Mechanism Of Nerve Injury Research Articles

Agmatine reverses pain induced by inflammation, neuropathy, and spinal cord injury.

Antagonists of glutamate receptors of the N-methyl-d-aspartate subclass (NMDAR) or inhibitors of nitric oxide synthase (NOS) prevent nervous system plasticity. Inflammatory and neuropathic pain rely on plasticity, presenting a clinical opportunity for the use of NMDAR antagonists and NOS inhibitors in chronic pain. Agmatine (AG), an endogenous neuromodulator present in brain and spinal cord, has both NMDAR antagonist and NOS inhibitor activities. We report here that AG, exogenously administered to rodents, decreased hyperalgesia accompanying inflammation, normalized the mechanical hypersensitivity (allodynia/hyperalgesia) produced by chemical or mechanical nerve injury, and reduced autotomy-like behavior and lesion size after excitotoxic spinal cord injury. AG produced these effects in the absence of antinociceptive effects in acute pain tests. Endogenous AG also was detected in rodent lumbosacral spinal cord in concentrations similar to those previously detected in brain. The evidence suggests a unique antiplasticity and neuroprotective role for AG in processes underlying persistent pain and neuronal injury.

Expression of nonclassical MHC class I (RT1-U) in certain neuronal populations of the central nervous system.

Major histocompatibility complex (MHC) class I genes consist of classical (Ia) and nonclassical (Ib) types. Recently, a set of structurally similar MHC class Ib genes in the rat, denoted RT1-U, was described. We here demonstrate expression of RT1-U mRNA using highly stringent oligonucleotide in situ hybridization in several different neuronal populations, including different motor nuclei and the substantia nigra in the rat MHC (c) and (n) haplotypes under normal conditions. The expression pattern for beta2-microglobulin mRNA was almost identical. In contrast, neuronal expression of classical MHC class I (RT1-A) was low. Interestingly, after mechanical nerve injury, glial cells predominantely upregulated expression of RT1-A, whereas neuronal expression of RT1-U remained unchanged. Neuronal expression of nonclassical MHC class I may thus be important for immune surveillance in the nervous system.

Axillary block complicated by hematoma and radial nerve injury

Background and Objectives. Hematoma is typically cited as one mechanism of nerve injury following axillary block. However, documented cases of this are lacking. Methods. A healthy 38-year-old man was scheduled for surgical removal of a tumor of the hand. A transarterial axillary block was performed with a 22-gauge short-bevel needle using 40 mL of a mixture of equal volumes of 1.5% lidocaine and 0.5% bupivacaine containing 1:200,000 epinephrine. No paresthesias were reported. Post-operative, the patient developed a large axillary hematoma accompanied by paresthesias and radial nerve weakness. Results. With conservative management, nerve recovery was complete in 6 months. Conclusions. Hematoma complicating axillary block may result in nerve dysfunction.

Strain dependent differences in the inflammatory response to mechanical nerve injuries

Strain dependent differences in the inflammatory response to mechanical nerve injuries

Plasticity in the expression of bradykinin binding sites in sensory neurons after mechanical nerve injury

The pro-inflammatory mediator bradykinin plays an important role in hyperalgesia during inflammatory conditions. Here, we used unilateral ligation of the sciatic nerve to investigate whether the expression of bradykinin binding sites in isolated rat dorsal root ganglion neurons is changed following nerve injury. Under control conditions, the percentage of neurons expressing bradykinin binding sites increased from 52% at day 0.8 in culture to 93% at day 1.8 and decreased to 67% at day 3.8. Following nerve ligation either two or 10 days prior to the isolation of the somata, the percentage of neurons from ipsilateral ganglia that expressed bradykinin binding sites was already 87% and 86%, respectively, at day 0.8 in culture; this level was maintained at day 1.8 and decreased slightly at day 3.8. In control neurons, high densities of bradykinin binding sites on individual neurons were observed no sooner than at day 1.8, but already at day 0.8 following nerve ligation, due to a “ de novo” expression of B1 receptors and augmentation of B2 receptors. Neurons from the contralateral side responded similarly to ipsilateral neurons after a two day nerve ligation, however, after either a 10 day ligation or a sham operation neurons responded similarly to control neurons. These data are the first evidence that expression of B1 receptors is induced and expression of B2 receptors is enhanced in sensory neurons following nerve ligation. Under pathophysiological conditions, increased expression of subtypes of bradykinin receptors in sensory neurons could contribute to chronic pain conditions.

Positioning in Anesthesia and Surgery. 3rd ed

Positioning in Anesthesia and Surgery. 3rd ed., John T. Martin and Mark A. Warner, eds. Saunders, Philadelphia: WB 1997, ISBN 0-7216-6674-4, 345 pp, $75.00. Positioning in Anesthesia and Surgery, is a multi-authored, hardcover book with minimum overlapping of information among chapters. It is divided into seven different sections, with each section having between one and five chapters. It is easy to read and well referenced, and the chapters are well illustrated with clear drawings by Roy E. Schneider. Section I discusses the general principles of surgical positioning of an anesthetized patient, followed by an overview of the basic operating Table withits various modifications. Subsequent chapters in Sections II-V describe the process of positioning an anesthetized patient in the desired surgical posture, i.e., supine, prone, lateral decubitus, sitting, and lithotomy, in a stepwise fashion. The physiological changes brought about by these positions in an anesthetized patient are well discussed. This book makes it quite clear that the process of getting an anesthetized patient to a desired position is a team-work approach requiring communication, coordination, meticulousness, and vigilance among operating room workers. Section VI describes positioning in special conditions because of unique surgical requirements, e.g., extracorporeal shockwave lithotripsy in waterbath or in nonwaterbath. Similarly, positioning in various patient populations, e.g., morbidly obese, pediatric, pregnant and geriatric, is well described. Their special needs, i.e., technical difficulty in handling the morbidly obese, guarding against hypothermia while positioning a pediatric patient, supine hypotensive syndrome in the obstetric patient, degenerative diseases of the geriatric population, and altered physiological state with its attendant implication in positioning are well discussed. In Section VII, possible predisposing factors and mechanism of nerve injury during the perioperative period and quick and reliable ways of diagnosing major peripheral nerve injury are described. Finally, Chapter 21 in Section VII discusses the medico-legal consideration and reminds the clinician to keep adequate documentation regarding surgical positioning for future reference. In summary, as Dr. Martin states in the introduction, "Outlining specific techniques for establishing a surgical postures can be 'cook-bookish.' Potentially, the practice implies that the reader will accept the presentation as the definitive standard for that maneuver, condemn all other alternatives, and attempt to enforce compliance thereto. Such an interpretation we neither intend nor support." To that end, this book provides the reader with ample information in achieving a particular surgical posture, its physiological implications on the anesthetized patient, and ways and means of avoiding potential complications arising from the position. This book is highly recommended for anesthesiology department libraries so that clinicians can use it as a quick reference guide to bring about desired patient outcome. Gaury S. Adhikary, MD Theodore J. Sanford, Jr. MD Department of Anesthesiology; University of Michigan; Ann Arbor, MI 48109-0048

Positioning in Anesthesia and Surgery. 3rd ed

Positioning in Anesthesia and Surgery. 3rd ed., John T. Martin and Mark A. Warner, eds. Saunders, Philadelphia: WB 1997, ISBN 0-7216-6674-4, 345 pp, $75.00. Positioning in Anesthesia and Surgery, is a multi-authored, hardcover book with minimum overlapping of information among chapters. It is divided into seven different sections, with each section having between one and five chapters. It is easy to read and well referenced, and the chapters are well illustrated with clear drawings by Roy E. Schneider. Section I discusses the general principles of surgical positioning of an anesthetized patient, followed by an overview of the basic operating Table withits various modifications. Subsequent chapters in Sections II-V describe the process of positioning an anesthetized patient in the desired surgical posture, i.e., supine, prone, lateral decubitus, sitting, and lithotomy, in a stepwise fashion. The physiological changes brought about by these positions in an anesthetized patient are well discussed. This book makes it quite clear that the process of getting an anesthetized patient to a desired position is a team-work approach requiring communication, coordination, meticulousness, and vigilance among operating room workers. Section VI describes positioning in special conditions because of unique surgical requirements, e.g., extracorporeal shockwave lithotripsy in waterbath or in nonwaterbath. Similarly, positioning in various patient populations, e.g., morbidly obese, pediatric, pregnant and geriatric, is well described. Their special needs, i.e., technical difficulty in handling the morbidly obese, guarding against hypothermia while positioning a pediatric patient, supine hypotensive syndrome in the obstetric patient, degenerative diseases of the geriatric population, and altered physiological state with its attendant implication in positioning are well discussed. In Section VII, possible predisposing factors and mechanism of nerve injury during the perioperative period and quick and reliable ways of diagnosing major peripheral nerve injury are described. Finally, Chapter 21 in Section VII discusses the medico-legal consideration and reminds the clinician to keep adequate documentation regarding surgical positioning for future reference. In summary, as Dr. Martin states in the introduction, "Outlining specific techniques for establishing a surgical postures can be 'cook-bookish.' Potentially, the practice implies that the reader will accept the presentation as the definitive standard for that maneuver, condemn all other alternatives, and attempt to enforce compliance thereto. Such an interpretation we neither intend nor support." To that end, this book provides the reader with ample information in achieving a particular surgical posture, its physiological implications on the anesthetized patient, and ways and means of avoiding potential complications arising from the position. This book is highly recommended for anesthesiology department libraries so that clinicians can use it as a quick reference guide to bring about desired patient outcome. Gaury S. Adhikary, MD Theodore J. Sanford, Jr. MD Department of Anesthesiology; University of Michigan; Ann Arbor, MI 48109-0048

Central and peripheral nervous complications of dental treatment

This review outlines the complications involving the central or peripheral nervous system arising from dental procedures reported in the last decade. By far the commonest complications were related to intraoperative mechanical peripheral nerve injury. Trauma to branches of the mandibular nerve occurring during oral operations may potentially result in varying degrees of hypoesthesia, paresthesia, dysesthesia or in chronic pain syndromes. An increase in malpractice suits related to such a complication has been recognized in the late years. A warning of the possibility of occurrence of this complication should to be given to all patients undergoing risky procedures as part of the process of obtaining informed consent to operation. Mandibular third molar extraction seems to be alone the most hazardous procedure related to mechanical nerve injuries and also with anesthesiological accidents. Severe but rather infrequent infectious (meningitis, brain abscess and cavernous sinus thrombophlebitis) and anesthesiological complications (occular and facial palsies, optic nerve injury and complications related to general anesthesia) were also reported in this period.

Diaphragm pacing in infants and children. A life-table analysis of implanted components.

Since 1976, we have implanted bilateral phrenic nerve electrodes for diaphragm pacing in 33 infants and children. This population includes 23 patients with congenital central hypoventilation syndrome (CHS), two with late onset CHS and hypothalamic dysfunction, three with hypoventilation associated with Chiari II malformation and myelomeningocele, and five with quadriplegia. Our experience, totalling 192 system-years and 96 patient-years of pacing, has enabled us to document the nature and frequency of problems related to the implanted components of the Avery Laboratories (S-232-1) pacemaker system when used in a pediatric population. By life table analysis, the mean time to need for replacement of any implanted component was 56.3 months. A total of 26 failures requiring component replacement occurred and were classified into four types: (1) receiver failure (15 cases), (2) electrode wire or wire insulation breakage (six cases), (3) infection requiring diaphragm pacer system removal (three cases), and (4) mechanical nerve injury (two cases). We conclude that the present diaphragm pacing system is effective but not without risk of biomedical component failure. The present system might be substantially improved by (1) a modified receiver design with a hermetic seal to prevent fluid penetration, (2) stronger, better insulated electrode wires, and (3) modifications of surgical technique and electrode type to prevent phrenic nerve damage.

Common peroneal nerve palsy associated with pelvic surgery for cancer. An analysis of 11 cases.

Eleven occurrences of common peroneal palsies following pelvic surgery for malignant conditions are reported. The patients' clinical course and possible mechanisms of nerve injury were reviewed. It was concluded that the current belief that all peripheral neuropathies occurring under general anesthesia are preventable may not be applicable to patients with pelvic cancer who must undergo tedious, lengthy, meticulous, extirpative surgery in the dorsal lithotomy position. In patients with tumors that are seemingly isolated to the pelvis, amenable for surgical resection, the possible risk of a peripheral nerve injury is superseded if beneficial effects are obtained by controlling the local manifestations of the tumor.

Mechanical Injury of Peripheral Nerves: Fine Structure And Dysfunction

In summary we have examined the morphology of the normal peripheral nerve, presented the types of mechanical nerve injury and associated histopathology, and discussed possible mechanisms responsible for symptoms of pain, paresthesiae, and weakness associated with these lesions. Neurapraxia consists of intussusception of axon and myelin through the nodes of Ranvier resulting in prolonged nerve conduction block. Axonotmesis and neurotmesis describe more severe disruptions of nerve fiber architecture, are difficult to distinguish electrophysiologically, and have poorer prognoses for functional regenerative repair. Chronic entrapment lesions consist of telescoping myelin internodes and tapering of the sheaths with bulbous polarization of internodes away from the site of injury. Both acute and chronic lesions chiefly involve large myelinated fibers and both may create neuralgia, although the mechanism by which this occurs is poorly understood. Presently, increasing evidence suggests ectopic impulse generators and ephaptic transmission may be responsible for sensorimotor phenomena in these lesions.

The relationship of Schwann cell migration in vitro to injury, using normal, Wobbler, and Dystrophic mice

A quantitative in vitro study of the cellular outgrowth from mouse sciatic nerve explants has been carried out using both normal untreated nerves and nerves taken at various times afer the in vivo application of trauma. The results obtained have been compared with the results for outgrowth from sciatic nerve of two neurological mutants: ‘the Wobbler mouse’ and the ‘ReJ 129 Dystrophic mouse’. It has been shown that the in vitro response to peripheral nerve injury does reflect the activity known to occur in vivo. Outgrowth from explants of mutant mouse nerves, although differing from normal has been found to be less profuse than that occurring after mechanical nerve injury.

Effect of mechanical nerve injury on the permeability of blood vessels

Effect of mechanical nerve injury on the permeability of blood vessels