Chronic inflammatory demyelinating polyradiculoneuropathy with cholesterol deposits in a dog

Chronic inflammatory demyelinating polyradiculoneuropathy occurred in an 11-year-old Labrador Retriever dog. Spinal cord compression resulted from massive radiculitis with prominent cholesterol granulomas. Cholesterol deposition and associated granuloma formation is unique in chronic inflammatory demyelinating polyradiculoneuropathy, in both its human and canine expressions.

Ndrg1 in development and maintenance of the myelin sheath

CMT4D disease is a severe autosomal recessive demyelinating neuropathy with extensive axonal loss leading to early disability, caused by mutations in the N-myc downstream regulated gene 1 (NDRG1). NDRG1 is expressed at particularly high levels in the Schwann cell (SC), but its physiological function(s) are unknown. To help with their understanding, we characterise the phenotype of a new mouse model, stretcher (str), with total Ndrg1 deficiency, in comparison with the hypomorphic Ndrg1 knock-out (KO) mouse. While both models display normal initial myelination and a transition to overt pathology between weeks 3 and 5, the markedly more severe str phenotype suggests that even low Ndrg1 expression results in significant phenotype rescue. Neither model replicates fully the features of CMT4D: although axon damage is present, regenerative capacity is unimpaired and the mice do not display the early severe axonal loss typical of the human disease. The widespread large fibre demyelination coincides precisely with the period of rapid growth of the animals and the dramatic (160-500-fold) increase in myelin volume and length in large fibres. This is followed by stabilisation after week 10, while small fibres remain unaffected. Gene expression profiling of str peripheral nerve reveals non-specific secondary changes at weeks 5 and 10 and preliminary data point to normal proteasomal function. Our findings do not support the proposed roles of NDRG1 in growth arrest, terminal differentiation, gene expression regulation and proteasomal degradation. Impaired SC trafficking failing to meet the considerable demands of nerve growth, emerges as the likely pathogenetic mechanism in NDRG1 deficiency.

The use of nerve and muscle biopsy in the diagnosis of vasculitis: a 5 year retrospective study

INTRODUCTION

Peripheral nerve vasculitis is an important condition which can be diagnostically challenging and is one of the principal current indications for nerve and muscle biopsy. Previous studies have suggested that combined nerve and muscle biopsy (usually of the superficial peroneal nerve and peroneus brevis muscle) produces a higher diagnostic yield than nerve biopsy alone in the investigation of vasculitis.

OBJECTIVE

To determine whether in our two centres combined nerve (usually the sural) and muscle (usually the vastus lateralis) biopsy improved diagnostic yield compared with nerve biopsy alone.

METHODS

We interrogated our database of all nerve biopsies (usually of the sural nerve) performed at our institutions over 5 years and identified 53 cases of biopsy proven peripheral nerve vasculitis. Clinicopathological and neurophysiological data in these patients were reviewed.

RESULTS

The most common clinical presentation was with a painful asymmetric axonal polyneuropathy or mononeuritis multiplex (66% of cases). Nerve biopsy demonstrated definite vasculitis in 36%, probable vasculitis in 62% and no vasculitis in 2% of cases. In 24 patients a muscle biopsy (usually the vastus lateralis) was also performed and vasculitis was demonstrated in 46% of these (in 13% showing definite and 33% probable vasculitis). There was only one patient in whom vasculitis was demonstrated in muscle but not in peripheral nerve.

CONCLUSION

Combined nerve (usually sural) and vastus lateralis muscle biopsy did not significantly increase the diagnostic yield compared with nerve biopsy alone. A sensible approach to the diagnosis of peripheral nerve vasculitis is to choose a nerve to biopsy which is clinically affected and amenable to biopsy. If the sural nerve is chosen, the data suggest that it is not routinely worth doing a vastus lateralis biopsy at the same time, whereas if the superficial peroneal nerve is chosen, it seems appropriate to do a combined superficial peroneal nerve and peroneus brevis biopsy. It is still not known if both the sural and superficial peroneal nerves are involved clinically which one gives the higher yield if biopsied.

The phagocytic capacity of neurones

Phagocytosis is defined as the ingestion of particulates over 0.5 microm in diameter and is associated with cells of the immune system such as macrophages or monocytes. Neurones are not generally recognized to be phagocytic. Using light, confocal, time-lapse and electron microscopy, we carried out a wide range of in-vitro and in-vivo experiments to examine the phagocytic capacity of different neuronal cell types. We demonstrated phagocytosis of material by neurones, including cell debris and synthetic particles up to 2.8 microm in diameter. We showed phagocytosis in different neuronal types, and demonstrated that debris can be transported from neurite extremities to cell bodies and persist within neurones. Flow cytometry analysis demonstrated the lack of certain complement receptors on neurones but the presence of others, including integrin receptors known to mediate macrophage phagocytosis, indicating that a restricted set of phagocytosis receptors may mediate this process. Neuronal phagocytosis occurs in vitro and in vivo, and we propose that this is a more widespread and significant process than previously recognized. Neuronal phagocytosis may explain certain inclusions in neurones during disease, cell-to-cell spread of disease, neuronal death during disease progression and provide a potential mechanism for therapeutic intervention through the delivery of particulate drug carriers.

Proteasomal inhibition causes loss of nigral tyrosine hydroxylase neurons

Dysfunction of the ubiquitin-proteasomal system (UPS) has been implicated in the pathogenesis of Parkinson's disease. The systemic administration of UPS inhibitors has been reported to induce nigrostriatal cell death and model Parkinson's disease pathology in rodents. We administered a synthetic, specific UPS inhibitor (PSI) subcutaneously to rats and quantified substantia nigral tyrosine hydroxylase-positive dopaminergic neurons by stereology. PSI caused a 15% decrease in UPS activity at 2 weeks and a 42% reduction in substantia nigra pars compacta tyrosine hydroxylase-positive neurons at 8 weeks. Systemic inhibition of the UPS warrants further evaluation as a means to model Parkinson's disease.

Clinical spectrum of CMT4C disease in patients homozygous for the p.Arg1109X mutation in SH3TC2

We investigated the manifestations of CMT4C disease in a genetically homogeneous group of patients homozygous for the recently identified Gypsy founder mutation p.Arg1109X in SH3TC2. We observed a surprising degree of variation in age at onset, rate of progression, extent and severity of motor and sensory involvement, scoliosis, and cranial nerve involvement, suggesting that the phenotypic spectrum of CMT4C disease is much broader than the classical diagnostic criteria. Phenotype similarity in first degree relatives and increasing heterogeneity in more distantly related subjects point to the involvement of genetic modifiers, possibly variants in the genes encoding protein partners interacting with SH3TC2.

Clinical spectrum of CMT4C disease in patients homozygous for the p.Arg1109X mutation in SH3TC2

We investigated the manifestations of CMT4C disease in a genetically homogeneous group of patients homozygous for the recently identified Gypsy founder mutation p.Arg1109X in SH3TC2. We observed a surprising degree of variation in age at onset, rate of progression, extent and severity of motor and sensory involvement, scoliosis, and cranial nerve involvement, suggesting that the phenotypic spectrum of CMT4C disease is much broader than the classical diagnostic criteria. Phenotype similarity in first degree relatives and increasing heterogeneity in more distantly related subjects point to the involvement of genetic modifiers, possibly variants in the genes encoding protein partners interacting with SH3TC2.

Brachial plexus hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy

We present the clinical, imaging and neuropathological findings in three patients with predominant brachial plexus neuropathy. MR scanning was key to determining the brachial plexus involvement. Biopsy of the brachial plexus was performed in one patient. The appearances of the brachial plexus on MRI, in conjunction with the clinical presentations of these patients, suggest that they are unusual variants within the spectrum of chronic inflammatory demyelinating polyradiculoneuropathy.

High incidence of spontaneous disease in an HLA-DR15 and TCR transgenic multiple sclerosis model

Multiple sclerosis (MS) is thought to involve CD4 T cell recognition of self myelin, many studies focusing on a pathogenic role for anti-myelin, HLA-DR15-restricted T cells. In experimental allergic encephalomyelitis, it is known which epitopes trigger disease and that disease is associated with determinant spread of T cell reactivity. Characterization of these events in human MS is critical for the development of peptide immunotherapies, but it has been difficult to define the role of determinant spread or define which epitopes might be involved. In this study, we report humanized transgenic mice, strongly expressing HLA-DR15 with an MS-derived TCR; even on a RAG-2 wild-type background, mice spontaneously develop paralysis. Disease, involving demyelination and axonal degeneration, correlates with inter- and intramolecular spread of the T cell response to HLA-DR15-restricted epitopes of myelin basic protein, myelin oligodendrocyte glycoprotein, and alphaB-crystallin. Spread is reproducible and progressive, with two of the epitopes commonly described in responses of HLA-DR15 patients. The fact that this pattern is reiterated as a consequence of CNS tissue damage in mice demonstrates the value of the transgenic model in supplying an in vivo disease context for the human responses. This model, encompassing pathologically relevant, spontaneous disease with the presentation of myelin epitopes in the context of HLA-DR15, should offer new insights and predictions about T cell responses during MS as well as a more stringent test bed for immunotherapies.

A case of severe congenital chronic inflammatory demyelinating polyneuropathy with complete spontaneous remission

Chronic inflammatory demyelinating polyneuropathy (CIPD) is characterised by progressive weakness, hyporeflexia and electrophysiological evidence of demyelination with maximal neurological deficit reached after at least 8 weeks progression. CIPD rarely affects children. We present a neonate with clinical features compatible with congenital CIPD. A term male infant of non-consanguineous parents was referred to us at birth with weakness and contractures affecting his legs, suggesting a prenatal onset of immobility. He also had evidence of bulbar dysfunction with poor suck, recurrent aspiration and requiring nasogastric feeding. He had no antigravity movements in the legs, bilateral wrist drop, distal joint contractures and absent deep tendon reflexes. Electromyography showed neurogenic changes, with nerve conduction velocities markedly reduced, increased distal motor latency and dispersed compound muscle action potentials. Cerebrospinal fluid protein was raised. Sural nerve biopsy demonstrated decreased numbers of myelinated fibres and inflammatory cell infiltrates. Muscle biopsy showed denervation. He only received supportive treatment and by 6 months he had fully recovered, and all electrophysiological parameters had normalised.

Sural nerve pathology in diabetic patients with minimal but progressive neuropathy

AIMS/HYPOTHESIS

The early pathological features of human diabetic neuropathy are not clearly defined. Therefore we quantified nerve fibre and microvascular pathology in sural nerve biopsies from diabetic patients with minimal neuropathy.

METHODS

Twelve diabetic patients underwent detailed assessment of neuropathy and fascicular sural nerve biopsy at baseline, with repeat assessment of neuropathy 8.7+/-0.6 years later.

RESULTS

At baseline, neuropathic symptoms, neurological deficits, quantitative sensory testing, cardiac autonomic function and peripheral nerve electrophysiology showed minimal abnormality, which deteriorated at follow-up. Myelinated fibre density, fibre and axonal area, and g-ratio were normal but teased fibre studies showed paranodal abnormalities (p<0.001), segmental demyelination (p<0.01) and remyelination (p<0.01) without axonal degeneration. Unassociated Schwann cell profile density (p<0.04) and unmyelinated axon density (p<0.001) were increased and axon diameter was decreased (p<0.007). Endoneurial capillaries demonstrated basement membrane thickening (p<0.006), endothelial cell hyperplasia (p<0.004) and a reduction in luminal area (p<0.007).

CONCLUSIONS/INTERPRETATION

The early pathological features of human diabetic neuropathy include an abnormality of the myelinated fibre Schwann cell and unmyelinated fibre degeneration with regeneration. These changes are accompanied by a significant endoneurial microangiopathy.

A novel RAB7 mutation associated with ulcero-mutilating neuropathy

There are two known autosomal dominant genes for the hereditary ulcero-mutilating neuropathies: SPTLC1 (hereditary sensory neuropathy type 1) and RAB7 (Charcot-Marie-Tooth disease type 2B). We report a family with autosomal dominant ulcero-mutilating neuropathy, developing in the teens and characterized by ulcers, amputations, sensory involvement in the feet but no motor features. Sequencing the RAB7 gene showed a novel heterozygous A to C mutation, changing asparagine to threonine at codon 161. The mutation is situated adjacent to a previously identified valine to methionine mutation at codon 162, implying a hotspot for mutations in the highly conserved C terminus of RAB7.

Coexistent hereditary and inflammatory neuropathy

Classically, the course of Charcot-Marie-Tooth (CMT) disease is gradually progressive. We describe eight atypical patients who developed acute or subacute deterioration. Seven of these had genetically proven CMT disease type 1A (CMT1A) due to chromosome 17p11.2-12 duplication, and one had X-linked disease (CMTX) due to a mutation in the GJB1 gene. In this group there was sufficient clinical, electrophysiological and neuropathological information to indicate a diagnosis of a superimposed inflammatory polyneuropathy. The age range of the patients was 18-69 years, with a mean of 39 years. A family history of a similar neuropathic condition was present in only four patients. All eight had an acute or subacute deterioration following a long asymptomatic or stable period. Seven had neuropathic pain or prominent positive sensory symptoms. Nerve biopsy demonstrated excess lymphocytic infiltration in all eight patients. Five patients were treated with steroids and/or intravenous immunoglobulin, with variable positive response; three patients received no immunomodulatory treatment. Inflammatory neuropathy has previously been recognized in patients with hereditary neuropathy, with uncharacterized genetic defects and with CMT1B. We present detailed assessments of patients with CMT1A and CMTX, including nerve biopsy, and conclude that coexistent inflammatory neuropathy is not genotype-specific in hereditary motor and sensory neuropathy. Although this was not a formal epidemiological study, estimates of the prevalence of CMT disease and chronic inflammatory demyelinating polyneuropathy indicate that the association is more frequent than would be expected by chance. This has implications for understanding the pathogenesis of inflammatory neuropathies and raises important considerations in the management of patients with hereditary neuropathies. If a patient with CMT disease experiences an acute or subacute deterioration in clinical condition, treatment of a coexistent inflammatory neuropathy with steroids or immunoglobulin should be considered.

Myotubularin-related 2 protein phosphatase and neurofilament light chain protein, both mutated in CMT neuropathies, interact in peripheral nerve

Charcot-Marie-Tooth disease type 4B1, CMT4B1, is a severe, autosomal-recessive, demyelinating peripheral neuropathy, due to mutations in the Myotubularin-related 2 gene, MTMR2. MTMR2 is widely expressed and encodes a phosphatase whose substrates include phosphoinositides. However, this does not explain how MTMR2 mutants specifically produce demyelination in the peripheral nerve. Therefore, we analysed the cellular and subcellular distribution of Mtmr2 in nerve. Mtmr2 was detected in all cytoplasmic compartments of myelin-forming Schwann cells, as well as in the cytoplasm of non-myelin-forming Schwann cells and both sensory and motorneurons. In contrast, Mtmr2 was detected in the nucleus of Schwann cells and motorneurons, but not in the nucleus of sensory neurons. As Mtmr2 is diffusely present also within the nerve, a specific function could derive instead from nerve-specific interacting proteins. Therefore, we performed two yeast two-hybrid screenings, using either fetal brain or peripheral nerve cDNA libraries. The neurofilament light chain protein, NF-L, was identified repeatedly in both screenings, and found to interact with MTMR2 in both Schwann cells and neurons. Interestingly, NF-L, encoding NF-L, is mutated in CMT2E. These data may provide a basis for the nerve-specific pathogenesis of CMT4B1, and further support for the notion that hereditary demyelinating and axonal neuropathies may represent different clinical manifestations of a common pathological mechanism.

Pathological findings in a patient with ventilatory failure and chronic inflammatory demyelinating polyneuropathy

Chronic inflammatory demyelinating polyneuropathy (CIDP) may cause significant disability, but severe respiratory complications are uncommon. We describe the case of a 49-year-old man with clinical features of CIDP for 5 years who died of respiratory failure. Post-mortem findings of denervation in diaphragm muscle and axonal loss in phrenic nerve are presented. Severe ventilatory failure may occur in CIDP when neuropathy affects the respiratory muscles. Attention to early clinical features of respiratory insufficiency may facilitate the prevention of more severe features of respiratory failure.

Peripheral nerve granuloma in a patient with tuberculosis

The cause of peripheral neuropathy associated with tuberculosis is controversial. Possibilities include an immune mediated neuropathy, direct invasion of nerves, vasculitic neuropathy, compressive neuropathy, a meningitic reaction, and the toxic effects of antituberculous chemotherapy. This report describes the unusual finding of granulomas in the peripheral nerve of a patient with tuberculosis. The pathological findings were of a delayed hypersensitivity reaction, but with no more specific indications of the mechanism of the neuropathy.

Peripheral nerve regeneration in galactosaemic rats

The use of galactosaemia as a model for some aspects of diabetic polyneuropathy allows the influence of glycation to be studied independently of other effects. There are well-studied abnormalities of the peripheral nerves in galactosaemic rats, one of which is that the efficiency of regeneration is initially reduced. One possible cause could be that glycated myelin debris in macrophages is less degradable and interferes with macrophage function. Macrophage recognition and ingestion of myelin glycosylated in vitro increases with the duration of incubation in a sugar-rich medium. This study was performed to investigate a possible correlation between galactosaemia and regeneration, together with the role of macrophages. Galactosaemia was induced by adding galactose to the rats' diet for 2 months before injury. Following a crush lesion to the sciatic nerve, regeneration was found to be delayed, demonstrated by a reduction in mean myelinated fibre size and density 1 month after crush, although, 2 and 3 months later, the differences did not reach statistical significance. There were also more macrophages in the galactosaemic rats than in the control animals at all time points. The initial delay in regeneration in galactosaemic rats was therefore only temporary and there was little evidence of long-term deleterious effects. In addition to the morphometric results, immunohistochemistry showed that there were more macrophages in the galactosaemic rats than in the control animals at all time points. Correlating macrophage and myelinated fibre counts suggests that the persistence of debris-containing macrophages does not appear to have a significant inhibitory effect on nerve regeneration. No evidence was found for persistent basal laminal tubes around the regenerating clusters.

YAC transgenic mice carrying pathological alleles of the MJD1 locus exhibit a mild and slowly progressive cerebellar deficit

Machado-Joseph disease (MJD; MIM 109150) is a late-onset neurodegenerative disorder caused by the expansion of a polyglutamine tract within the MJD1 gene. We have previously reported the generation of human yeast artificial chromosome (YAC) constructs encompassing the MJD1 locus into which expanded (CAG)(76) and (CAG)(84) repeat motifs have been introduced by homologous recombination. Transgenic mice containing pathological alleles with polyglutamine tract lengths of 64, 67, 72, 76 and 84 repeats, as well as the wild type with 15 repeats, have now been generated using these YAC constructs. The mice with expanded alleles demonstrate a mild and slowly progressive cerebellar deficit, manifesting as early as 4 weeks of age. As the disease progresses, pelvic elevation becomes markedly flattened, accompanied by hypotonia, and motor and sensory loss. Neuronal intranuclear inclusion (NII) formation and cell loss is prominent in the pontine and dentate nuclei, with variable cell loss in other regions of the cerebellum from 4 weeks of age. Interestingly, peripheral nerve demyelination and axonal loss is detected in symptomatic mice from 26 weeks of age. In contrast, transgenic mice carrying the wild-type (CAG)(15) allele of the MJD1 locus appear completely normal at 20 months. Disease severity increases with the level of expression of the expanded protein and the size of the repeat. These mice are representative of MJD and will be a valuable resource for the detailed analysis of the roles of repeat length, tissue specificity and level of expression in the neurodegenerative processes underlying MJD pathogenesis.

Effects of nonenzymatic glycosylation of extracellular matrix components on cell survival and sensory neurite extension in cell culture

Diabetic sensory polyneuropathy is characterized by a distal axonopathy of dying-back type. It is accompanied by a failure of axonal regeneration, in which nonenzymatic glycosylation (glycation) of the extracellular matrix may be involved. In the present study, the effects of glycation of collagen IV and laminin, major components of basal lamina, on neuron survival and neurite extension were investigated in tissue culture. Fast glycation of laminin was achieved by incubation with glycolaldehyde and glycation of collagen IV by incubation with glucose. The degree of glycation was estimated by fluorescence analysis. Glycated or nonglycated laminin or collagen IV were used as substrates for culture of dorsal root ganglion (DRG) neurons from neonatal rats. Cultures were assessed for the proportion of cells attaching to the substrate, surviving and bearing neurites. Cell attachment and the proportion bearing neurites were significantly reduced on collagen IV glycated for 2 weeks, but survival was only affected by glycation for 4 or 5 weeks. All 3 parameters were significantly reduced on glycated compared with unglycated laminin. Glycation of both laminin and collagen IV produced considerable morphological differences in the cultured neurons on scanning electron microscopy. Dissociated DRG neurons from adult animals with streptozotocin-induced diabetes cultured on nonglycated substrates survived less well and produced fewer neurites. Glycation of collagen IV and laminin thus affects neuronal survival, neurite production and cell morphology, and diabetes affects both the survival of sensory neurons in culture and their ability to extend neurites.

Comparison of a new pmp22 transgenic mouse line with other mouse models and human patients with CMT1A

Charcot-Marie-Tooth disease type 1A is a dominantly inherited demyelinating disorder of the peripheral nervous system. It is most frequently caused by overexpression of peripheral myelin protein 22 (PMP22), but is also caused by point mutations in the PMP22 gene. We describe a new transgenic mouse model (My41) carrying the mouse, rather than the human, pmp22 gene. The My41 strain has a severe phenotype consisting of unstable gait and weakness of the hind limbs that becomes obvious during the first 3 weeks of life. My41 mice have a shortened life span and breed poorly. Pathologically, My41 mice have a demyelinating peripheral neuropathy in which 75% of axons do not have a measurable amount of myelin. We compare the peripheral nerve pathology seen in My41 mice, which carry the mouse pmp22 gene, with previously described transgenic mice over-expressing the human PMP22 protein and Trembler-J (TrJ) mice which have a P16L substitution. We also look at the differences between CMT1A duplication patients, patients with the P16L mutation and their appropriate mouse models.