Comparison of Spasticity in Spinal Cord Injury and Stroke Patients Using Reflex Period in Pendulum Test.

Spasticity is a motor impairment present in patients with both stroke and spinal cord injury. In this research, the results from the Wartenberg pendulum test, performed on stroke and spinal cord injury patients using goniometers and electromyogram recordings of the quadriceps, were reviewed and a new parameter to quantify spasticity was extracted. The Reflex Period (RP) of the pendulum test was defined as the time span from 50% of the maximum velocity of the leg swing to the activation of muscle contraction in the quadriceps, determined from the EMG. The results suggest that the reflex period in stroke patients is generally shorter than in those suffering from spinal cord injury.

Preferential activation of small cutaneous fibers through small pin electrode also depends on the shape of a long duration electrical current.

BACKGROUND: Electrical stimulation is widely used in experimental pain research but it lacks selectivity towards small nociceptive fibers. When using standard surface patch electrodes and rectangular pulses, large fibers are activated at a lower threshold than small fibers. Pin electrodes have been designed for overcoming this problem by providing a higher current density in the upper epidermis where the small nociceptive fibers mainly terminate. At perception threshold level, pin electrode stimuli are rather selectively activating small nerve fibers and are perceived as painful, but for high current intensity, which is usually needed to evoke sufficient pain levels, large fibers are likely co-activated. Long duration current has been shown to elevate the threshold of large fibers by the mechanism of accommodation. However, it remains unclear whether the mechanism of accommodation in large fibers can be utilized to activate small fibers even more selectively by combining pin electrode stimulation with a long duration pulse. RESULTS: In this study, perception thresholds were determined for a patch- and a pin electrode for different pulse shapes of long duration. The perception threshold ratio between the two different electrodes was calculated to estimate the ability of the pulse shapes to preferentially activate small fibers. The perception threshold ratios were compared between stimulation pulses of 5- and 50 ms durations and shapes of: exponential increase, linear increase, bounded exponential, and rectangular. Qualitative pain perception was evaluated for all pulse shapes delivered at 10 times perception threshold. The results showed a higher perception threshold ratio for long duration 50 ms pulses than for 5 ms pulses. The highest perception threshold ratio was found for the 50 ms, bounded exponential pulse shape. Results furthermore revealed different strength-duration relation between the bounded exponential- and rectangular pulse shapes. Pin electrode stimulation at high intensity was mainly described as "stabbing", "shooting", and "sharp". CONCLUSION: These results indicate that long duration pulses with a bounded exponential increase preferentially activate the small nociceptive fibers with a pin electrode and concurrently cause elevated threshold of large non-nociceptive fibers with patch electrodes.

CT and MRI Assessment and Characterization Using Segmentation and 3D Modeling Techniques: Applications to Muscle, Bone and Brain.

This paper reviews the novel use of CT and MRI data and image processing tools to segment and reconstruct tissue images in 3D to determine characteristics of muscle, bone and brain. This to study and simulate the structural changes occurring in healthy and pathological conditions as well as in response to clinical treatments. Here we report the application of this methodology to evaluate and quantify: 1. progression of atrophy in human muscle subsequent to permanent lower motor neuron (LMN) denervation, 2. muscle recovery as induced by functional electrical stimulation (FES), 3. bone quality in patients undergoing total hip replacement and 4. to model the electrical activity of the brain. Study 1: CT data and segmentation techniques were used to quantify changes in muscle density and composition by associating the Hounsfield unit values of muscle, adipose and fibrous connective tissue with different colors. This method was employed to monitor patients who have permanent muscle LMN denervation in the lower extremities under two different conditions: permanent LMN denervated not electrically stimulated and stimulated. Study 2: CT data and segmentation techniques were employed, however, in this work we assessed bone and muscle conditions in the pre-operative CT scans of patients scheduled to undergo total hip replacement. In this work, the overall anatomical structure, the bone mineral density (BMD) and compactness of quadriceps muscles and proximal femoral was computed to provide a more complete view for surgeons when deciding which implant technology to use. Further, a Finite element analysis provided a map of the strains around the proximal femur socket when solicited by typical stresses caused by an implant press fitting. Study 3 describes a method to model the electrical behavior of human brain using segmented MR images. The aim of the work is to use these models to predict the electrical activity of the human brain under normal and pathological conditions by developing detailed 3D representations of major tissue surfaces within the head, with over 12 different tissues segmented. In addition, computational tools in Matlab were developed for calculating normal vectors on the brain surface and for associating this information with the equivalent electrical dipole sources as an input into the model.

Feasibility Study of a Novel Electrode Concept for a Neuroprosthesis for Augmentation of Impaired Finger Functions.

The project "Finger Rehabilitation" aims to design a neuroprosthesis with integrated electronics. The neuroprosthesis should enable spinal cord injured people, with injury at cervical vertebrae level, to increase finger mobility and activity with the use of functional electrical stimulation. The equipment is based on several integrated factors. The user has to be independent from any external help and has to be able to put it on, control the electrical stimulation and remove it by himself. The neuroprosthesis has to be both flexible and stable for the electrodes to remain firmly on the skin. In this part of the project, new electrodes which do not get stuck on the skin are described. The electrodes are small and have low impedance. A sleeve, made from glass fibres, is also described. The electrode matrices are integrated in the sleeve. The neuroprosthesis fits a patient with spinal cord injury at C5-C6. In this work, a novel electrode concept integrated in a glass fibre sleeve is tested on its ability for use in an "independent user" neuroprosthesis for finger movement rehabilitation.

Finite Element Modelling of the Femur Bone of a Subject Suffering from Motor Neuron Lesion Subjected to Electrical Stimulation.

Bone loss and a decrease in bone mineral density is frequently seen in patients with motor neuron lesion due to lack of mechanical stimulation. This causes weakening of the bones and a greater risk of fracture. By using functional electrical stimulation it is possible to activate muscles in the body to produce the necessary muscle force to stimulate muscle growth and potentially decrease the rate of bone loss. A longitudinal study was carried out on a single patient undergoing electrical stimulation over a 6 year period. The patient underwent a CT scan each year and a full three dimensional finite element model for each year was created using Mimics (Materialise) and Abaqus (Simulia) to calculate the risk of fracture under physiologically relevant loading conditions. Using empirical formulas connecting the bone mineral density to the stiffness and ultimate tensile stress of the bone, each element was assigned a unique material property, based on its density. The risk of fracture was estimated by calculating the ratio between the predicted stress and the ultimate tensile stress, should it exceed unity, failure was assumed. The results showed that the number of elements that were predicted to be at risk of failure varied between years.

Application of Acoustic-Electric Interaction for Neuro-Muscular Activity Mapping: A Review.

Acousto-electric interaction signal (AEI signal) resulting from interaction of acoustic pressure wave and electrical current field has received recent attention in biomedical field for detection and registration of bioelectrical current. The signal is very of small value and brings about several challenges when detecting it. Several observations has been done in saline solution and on nerves and tissues under controlled condition that give optimistic indication about its utilization. Ultrasound Current Source Density Imaging (UCSDI) has been introduced, that uses the AEI signal to image the current distribution. This review provides an overview of the investigations on the AEI signal and USCDI imaging that has been made, their results and several considerations on the limitations and future possibilities on using the acousto-electric interaction signal.

Muscle, tendons, and bone: structural changes during denervation and FES treatment.

OBJECTIVES: This paper describes a novel approach to determine structural changes in bone, muscle, and tendons using medical imaging, finite element models, and processing techniques to evaluate and quantify: (1) progression of atrophy in permanently lower motor neuron (LMN) denervated human muscles, and tendons; (2) their recovery as induced by functional electrical stimulation (FES); and (3) changes in bone mineral density and bone strength as effect of FES treatment. METHODS: Briefly, we used three-dimensional reconstruction of muscle belly, tendons, and bone images to study the structural changes occurring in these tissues in paralysed subjects after complete lumbar-ischiadic spinal cord injury (SCI). These subjects were recruited through the European project RISE, an endeavour designed to establish a novel clinical rehabilitation method for patients who have permanent and non-recoverable muscle LMN denervation in the lower extremities. This paper describes the use of segmentation techniques to study muscles, tendons, and bone in several states: healthy, LMN denervated-degenerated but not stimulated, and LMN denervated-stimulated. Here, we have used medical images to develop three-dimensional models and advanced imaging, including computational tools to display tissue density. Different tissues are visualized associating proper Hounsfield intervals defined experimentally to fat, connective tissue, and muscle. Finite element techniques are used to calculate Young's modulus on the patella bone and to analyse correlation between muscle contraction and bone strength changes. RESULTS: These analyses show restoration of muscular structures, tendons, and bone after FES as well as decline of the same tissues when treatment is not performed. This study suggests also a correlation between muscle growth due to FES treatment and increase in density and strength in patella bone. CONCLUSION: Segmentation techniques and finite element analysis allow the study of the structural changes of human skeletal muscle, tendons, and bone in SCI patient with LMN injury and to monitor effects and changes in tissue composition due to FES treatment. This work demonstrates improved bone strength in the patella through the FES treatment applied on the quadriceps femur.

Monitoring of muscle and bone recovery in spinal cord injury patients treated with electrical stimulation using three-dimensional imaging and segmentation techniques: methodological assessment.

Muscle tissue composition accounting for the relative content of muscle fibers and intramuscular adipose and loose fibrous tissues can be efficiently analyzed and quantified using images from spiral computed tomography (S-CT) technology and the associated distribution of Hounsfield unit (HU) values. Muscle density distribution, especially when including the whole muscle volume, provides remarkable information on the muscle condition. Different physiological and pathological scenarios can be depicted using the muscle characterization technique based on the HU values and the definition of appropriate intervals and the association of such intervals to different colors. Using this method atrophy, degeneration, and restoration in denervated muscle undergoing electrical stimulation treatments can be clearly displayed and monitored. Moreover, finite element methods are employed to calculate Young's modulus on the patella bone and to analyze correlation between muscle contraction and bone strength changes. The reliability of this tool though depends on S-CT assessment and calibration. To assess imaging quality and the use of HU values to display muscle composition, different S-CT devices are compared using a Quasar body scanner. Density distributions and volumes of various calibration elements such as lung, polyethylene, water equivalent, and trabecular and dense bone are measured with different scanning protocols and at different points of time. The results show that every scanned element undergoes HU variations, which are greater for materials at the extremes of the HU scale, such as dense bone and lung inhale. Moreover, S-CT scanning with low tube voltages (80 KV) produces inaccurate HU values especially in bones. In conclusion, 3-D modeling techniques based on S-CT scanning is a powerful follow-up tool that may provide structural information at the millimeter scale, and thus may drive choice and timing to validate rehabilitation protocols.

Quantitative color three-dimensional computer tomography imaging of human long-term denervated muscle.

OBJECTIVES: A new non-invasive method was developed to analyse macroscopic and microscopic structural changes of human skeletal muscle based on processing techniques of medical images, here exemplified by monitoring progression and recovery of long-term denervation by home based functional electrical stimulation. METHODS: Spiral computer tomography images and special computational tools were used to isolate the quadriceps muscles and to make three-dimensional reconstructions of denervated muscles. Shape, volume and density changes were quantitatively measured on each part of the quadriceps muscle. Changes in tissue composition within the muscle were visualized associating Hounsfield unit values of normal or atrophic muscle, fat and connective tissue to different colors. The minimal volumetric element (voxel) is approximately ten times smaller than the volume analysed by needle muscle biopsy. The results of this microstructural analysis are presented as the percentage of different tissues (muscle, loose and fibrous connective tissue, and fat) in the total volume of the rectus muscle and displaying the first cortical layer of voxels that describe the muscle epimysium directly on the muscle three-dimensional reconstruction. RESULTS: In normal and paraplegic patients, this new monitoring approach provides information on macroscopic shape, volume, and the increased adipose and fibrous tissue content within the denervated muscle. In particular, the change displayed at epimysium level is structurally important and possibly functionally relevant. Here we show that muscle restoration induced by homebased functional electrical stimulation is documented by the increase in normal muscle tissue from 45 to 60% of the whole volume, while connective tissue and fat are reduced of 30 and 50% with respect to the pre-treatment values. These changes are in agreement with the muscle biopsy findings, and self-evident when epimysium thickness is depicted. CONCLUSION: Color three-dimensional imaging of human skeletal muscle is an improved computational approach of non-invasive medical imaging able to detect not only macroscopic changes of human muscle volume and shape, but also their tissue composition at microscopic level.

Restoration of muscle volume and shape induced by electrical stimulation of denervated degenerated muscles: qualitative and quantitative measurement of changes in rectus femoris using computer tomography and image segmentation.

This study demonstrates in a novel way how volume and shape are restored to denervated degenerated muscles due to a special pattern of electrical stimulation. To this purpose, Spiral Computer Tomography (CT) and special image processing tools were used to develop a method to isolate the rectus femoris from other muscle bellies in the thigh and monitor growth and morphology changes very accurately. During 4 years of electrical stimulation, three-dimensional (3D) reconstructions of the rectus femoris muscles from patients with long-term flaccid paraplegia were made at different points in time. The growth of the muscle and its changes through the time period are seen in the 3D representation and are measured quantitatively. Furthermore, changes in shape are compared with respect to healthy muscles in order to estimate the degree of restoration. The results clearly show a slow but continuing muscle growth induced by electrical stimulation; the increase of volume is accompanied by the return of a quasi-normal muscle shape. This technique allows a unique way of monitoring which provides qualitative and quantitative information on the denervated degenerated muscle behavior otherwise hidden.

Monitoring muscle growth and tissue changes induced by electrical stimulation of denervated degenerated muscles with CT and stereolithographic 3D modeling.

In the frame of the EU-funded RISE project, patients with lower motor neuron lesion and denervated and degenerated muscles are treated with electrical stimulation, with the aim of restoring muscle mass and force. Spiral computer tomography from the hip joint down to the knee joint is used to gather three-dimensional data on the upper leg tissue. These data are analyzed in order to monitor tissue changes induced by the electrical stimulation treatment. Especially the data representing muscle tissue and bone tissue were isolated for measurement purposes. Computer models and models made with rapid prototyping methods were used to display and demonstrate changes in muscle shape and size, as well as position relative to bone. Results showed that time and spatial dependencies of muscle growth can be monitored and studied quantitatively and qualitatively with the aid of a three-dimensional data set displayed on the computer screen or in the form of plastic models. These first results indicate muscle growth and an increase in bone density.