRI. In addition, one boy had symmetrical T2-hyperintensities in both thalami. Two patients had optic atrophy, one of them with normal MRI. In three patients proton MRS revealed elevated concentrations of total N-acetyl compounds (neuronal marker), total creatine (found in all cells) and myo-inositol (astrocytic marker) in cerebral white and gray matter though with regional variation. These alterations were most pronounced in the two patients with abnormal MRI. DTI of these patients revealed mild reductions of fractional anisotropy and mild increase of mean diffusivity in white matter. The present findings indicate an enhanced cellular density in cerebral white matter of MFN2 neuropathy which is primarily due to a reactive gliosis without axonal damage and possibly accompanied by mild demyelination.

Pediatric onset multiple sclerosis: McDonald criteria 2010 and the contribution of spinal cord MRI:

Background: Diagnostic magnetic resonance imaging (MRI) criteria have not been sufficiently validated in pediatric multiple sclerosis (MS) despite differences in epidemiologic data and clinical disease courses between pediatric and adult MS. Objective: The objective of this paper is to evaluate the diagnostic applicability and validity of the revised McDonald diagnostic criteria 2010 in a large cohort of pediatric-onset MS patients (POMS) and compare them to previously recommended MRI-based classifications. Furthermore, we aimed to investigate the contribution of spinal cord lesions to the revised McDonald criteria 2010. Methods: A cohort of 85 patients with definite MS, age at onset 2.8–18 years, was analyzed in a retrospective multicenter study. Number and regional distribution of T2w and contrast-enhancing T1w lesions at initial and follow-up MRIs were main outcome measures. Results: In 62% of POMS the initial MRI within four weeks after symptom onset was sufficient to diagnose MS according to the revised McDonald criteria 2010. In a subcohort of patients with spinal MRI at first presentation, 10% reached the dissemination in space (DIS) and dissemination in time (DIT) criteria only by the inclusion of contrast-enhancing spinal lesions. Conclusions: The revised McDonald criteria 2010 facilitate the diagnosis of POMS already at first presentation. The addition of a spinal cord MRI was helpful only in selected cases.

Identification of the upward movement of human CSF in vivo and its relation to the brain venous system.

CSF flux is involved in the pathophysiology of neurodegenerative diseases and cognitive impairment after traumatic brain injury, all hallmarked by the accumulation of cellular metabolic waste. Its effective disposal via various CSF routes has been demonstrated in animal models. In contrast, the CSF dynamics in humans are still poorly understood. Using novel real-time MRI, forced inspiration has been identified recently as a main driving force of CSF flow in the human brain. Exploiting technical advances toward real-time phase-contrast MRI, the current work analyzed directions, velocities, and volumes of human CSF flow within the brain aqueduct as part of the internal ventricular system and in the spinal canal during respiratory cycles. A consistent upward CSF movement toward the brain in response to forced inspiration was seen in all subjects at the aqueduct, in 11/12 subjects at thoracic level 2, and in 4/12 subjects at thoracic level 5. Concomitant analyses of CSF dynamics and cerebral venous blood flow, that is, in epidural veins at cervical level 3, uniquely demonstrated CSF and venous flow to be closely communicating cerebral fluid systems in which inspiration-induced downward flow of venous blood due to reduced intrathoracic pressure is counterbalanced by an upward movement of CSF. The results extend our understanding of human CSF flux and open important clinical implications, including concepts for drug delivery and new classifications and therapeutic options for various forms of hydrocephalus and idiopathic intracranial hypertension. SIGNIFICANCE STATEMENT Effective disposal of brain cellular waste products via CSF has been demonstrated repeatedly in animal models. However, CSF dynamics in humans are still poorly understood. A novel quantitative real-time MRI technique yielded in vivo CSF flow directions, velocities, and volumes in the human brain and upper spinal canal. CSF moved upward toward the head in response to forced inspiration. Concomitant analysis of brain venous blood flow indicated that CSF and venous flux act as closely communicating systems. The finding of a human CSF–venous network with upward CSF net movement opens new clinical concepts for drug delivery and new classifications and therapeutic options for various forms of hydrocephalus and ideopathic intracranial hypertension.

Assessment of myelination in hypomyelinating disorders by quantitative MRI.

To apply myelin‐sensitive quantitative magnetic resonance imaging (MRI) techniques in defined hypomyelinating conditions and to identify spatial patterns of myelination as criteria for characterization of undefined disorders.

Early Reduction of Total N-Acetyl-Aspartate-Compounds in Patients With Classical Vanishing White Matter Disease. A Long-Term Follow-Up MRS Study

The neuropathology of vanishing white matter (VWM) disease is characterized by a loss of white matter (WM). Although recent histopathological studies suggest a primary glial dysfunction, the purpose of this work was to assess the extent of axonal involvement in VWM using long-term follow-up proton MR spectroscopy. White and gray matter of nine children with genetically proven VWM and late infancy/early childhood onset were investigated with short-echo time, single-voxel proton MR spectroscopy over up to 8 years starting as early as less than 2 years after the onset of symptoms (5 patients). Total N-acetyl-aspartate (−51% from normal control), creatine and phosphocreatine (−47%), and myo-inositol (−49%) were reduced in WM at early disease stages. Choline-containing compounds were less severely decreased (−31%). Follow-up investigations revealed progressive reduction of all metabolites in WM. In gray matter, no distinct changes were detected at early stages. Later total N-acetyl-aspartate decreased slightly (−22%). Assuming the metabolite alterations to primarily reflect changes in cellular composition, the observed pattern indicates early axonal involvement or loss as well as relatively enhanced turnover of myelin. These early stages are followed by a complete cellular loss in cerebral WM.

In vivo proton MR spectroscopy findings specific for adenylosuccinate lyase deficiency.

Adenylosuccinate lyase (ADSL) deficiency is an inherited metabolic disorder affecting predominantly the central nervous system. The disease is characterized by the accumulation of succinylaminoimidazolecarboxamide riboside and succinyladenosine (S‐Ado) in tissue and body fluids. Three children presented with muscular hypotonia, psychomotor delay, behavioral abnormalities, and white matter changes on brain MRI. Two of them were affected by seizures. Screening for inborn errors of metabolism including in vitro high resolution proton MRS revealed an ADSL deficiency that was confirmed genetically in all cases. All patients were studied by in vivo proton MRS. In vitro high resolution proton MRS of patient cerebrospinal fluid showed singlet resonances at 8.27 and 8.29 ppm that correspond to accumulated S‐Ado. In vivo proton MRS measurements also revealed a prominent signal at 8.3 ppm in gray and white matter brain regions of all patients. The resonance was undetectable in healthy human brain. In vivo proton MRS provides a conclusive finding in ADSL deficiency and represents a reliable noninvasive diagnostic tool for this neurometabolic disorder. Copyright

A Novel SLC6A8 Mutation in a Large Family with X-Linked Intellectual Disability: Clinical and Proton Magnetic Resonance Spectroscopy Data of Both Hemizygous Males and Heterozygous Females

X-linked creatine transport (CRTR) deficiency, caused by mutations in the SLC6A8 gene, leads to intellectual disability, speech delay, epilepsy, and autistic behavior in hemizygous males. Additional diagnostic features are depleted brain creatine levels and increased creatine/creatinine ratio (cr/crn) in urine. In heterozygous females the phenotype is highly variable and diagnostic hallmarks might be inconclusive. This survey aims to explore the intrafamilial variability of clinical and brain proton Magnetic Resonance Spectroscopy (MRS) findings in males and females with CRTR deficiency. X-chromosome exome sequencing identified a novel missense mutation in the SLC6A8 gene (p.G351R) in a large family with X-linked intellectual disability. Detailed clinical investigations including neuropsychological assessment, measurement of in vivo brain creatine concentrations using quantitative MRS, and analyses of creatine metabolites in urine were performed in five clinically affected family members including three heterozygous females and one hemizygous male confirming the diagnosis of CRTR deficiency. The severe phenotype of the hemizygous male was accompanied by most distinct aberrations of brain creatine concentrations (-83% in gray and -79% in white matter of age-matched normal controls) and urinary creatine/creatinine ratio. In contrast, the heterozygous females showed varying albeit generally milder phenotypes with less severe brain creatine (-50% to -33% in gray and -45% to none in white matter) and biochemical urine abnormalities. An intrafamilial correlation between female phenotype, brain creatine depletion, and urinary creatine abnormalities was observed. The combination of powerful new technologies like exome-next-generation sequencing with thorough systematic evaluation of patients will further expand the clinical spectrum of neurometabolic diseases.

Unilateral dilation of virchow-robin spaces in early childhood.

Observations of extreme unilateral widening of Virchow-Robin spaces (VRS) are rare and hitherto confined to adult, mainly old-aged patients. Magnetic resonance imaging (MRI) was performed in two unrelated boys aged 3 years with developmental coordination disorders. In one of these patients, follow-up MRI and diffusion tensor imaging (DTI) were carried out 5 years later. In both boys, MRI incidentally revealed numerous intracerebral cysts strictly confined to one hemisphere. Localization, size, shape, and signal isointensity to cerebrospinal fluid indicated unilateral marked widening of VRS. In one patient, follow-up investigation after 5 years showed unchanged dilation of VRS on MRI, but mild facial hemihypertrophy, ipsilateral to the widened VRS. DTI indicated displacement rather than disruption of fiber tracks adjacent to the dilated VRS. Unilateral widening of VRS may be detected fortuitously on neuroimaging already in early childhood.