Bi-allelic JAM2 Variants Lead to Early-Onset Recessive Primary Familial Brain Calcification.

Primary familial brain calcification (PFBC) is a rare neurodegenerative disorder characterized by a combination of neurological, psychiatric, and cognitive decline associated with calcium deposition on brain imaging. To date, mutations in five genes have been linked to PFBC. However, more than 50% of individuals affected by PFBC have no molecular diagnosis. We report four unrelated families presenting with initial learning difficulties and seizures and later psychiatric symptoms, cerebellar ataxia, extrapyramidal signs, and extensive calcifications on brain imaging. Through a combination of homozygosity mapping and exome sequencing, we mapped this phenotype to chromosome 21q21.3 and identified bi-allelic variants in JAM2. JAM2 encodes for the junctional-adhesion-molecule-2, a key tight-junction protein in blood-brain-barrier permeability. We show that JAM2 variants lead to reduction of JAM2 mRNA expression and absence of JAM2 protein in patient's fibroblasts, consistent with a loss-of-function mechanism. We show that the human phenotype is replicated in the jam2 complete knockout mouse (jam2 KO). Furthermore, neuropathology of jam2 KO mouse showed prominent vacuolation in the cerebral cortex, thalamus, and cerebellum and particularly widespread vacuolation in the midbrain with reactive astrogliosis and neuronal density reduction. The regions of the human brain affected on neuroimaging are similar to the affected brain areas in the myorg PFBC null mouse. Along with JAM3 and OCLN, JAM2 is the third tight-junction gene in which bi-allelic variants are associated with brain calcification, suggesting that defective cell-to-cell adhesion and dysfunction of the movement of solutes through the paracellular spaces in the neurovascular unit is a key mechanism in CNS calcification

Genetic and phenotypic characterization of NKX6‐2‐related spastic ataxia and hypomyelination

Background and purpose Hypomyelinating leukodystrophies are a heterogeneous group of genetic disorders with a wide spectrum of phenotypes and a high rate of genetically unsolved cases. Bi‐allelic mutations in NKX6‐2 were recently linked to spastic ataxia 8 with hypomyelinating leukodystrophy. Methods Using a combination of homozygosity mapping, exome sequencing, and detailed clinical and neuroimaging assessment a series of new NKX6‐2 mutations in a multicentre setting is described. Then, all reported NKX6‐2 mutations and those identified in this study were combined and an in‐depth analysis of NKX6‐2‐related disease spectrum was provided. Results Eleven new cases from eight families of different ethnic backgrounds carrying compound heterozygous and homozygous pathogenic variants in NKX6‐2 were identified, evidencing a high NKX6‐2 mutation burden in the hypomyelinating leukodystrophy disease spectrum. Our data reveal a phenotype spectrum with neonatal onset, global psychomotor delay and worse prognosis at the severe end and a childhood onset with mainly motor phenotype at the milder end. The phenotypic and neuroimaging expression in NKX6‐2 is described and it is shown that phenotypes with epilepsy in the absence of overt hypomyelination and diffuse hypomyelination without seizures can occur. Conclusions NKX6‐2 mutations should be considered in patients with autosomal recessive, very early onset of nystagmus, cerebellar ataxia with hypotonia that rapidly progresses to spasticity, particularly when associated with neuroimaging signs of hypomyelination. Therefore, it is recommended that NXK6‐2 should be included in hypomyelinating leukodystrophy and spastic ataxia diagnostic panels

Biallelic mutations in neurofascin cause neurodevelopmental impairment and peripheral demyelination.

Axon pathfinding and synapse formation are essential processes for nervous system development and function. The assembly of myelinated fibres and nodes of Ranvier is mediated by a number of cell adhesion molecules of the immunoglobulin superfamily including neurofascin, encoded by the NFASC gene, and its alternative isoforms Nfasc186 and Nfasc140 (located in the axonal membrane at the node of Ranvier) and Nfasc155 (a glial component of the paranodal axoglial junction). We identified 10 individuals from six unrelated families, exhibiting a neurodevelopmental disorder characterized with a spectrum of central (intellectual disability, developmental delay, motor impairment, speech difficulties) and peripheral (early onset demyelinating neuropathy) neurological involvement, who were found by exome or genome sequencing to carry one frameshift and four different homozygous non-synonymous variants in NFASC. Expression studies using immunostaining-based techniques identified absent expression of the Nfasc155 isoform as a consequence of the frameshift variant and a significant reduction of expression was also observed in association with two non-synonymous variants affecting the fibronectin type III domain. Cell aggregation studies revealed a severely impaired Nfasc155-CNTN1/CASPR1 complex interaction as a result of the identified variants. Immunofluorescence staining of myelinated fibres from two affected individuals showed a severe loss of myelinated fibres and abnormalities in the paranodal junction morphology. Our results establish that recessive variants affecting the Nfasc155 isoform can affect the formation of paranodal axoglial junctions at the nodes of Ranvier. The genetic disease caused by biallelic NFASC variants includes neurodevelopmental impairment and a spectrum of central and peripheral demyelination as part of its core clinical phenotype. Our findings support possible overlapping molecular mechanisms of paranodal damage at peripheral nerves in both the immune-mediated and the genetic disease, but the observation of prominent central neurological involvement in NFASC biallelic variant carriers highlights the importance of this gene in human brain development and function

The TMS Map Scales with Increased Stimulation Intensity and Muscle Activation

One way to study cortical organisation, or its reorganisation, is to use transcranial magnetic stimulation (TMS) to construct a map of corticospinal excitability. TMS maps are reported to be acquired with a wide variety of stimulation intensities and levels of muscle activation. Whilst MEPs are known to increase both with stimulation intensity and muscle activation, it remains to be established what the effect of these factors is on the map's centre of gravity (COG), area, volume and shape. Therefore, the objective of this study was to systematically examine the effect of stimulation intensity and muscle activation on these four key map outcome measures. In a first experiment, maps were acquired with a stimulation intensity of 110, 120 and 130% of resting threshold. In a second experiment, maps were acquired at rest and at 5, 10, 20 and 40% of maximum voluntary contraction. Map area and map volume increased with both stimulation intensity (P 0.09 in all cases). This result indicates the map simply scales with stimulation intensity and muscle activation

Distinct cortical and subcortical structural alterations mirroring daytime‐related seizure occurrence [Abstract]

Purpose: Investigating the daytime‐related patterns of sei-zure presentation might provide important insights into theinvolved epileptogenic networks. However, the alterationsof brain structural integrity linked to different profiles ofseizure occurrence are still not clear. In this study weaddressed the structural magnetic resonance imaging(MRI)‐derived features of the involved cortical and subcor-tical substrates. Method: In 13 patients (mean age ± standard deviation:28±9 years; 9 male) with nocturnal seizures (NS), 12patients (26±9; 3 male) with diurnal seizures (DS) and 10healthy controls (HC) (28±4; 6 male) 3D 3T MRI was per-formed. Cortical and subcortical volumes (hippocampus,amygdala, thalamus) were extracted with the FreeSurferprocessing stream and the between‐group differencesassessed with analysis of variance (ANOVA) and Bonfer-roni post hoc tests. There was no difference between thegroups regarding age (F2,32= 0.26, p = 0.77) and gender(χ†= 5.103, df = 2, p = 0.08). Results: NS group in contrast to DS group showed largervolumes of bilateral insula, superior temporal and orbito-frontal cortices (p = 0.05, corrected). In patients with NScortical volumes of left postcentral and right middle tempo-ral cortices were smaller in comparison to HC. Patientswith DS in comparison to HC displayed reduced corticalvolumes mainly in frontal, temporal and parietal lobes ofthe right hemisphere. Hippocampus analysis showed a sig-nificant group difference (F2,32= 3.643, p = 0.03) withpost hoc test indicating larger volumes in NS group(8208.6±1006.1) vs DS group (3859.1±508.1 mm‡,p = 0.02). For amygdala, ANOVA showed a similar signif-icant group difference (F2,32= 4.341, p = 0.02) with largervolumes in NS group (1797.3±323.2 mm‡) vs DS group(1500.5±246.2 mm‡, p = 0.03). There were no differencesin thalamic volumes between the studied groups. Conclusion: Despite epileptogenesis daytime‐related sei-zures have distinct structural correlates. These alterationscan assign protective or susceptibility properties linked tovigilance or sleep states that could be useful for therapeuticdecisions

Effective deep brain stimulation co-modulate cross-frequency coupling [Abstract]

Objective: The disruption of pathological signals in the cortico-basal ganglia- network has been hypothesized as a mechanism of action of deep brain stimulation (DBS). However, a comprehensive model for DBS modulating oscillations is still missing. Background: Besides considering gamma as physiologic and pro-kinetic, it has been suggested that finely tuned gamma oscillations between 60-90Hz reflect dynamic processing, possibly by inducing local inhibition or facilitation. Most studies investigating gamma focused on oscillations within the STN, motor cortex (M1), supplementary motor area (SMA), and the pallidum (Allert et al., 2018). Furthermore, elements of the BG-thalamocortical network like the premotor (PMC) or prefrontal cortices (PFC) and the sub-cortical network of cerebellum (CB) have been neglected to date. Method: We recorded resting state high-density 256-channels EEG of 31 PD-patients during DBS at the clinically most effective frequency (i.e 130Hz or 160Hz). We compared spectral power and cross-frequency coupling (frequency to power) of cortical and subcortical regions using a beamformer algorithm for coherent sources (Muthuraman et al., 2018). Two clinically ineffective frequencies have been tested as control conditions. Results: We demonstrated that clinically effective STN-DBS alters oscillatory activity in a wide-spread network of cortical and subcortical regions. A reduction of beta and increase of gamma power is attested in the cortical (M1, SMA, PMC, PFC) and sub-cortical network nodes (STN, CB). Additionally, we found increased cross-frequency coupling of narrowband gamma frequencies to the stimulation frequency in the same nodes of the cortico-subcortical network. No such dynamics were revealed within control regions (i.e. posterior parietal cortex). Furthermore, stimulating at lower or higher frequencies did not significantly alter the networks’ source power spectra or cross-frequency coupling. Conclusion: We were able to show a modulation of beta- and gamma-power and cross-frequency coupling during DBS with HD-EEG in a cortical-sub cortical network. DBS does not exclusively influence motor-function but also the physiological processing related to facilitation and dynamic adaptation, in line with the proposed function of gamma oscillations

Multimodal alterations of directed connectivity profiles in patients with attention-deficit/hyperactivity disorders

Functional and effective connectivity measures for tracking brain region interactions that have been investigated using both electroencephalography (EEG) and magnetoencephalography (MEG) bringing up new insights into clinical research. However, the differences between these connectivity methods, especially at the source level, have not yet been systematically studied. The dynamic characterization of coherent sources and temporal partial directed coherence, as measures of functional and effective connectivity, were applied to multimodal resting EEG and MEG data obtained from 11 young patients (mean age 13.2 ± 1.5 years) with attention-deficit/hyperactivity disorder (ADHD) and age-matched healthy subjects. Additionally, machine-learning algorithms were applied to the extracted connectivity features to identify biomarkers differentiating the two groups. An altered thalamo-cortical connectivity profile was attested in patients with ADHD who showed solely information outflow from cortical regions in comparison to healthy controls who exhibited bidirectional interregional connectivity in alpha, beta, and gamma frequency bands. We achieved an accuracy of 98% by combining features from all five studied frequency bands. Our findings suggest that both types of connectivity as extracted from EEG or MEG are sensitive methods to investigate neuronal network features in neuropsychiatric disorders. The connectivity features investigated here can be further tested as biomarkers of ADHD

Directional deep brain stimulation for Parkinson's disease: results of an international crossover study with randomized, double-blind primary endpoint

Objective: Published reports on directional deep brain stimulation (DBS) have been limited to small, single-center investigations. Therapeutic window (TW) is used to describe the range of stimulation amplitudes achieving symptom relief without side effects. This crossover study performed a randomized double-blind assessment of TW for directional and omnidirectional DBS in a large cohort of patients implanted with a DBS system in the subthalamic nucleus for Parkinson’s disease. Materials and Methods: Participants received omnidirectional stimulation for the first three months after initial study pro gramming, followed by directional DBS for the following three months. The primary endpoint was a double-blind, randomized evaluation of TW for directional vs omnidirectional stimulation at three months after initial study programming. Additional data recorded at three- and six-month follow-ups included stimulation preference, therapeutic current strength, Unified Parkinson’s Disease Rating Scale (UPDRS) part III motor score, and quality of life. Results: The study enrolled 234 subjects (62 ± 8 years, 33% female). TW was wider using directional stimulation in 183 of 202 subjects (90.6%). The mean increase in TW with directional stimulation was 41% (2.98 ± 1.38 mA, compared to 2.11 ± 1.33 mA for omnidirectional). UPDRS part III motor score on medication improved 42.4% at three months (after three months of omnidi rectional stimulation) and 43.3% at six months (after three months of directional stimulation) with stimulation on, compared to stimulation off. After six months, 52.8% of subjects blinded to stimulation type (102/193) preferred the period with directional stimulation, and 25.9% (50/193) preferred the omnidirectional period. The directional period was preferred by 58.5% of clinicians (113/193) vs 21.2% (41/193) who preferred the omnidirectional period. Conclusion: Directional stimulation yielded a wider TW compared to omnidirectional stimulation and was preferred by blinded subjects and clinicians

Structural network fingerprints for GPI-DBS in dystonia [Abstract]

Objective: Here, we investigate whether patients who respond to GPi-DBS present different brain global and local network organization and structural MRI fingerprints as derived from 3D MP-RAGE-T1 images, and if these markers could act as predictors for the DBS outcome. Background: Deep brain stimulation (DBS) on the globus pallidus internus (GPi) is an effective evidence-based therapy for dystonia. However, no unequivocal and independent predictors of the clinical response to DBS exist. Moreover, only little is known about the neuromodulatory effects of DBS over the brain networks. Method: Fifty-one patients diagnosed with segmental and generalized dystonia who underwent bilateral GPi-DBS were recruited for this study. Patient’s neurosurgical procedure and clinical data are described elsewhere[1-3]. DBS clinical outcomes were quantified as the improvement percentage in the movement scale, assessed before and 3 years after surgery. The improvement percentage at follow-up was then used to classify the patients as having a moderate- or superior-outcome (threshold of 70%). All patients underwent MRI (1.5T) and a validation cohort was acquired at 3T. MRI data were pre-processed in FreeSurfer to obtain cortical thickness (CT). Network reconstruction from CT estimates was based on the anatomical delimitations of the Desikan-Killiany atlas[4]. The network topology was assessed within the graph theoretical framework using the brain connectivity toolbox[5]. Results: Decreased small-worldness (t=4.7, p=1.8e-5) and normalized path length (t=3.82, p=0.0002), with increased normalized clustering coefficient (t=3.81, p=0.005) and local efficiency (t=1.6, p=0.05) arose for the superior-outcome, indicating long-range disconnection and higher local connectivity. The regional analyses showed that frontal, sensori-motor, temporal and parietal regions had higher degree centrality and clustering in the moderate-outcome network than in the superior-outcome. The structural integrity of cortical regions showing network differences could best discern the clinical responsiveness 3 years after GPi-DBS (AUC=88%). Conclusion: Our study shows that the analysis of morphologic MRI markers and its derived network architecture can be developed into independent predictors for GPi-DBS outcomes at the group and single subject level, which in turn can be used to guide personalized therapeutic approaches when selecting patients who will benefit from this therapy