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Results for “Nerve Compression Syndromes”

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At least 289 records · Page 16Linked to original sources
PubMed1999

[Hypothesis concerning the anatomical basis of cauda equina syndrome and transient nerve root irritation after spinal anesthesia].

OBJECTIVE: Cauda equine syndrome is a rare neurological complication associated with subarachnoid anesthesia, and particularly with the use of 5% hyperbaric lidocaine and small gauge catheters. Our aim was to study a possible anatomical factor that might impede adequate dilution of local anesthetic and explain the development of cauda equine syndrome and transitory radicular irritation. MATERIAL AND METHOD: The spinal dura matters and their contents from two male human cadavers were examined after organs had been extracted for transplantation. Both men had recently died at ages 56 and 65 years of age. Samples were fixed in a glutaraldehyde phosphate buffer and dehydrated in acetone, which was then removed by critical point elimination. The samples were then metallized with gold and observed under a scanning electron microscope. RESULTS: We found that one portion of the arachnoids was more compact and another was lax. The compact portion had a laminar structure formed by the fusion of fibers and cell components lining the inner surface of the dural mater. The lax portion was comprised of a weblike network of filaments and few cells bodies. This portion extended from the compact inner arachnoid lamina to the cell plane of the pia mater, where it dispersed, sending out compact arachnoid projections that wrapped around structures in the subarachnoid space. We termed these wrappings "arachnoid sheaths".

Aged↗
PubMed1995

Nerve conduction velocities in the lower extremities among patients with vibration syndrome.

In order to clarify the effect of vibration syndrome (VS) on the peripheral nervous system (PNS) in the lower extremities, 59 patients with VS (age 58.5 +/- 5.1 years) and 49 age-matched controls (age 57.0 +/- 5.1 years) were examined for sensory nerve conduction velocities (SCV) in the sural nerve (SSCV) and the medial plantar nerve (PSCV) in the summer of 1993 and 1994. They had not been suffering from diseases and injuries which might have affected the SCV in the lower extremities. These patients were divided into two subgroups, one with past vibration exposure to chainsaw (N = 22) and the other with past vibration exposure to rock drills and other tools (N = 37). SCVs corrected by skin temperature were subjected to statistical analysis. In PSCV a significant reduction among all patients (40.8 +/- 4.24 m/s, p < 0.01) including two subgroups (chainsaw, 39.7 +/- 4.7 m/s, p < 0.01; rock drill and others, 41.0 +/- 4.6 m/s, p < 0.01) was observed compared with those of the controls (43.2 +/- 4.31 m/s), but there was no significant reduction in SSCV. Significantly more subjects with PSCV below the standard of PSCV (ten percentile value of those of the controls) were observed among all patients (17/59, 28.8%, p < 0.05) including two subgroups (chainsaw, 7/22, 31.8%, p < 0.05; rock drill and others, 10/37, 27.0%, p < 0.05) than in the controls (4/49, 8.2%). These findings suggested that VS affected the PNS function in the lower extremities and that its mechanism was considered to mediate a circulatory disturbance, and to differ from SCV reduction in the finger.

Case-Control Studies↗
PubMed1999

An electrophysiological exploration of the double crush hypothesis.

The double crush hypothesis has not been rigorously evaluated in humans. We therefore analyzed cases of C6, C7, and C8 radiculopathy and exploited the fact that the median sensory response is of C6/C7 origin and the median motor response is primarily of C8 origin. We hypothesized that C6 and/or C7 cases would demonstrate an increased frequency of median mononeuropathy by sensory criteria, and C8 cases would demonstrate an increased frequency of median mononeuropathy by motor criteria. We also hypothesized that median sensory and motor response parameters among these same groups would be altered in ways consistent with a proximal influence on distal nerve conduction studies. Although median mononeuropathy was unexpectedly common (22.1%) among cases of cervical radiculopathy (which may explain the clinical acceptance of the double crush hypothesis), none of the hypotheses was supported. This study identified no evidence to support a neurophysiological explanation for the double crush hypothesis.

Age Factors↗
PubMed2000

Molecular mechanisms of osteolytic bone metastases.

BACKGROUND: Breast carcinoma commonly metastasizes to the skeleton in patients with advanced disease to cause bone destruction and the associated pain, hypercalcemia, fracture, and nerve-compression syndromes. In this scenario, the bone destruction is mediated by the osteoclast. Tumor-produced parathyroid hormone-related protein (PTHrP), a known stimulator of osteoclastic bone resorption, is a major mediator of the osteolytic process. Transforming growth factor beta (TGFbeta), which is abundant in bone matrix and is released as a consequence of osteoclastic bone resorption, may promote breast carcinoma osteolysis by stimulating PTHrP production by tumor cells. METHODS: Stable breast carcinoma MDA-MB-231 cell lines were constructed that expressed mutant TGFbeta receptors, Smad proteins, or estrogen receptor (ER)-alpha and were used to determine the role of TGFbeta in modulating tumor production of PTHrP. These stable cell lines were applied to a mouse model of human breast carcinoma metastases to the bone to dissect the molecular mechanisms responsible for osteolytic bone metastases. RESULTS: TGFbeta promoted the development and progression of osteolytic bone metastases by inducing tumor production of PTHrP, the effect of which was mediated through the Smad signaling pathway. PTHrP stimulated osteoclastic bone resorption by increasing osteoblast production of the receptor activator of nuclear factor K B (RANK) ligand and decreasing osteoblast production of osteoprotegerin (OPG). A constitutively active ER-alpha mutation (Tyr537Asn), identified from a human bone metastases, when it was expressed in human breast carcinoma cells, caused increased production of PTHrP. TGFbeta significantly enhanced the ER-alpha-mediated transcriptional activity induced by ER-alpha (Tyr537Asn), and this resulted in further stimulation of PTHrP production. CONCLUSIONS: These data indicate a central role for TGFbeta in the pathogenesis of osteolytic bone metastases from breast carcinoma by 1) the induction of PTHrP through the Smad signaling pathway and 2) the potentiation of ER-alpha-mediated transcription induced by a constitutively active ER-alpha. Understanding the mechanisms of osteolysis at a molecular level will generate more effective therapeutic agents for patients with this devastating complication of cancer.

Animals↗
PubMed1996

Neurotrophic factors in the treatment of peripheral neuropathy.

Peripheral neuropathies are common and frequently debilitating disorders which may include various subpopulations of motor, sensory or autonomic neurons depending on the underlying aetiology. They are likely to be the first group of neurological disorders to be successfully treated with growth factors since peripheral nerves are accessible to proteins given systemically. Preclinical and ongoing clinical trials of nerve growth factor (NGF) suggest that it will be useful for the treatment of diabetic, toxic and compressive sensory neuropathies. At appropriate doses NGF has no significant side effects in humans. Since NGF administration to mature animals stimulates synthesis of brain-derived neurotrophic factor and perhaps other neurotrophins in peripheral nerves, the spectrum of neuropathies treatable with NGF is wider than might be predicted. Preclinical studies suggest that insulin-like growth factor 1 (IGF-1) will be useful for the treatment of mixed motor and sensory neuropathies. For example, IGF-1 treatment can prevent the experimental motor and sensory neuropathies caused by the antitumour drugs, vincristine and cisplatin. Other neurotrophic factors have also shown promise in preclinical trials. The successful use of growth factors in the treatment of peripheral neuropathies may provide the first true therapy for this previously untreatable and devastating group of neurological disorders.

Animals↗
PubMed1980

Brachial plexus involvement in familial pressure-sensitive neuropathy: electrophysiological and morphological findings.

Two family members with hereditary pressure-sensitive neuropathy are reported. One patient presented atypically with acute brachial plexus neuropathy following transaxillary removal of the first rib. Electrophysiological studies showed slowing of motor nerve conduction in clinically affected and unaffected nerves. In vitro recording of the compound action potential of the subclinically involved sural nerve showed pronounced slowing in conduction of large and small myelinated fiber groups. These alterations correlated with morphological studies of the sural nerve that showed tomacula with acute and healed segmental demyelination. An inherited, generalized neuropathy manifested by a morphological abnormality of myelination may render peripheral nerves unduly susceptible to mechanical trauma, including positional pressure or traction effects during general anesthesia.

Adult↗
PubMed1984

Principles and pitfalls of nerve conduction studies.

This report reviews the fundamental principles and the changing concepts of nerve stimulation techniques, and discusses the proper application of these techniques in the differential diagnosis of peripheral nerve disorders. Nerve conduction studies help delineate the extent and distribution of the neural lesion and distinguish two major categories of peripheral nerve disease: demyelination and axonal degeneration. Although the method is based on simple principles, pitfalls abound in practice. Variability in nerve conduction measurement may result from temperature change, variations among nerve segments, and the effects of age. Other sources of error include excessive spread of stimulation current, anomalous innervation, temporal dispersion, and inaccuracy of surface measurement. Unlike a bipolar derivation, which selectively records near-field potentials, a referential recording may give rise to stationary far-field peaks from a moving source. Overlooking this possibility can lead to an incorrect interpretation of findings. Conventional nerve conduction studies deal primarily with measurements of the distal nerve segments in an extremity. More recent techniques are applicable to less accessible anatomical regions, as illustrated by elicitation of the blink reflex, F wave, and H reflex, and the use of the inching technique. Other methods used to assess special aspects of nerve conduction include the ischemic test and studies of slow-conducting fibers.

Axons↗
PubMed1989

Structural assessment of rat sciatic nerve following tourniquet compression and vascular manipulation.

In a recent study (Nitz et al., Exp Neurol 94:264-279, 1986) the validity of a rat animal model to examine effects of tourniquet compression and vascular occlusion on limb motor function, leg girth, and electrophysiologic changes was established. Here we report observations on sciatic nerve morphologic and morphometric alterations of these same animals. The hindlimbs of 90 rats were compressed by a pneumatic tourniquet at clinically relevant pressures (200 to 400 mm Hg) for 1 to 3 hours, and the sciatic nerve was assessed by light and electron microscopy at 1, 3, and 6 weeks post compression. The nerves were also examined from five additional animals at each of these time intervals following arterial ligation and sciatic nerve epineurectomy (30 rats). Percentage of degenerating myelinated nerve fibers and volume fraction of mast cells and fibroblasts were quantified morphometrically. The percentage of degenerating myelinated nerve fibers after moderate to severe tourniquet compression and vascular manipulation was similar and ranged from 15% to 45%. Tourniquet compression, but not vascular occlusion, resulted in an increase of mast cells and fibroblasts and disruption of endothelial cells of endoneurial vessels. The results suggest that clinically relevant tourniquet compression causes a secondary increase in vascular permeability, intraneural edema, and subsequent prolonged tissue ischemia, resulting in nerve degeneration.

Animals↗
PubMed1990

Abdominal wall pain: an alternative diagnosis.

The cause of abdominal pain need not necessarily reside in the viscera; the abdominal wall is another source of symptoms. Some causes of abdominal wall pain are obvious, e.g. hernias, but not so others such as nerve entrapment syndromes. This review is concerned with causes of abdominal wall pain which, although common, may be easily overlooked.

Abdominal Muscles↗
PubMed1999

Interleukin-1 beta promotes functional recovery of crushed peripheral nerve.

This study was conducted to elucidate the role of the cytokine interleukin-1 beta on peripheral nerve recovery following crush injuries of two different magnitudes. Eighty-eight female rats were divided into four groups. A 5-mm segment of the right sciatic nerve was subjected to a 100-g crush load for 2 hours in the rats in Groups A1 and B1 or to a 15,000-g crush load for 10 minutes in the rats in Groups A2 and B2. The rats in Groups A1 and A2 received 10 microg/100 g body weight human recombinant interleukin-1 beta intraperitoneally 48, 24, and 1 hours before the nerve injury. The rats in Groups B1 and B2 were treated with an equal volume of normal saline solution with identical schedule guidelines. Walking-track tests (sciatic functional index) performed at intervals until 56 days after the crush and measurements of the contractile force of the extensor digitorum longus muscle made until 28 days were used to evaluate functional recovery of the nerve. During the second week after injury, the rats treated with interleukin-1 beta (A1) had an earlier recovery on the walking track than did those treated with saline solution (B1); this difference reached significance (p < 0.05) at day 11. Although Group A2 demonstrated a trend toward earlier recovery compared with Group B2, there was no significant difference between the two groups. After low or high-load crush injury, tetanic contractile forces were greater in the rats treated with human recombinant interleukin-1 beta than in those treated with saline solution. The results suggest that treatment with human recombinant interleukin-1 beta before crush injury can promote function in the peripheral nerve after the injury. However, the mechanisms that underlie the observed beneficial effects are not completely understood and only speculations can be made.

Animals↗
PubMed2007

Quantitative sensory testing of cold and vibration perception during compression of median nerve at the wrist.

We conducted a sequential study of quantitative sensory testing (QST) during compression-induced conduction block of the median nerve to determine relative vulnerability of the small and large myelinated nerve fibers. We tested cold (CPT) and vibratory perception thresholds (VPT) of the third digit in 15 healthy subjects during constant, localized compression for 30 min of the median nerve at the wrist. The orthodromic sensory nerve action potentials (SNAPs) recorded at wrist and elbow served to monitor the degree of associated conduction block. After the onset of nerve compression, it took 16 min for CPT to show the first change; VPT remained normal for 26 min. CPT recovered 2 min later than VPT after release of compression. The SNAP amplitude at the wrist diminished immediately at the start of compression and declined progressively, whereas the response at the elbow remained the same initially, showing no latency change for 20 min. A nearly identical time course of SNAP changes in the two experiments justified the comparison of separately tested CPT and VPT as a measure of modality-specific vulnerability. Contrary to the common belief, a focal compression sufficient to produce rapidly reversible conduction abnormalities affects the slow-conducting small myelinated fibers mediating cold perception before the fast-conducting large myelinated fibers transmitting vibration perception. The data document the order of modality-specific vulnerability of sensory nerve fibers to mild compression. The finding suggests that testing CPT, rather than VPT, provides a better QST to delineate rapidly reversible symptoms induced by compression.

Action Potentials↗
PubMedDate not supplied

Early recognition of nerve disorders by near-nerve recording of sensory action potentials.

Evaluated herein are the advantages and limitations of recording sensory action potentials with a gross electrode placed near the nerve. This technique has proved to be a sensitive measure of early nerve damage for two reasons: first, electrodes can be positioned in such a way that maximal velocity is determined only along the abnormal stretch of the nerve; and second, small late components originating from demyelinated, remyelinated, or regenerating fibers can be detected.

Demyelinating Diseases↗
PubMedDate not supplied

Subclinical entrapment of the lateral femoral cutaneous nerve: an autopsy study.

Five out of 12 lateral femoral cutaneous nerves, removed at routine autopsies, showed pathologic changes in myelinated nerve fibers in the vicinity of the inguinal ligament. These changes included both local demyelination and Wallerian degeneration, particularly affecting the fibers with the largest diameters. The presence of polarized internodal swellings on single nerve fibers from two specimens suggested that mechanical factors were involved in pathogenesis. Endoneurial vascular thickening confined to the region of the inguinal ligament was also seen and may be implicated in the production of some of the symptoms of meralgia paresthetica (MP).

Adult↗
PubMedDate not supplied

Acute vs. chronic compressive neuropathy.

Studies of the management of acute and chronic compressive peripheral neuropathies have not kept pace with advances in our understanding of the pathophysiology of these disorders. In this review, the pathophysiological differences between acute and chronic compressive neuropathy are reviewed from experimental models as well as from clinical examples in humans. It is concluded that surgical intervention is unlikely to alter significantly the course of recovery in acute compressive neuropathies. Similarly, in chronic compressive neuropathies without progressive weakness, conservative treatment is indicated because of the high incidence of spontaneous improvement. However, in patients with progressive weakness, especially in conjunction with electrophysiological evidence of partial denervation or conduction block (but not simply slowing of nerve conduction), surgical treatment is recommended.

Action Potentials↗
PubMed1991

Quantitation of axon loss and conduction block in peroneal nerve palsies.

We compared conduction in motor fibers supplying the extensor digitorum brevis (EDB) and anterior lateral compartment (AL) muscles. The object was to determine whether there were any differences in the relative proportions of degenerated and blocked nerve fibers between the longer EDB and shorter AL fibers. In almost every case the percentage of motor fibers undergoing axonal degeneration was greatest in EDB fibers. Conversely, the percentage of conduction block was greatest in the AL motor fibers. As clinical recovery is dependent on AL muscles rather than EDB, electrophysiological study of the relative proportions of degenerated and blocked fibers in the former should provide a more reliable measure of outcome than similar studies of EDB. Conduction velocity distal to the fibular head was not slowed despite the large loss of EDB motor fibers. Evidence for selective involvement of the larger myelinated fibers is, therefore, lacking. The location of the major conduction abnormalities was in almost every case between the mid-fibular head and popliteal fossa.

Adult↗
PubMed2000

Onion-bulb formation after a single compression injury in the macrophage scavenger receptor knockout mice.

Onion-bulb (OB) formation is often encountered in acquired neuropathies such as chronic inflammatory demyelinating polyradiculoneuropathy and diabetic neuropathy and is believed to require repeated injuries to peripheral nerves. Although this suggests that remaining damaged cell membranes, including myelin debris, might trigger OB formation, the molecular mechanism remains unclear. In this study, we were successful in producing many small OBs after a single compression injury to peripheral nerves of the knockout mice deficient of macrophage scavenger receptor class A (MSR-A). Although morphometry showed no difference in the average densities of the remaining myelinating fibers between wild-type and MSR-A knockout mice after the compression injury, there were more macrophages and myelin debris positive for oxidized-phosphatidylcholine in the nerves from the MSR-A knockout mice. We believe that OB formation was induced after a single compression injury as the result of delayed phagocytosis of myelin debris possessing oxidized lipids by MSR-A deficient macrophages. The present work shed light on the molecular mechanism of OB formation seen in chronic neuropathies and provided a model for further investigation.

Animals↗