Deficiency in monocarboxylate transporter 1 (MCT1) in mice delays regeneration of peripheral nerves following sciatic nerve crush.

Peripheral nerve regeneration following injury occurs spontaneously, but many of the processes require metabolic energy. The mechanism of energy supply to axons has not previously been determined. In the central nervous system, monocarboxylate transporter 1 (MCT1), expressed in oligodendroglia, is critical for supplying lactate or other energy metabolites to axons. In the current study, MCT1 is shown to localize within the peripheral nervous system to perineurial cells, dorsal root ganglion neurons, and Schwann cells by MCT1 immunofluorescence in wild-type mice and tdTomato fluorescence in MCT1 BAC reporter mice. To investigate whether MCT1 is necessary for peripheral nerve regeneration, sciatic nerves of MCT1 heterozygous null mice are crushed and peripheral nerve regeneration was quantified electrophysiologically and anatomically. Compound muscle action potential (CMAP) recovery is delayed from a median of 21days in wild-type mice to greater than 38days in MCT1 heterozygote null mice. In fact, half of the MCT1 heterozygote null mice have no recovery of CMAP at 42days, while all of the wild-type mice recovered. In addition, muscle fibers remain 40% more atrophic and neuromuscular junctions 40% more denervated at 42days post-crush in the MCT1 heterozygote null mice than wild-type mice. The delay in nerve regeneration is not only in motor axons, as the number of regenerated axons in the sural sensory nerve of MCT1 heterozygote null mice at 4weeks and tibial mixed sensory and motor nerve at 3weeks is also significantly reduced compared to wild-type mice. This delay in regeneration may be partly due to failed Schwann cell function, as there is reduced early phagocytosis of myelin debris and remyelination of axon segments. These data for the first time demonstrate that MCT1 is critical for regeneration of both sensory and motor axons in mice following sciatic nerve crush.

Scapulalgie et neuropathie sus-scapulaire en pathologie sportive [Scapular pain and supra-scapular neuropathy in sports medicine]

Eight patients with shoulder pain are reported with a history of athletic activities. On examination, performed with a delay of several months, all patients had painful paresis and atrophy of spinati fossa. Electroneuromyography was carried out in all cases and showed a suprascapular nerve axonal loss from the spinati muscles or infraspinatus muscle, signs of denervation-reinnervation in spinati or infraspinatus muscles, normal examination of other scapular girdle muscles, and a coordinate spinati contraction with shoulder displacement excluding rotator cuff tears. All patients had conservative treatment and only two improved. Six patients underwent surgical decompression of the suprascapular nerve; in three, motor function clearly improved, and in three others pain improved. The factors leading to entrapment include stretch mechanisms associated with shoulder movements, leading to suprascapular nerve liability to mechanical lesions. In patients with shoulder pain, the authors recommend an early electrophysiological work-up to recognize an isolated suprascapular neuropathy. The surgical decompression of the nerve should be based on persistent shoulder pain after conservative treatment.

Fetal akinesia in metatropic dysplasia: The combined phenotype of chondrodysplasia and neuropathy?

Dominant mutations in the receptor calcium channel gene TRPV4 have been associated with a family of skeletal dysplasias (metatropic dysplasia, pseudo-Morquio type 2, spondylometaphyseal dysplasia, Kozlowski type, brachyolmia, and familial digital arthropathy) as well as with dominantly inherited neuropathies (hereditary motor and sensory neuropathy 2C, scapuloperoneal spinal muscular atrophy, and congenital distal spinal muscular atrophy). While there is phenotypic overlap between the various members of each group, the two groups were considered to be totally separate with the former being strictly a structural skeletal condition and the latter group being confined to the peripheral nervous system. We report here on fetal akinesia as the presenting feature of severe metatropic dysplasia, suggesting that certain TRPV4 mutations can cause both a skeletal and a neuropathic phenotype. Three cases were detected on prenatal ultrasound because of absent movements in the second trimester. Case 4 presented with multiple joint contractures and absent limb movements at birth and was diagnosed with "fetal akinesia syndrome". Post-interruption and post-natal X-rays showed typical features of metatropic dysplasia in all four. Sequencing of the TRPV4 gene confirmed the presence of de novo heterozygous mutations predicting G78W (Case 1), T740I (Cases 2 and 3), and K276E (Case 4). Although some degree of restriction of movements is not uncommon in fetuses with skeletal dysplasia, akinesia as leading sign is unusual and suggests that certain TRPV4 mutations produce both chondrodysplasia and a peripheral neuropathy resulting in a severe "overlap" phenotype.

Neuropathie optique lors d'un traitement par disulfirame [Optic neuropathy while taking disulfiram]

INTRODUCTION: Disulfiram has been used since the late 1940s to treat chronic alcoholism. This drug interferes with alcohol metabolism resulting in an acetaldehyde increase. This causes painful symptoms, encouraging abstinence. Side effects include rare cases of bilateral optic neuropathies. Visual recovery occurs frequently upon cessation of therapy. METHOD AND OBSERVATION: We retrospectively studied patients referred for visual loss while treated with disulfiram between 1987 and 2005. Fourteen patients (three females, 11 males; aged 35-62 years) complained of visual loss, but a toxic, disulfiram-related, optic neuropathy was diagnosed in only five patients. Following cessation of disulfiram therapy, visual acuity and field improved in all five patients. DISCUSSION: and conclusion: When disulfiram toxicity is suspected with optic neuropathy, cessation of treatment is mandatory. Visual prognosis is good in the majority of cases, as illustrated by our series. Disulfiram toxicity can be diagnosed only after excluding all other possible causes of visual loss.

Novel pathogenic pathways in diabetic neuropathy.

Diabetic peripheral neuropathy (DPN) is a common complication affecting more than one third of diabetes mellitus (DM) patients. Although all cellular components participating in peripheral nerve function are exposed to and affected by the metabolic consequences of DM, nodal regions, areas of intense interactions between Schwann cells and axons, may be particularly sensitive to DM-induced alterations. Nodes are enriched in insulin receptors, glucose transporters, Na(+) and K(+) channels, and mitochondria, all implicated in the development and progression of DPN. Latest results particularly reinforce the idea that changes in ion-channel function and energy metabolism, both of which depend on axon-glia crosstalk, are among the important contributors to DPN. These insights provide a basis for new therapeutic approaches aimed at delaying or reversing DPN.

A hypomorphic mutation in lpin1 induces progressively improving peripheral neuropathy in the rat

The Lpin1 gene encodes the phosphatidate phosphatase (PAP1) enzyme Lipin 1, which plays a critical role in lipid metabolism. In this study we describe the identification and characterization of a rat with a mutated Lpin1 gene (Lpin11Hubr ), generated by N-ethyl-N-nitrosourea mutagenesis. Lpin11Hubr rats are characterized by hindlimb paralysis that is detectable from the second postnatal week. Sequencing of Lpin1 identified a missense mutation in the 5'-end splice site of exon 18 resulting in mis-splicing, a reading frame shift and a premature stop codon. As this mutation does not induce nonsense-mediated decay, it allows the production of a truncated Lipin 1 protein lacking PAP1 activity. As a consequence, Lpin11Hubr rats develop hypomyelination rather than the pronounced demyelination defect characteristic of Lpin1fld/fld mice, which carry a null allele for Lpin1. Furthermore, histological and molecular analyses revealed that this lesion improve in older Lpin11Hubr rats as compared to young Lpin11Hubr rats and Lpin1fld/fld mice. The observed differences between the murine Lpin1fld/fld mutant, with a complete loss of Lipin 1 function, and the Lpin1Hubr rat, with a truncated PAP1 activitydeficient form of Lipin 1, provide additional evidence for suggested non-enzymatic Lipin1 function residing outside of its PAP1 domain. While we are cautious in making a direct parallel between the presented rodent model and human disease, our data may provide new insight into pathogenicity of recently identified human Lpin1 mutations. *These authors contributed equally.

Bilateral anterior ischemic optic neuropathy following influenza vaccination.

Optic neuritis is an occasional complication of vaccination. Visual loss can be unilateral or bilateral, and most patients recover substantially without treatment. The presumptive mechanism is an immune-mediated demyelinating injury of the optic nerve. We report two patients who had permanent visual loss following influenza vaccination. Their pattern of visual loss, segmental optic disc changes, and failure of visual recovery were atypical for demyelinating optic neuritis and reminiscent of a primary ischemic injury to the optic nerve. We speculate that an immune complex-mediated vasculopathy following vaccination can cause anterior ischemic optic neuropathy. Clinicians should be aware of this entity because of the less favorable prognosis for visual recovery in these cases.

Clinical and electrophysiological recovery in Leber hereditary optic neuropathy with G3460A mutation.

To report a case of clinical and electrophysiological recovery in Leber hereditary optic neuropathy (LHON) with G3460A Mutation. A 10-year-old boy with a three-month history of painless bilateral sequential visual loss upon presentation underwent visual acuity (diminished), anterior and posterior segment examination (normal), fluorescein angiography (normal), Goldman kinetic perimetry (bilateral central scotomata), genetic (a point G3460A mutation) and electrophysiological investigation (undetectable pattern visual evoked potentials (VEP); low amplitude, broadened and reduced flash VEPs and loss of the N95 component in the pattern electroretinograms). Diagnosis of LHON was made. Eighteen months later vision and electrophysiological tests results began spontaneously improving. Kinetic perimetry revealed reduced density and size of scotomata. Two years later, there had been further electrophysiological improvement. This report describes both clinical and electrophysiological improvement in LHON with G3460A mutation.

Clinical spectrum of tuberculous optic neuropathy.

PURPOSE: Tuberculous optic neuropathy may follow infection with Mycobacterium tuberculosis or administration of the bacille Calmette-Guerin. However, this condition is not well described in the ophthalmic literature. METHODS: Ophthalmologists, identified through professional electronic networks or previous publications, collected standardized clinical data relating to 62 eyes of 49 patients who they had managed with tuberculous optic neuropathy. RESULTS: Tuberculous optic neuropathy was most commonly manifested as papillitis (51.6 %), neuroretinitis (14.5 %), and optic nerve tubercle (11.3 %). Uveitis was an additional ocular morbidity in 88.7 % of eyes. In 36.7 % of patients, extraocular tuberculosis was present. The majority of patients (69.4 %) had resided in and/or traveled to an endemic area. Although initial visual acuity was 20/50 or worse in 62.9 % of 62 eyes, 76.7 % of 60 eyes followed for a median of 12 months achieved visual acuities of 20/40 or better. Visual field defects were reported for 46.8 % of eyes, but these defects recovered in 63.2 % of 19 eyes with follow-up. CONCLUSION: Visual recovery from tuberculous optic neuropathy is common, if the diagnosis is recognized and appropriate treatment is instituted. A tuberculous etiology should be considered when evaluating optic neuropathy in persons from endemic areas.

Changes in nuclear 3,5,3'-triiodothyronine receptor expression in rat dorsal root ganglia and sciatic nerve during development: comparison with regeneration.

The action of the thyroid hormones on responsive cells in the peripheral nervous system requires the presence of nuclear triiodothyronine receptors (NT3R). These nuclear receptors, including both the alpha and beta subtypes of NT3R, were visualized by immunocytochemistry with the specific 2B3 monoclonal antibody. In the dorsal root ganglia (DRG) of rat embryos, NT3R immunoreactivity was first discretely revealed in a few neurons at embryonic day 14 (E14), then strongly expressed by all neurons at E17 and during the first postnatal week; all DRG neurons continued to possess clear NT3R immunostaining, which faded slightly with age. The peripheral glial cells in the DRG displayed a short-lived NT3R immunoreaction, starting at E17 and disappearing from the satellite and Schwann cells by postnatal days 3 and 7 respectively. In the developing sciatic nerve, Schwann cells also exhibited transient NT3R immunoreactivity restricted to a short period ranging from E17 to postnatal day 10; the NT3R immunostaining of the Schwann cells vanished proximodistally along the sciatic nerve, so that the Schwann cells rapidly became free of detectable NT3R immunostaining. However, after the transection or crushing of an adult sciatic nerve, the NT3R immunoreactivity reappeared in the Schwann cells adjacent to the lesion by 2 days, then along the distal segment in which the axons were degenerating, and finally disappeared by 45 days, when the regenerating axons were allowed to re-occupy the distal segment.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic pitfalls: posterior ischemic optic neuropathy mimicking optic neuritis.

In young people, the most frequent cause of isolated monocular visual loss due to an optic neuropathy is optic neuritis. We present the case of a 27 year old woman who presented monocular visual loss, excruciating orbital pain and unusual temporal headache. The initial diagnosis of optic neuritis revealed later to be a posterior ischemic optic neuropathy (PION). In this case, PION was the first unique presentation of a non-traumatic carotid dissection, and it was followed 24h later by an ischemic stroke. Sudden monocular visual loss associated with a new-onset headache are clinical symptoms that should immediately prompt to a carotid dissection.

Outcomes of optic nerve sheath decompression for nonarteritic ischemic optic neuropathy.

Efficacy of optic nerve sheath decompression (ONSD) in treating non-arteritic ischemic optic neuropathy (NAION) is not clear. We retrospectively analyzed the records of 91 patients with NAION, who were examined during a two-year period, and compared the final Snellen visual acuities of eyes treated with ONSD with those of eyes that did not have surgery. Seven of 18 eyes with ONSD (39%) demonstrated increased visual acuity of two or more lines; whereas 23 of 71 eyes without surgery (32%) had increased acuity. The ONSD group and no surgery group were further subdivided into eyes with progressive visual loss and nonprogressive visual loss. No statistically significant differences in visual outcome between groups were found. We did not find the high frequency of visual improvement that has been reported in some studies of ONSD for NAION.