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At least 397 records · Page 22Linked to original sources
PubMed1994

Experimental lumbar radiculopathy. Behavioral and histologic changes in a model of radicular pain after spinal nerve root irritation with chromic gut ligatures in the rat.

OBJECTIVE: The recently proposed animal model of lumbar radiculopathy was used to investigate behavioral consequences and histologic changes in spinal nerve roots, dorsal root ganglia, and spinal nerves after the L4, L5, and L6 nerve roots were loosely ligated with either silk or chromic gut sutures in an attempt to better understand the pathophysiologic mechanisms that give rise to pain associated with lumbar radiculopathy. SUMMARY OF BACKGROUND DATA: Little is known about the pathophysiologic mechanisms that give rise to pain associated with lumbar radiculopathy. The recently proposed animal model of unilateral lumbar radiculopathy, which demonstrated an association with motor paresis and thermal hyperalgesia of the affected hind limb and showed evidence of spontaneous pain has been demonstrated, may serve as a vehicle to allow direct investigation of the nature of the pathophysiological mechanisms associated with lumbar radiculopathy. METHODS: Three distinct treatments of the nerve roots were initially investigated: 1) a sham intervention, where the surgery simply exposed the nerve roots and dorsal root ganglion followed by standard closing procedures; 2) 4-0 silk ligature, where two loose ligatures of 4-0 silk were placed around the nerve roots; and 3) 4-0 chromic gut 2, where four 0.3 cm pieces of 4-0 chromic gut were laid adjacent to the nerve roots and secured by two loose ligatures of 4-0 chromic gut. STUDY DESIGN: ANOVA techniques were used to test for differential effects across time for the three treatment groups in terms of animal function. A qualitative analysis of the histology of the ipsilateral and contralateral nerve roots, dorsal root ganglia, and spinal nerves was done to correlate histologic changes with behavioral changes. RESULTS: Behavioral results were consistent with the previous study. Rats treated with chromic gut, but not silk, reliably demonstrated a prolonged thermal hyperalgesia that was maximal 2 weeks after surgery and lasted for up to 12 weeks. These behavioral changes, however, were not correlated with histologic changes in myelinated fiber content in the L4, L5, and L6 nerve roots, dorsal root ganglia and spinal nerves, the ipsilateral spinal nerved, dorsal root ganglia, and nerve roots of rates ligated with silk or chromic gut showed similar, significant, decreased in the number of large diameter myelinated fibers. CONCLUSIONS: These results suggest that mechanical constriction of the L4, L5, and L6 spinal nerve roots, as evidenced by a loss of myelinated fibers, is not sufficient to produce the behavioral effects associated with this model of lumbar radiculopathy. It is hypothesized that chemical factors from the chromic gut play a role in the pathophysiology and development of the behavioral, but not histological, changes in this model of lumbar radiculopathy.

Animals↗
PubMed1997

Histologic analysis of the lumbosacral nerve roots after compression in young and aged rabbits.

STUDY DESIGN: The histologic changes in the lumbosacral nerve roots of aged rabbits because of chronic (graded) and acute compression were compared with those seen in young rabbits. OBJECTIVES: To study differences in the process of recovery from nerve compression between the aged and the young. SUMMARY OF BACKGROUND DATA: Clinical findings often differ between nerve compressive lesions in young and aged patients. Little has been reported on the pathologic basis of this difference. METHODS: Forty-five Japanese white rabbits were used. The cauda equina and spinal nerve root were compressed with a device specifically designed for this purpose. Nerve compression was applied to the dura mater and nerve roots after partial laminectomy. The specimens were sampled at 1 month or 3 months after acute or graded nerve compression. RESULTS: An increase in small myelinated fibers, consistent with the process of regeneration, was observed by light microscopy; this difference was greater in the young group than in the aged group. Reactive degenerative changes, as seen by electron microscopy, were more often observed in the aged group than in the young group. CONCLUSIONS: These findings demonstrate the suppression of regeneration and the latent fragility of the aged neural tissue. This may explain the clinical findings observed in aged patients with degenerative lumbar lesions.

Age Factors↗
PubMed1998

The function of sensory nerve fibers in lumbar radiculopathy. Use of quantitative sensory testing in the exploration of different populations of nerve fibers and dermatomes.

STUDY DESIGN: The function of sensory nerve fibers in patients with lumbar radiculopathy and in control individuals was evaluated using quantitative sensory testing. OBJECTIVES: To investigate the effect of lumbar nerve root compression on different populations of nerve fibers and to explore the function of sensory nerve fibers in neighboring nerve roots not involved in the mechanical compression. BACKGROUND DATA: Results from experimental and clinical studies indicate that chronic compression of lumbar nerve roots affects the large myelinated nerve fibers. The majority of nerve fibers involved in the sensation of pain, however, are small afferent nerve fibers. It is therefore of interest to study the effect of compression on large and small sensory afferent channels. Several authors have elucidated the biochemical interaction between disc tissue and nerve roots. Chemical substances in the epidural space can reach the nerve fibers in nerve roots at the same or neighboring lumbar segments. In this way, fibers not involved in the mechanical compression may be affected. METHODS: The small nerve fibers were studied using tests for thermal thresholds (thermotest), and the large myelinated fibers were studied by vibrametry. Forty-two patients were investigated in the symptomatic and the asymptomatic leg, and the results were compared with those of 21 healthy individuals. RESULTS: The thresholds of cold, warmth, and vibration were significantly increased in the dermatome of the compressed nerve root, indicating that large and small sensory nerve fibers were affected. Further, the thresholds were significantly increased in the neighboring dermatomes in the symptomatic and the asymptomatic leg. CONCLUSION: Large and small sensory afferent nerve fibers are affected in lumbar radiculopathy. The increase in sensation thresholds in the ipsilateral neighboring dermatome and in the dermatomes in the asymptomatic leg indicates that adjacent nerve roots are involved in the pathophysiology of sciatica in patients with lumbar disc herniation.

Adult↗
PubMed2005

Autonomic fibre sprouting and changes in nociceptive sensory innervation in the rat lower lip skin following chronic constriction injury.

In this study we used immunocytochemistry to investigate whether autonomic fibres sprouted in the skin of the lower lip in a rat model of neuropathic pain. We used a bilateral chronic constriction injury (CCI) of the mental nerve (MN), a branch of the trigeminal nerve. In this model, we also studied the accompanying changes in peptidergic [calcitonin gene-related peptide (CGRP)-immunoreactive] sensory fibres, as well as in trkA receptor immunoreactivity in the sensory nerves. Autonomic (sympathetic and parasympathetic) fibre sprouting was first observed 1 week post-injury with a peak in the number of sprouted fibres occurring at 4 and 6 weeks post-CCI. CGRP-IR fibres almost disappeared at 2 weeks post-CCI, but quickly sprouted, leading to a significant peak above sham levels 4 weeks post-injury. trkA receptor expression was found to be up-regulated in small cutaneous nerves 4 weeks post-CCI, returning to sham levels by 8 weeks post-CCI. There was no sympathetic fibre sprouting in the trigeminal ganglion following CCI. At 4 weeks post-CCI, rats displayed spontaneous, directed grooming to the area innervated by the MN that was not seen in sham animals, which we interpreted as a sign of spontaneous pain or dysesthesiae. Collectively, our findings indicate that as a result of autonomic sprouting due to CCI of the MN, remaining intact nociceptive fibres may potentially develop sensitivity to sympathetic and parasympathetic stimulation, which may have a role in the generation of abnormal pain following nerve injury.

Animals↗
PubMed2006

Demyelination secondary to chronic nerve compression injury alters Schmidt-Lanterman incisures.

The role of Schmidt-Lanterman incisures (SLIs) within the myelin sheath remains the subject of much debate. Previous studies have shown a positive correlation between the number of SLIs per internode and internodal width for both normal and pathological myelin internodes. As chronic nerve compression (CNC) injury induces demyelination, we sought to evaluate if CNC injury altered the occurrence of SLIs using nerve-teasing techniques and light microscopy. Rigorous examination of the teased axons from nerves subjected to CNC injury for 1 month, 2 months or 8 months revealed that there is indeed a positive correlation between the number of SLIs per internode and the internodal width. However, unlike previous studies, the degree of positive correlation between these two parameters was greater in the internodes that had undergone remyelination in response to CNC injury as compared with the internodes from control nerves. These findings support the theory that SLIs are likely to assist in the metabolic processes of the myelin sheath, including growth and maintenance of the myelin sheath.

Animals↗
PubMed1998

Warm and cold sensory thresholds in patients with unilateral sciatica: C fibers are more severely affected than A-delta fibers.

OBJECTIVES: In order to evaluate if nerve root compression or inflammation is the most important pathogenetic mechanism in lumbar radicular pain, we investigated unmyelinated C-fiber function (warm sensation) and myelinated A-delta fiber function (cold sensation) in patients with unilateral L5 or S1 sciatica. MATERIAL AND METHODS: Forty consecutive patients with clinical and radiological evidence of unilateral L5 (n = 29) or S1 (n = 11) sciatica were studied. The warm and cold sensory thresholds (Somedic thermotest, method of limits) were measured on the anterolateral leg (L5 dermatome) and on the calf (S1 dermatome) on both sides. RESULTS: Warm thresholds were significantly higher on the symptomatic side compared to the non-symptomatic side (8.4+/-3.0 vs 6.2+/-2.5 degrees C, P < 0.0005) in the affected dermatome. In a subgroup with confirmed disk herniation at surgery (32 of the 34 operated), significant differences between the symptomatic and the non-symptomatic side for the affected dermatome, were found for both warm (P < 0.0005) and cold (P = 0.003) thresholds. No threshold difference was seen in patients with disk herniations contained within the outer annulus fibrosis (n = 22) compared to those with non-contained herniations (n = 10). CONCLUSIONS: Patients with unilateral sciatica and L5 or S1 nerve root involvement had increased warm thresholds suggesting impaired C-fiber function. Cold thresholds were significantly elevated in a subgroup with operatively confirmed disk herniation. Because myelinated axons are affected more by compression than unmyelinated ones, our results suggest that nerve root inflammation is more important than compression per se in the generation of sciatic pain.

Adult↗
PubMed1995

Changes in nerve fibers adjacent to transplanted VX2 carcinoma in rabbit tongue.

This study was undertaken to examine the relationship between malignant tumor tissue and nerve fibers using a transplantation model and nerve fiber strains. Most of the neural tissue, as well as the other host tissues, showed severe degenerative changes as the transplanted tumor grew. Furthermore, the degenerative changes were chiefly confined to the area anterior to the tumor. These changes were probably provoked chiefly by the compressive effects of the rapidly enlarging transplant. The results could possibly explain clinical symptoms such as paralysis or disturbances in the movement of the tongue observed occasionally in some patients with lingual carcinomas.

Animals↗
PubMed1990

Effects of sympathetic stimulation on C-fibre response after peripheral nerve compression: an experimental study in the rabbit common peroneal nerve.

Non-myelinated C-fibre responses during sympathetic trunk stimulation were studied in rabbit common peroneal nerve 2 weeks after the nerve had been subjected to compression at 400 mmHg for 30 min. Our previous studies have demonstrated that during sympathetic trunk stimulation the compound action potential of uninjured somatic C-fibres is characterized by a reduced amplitude and an increased latency. In the present study, nerve compression changed the C-fibre response to sympathetic stimulation. Three out of eight nerves reacted to nerve compression by increased C-fibre compound action potential amplitude in response to sympathetic stimulation. In three other rabbits with compressed nerves the C-fibre action potential amplitude was unchanged, and in the remaining two rabbits the action potential amplitude was decreased during sympathetic stimulation. The action potential latency increased in all tested compressed C-fibres. The phenomenon of increased C-fibre amplitude during sympathetic activation has not been observed in uninjured nerves. As in uninjured nerves, noradrenaline infusion produced an increased C-fibre action potential amplitude and latency in six animals. Sympathetic stimulation did not affect the A-fibre response. These results indicate that sympathetic activity influences the conduction properties in C-fibres of somatic origin and that the response can be changed after a nerve injury. The findings may be of importance for the understanding of pain aggravation in different types of nerve injuries during increased sympathetic activity.

Action Potentials↗
PubMed1994

The contribution of ischaemia and deformation to the conduction block generated by compression of the cat sciatic nerve.

The pattern of conduction block induced in cat peripheral nerve by compression has been investigated electrophysiologically by recording unitary action potentials. A degree of compression, associated with chronic compression disorders in man, was applied to the cat sciatic nerve and resulted in a conduction block typified by early failure of the slow conducting myelinated axons. By contrast, a greater degree of compression, a degree more likely to result in acute compression lesions, produced a different pattern of effect, inducing early conduction failure in the fast conducting myelinated axons. These results are related to earlier studies which have shown that nerve deformation during compression has a differential action upon fast myelinated axons, while nerve ischaemia has a differential action upon slow myelinated axons.

Action Potentials↗
PubMed1972

Recovery of nerve conduction after a pneumatic tourniquet: observations on the hind-limb of the baboon.

A small pneumatic cuff inflated around the knee was used to produce tourniquet paralysis in baboons. A cuff pressure of 1,000 mm Hg maintained for one to three hours produced paralysis of distal muscles lasting up to three months. Nerve conduction studies showed that most of the motor fibres to the abductor hallucis muscle were blocked at the level of the cuff and that they conducted impulses normally in their distal parts. There was a significant correlation between the duration of compression and that of the subsequent conduction block. When tested two to three weeks after the tourniquet, the amplitude of the response of m. abductor hallucis to nerve stimulation distal to the cuff was usually slightly reduced compared with the precompression figure. This was assumed to mean that a small proportion of the motor fibres had undergone Wallerian degeneration as a result of compression. Maximal motor conduction velocity was reduced in recovering nerves. It was also reduced when a cuff pressure of 500 mm Hg was used, which was insufficient to produce persistent conduction block. In such cases a reduced velocity without evidence of block could be demonstrated 24 hours after compression. Ascending nerve action potentials were recorded from the sciatic nerve in the thigh, with stimulation at the ankle. Before compression the fastest afferent fibres had a significantly higher velocity than the fastest motor fibres in the same nerve trunk. Results after compression suggested that the high-velocity afferent fibres had a susceptibililty to the procedure similar to that of the fastest motor fibres.

Action Potentials↗
PubMed1974

Pattern of recruiting human motor units in neuropathies and motor neurone disease.

The pattern of recruiting human motor units in the first dorsal interosseous muscle of the hand has been studied in 31 patients with ulnar neuropathies and motor neurone disease. Two years after surgical repair of an unilateral complete severance of the ulnar nerve, the twitch tensions increased to normal size. However, the normal orderly pattern of recruiting motor units of increasing size during increasing voluntary contractions was irretrievably lost. Among patients with pressure or entrapment neuropathies, the normal orderly pattern of recruiting motor units was always retained. Similarly, in patients with motor neurone disease (amyotrophic lateral sclerosis), the orderly pattern of recruitment was not disrupted.

Amyotrophic Lateral Sclerosis↗
PubMed1974

Contractile and electrical properties of human motor units in neuropathies and motor neurone disease.

The contractile and electrical properties of motor units in the first dorsal interosseous muscle of the hand have been studied in 26 patients with ulnar neuropathies and motor neurone disease (amyotrophic lateral sclerosis). Among patients with unilateral pressure or entrapment ulnar neuropathies, there was a tendency for the twitch tensions for single motor units to be smaller, while the surface EMG amplitudes were generally larger in the affected hands. Very large EMG amplitudes but normal size twitch tensions were observed among the motor neurone disease patients, indicating that, in general, motor units enlarged by sprouting are less efficient contractile units than units of normal physiological size.

Action Potentials↗
PubMed1979

Nerve conduction, tactile sensibility, and the electromyogram after suture or compression of peripheral nerve: a longitudinal study in man.

In three patients sequential studies were performed of sensory and motor conduction after complete section and suture of the median nerve at the wrist and in one patient after partial section of the nerve. The sensory potential evoked by stimuli to digits III and I and recorded proximal to the suture line at the wrist appeared after a delay of three to four months, corresponding to a growth rate of 1.5-2.0 mm per day. From early in the course of regeneration the sensory potential was dispersed in 40 components. In the adult patient the cumulative amplitude increased for two years slowly and thereafter at a two times faster rate. Amplitude and tactile sensibility were normal after 40 months, but the sensory potential was still five times more dispersed than normal. The overall increase in the amplitude of the sensory potentials in children aged 10 and 12 years was three times faster than in adults. In the adults and in the children the maximum sensory conduction velocity was 10-25% of normal. It then increased at 3% per month during the first two years, and thereafter 10 times slower. Forty months after suture in the adults and 13-19 months after suture in the children the conduction velocity had reached 65-75% of normal. The pattern of discrete electrical activity during voluntary effort and the prolonged duration of motor unit potentials indicate persistent enlargement of the reinnervated motor units by peripheral sprouting. The sensory potential recovered five times faster after a compressive nerve lesion than after section and suture as seen in another patient with an affection of the ulnar nerve at the elbow. Normal tactile sensibility was attained 10 times faster than after section and suture. Maximum sensory and motor condution velocity recovered within one year from 60-70% to 80-90% of normal.

Adult↗
PubMed1980

Blockage of axonal transport induced by acute, graded compression of the rabbit vagus nerve.

Rapid axonal transport in rabbit vagus nerve was studied during and after graded nerve compression. Proteins of the rapid axonal transport were labelled by micro-injection of 3H-leucine into the nodose ganglion and the cervical vagus nerve was subjected to graded compression by a small "mini-cuff" applied directly to the exposed nerve trunk. The results showed that even slight trauma to the nerve, in this model represented by a pressure at 50 mmHg applied for two hours, may induce accumulation of axonally transported proteins at the level of compression. This transport block was, however, reversible within one day. 200 mmHg and 400 mmHg applied for two hours similarly induced a block of axonal transport persisting up to at least one and three days respectively after the compression. Time for recovery of normal transport was correlated with the magnitude of the pressure applied to the nerve. The results indicate that axons may survive, that is not undergo Wallerian degeneration, after blockage of rapid axonal transport persisting at least one day after the compression trauma.

Animals↗
PubMed1984

Normal proximal and delayed distal conduction in the pudendal nerves of patients with idiopathic (neurogenic) faecal incontinence.

The latency of the response in the external anal sphincter muscle following transcutaneous stimulation of the cauda equina at the L1 vertebral level was measured in nine women with neurogenic faecal incontinence (mean 7.3 SD 0.7 ms) and 11 normal subjects (mean 5.6 SD 0.6 ms) (p = 0.01). There was no difference in conduction velocity between the L1 and L4 vertebral levels thus supporting the suggestion that conduction delay in faecal incontinence occurs distally.

Adult↗
PubMed1987

The effects of cold on a partially denervated muscle.

The abductor digiti minimi of a patient had undergone partial denervation with some subsequent re-innervation. Cooling of the muscle caused a severe reduction in the EMG and force which accompanied either voluntary effort or tetanic nerve stimulation, but it had little effect on the response to single stimuli. The ineffectual attempts at voluntary contraction of the cooled muscle did, however, block the response to single nerve stimuli. Administration of cholinesterase inhibitors did not improve neuromuscular transmission in the cooled muscle, but usually made it worse. It is concluded that depolarisation block may contribute to the weakness of cooled denervated muscles.

Action Potentials↗