[Similarities between amyotrophic lateral sclerosis and frontotemporal dementia]

Frontotemporal dementia (FTD) is characterized by degeneration of the frontal and temporal lobes. Classic symptoms include behavioural alterations and executive dysfunction. Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease of the first and second motoneurones, as well as of cortical neurons, presenting with weakness and wasting of the limb, respiratory and bulbar muscles. Accumulation of a mis-localized protein in the neuronal cytoplasma is the main neuropathological marker of ALS but has also been described in certain FTD-variants. Molecules interfering specifically on this level of mis-localization and toxic aggregation may thus represent a very interesting therapeutic approach in both, ALS and FTD.

Relaxation-weighted 23Na magnetic resonance imaging maps regional patterns of abnormal sodium concentrations in amyotrophic lateral sclerosis

Objectives:

Multiparametric magnetic resonance imaging (MRI) is established as a technical instrument for the characterisation of patients with amyotrophic lateral sclerosis (ALS). The contribution of relaxation-weighted sodium (²³NaR) MRI remains to be defined. The aim of this study is to apply ²³NaR MRI to investigate brain sodium homeostasis and map potential alterations in patients with ALS as compared with healthy controls.

Materials and Methods:

Seventeen patients with ALS (mean age 61.1 ± 11.4 years, m/f = 9/8) and 10 healthy control subjects (mean age 60.3 ± 15.3 years, m/f = 6/4) were examined by ²³NaR MRI at 3 T. Regional sodium maps were obtained by the calculation of the weighted difference from two image data sets with different echo times (TE₁ = 0.3 ms, TE₂ = 25 ms). Voxel-based analysis of the relaxation-weighted maps, together with ²³Na concentration maps for comparison, was performed.

Results:

ROI-based analyses of relaxation-weighted brain sodium concentration maps demonstrated increased sodium concentrations in the upper corticospinal tracts and in the frontal lobes in patients with ALS; no differences between ALS patients and controls were found in reference ROIs, where no involvement in ALS-associated neurodegeneration could be anticipated.

Conclusion:

²³NaR MRI mapped regional alterations within disease-relevant areas in ALS which correspond to the stages of the central nervous system (CNS) pathology, providing evidence that the technique is a potential biological marker of the cerebral neurodegenerative process in ALS.

Are nerve conduction studies altered in functional neurological disorders?

•

Central nervous system activity influences generation of F-waves.

•

We report F-wave abnormalities in a patient with a functional neurological disorder.

•

F-waves can be useful in characterising the origin of undetermined muscle weakness.

Background

Functional neurological disorders represent conditions without a readily identifiable origin or laboratory-supported diagnostic. We report a case of functional neurological disorder, presenting with muscle weakness with alterations in F-waves on the affected side.

Case report

A retrospective case review of a patient seen in clinic. Electrophysiological evaluation included nerve conduction studies, including recording of F-waves in lower limbs, and needle EMG. A patchy sensory loss and unilateral muscle weakness of the left lower limb persisted nine days after a 40-year-old female patient developed bilateral lower limb weakness following a laparoscopic surgery. MRI was negative for radicular compression, myelopathy, or lumbosacral plexopathy. F-waves of the peroneal and tibial nerves on the left were absent or of reduced persistence and amplitude compared to the asymptomatic right side.

Significance

The observation of unilateral alterations of F-wave parameters could be interpreted as an asymmetrical decrease of alpha motor neuron excitability on L4 – S2 segments. In the absence of peripheral nervous system dysfunction or a structural lesion, the results here suggest a central control dysfunction or point to a more complex peripheral role. Further research is necessary to determine the frequency of these findings in a larger group of patients while incorporating other late responses, such as H (Hoffman) reflex, and measures of cortical excitability.

[Small fiber neuropathy diagnosis]

Small fiber neuropathies affect small, poorly myelinated sensory Aδ and amyelinated C autonomic fibers. Neuropathic pain is often the main symptom. Positive diagnosis is based on the presence of deficient thermo-algesic sensory signs and/or dysautonomic signs with normal neurography. Several tests help to confirm the involvement of small fibers, ranging from simple tests such as the sympathetic skin response to skin biopsy, which measures the density of intraepidermal nerve fibers. The availability of these different tests varies greatly from one center to another. There are multiple etiologies, from rare genetic causes to the more frequent acquired dysimmune or metabolic causes. However, in more than half of the cases, no etiology is identified.

[Muscle disease in the adults: when to suspect it?]

Muscle diseases or myopathies have heterogeneous clinical presentations and etiologies. The principal sign is muscular weakness, whose distribution can help diagnostic orientation. Exercise intolerance, even without weakness at rest, can indicate an underlying myopathy. An isolated CK elevation can have multiple causes, but its persistence after a period of rest can point towards a subclinical myopathy. Isolated myalgia, especially at rest, are usually not associated with muscle disease. If the suspicion of myopathy is high, the patient will be assessed by a neurologist trained in muscle disorders, with correlation of clinical and neurophysiological findings, muscle imaging and, if indicated, muscle biopsy and genetic analysis. Cardiac and respiratory assessments are mandatory if a myopathy is suspected.

[Treating hereditary neuropathies : a dream come true?]

Hereditary neuropathies have been the subject of recent major therapeutic advances. Treatments based on antisense oligonucleotides (ASO) and small interfering RNA (siRNA) have been developed and are now commercially available to treat hereditary transthyretin amyloidosis (hTTR) and porphyria. More recently, a CRISPR-Cas9 genomic editing treatment targeting the TTR gene has been developed and is being tested in patients with hTTR. Based on their success in hTTR and porphyria, innovative treatments targeting mRNA and DNA are being evaluated in other hereditary neuropathies, including Charcot-Marie-Tooth disease (CMT).

[Neurological shoulder pain and weakness : practical attitudes]

Shoulder pain or paresis should be assessed carefully, as there are many possible causes, which can be osteoarticular, degenerative, inflammatory, or neurological. Weakness or pain can be related to cervicobrachialgia, plexitis, or focal mononeuropathy. The clinical picture should identify any muscular or mechanical origin of paresis responsible for pseudo-paretic functional limitation. Neurogenic scapulalgia with functional deficit implies the compression or entrapment of a nerve trunk including the axillary, long thoracic, accessory, suprascapular, or dorsal scapular nerves. Nerve conduction study and myography together with medical imaging help to identify the relevant etiology. Treatment mostly includes pain relief and physiotherapy, but surgery is rarely necessary.

[What have we learned about chronic inflammatory demyelinating polyradiculoneuropathyin the last twenty years ?]

chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) has been widely described during the last quarter of the twentieth century. The last 20 years have seen decisive progress in its understanding. The diagnostic criteria have been simplified and the steps of the diagnostic process have been clarified. The phenotypic contours of the disease are now well known, as are the diagnostic pitfalls. From a pathophysiological point of view, the discovery of autoantibodies directed against nodal and paranodal proteins has been a major advance, although it concerns only a minority of patients. These discoveries have a major impact on the therapeutic management of these patients, often suffering from a very active form of the disease. The next 20 years will surely see a further deepening of knowledge about this fascinating disease.

[Cramps and fasciculations: is it amyotrophic lateral sclerosis?]

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease of the adult age. It is an aggressive condition with a mean disease duration of only 3 to 5 years, characterized by progressive weakness and atrophy of limb, bulbar, and respiratory muscles. In general, death is caused by chronic hypoventilation due to respiratory insufficiency. No causal treatment is known today, but the two therapeutic agents authorized in Switzerland for the treatment of ALS can slow disease progression significantly. Other important therapeutic strategies include invasive/non-invasive ventilation, pain therapy, as well as physio-, ergo- and speech therapy on a regular basis.

[Muscle cramps]

Muscle cramps are very common and can reduce quality of life. There are multiple causes, including some physiological conditions, metabolic, endocrine, vascular disorders or neuromuscular diseases. Adequate management first requires differentiating cramps from other muscular phenomena. In most cases, the investigations are limited to a comprehensive history and clinical examination, but a biological, radiological and/or electrophysiological work-up may be useful. Treatment, when needed, is most often symptomatic and is unfortunately based on little evidence.

The ipsilateral silent period: an early diagnostic marker of callosal disconnection in ALS

Introduction:

Imaging studies showed affection of the corpus callosum (CC) in amyotrophic lateral sclerosis (ALS). Here, we sought to determine whether these structural alterations reflect on the functional level, using transcranial magnetic stimulation (TMS).

Methods:

In 31 ALS patients and 12 controls, we studied mirror movements (MM) and transcallosal inhibition (TI) using TMS. Structural integrity of transcallosal fibres was assessed using diffusion tensor imaging.

Results:

TI was pathologic in 25 patients (81%), 22 (71%) showed MM. Loss of TI was observed in very early stages (disease duration <4 months). No correlation was found between TI/MM and fractional anisotropy of transcallosal fibres.

Discussion:

These results substantiate the body of evidence towards a functional involvement of the CC in early ALS beyond microstructural alterations.

Significance:

TI may become a useful early diagnostic marker in ALS, even before descending tracts are affected. Diagnostic delay in ALS is high, often preventing patients from gaining access to therapeutic trials, and sensitive diagnostic tools are urgently needed. Our findings also provide insights into the pathophysiology of ALS, potentially supporting the so-called ‘top-down’ hypothesis, that is, corticoefferent (intracortical/corticospinal) propagation. Callosal affection in early stages might represent the ‘missing link’ to explain corticocortical disease-spreading.

Management of transthyretin amyloidosis

Transthyretin amyloidosis (ATTR amyloidosis) is a disease caused by deposition of transthyretin fibrils in organs and tissues, which causes their dysfunction. The clinical heterogeneity of ATTR amyloidosis and the variable presentation of symptoms at early disease stages, historically meant treatment delays. Diagnostic tools and therapy options of ATTR amyloidosis have markedly improved in recent years. The first Swiss Amyloidosis Network (SAN) meeting (Zurich, Switzerland, January 2020) aimed to define a consensus statement regarding the diagnostic work-up and treatment for systemic amyloidosis, tailored to the Swiss healthcare system. A consortium of 45 clinicians and researchers from all Swiss regions and universities was selected by the SAN committee to represent all sub-specialty groups involved in care of patients with amyloidosis. A steering committee conducted the literature search and analysis, wrote the critical synthesis and elaborated a list of statements that were evaluated by all the participants. These recommendations will improve outcomes and quality of life for patients with ATTR amyloidosis. A global review of these guidelines is planned every 3 years with a formal meeting of all the involved experts.

Altered perivascular fibroblast activity precedes ALS disease onset

Apart from well-defined factors in neuronal cells¹, only a few reports consider that the variability of sporadic amyotrophic lateral sclerosis (ALS) progression can depend on less-defined contributions from glia^2,3 and blood vessels⁴. In this study we use an expression-weighted cell-type enrichment method to infer cell activity in spinal cord samples from patients with sporadic ALS and mouse models of this disease. Here we report that patients with sporadic ALS present cell activity patterns consistent with two mouse models in which enrichments of vascular cell genes preceded microglial response. Notably, during the presymptomatic stage, perivascular fibroblast cells showed the strongest gene enrichments, and their marker proteins SPP1 and COL6A1 accumulated in enlarged perivascular spaces in patients with sporadic ALS. Moreover, in plasma of 574 patients with ALS from four independent cohorts, increased levels of SPP1 at disease diagnosis repeatedly predicted shorter survival with stronger effect than the established risk factors of bulbar onset or neurofilament levels in cerebrospinal fluid. We propose that the activity of the recently discovered perivascular fibroblast can predict survival of patients with ALS and provide a new conceptual framework to re-evaluate definitions of ALS etiology.

SARS-CoV-2 and Guillain-Barré syndrome: AIDP variant with a favourable outcome

BACKGROUND AND PURPOSE

The spectrum of COVID-19, caused by severe acute respiratory syndrome coronavirus 2 infection (SARS-CoV-2), includes different neurologic manifestations of the central and peripheral nervous system.

METHODS

From March through April 2020, in two university hospitals located in western Switzerland, we examined three patients with Guillain-Barré syndrome (GBS) following SARS-CoV-2.

RESULTS

These cases were characterized by a primary demyelinating electrophysiological pattern (Acute inflammatory demyelinating polyneuropathy or AIDP) and a less severe disease course compared to recently published case series. Clinical improvement was observed in all patients at week five. One patient was discharged from hospital after full recovery with persistence of minor neurological signs (areflexia). Two of the three patients remained hospitalized: one was able to walk and the other could stand up with assistance.

CONCLUSIONS

We report three cases of typical GBS (AIDP) occurring after SARS-CoV-2 infection and presenting with a favourable clinical course. Given the interval between COVID-19-related symptoms and neurological manifestations (mean of 15 days) we postulate a secondary immune-mediated mechanism rather than direct viral damage.

Expert recommendation from the Swiss Amyloidosis Network (SAN) for systemic AL-amyloidosis

Systemic amyloidosis is a heterogeneous group of diseases associated with protein misfolding into insoluble beta-sheet rich structures that deposit extracellularly in different organs, eventually compromising their function. There are more than 30 different proteins, known to be amyloidogenic with &ldquo;light chain&rdquo; (AL)-amyloidosis being the most common type, followed by transthyretin (ATTR)-, and amyloid protein A (AA)-amyloidosis. Systemic amyloidosis is a rare disease with an incidence of around 10 patients in 1 million inhabitants. Recently several new therapeutic options have been developed for subgroups of amyloidosis patients, and the introduction of novel therapies for plasma cell myeloma has led to an increase in the therapeutic armamentarium for plasma cell disorders, including AL amyloidosis. Among them, proteasome inhibitors, immunomodulatory agents (-imids), and monoclonal antibodies have been successfully introduced into clinical practice. Still, high-quality data from randomised controlled trials regarding the benefit of these cost-intensive drugs in AL amyloidosis are widely lacking, and due to the rarity of the disease many physicians will not gain routine experience in the management of these frail patients. The diagnosis of AL amyloidosis relies on a close collaboration between clinicians, pathologists, imaging experts, and sometimes geneticists. Diagnosis and treatment options in this complex disorder should be discussed in dedicated multidisciplinary boards. In January 2020, the first meeting of the Swiss Amyloidosis Network took place in Zurich, Switzerland. One aim of this meeting was to establish a consensus guideline regarding the diagnostic work-up and the treatment recommendations for systemic amyloidosis tailored to the Swiss health care system. Forty-five participants from different fields in medicine discussed many aspects of amyloidosis. These are the Swiss Amyloidosis Network recommendations which focus on diagnostic work-up and treatment of AL-amyloidosis.

Phenotypes and malignancy risk of different FUS mutations in genetic amyotrophic lateral sclerosis

OBJECTIVE

Mutations in Fused in Sarcoma (FUS or TLS) are the fourth most prevalent in Western European familial amyotrophic lateral sclerosis (ALS) populations and have been associated with causing both early and very late disease onset. FUS aggregation, DNA repair deficiency, and genomic instability are contributors to the pathophysiology of FUS-ALS, but their clinical significance per se and their influence on the clinical variability have yet to be sufficiently investigated. The aim of this study was to analyze genotype-phenotype correlations and malignancy rates in a newly compiled FUS-ALS cohort.

METHODS

We cross-sectionally reviewed FUS-ALS patient histories in a multicenter cohort with 36 novel cases and did a meta-analysis of published FUS-ALS cases reporting the largest genotype-phenotype correlation of FUS-ALS.

RESULTS

The age of onset (median 39 years, range 11-80) was positively correlated with the disease duration. C-terminal domain mutations were found in 90%. Among all, P525L and truncating/ frameshift mutations most frequently caused juvenile onset, rapid disease progression, and atypical ALS often associated with negative family history while the R521 mutation site was associated with late disease onset and pure spinal phenotype. Malignancies were found in one of 40 patients.

INTERPRETATION

We report the largest genotype-phenotype correlation of FUS-ALS, which enables a careful prediction of the clinical course in newly diagnosed patients. In this cohort, FUS-ALS patients did not have an increased risk for malignant diseases.

FUS-mediated regulation of acetylcholine receptor transcription at neuromuscular junctions is compromised in amyotrophic lateral sclerosis

Neuromuscular junction (NMJ) disruption is an early pathogenic event in amyotrophic lateral sclerosis (ALS). Yet, direct links between NMJ pathways and ALS-associated genes such as FUS, whose heterozygous mutations cause aggressive forms of ALS, remain elusive. In a knock-in Fus-ALS mouse model, we identified postsynaptic NMJ defects in newborn homozygous mutants, attributable to mutant FUS toxicity in skeletal muscle. Adult heterozygous knock-in mice displayed smaller neuromuscular endplates that denervated before motor neuron loss, consistent with ‘dying-back’ neuronopathy. FUS was enriched in subsynaptic myonuclei, and this innervation-dependent enrichment was distorted in FUS-ALS. Mechanistically, FUS collaborates with the ETS-transcription factor ERM to stimulate transcription of acetylcholine receptor (AchR) genes. FUS-ALS patient iPSC-derived motor neuron-myotube co-cultures revealed endplate maturation defects due to intrinsic FUS toxicity in both motor neurons and myotubes. Thus, FUS regulates AChR gene expression in subsynaptic myonuclei and muscle-intrinsic toxicity of ALS-mutant FUS may contribute to dying-back motor neuronopathy.

Hot-spot KIF5A mutations cause familial ALS

Heterozygous missense mutations in the N-terminal motor or coiled-coil domains of the kinesin family member 5A (KIF5A) gene cause monogenic spastic paraplegia (HSP10) and Charcot-Marie-Tooth disease type 2 (CMT2). Moreover, heterozygous de novo frame-shift mutations in the C-terminal domain of KIF5A are associated with neonatal intractable myoclonus, a neurodevelopmental syndrome. These findings, together with the observation that many of the disease genes associated with amyotrophic lateral sclerosis disrupt cytoskeletal function and intracellular transport, led us to hypothesize that mutations in KIF5A are also a cause of amyotrophic lateral sclerosis. Using whole exome sequencing followed by rare variant analysis of 426 patients with familial amyotrophic lateral sclerosis and 6137 control subjects, we detected an enrichment of KIF5A splice-site mutations in amyotrophic lateral sclerosis (2/426 compared to 0/6137 in controls; P = 4.2 × 10⁻³), both located in a hot-spot in the C-terminus of the protein and predicted to affect splicing exon 27. We additionally show co-segregation with amyotrophic lateral sclerosis of two canonical splice-site mutations in two families. Investigation of lymphoblast cell lines from patients with KIF5A splice-site mutations revealed the loss of mutant RNA expression and suggested haploinsufficiency as the most probable underlying molecular mechanism. Furthermore, mRNA sequencing of a rare non-synonymous missense mutation (predicting p.Arg1007Gly) located in the C-terminus of the protein shortly upstream of the splice donor of exon 27 revealed defective KIF5A pre-mRNA splicing in respective patient-derived cell lines owing to abrogation of the donor site. Finally, the non-synonymous single nucleotide variant rs113247976 (minor allele frequency = 1.00% in controls, n = 6137), also located in the C-terminal region [p.(Pro986Leu) in exon 26], was significantly enriched in familial amyotrophic lateral sclerosis patients (minor allele frequency = 3.40%; P = 1.28 × 10⁻⁷). Our study demonstrates that mutations located specifically in a C-terminal hotspot of KIF5A can cause a classical amyotrophic lateral sclerosis phenotype, and underline the involvement of intracellular transport processes in amyotrophic lateral sclerosis pathogenesis.

Association of NIPA1 repeat expansions with amyotrophic lateral sclerosis in a large international cohort

NIPA1 (nonimprinted in Prader-Willi/Angelman syndrome 1) mutations are known to cause hereditary spastic paraplegia type 6, a neurodegenerative disease that phenotypically overlaps to some extent with amyotrophic lateral sclerosis (ALS). Previously, a genomewide screen for copy number variants found an association with rare deletions in NIPA1 and ALS, and subsequent genetic analyses revealed that long (or expanded) polyalanine repeats in NIPA1 convey increased ALS susceptibility. We set out to perform a large-scale replication study to further investigate the role of NIPA1 polyalanine expansions with ALS, in which we characterized NIPA1 repeat size in an independent international cohort of 3955 patients with ALS and 2276 unaffected controls and combined our results with previous reports. Meta-analysis on a total of 6245 patients with ALS and 5051 controls showed an overall increased risk of ALS in those with expanded (>8) GCG repeat length (odds ratio = 1.50, p = 3.8×10^-5). Together with previous reports, these findings provide evidence for an association of an expanded polyalanine repeat in NIPA1 and ALS.

ALS-Mimics

Die amyotrophe Lateralsklerose (ALS) ist eine degenerative Erkrankung des motorischen Nervensystems, die mangels kurativer Therapieansätze binnen 3 – 5 Jahren letal verläuft. Eine definitive Diagnosestellung wird aufgrund des oft erst spät im Krankheitsverlauf zur Ausprägung kommenden klassischen Bildes einer ALS häufig verzögert. Einige Krankheitsentitäten können insbesondere in den Anfangsstadien mit einer ALS verwechselt werden. Eine sichere Unterscheidung ist jedoch aufgrund der – im Gegensatz zur ALS – teilweise vorliegenden kausalen Therapiemöglichkeiten essenziell. Da die ALS durch das Vorliegen von Schädigungszeichen des ersten und zweiten Motoneurons charakterisiert ist, sind insbesondere Krankheiten, die diese Merkmale mit der ALS teilen, von Bedeutung. Als Differenzialdiagnose einer ALS mit Betonung des zweiten Motoneurons zu nennen sind: Die immunvermittelten Neuropathien wie die multifokale motorische Neuropathie (MMN) mit ausgeprägten, v. a. distalen Paresen ohne starke Atrophie und dem Nachweis von proximalen Leitungsblöcken in der Elektroneurografie sowie die chronisch inflammatorische demyelinisierende Polyradikuloneuropathie (CIDP), bei der sich im Gegensatz zur ALS häufig Sensibilitätsstörungen und eine Areflexie finden sowie als liquordiagnostisches Merkmal eine zytoalbuminäre Dissoziation vorliegt. Weiterhin die sporadische Einschlusskörperchenmyositis (sIBM), bei der sich typische Biopsiebefunde sowie klinisch ein hauptsächlicher Befall der Fingerflexoren finden und die spinobulbäre Muskelatrophie Typ Kennedy (SBMA), bei der durch die Bestimmung des Androgenrezeptor-(AR-)Gens eine klare Abgrenzung zur ALS getroffen werden kann sowie klinisch Zeichen einer peripheren Androgenresistenz imponieren. Die monomelische Amyotrophie Hirayama zeigt Kälteparesen, ein MRT der HWS sowie eine unauffällige Neurografie sichern die Diagnose. Bei den benignen Faszikulationen fehlen Paresen und Atrophien, im EMG zeigt sich im Gegensatz zur ALS keine pathologische Spontanaktivität. Bei der spinalen Muskelatrophie (SMA) hilft die SMN-Gen-Diagnostik bei der Differenzierung, zudem ist die Erkrankung im Erwachsenenalter sehr selten. Differenzialdiagnosen einer ALS mit z. T. nebeneinander vorkommender Affektion des ersten und zweiten Motoneurons sind metabolische Erkrankungen (Adrenoleukodystrophie, metachromatische Leukodystrophie, Tay-Sachs-Syndrom), hier stellt die Bestimmung der jeweiligen Laborparameter den wichtigsten diagnostischen Schritt dar. Auch eine zervikale Myelopathie kann Zeichen des ersten und zweiten Motoneurons bedingen, kann jedoch mittels MRT der HWS gut unterschieden werden. Als Differenzialdiagnose einer ALS mit Betonung des ersten Motoneurons behandeln wir zudem die hereditäre spastische Paraparese (HSP), die klinisch durch eine symmetrische Spastik der Beine auffällt, im MRT meist eine Atrophie des Myelons zeigt und mittels SPG-Gendiagnostik von der ALS differenziert werden kann.

Comprehensive analysis of the mutation spectrum in 301 German ALS families

OBJECTIVES

Recent advances in amyotrophic lateral sclerosis (ALS) genetics have revealed that mutations in any of more than 25 genes can cause ALS, mostly as an autosomal-dominant Mendelian trait. Detailed knowledge about the genetic architecture of ALS in a specific population will be important for genetic counselling but also for genotype-specific therapeutic interventions.

METHODS

Here we combined fragment length analysis, repeat-primed PCR, Southern blotting, Sanger sequencing and whole exome sequencing to obtain a comprehensive profile of genetic variants in ALS disease genes in 301 German pedigrees with familial ALS. We report C9orf72 mutations as well as variants in consensus splice sites and non-synonymous variants in protein-coding regions of ALS genes. We furthermore estimate their pathogenicity by taking into account type and frequency of the respective variant as well as segregation within the families.

RESULTS

49% of our German ALS families carried a likely pathogenic variant in at least one of the earlier identified ALS genes. In 45% of the ALS families, likely pathogenic variants were detected in C9orf72, SOD1, FUS, TARDBP or TBK1, whereas the relative contribution of the other ALS genes in this familial ALS cohort was 4%. We identified several previously unreported rare variants and demonstrated the absence of likely pathogenic variants in some of the recently described ALS disease genes.

CONCLUSIONS

We here present a comprehensive genetic characterisation of German familial ALS. The present findings are of importance for genetic counselling in clinical practice, for molecular research and for the design of diagnostic gene panels or genotype-specific therapeutic interventions in Europe.

Acute DWI Reductions In Patients After Single Epileptic Seizures - More Common Than Assumed

Background: Changes of cerebral diffusivity detected by magnetic resonance imaging (MRI) have been reported in epilepsy. Diffusion weighted imaging (DWI) detects changes in the distribution of water molecules by measuring the apparent diffusion coefficient (ADC) and is mainly used in the diagnosis of ischemic stroke. DWI changes in epilepsy were reported in status epilepticus (SE) or series of seizures. It remains unclear whether this phenomenon also occurs after single seizures. Accordingly, possible pathomechanisms have only been discussed on the presumed basis of ongoing epileptic brain activity.

Methods: In this retrospective study, we systematically analyzed DWI alterations related to epileptic seizures in 454 patients who received MRI scanning within the first 24 h after seizure onset.

Results: DWI restrictions not classified as ischemic stroke were observed in 18 patients (4%). We found DWI restrictions in 19% of patients with SE/seizure series and in 3% of patients after single focal and 2.5% after single generalized seizures. 17 patients with DWI alterations were diagnosed with a structural epilepsy. DWI signal decreased in the majority of patients within the first days and could not be detected in follow-up imaging >3 months. In all patients except one, DWI alterations were detected in the same hemisphere as the lesion. In the case of seizure series or SE, DWI restrictions mostly presented with a typical “garland-like” pattern alongside the cortical band or on the border of a defined lesion, while in isolated seizures, the restrictions were often rather subtle and small.

Discussion: We show that DWI restrictions can be observed in patients after single epileptic seizures. As the vast majority of these patients was diagnosed with an epilepsy due to structural cerebral pathology, DWI restriction may reflect a higher vulnerability in these regions. This might also explain the fact that diffusivity changes were observed after single focal seizures as well as after multiple seizures or SE. The occurence itself on one side as well as the spatial pattern of this phenomenon on the other may thus not only be related to the duration of ictal activity, but to structural pathology.

In vivo assessment of retinal vessel pathology in amyotrophic lateral sclerosis

BACKGROUND

Changes in skin and muscle small blood vessels (SBVs) and microvascular structures of the brain have been reported in patients with amyotrophic lateral sclerosis (ALS). A direct assessment of brain SBVs in vivo is currently not feasible. Retinal vessels are considered a "mirror" of brain SBVs. In this study, we used optic coherence tomography (OCT)-based measurements to detect changes in retinal blood vessels of ALS patients compared to those of healthy controls.

METHODS

We analysed Spectralis-OCT images of 34 ALS patients and 20 HCs. The inner wall thickness (IWT), outer wall thickness (OWT), and lumen diameter (LD) of retinal vessels were assessed using intensity-based measurements. In addition, the different retinal layers were analysed using automated segmentation software. The correlations between the various retinal layers and clinical parameters [e.g., disease duration and revised ALS functional rating scale (ALS-FRS-R)] were examined.

RESULTS

The OWT of retinal vessels was higher in ALS patients than in HCs (p = 0.04). There were no differences in the IWT, LD. ALS patients showed a thinning of the outer nuclear layer (ONL) compared to HCs (median 1.63 vs. 1.77, p = 0.002). The whole retinal thickness negatively correlated with the ALS-FRS scale (r = 0.3, p = 0.03).

CONCLUSION

Our study reports retinal vessel pathology in ALS patients. These changes may be related to those observed in SBVs in skin and muscle biopsies. Furthermore, we report a thinning of the ONL in ALS, revealing a possible affection of rods and cones function in ALS.

Sequence variations in C9orf72 downstream of the hexanucleotide repeat region and its effect on repeat-primed PCR interpretation: a large multinational screening study

A large GGGGCC-repeat expansion mutation (HREM) in C9orf72 is the most common known cause of ALS and FTD in European populations. Sequence variations immediately downstream of the HREM region have previously been observed and have been suggested to be one reason for difficulties in interpreting RP-PCR data. Our objective was to determine the properties of these sequence variations with regard to prevalence, the range of variation, and effect on disease prognosis. We screened a multi-national cohort (n = 6981) for the HREM and samples with deviant RP-PCR curves were identified. The deviant samples were subsequently sequenced to determine sequence alteration. Our results show that in the USA and European cohorts (n = 6508) 10.7% carried the HREM and 3% had a sequence variant, while no HREM or sequence variants were observed in the Japanese cohort (n = 473). Sequence variations were more common on HREM alleles; however, certain population specific variants were associated with a non-expanded allele.In conclusion, we identified 38 different sequence variants, most located within the first 50 bp downstream of the HREM region. Furthermore, the presence of an HREM was found to be coupled to a lower age of onset and a shorter disease survival, while sequence variation did not have any correlation with these parameters.

Retinal involvement in amyotrophic lateral sclerosis: a study with optical coherence tomography and diffusion tensor imaging

Although motor neuron degeneration is the predominant feature in ALS, recent data point to a more widespread pathology also comprising non-motor symptoms. Retinal thinning has been reported in a variety of neurodegenerative conditions. Yet, studies of retinal involvement in ALS are sparse and results are heterogeneous. We studied retinal alterations in ALS using a systematic approach combining Optical Coherence Tomography (OCT), Diffusion Tensor Imaging (DTI) and clinical phenotyping. We hypothesized that selective changes of specific retinal layers may be a reflection of overall neurodegeneration as measured by DTI. Spectral domain OCT images were analyzed to calculate the average thickness of retinal layers in 71 ALS patients and 20 controls. In 30 patients, the region of interest (ROI) based fractional anisotrophy (FA) was measured in the corticospinal tract (CST), as this region is preferentially affected by motor neuron degeneration. Clinical data were collected for correlation analysis. Patients showed a significant thinning of the inner nuclear layer (INL; p = 0.04) and the retinal nerve fibre layer (RNFL; p = 0.004) compared to controls. We saw significant correlations between retinal thickness and FA values of the CST in patients (p = 0.005). No significant correlation between clinical parameters and retinal involvement was observed. Our study provides evidence for a retinal involvement in ALS. Interestingly, ALS patients show a reduction in FA of the CST, which is correlated to retinal thinning. We conclude that retinal involvement is in fact associated to overall neurodegeneration and may be regarded as a potential technical biomarker in ALS.

De novo FUS mutations are the most frequent genetic cause in early-onset German ALS patients

In amyotrophic lateral sclerosis (ALS) patients with known genetic cause, mutations in chromosome 9 open reading frame 72 (C9orf72) and superoxide dismutase 1 (SOD1) account for most familial and late-onset sporadic cases, whereas mutations in fused in sarcoma (FUS) can be identified in just around 5% of familial and 1% of overall sporadic cases. There are only few reports on de novo FUS mutations in juvenile ALS patients. To date, no systematic evaluation on the frequency of de novo FUS mutations in early-onset ALS patients has been conducted. Here, we screened a cohort of 14 early-onset sporadic ALS patients (onset age <35 years) to determine the frequency of mutations in C9orf72, SOD1, and FUS in this defined patient cohort. All patients were recruited prospectively by a single center in a period of 38 months. No mutations were detected in SOD1 or C9orf72; however, we identified 6 individuals (43%) carrying a heterozygous FUS mutation including 1 mutation that has not been described earlier (c.1504delG [p.Asp502Thrfs*27]). Genetic testing of parents was possible in 5 families and revealed that the mutations in these patients arose de novo. Three of the 6 identified patients presented with initial bulbar symptoms. Our study identifies FUS mutations as the most frequent genetic cause in early-onset ALS. Genetic testing of FUS thus seems indicated in sporadic early-onset ALS patients especially if showing predominant bulbar symptoms and an aggressive disease course.

Serum microRNAs in sporadic amyotrophic lateral sclerosis

MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression and specific mircoRNA "fingerprints" are thought to contribute to and/or reflect certain disease conditions. Recently, we identified surprisingly homogeneous signatures of circulating miRNAs in the serum of familial amyotrophic lateral sclerosis (ALS) patients, which were already present in presymptomatic carriers of ALS gene mutations. Here, we characterize circulating miRNAs in the serum of sporadic ALS patients. We show that, in contrast to familial ALS, miRNA signatures of sporadic ALS are highly heterogeneous suggesting a number of different etiologies. Nevertheless, 2 miRNAs, miR-1234-3p and miR-1825, could be identified to be consistently downregulated in sporadic ALS. Bioinformatic analysis revealed miRNA fingerprints resembling those of familial ALS patients and mutation carriers in 61% of sporadic ALS patients, while the remaining subgroup had clearly different miRNA signatures. These data support a higher than expected contribution of genetic factors also to sporadic ALS. Moreover, our results indicate a more heterogeneous molecular etiology of sporadic ALS compared with (mono)genic cases, which should be considered for the development of disease modifying treatments.

[Amyotrophic lateral sclerosis]

Amyotrophic lateral sclerosis (ALS) is an aggressive degeneration of upper and lower motor neurons and thus affects both the central and the peripheral nervous system. Clinically, the disease is characterized by rapidly progressing atrophy and paresis of all muscle groups with a letal outcome after three to six years due to paresis of the respiratory muscles. So far, no causal treatment is known.

Polymerase chain reaction and Southern blot-based analysis of the C9orf72 hexanucleotide repeat in different motor neuron diseases

The GGGGCC-hexanucleotide repeat expansion in C9orf72 is the most common genetic cause of familial amyotrophic lateral sclerosis and frontotemporal dementia. This study determined the frequency of C9orf72 repeat expansions in different motor neuron diseases (amyotrophic lateral sclerosis (ALS), motor neuron diseases affecting primarily the first or the second motor neuron and hereditary spastic paraplegia). Whereas most studies on C9orf72 repeat expansions published so far rely on a polymerase chain reaction-based screening, we applied both polymerase chain reaction-based techniques and Southern blotting. Furthermore, we determined the sensitivity and specificity of Southern blotting of the C9orf72 hexanucleotide repeat in DNA derived from lymphoblastoid cell lines. C9orf72 repeat expansions were found in 27.1% out of 166 familial ALS patients, only once in 68 sporadic ALS patients, and not in 61 hereditary spastic paraplegia patients or 52 patients with motor neuron diseases affecting clinically primarily either the first or the second motor neuron. We found hints for a correlation between C9orf72 repeat length and the age of onset. Somatic instability of the C9orf72 repeat was observed in lymphoblastoid cell lines compared with DNA derived from whole blood from the same patient and therefore caution is warranted for repeat length determination in immortalized cell lines.

A novel phosphorylation site mutation in profilin 1 revealed in a large screen of US, Nordic, and German amyotrophic lateral sclerosis/frontotemporal dementia cohorts

Profilin 1 is a central regulator of actin dynamics. Mutations in the gene profilin 1 (PFN1) have very recently been shown to be the cause of a subgroup of amyotrophic lateral sclerosis (ALS). Here, we performed a large screen of US, Nordic, and German familial and sporadic ALS and frontotemporal dementia (FTLD) patients for PFN1 mutations to get further insight into the spectrum and pathogenic relevance of this gene for the complete ALS/FTLD continuum. Four hundred twelve familial and 260 sporadic ALS cases and 16 ALS/FTLD cases from Germany, the Nordic countries, and the United States were screened for PFN1 mutations. Phenotypes of patients carrying PFN1 mutations were studied. In a German ALS family we identified the novel heterozygous PFN1 mutation p.Thr109Met, which was absent in controls. This novel mutation abrogates a phosphorylation site in profilin 1. The recently described p.Gln117Gly sequence variant was found in another familial ALS patient from the United States. The ALS patients with mutations in PFN1 displayed spinal onset motor neuron disease without overt cognitive involvement. PFN1 mutations were absent in patients with motor neuron disease and dementia, and in patients with only FTLD. We provide further evidence that PFN1 mutations can cause ALS as a Mendelian dominant trait. Patients carrying PFN1 mutations reported so far represent the "classic" ALS end of the ALS-FTLD spectrum. The novel p.Thr109Met mutation provides additional proof-of-principle that mutant proteins involved in the regulation of cytoskeletal dynamics can cause motor neuron degeneration. Moreover, this new mutation suggests that fine-tuning of actin polymerization by phosphorylation of profilin 1 might be necessary for motor neuron survival.

Combined (1)H and (31)P spectroscopy provides new insights into the pathobiochemistry of brain damage in multiple sclerosis

(1)H MRSI has evolved as an important tool to study the onset and progression of brain damage in multiple sclerosis. Abnormal increases in total creatine, total choline and myoinositol have been noted in multiple sclerosis. However, the pathobiochemical mechanisms related to these changes are still largely unclear. The combination of (1)H MRSI and (1)H-decoupled (31)P MRSI can specify to what extent phosphorylated components of total creatine and total choline contribute to this increase. Combined (1)H and (31)P MRSI data were obtained at 3 T in 22 patients with multiple sclerosis and in 23 healthy controls, and aligned with structural MRI to allow for correction for partial volume effects caused by cerebrospinal fluid and lesion load. A significant increase in total creatine was found in multiple sclerosis, and this was attributed to equal changes in the phosphorylated and unphosphorylated components. The concentrations of the putative glial markers total creatine and myoinositol in lesion-free (1)H MRSI voxels correlated with the global lesion load. We conclude that changes in total creatine are not related to altered energy metabolism, but rather indicate gliosis. Together with the increase in myoinositol, total creatine can be considered as a biomarker for disease severity. A significant total choline increase was mainly a result of choline components not visible by (31)P MRS. The origin of this residual choline fraction remains to be investigated.