Search

Myelination requires extensive plasma membrane rearrangements, implying that molecules controlling membrane dynamics play prominent roles. The large GTPase dynamin 2 (DNM2) is a well-known regulator of membrane remodeling, membrane fission, and vesicular trafficking. Here, we genetically ablated Dnm2 in Schwann cells (SCs) and in oligodendrocytes of mice. Dnm2 deletion in developing SCs resulted in severely impaired axonal sorting and myelination onset. Induced Dnm2 deletion in adult SCs caused a rapidly-developing peripheral neuropathy with abundant demyelination. In both experimental settings, mutant SCs underwent prominent cell death, at least partially due to cytokinesis failure. Strikingly, when Dnm2 was deleted in adult SCs, non-recombined SCs still expressing DNM2 were able to remyelinate fast and efficiently, accompanied by neuropathy remission. These findings reveal a remarkable self-healing capability of peripheral nerves that are affected by SC loss. In the central nervous system, however, we found no major defects upon Dnm2 deletion in oligodendrocytes., Competing Interests: DG, MG, ET, CS, JG, JP, AO, GF, MM, LN, VS, VT, PS, CW, KT, US No competing interests declared, (© 2019, Gerber et al.)

Objective: Spinal and bulbar muscular atrophy (SBMA) is caused by an abnormal expansion of the CAG repeat in the androgen receptor gene. This study aimed to systematically phenotype a German SBMA cohort (n = 80) based on laboratory markers for neuromuscular, metabolic, and endocrine status, and thus provide a basis for the selection of biomarkers for future therapeutic trials., Methods: We assessed a panel of 28 laboratory parameters. The clinical course and blood biomarkers were correlated with disease duration and CAG repeat length. A subset of 11 patients was evaluated with body fat MRI., Results: Almost all patients reported muscle weakness (99%), followed by dysphagia (77%), tremor (76%), and gynecomastia (75%) as major complaints. Creatine kinase was the most consistently elevated (94%) serum marker, which, however, did not relate with either the disease duration or the CAG repeat length. Paresis duration and CAG repeat length correlated with dehydroepiandrosterone sulfate after correction for body mass index and age. The androgen insensitivity index was elevated in nearly half of the participants (48%)., Conclusions: Metabolic alterations in glucose homeostasis (diabetes) and fat metabolism (combined hyperlipidemia), and sex hormone abnormalities (androgen insensitivity) could be observed among SBMA patients without association with the neuromuscular phenotype. Dehydroepiandrosterone sulfate was the only biomarker that correlated strongly with both weakness duration and the CAG repeat length after adjusting for age and BMI, indicating its potential as a biomarker for both disease severity and duration and, therefore, its possible use as a reliable outcome measure in future therapeutic studies.

Myelin formation during peripheral nervous system (PNS) development, and reformation after injury and in disease, requires multiple intrinsic and extrinsic signals. Akt/mTOR signaling has emerged as a major player involved, but the molecular mechanisms and downstream effectors are virtually unknown. Here, we have used Schwann-cell-specific conditional gene ablation of raptor and rictor, which encode essential components of the mTOR complexes 1 (mTORC1) and 2 (mTORC2), respectively, to demonstrate that mTORC1 controls PNS myelination during development. In this process, mTORC1 regulates lipid biosynthesis via sterol regulatory element-binding proteins (SREBPs). This course of action is mediated by the nuclear receptor RXRγ, which transcriptionally regulates SREBP1c downstream of mTORC1. Absence of mTORC1 causes delayed myelination initiation as well as hypomyelination, together with abnormal lipid composition and decreased nerve conduction velocity. Thus, we have identified the mTORC1-RXRγ-SREBP axis controlling lipid biosynthesis as a major contributor to proper peripheral nerve function., (Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.)

Inflammatory neuropathies represent disabling human autoimmune disorders with considerable disease variability. Animal models provide insights into defined aspects of their disease pathogenesis. Forkhead box P3 (FoxP3)+ regulatory T lymphocytes (Treg) are anti-inflammatory cells that maintain immune tolerance and counteract tissue damage in a variety of immune-mediated disorders. Dysfunction or a reduced frequency of Tregs have been associated with different human autoimmune disorders. We here analyzed the functional relevance of Tregs in determining disease manifestation and severity in murine models of autoimmune neuropathies. We took advantage of the DEREG mouse system allowing depletion of Treg with high specificity as well as anti-CD25 directed antibodies to deplete Tregs in mice in actively induced experimental autoimmune neuritis (EAN). Furthermore antibody-depletion was performed in an adoptive transfer model of chronic neuritis. Early Treg depletion increased clinical EAN severity both in active and adoptive transfer chronic neuritis. This was accompanied by increased proliferation of myelin specific T cells and histological signs of peripheral nerve inflammation. Late stage Treg depletion after initial disease manifestation however did not exacerbate inflammatory neuropathy symptoms further. We conclude that Tregs determine disease severity in experimental autoimmune neuropathies during the initial priming phase, but have no major disease modifying function after disease manifestation. Potential future therapeutic approaches targeting Tregs should thus be performed early in inflammatory neuropathies.

Objective: Self-regulation models of coping suggest that patients with chronic diseases reporting low quality of life (QoL), an indicator of failed coping efforts, should show facilitated access to disease related words. Here we investigated whether a reduced N400 amplitude within an incongruent, i.e. unpredictable disease-related context would be a correlate of this facilitated access., Methods: ERPs were recorded in N=18 patients with amyotrophic lateral sclerosis (ALS) and N=20 age-matched healthy controls during reading of sentences, ending either with congruent or incongruent words. Incongruent and congruent words were disease related or disease unrelated. Mean N400 amplitudes were analyzed with mixed models., Results: Generally, incongruent words elicited a more negative N400 amplitude than congruent words in all groups and conditions, i.e. an N400 effect. In patients with high QoL this N400 effect did not differ between disease related and unrelated words. In patients with low QoL, however, the N400 effect was significantly smaller for disease related than for disease unrelated words. In healthy controls N400 amplitudes showed no such interaction between congruence, disease relatedness and QoL. Results remained stable when controlling for disease severity, duration and depression., Conclusion: The N400 indicates increased accessibility to disease related information in ALS patients with low QoL. The increased access may imply a constantly activated disease related context which is linked to low QoL., Significance: N400 modulation by disease related information may serve as a psychophysiological correlate of coping and the patient's QoL., (Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

The ganglioside-induced differentiation-associated protein 1 (GDAP1) is a mitochondrial fission factor and mutations in GDAP1 cause Charcot-Marie-Tooth disease. We found that Gdap1 knockout mice (Gdap1(-/-)), mimicking genetic alterations of patients suffering from severe forms of Charcot-Marie-Tooth disease, develop an age-related, hypomyelinating peripheral neuropathy. Ablation of Gdap1 expression in Schwann cells recapitulates this phenotype. Additionally, intra-axonal mitochondria of peripheral neurons are larger in Gdap1(-/-) mice and mitochondrial transport is impaired in cultured sensory neurons of Gdap1(-/-) mice compared with controls. These changes in mitochondrial morphology and dynamics also influence mitochondrial biogenesis. We demonstrate that mitochondrial DNA biogenesis and content is increased in the peripheral nervous system but not in the central nervous system of Gdap1(-/-) mice compared with control littermates. In search for a molecular mechanism we turned to the paralogue of GDAP1, GDAP1L1, which is mainly expressed in the unaffected central nervous system. GDAP1L1 responds to elevated levels of oxidized glutathione by translocating from the cytosol to mitochondria, where it inserts into the mitochondrial outer membrane. This translocation is necessary to substitute for loss of GDAP1 expression. Accordingly, more GDAP1L1 was associated with mitochondria in the spinal cord of aged Gdap1(-/-) mice compared with controls. Our findings demonstrate that Charcot-Marie-Tooth disease caused by mutations in GDAP1 leads to mild, persistent oxidative stress in the peripheral nervous system, which can be compensated by GDAP1L1 in the unaffected central nervous system. We conclude that members of the GDAP1 family are responsive and protective against stress associated with increased levels of oxidized glutathione.

Introduction: In monoclonal gammopathy, organ dysfunction can occur due to deposition of immunoglobulin fragments. A rare form of acquired myopathy often associated with monoclonal gammopathy is sporadic late onset nemaline myopathy (SLONM), which is characterized by nemaline rods in myofibers. The pathogenetic link between monoclonal gammopathy and SLONM has not yet been elucidated., Methods: Case report of a patient with monoclonal gammopathy who developed a progressive myopathy, finally diagnosed as SLONM., Results: A muscle biopsy showed mild myopathic changes. A second biopsy 1 year after clinical onset demonstrated deposition of immunoglobulin light and heavy chains and the presence of nemaline rods. The patient experienced marked improvement of muscle strength after autologous stem cell transplantation and treatment with bortezomib, a therapy that is known to be effective in light chain deposition disease., Conclusions: We speculate that deposition of light and heavy chains, rather than nemaline bodies, has myotoxic effects on skeletal muscle., (Copyright © 2013 Wiley Periodicals, Inc.)

Objectives: Recently, we proposed a new stimulation paradigm for brain computer interfaces (BCI) based on event-related potentials (ERP), i.e. flashing characters with superimposed pictures of well-known faces. This new face flashing (FF) paradigm significantly outperformed the commonly used character flashing (CF) approach, i.e. simply highlighting characters., Methods: In the current study we assessed the impact of face stimuli on BCI inefficiency in patients with neurodegenerative disease, i.e. on their inability to communicate by means of a BCI. Healthy participants (N = 16) and those with neurodegenerative disease (N = 9) performed spelling tasks using CF and FF paradigms., Results: Online performance with FF was significantly increased as compared to CF in both, healthy and impaired users. Importantly, two patients who were classified "highly inefficient" with the classic CF stimulation were able to spell with high accuracy using FF. Our results particularly emphasize great benefit of the FF paradigm for those users displaying low signal-to-noise ratio of the recorded ERPs in the classic stimulation approach., Conclusion: In conclusion, we confirm previously reported results now systematically validated in an online setting and display specifically beneficial effects of FF for motor-impaired users., Significance: The FF paradigm thus constitutes a big step forward against the BCI inefficiency phenomenon., (Copyright © 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)

Introduction: Reversible posterior leukoencephalopathy syndrome - a reversible subacute global encephalopathy clinically presenting with headache, altered mental status, visual symptoms such as hemianopsia or cortical blindness, motor symptoms, and focal or generalized seizures - is characterized by a subcortical vasogenic edema symmetrically affecting posterior brain regions. Complete reversibility of both clinical signs and magnetic resonance imaging lesions is regarded as a defining feature of reversible posterior leukoencephalopathy syndrome. Reversible posterior leukoencephalopathy syndrome is almost exclusively seen in the setting of a predisposing clinical condition, such as pre-eclampsia, systemic infections, sepsis and shock, certain autoimmune diseases, various malignancies and cytotoxic chemotherapy, transplantation and concomitant immunosuppression (especially with calcineurin inhibitors) as well as episodes of abrupt hypertension. We describe for the first time clinical, radiological and histological findings in a case of reversible posterior leukoencephalopathy syndrome with an irreversible and fatal outcome occurring in the absence of any of the known predisposing clinical conditions except for a hypertensive episode., Case Presentation: A 58-year-old Caucasian woman presented with a two-week history of subacute and progressive occipital headache, blurred vision and imbalance of gait and with no evidence for raised arterial blood pressure during the two weeks previous to admission. Her past medical history was unremarkable except for controlled arterial hypertension. Cerebral magnetic resonance imaging demonstrated cortical and subcortical lesions with combined vasogenic and cytotoxic edema atypical for both venous congestion and arterial infarction. Routine laboratory and cerebrospinal fluid parameters were normal. The diagnosis of reversible posterior leukoencephalopathy syndrome was established.Within hours after admission the patient showed a rapidly decreasing level of consciousness, extension and flexion synergisms, bilaterally extensor plantar responses and rapid cardiopulmonary decompensation requiring ventilatory and cardiocirculatory support. Follow-up cerebral imaging demonstrated widespread and confluent cytotoxic edematous lesions in different arterial territories, global cerebral swelling, and subsequent upper and lower brainstem herniation. Four days after admission, the patient was declared dead because of brain death., Conclusion: This case demonstrates that fulminant and fatal reversible posterior leukoencephalopathy syndrome may occur spontaneously, that is, in the absence of any of the known predisposing systemic conditions.

Studying the function and malfunction of genes and proteins associated with inherited forms of peripheral neuropathies has provided multiple clues to our understanding of myelinated nerves in health and disease. Here, we have generated a mouse model for the peripheral neuropathy Charcot-Marie-Tooth disease type 4H by constitutively disrupting the mouse orthologue of the suspected culprit gene FGD4 that encodes the small RhoGTPase Cdc42-guanine nucleotide exchange factor Frabin. Lack of Frabin/Fgd4 causes dysmyelination in mice in early peripheral nerve development, followed by profound myelin abnormalities and demyelination at later stages. At the age of 60 weeks, this was accompanied by electrophysiological deficits. By crossing mice carrying alleles of Frabin/Fgd4 flanked by loxP sequences with animals expressing Cre recombinase in a cell type-specific manner, we show that Schwann cell-autonomous Frabin/Fgd4 function is essential for proper myelination without detectable primary contributions from neurons. Deletion of Frabin/Fgd4 in Schwann cells of fully myelinated nerve fibres revealed that this protein is not only required for correct nerve development but also for accurate myelin maintenance. Moreover, we established that correct activation of Cdc42 is dependent on Frabin/Fgd4 function in healthy peripheral nerves. Genetic disruption of Cdc42 in Schwann cells of adult myelinated nerves resulted in myelin alterations similar to those observed in Frabin/Fgd4-deficient mice, indicating that Cdc42 and the Frabin/Fgd4-Cdc42 axis are critical for myelin homeostasis. In line with known regulatory roles of Cdc42, we found that Frabin/Fgd4 regulates Schwann cell endocytosis, a process that is increasingly recognized as a relevant mechanism in peripheral nerve pathophysiology. Taken together, our results indicate that regulation of Cdc42 by Frabin/Fgd4 in Schwann cells is critical for the structure and function of the peripheral nervous system. In particular, this regulatory link is continuously required in adult fully myelinated nerve fibres. Thus, mechanisms regulated by Frabin/Fgd4-Cdc42 are promising targets that can help to identify additional regulators of myelin development and homeostasis, which may crucially contribute also to malfunctions in different types of peripheral neuropathies.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disease caused by a functional deficiency of arylsulfatase A (ASA). Previous studies in ASA-knockout mice suggested enzyme replacement therapy (ERT) to be a promising treatment option. The mild phenotype of ASA-knockout mice did, however, not allow to examine therapeutic responses of the severe neurological symptoms that dominate MLD. We, therefore, generated an aggravated MLD mouse model displaying progressive demyelination and reduced nerve conduction velocity (NCV) and treated it by weekly intravenous injections of 20 mg/kg recombinant human ASA for 16 weeks. To analyze the stage-dependent therapeutic effects, ERT was initiated in a presymptomatic, early and progressed disease stage, at age 4, 8 and 12 months, respectively. Brain sulfatide storage, NCV and behavioral alterations were improved only in early, but not in late, treated mice showing a clear age-dependent efficacy of treatment. Hematopoietic stem cell transplantation (HSCT) for late-onset variants is the only therapeutic option for MLD to date. ERT resembles a part of the HSCT rationale, which is based on ASA supply by donor cells. Beyond ERT, our results, therefore, corroborate the clinical observation that HSCT is only effective when performed in early stages of disease.

Background: Pioglitazone, an oral anti-diabetic that stimulates the PPAR-gamma transcription factor, increased survival of mice with amyotrophic lateral sclerosis (ALS)., Methods/principal Findings: We performed a phase II, double blind, multicentre, placebo controlled trial of pioglitazone in ALS patients under riluzole. 219 patients were randomly assigned to receive 45 mg/day of pioglitazone or placebo (one: one allocation ratio). The primary endpoint was survival. Secondary endpoints included incidence of non-invasive ventilation and tracheotomy, and slopes of ALS-FRS, slow vital capacity, and quality of life as assessed using EUROQoL EQ-5D. The study was conducted under a two-stage group sequential test, allowing to stop for futility or superiority after interim analysis. Shortly after interim analysis, 30 patients under pioglitazone and 24 patients under placebo had died. The trial was stopped for futility; the hazard ratio for primary endpoint was 1.21 (95% CI: 0.71-2.07, p = 0.48). Secondary endpoints were not modified by pioglitazone treatment. Pioglitazone was well tolerated., Conclusion/significance: Pioglitazone has no beneficial effects on the survival of ALS patients as add-on therapy to riluzole., Trial Registration: Clinicaltrials.gov NCT00690118.

Emery-Dreifuss muscular dystrophy (EDMD) is a hereditary neuromuscular disorder characterized by slowly progressive muscle weakness, early contractures, and dilated cardiomyopathy. We reported an uneventful general anaesthesia using total intravenous anaesthesia (TIVA) for cardiac transplantation in a 19-year-old woman suffering from EDMD. In vitro contracture test results of two pectoralis major muscle bundles of the patient suggest that exposition to triggering agents does not induce a pathological sarcoplasmic calcium release in the lamin A/C phenotype. However, due to the lack of evidence in the literature, we would recommend TIVA for patients with EDMD if general anaesthesia is required.

Visualization of neuroinflammation is still a major task in neuroscience and neurology since inflammatory processes play a central pathophysiological role in many disorders of the nervous system but are not yet covered by conventional imaging techniques. Recently, (19)F magnetic resonance imaging (MRI) was introduced as a new cellular imaging technology. In the present study, we established (19)F high field MRI for cell tracking in the peripheral nervous system (PNS) of rats using dedicated MR coils. To mimic focal neuroinflammation, lysolecithin was locally injected into the left sciatic nerve inducing demyelination followed by severe infiltration of monocytes/macrophages from the circulation. Systemic administration of perfluorocarbons (PFC) led to a fluorine signal along the proximal stretch of the affected sciatic nerves in in vivo(19)F MRI which was not seen on the right healthy side. The preferential in vivo uptake of PFC by circulating mononuclear cells was confirmed by density gradient centrifugation of the blood. Removal of nerves with consecutive ex vivo(19)F MRI and additional (19)F spectroscopy for quantification corroborated the localization of the (19)F marker within the injured nerves (1.07×10(18)±1.00×10(18) mean detectable fluorine spins) while contralateral naive nerves did not exhibit any detectable fluorine signal. Histological assessment confirmed the presence of numerous ED1-positive macrophages within the nerve lesions. Control experiments showed that intraneural application of saline led to an inflammatory reaction restricted to the perineurium which could also be detected by (19)F MRI. In conclusion, we show that (19)F MRI is a promising new technology to visualize hematogenous macrophage responses in the nervous system., (Copyright © 2011 Elsevier Inc. All rights reserved.)

We report on magnetic resonance neurography (MRN) as a supplementary diagnostic tool in sciatic nerve injection injury. The object of the study was to test if T2-weighted (w) contrast within the sciatic nerve serves as an objective criterion for sciatic injection injury. Three patients presented with acute sensory and/or motor complaints in the distribution of the sciatic nerve after dorsogluteal injection and underwent MRN covering gluteal, thigh and knee levels. Native and contrast-enhanced T1-w images were employed to identify the tibial and peroneal division of the sciatic nerve while T2-w images with fat suppression allowed visualization of the site and extent of the nerve lesion. MRN in the two patients with clinically severe sensory and motor impairment correctly depicted sciatic injury: continuity of the T2-w lesion within the nerve at the lesion site and distal to it corresponded well to severe injury confirmed by NCS/EMG as axonotmetic or neurotmetic. Topography of the T2-w lesion on cross-section corresponded to predominant peroneal involvement; moreover, associated denervation patterns of distal target muscles were revealed. One of these patients completely recovered with concomitant complete regression of MRN abnormalities on follow-up. The third patient experienced transient sensory and mild motor impairment with complete recovery after 2 weeks. In this patient, T2-w signal within the nerve and distal target muscles remained normal indicating only mild, non-axonal nerve affliction. Our case series shows that MRN can be very useful in precisely determining the site of sciatic injection injury and may provide diagnostic criteria for the assessment of lesion severity and recovery.

Amyotrophic lateral sclerosis (ALS), the major form of motor neuron disease in the adult occurs as a sporadic disease in more than 95% of all cases. Analysis of familial forms is considered as a key to understand the pathophysiology of the disease. It is expected that mutations responsible for familial forms are also found in sporadic ALS. During the past years, several loci and genes have been identified in which disease associated mutations have been discovered. We report here on the screening of 596 sporadic ALS patients, 41 familial ALS cases and other motor neuron disease patients from Germany for mutations in the FUS/TLS gene. Sequencing of the last two exons in all patients revealed the C1561T transversion, which leads to the amino acid substitution at R521C, in one familial and one sporadic ALS patient. In addition three patients with a synonymous mutation at codon 522 were identified. None of these variants were present in the control population. Our results indicate that mutations in FUS/TLS are not a major cause of sporadic ALS in the German population., (Copyright © 2009. Published by Elsevier Inc.)

The blood-nerve barrier (BNB) separates the endoneurium from the endovascular space and the epineurial connective tissue. An intact BNB is very important for integrity and functions of the nerve fibers within the endoneurial space. Disruption of the BNB which leads to functional and structural impairment of the peripheral nerve plays an important role in many disorders of the peripheral nerve like Wallerian degeneration, inflammatory nerve disorders, and demyelination. So far, this increased BNB permeability can only be assessed ex vivo. Assessing BNB disruption in vivo would be of great value for studying disorders of the peripheral nervous system. Gadofluorine M (Gf), a new amphiphilic contrast agent for MRI, accumulates in rat nerves with increased permeability of the BNB. After application of Gf, T1-weighted MR images show contrast enhancement of nerves with a disrupted BNB. This new tool of assessing BNB permeability in vivo is described.

Synaptic inhibition is a central factor in the fine tuning of neuronal activity in the central nervous system. Symptoms consistent with reduced inhibition such as stiffness, spasms and anxiety occur in paraneoplastic stiff person syndrome with autoantibodies against the intracellular synaptic protein amphiphysin. Here we show that intrathecal application of purified anti-amphiphysin immunoglobulin G antibodies induces stiff person syndrome-like symptoms in rats, including stiffness and muscle spasms. Using in vivo recordings of Hoffmann reflexes and dorsal root potentials, we identified reduced presynaptic GABAergic inhibition as an underlying mechanism. Anti-amphiphysin immunoglobulin G was internalized into neurons by an epitope-specific mechanism and colocalized in vivo with presynaptic vesicular proteins, as shown by stimulation emission depletion microscopy. Neurons from amphiphysin deficient mice that did not internalize the immunoglobulin provided additional evidence of the specificity in antibody uptake. GABAergic synapses appeared more vulnerable than glutamatergic synapses to defective endocytosis induced by anti-amphiphysin immunoglobulin G, as shown by increased clustering of the endocytic protein AP180 and by defective loading of FM 1-43, a styryl dye used to label cell membranes. Incubation of cultured neurons with anti-amphiphysin immunoglobulin G reduced basal and stimulated release of γ-aminobutyric acid substantially more than that of glutamate. By whole-cell patch-clamp analysis of GABAergic inhibitory transmission in hippocampus granule cells we showed a faster, activity-dependent decrease of the amplitude of evoked inhibitory postsynaptic currents in brain slices treated with antibodies against amphiphysin. We suggest that these findings may explain the pathophysiology of the core signs of stiff person syndrome at the molecular level and show that autoantibodies can alter the function of inhibitory synapses in vivo upon binding to an intraneuronal key protein by disturbing vesicular endocytosis.

The chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2) has been previously shown to be an important mediator of macrophage-related neural damage in models of two distinct inherited neuropathies, Charcot-Marie-Tooth (CMT) 1A and 1B. In mice deficient in the gap junction protein connexin 32 (Cx32def), an established model for the X-chromosome-linked dominant form of CMT (CMT1X), we investigated the role of the chemokine in macrophage immigration and neural damage by crossbreeding the Cx32def mice with MCP-1 knockout mutants. In Cx32def mutants typically expressing increased levels of MCP-1, macrophage numbers were strongly elevated, caused by an MCP-1-mediated influx of haematogenous macrophages. Curiously, the complete genetic deletion of MCP-1 did not cause reduced macrophage numbers in the nerves due to compensatory proliferation of resident macrophages. In contrast, and as already seen in other CMT models, heterozygous deletion of MCP-1 led to reduced numbers of phagocytosing macrophages and an alleviation of demyelination. Whereas alleviated demyelination was transient, axonal damage was persistently improved and even robust axonal sprouting was detectable at 12 months. Other axon-related features were alleviated electrophysiological parameters, reduced muscle denervation and atrophy, and increased muscle strength. Similar to models for CMT1A and CMT1B, we identified MEK-ERK signalling as mediating MCP-1 expression in Cx32-deficient Schwann cells. Blocking this pathway by the inhibitor CI-1040 caused reduced MCP-1 expression, attenuation of macrophage increase and amelioration of myelin- and axon-related alterations. Thus, attenuation of MCP-1 upregulation by inhibiting ERK phosphorylation might be a promising approach to treat CMT1X and other so far untreatable inherited peripheral neuropathies in humans.

Objective: To illustrate magnetic resonance neurography findings of severe sciatic injury and muscle denervation related to deep gluteal endometriosis at the sciatic notch., Design: Case report., Setting: Academic teaching hospital., Patient(s): A 39-year-old woman with a 4-year history of sciatica related to the menstrual cycle., Intervention(s): Surgical exploration of the sciatic notch for diagnostic confirmation, external neurolysis of the sciatic nerve, and eventual pharmacologic treatment., Main Outcome Measure(s): Magnetic resonance neurography imaging revealed severe neuropathic injury and muscle denervation related to a deep infiltrative endometriotic focus at the sciatic notch, which was confirmed histologically on surgical exploration. Detailed electrodiagnostic and clinical neurologic examinations at initial presentation and during follow-up were obtained for further assessment of nerve degeneration, muscle denervation, and clinical recovery., Result(s): Initial gynecologic and eventual laparoscopic evaluation on persisting complaints were without pathological findings. When a progressive weakness of the leg was noted, magnetic resonance neurography revealed a severe axonal damage to the sciatic nerve and denervation of distal target muscles related to a diffuse infiltrative lesion at the sciatic notch. On surgical exploration, extragenital endometriosis was confirmed histologically. Considerable improvement in pain and strength occurred after pharmacologic therapy with a GnRH analogue., Conclusion(s): This is the first report to describe imaging findings of magnetic resonance neurography in severe neuropathic injury of the sciatic nerve and subsequent muscle denervation related to a deep infiltrative gluteal endometriotic focus., (Copyright (c) 2010 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.)

We have previously shown that in two distinct models for inherited neuropathies of the Charcot-Marie-Tooth (CMT) type, T-lymphocytes are critically involved in demyelination. In the present study, we tested whether T-lymphocytes have a similar pathogenetic impact in another CMT model, i.e., in mice overexpressing the peripheral myelin protein (PMP)-22, representing the most prevalent form CMT1A. By cross breeding the myelin mutant mice with mutants lacking mature T- and B-lymphocytes (RAG-1-deficient mice), the pathological alterations were not changed in comparison to PMP22 mutants with a normal immune system. Reciprocal enhancement of lymphocyte activation, by inactivation of the lymphocytic co-inhibitor programmed death-1, also did not alter pathological changes, as opposed to models with approved lymphocytic involvement. These findings strongly suggest that lymphocytes are not pathogenetically relevant in this model for CMT1A. We suggest that - in contrast to myelin phagocytosing macrophages - T-lymphocytes are not a promising target for treatment of CMT1A., (Copyright 2010 Elsevier Inc. All rights reserved.)

Charcot-Marie-Tooth 1A (CMT1A) neuropathy, the most common inherited peripheral neuropathy, is primarily caused by a gene duplication for the peripheral myelin protein-22 (PMP22). In an accordant mouse model, we investigated the role of monocyte chemoattractant protein-1 (MCP-1/CCL2) as a regulator of nerve macrophages and neural damage including axonopathy and demyelination. By generating PMP22tg mice with reduced levels or lack of MCP-1/CCL2, we found that MCP-1/CCL2 is involved in the increase of macrophages in mutant nerves. PMP22tg mice with wild-type levels of MCP-1/CCL2 showed strong macrophage increase in the diseased nerves, whereas either 50% reduction or total absence of MCP-1/CCL2 led to a moderate or a strong reduction of nerve macrophages, respectively. Interestingly, MCP-1/CCL2 expression level and macrophage numbers were correlated with features indicative of axon damage, such as maldistribution of K+ channels, reduced compound muscle action potentials, and muscle weakness. Demyelinating features, however, were most highly reduced when MCP-1/CCL2 was diminished by 50%, whereas complete lack of MCP-1/CCL2 showed an intermediate demyelinating phenotype. We also identified the MEK1/2-ERK1/2-pathway as being involved in MCP-1/CCL2 expression in the Schwann cells of the CMT1A model. Our data show that, in a CMT1A model, MCP-1/CCL2 activates nerve macrophages, mediates both axon damage and demyelination, and may thus be a promising target for therapeutic approaches.

The integrity of peripheral nerves relies on communication between axons and Schwann cells. The axonal signals that ensure myelin maintenance are distinct from those that direct myelination and are largely unknown. Here we show that ablation of the prion protein PrP(C) triggers a chronic demyelinating polyneuropathy (CDP) in four independently targeted mouse strains. Ablation of the neighboring Prnd locus, or inbreeding to four distinct mouse strains, did not modulate the CDP. CDP was triggered by depletion of PrP(C) specifically in neurons, but not in Schwann cells, and was suppressed by PrP(C) expression restricted to neurons but not to Schwann cells. CDP was prevented by PrP(C) variants that undergo proteolytic amino-proximal cleavage, but not by variants that are nonpermissive for cleavage, including secreted PrP(C) lacking its glycolipid membrane anchor. These results indicate that neuronal expression and regulated proteolysis of PrP(C) are essential for myelin maintenance.

Late-onset glycogen storage disease type 2 (GSD2)/Pompe disease is a progressive multi-system disease evoked by a deficiency of lysosomal acid alpha-glucosidase (GAA) activity. GSD2 is characterized by respiratory and skeletal muscle weakness and atrophy, resulting in functional disability and reduced life span. Since 2006 alglucosidase alfa has been licensed as a treatment in all types of GSD2/Pompe disease. We here present an open-label, investigator-initiated observational study of alglucosidase alfa enzyme replacement therapy (ERT) in 44 late-onset GSD2 patients with various stages of disease severity. Alglucosidase alfa was given i.v. at the standard dose of 20 mg/kg every other week. Assessments included serial arm function tests (AFT), Walton Gardner Medwin scale (WGMS), timed 10-m walk tests, four-stair climb tests, modified Gowers' maneuvers, 6-min walk tests, MRC sum score, forced vital capacities (FVC), creatine kinase (CK) levels and SF-36 self-reporting questionnaires. All tests were performed at baseline and every 3 months for 12 months of ERT. We found significant changes from baseline in the modified Gowers' test, the CK levels and the 6-min walk test (341 +/- 149.49 m, median 342.25 m at baseline; 393 +/- 156.98 m; median 411.50 m at endpoint; p = 0.026), while all other tests were unchanged. ERT over 12 months revealed minor allergic reactions in 10% of the patients. No serious adverse events occurred. None of the patients died or required de novo ventilation. Our clinical outcome data imply stabilization of neuromuscular deficits over 1 year with mild functional improvement.

We describe an inflammatory myopathy that was symmetrically restricted to both gastrocnemius muscles in a young man. Histopathological findings were typical for polymyositis, but there were neither signs of generalization nor muscle weakness and wasting. This condition was highly sensitive to steroids and has been kept in remission for more than a year using azathioprine. Our findings add another entity to the spectrum of spatially restricted inflammatory myopathies. Muscle Nerve 40: 309-312, 2009.

Mice hetero- or homozygously deficient for myelin protein zero (P0+/-, P0-/- mice) are models for distinct forms of inherited de- or dysmyelinating neuropathies, respectively. P0+/- mice show a demyelinating neuropathy with a pathogenetic implication of CD8+ T-lymphocytes and macrophages, while P0-/- mice show dysmyelination with axonal loss. It was, therefore, of interest to treat both mutants with FK506 (Tacrolimus), an agent with immunosuppressive and neuroprotective properties. Treatment of P0+/- mice led to an aggravation of demyelination, without affecting nervous CD8+ T-lymphocytes, but reducing splenic CD4+ cells. Treatment of P0-/- mice resulted in a substantial increase of the dysmyelination-related axon loss. Treatment of wildtype mice did not cause pathological changes in peripheral nerves. Our study shows that FK506 may not be suitable for the treatment of the human nerve disorders. Furthermore, when used as an immunosuppressant, the drug may generate detrimental neurological side effects in patients with an additional hereditary neuropathy.

Magnetic resonance imaging (MRI) is a powerful tool to assess brain lesions, but currently available contrast agents are limited in the assessment of cellular and functional alterations. By use of the novel MRI contrast agent gadofluorine M (Gf) we report on imaging of transient and widespread changes of blood-brain barrier (BBB) properties as a consequence of focal photothrombotic brain lesions in rats. After i.v. application, Gf led to bright contrast in the lesions, but also the entire ipsilateral cortex on T1-weighted MRI. In contrast, enhancement after application of gadolinium diethylenetriamine-pentaacetic acid (Gd-DTPA), a common clinical indicator of BBB leakage was restricted to the lesions. Remote Gf enhancement was restricted in time to the first 24 h after photothrombosis and corresponded to a transient breakdown of the BBB as revealed by extravasation of the dye Evans blue. In conclusion, our study shows that Gf can visualize subtle disturbances of the BBB in three dimensions not detectable by Gd-DTPA. Upon entry into the central nervous system Gf most likely is locally trapped by interactions with extracellular matrix proteins. The unique properties of Gf hold promise as a more sensitive contrast agent for monitoring BBB disturbances in neurologic disorders, which appear more widespread than anticipated previously.

We have previously shown that mice heterozygously deficient for P0 are characterized by a late onset myelin disorder implicating CD8+ T-lymphocytes and macrophages. We now investigated the impact of the co-inhibitory molecule "programmed death" (PD)-1 (CD279), a CD28-related receptor expressed on activated T- and B-lymphocytes on the pathogenic phenotype of CD8+ T-lymphocytes in the P0 myelin mutants. PD-1 deficiency in P0+/- mice leads to a stronger increase of CD8+ T-lymphocytes and a substantially aggravated histological phenotype in the PNS compared to P0+/- mice expressing PD-1. Correspondingly, functional down-stream features, such as electrophysiological parameters, walking coordination and mechano-sensation are more affected than in PD-1-expressing myelin mutants. Our study demonstrates that a monogenic nerve disorder can be substantially modified by immune-controlling mechanisms. Thus, understanding the implication of disease-modifiers in inherited demyelination could be of pivotal interest for limiting the detrimental impact of primarily genetically-mediated myelin disorders by fostering immuno-regulatory pathways.

Nerve imaging by magnetic resonance imaging (MRI) is an emerging tool for the diagnostic work-up of patients with PNS disorders. We have recently shown that the experimental MR contrast agent gadofluorine M (Gf, Bayer Schering Pharma AG, Berlin) accumulates in nerves undergoing Wallerian degeneration and in areas of acute focal demyelination allowing in-vivo assessment of nerve pathology. The exact pathomechanism underlying Gf accumulation in peripheral nerve disorders is unknown so far. In the present study we compared nerve signal alterations on T2-w and Gf-enhanced T1-w MRI in two different models of acute inflammatory and chronic degenerative demyelination: experimental autoimmune neuritis (EAN) induced by immunization with PNS myelin and experimental Charcot-Marie-Tooth (CMT) disease in rats overexpressing the myelin protein PMP22. During the acute stage of inflammation and demyelination, strong Gf enhancement on T1-w MRI was seen in nerve roots and peripheral nerves in EAN, which resolved with completed remyelination. Similarly, Gf accumulation was seen in CMT rats during early stages with active demyelination at 6 weeks while at chronic stages (9 months) Gf enhancement decreased despite numerous demyelinated axons and onion bulb formation. At all disease stages no signal alterations were seen on T2-w MRI. In conclusion, our data show that the novel MR contrast agent Gf, but not Gadolinium (Gd)-DTPA, facilitates detection of ongoing demyelination by MR neurography independent from the underlying pathology. It appears that the extent of Gf enhancement depends on the acuity of demyelination and is probably related to a transient disturbance of the blood-nerve barrier. Clinical development of Gf may help to further improve the sensitivity of nerve lesion assessment by MRI in patients with peripheral neuropathies.

Charcot-Marie-Tooth (CMT) disease denotes a large group of genetically heterogeneous hereditary motor and sensory neuropathies and ranks among the most common inherited neurological disorders. Mutations in the Myotubularin-Related Protein-2 (MTMR2) or MTMR13/Set-Binding Factor-2 (SBF2) genes are associated with the autosomal recessive disease subtypes CMT4B1 or CMT4B2. Both forms of CMT share similar features including a demyelinating neuropathy associated with reduced nerve conduction velocity (NCV) and focally folded myelin. Consistent with a common disease mechanism, the homodimeric MTMR2 acts as a phosphoinositide D3-phosphatase with phosphatidylinositol (PtdIns) 3-phosphate and PtdIns 3,5-bisphosphate as substrates while MTMR13/SBF2 is catalytically inactive but can form a tetrameric complex with MTMR2, resulting in a strong increase of the enzymatic activity of complexed MTMR2. To prove that MTMR13/SBF2 is the disease-causing gene in CMT4B2 and to provide a suitable animal model, we have generated Mtmr13/Sbf2-deficient mice. These animals reproduced myelin outfoldings and infoldings in motor and sensory peripheral nerves as the pathological hallmarks of CMT4B2, concomitant with decreased motor performance. The number and complexity of myelin misfoldings increased with age, associated with axonal degeneration, and decreased compound motor action potential amplitude. Prolonged F-wave latency indicated a mild NCV impairment. Loss of Mtmr13/Sbf2 did not affect the levels of its binding partner Mtmr2 and the Mtmr2-binding Dlg1/Sap97 in peripheral nerves. Mice deficient in Mtmr13/Sbf2 together with known Mtmr2-deficient animals will be of major value to unravel the disease mechanism in CMT4B and to elucidate the critical functions of protein complexes that are involved in phosphoinositide-controlled processes in peripheral nerves.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by the deficiency of arylsulfatase A (ASA). This results in accumulation of sulfated glycosphingolipids, mainly 3-O-sulfogalactosylceramide (sulfatide), in the nervous system and various other organs. In patients, lipid storage causes a progressive loss of myelin leading to various neurological symptoms. The sulfatide storage pattern in ASA-deficient [ASA(-/-)] mice is comparable to humans, but regrettably, the mice do not mimic the myelin pathology. We reasoned that increasing sulfatide storage in this animal model might provoke demyelination. Therefore, we generated transgenic ASA(-/-) [tg/ASA(-/-)] mice overexpressing the sulfatide-synthesizing enzyme galactose-3-O-sulfotransferase-1 in myelinating cells. Indeed, these tg/ASA(-/-) mice displayed a significant increase in sulfatide storage in brain and peripheral nerves. Mice older than 1 year developed severe neurological symptoms. Nerve conduction velocity was significantly reduced in tg/ASA(-/-) mice because of a peripheral neuropathy characterized by hypomyelinated and demyelinated axons. Inhomogeneous myelin thickness in the corpus callosum, increased frequency of hypomyelinated and demyelinated axons in corpus callosum and optic nerve, and substantially reduced myelin basic protein levels are in accordance with loss of myelin in the CNS. Thus, increasing sulfatide storage in ASA(-/-) mice leads to neurological symptoms and morphological alterations that are reminiscent of human MLD. The approach described here may also be applicable to improve other mouse models of lysosomal as well as nonlysosomal disorders.

Magnetic resonance imaging (MRI) allows assessment of axonal nerve lesions, but detection of focal demyelination is still difficult. We have recently shown that the novel micellar magnetic resonance (MR) contrast agent gadofluorine M (Gf) accumulates in nerve fibers undergoing Wallerian degeneration. In the present study, we report on the in vivo visualization of focal demyelination induced by lysolecithin. Upon appropriate intraneural injection, lysolecithin focally dissolves myelin sheaths with sparing of axons. Conventional unenhanced and gadolinium-DTPA enhanced T1-w MRI did not show signal alterations or contrast enhancement. In contrast, application of Gf led to bright contrast enhancement on T1-w images at the site of focal demyelination, but spared distal nerve segments not affected by demyelination. Gf enhancement persisted until remyelination had occurred. Our study shows that areas of focal nerve demyelination can be detected in vivo by Gf-enhanced MRI. This finding opens up a broad spectrum of applications in experimental neurology, and, depending on further clinical development of Gf, may aid in the diagnostic work up of patients with patchy, multifocal demyelinative disorders in the future.

We report a patient with an extensive paranasal sinus carcinoma. One year after tumor resection, magnetic resonance imaging (MRI) showed swelling of the ipsilateral masticatory muscles with signal increase on T2-weighted images and gadolinium-DTPA uptake, suggestive of local tumor infiltration. However, electromyography, biopsy, and follow-up MRI confirmed denervation pseudohypertrophy of the muscles innervated by the mandibular nerve and excluded tumor recurrence. Muscle denervation and pseudohypertrophy should be considered in the differential diagnosis of appropriate patients with suspected tumor recurrence.

Using newly generated transgenic mice in which the coding region of the connexin29 (Cx29) gene was replaced by the lacZ reporter gene, we confirmed previous immunochemical results that Cx29 is expressed in Schwann cells, oligodendrocytes and Bergmann glia cells. In addition, we detected lacZ/Cx29 in Schwann cells of the sciatic nerve and in particular of the spiral ganglion in the inner ear, as well as at low abundance in the stria vascularis. Furthermore, we found lacZ/Cx29 expression in nonmyelinating Schwann cells of the adrenal gland, in chondrocytes of intervertebral discs and the epiphysis of developing bones. Electron microscopic analyses of myelin sheaths in the central and peripheral nervous system of Cx29-deficient mice detected no abnormalities. The nerve conduction in the sciatic nerve of adult Cx29-deficient mice and the auditory brain stem response as well as visually evoked potentials in 4- to 10-week-old Cx29-deficient mice were not different from wild-type littermate controls. Thus, in contrast to connexin32 and connexin47, which are also expressed in myelinating cells, Cx29 does not contribute to the function of myelin in adult mice.

Mouse mutants heterozygously deficient for the myelin component P0 mimic some forms of inherited neuropathies in humans. We have previously shown that both T lymphocytes and macrophages contribute to the demyelinating neuropathy. Both cell types appear to influence each other mutually, i.e., impaired T lymphocyte development in RAG-1-deficient P0 mutants leads to decreased macrophage numbers and retarded macrophage activation causes reduced T lymphocyte numbers in the peripheral nerves of P0(+/-) mice. In the present study, we investigated the possible role of the macrophage-restricted sialic acid-binding Ig-like lectin sialoadhesin (Sn, Siglec-1) in the pathogenesis of inherited demyelination in P0(+/-) mice. We found that most peripheral nerve macrophages express Sn in the mutants. Myelin mutants devoid of Sn show reduced numbers of CD8+ T lymphocytes and macrophages in peripheral nerves and less severe demyelination, resulting in improved nerve conduction properties. Our findings are potentially important in the development of future treatment strategies for inherited demyelinating neuropathies.

Experimental autoimmune neuritis (EAN) represents an animal model of acute inflammatory nerve injury mirroring pathophysiological aspects of the human Guillain-Barré syndrome. In the present study, we for the first time visualized the spatiotemporal evolution of autoimmune nerve injury and recovery by magnetic resonance imaging (MRI) by use of the novel micellar magnetic resonance (MR) contrast agent gadofluorine M (Gf). EAN was induced in Lewis rats by T-cell transfer (AT-EAN) leading to severe axonal damage, and Gf was applied intravenously at various disease stages mostly 24 h before MRI. In naive rats, Gf enhancement was present solely in the vascular compartment. In AT-EAN, clinically asymptomatic rats already showed consistent Gf uptake in spinal nerves on day 3, while sciatic nerves were spared. The cauda equina correspondingly exhibited massive T-cell infiltration. Gf enhancement further extended to the plexus lumbosacralis on day 4. On days 5 and 6, the entire peripheral neuraxis from the cauda equina, along the sciatic down to the tibial and peroneal nerves, showed strong Gf enhancement. Spinal and peripheral nerves now exhibited massive inflammation and axonal injury on parallel histological analysis. Gf enhancement persisted in the afflicted nerves until complete recovery and disappeared with a proximodistal gradient. In conclusion, Gf-enhanced MR neurography opens a new avenue for monitoring nerve damage in-vivo during an immune attack.

Charcot-Marie-Tooth disease (CMT) comprises a family of clinically and genetically very heterogeneous hereditary peripheral neuropathies and is one of the most common inherited neurological disorders. We have generated a mouse model for CMT type 4B1 using embryonic stem cell technology. To this end, we introduced a stop codon into the Mtmr2 locus within exon 9, at the position encoding amino acid 276 of the MTMR2 protein (E276X). Concomitantly, we have deleted the chromosomal region immediately downstream of the stop codon up to within exon 13. The resulting allele closely mimics the mutation found in a Saudi Arabian CMT4B1 patient. Animals homozygous for the mutation showed various degrees of complex myelin infoldings and outfoldings exclusively in peripheral nerves, in agreement with CMT4B1 genetics and pathology. Mainly, paranodal regions of the myelin sheath were affected, with a high degree of quantitative and qualitative variability between individuals. This pathology was progressive with age, and axonal damage was occasionally observed. Distal nerve regions were more affected than proximal parts, in line with the distribution in CMT. However, we found no significant electrophysiological changes, even in aged (16-month-old) mice, suggesting that myelin infoldings and outfoldings per se are not invariably associated with detectable electrophysiological abnormalities. Our animal model provides a basis for future detailed molecular and cellular studies on the underlying disease mechanisms in CMT4B1. Such an analysis will reveal how the disease develops, in particular, the enigmatic myelin infoldings and outfoldings as well as axonal damage, and provide mechanistic insights that may aid in the development of potential therapeutic approaches.

Charcot-Marie-Tooth neuropathy type 1A (CMT 1 A) is the most common inherited neuropathy in humans and is mostly caused by a 1.5-Mb tandem duplication of chromosome 17 comprising the gene for the peripheral myelin protein 22-kDa (PMP 22). Although there are numerous studies on the functional role of PMP 22, the mechanisms of myelin degeneration under PMP 22-overexpression conditions have not yet been fully understood. We have shown previously that in mouse mutants hetero- or homozygously deficient for two other myelin components, P0 and C x 32, respectively, immune cells contribute to the demyelinating neuropathy. To test this possibility for PMP 22 overexpression, we investigated a putative mouse model for CMT 1 A, i.e., the mouse strain C 6 1 mildly overexpressing human PMP 22 in peripheral nerves. Electron microscopic and electrophysiologic investigations revealed that this mouse strain develops pathologic features similar to those found in CMT 1 A patients. A novel finding, however, was the upregulation of CD8- and F4/80-positive lymphocytes and macrophages, respectively, in peripheral nerves. The observation that macrophages enter endoneurial tubes of the mutants and obviously phagocytose morphologically normal myelin strongly suggests that the myelin degeneration is mediated at least partially by these phagocytic cells. By gene array technology and quantitative RT-PCR of peripheral nerve homogenates from PMP 22 mutants, monocyte chemoattractant protein-1 (MCP-1; cc l2) could be identified as a putative factor to attract or activate macrophages that attack myelin sheaths in this model of CMT 1 A., ((c) 2005 Wiley-Liss, Inc.)

A deficiency of arylsulfatase A (ASA) causes the lysosomal storage disease metachromatic leukodystrophy, which is characterized by accumulation of the sphingolipid 3-O-sulfogalactosylceramide (sulfatide). Sphingolipid storage results in progressive demyelination and severe neurologic symptoms. The disease is lethal, and curative therapy is not available. To assess the therapeutic potential of enzyme replacement therapy (ERT), ASA knockout mice were treated by intravenous injection of recombinant human ASA. Plasma levels of ASA declined with a half-time of approximately 40 min, and enzyme was detectable in tissues within minutes after injection. The uptake of injected enzyme was high into liver, moderate into peripheral nervous system (PNS) and kidney and very low into brain. The apparent half-life of endocytosed enzyme was approximately 4 days. A single injection led to a time- and dose-dependent decline of the excess sulfatide in PNS and kidney by up to 70%, but no reduction was seen in brain. Four weekly injections with 20 mg/kg body weight not only reduced storage in peripheral tissues progressively, but also were surprisingly effective in reducing sulfatide storage in brain and spinal cord. The histopathology of kidney and central nervous system was ameliorated. Improved neuromotor coordination capabilities and normalized peripheral compound motor action potential demonstrate the benefits of ERT on the nervous system function. Enzyme replacement may therefore be a promising therapeutic option in this devastating disease.

Background: Stiff-person syndrome (SPS) with antibodies to amphiphysin is a paraneoplastic disorder of the central nervous system with a putative autoimmune pathogenesis. Proof of a causal role of the antibodies is still lacking for this and all other antibody-associated paraneoplastic syndromes of the central nervous system., Methods: We obtained the plasma filtrate of a patient with breast cancer and SPS that responded to therapeutic plasmapheresis. The purified IgG fraction included high-titre antibodies to the synaptic protein amphiphysin. In a cotransfer design, this IgG fraction was injected intraperitoneally into female Lewis rats that had received encephalitogenic T-helper (Th) lymphocytes specific for myelin basic protein, to induce an immune-mediated leaky blood-brain barrier. The rats were followed up with behavioural tests, video photography, and electromyography., Findings: The injection of the IgG fraction including antibodies to amphiphysin resulted in a dose-dependent stiffness with spasms resembling human SPS. Control IgG injected into rats that had received the same encephalitogenic Th cells had no effect. IgG binding was demonstrated in the central nervous system of rats that showed signs of the disorder., Interpretation: These experiments support the hypothesis of a pathogenetic role of antibodies to amphiphysin, thus adding paraneoplastic SPS to the group of antibody-mediated autoimmune disorders., Relevance to Practice: These findings provide a strong argument for a direct pathogenetic role of anti-amphiphysin in this type of SPS and support therapeutic attempts to eliminate these autoantibodies by plasmapheresis. The experimental approach used could help to elucidate the role of autoantibodies in other paraneoplastic syndromes, such as SPS with antibodies to glutamic acid decarboxylase, and others including anti-Hu-associated subacute cerebellar degeneration and limbic encephalitis.

Nerve injury represents a major cause of disability. In the peripheral nervous system, nerves have the capacity to regrow but within weeks after injury, it is impossible to clarify whether proper regeneration is under way or is failing. In this experimental study, we report on a novel tool to assess nerve outgrowth in vivo. After systemic application, the novel gadolinium-based magnetic resonance (MR) contrast agent Gadofluorine M (Gf) selectively accumulated and persisted in nerve fibers undergoing Wallerian degeneration causing bright contrast on T1-weighted MR images. Gf enhancement on MR imaging was present already at 48 hours within the entire nerve segments undergoing Wallerian degeneration, and subsequently disappeared from proximal to distal parts in parallel to regrowth of nerve fibers. Most importantly, Gf enhancement persisted in nonregenerating, permanently transected nerves. Our novel Gf-based MR imaging methodology holds promise for clinical use to bridge the diagnostic gap between nerve injury and completed nerve regeneration, and to determine the necessity for neurolysis and engraftment if spontaneous regeneration is not successful.

Spinal muscular atrophy with respiratory distress type 1 (SMARD1) is caused by recessive mutations of the IGHMBP2 gene. The role of IGHMBP2 (immunoglobulin mu-binding protein 2) in the pathomechanism of motor neuron disease is unknown. We have generated antibodies against Ighmbp2 and showed that low levels of Ighmbp2 immunoreactivity are present in the nucleus of spinal motor neurons and high levels in cell bodies, axons and growth cones. Ighmbp2 protein levels are strongly reduced in neuromuscular degeneration (nmd) mice, the mouse model of SMARD1. Mutant mice show severe motor neuron degeneration before first clinical symptoms become apparent. The loss of motor neuron cell bodies in lumbar spinal cord is followed by axonal degeneration in corresponding nerves such as the femoral quadriceps and sciatic nerve and loss of axon terminals at motor endplates. Motor neuron degeneration and clinical symptoms then slowly progress until the mice die at the age of 3-4 months. In addition, myopathic changes seem to contribute to muscle weakness and especially to respiratory failure, which is characteristic of the disorder in humans. Cultured motor neurons from embryonic nmd mice did not show any abnormality with respect to survival, axonal growth or growth cone size, thus differing from motor neurons derived from, e.g. Smn (survival motor neuron) deficient mice, the model of spinal muscular atrophy (SMA). Our data suggest that the pathomechanism in SMARD1 is clearly distinct from other motor neuron diseases such as classic SMA.

Acute axonal nerve lesions cause a hyperintense signal on T2-weighted (T2-w) magnetic resonance imaging (MRI) at the nerve lesion site and distal to it. The aim of this experimental study was to investigate the spatiotemporal evolution and resolution of MR nerve signal changes following denervation and reinnervation, and to relate these findings to electrophysiology and histology. The proximal sciatic nerve of adult rats was ligated by a tight suture that was removed 1 week later to induce complete axotomy and nerve regeneration upon release. Serial electromyography (EMG) and motor nerve conduction studies were performed parallel to MRI at multiple points of time. Moreover, sciatic nerves were taken for quantitative histological evaluation. Nerve hyperintensity on T2-w MRI was present distal to the lesion at thigh level 24 h after denervation preceding the occurrence of spontaneous activity on EMG by 24 h. After 48 h, the entire sciatic nerve and its branches showed an increased signal down to the level of the lower leg. The increased nerve signal regressed with a proximo-distal gradient beginning from week 2 after onset of nerve regeneration in the thigh. On EMG, the first reinnervation potentials were detected at that time at the respective level. Compound muscle action potential (CMAP) in the foot muscle fully recovered 12 weeks after onset of nerve regeneration, that is, 2 weeks after resolution of the hyperintensity along the entire nerve on MRI. Histology revealed axonal degeneration in the acute phase and later nerve oedema parallel to the increased nerve signal on MRI. MR signal alterations occur as early as 24 h after an axonal nerve lesion and correlate with nerve fiber degeneration and later with nerve oedema on histology. MR findings in denervation and reinnervation parallel the electrophysiological changes. Thus, MRI is a promising diagnostic tool for the early detection of acute axonal nerve lesions and monitoring of nerve regeneration.

Mutations in the gene of the peripheral myelin protein zero (P0) give rise to the peripheral neuropathies Charcot-Marie-Tooth type 1B disease (CMT1B), Déjérine-Sottas syndrome, and congenital hypomyelinating neuropathy. To investigate the pathomechanisms of a specific point mutation in the P0 gene, we generated two independent transgenic mouse lines expressing the pathogenic CMT1B missense mutation Ile106Leu (P0sub) under the control of the P0 promoter on a wild-type background. Both P0sub-transgenic mouse lines showed shivering and ultrastructural abnormalities including retarded myelination, onion bulb formation, and dysmyelination seen as aberrantly folded myelin sheaths and tomacula in all nerve fibers. Functionally, the mutation leads to dispersed compound muscle action potentials and severely reduced conduction velocities. Our observations support the view that the Ile106Leu mutation acts by a dominant-negative gain of function and that the P0sub-transgenic mouse represents an animal model for a severe, tomaculous form of CMT1B.

A signal increase in denervated muscle on magnetic resonance imaging (MRI) has been described in several clinical and experimental studies. Here, we studied the time course of T2-relaxation time changes in denervation and subsequent reinnervation in a rat model and correlated the findings with electrophysiology and quantitative histology. A prolongation of the T2 relaxation time in muscles was present 48 h after denervation, which was paralleled by spontaneous activity on electromyography (EMG). Histologically, there was a marked enlargement of the capillaries at that time point, indicating increased blood volume. The relaxation time changes peaked 3 weeks after beginning of nerve regeneration identified by EMG. Subsequently, the T2 prolongation normalized until 10 weeks after beginning of regeneration which was associated with a histological regression of the capillary enlargement. MRI closely mirrors the electrophysiological changes following denervation and reinnervation and may thus be used as adjunct to electrophysiology. The pathophysiological basis for the MR relaxation time changes is predominantly the enlargement of the capillary bed.