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PubMed2001

Effect of endplate conditions and bone mineral density on the compressive strength of the graft-endplate interface in anterior cervical spine fusion.

STUDY DESIGN: Destructive compression tests and finite element analyses were conducted to investigate the biomechanical strength at the graft-endplate interface in anterior cervical fusion. OBJECTIVES: To investigate the effect of endplate thickness, endplate holes, and bone mineral density of the vertebral body on the biomechanical strength of the endplate-graft interface in an anterior interbody fusion of the cervical spine. SUMMARY OF BACKGROUND: Subsidence of the graft into the vertebral body is a well-known complication in anterior cervical fusion. However, there is no information in the literature regarding the compressive strength of the graft-endplate interface in relation to the endplate thickness, holes in the endplate, and bone mineral density of the vertebral body. METHODS: Biomechanical destructive compression tests and finite element analyses were performed in this study. Cervical vertebral bodies (C3-C7) isolated from seven cadaveric cervical spines (age at death 69-86 years, mean 79 years) were used for compression tests. Bone mineral density of each vertebral body was measured using a dual energy radiograph absorptiometry unit. Endplate thickness was measured using three coronal computed tomography images of the middle portion of the vertebral body obtained using a computer-assisted imaging analysis. Then each vertebral body was cut into halves through the horizontal plane. A total of 54 specimens, consisting of one endplate and half of the vertebral body, were obtained after excluding eight vertebrae with gross pathology on plain radiograph. Specimens were assigned to one of three groups with different endplate conditions (Group I, intact; Group II, partial removal; and Group III, complete removal) so that group mean bone mineral density became similar. Each endplate was slowly compressed until failure using an 8-mm-diameter metal indenter, and the load to failure was determined as a maximum force on a recorded force-displacement curve. The effect on the strength of the graft-endplate interface of various hole patterns in the endplate was studied using a finite element technique. The simulatedhole patterns included the following: one large central hole, two lateral holes, two holes in the anterior and posterior portion of the endplate, and four holes evenly distributed from the center of the endplate. Stress distribution in the endplate was predicted in response to an axial compressive force of 110 N, and the elements with von Mises stress greater than 4.0 MPa were determined as failed. RESULTS: The endplate thickness and bone mineral density were similar at all cervical levels, and the superior and inferior endplates had similar thickness at all cervical levels. There was no significant association between bone mineral density and endplate thickness. Load to failure was found to have a significant association with bone mineral density but not with endplate thickness. However, load to failure tends to decrease with incremental removal of the endplate, and load to failure of the specimens with an intact endplate was significantly greater than that of the specimens with no endplate. Finite element model predictions showed significant influence of the hole pattern on the fraction of the upper endplate exposed to fracture stress. A large hole was predicted to be more effective than the other patterns at distributing a compressive load across the remaining area and thus minimizing the potential fracture area. CONCLUSION: Results of this study suggest that it is important to preserve the endplate as much as possible to prevent graft subsidence into the vertebral body, particularly in patients with poor bone quality. It is preferable to make one central hole rather than multiple smaller holes in the endplate for vascularity of the bone graft because it reduces the surface area exposed to fracture stresses.

Aged↗

PubMed2001

Effects of diclofenac and ketoprofen on nerve conduction velocity in experimental nerve root compression.

STUDY DESIGN: The effects of diclofenac and ketoprofen on nerve conduction velocity in experimental nerve root compression were evaluated in a setup using an established pig model. OBJECTIVE: To assess the effects of two potent nonsteroidal antiinflammatory drugs, diclofenac and ketoprofen, in experimental nerve root compression. SUMMARY OF BACKGROUND DATA: Compression of spinal nerve roots is recognized to be of major etiologic importance for several common spinal pain syndromes. Secondary inflammatory changes, induced by microvascular permeability changes and leakage of inflammatory mediators into the endoneural tissue, have been proposed as important for the induction of spinal nerve root injury by chronic compression. METHODS: This study involved 21 pigs. An ameroid constrictor was used to induce compression. Seven pigs were treated with daily intramuscular injections of diclofenac 3 mg/kg for 7 days. Seven other pigs were treated with daily intramuscular injections of ketoprofen 4 mg/kg. For a control, seven pigs did not receive any drug treatment. After 7 days, the pigs were reanesthetized, and the nerve conduction velocity in the compressed nerve root segments was determined. RESULTS: The nerve conduction velocity was significantly higher (P < 0.05, Student's t test) in the pigs treated with diclofenac (50 +/- 16 m/second) than in the untreated pigs (32 +/- 15 m/second). The nerve conduction velocity also was significantly higher (P < 0.05) in the pigs treated with ketoprofen (59 +/- 16 m/second) than in the untreated pigs. There were no significant differences in nerve conduction velocity between pigs treated with ketoprofen and those treated with diclofenac. CONCLUSIONS: The findings indicate that intramuscular administration of diclofenac or ketoprofen, both potent antiinflammatory drugs, may reduce nerve root dysfunction induced by compression of spinal nerve roots in an experimental pig model.

Animals↗

PubMed2005

Compression and reconstruction of sorted PET listmode data.

BACKGROUND: In nuclear medicine data can be stored in histogram or listmode format. The most popular histogram format is the planar projection format. Due to the increase in detector blocks, the improved energy resolution and the trends towards time of flight, dynamic and gated imaging, it can be more appropriate to store the data in listmode format. The size of the storage in this format increases linearly with the number of properties (positions, energy, time info) while the histogram format increases exponentially. However, the datasize of listmode data also increases linearly with the number of coincidences. Due to the high number of counts in 3D PET this will lead to very large datasets. Therefore a good compression algorithm for listmode data is very important. METHODS: A sorting and compression method is proposed to reduce the amount of space needed to store the listmode dataset. One event is represented by one number without any information loss compared to the original listmode file. The next step is to sort all events into an array of increasing numbers. These data are compressed by the gzip routine. One of the advantages of 3D PET listmode reconstructions is that they result in a more uniform resolution across the field of view (FOV), which is not always true for other reconstruction algorithms. This improved resolution is shown for the listmode data of a gamma camera operating in PET mode. RESULTS: First the effect of positional accuracy in the listmode dataset is evaluated by comparing resolution in the reconstructions. It is shown that the highest accuracy is not necessary and a significant reduction in the size of the dataset can be obtained prior to lossless compression. A further reduction can be obtained by using the proposed sorting and compression techniques. It is shown that the storage space decreases linearly with the logarithm of the number of coincidences. The compression obtained by different acquisition matrices was compared. Finally it is shown that the 3D listmode reconstruction of sorted listmode data is faster because of improved cache behaviour. The method can be applied to any kind of listmode data. The compression factors will improve when the ratio of measured events to possible events increases.

Algorithms↗

PubMed1985

Risk factors associated with ulnar nerve compression in bedridden patients.

This study was undertaken to determine the incidence of ulnar nerve compression in patients on bedrest and to determine which historical risk factors and assessment measures were most predictive of ulnar nerve compression. Thirty subjects were chosen from the orthopedic, neurological/neurosurgical, and rehabilitation units of two teaching hospitals. The incidence of ulnar nerve compression in this population was 23 percent (seven cases). The overall incidence of compression was then compared with the incidence of subjects having certain risk factors. A combination of two risk factors in subjects carried a greater relative risk of ulnar nerve compression than the presence of single risk factors alone. Using multiple regression analysis, the best multivariate model consisted of four variables which explained 72.8 percent of the variance in ulnar nerve compression. The findings suggest the use of an elbow flexion test and simple questioning as a method for screening patients at higher risk of ulnar nerve compression.

Adult↗

PubMed2005

Wavelet-based lossy-to-lossless ECG compression in a unified vector quantization framework.

In a prior work, a wavelet-based vector quantization (VQ) approach was proposed to perform lossy compression of electrocardiogram (ECG) signals. In this paper, we investigate and fix its coding inefficiency problem in lossless compression and extend it to allow both lossy and lossless compression in a unified coding framework. The well-known 9/7 filters and 5/3 integer filters are used to implement the wavelet transform (WT) for lossy and lossless compression, respectively. The codebook updating mechanism, originally designed for lossy compression, is modified to allow lossless compression as well. In addition, a new and cost-effective coding strategy is proposed to enhance the coding efficiency of set partitioning in hierarchical tree (SPIHT) at the less significant bit representation of a WT coefficient. ECG records from the MIT/BIH Arrhythmia and European ST-T Databases are selected as test data. In terms of the coding efficiency for lossless compression, experimental results show that the proposed codec improves the direct SPIHT approach and the prior work by about 33% and 26%, respectively.

Algorithms↗

PubMed2006

Lossless compression of VLSI layout image data.

We present a novel lossless compression algorithm called Context Copy Combinatorial Code (C4), which integrates the advantages of two very disparate compression techniques: context-based modeling and Lempel-Ziv (LZ) style copying. While the algorithm can be applied to many lossless compression applications, such as document image compression, our primary target application has been lossless compression of integrated circuit layout image data. These images contain a heterogeneous mix of data: dense repetitive data better suited to LZ-style coding, and less dense structured data, better suited to context-based encoding. As part of C4, we have developed a novel binary entropy coding technique called combinatorial coding which is simultaneously as efficient as arithmetic coding, and as fast as Huffman coding. Compression results show C4 outperforms JBIG, ZIP, BZIP2, and two-dimensional LZ, and achieves lossless compression ratios greater than 22 for binary layout image data, and greater than 14 for gray-pixel image data.

Algorithms↗

PubMed2006

Efficient transmission of compressed data for remote volume visualization.

One of the goals of telemedicine is to enable remote visualization and browsing of medical volumes. There is a need to employ scalable compression schemes and efficient client-server models to obtain interactivity and an enhanced viewing experience. First, we present a scheme that uses JPEG2000 and JPIP (JPEG2000 Interactive Protocol) to transmit data in a multi-resolution and progressive fashion. The server exploits the spatial locality offered by the wavelet transform and packet indexing information to transmit, in so far as possible, compressed volume data relevant to the clients query. Once the client identifies its volume of interest (VOI), the volume is refined progressively within the VOI from an initial lossy to a final lossless representation. Contextual background information can also be made available having quality fading away from the VOI. Second, we present a prioritization that enables the client to progressively visualize scene content from a compressed file. In our specific example, the client is able to make requests to progressively receive data corresponding to any tissue type. The server is now capable of reordering the same compressed data file on the fly to serve data packets prioritized as per the client's request. Lastly, we describe the effect of compression parameters on compression ratio, decoding times and interactivity. We also present suggestions for optimizing JPEG2000 for remote volume visualization and volume browsing applications. The resulting system is ideally suited for client-server applications with the server maintaining the compressed volume data, to be browsed by a client with a low bandwidth constraint.

Algorithms↗

PubMed2004

Compression stockings reduce occupational leg swelling.

BACKGROUND: Evening edema of the legs is a physiologic phenomenon occurring after sitting and standing. OBJECTIVE: The objective of this study was to investigate which compression pressure is necessary to prevent leg swelling. METHODS: In 12 volunteers, the volume of both lower legs was measured in the morning and 7 h later, the difference being defined as evening edema (mL). The procedure was carried out for 4 days, in which the subjects wore below-knee stockings of different compression levels alternatively on one leg only in a random order. Compression pressure was assessed using the HATRA device. RESULTS. The average evening edema of the noncompressed legs was 62.4 mL on the left side and 94.4 mL on the right side (n.s.). Evening edema was significantly reduced to 40.3 mL by light support stockings, to -34.1 mL by compression class A, to -39.6 by compression class I, and to -59.1 mL by compression class II. Mainly stockings exerting a pressure above 10 mmHg improved subjective symptoms. CONCLUSION: Calf-length compression stockings with a pressure range between 11 and 21 mmHg are able to reduce or totally prevent evening edema and may therefore be recommended for people with a profession connected with long periods of sitting or standing.

Adult↗

PubMed1991

Chronic cervical compressive myelopathy in horses: clinical correlations with spinal cord alterations.

Histological examination was performed on the cervical spinal cord from 13 horses with chronic cervical compressive myelopathy of 4 to 29 months duration. Structural alterations were correlated with clinical features. At the level of compression, the spinal cord was grossly deformed. Histological alterations included nerve fibre swelling and degeneration, occasional spheroids, astrocytic gliosis, increased macrophage activity and increased perivascular collagen. Myelin degeneration or loss at the level of the compressive lesion was greatest in the ventral and lateral funiculi and less consistently present in the dorsal funiculi. Asymmetry of lesions in the dorsal funiculi was associated with asymmetry of clinical signs in 5 horses. Histological alterations in areas of Wallerian degeneration were similar to that at the level of spinal cord compression, except that perivascular collagen was not increased. Wallerian degeneration was present cranial to the compressed site in the superficial portions of the lateral funiculi and in the middle of the dorsal funiculi. Caudal to the compressed site it was present in the ventral funiculi adjacent to the ventral median fissure and in the middle of the lateral funiculi. Deformation of the spinal cord did not correlate with the severity or duration of clinical signs but was positively correlated with the amount of perivascular collagen increase. The amount of nerve fibre swelling was not correlated with the severity of clinical signs but was negatively correlated with their duration. A rapid loss of nerve fibres apparently occurred early in the course of compression, since there was a marked decrease in the amount of nerve fibre swelling and Marchi stained degenerating myelin with increasing clinical duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

The role of flow-independent viscoelasticity in the biphasic tensile and compressive responses of articular cartilage.

A long-standing challenge in the biomechanics of connective tissues (e.g., articular cartilage, ligament, tendon) has been the reported disparities between their tensile and compressive properties. In general, the intrinsic tensile properties of the solid matrices of these tissues are dictated by the collagen content and microstructural architecture, and the intrinsic compressive properties are dictated by their proteoglycan content and molecular organization as well as water content. These distinct materials give rise to a pronounced and experimentally well-documented nonlinear tension-compression stress-strain responses, as well as biphasic or intrinsic extracellular matrix viscoelastic responses. While many constitutive models of articular cartilage have captured one or more of these experimental responses, no single constitutive law has successfully described the uniaxial tensile and compressive responses of cartilage within the same framework. The objective of this study was to combine two previously proposed extensions of the biphasic theory of Mow et al. [1980, ASME J. Biomech. Eng., 102, pp. 73-84] to incorporate tension-compression nonlinearity as well as intrinsic viscoelasticity of the solid matrix of cartilage. The biphasic-conewise linear elastic model proposed by Soltz and Ateshian [2000, ASME J. Biomech. Eng., 122, pp. 576-586] and based on the bimodular stress-strain constitutive law introduced by Curnier et al. [1995, J. Elasticity, 37, pp. 1-38], as well as the biphasic poroviscoelastic model of Mak [1986, ASME J. Biomech. Eng., 108, pp. 123-130], which employs the quasi-linear viscoelastic model of Fung [1981, Biomechanics: Mechanical Properties of Living Tissues, Springer-Verlag, New York], were combined in a single model to analyze the response of cartilage to standard testing configurations. Results were compared to experimental data from the literature and it was found that a simultaneous prediction of compression and tension experiments of articular cartilage, under stress-relaxation and dynamic loading, can be achieved when properly taking into account both flow-dependent and flow-independent viscoelasticity effects, as well as tension-compression nonlinearity.

Animals↗

PubMed2005

Optic nerve compression by normal carotid artery in patients with normal tension glaucoma.

AIM: To determine whether compression of the optic nerve by the intracranial carotid artery (ICA) can be a causative factor of normal tension glaucoma (NTG). METHODS: The medical records of 103 eyes of 54 Japanese patients with NTG and 104 eyes of 52 age matched control patients were reviewed. The neuroradiological findings of magnetic resonance images (MRI) were evaluated to determine the relation between the optic nerve and ICA. The clinical characteristics and general medical conditions, such as diabetes and systemic hypertension, were also compared between the two groups. RESULTS: The prevalence of optic nerve compression by the ICA in patients with NTG was 49.5%, which was significantly higher than that in control group with 34.6% (p = 0.035). Bilateral compression of the optic nerve was detected in 22 patients with NTG (40.7%), and this was also significantly higher (p = 0.029) than that in the control group (11 patients, 21.2%). In the NTG group, eyes with cup/disc ratio (C/D ratio) > or =0.7 showed a higher percentage of compression (52.6%) compared with eyes with C/D ratio of <0.7 (12.5%; p = 0. 042). The presence of diabetes and hypertension did not affect the incidence of optic nerve compression by ICA significantly. CONCLUSIONS: The significantly higher percentage of NTG patients who had optic nerve compression by the ICA suggests that compression of the optic nerve by ICA may be a possible causative factor or a risk factor for optic nerve damage in some patients with NTG.

Adult↗

PubMed2006

Increased sympathetic nerve activity correlates with neurovascular compression at the rostral ventrolateral medulla.

We used microneurography to measure muscle sympathetic nerve activity (MSNA) in 25 hypertensive subjects and correlated these results with the presence or absence of signs of neurovascular compression (NVC) at the rostral ventrolateral (RVL) medulla on MRI. Subjects were divided into 3 groups based on MRI findings: NVC-, no MRI evidence of NVC (N=9); NVC+contact, image showing artery in contact but not compressing the RVL medulla (N=8); and NVC+compression, image showing arterial compression of the RVL medulla (N=8). The MSNA measurements were performed at rest, after a hypothermic stimulus, and during isometric exercise. The MSNA during rest in the NVC+compression group was significantly higher than that in the NVC+contact and NVC- groups (30.4+/-3.4 versus 17.5+/-1.1 and 21.4+/-3.2 spikes per minute, respectively). However, the blood pressure in the NVC+compression group was slightly but not significantly higher than that in the other 2 groups (183+/-7/115+/-8, 174+/-6/108+/-7, and 171+/-5/110+/-5 mm Hg, respectively). The increases in MSNA, blood pressure, and heart rate during the cold pressor and isometric exercise tests were similar. Our results show that, although resting MSNA is elevated in patients with true NVC of the RVL medulla, patients without NVC or with arterial contact but not overt compression of the RVL medulla have similar MSNA. These findings are important for identifying, among hypertensive patients with NVC, individuals who may have associated physiological repercussions, such as increased sympathetic activity.

Adult↗

PubMed1997

Hyperactive pectoralis reflex as an indicator of upper cervical spinal cord compression. Report of 15 cases.

Myelopathy from cervical spondylosis is often accompanied by hyperreflexia of the upper-extremity deep tendon reflexes (DTRs). Reflexes such as the pectoralis jerk and the deltoid jerk may only be apparent in the context of hyperreflexia. Although the nerve roots involved in the reflex arcs are well described, levels of cervical spinal cord compression that lead to the hyperreflexia are not as clear. This is of particular significance for patients with multilevel cervical spondylosis in determining the levels responsible for their symptoms. The authors examined 15 consecutive patients who presented for treatment of cervical myelopathy. The clinical examination was then correlated with levels of cervical spinal cord compression by cervical magnetic resonance imaging or computerized tomography with intrathecal contrast enhancement. The presence of a prominent pectoralis jerk was seen only in patients with spinal cord compression at the C2-3 and/or C3-4 levels (nine patients). No patient with compression at or below the C4-5 disc space without coexisting compression at a higher level had hyperactive pectoralis reflexes. This association between the C3-4 level and a hyperactive pectoralis reflex was significant (p < 0.004, Fisher's exact test). The deltoid reflex was tested in the last nine consecutive patients. It was present in patients with compression of the upper spinal cord at levels C3-4 and C4-5 (four of five patients) but appeared in only one of four patients with compression below C4-5. This association did not attain statistical significance. The presence of a hyperactive pectoralis reflex is specific for lesions of the upper cervical spinal cord. Examination of upper-extremity DTRs may be helpful in planning the appropriate levels for surgical decompression in patients with multilevel spondylosis and myelopathy.

Humans↗

PubMed1998

Hemifacial spasm caused by vascular compression of the distal portion of the facial nerve. Report of seven cases.

It is generally accepted that hemifacial spasm (HFS) and trigeminal neuralgia are caused by compression of the facial nerve (seventh cranial nerve) or the trigeminal nerve (fifth cranial nerve) at the nerve's root exit (or entry) zone (REZ); thus, neurosurgeons generally perform neurovascular decompression at the REZ. Neurosurgeons tend to ignore vascular compression at distal portions of the seventh cranial nerve, even when found incidentally while performing neurovascular decompression at the REZ of that nerve, because compression of distal portions of the seventh cranial nerve has not been regarded as a cause of HFS. Recently the authors treated seven cases of HFS in which compression of the distal portion of the seventh cranial nerve produced symptoms. The anterior inferior cerebellar artery (AICA) was the offending vessel in five of these cases. Great care must be taken not to stretch the internal auditory arteries during manipulation of the AICA because these small arteries are quite vulnerable to surgical manipulation and the patient may experience hearing loss postoperatively. It must be kept in mind that compression of distal portions of the seventh cranial nerve may be responsible for HFS in cases in which neurovascular compression at the REZ is not confirmed intraoperatively and in cases in which neurovascular decompression at the nerve's REZ does not cure HFS. Surgical procedures for decompression of the distal portion of the seventh cranial nerve as well as decompression at the REZ should be performed when a deep vascular groove is noticed at the distal site of compression of the nerve.

Adult↗

PubMed2004

Closed reduction vertebroplasty for the treatment of osteoporotic vertebral compression fractures. Technical note.

The purpose of this study was to determine the efficacy and feasibility of closed reduction vertebroplasty for the treatment of osteoporotic vertebral compression fractures. Two hundred consecutive patients (183 women and 17 men) with single-level osteoporotic vertebral compression fracture were included in this study. After induction of general anesthesia, the patient was placed prone on an operating table. Closed reduction of the fractured and kyphotic spine was achieved by extending the table to restore the kyphotic angle and vertebral body (VB) height. Percutaneous vertebroplasty was then performed to treat the fractured vertebra. The results were quantitatively evaluated, according to the concept of estimated VB height. The anterior, middle, and posterior VB heights of the fractured vertebra were measured preoperatively and immediately after surgery by studying plain standing lateral radiographs. In 162 (81%) of the compression fractures the anterior VB height was restored (57.1 +/- 24.8% of lost anterior VB height); in 152 (76%) of the compression fractures the middle VB height was restored (61.4 +/- 20.6% of lost middle VB height); and in 52 (26%) of the compression fractures the posterior VB height was restored (51.3 +/- 23.1% of lost posterior VB height). In 141 (71.5%) of the compression fractures kyphosis was corrected by 12.5 +/- 3.8 degrees [mean 61.6 +/- 23.7%]). Closed reduction vertebroplasty is an efficacious and simple method in the treatment of osteoporotic vertebral compression fracture and was able to restore the VB height and kyphotic angle in postions of fractured vertebrae. Its associated, long-term effects on treated vertebrae, however, need further evaluation.

Aged↗

PubMed1995

Early compressive strength and phase-formation of dental amalgam.

The compressive strength of five different amalgams was measured at one hour, six hours, 24 hours, and seven days, and X-ray diffraction analysis was carried out for each amalgam at the same times in order to investigate the early strength characteristics of the amalgams in relation to the formation of different phases. At 24 hours all tested amalgams reached about 90% or more of their seven-day compressive strength, but the increase in the early compressive strength from one hour to 24 hours varied between different amalgams. Two of the five amalgams tested reached about 90% of their seven-day compressive strength at six hours. A significant correlation was found between the ratio of early compressive strength to seven-day compressive strength, and the X-ray diffraction intensity ratio (ratios of one-, six- and 24 hour intensity to seven-day intensity) for the gamma 1 phase, indicating that the increases in early compressive strength are mainly dependent upon the formation of gamma 1.

Analysis of Variance↗

PubMed1999

Facial nerve injury caused by vestibular Schwannoma compression: severity and adaptation to maintain normal clinical facial function.

OBJECTIVES: To assess facial nerve injury caused by vestibular Schwannoma compression and the adaptive ability of the nerve/muscle complex to maintain normal clinical facial function. STUDY DESIGN: Prospective study. SETTING: Tertiary referral centre. PATIENTS: Thirty-four patients undergoing translabyrinthine resection of vestibular schwannoma. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURES: Facial nerve action potential (FNAP) amplitude recorded at the second genu enables direct assessment of motoneuron function. Comparison of FNAP amplitudes to stimulation proximal and distal to tumor compression allows calculation of motoneuron conduction block across the site of tumor compression. Recordings performed before tumor dissection from the facial nerve reflects nerve injury caused by vestibular Schwannoma compression alone. Comparison of compound muscle action potential (CMAP) amplitudes to stimulation proximal and distal to tumor compression measures motoneuron conduction block and compensatory collateral sprouting at the nerve/muscle interface. Comparison of FNAP and CMAP data demonstrates the extent of collateral sprouting, which helps maintain normal clinical facial function. RESULTS: Normal clinical facial function is maintained when only 10% of functioning motoneurons are active. The facial nerve is highly susceptible to tumor compression with significant motoneuron injury occurring with all sizes of tumors. Motoneuron injury correlates with tumor size but with exceptions. Collateral sprouting maintains muscle function despite severe motoneuron injury. There is a significant decrease in muscle function when >80% of functioning motoneurons are in conduction block. CONCLUSIONS: The facial nerve is highly susceptible to vestibular Schwannoma compression. Collateral sprouting of active functioning motoneurons reinnervate denervated muscle fibers so maintaining muscle function and therefore clinical facial function.

Adaptation, Physiological↗

PubMed2002

[Ulnar-side wrist pain unduced by the compression of the dorsal branch of the ulnar nerve: anatomical and clinical study].

OBJECTIVES: To investigate anatomical mechanism of the ulnar wrist pain caused by the compression of the dorsal branch of the ulnar nerve, and discuss the diagnosis and treatment of the compression. METHODS: 40 sides of the upper extremities of adult cadavers were studied anatomically. The dorsal branch of the ulnar nerve and its relationship to the surroundings was dissected and observed grossly and microscopically. 13 cases of the compression of the dorsal branch of the ulnar nerve were treated and followed up. RESULTS: The dorsal branch of the ulnar nerve was penetrated from the deep of the flexor carpi ulnaris muscle 5.6 approximately 6.8 cm proximally from the styloid process of the ulna, then ran along the ulna and divided into 2 approximately 3 big branches at the medial side of the head of the ulna. The transverse branch was apt to injury during wrist movement as it crossed or rounded the head of the ulna where it was close to the peristeam. Seven of 13 cases of the compression of the dorsal branch of the ulnar nerve were treated by local block, and 6 by surgical neurolysis. Nine cases of this group got showed good effect without recurrence after 4 months to 1 year follow-up. CONCLUSION: The anatomical basis of the compression of the dorsal branch of the ulnar nerve is repetitive traction to this nerve during wrist movement, and the compression of the transverse branch is the main cause of ulnar wrist pain. The compression of the dorsal branch of the ulnar nerve should be considered to the patients with ulnar wrist pain and abnormal sensation along the dorsal ulnar side of hand.

Adult↗