Peripheral nerve stimulation by time-varying magnetic fields

PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation.     

Radial echo-planar imaging

A new ultrafast magnetic resonance imaging pulse sequence named radial echo-planar imaging (rEPI) is introduced. The sequence is based on a modification of the echo-planar imaging (EPI) sequence to scan k-space radially, in an attempt to combine the speed of EPI with the benefits of radial sampling. Like in EPI, all the desired lines in k-space are scanned consecutively in opposite directions. The unique feature of this new sequence, however, is that the orientation of the readout gradient is incrementally rotated, so that all the echoes are refocused through the center of k-space. Therefore, rEPI data are acquired in a polar grid, and image reconstruction can be done either by means of filtered back-projection or by regridding the data to a Cartesian matrix followed by 2D Fourier transform. First results show that rEPI images can be acquired with the same speed and signal-to-noise ratio of EPI images. rEPI images are also shown to be less sensitive to off-resonance effects than EPI images. Further studies are underway to investigate the usefulness of rEPI for spectroscopic imaging and applications affected by motion.     

In vivo echo-planar imaging of rat spinal cord

An integrated approach to echo-planar imaging of rat spinal cord in vivo with a small field of view (FOV) is presented. This protocol is based on a multishot interleaved echo-planar imaging (EPI) sequence and includes: 1) use of an inductively coupled implantable coil for improved signal-to-noise ratio (SNR); 2) three-dimensional (3D) automatic shimming of the magnetic field over the spinal cord; and 3) post-acquisition data processing using a multireference scan for minimizing image artifacts. Some of the practical issues in implementing this protocol are discussed. This imaging protocol will be useful in characterizing the spinal cord pathology using techniques that are otherwise time-consuming, such as diffusion tensor imaging.     

Peripheral nerve hemangioblastoma

Capillary hemangioblastoma (HB) is a benign, highly vascular tumor limited almost exclusively to the central nervous system (CNS). It occurs primarily in the posterior fossa and less often in the spinal cord. We report three cases of HB occurring in peripheral nerve, two intradural tumors arising in a C4 and a cauda equina nerve root, respectively, and a third lesion in the sciatic nerve at mid thigh. The patients, 1 woman and 2 men, ranged in age from 25 to 49 years. Two had von Hippel-Lindau disease, an association usually found in one-third of CNS HBs, and one had a family history of pheochromocytoma. In every way, HBs of peripheral nerve were indistinguishable from their CNS counterpart. Ranging in size from 1.5 to 5.5 cm in diameter, the tumors were well circumscribed and contained a myriad of small caliber vessels lined by endothelial cells and surrounded by pericytes. Throughout, the lesions were rich in large, often vacuolated stromal cells. In all of the cases, these stained strongly for vimentin and neuron-specific enolase; only one showed focal S100 protein reactivity. Surgical therapy required excision of the affected nerve roots in the first two cases. In the third case, prominent extension of the tumor within epineurium permitted a microsurgical resection with sparing of sciatic nerve fascicles. No tumor recurred during a follow-up period of 5 to 20 months.     

Gradient moment smoothing: a new flow compensation technique for multi-shot echo-planar imaging

This work identifies an additional source of phase error across ky in multi-shot echo-planar imaging resulting from flow or motion along the phase-encoding direction. A velocity-independent flow compensation technique, gradient moment smoothing, is presented that corrects this error by forcing the phase to have smooth quadratic behavior. The correction is implemented, without compromising scan time, by changing the first moment of a bipolar prephaser pulse on a shot-by-shot basis. In phantom and in vivo experiments, gradient moment smoothing effectively eliminates ghosting and signal loss due to phase-encoding flow. When used in conjunction with a "flyback" echo-planar readout, which compensates for flow in the frequency-encoding direction, gradient moment smoothing renders multi-shot echo-planar imaging relatively insensitive to in-plane flow. This can make multi-shot echo-planar imaging a viable technique for accurately imaging in-plane flow and may desensitize it to the otherwise serious problem of in-plane motion.     

Functional magnetic resonance imaging of median nerve stimulation in rats at 2.0 T

A cDNA clone, called CLB1, was isolated from a cDNA library from tomato (Lycopersicon esculentum) and characterized. The CLB1 cDNA contains an open reading frame of 1518 bp, and encodes a putative protein of 506 amino acids with a predicted molecular mass of 54,633 Da. The deduced CLB1 amino acid sequence contains a domain that exhibits from 26% to 37% identity with the Ca2+-dependent lipid-binding domains of cytosolic phospholipase A2, protein kinase C, Rabphilin-3A, and Synaptotagmin 1 of animals. Southern blot analysis indicates that the CLB1 gene belongs to a small gene family in the tomato genome. The CLB1 mRNA is preferentially expressed in fruit tissues.     

Peripheral nerve revascularization: a current literature review

Gene therapy of human cancer is likely to be most effective when it is directed at targets that are expressed in cancer cells but are lacking from other cells. Human papillomaviruses can provide such targets, since these viruses are present in many cervical and oral cancers, and are likely to be etiological agents of the tumor. Continued expression of human papillomavirus genes is probably necessary for the growth of these cancers, and effective gene therapy could consist of antisense or ribozyme molecules directed against these genes. Some human papillomavirus gene products are antigenic, and immunotherapy based upon these antigens might prove clinically beneficial. Human papillomaviruses have specific promoters, are linked to toxin genes, the toxin may be selectively expressed by tumor cells where the virus genes are active. Thus, there are several approaches for the development of specific gene therapy for human cancers that contain human papillomaviruses.     

Segmented three-dimensional echo-planar flow imaging of the cervical carotid arteries

PURPOSE: To implement and assess the application of segmented three-dimensional echo-planar MR imaging time-of-flight flow sequences for studying the anatomy of the cervical carotid arteries at 1.5 T. METHODS: The 3-D echo-planar sequences were segmented along the in-plane phase-encoding direction. Echo train lengths (ETLs) of 3 and 5 and signal bandwidths of +/-25, +/-33, and +/-50 KHz were tested along with a conventional (ETL = 1) 3-D MR flow study in six healthy volunteers and in five patients with known arteriosclerotic disease involving the carotid bifurcation as confirmed by conventional angiography. The volunteer data were used to rank the techniques with respect to vessel dimension, vessel/background contrast, and quality by four trained neuroradiologists. For the patient studies, the percentage of stenoses was measured for all MR studies and compared against the conventional angiographic data using the criteria of the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: Using Wilcoxon's test statistic and a significance level of .05, we found that the conventional MR flow examination was better than the segmented techniques and that the segmented techniques with ETL of 3 were superior to their counterparts with ETL of 5. For the ETL of 3 techniques, the high-bandwidth studies were inferior to their lower bandwidth counterparts; however, there was no significant difference between the performance of the medium- and low-bandwidth sequences. The patient data revealed that the segmented techniques consistently overestimated the severity of stenosis; however, in no instance did any of the segmented examinations erroneously indicate the presence of disease. CONCLUSIONS: The reduction in acquisition time and the zero false-positive rate we obtained suggest that segmented 3-D echo-planar MR flow techniques may be used as a screening/locating study for cervical carotid artery disease.     

Motion and deformation tracking for short-axis echo-planar myocardial perfusion imaging

Aggression research does not lack data--it lacks a model for integrating data. One of the problems confronting aggression researchers is the extensive body of multidisciplinary data that is difficult to synthesize to generate new directions in research. This paper proposes one solution that starts by asking "what is the minimal number of categories of concepts and measurements which are necessary to describe a person?". The answer is four categories of concepts: biological; cognitive; behavioral; environmental (physical and social). One way of many for integrating these four categories of concepts is a proposed discipline neutral heuristic model that is used herein to compare two different research approaches to the study of impulsive aggression. This comparison identifies clearly the differences in the two approaches with regard to different emphases among the four categories of constructs for each program. Using the model an example of common ground between the two approaches is sought as a basis for extending aggression research. The main conclusion of one of the research programs was that central nervous arousal is related to impulsive aggression. This program demonstrated that phenytoin will reduce impulsive aggressive acts and has an effect on CNS arousal. The other research program on impulsive aggression has been at the forefront in demonstrating the well established inverse relationship between serotonin levels and aggression. The comparison resulted in the suggestion that both serotonin and phenytoin may relate to a common neurochemical substrate which interacts in part to control CNS arousal, especially at the cortical level. The proposed heuristic model made obvious the need to use synthesizing concepts (e.g. information processing or language) which can interrelate multidisciplinary concepts and data from different research programs within the four categories of constructs when comparing interdisciplinary research.     

Increased-contrast, high-spatial-resolution, diffusion-weighted, spin-echo, echo-planar imaging

An insertable head gradient coil with a maximum gradient amplitude of 45 mT/m and a rise time of 150 musec along all three major axes was used to collect high-spatial-resolution, single-shot, spin-echo, echo-planar, diffusion-weighted magnetic resonance images with b values ranging from 0 to 2,200 sec/mm2. Improvements in spatial resolution allowed better visualization of large white matter tracts and their relation to adjacent anatomic structures. Excellent contrast and anatomic detail were revealed for most structures in the brain when a sufficient number of acquisitions were collected.     

Peripheral nerve entrapment in Paget''s disease

Thirteen anthropometric measurements of Kaffa district schoolchildren in Ethiopia were factor analysed. Two factors emerged which may be interpreted as (a) body size and (b) fat mass.     

Peripheral nerve injury as a complication from orthopedic operation

We report a case of pulmonary carcinosarcoma. Surgery is required for this rare mixed type, biphasic tumor. It is generally considered to be a malignant formation issuing from a single cell line but with a two-way differentiation into epithelial and conjunctive components. There is a differentiation continuum between spindle-cell carcinomas (also called monophasic sarcomatoid carcinoma) and carcinosarcoma (or biphasic sarcomatoid carcinoma) leading to debate concerning the immunohistochemical and ultrastructural features.     

Peripheral nervous system involvement in systemic sclerosis: the median nerve as target structure

The differential diagnosis of cutaneous small round cell malignancies is a relatively uncommon but recurrent problem that usually requires adjuvant techniques including special histochemical stains, immunohistochemistry (IHC), electron microscopy (EM), and cytogenetics (CG) to arrive at a definite answer. This report describes a case of a primary cutaneous malignancy that, after workup, fulfilled the criteria of extraskeletal Ewing's family sarcoma, which was corroborated by IHC with an antibody to glycoprotein p30/32 mic2 that is highly expressed in these neoplasms. The lesions consisted of a large nodular proliferation of poorly differentiated monotonous small round cells confined to the dermis and subcutaneous tissue. The cells had high nuclear to cytoplasmic (N/C) ratios, scattered prominent nucleoli, and indistinct cytoplasm. A periodic acid-Schiff (PAS) stain with and without diastase demonstrated abundant cytoplasmic glycogen. The glycogen was confirmed with EM, which did not show neurosecretory granules, but extensive sectioning of the tissue blocks demonstrated with light microscopy a single focus with pseudorosette formation. IHC was positive for monoclonal antibody (MAb) O13 to glycoprotein p30/32 mic2 and negative for lymphoid (CD45), neural (S-100, NF, GFAP), neuroendocrine (NSE), and muscle (MSA, desmin) markers. To the best of our knowledge, this is one of few reported cases of primary cutaneous (extraskeletal/extraosseous) Ewing's sarcoma (EEWS) and the first to use IHC with MAb O13, which recognizes the cell surface glycoprotein p30/32 mic2. This case further illustrates the continuum between EEWS and primitive peripheral neuroepithelioma and supports the unifying concept that these two entities are merely subtle morphologic variants of the same malignant neoplasm, which is better designated a Ewing's family sarcoma.     

Peripheral nerve disorders--clinical pathological approaches]

Clinical pathological approach is defined as combination of neurological, neurophysiological and neuroradiological findings for the interpretation of the morphology of the sural nerve. For this purpose, first, the usefulness of simultaneous biopsy of sural nerve and ipsilateral short peroneal muscle was presented. This method has helped establish the diagnosis of angitis or amyloidosis in some cases. Furthermore, motor-dominant clinical picture was ascertained by relative preservation of sural nerve in contrast with severe changes in intramuscular nerve fascicles. Second, histochemistry using UEA-1 lectin to detect somatic sensory C fibers was discussed. UEA-1 specifically binds to unmyelinated axons and small neurons in dorsal root ganglia as well as substantia gelatinosa of the spinal cord. Serial semithin and ultrathin sections were obtained. The semithin section was removed of epon and stained histochemically with UEA-1. Positive fibers in the semithin section was compared with the counterpart in the ultrathin sections. UEA-1 positive fibers were found to comprise 20% of all unmyelinated fibers and be randomly distributed among the entire nerve fascicles. The application of this technique to pathological specimens is now undergoing. Third, an autopsy case with sarin intoxication was reported as an example of systemic study of the peripheral nervous system. The patient was a 51-year-old man who inhaled sarin in the attack of Tokyo Subway. He fell into vegetative state and was passively maintained for 13 months. Peripheral sensory nerve showed typical pattern of dying back-type distal peripheral axonopathy. It might be indicated that peripheral nerve be carefully checked among the sarin victims. In conclusion, the aim of our approach is to combine all clinical information, introduce recent advance in neuroscience, and try to find possible cure to intractable neurological disorders.     

Peripheral nerve vascular changes in spontaneously hypertensive rats

Circulation to the brain is affected by hypertension. Hypertension-dependent cerebrovascular changes were documented primarily in brain pial arteries, whereas no information is so far available concerning changes of peripheral nerve vascularization in hypertension. This study was designed to assess the occurrence of structural changes of interfascicular and intrafascicular arteries supplying peripheral nerves (the so called vasa nervorum) in spontaneously hypertensive rats (SHR). The investigation was performed in 8-month-old SHR, by using standard microanatomical techniques associated with quantitative image analysis. In SHR a significant increase of systolic pressure values accompanied by thickening of the arterial wall, narrowing of the lumen and increase of the wall-to-lumen ratio were observed in comparison with age-matched normotensive Wistar-Kyoto rats. Hypertension-related structural changes involved primarily interfascicular arteries and to a lesser extent intrafascicular arteries. These findings indicate that similarly as documented for cerebral arteries, the vascular supply to peripheral nerves is impaired in hypertension. Structural changes of interfascicular and intrafascicular arteries of SHR could lead to ischemia of peripheral nerves. Further work is in progress to evaluate the functional relevance of hypertensive changes to peripheral nerve vasculature.     

Vagus nerve stimulation for intractable epilepsy: a review

Electrical stimulation of the vagus nerve in the neck by using a programmable stimulator similar to a cardiac pacemaker is being explored as a treatment for epilepsy. There is sound rationale based on studies of animal seizure models for pursuing this treatment modality, and early clinical trials provide support for efficacy in patients with intractable epilepsy at least equivalent to that of some of the new antiepileptic drugs. Safety and tolerability have been demonstrated in >800 patients worldwide since the first implant in 1988. Most of these had partial seizures for which resective epilepsy surgery was not feasible or had failed, but efficacy of vagal stimulation appears to be the same for both partial and generalized epilepsy. Specific selection criteria for this procedure have yet to be established, and further studies are warranted to determine whether vagal stimulation becomes an accepted procedure for epilepsy management.     

Aspiration: a potential complication to vagus nerve stimulation

PURPOSE: Vagus nerve stimulation (VNS) is reported to reduce the frequency of seizures in children and adults without causing serious side effects. However, clinical observation of swallowing difficulties in 2 children treated with VNS made further investigation necessary. METHODS: Seven patients aged 4-18 years and treated with VNS for 6-14 months were investigated with videoradiography during barium swallow. The children performed 5-30 barium swallow investigations with the VNS device turned off, running as programmed, or set at continuous stimulations. The degree of aspiration was scored from 0 to 3. RESULTS: In 5 of 7 children, of whom reported transient swallowing difficulties, no change in the degree of aspiration was noted. The 2 children with swallowing difficulties, however. showed increased aspiration score when the stimulator was set at continuous stimulations. In 1 the score also appeared to increase with the VNS running as programmed (p > 0.05). Both children had severe mental and motor disabilities. CONCLUSIONS: Before and during VNS treatment patients should be evaluated with regard to swallowing problems. There needs to be an easy way to turn the device on and off to avoid aspirations, a hazardous and potentially life-threatening complication of VNS.