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Unmyelinated Nerve Fibers (unmyelinated + nerve_fiber)
Selected AbstractsC-fiber (Remak) bundles contain both isolectin B4-binding and calcitonin gene-related peptide-positive axonsTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 4 2005Beth Brianna Murinson Abstract Unmyelinated nerve fibers (Remak bundles) in the rodent sciatic nerve typically contain multiple axons. This study asked whether C-fiber bundles contain axons arising from more than one type of neuron. Most small neurons of the lumbar dorsal root ganglion (DRG) are either glial cell line-derived neurotrophic factor dependent or nerve growth factor dependent, binding either isolectin B4 (IB4) or antibodies to calcitonin gene-related peptide (CGRP), respectively. Injection of IB4-conjugated horseradish peroxidase into a lumbar DRG resulted in intense labeling of IB4 axons, with very low background. Visualized by confocal fluorescence, IB4-binding and CGRP-positive nerve fibers orginating from different DRG neurons came together and remained closely parallel over long distances, suggesting that these two types of axon occupy the same Remak bundle. With double-labeling immunogold electron microscopy (EM), we confirmed that IB4 and CGRP axons were distinct and were found together in single Remak bundles. Previous studies indicate that some DRG neurons express both CGRP and IB4 binding. To ensure that our immunogold results were not a consequence of coexpression, we studied large populations of unmyelinated axons by using quantitative single-label EM. Tetramethylbenzidine, a chromogen with strong intrinsic signal amplification of IB4-horseradish peroxidase, labeled as many as 52% of unmyelinated axons in the dorsal root. Concomitantly, 97% of the Remak bundles with more than one axon contained at least one IB4-labeled axon. Probabilistic modeling using binomial distribution functions rejected the hypothesis that IB4 axons segregate into IB4-specific bundles (P < 0.00001). We conclude that most Remak bundle Schwann cells simultaneously support diverse axon types with different growth factor dependences. J. Comp. Neurol. 484:392,402, 2005. © 2005 Wiley-Liss, Inc. [source] High prevalence of vasomotor reflex impairment in newly diagnosed leprosy patientsEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 10 2005X. Illarramendi Abstract Background, Initial nerve damage in leprosy occurs in small myelinated and unmyelinated nerve fibers. Early detection of leprosy in the peripheral nervous system is challenging as extensive nerve damage may take place before clinical signs of leprosy become apparent. Patients and methods, In order to determine the prevalence of, and factors associated with, peripheral autonomic nerve dysfunction in newly diagnosed leprosy patients, 76 Brazilian patients were evaluated prior to treatment. Skin vasomotor reflex was tested by means of laser Doppler velocimetry. Blood perfusion and reflex vasoconstriction following an inspiratory gasp were registered on the second and fifth fingers. Results, Vasomotor reflex was impaired in at least one finger in 33/76 (43%) patients. The fifth fingers were more frequently impaired and suffered more frequent bilateral alterations than the second fingers. Multivariate regression analysis showed that leprosy reaction (adjusted odds ratio = 8·11, 95% confidence interval: 1·4,48·2) was associated with overall impaired vasomotor reflex (average of the four fingers). In addition, palmar erythrocyanosis and an abnormal upper limb sensory score were associated with vasomotor reflex impairment in the second fingers, whereas anti-phenolic glycolipid-I antibodies, ulnar somatic neuropathy and a low finger skin temperature were associated with impairment in the fifth fingers. Conclusions, A high prevalence of peripheral autonomic dysfunction as measured by laser Doppler velocimetry was observed in newly diagnosed leprosy patients, which is clinically evident late in the disease. Autonomic nerve lesion was more frequent than somatic lesions and was strongly related to the immune-inflammatory reaction against M. leprae. [source] Adjuvant topical therapy with a cannabinoid receptor agonist in facial postherpetic neuralgiaJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 2 2010Ngoc Quan Phan Summary Background: Postherpetic neuralgia is a frequent adverse event in herpes zoster patients and difficult to treat. Conventional analgetic therapy often fails to reduce the burning pain transmitted by unmyelinated nerve fibers. These nerves express cannabinoid receptors which exert a role in modulation of nociceptive symptoms. Therefore, topical therapy with cannabinoid receptor agonist seems likely to suppress local burning pain. Patients and methods: In an open-labeled trial, 8 patients with facial postherpetic neuralgia received a cream containing the cannabinoid receptor agonist N-palmitoylethanolamine. The course of symptoms was scored with the visual analog scale. Results: 5 of 8 patients (62.5 %) experienced a mean pain reduction of 87.8 %. Therapy was tolerated by all patients. No unpleasant sensations or adverse events occurred. Conclusions: Topical cannabinoid receptor agonists are an effective and well-tolerated adjuvant therapy option in postherpetic neuralgia. [source] Opportunities afforded by the study of unmyelinated nerves in skin and other organsMUSCLE AND NERVE, Issue 6 2004William R. Kennedy MS Abstract Neurological practice is mainly focused on signs and symptoms of disorders that involve functions governed by myelinated nerves. Functions controlled by unmyelinated nerve fibers have necessarily remained in the background because of the inability to consistently stain, image, or construct clinically applicable neurophysiological tests of these nerves. The situation has changed with the introduction of immunohistochemical methods and confocal microscopy into clinical medicine, as these provide clear images of thin unmyelinated nerves in most organs. One obvious sign of change is the increasing number of reports from several laboratories of the pathological alterations of cutaneous nerves in skin biopsies from patients with a variety of clinical conditions. This study reviews recent methods to stain and image unmyelinated nerves as well as the use of these methods for diagnosing peripheral neuropathy, for experimental studies of denervation and reinnervation in human subjects, and for demonstrating the vast array of unmyelinated nerves in internal organs. The new ability to examine the great variety of nerves in different organs opens opportunities and creates challenges and responsibilities for neurologists and neuroscientists. Muscle Nerve 756,767, 2004 [source] Sensory nerve conduction deficit in experimental monoclonal gammopathy of undetermined significance (MGUS) neuropathyMUSCLE AND NERVE, Issue 6 2001Michael W. Lawlor BS Abstract An emerging body of evidence from in vitro studies and in vivo animal models supports a pathogenic role of antibodies in the development of peripheral neuropathy associated with monoclonal gammopathy of undetermined significance (MGUS). Although the assessment of motor and sensory nerve fiber function is of clinical importance, it is seldom applied experimentally. We describe the application of an electrophysiologic method for the evaluation of motor and sensory nerve fiber function using an experimental model of MGUS neuropathy. Supramaximal stimulation of the tibial nerve elicited an early motor response (M-wave, 1.7 ± 0.1 ms, n = 10) and a late sensory (H-reflex, 7.8 ± 0.1 ms, n = 10) response that was recorded from the hind foot of anesthetized rats. Intraneural injection of serum antibodies from a MGUS patient with sensorimotor polyneuropathy, but not from an age-matched control subject, produced a marked attenuation of the H-reflex (P < 0.01, n = 10) without affecting the M-wave. Light and electron microscopy of affected nerve showed myelinoaxonal degeneration with sparing of the smaller unmyelinated nerve fibers. The combined electrophysiologic and morphologic findings presented in this study are consistent with a selective sensory conduction deficit in MGUS neuropathy. Selective injury of afferent nerve fibers by this patient's serum antibodies may result from reactivity to neural antigens uniquely expressed by sensory neurons. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 809,816, 2001 [source] Treatment-induced diabetic neuropathy: A reversible painful autonomic neuropathyANNALS OF NEUROLOGY, Issue 4 2010Christopher H. Gibbons MD Objective To describe the natural history, clinical, neurophysiological, and histological features, and outcomes of diabetic patients presenting with acute painful neuropathy associated with glycemic control, also referred to as insulin neuritis. Methods Sixteen subjects presenting with acute painful neuropathy had neurological and retinal examinations, laboratory studies, autonomic testing, and pain assessments over 18 months. Eight subjects had skin biopsies for evaluation of intraepidermal nerve fiber density. Results All subjects developed severe pain within 8 weeks of intensive glucose control. There was a high prevalence of autonomic cardiovascular, gastrointestinal, genitourinary, and sudomotor symptoms in all subjects. Orthostatic hypotension and parasympathetic dysfunction were seen in 69% of subjects. Retinopathy worsened in all subjects. Reduced intraepidermal nerve fiber density (IENFD) was seen in all tested subjects. After 18 months of glycemic control, there were substantial improvements in pain, autonomic symptoms, autonomic test results, and IENFD. Greater improvements were seen after 18 months in type 1 versus type 2 diabetic subjects in autonomic symptoms (cardiovascular p < 0.01; gastrointestinal p < 0.01; genitourinary p < 0.01) and autonomic function tests (p < 0.01, sympathetic and parasympathetic function tests). Interpretation Treatment-induced neuropathy is characterized by acute, severe pain, peripheral nerve degeneration, and autonomic dysfunction after intensive glycemic control. The neuropathy occurred in parallel with worsening diabetic retinopathy, suggesting a common underlying pathophysiological mechanism. Clinical features and objective measures of small myelinated and unmyelinated nerve fibers can improve in these diabetic patients despite a prolonged history of poor glucose control, with greater improvement seen in patients with type 1 diabetes. ANN NEUROL 2010;67:534,541 [source] Long-term course and mutational spectrum of spatacsin -linked spastic paraplegiaANNALS OF NEUROLOGY, Issue 6 2007Ute Hehr MD Objective Hereditary spastic paraplegias (HSPs) comprise a heterogeneous group of neurodegenerative disorders resulting in progressive spasticity of the lower limbs. One form of autosomal recessive hereditary spastic paraplegia (ARHSP) with thin corpus callosum (TCC) was linked to chromosomal region 15q13-21 (SPG11) and associated with mutations in the spatacsin gene. We assessed the long-term course and the mutational spectrum of spatacsin -associated ARHSP with TCC. Methods Neurological examination, cerebral magnetic resonance imaging (MRI), 18fluorodeoxyglucose positron emission tomography (PET), nerve biopsy, linkage and mutation analysis are presented. Results Spastic paraplegia in patients with spatacsin mutations (n = 20) developed during the second decade of life. The Spastic Paraplegia Rating Scale (SPRS) showed severely compromised walking between the second and third decades of life (mean SPRS score, >30). Impaired cognitive function was associated with severe atrophy of the frontoparietal cortex, TCC, and bilateral periventricular white matter lesions. Progressive cortical and thalamic hypometabolism in the 18fluorodeoxyglucose PET was observed. Sural nerve biopsy showed a loss of unmyelinated nerve fibers and accumulation of intraaxonal pleomorphic membranous material. Mutational analysis of spatacsin demonstrated six novel and one previously reported frameshift mutation and two novel nonsense mutations. Furthermore, we report the first two splice mutations to be associated with SPG11. Interpretation We demonstrate that not only frameshift and nonsense mutations but also splice mutations result in SPG11. Mutations are distributed throughout the spatacsin gene and emerge as major cause for ARHSP with TCC associated with severe motor and cognitive impairment. The clinical phenotype and the ultrastructural analysis suggest a disturbed axonal transport of long projecting neurons. Ann Neurol 2007 [source] | ||||||||||