Dopamine and its metabolites in human peripheral nerves: is there a widely distributed system of peripheral dopaminergic nerves?
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3,4-Dihydroxyphenylacetic Acid↗
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Cold storage of peripheral nerves: an in vitro assay of cell viability and function.
The development of a nerve bank as a source of donor material to repair large defects in peripheral nerve injuries requires an understanding of the influence of cold storage on cell viability and function in these potential nerve grafts. Segments of peripheral nerves from both human and rat were stored in University of Wisconsin Cold Storage Solution (UW) at 4 degrees C for < 12 h, 3 days, and 1, 2, or 3 weeks. Cellular viability was initially assessed by the degree of cellular outgrowth from explants of the stored nerves placed in culture, and then further quantitated by dissociating the cultured nerve explants and calculating the type and number of cells per milligram of peripheral nerve. Rat Schwann cells (SCs) obtained from the stored (control and 1 and 2 weeks) nerves were tested for their functional ability to myelinate dorsal root ganglion (DRG) neurons in culture. Our findings indicate that human and rat peripheral nerves contain few viable SCs and fibroblasts after 3 weeks of cold storage with the quantity of viable cells within the human cold stored peripheral nerves decreasing significantly after 1 week of cold storage. Despite their reduced number, some SCs from rat nerves stored up to 2 weeks are capable of myelinating DRG axons in culture. These results suggest that short intervals (< 1 week) of cold storage will result in potential peripheral nerve grafts containing large populations of functional cells, while long-term (> or = 3 weeks) cold stored peripheral nerves will contain few viable cells.
Animals↗
Differential atrophy of sensory and motor fibers following section of cat peripheral nerves.
Differential effects of peripheral nerve section on myelinated sensory and motor fiber populations were investigated in 5 hindlimb nerves of cats. Upon electrical stimulation of each nerve, monophasic compound action potentials were recorded from the L6, L7 and S1 dorsal and ventral roots, and the impedance of each root was measured. The decline in the electrical charge computed from potentials 43 to 252 days after nerve section gave a measure of the effect of axotomy on the diameters of sensory and of motor fibers in each nerve. No significant difference in the rate of atrophy of sensory and motor fibers was observed after about 45 days following nerve section. After about 145 and 245 days, however, dorsal root charge contributions had decreased significantly more than ventral root values. Exponential decay curves were fitted separately to charge data for sensory and for motor fibers. The calculated value for the endpoint of the decay was about 35% of the control value for motor fibers, and not significantly different from zero to sensory fibers. These results suggest that in response to axotomy, myelinated motor fiber diameters decline at first but later stabilize, while myelinated sensory fibers continue to decline and may atrophy completely if regeneration is prevented. Possible roles of electrical activity and of 'trophic' interactions with the periphery in the maintenance of cell properties are discussed.
Animals↗
Factors influencing nerve repair. I. Blood supply of peripheral nerves.
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Humans↗
Experience with homologous lyophilised nerve grafts in the treatment of peripheral nerve injuries.
Report of a series of 18 late secondary nerve grafts using lyophilised (disantigenised and disenzymatised) homografts of the Braun Melsungen Company. In contrast to the publication of Kuhlendahl et al. (1972) 32% of the cases showed definitive signs of regeneration. Therefore, in spite of the fact that autografts give better results, further research into the possibilities of homografts seems desirable. Their potential usefulness obviously is restricted to cases in which from any reasons autologous nerve grafts are not available.
Adolescent↗
Neuropathic pain and injured nerve: peripheral mechanisms.
Injury to sensory axons often has the paradoxical effect of inducing positive sensory disturbances; paraesthesias and chronic neuropathic pain. Such symptoms can be at least partially understood in terms of pathophysiological changes that occur in the electrical excitability of the injured sensory neuron. These changes result in the generation of an abnormal ongoing and evoked discharge, originating, alternatively, at various ectopic neural pacemaker sites. Many of the most effective therapeutic modalities recommended for neuropathic pain act by reducing this ectopic neural discharge.
Chronic Disease↗
[Effect of histologic classification on surgical treatment of peripheral nerve tumors].
The influence of histological classification on the options of the peripheral nerve tumors surgery Peripheral nerve sheath tumors (PNST) constitute significant part of all tumors of peripheral nerves. In 1998-2000 years we have operated 7 such patients--3 females, 4 males in our department. The definite diagnosis was made by histology. Total removal was performed in all patients. The nerve continuity was preserved in 4 cases (3x neurofibroma, 1x schwannoma) and nerve had to be disconnected in 3 cases (1x neurobibroma, 1x plexiform neurofibroma as a part of von Recklinghausen disease (VRD), 1x malignant schwannoma). Good neurological outcome was in patients with preserved nerve continuity. Out of 3 patients with the need of nerve disconnection, graft and complete reinervation was performed in case of benign neurofibroma, but in the patient with von Recklinghausen disease and in the patient with malignant schwannoma the permanent leasion of nerve remained. We can conclude that histological classification directly predetermine the options of the peripheral nerve tumors surgery.
Adult↗
The expression, origin and function of tenascin during peripheral nerve formation in the chick.
During development of the peripheral nervous system, the extracellular matrix molecule tenascin has been found to be closely associated with growing axons. However, its origin and function in peripheral nerve formation are far from clear. In this study, we examined the expression of tenascin during outgrowth of sensory, motor and sympathetic preganglionic axons, and assessed its origin and function in peripheral nerve formation. During outgrowth of sensory and motor axons, a high concentration of tenascin and its mRNA was found to surround sensory and motor axons in the newly formed spinal nerves. The source of this tenascin was examined through a series of surgical manipulations. Neural crest removals did not alter the distribution of tenascin protein or its mRNA surrounding the spinal nerves. Transplantation of quail somites into chick embryos showed that, similar to the distribution of tenascin, there is a high concentration of somitic cells surrounding the spinal nerves. Moreover, somite removals resulted in a reduction of the tenascin and tenascin mRNA surrounding the spinal nerves. Taken together, these results suggest that the majority of the tenascin surrounding the spinal nerves is of somitic origin. Possible functions of tenascin associated with peripheral nerve formation were examined through injections of tenascin or its antiserum into individual somites prior to or during axon outgrowth. Injections of tenascin or its antiserum did not alter the trajectory of peripheral axons in the anterior half of the somite, nor produce gross abnormalities in the morphology of peripheral nerves, suggesting that tenascin does not play a crucial role in the early formation of peripheral nerves.
Animals↗
Changes in the axonal membrane potential and Ca2+ concentration associated with peripheral nerve grafting after spinal cord injury.
We performed peripheral nerve allografting in rats with spinal cord injury, and measured motor function and axonal membrane potential as well as Ca(2+) concentration of the nerve grafting spinal cord area by using a behavior observation system and a confocal laser-scanning microscope, respectively. In our experiments, we produced a model of peripheral nerve grafting after spinal cord injury by peripheral nerve allografting (sciatic nerve) in rats with spinal cord injury (thoracic cord hemisection). The group with spinal cord injury that underwent peripheral nerve grafting showed improvement in motor function, a significant increase in the axonal action potential, and a slight increase in the Ca(2+) concentration compared with the group that did not undergo nerve grafting.
Animals↗
Imaging of peripheral nerve lesions.
PURPOSE OF REVIEW: Clinical investigations of peripheral nerve lesions routinely involve nerve conduction studies and electromyography. Imaging studies are often used to exclude focal mass lesions or external compression and to visualize muscle atrophy. More recently, it has been recognized that magnetic resonance imaging can identify changes in peripheral nerves and secondary neurogenic alterations in skeletal muscle, which may significantly enhance its use in the differential diagnosis of peripheral nerve disease. RECENT FINDINGS: Acute axonal nerve lesions cause a hyperintense signal on T2-weighted images at and distal to the lesion site, which correlates with Wallerian degeneration and nerve oedema. Superparamagnetic iron oxide particles provide an exciting new tool to detect the invasion of macrophages into the degenerating nerve distal to an axonal lesion. Prolongation of the T2 relaxation time and gadolinium enhancement of denervated muscle develop in parallel to the development of spontaneous activity on electromyography, and are probably the consequence of capillary enlargement and increased muscular blood volume. SUMMARY: Magnetic resonance imaging supplements the differential diagnosis of peripheral nerve disease. An advantage over clinical neurophysiological investigations is that it is operator independent and painless. It can identify axonal damage and may thus help to identify a lesion site precisely, where fractionated nerve conduction studies are not applicable. Novel contrast media may potentially be used to detect pathophysiologically relevant mechanisms such as infiltration of the nerve by macrophages. Magnetic resonance imaging also has the advantage of providing a lasting detailed topographical picture of regional variations and avoids localization errors of muscles in electromyography.
Humans↗
[Pictorial essay: Ultrasound of tumours and tumour-like lesions of peripheral nerves].
High-resolution ultrasound is an excellent diagnostic modality for visualising peripheral nerves and differentiate tumours of the peripheral nerve. With high-frequency transducers (5-15 MHz), peripheral nerves can be visualised, the hypoechoic nerve fascicles, the surrounding tissue and tumourous lesions including the relation to their nerve of origin can be evaluated. By using colour Doppler sonography (CDS), it is possible to detect and assess vascularisation of tumours of the nerve. We present sonographic features of common and uncommon benign and malignant tumours of the peripheral nerve.
Adult↗
Ultrasonography of peripheral nerves.
During sonographic examination of the extremities using high frequency "small-parts" equipment, peripheral nerves may be identified in virtually all patients. Peripheral nerves have a typical ultrasonographic pattern that correlates well with histologic structure and facilitates differentiation between nerves and tendons. The ability of this technique to depict peripheral nerves makes it possible, in many instances, to study nerve abnormalities in trauma, entrapment syndromes and tumors. Ultrasound can enable differentiation of an endoneural from an extraneural space-occupying lesion and evaluation of the extent and consistency of the lesion, as well as the integrity and dynamic behavior of the nerve involved at follow-up study. The purpose of this review article is to describe the normal ultrasonographic appearance of peripheral nerves and to discuss the potential role of this technique to image nerve lesions noninvasively. A series of paradigmatic ultrasound images of diverse pathologic processes involving peripheral nerves is presented. Although the ultrasound study of peripheral nerves remains in its infancy, with further refinement of ultrasound technology and a more precise knowledge of the ultrasound appearance of the extremities we may be optimistic to the future impact of this technique on diagnosis, treatment and prognosis in patients clinically suspected to have a nerve lesion.
Humans↗
Peripheral nerve regeneration: an opinion on channels, scaffolds and anisotropy.
Peripheral nerve regeneration presents a significant clinical challenge and the current state of the art using autografts to repair long peripheral nerve gaps is unsatisfactory. In this manuscript, the analytical framework that determines the fate of grafts (autografts or biomaterial-based grafts) is discussed. Also outlined are parameters and variables that might be manipulated to enhance the efficacy of scaffolds designed for peripheral nerve regeneration. The importance of using appropriate animal models and outcome measures in evaluating biomaterials-based scaffolds or other engineered constructs suitability for bridging peripheral nerve gaps is highlighted.
Animals↗
[Complications of peripheral nerve blocks].
Recent years have brought renewed interest in peripheral nerve blocks as new drugs and materials have become available and as the advantages of such blocks over other anesthetic and analgesic techniques have been demonstrated. We conducted a literature search in PubMed, the Cochrane Library Plus (Spanish version), and Healthgate for the period January 1, 2000 through October 15, 2005 using the key words "complication and peripheral nerve block," "complication and peripheral block anaesthesia," and "complication and plexus anaesthesia." Totals of 178, 109, and 145 titles were obtained with each portal. When the search was limited to reviews, clinical trials, and randomized controlled trials, the numbers of articles from each portal became 11, 20, and 10, respectively, for the first string of key words; 0, 8 and 6, respectively, for the second string; and 10, 40 and 16 for the third. A detailed analysis of the results revealed 2 reviews and 1 clinical trial in which complications of peripheral nerve blocks figured in the main topic. Most of these publications agree that the overall incidence of complications related to these techniques is low. If practice guidelines and algorithms from experts are followed the incidence can be reduced. The aim of this review is to give an updated report of complications related to peripheral nerve blocks.
Algorithms↗
Nerve growth factor receptor immunostaining in the spinal cord and peripheral nerves in amyotrophic lateral sclerosis.
In animal experiments, nerve transection is followed by expression of nerve growth factor receptors (NGFR) on Schwann cells of both motor and sensory nerve fibres distally to the site of the lesion. To determine whether denervated Schwann cells in amyotrophic lateral sclerosis (ALS) similarly express NGFR, a study was made of post-mortem material of peripheral nerves and ventral roots from ALS cases and age-matched controls, using immunolabelling methods. Dorsal roots and spinal cords were also examined for the presence of NGFR. In all the ALS cases and controls, NGFR immunostaining was seen in the outer layer of vessel walls, perineurial sheaths, connective tissue surrounding fascicles in nerve roots and in the substantia gelatinosa of the spinal cord. In ALS, NGFR staining was also present in the Schwann cells of degenerated nerve fibres in mixed peripheral nerves, in ventral roots and, to a lesser extent, in dorsal roots. NGFR immunoreactivity was also seen in elongated cells extending from the perifascicular connective tissue into the nerve fascicles. It is concluded that denervated Schwann cells in ALS express NGFR and that NGFR immunostaining on Schwann cells may be used as an indicator of axonal degeneration. The NGFR labelling in the dorsal roots supports the notion that ALS is not a pure motor syndrome.
Amyotrophic Lateral Sclerosis↗
Impaired regeneration of bcl-2-lacking peripheral nerves.
OBJECT: The outcome of peripheral nerve damage in still not satisfactory, despite the general capacity of peripheral nervous system to regenerate. The molecular mechanisms underlying nerve regeneration are still not clear, but it is likely that apoptosis regulating genes plays a crucial role in these processes. The aim of the present study was to establish the role of the anti-apoptotic gene bcl-2 in peripheral nerve repair. MATERIAL AND METHODS: Sciatic nerves of bcl-2-deficient and wild type mice were transected, and immediately re-sutured. The regeneration was assessed functionally and morphologically throughout the 4-week follow-up. RESULTS: We found markedly worse sciatic function index outcome, as well as more significant atrophy of denervated muscles in bcl-2 knock-out animals when compared with wild-type ones. The intensity of histological regeneration features, including GAP-43-positive growth cones, Schwann cells and macrophages in the distal stump of the transected nerve, was also decreased. The number of motor and sensory neurons in the relevant cross-sections of spinal cord was similar in both groups of mice. CONCLUSION: We concluded that the bcl-2 gene plays an important role in peripheral nerve regeneration, influencing nerve injury site clearing, fiber regrowth and myelination.
Animals↗
Diffusion tensor imaging and tractography of distal peripheral nerves at 3 T.
OBJECTIVE: We studied whether distal peripheral nerves could be imaged using quantitative diffusion tensor imaging (DTI) with a 3-T MRI scanner, and visualized using tractography. METHODS: Altogether 6 healthy subjects were studied. The diffusion was quantified with apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps, and the direction of main diffusivity was visualized with color-coded orientation maps and tractography. RESULTS: We present the first DTI and tractography results of human distal peripheral nerves. The courses of median, ulnar, and radial nerves in the upper limb and of tibial and peroneal nerves in the lower limb were first analyzed quantifying ADC and FA, and then visualized in 3D with tractography. Tractography illustrated nicely the 3D courses of both upper and lower limb nerves which were reliably distinguished from the surrounding muscle tissue and ligaments. CONCLUSIONS: Quantitative DTI and tractography can be used to image and visualize distal peripheral nerves. SIGNIFICANCE: DTI is a quantitative method that could provide useful information for the diagnosis and follow-up of nerve lesions, entrapments, and regeneration. Peripheral nerves as well-delineated structures also containing abundant branching into bundles of different diameters, could be used as 'living phantoms' for testing and validating different tractography methods.
Adult↗
[Alteration of the auditory function and auditory nerve pathology in Guinea pigs with peripheral nerve demyelination].
OBJECTIVE: To study the auditory function and auditory nerve pathological changes of the experimental allergic neuritis (EAN) animal model in Guinea pigs. METHOD: To establish the animal model of EAN, heterologous myelin basic protein (MBP) of peripheral nerve was used to the immunize Guinea pigs. Serum anti-MBP-IgG levels, sciatic nerve conduction velocity (NCV), hearing thresholds and wave latencies, and pathological changes in auditory nerve, sciatic nerve and cochlea were observed. The immune lesions in inner ear were examined with immunohistochemistry. Auditory brainstem response (ABR) and compound action potential (CAP) were assayed weekly before and after immunization for a period of seven weeks. In the control group, antigen was replaced by the 0.9% saline. RESULT: Serum anti-MBP-IgG levels increased significantly in experimental group comparing with the control group (P < 0.01). Seiatic nerve conduction velocity decreased after immunization, as comparing with the control group (P < 0.01). Sciatic nerve and auditory nerve showed the existence of demyelination. There was significant increase of ABR and CAP thresholds and the latencies of wave I, III, V and N1 in experimental group when compared to the controls (P < 0.01), but no significant changes in inter-peak latencies of I-III, III-V were found( P > 0.05). In addition, there were 4 Guinea pigs (8 ears) in which only appeared lengthened wave latencies with normal hearing thresholds. Immunohistochemistry indicated that antibodies to inner ear from the MBP-sensitized animals distributed in cochlear nerve, neurofiber of inner ear and spiral ganglion cells. Cochlear scanning electron microscopy showed the pathology of inner hair cell with stereociliary disorder and cytoplasmic protrusions. CONCLUSION: The results suggest that auditory nerve demyelination are involved in this experimental allergic neuritis animal model and sciatic nerve demyelination as well, and the auditory abnormalities are elicited. This animal model seems to be a promising one of auditory dysfunction due to demyelination disorders.
Action Potentials↗