Functional MRI of the rat lumbar spinal cord involving painful stimulation and the effect of peripheral joint mobilization

Association between myofascial trigger point therapy and conditioned pain modulation

INTRODUCTION

Myofascial trigger point therapy (MTrP) is a widely used therapeutic approach, although the underlying mechanisms remain unclear. Mechanisms discussed include peripheral involvement of muscles as well as central pain modulating processes such as the conditioned pain modulation (CPM). The aim of this study was to investigate whether the analgesic response of MTrP and the analgesic response of CPM correlate in asymptomatic participants in order to identify shared underlying mechanisms of MTrP and CPM.

METHOD

Both, CPM and MTrP protocols consisted of heat-based test stimuli (heat pain thresholds before and after the intervention) and pressure-based (conditioning) stimuli. Asymptomatic participants (n = 94) were randomly assigned to receive either mild, intense or no pressure stimuli (between-group design) to both the fingernail and the MTrP of the infraspinatus muscle (within-group design). Pressure stimuli at both locations (fingernail, MTrP) were applied with a pressure algometer for 120 s and continuously adjusted to maintain a constant pain intensity of mild or intense pain. All thermal stimuli were applied on the lower leg with a thermal stimulator.

RESULTS

A significant correlation was shown between the analgesic effect of CPM and MTrP therapy for mild (r = 0.53, p = 0.002) and intensive stimuli (r = 0.73, p < 0.001). 17.3% of the variance of the MTrP effect were explained by CPM after mild stimulation, and 47.1% after intense stimulation. Pain-related characteristics did not explain the variance within the analgesic response using a regression analysis.

CONCLUSIONS

Between the analgesic responses following MTrP and CPM paradigms, a moderate to strong correlation was observed, suggesting shared underlying mechanisms.

An investigation of neurological and/or biomechanical factors underpinning the effect of a thrust manipulation on chronic ankle symptoms: an observational study

BACKGROUND

Ankle sprains are a commonly occurring musculoskeletal injury potentially resulting in persistent pain and/or altered motion. Thrust manipulation may serve as an interventional strategy but limited evidence exists on the mechanism(s) by which a change to symptoms might occur.

OBJECTIVE

The study sought to quantify the immediate effect of a thrust manipulation to the ankle to determine a mechanism by which change to symptoms occurred.

METHODS

Eleven participants (6 m/5f, 26.09 ± 4.25 yrs) with a history of ankle sprain that occurred greater than three months ago with recurring pain and/or altered motion were recruited. Participants underwent neurophysiological testing to assess any pain alterations and instrumented gait analysis (IGA) for biomechanical assessment pre-post thrust manipulation to the ankle.

RESULTS

There were no significant differences in ankle dorsiflexion (DF) (p = 0.62), plantarflexion (PF) (p = 0.23), ground reaction force (GRF), or velocity (p = 0.63) following thrust manipulation compared to baseline; however, pre- and post-data did show differences in pain pressure threshold (p = 0.046). There were no significant differences in dynamic pain measurements.

CONCLUSIONS

Ankle sprains that result in persistent pain and/or altered motion can be impacted by a thrust manipulation which appears to act through neurophysiological mechanisms.

Effects of the Addition of Hands-on Procedures to McKenzie Exercises on Pain, Functional Disability and Back Mobility in Patients with Low Back Pain: A Randomised Clinical Trial

Background

Low back pain (LBP) is a common musculoskeletal disorder that affects people of all ages. This study investigates the effects of the addition of hands-on procedures to McKenzie exercises on patients with LBP and derangement syndrome.

Methods

Forty-eight female patients were randomly assigned to either the experimental group or control group. All the patients in both groups underwent McKenzie exercises, transcutaneous electrical nerve stimulation (TENS) and education for 35 min/session-45 min/ session, with three sessions/week for 2 weeks. Hands-on procedures were added to the McKenzie extension exercises only for the patients in the experimental group. A visual analogue scale (VAS), the Oswestry disability index (ODI), back range of motion (BROM) and body diagrams were used to measure pain, functional disability, BROM and the centralisation of symptoms, respectively.

Results

The mean values of VAS, ODI and BROM significantly improved after the interventions in both groups (P < 0.05), whereas the results of repeated measures ANOVA and Mann-Whitney U tests showed statistically non-significant differences between the two groups (P > 0.05).

Conclusion

The addition of hands-on procedures to McKenzie exercises, TENS and education significantly alleviated back pain and functional disability and improved the back mobility and centralisation of symptoms in patients with LBP and derangement syndrome; however, these measures did not result in any significant additional benefits for such patients.

The Immediate Hypoalgesic Effect of Low and High Force Thoracic Mobilizations in Asymptomatic Subjects as Measured by Pain Pressure Thresholds (PPT)

Physiotherapists commonly use mobilizations for treating patients with thoracic spine pain (TSP). There is evidence to suggest that spinal mobilizations can decrease pain. Different doses of mobilization treatment are applied, however there is a paucity of evidence on the influence of these dosage parameters. The effect of different forces of treatment remains unknown. This study aimed to investigate whether there was a difference in the hypoalgesic effect of high and low force thoracic mobilizations. This single-blinded, randomized, within-subject, repeated measures, cross-over design recruited 28 asymptomatic participants. Participants received the experimental conditions of high (200 N) and low force (30 N) mobilizations to T6 at least 48 h apart. Pressure pain thresholds (PPTs) were measured before and immediately after each experimental intervention at three different standardized sites. The results demonstrated that high force thoracic mobilizations caused a significant increase in PPT measures compared to low force mobilizations. This effect was detected at all PPT sites. This study suggests that high force thoracic PA mobilizations cause a significantly greater hypoalgesic response in asymptomatic participants than low force thoracic mobilizations. The hypoalgesic response seems to be elicited not only locally at the site of the intervention, but in a widespread manner.

Comparative features of the immediate impact of manual therapy traction manipulations on the cardiorespiratory system of men and women

Purpose: the aim of this study was to determine the principal differences of changes in the cardiorespiratory system activity under the influence of traction manipulations in the thoracic spine of men and women. Material & Methods: the 26 adults were involved in the study, including 18 women aged 39.6±12.1 years and 8 men aged 36.3±8.3 years. All patients were diagnosed with osteochondrosis of the thoracic spine, which was confirmed by radiographic examination. The study of the cardiorespiratory system was conducted in the first procedure of SMT before and after the use of traction manipulations directly in the physician office. The integrated method of studying the cardiorespiratory system defined as spiroarteriocardiorhythmography (SACR) was used. It simultaneously records the heart rate, rhythms of systolic and diastolic pressure at each heartbeat and respiratory rhythms, which provides significant time savings to determine the functional state of the heart, vessels and respiration, as well as to identify the important parameters of their interaction. Results: characterizing the changes in the cardiorespiratory system as a whole under the influence of traction manipulations on the thoracic spine, it should be noted that men and women had some significant unidirectional changes in HR (min–1), CO (dm3), CI (dm3/m2), IH (n. u.), which are determined primarily by the decrease in HR (min–1) under the influence of traction manipulations. As to the men, the significant effects were more related to the impact on the contractile function of the heart, which was confirmed by the improvement of the electrical systole of the ventricles (QTC, s), the increase in the activity of the effects of the parasympathetic branch of the ANS on the cardiac rhythm (HF, ms2) and a certain increase in the stroke index within the normative values (SI, cm3/m2), then to the women the significant effects were more related to the influence on the breathing pattern and vascular tone. Thus, characteristic and positive effects in women can be considered a decrease in the variability of diastolic blood pressure in the very-low-frequency range (VLFDBP, mmHg2), which is combined with a decrease in the total power of diastolic pressure variability (TPDBP, mmHg2) and an increase in the total peripheral vascular resistance (GPVR, dyn/s/cm−5). Conclusions: summarizing the results of the impact of traction manipulations in the thoracic spine on the cardiorespiratory system of men and women, it can be stated that their effect is different and has features associated with the use of different mechanisms. For men, the predominant effect is on the heart contractile function, and for women it is on the respiratory system and autonomous regulation of vascular tone.

Large-scale functional ultrasound imaging of the spinal cord reveals in-depth spatiotemporal responses of spinal nociceptive circuits in both normal and inflammatory states

Despite a century of research on the physiology/pathophysiology of the spinal cord in chronic pain condition, the properties of the spinal cord were rarely studied at the large-scale level from a neurovascular point of view. This is mostly due to the limited spatial and/or temporal resolution of the available techniques. Functional ultrasound imaging (fUS) is an emerging neuroimaging approach that allows, through the measurement of cerebral blood volume, the study of brain functional connectivity or functional activations with excellent spatial (100 μm) and temporal (1 msec) resolutions and a high sensitivity. The aim of this study was to increase our understanding of the spinal cord physiology through the study of the properties of spinal hemodynamic response to the natural or electrical stimulation of afferent fibers. Using a combination of fUS and ultrasound localization microscopy, the first step of this study was the fine description of the vascular structures in the rat spinal cord. Then, using either natural or electrical stimulations of different categories of afferent fibers (Aβ, Aδ, and C fibers), we could define the characteristics of the typical hemodynamic response of the rat spinal cord experimentally. We showed that the responses are fiber-specific, located ipsilaterally in the dorsal horn, and that they follow the somatotopy of afferent fiber entries in the dorsal horn and that the C-fiber response is an N-methyl-D-aspartate receptor-dependent mechanism. Finally, fUS imaging of the mesoscopic hemodynamic response induced by natural tactile stimulations revealed a potentiated response in inflammatory condition, suggesting an enhanced response to allodynic stimulations.

Spinal Manipulation and Select Manual Therapies: Current Perspectives

Touch is fundamental to the doctor-patient relationship. Touch can produce neuromodulatory effects that mitigate pain and put patients at ease. Touch begins with a confident handshake and continues throughout the physical examination. Touching patients where they hurt is a clear indication that a provider understands their complaint. Touch often continues as a function of treatment. This article updates evidence surrounding human touch and addresses mechanisms of action for manual therapy, the impact of manual therapy on pain management, health care conditions for which manual therapy may be beneficial, treatment plans with dose-response evidence, and the impact of manual therapy on the health care system.

Physiological Responses Induced by Manual Therapy in Animal Models: A Scoping Review

Background: Physiological responses related to manual therapy (MT) treatment have been investigated over decades using various animal models. However, these studies have not been compiled and their collective findings appraised. The purpose of this scoping review was to assess current scientific knowledge on the physiological responses related to MT and/or simulated MT procedures in animal models so as to act as a resource to better inform future mechanistic and clinical research incorporating these therapeutic interventions.

Methods: PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane, Embase, and Index of Chiropractic Literature (ICL) were searched from database inception to August 2019. Eligible studies were: (a) published in English; (b) non-cadaveric animal-based; (c) original data studies; (d) included a form of MT or simulated MT as treatment; (e) included quantification of at least one delivery parameter of MT treatment; (f) quantification of at least one physiological measure that could potentially contribute to therapeutic mechanisms of action of the MT. MT studies were categorized according to three main intervention types: (1) mobilization; (2) manipulation; and (3) massage. Two-phase screening procedures were conducted by a pair of independent reviewers, data were extracted from eligible studies and qualitatively reported.

Results: The literature search resulted in 231 articles of which 78 met inclusion criteria and were sorted by intervention type. Joint mobilization induced changes in nociceptive response and inflammatory profile, gene expression, receptor activation, neurotransmitter release and enzymatic activity. Spinal manipulation produced changes in muscle spindle response, nocifensive reflex response and neuronal activity, electromyography, and immunologic response. Physiological changes associated with massage therapy included autonomic, circulatory, lymphatic and immunologic functions, visceral response, gene expression, neuroanatomy, function and pathology, and cellular response to in vitro simulated massage.

Conclusion: Pre-clinical research supports an association between MT physiological response and multiple potential short-term MT therapeutic mechanisms. Optimization of MT delivery and/or treatment efficacy will require additional preclinical investigation in which MT delivery parameters are controlled and reported using pathological and/or chronic pain models that mimic neuromusculoskeletal conditions for which MT has demonstrated clinical benefit.

The effects of spinal manipulative therapy on lower limb neurodynamic test outcomes in adults: a systematic review

Objective: Spinal Manipulative Therapy (SMT) is a routinely applied treatment modality for various musculoskeletal conditions, including low back pain. The precise mechanisms by which SMT elicits its effects are largely unknown, but recent research supports a multi-system explanation recognizing both biomechanical and neurophysiological mechanisms. Although the evaluation of changes in clinical presentation is complex, objective neurophysiological measures of sensitivity to movement (e.g. neurodynamic tests) can be a valuable clinical indicator in evaluating the effects of SMT. This review aimed to synthesize current literature investigating the effects of SMT on lower limb neurodynamics.Method: Eight electronic databases were systematically searched for randomized controlled trials (RCT) that applied SMT (against any control) and evaluated lower limb neurodynamics (Passive Straight Leg Raise or Slump Test). Selection and data extraction were conducted by one researcher, reviewed by a second author. Risk of bias (RoB) was assessed using the Cochrane Back Review Group criteria.Results: Eight RCTs were included, one with high RoB. SMT produced a clinically meaningful (≥6⁰) difference in five of these studies compared with inert control, hamstring stretching, and as an adjunct to conventional physiotherapy, but not compared with standard care, as an adjunct to home exercise and advice, or when comparing different SMT techniques. Findings compared to sham were mixed. When reported, effects tentatively lasted up to 6 weeks post-intervention.Conclusion: Limited evidence suggests SMT-improved range of motion and was more effective than some other interventions. Future research, using standardized Neurodynamic tests, should explore technique types and evaluate longer-term effects.Level of Evidence: 1a.

Comparison of two mobilization techniques in management of chronic non-specific low back pain

AIM

The aim of the study was to compare between the effects of Maitland's postero-anterior (PA glide) mobilization and Mulligan's sustained natural apophyseal glide (SNAG) on pain, mobility, muscle activation and functional disability in subjects with chronic, non-specific low back pain.

METHODS

The study was a two arm repeated measure design with random allocation of subjects (n = 33). Subjects in group 1 received Maitland's PA glide mobilization and those in group 2 received Mulligan's SNAG. Along with the respective mobilization technique, individualized exercises were common for subjects in both the groups. Subjects in both groups received treatment for 4 days a week for 4 weeks. The outcome measures were numeric pain rating scale (NPRS) scores, lumbar flexion and extension range of motion, erector spinae muscle activity and Oswestry low back pain disability questionnaire score.

RESULTS

The outcome measure scores showed statistical significance in time effect on NPRS (p = 0.001); lumbar flexion and extension range of motion (p = 0.001); erector spinae muscle activity (0.001); Oswestry low back pain disability questionnaire score (p = 0.001); group effect on lumbar flexion (p = 0.03) and extension range of motion (p = 0.05); and interaction effect (time x group) on lumbar flexion (p = 0.003) and extension range of motion (p = 0.002); and, erector spinae muscle activity (p = 0.05) at the 3rd lumbar vertebral level.

CONCLUSION

The addition of Maitland or Mulligan mobilization techniques of the spine does not show a difference in the improvement of symptoms associated with chronic non-specific low back pain.

Immediate effects of Mulligan's techniques on pain and functional mobility in individuals with knee osteoarthritis: A randomized control trial

BACKGROUND AND PURPOSE

Mulligan's mobilization with movement was shown to be effective when implemented in multimodal therapy for knee osteoarthritis. However, no study has evaluated the Mulligan's technique in isolation and compared the relative effectiveness with sham-controlled interventions. Hence, the present study examined the immediate effects of Mulligan's techniques with sham mobilization on the numerical pain rating scale (NPRS) and timed up and go (TUG) test in individuals with knee osteoarthritis.

METHODS

Thirty participants (mean age: 55.3 ± 8.3 years) with symptoms at the knee and radiographic diagnosis of knee osteoarthritis were randomized into sham (n = 15) and intervention (n = 15) groups. The intervention (I) group received Mulligan's mobilization glides that resulted in relative pain relief for three sets of 10 repetitions. For the sham (S) group, the therapist's hand was placed over the joint surfaces mimicking the pain-relieving glides, without providing the gliding force. The outcome measures NPRS and TUG were recorded by a blinded assessor pre- and post-intervention.

RESULTS

Statistically significant differences were identified between the groups in post-intervention median (interquartile range) NPRS (I group: 4.00 [2.00-5.00]; S group: 6.00 [4.00-7.00]) and TUG scores (I group: 10.9 [9.43-10.45]; S group: 13.18 [10.38-16.00]) with the intervention group demonstrating better outcomes (p < .05). Within-group, the post-intervention scores of NPRS and TUG were significantly lower (p < .05) compared to the pre-intervention scores in the intervention group. In the sham group, a statistically significant pre-post change was noticed only in the NPRS scores but not in the TUG scores.

CONCLUSION

Mulligan's techniques were effective in improving pain and functional mobility in individuals with knee osteoarthritis. The underlying mechanisms for observed effects must be examined further, as participants reported pain relief following sham mobilization.

Association between sympathoexcitatory changes and symptomatic improvement following cervical mobilisations in participants with neck pain. A double blind placebo controlled trial

BACKGROUND

sympathoexcitation observed with passive cervical mobilisations may imply activation of an endogenous pain inhibition system resulting in hypoalgesia. However, research is mostly in asymptomatic participants and there is very limited evidence of a relationship between sympathoexcitation and symptomatic improvement in people with clinical pain.

OBJECTIVE

to investigate the effects of cervical mobilisations on the sympathetic nervous system in participants with neck pain, and to explore the relationship between symptomatic improvement and sympathoexcitation.

DESIGN

double-blind randomised controlled trial.

METHOD

40 participants with neck pain (aged 20-69 years, 25 female) were randomly allocated to either cervical mobilisations or motionless placebo. Skin conductance was measured before, during, and after intervention. After interventions were completed, their credibility was assessed. Participants were classified as responders or non-responders according to global symptom change.

RESULTS

participants receiving mobilisations were more likely to be classified as responders (odds ratio: 4.33, p = 0.03) and demonstrated greater change in most outcome measures of sympathoexcitation from baseline to during the intervention but not from during to after the intervention. There was no association between sympathoexcitation and symptomatic improvement. Mobilisations and placebo were equally credible.

CONCLUSIONS

These findings suggest sympathoexcitatory changes may be caused by an orienting response unrelated to the activation of an endogenous pain inhibition system Alternatively, the observed lack of an association may be explained by the existence of various mechanisms for pain relief. This study used single outcome measures of sympathoexcitation and symptomatic improvement and other measures may reveal different things. CLINICALTRIALS.

GOV NUMBER

M10/2016/095.

Effect of myocardial ischemic preconditioning on ischemia-reperfusion stimulation-induced activation in rat thoracic spinal cord with functional MRI

BACKGROUND

Myocardial ischemia and reperfusion-evoked spinal reflexes involve nociceptive signals that trigger neuronal excitation through cardiac afferents, projecting into the thoracic spinal cord. Ischemic preconditioning (IPC) involves brief episodes of sublethal ischemia and reperfusion enhances the resistance of the myocardium to subsequent ischemic insults. This study investigated the effects of IPC on ischemia-reperfusion (I/R) stimulation-induced activation in the thoracic spinal cord of rats.

METHODS

A new remotely controlled I/R model was established. The infarct size was determined as a percentage of area at risk (IS/AAR) and arrhythmia scores were evaluated. Non-invasive in vivo fMRI was used for signal quantitative analysis of thoracic spinal spatiotemporal. The role of IPC on the excitability of substantia gelatinosa (SG) neurons was assessed by spinal patch clamp recording technique. The altered expressions of c-Fos, SP, and CGRP in T₄ segment were detected by immunohistochemical staining.

RESULTS

The novel I/R model was induced successfully and reliably utilized, and IPC treatment markedly reduced the myocardial infarct size. fMRI analysis revealed that IPC reduced the increased BOLD signals induced by prolonged ischemia-reperfusion. Patch clamp recording showed that IPC treatment reversed the enhanced excitability of SG neurons during I/R treatment. The results of immunofluorescent staining indicated that IPC mitigated the I/R-induced dramatic increase of c-Fos, and reduced the release of SP and CGRP in dorsal horns of spinal cord.

CONCLUSIONS

These results suggested that IPC suppressed neuronal activation induced by I/R stimuli in rat thoracic spinal cord using spinal cord fMRI and patch clamp recording techniques.

Ten Key Insights into the Use of Spinal Cord fMRI

A comprehensive review of the literature-to-date on functional magnetic resonance imaging (fMRI) of the spinal cord is presented. Spinal fMRI has been shown, over more than two decades of work, to be a reliable tool for detecting neural activity. We discuss 10 key points regarding the history, development, methods, and applications of spinal fMRI. Animal models have served a key purpose for the development of spinal fMRI protocols and for experimental spinal cord injury studies. Applications of spinal fMRI span from animal models across healthy and patient populations in humans using both task-based and resting-state paradigms. The literature also demonstrates clear trends in study design and acquisition methods, as the majority of studies follow a task-based, block design paradigm, and utilize variations of single-shot fast spin-echo imaging methods. We, therefore, discuss the similarities and differences of these to resting-state fMRI and gradient-echo EPI protocols. Although it is newly emerging, complex connectivity and network analysis is not only possible, but has also been shown to be reliable and reproducible in the spinal cord for both task-based and resting-state studies. Despite the technical challenges associated with spinal fMRI, this review identifies reliable solutions that have been developed to overcome these challenges.

Functional Neuroimaging of Nociceptive and Pain-Related Activity in the Spinal Cord and Brain: Insights From Neurovascular Coupling Studies

Spinal cord and brain processes underlie pain perception, which produces systemic cardiovascular changes. In turn, the autonomic nervous system regulates vascular function in the spinal cord and brain in order to adapt to these systemic changes, while neuronal activity induces local vascular changes. Thus, autonomic regulation and pain processes in the brain and spinal cord are tightly linked and interrelated. The objective of this topical review is to discuss work on neurovascular coupling during nociceptive processing in order to highlight supporting evidence and limitations for the use of cerebral and spinal fMRI to investigate pain mechanisms and spinal nociceptive processes. Work on functional neuroimaging of pain is presented and discussed in relation to available neurovascular coupling studies and related issues. Perspectives on future work are also discussed with an emphasis on differences between the brain and the spinal cord and on different approaches that may be useful to improve current methods, data analyses and interpretation. In summary, this review highlights the lack of data on neurovascular coupling during nociceptive stimulation and indicates that hemodynamic and BOLD responses measured with fMRI may be biased by nonspecific vascular changes. Future neuroimaging studies on nociceptive and pain-related processes would gain further understanding of neurovascular coupling in the brain and spinal cord and should take into account the effects of systemic vascular changes that may affect hemodynamic responses. Anat Rec, 301:1585-1595, 2018. © 2018 Wiley Periodicals, Inc.

Resting-state functional connectivity in the rat cervical spinal cord at 9.4 T

PURPOSE

Numerous studies have adopted resting-state functional MRI methods to infer functional connectivity between cortical regions, but very few have translated them to the spinal cord, despite its critical role in the central nervous system. Resting-state functional connectivity between gray matter horns of the spinal cord has previously been shown to be detectable in humans and nonhuman primates, but it has not been reported previously in rodents.

METHODS

Resting-state functional MRI of the cervical spinal cord of live anesthetized rats was performed at 9.4 T. The quality of the functional images acquired was assessed, and quantitative analyses of functional connectivity in C4-C7 of the spinal cord were derived.

RESULTS

Robust gray matter horn-to-horn connectivity patterns were found that were statistically significant when compared with adjacent control regions. Specifically, dorsal-dorsal and ventral-ventral connectivity measurements were most prominent, while ipsilateral dorsal-ventral connectivity was also observed but to a lesser extent. Quantitative evaluation of reproducibility also revealed moderate robustness in the bilateral sensory and motor networks that was weaker in the dorsal-ventral connections.

CONCLUSIONS

This study reports the first evidence of resting-state functional circuits within gray matter in the rat spinal cord, and verifies their detectability using resting-state functional MRI at 9.4 T. Magn Reson Med 79:2773-2783, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Decreased spontaneous activity and altered evoked nociceptive response of rat thalamic submedius neurons to lumbar vertebra thrust

The thalamus is a central structure important to modulating and processing all mechanoreceptor input destined for the cortex. A large number of diverse mechanoreceptor endings are stimulated when a high velocity low amplitude thrust is delivered to the lumbar spine during spinal manipulation. The objective of this study was to determine if a lumbar thrust alters spontaneous and/or evoked nociceptive activity in medial thalamic submedius (Sm) neurons. Extracellular recordings were obtained from 94 thalamic Sm neurons in 54 urethane-anesthetized adult Wistar rats. Spontaneous activity was recorded 5 min before and after an L₅ control (no thrust) and thrust (85% rat body weight; 100 ms) procedure. In a subset of responsive nociceptive-specific neurons, mean changes in noxious-evoked response (10-s pinch with clip; 795 g) at three sites (tail, contra- and ipsilateral hindpaw) were determined following an L₅ thrust. Mean changes in Sm spontaneous activity (60 s bins) and evoked noxious response were compared using a mixed model repeated measures ANOVA with Bonferroni post hoc t tests and paired t tests, respectively. Compared to control, spontaneous Sm activity decreased 180-240 s following the lumbar thrust (p < 0.005). Inhibitory evoked responses were attenuated in the contralateral hindpaw following an L₅ thrust compared to control (p < 0.05). No other changes in spontaneous or noxious-evoked Sm activity were found. A delayed, but prolonged suppression of spontaneous Sm activity along with changes in noxious-evoked inhibitory responses in the contralateral hindpaw following lumbar vertebra thrust suggest that thalamic submedius neurons may play a role in central pain modulation related to manual therapy intervention.

Effect of Seven Sessions of Posterior-to-Anterior Spinal Mobilisation versus Prone Press-ups in Non-Specific Low Back Pain - Randomized Clinical Trial

INTRODUCTION

Low back pain is non-specific in 85% of population. Posterior-to-anterior (PA) mobilization and press-up exercises are common physical therapy interventions used to treat low back pain.

AIM

The purpose of this study was to investigate the effect of posterior-to-anterior spinal mobilization and prone press-ups in non-specific low back pain.

MATERIALS AND METHODS

The study design was double blind randomized clinical trial. Forty participants reporting to Physiotherapy Out-patient department in hospital who were 18-45 years of age and had diagnosis of non-specific low back pain were included. Primary outcome measures were lumbar extension range, pain and physical function.

RESULTS

Both interventions resulted in significant reduction in the average pain scores for both groups. Similarly, gain in total lumbar extension was significant in both the PA mobilization group and the press-up group. Functional scores significantly improved for both the groups. Both the groups significantly differed in terms of pain, lumbar extension and functional scores. PA mobilization proved to be a superior intervention.

CONCLUSION

PA mobilization and press-ups can be used as an effective intervention in non-specific low back pain.

Antinociceptive Effects of Spinal Manipulative Therapy on Nociceptive Behavior of Adult Rats during the Formalin Test

Optimizing pain relief resulting from spinal manipulative therapies, including low velocity variable amplitude spinal manipulation (LVVA-SM), requires determining their mechanisms. Pain models that incorporate simulated spinal manipulative therapy treatments are needed for these studies. The antinociceptive effects of a single LVVA-SM treatment on rat nociceptive behavior during the commonly used formalin test were investigated. Dilute formalin was injected subcutaneously into a plantar hindpaw. Licking behavior was video-recorded for 5 minutes. Ten minutes of LVVA-SM at 20° flexion was administered with a custom-made device at the lumbar (L5) vertebra of isoflurane-anesthetized experimental rats (n = 12) beginning 10 minutes after formalin injection. Hindpaw licking was video-recorded for 60 minutes beginning 5 minutes after LVVA-SM. Control rats (n = 12) underwent the same methods except for LVVA-SM. The mean times spent licking the formalin-injected hindpaw of both groups 1–5 minutes after injection were not different. The mean licking time during the first 20 minutes post-LVVA-SM of experimental rats was significantly less than that of control rats (P < 0.001). The mean licking times of both groups during the second and third 20 minutes post-LVVA-SM were not different. Administration of LVVA-SM had a short-term, remote antinociceptive effect similar to clinical findings. Therefore, mechanistic investigations using this experimental approach are warranted.

A preliminary study comparing the use of cervical/upper thoracic mobilization and manipulation for individuals with mechanical neck pain

OBJECTIVES

Neck pain is routinely managed using manual therapy (MT) to the cervical and thoracic spines. While both mobilizations and manipulations to these areas have been shown to reduce neck pain, increase cervical range of motion, and reduce disability, the most effective option remains elusive. The purpose of this preliminary trial was to compare the pragmatic use of cervical and thoracic mobilizations vs. manipulation for mechanical neck pain.

METHODS

This trial included 20 patients with mechanical neck pain. Each patient was randomized to receive either mobilization or manipulation to both the cervical and thoracic spines during their plan of care. Within-group analyses were made with Wilcoxon signed-rank tests and between-group analyses were made with Mann-Whitney U.

RESULTS

There were no between-group differences for any of the dependent variables including cervical active range of motion (CAROM) (P = 0.18), deep cervical flexion (DCF) endurance (P = 0.06), numerical pain rating scale (NPRS) (P = 0.26), the neck disability index (NDI, P = 0.33), patient-specific functional scale (PSFS, P = 0.20), or the global rating of change (GROC) scale (P = 0.94). Within-group results were significant for all outcome variables (P<0.001) from initial evaluation to discharge for both groups.

DISCUSSION

These findings were consistent with other trials previously conducted that applied the MT techniques in a pragmatic fashion, but varied from previous trials where the treatment was standardized. A larger experimental study is necessary to further examine the differences between mobilization and manipulation for neck pain.

Using functional magnetic resonance imaging to determine if cerebral hemodynamic responses to pain change following thoracic spine thrust manipulation in healthy individuals

STUDY DESIGN

Case series.

OBJECTIVES

To use blood oxygenation level-dependent functional magnetic resonance imaging (fMRI) to determine if supraspinal activation in response to noxious mechanical stimuli varies pre- and post-thrust manipulation to the thoracic spine.

BACKGROUND

Recent studies have demonstrated the effectiveness of thoracic thrust manipulation in reducing pain and improving function in some individuals with neck and shoulder pain. However, the mechanisms by which manipulation exerts such effects remain largely unexplained. The use of fMRI in the animal model has revealed a decrease in cortical activity in response to noxious stimuli following manual joint mobilization. Supraspinal mediation contributing to hypoalgesia in humans may be triggered following spinal manipulation.

METHODS

Ten healthy volunteers (5 women, 5 men) between the ages of 23 and 48 years (mean, 31.2 years) were recruited. Subjects underwent fMRI scanning while receiving noxious stimuli applied to the cuticle of the index finger at a rate of 1 Hz for periods of 15 seconds, alternating with periods of 15 seconds without stimuli, for a total duration of 5 minutes. Subjects then received a supine thrust manipulation directed to the midthoracic spine and were immediately returned to the scanner for reimaging with a second delivery of noxious stimuli. An 11-point numeric pain rating scale was administered immediately after the application of noxious stimuli, premanipulation and postmanipulation. Blood oxygenation level-dependent fMRI recorded the cerebral hemodynamic response to the painful stimuli premanipulation and postmanipulation.

RESULTS

The data indicated a significant reduction in subjects' perception of pain (P<.01), as well as a reduction in cerebral blood flow as measured by the blood oxygenation level-dependent response following manipulation to areas associated with the pain matrix (P<.05). There was a significant relationship between reduced activation in the insular cortex and decreased subjective pain ratings on the numeric pain rating scale (r = 0.59, P<.05).

CONCLUSION

This study provides preliminary evidence that suggests that supraspinal mechanisms may be associated with thoracic thrust manipulation and hypoalgesia. However, because the study lacked a control group, the results do not allow for the discernment of the causative effects of manipulation, which may also be related to changes in levels of subjects' fear, anxiety, or expectation of successful outcomes with manipulation. Future investigations should strive to elicit more conclusive findings in the form of randomized clinical trials.

Neural mobilization reverses behavioral and cellular changes that characterize neuropathic pain in rats

BACKGROUND

The neural mobilization technique is a noninvasive method that has proved clinically effective in reducing pain sensitivity and consequently in improving quality of life after neuropathic pain. The present study examined the effects of neural mobilization (NM) on pain sensitivity induced by chronic constriction injury (CCI) in rats. The CCI was performed on adult male rats, submitted thereafter to 10 sessions of NM, each other day, starting 14 days after the CCI injury. Over the treatment period, animals were evaluated for nociception using behavioral tests, such as tests for allodynia and thermal and mechanical hyperalgesia. At the end of the sessions, the dorsal root ganglion (DRG) and spinal cord were analyzed using immunohistochemistry and Western blot assays for neural growth factor (NGF) and glial fibrillary acidic protein (GFAP).

RESULTS

The NM treatment induced an early reduction (from the second session) of the hyperalgesia and allodynia in CCI-injured rats, which persisted until the end of the treatment. On the other hand, only after the 4th session we observed a blockade of thermal sensitivity. Regarding cellular changes, we observed a decrease of GFAP and NGF expression after NM in the ipsilateral DRG (68% and 111%, respectively) and the decrease of only GFAP expression after NM in the lumbar spinal cord (L3-L6) (108%).

CONCLUSIONS

These data provide evidence that NM treatment reverses pain symptoms in CCI-injured rats and suggest the involvement of glial cells and NGF in such an effect.

Rodent functional and anatomical imaging of pain

Human brain imaging has provided much information about pain processing and pain modulation, but brain imaging in rodents can provide information not attainable in human studies. First, the short lifespan of rats and mice, as well as the ability to have homogenous genetics and environments, allows for longitudinal studies of the effects of chronic pain on the brain. Second, brain imaging in animals allows for the testing of central actions of novel pharmacological and nonpharmacological analgesics before they can be tested in humans. The two most commonly used brain imaging methods in rodents are magnetic resonance imaging (MRI) and positron emission tomography (PET). MRI provides better spatial and temporal resolution than PET, but PET allows for the imaging of neurotransmitters and non-neuronal cells, such as astrocytes, in addition to functional imaging. One problem with rodent brain imaging involves methods for keeping the subject still in the scanner. Both anesthetic agents and restraint techniques have potential confounds. Some PET methods allow for tracer uptake before the animal is anesthetized, but imaging a moving animal also has potential confounds. Despite the challenges associated with the various techniques, the 31 studies using either functional MRI or PET to image pain processing in rodents have yielded surprisingly consistent results, with brain regions commonly activated in human pain imaging studies (somatosensory cortex, cingulate cortex, thalamus) also being activated in the majority of these studies. Pharmacological imaging in rodents shows overlapping activation patterns with pain and opiate analgesics, similar to what is found in humans. Despite the many structural imaging studies in human chronic pain patients, only one study has been performed in rodents, but that study confirmed human findings of decreased cortical thickness associated with chronic pain. Future directions in rodent pain imaging include miniaturized PET for the freely moving animal, as well as new MRI techniques that enable ongoing chronic pain imaging.

Novel use of a manual therapy technique and management of a patient with peroneal tendinopathy: a case report

Peroneal tendinopathy is an uncommon but underappreciated source of lateral hindfoot pain and dysfunction. There is a paucity of literature describing optimal intervention for those suffering with pain secondary to peroneal tendinopathy. The purpose of this case report is to describe the evaluation and treatment incorporating manual therapy and therapeutic exercise for a patient diagnosed with peroneal tendinopathy. The patient was a 50 year-old female with a history of chronic lateral ankle pain and whose presentation was consistent with peroneal tendinopathy. Despite attempts to improve pain and function with over-the-counter orthotics, manual therapy to a hypomobile talocrural joint, and strengthening of the peroneal tendons, successful response was not reported until a lateral calcaneal glide was added. Improvement in impairments (pain, talocrural dorsiflexion, unilateral heel raises, and Star Excursion Balance Test) and function (Lower Extremity Functional Scale and Global Rating of Change), were observed over a course of eight visits. The patient was able to return to work and her recreational work out routine without limitations. In conclusion a successful physical therapy intervention for a patient with peroneal tendinopathy included a unique manual therapy technique, the lateral calcaneal glide, in conjunction with other manual therapy techniques and a structured home exercise program.

Paradigm shift in translational neuroimaging of CNS disorders

During the last two decades, functional neuroimaging technology, especially functional magnetic resonance imaging (fMRI), has improved tremendously, with new attention towards resting-state functional connectivity of the brain. This development has allowed scientists to study changes in brain structure and function, and probe these two properties under conditions of evoked stimulation, disease and drug administration. In the domain of functional imaging, the identification and characterization of central nervous system (CNS) functional networks have emerged as potential biomarkers for CNS disorders in humans. Recent attempts to translate clinical neuroimaging methodology to preclinical studies have also been carried out, which offer new opportunities in translational neuroscience research. In this paper, we review recent developments in structural and functional MRI and their use to probe functional connectivity in various CNS disorders such as schizophrenia, mood disorders, Alzheimer's disease (AD) and pain.

Spinal cord - MR of rodent models

Different MR techniques, such as relaxation times, diffusion, perfusion, and spectroscopy have been employed to study rodent spinal cord. In this chapter, a description of these methods is given, along with examples of normal metrics that can be derived from the MR acquisitions, as well as examples of applications to pathology.

MRI in rodent models of brain disorders

Magnetic resonance imaging (MRI) is a well-established tool in clinical practice and research on human neurological disorders. Translational MRI research utilizing rodent models of central nervous system (CNS) diseases is becoming popular with the increased availability of dedicated small animal MRI systems. Projects utilizing this technology typically fall into one of two categories: 1) true "pre-clinical" studies involving the use of MRI as a noninvasive disease monitoring tool which serves as a biomarker for selected aspects of the disease and 2) studies investigating the pathomechanism of known human MRI findings in CNS disease models. Most small animal MRI systems operate at 4.7-11.7 Tesla field strengths. Although the higher field strength clearly results in a higher signal-to-noise ratio, which enables higher resolution acquisition, a variety of artifacts and limitations related to the specific absorption rate represent significant challenges in these experiments. In addition to standard T1-, T2-, and T2*-weighted MRI methods, all of the currently available advanced MRI techniques have been utilized in experimental animals, including diffusion, perfusion, and susceptibility weighted imaging, functional magnetic resonance imaging, chemical shift imaging, heteronuclear imaging, and (1)H or (31)P MR spectroscopy. Selected MRI techniques are also exclusively utilized in experimental research, including manganese-enhanced MRI, and cell-specific/molecular imaging techniques utilizing negative contrast materials. In this review, we describe technical and practical aspects of small animal MRI and provide examples of different MRI techniques in anatomical imaging and tract tracing as well as several models of neurological disorders, including inflammatory, neurodegenerative, vascular, and traumatic brain and spinal cord injury models, and neoplastic diseases.

CNS animal fMRI in pain and analgesia

Animal imaging of brain systems offers exciting opportunities to better understand the neurobiology of pain and analgesia. Overall functional studies have lagged behind human studies as a result of technical issues including the use of anesthesia. Now that many of these issues have been overcome including the possibility of imaging awake animals, there are new opportunities to study whole brain systems neurobiology of acute and chronic pain as well as analgesic effects on brain systems de novo (using pharmacological MRI) or testing in animal models of pain. Understanding brain networks in these areas may provide new insights into translational science, and use neural networks as a "language of translation" between preclinical to clinical models. In this review we evaluate the role of functional and anatomical imaging in furthering our understanding in pain and analgesia.

Functional magnetic resonance imaging of the spinal cord during sensory stimulation in diabetic rats

PURPOSE

To determine if differences exist between control and diabetic rats in functional magnetic resonance imaging (fMRI) activity of the spinal cord and if fMRI can provide a means of early detection of diabetic neuropathy.

MATERIALS AND METHODS

fMRI of the spinal cord, using noxious electrical stimulation (15 V ( approximately 8 mA), 0.3 msec, 3 Hz) of the hind paw, was performed in groups of control and streptozotocin (STZ)-induced type 1 diabetic rats.

RESULTS

Diabetic rats were lighter, hyperglycemic, and had lower blood pH than controls. fMRI activity at the lumbar enlargement of the spinal cord was identified in the dorsal horn ipsilateral to stimulus of all animals. Signal intensity changes across the lumbar spinal cord during periods of activity were not significantly different between control and diabetic rats, with a trend toward greater signal changes in controls. When specific regions of the spinal cord were analyzed, control rats exhibited significantly increased blood-oxygen level-dependent (BOLD) fMRI activity in both ipsilateral and contralateral dorsal horn compared to diabetic rats.

CONCLUSION

The results of this study are consistent with reports that primary afferent input to the spinal cord is diminished by diabetes, and suggest that BOLD fMRI may be useful in early detection of diabetic neuropathy.

The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model

Prior studies suggest manual therapy (MT) as effective in the treatment of musculoskeletal pain; however, the mechanisms through which MT exerts its effects are not established. In this paper we present a comprehensive model to direct future studies in MT. This model provides visualization of potential individual mechanisms of MT that the current literature suggests as pertinent and provides a framework for the consideration of the potential interaction between these individual mechanisms. Specifically, this model suggests that a mechanical force from MT initiates a cascade of neurophysiological responses from the peripheral and central nervous system which are then responsible for the clinical outcomes. This model provides clear direction so that future studies may provide appropriate methodology to account for multiple potential pertinent mechanisms.

Effects of a single session of posterior-to-anterior spinal mobilization and press-up exercise on pain response and lumbar spine extension in people with nonspecific low back pain

BACKGROUND AND PURPOSE

Posterior-to-anterior (PA) mobilization and press-up exercises are common physical therapy interventions used to treat low back pain. The purpose of this study was to examine the immediate effects of PA mobilization and a press-up exercise on pain with standing extension and lumbar extension in people with nonspecific low back pain.

SUBJECTS

The study participants were 30 adults (19 women and 11 men) who were 18 to 45 years of age and had a diagnosis of nonspecific low back pain.

METHODS

Lumbar segmental extension during a press-up maneuver was measured by dynamic magnetic resonance imaging prior to and immediately following a single session of either PA spinal mobilization or a press-up exercise. Pain scores before and after intervention were recorded with a visual analog scale. Differences between the treatment groups in pain and total lumbar extension were compared over time by use of a 2-way analysis of variance.

RESULTS

Following both interventions, there was a significant reduction in the average pain scores for both groups (significant main effect for time, no interaction). Similarly, total lumbar extension significantly increased in both the PA mobilization group and the press-up group (significant main effect for time, no interaction). No significant differences between the 2 interventions in pain or lumbar extension were found.

DISCUSSION AND CONCLUSION

The findings of this study support the use of PA mobilization and a press-up exercise for improving lumbar extension in people with nonspecific low back pain. Although statistically significant within-group changes in pain were detected, the clinical meaningfulness of these changes is questionable.

Potential clinical applications for spinal functional MRI

Functional MRI (fMRI) of the spinal cord is a noninvasive technique for obtaining information regarding spinal cord neuronal function. This article provides a brief overview of recent developments in spinal cord fMRI and outlines potential applications, as well as the limitations that must be overcome, for using spinal fMRI in the clinic. This technique is currently used for research purposes, but significant potential exists for spinal fMRI to become an important clinical tool.

Comparison of functional activity in the rat cervical spinal cord during alpha-chloralose and halothane anesthesia

Alpha-chloralose is commonly used during animal fMRI studies for anesthesia, however, recovery of animals is difficult, limiting experimental design. The use of a less invasive anesthetic would enable chronic experiments. The present study compares functional activity in the spinal cord of the alpha-chloralose and halothane-anesthetized rat. Functional MRI of the rat cervical spinal cord was performed on 6 alpha-chloralose and 6 halothane-anesthetized rats in a Bruker 7 T MR system during electrical stimulation of the right forepaw. Following imaging, four animals from each group were perfused and spinal cords removed for immunohistochemical analysis. Areas of c-fos expression were identified with immunofluorescent labeling to confirm the presence of neuronal activity. Functional activity and c-fos expression were observed predominantly between the fifth and seventh cervical spinal cord segments. Areas of fMRI activation in the spinal cord correspond well with spinal cord physiology. Areas of c-fos expression confirmed that neuronal activity was present in the regions of fMRI activity. The regions and amount of fMRI activity observed were similar for both anesthetics. Functional magnetic resonance imaging of the spinal cord can be achieved using both alpha-chloralose and halothane anesthesia in rats. We therefore suggest that halothane may be used as an anesthetic agent for chronic fMRI studies of the spinal cord.

Blood oxygenation level-dependent visualization of synaptic relay stations of sensory pathways along the neuroaxis in response to graded sensory stimulation of a limb

Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) was used to test at which levels of the neuroaxis signals are elicited when different modalities of sensory information from the limbs ascend to cortex cerebri. We applied graded electric stimuli to the rat hindlimbs and used echo-planar imaging to monitor activity changes in the lumbar spinal cord and medulla oblongata, where primary afferents of painful and nonpainful sensation synapse, respectively. BOLD signals were detected in ipsilateral lumbar spinal cord gray matter using sufficiently strong stimuli. Using stimuli well below the threshold needed for signals to be elicited in the spinal cord, we found BOLD responses in dorsal medulla oblongata. The distribution of these signals is compatible with the neuroanatomy of the respective synaptic relay stations of the corresponding sensory pathways. Hence, the sensory pathways conducting painful and nonpainful information were successfully distinguished. The fMRI signals in the spinal cord were markedly decreased by morphine, and these effects were counteracted by naloxone. We conclude that fMRI can be used as a reliable and valid method to monitor neuronal activity in the rat spinal cord and medulla oblongata in response to sensory stimuli. Previously, we also documented BOLD signals from thalamus and cortex. Thus, BOLD responses can be elicited at all principal synaptic relay stations along the neuroaxis from lumbar spinal cord to sensory cortex. Rat spinal cord fMRI should become a useful tool in experimental spinal cord injury and pain research.

Simultaneous functional magnetic resonance imaging in the rat spinal cord and brain

Functional magnetic resonance imaging (fMRI) method was developed to investigate the pattern and temporal relationship in neuronal pathways of brain and spinal cord. Signal intensity changes correlating with stimulation patterns were observed simultaneously in the rat spinal cord and brain using fMRI at 9.4 T. Electrical stimulation of the forepaw was used to elicit activity. A quadrature volume RF coil covering both brain and the cervical spinal cord was used. Sets of fast spin echo (FSE) images were acquire simultaneously for both brain and spinal cord fMRI. Experiments were repeated in single animal and across animals. Activities within the dorsal horn of the spinal cord and within the somatosensory cortex were observed consistently within each animal as well as across animals.

The role of fMRI in drug discovery

Pharmacological functional (phMRI) studies are making a significant contribution to our understanding of drug-effects on brain systems. Pharmacological fMRI has an additional contribution to make in the translation of disease models and candidate compounds from preclinical to clinical investigation and in the early clinical stages of drug development. Here it can demonstrate a proof-of-concept of drug action in a small human cohort and thus contribute substantially to decision-making in drug development. We review the methods underlying pharmacological fMRI studies and the links that can be made between animal and human investigations. We discuss the potential fMRI markers of drug effect, experimental designs and caveats in interpreting hemodynamic fMRI data as reflective of changes in neuronal activity. Although there are no current published examples of fMRI applied to novel compounds, we illustrate the potential of fMRI across a range of applications and with specific reference to processing of pain in the human brain and pharmacological analgesia. Pharmacological fMRI is developing to meet the neuroscientific challenges. Electrophysiological methods can be used to corroborate the drug effects measured hemodynamically with fMRI. In future, pharmacological fMRI is likely to extend to examinations of the spinal cord and into pharmacogenetics to relate genetic polymorphisms to differential responses of the brain to drugs.

Magnetic resonance imaging of neuronal function in the spinal cord: spinal FMRI

A review of the current literature on magnetic resonance imaging of neuronal function in the spinal cord (spinal fMRI) is presented. The unique challenges of spinal fMRI are identified as being the small cross-sectional dimensions of the spinal cord, magnetic field inhomogeneity caused by the bone and cartilage in the spine, and motion of cerebrospinal fluid, blood, adjacent tissues and organs and of the spinal cord itself. Techniques have been developed to overcome or compensate for these challenges and the result is a fMRI method which is distinct from that used for mapping function in the brain. Evidence that the current spinal fMRI method provides accurate and sensitive maps of neuronal function is also discussed. Studies presented in the literature have demonstrated areas of neuronal activity corresponding with spinal cord neuroanatomy as a result of thermal and electrical stimuli and motor tasks with the hands, arms and legs. Signal intensity changes detected in active areas have also been demonstrated to depend on the intensity of the stimuli with both thermal stimulation and a motor task, providing evidence of the correspondence between spinal fMRI results and neuronal activity in the spinal cord.

Functional magnetic resonance imaging of the human lumbar spinal cord

PURPOSE

To determine whether consistent regions of activity could be observed in the lumbar spinal cord of single subjects with spin-echo functional MRI (fMRI) if several repeated experiments were performed within a single imaging session.

MATERIALS AND METHODS

Repeated fMRI experiments of the human lumbar spinal cord were performed at 1.5 T with a single-shot spin-echo technique (half-Fourier single-shot turbo spin-echo (HASTE)) as used by previous investigators, and a modified method (fluid-attenuated inversion recovery (FLAIR)-HASTE) that nulled the otherwise highly variable signal from the cerebrospinal fluid (CSF).

RESULTS

FLAIR-HASTE reduced the variability of the signal in the CSF region to background levels, and presumably reduced associated artifacts in the spinal cord. Consistent areas of activation in the spinal cord in response to a thermal stimulus just below the knee were not observed across the fMRI experiments with either method.

CONCLUSION

FLAIR-HASTE was useful for removing artifact in the spinal cord signal induced by variability in the CSF signal. However, with the techniques used in this study, we were not able to confirm the presence of a consistent fMRI response in the lumbar spinal cord because of the signal enhancement by extravascular protons (SEEP) effect during thermal stimulation of the hindlimb.

Magnetic resonance imaging, microscopy, and spectroscopy of the central nervous system in experimental animals

Over the last two decades, microscopic resolution in vivo magnetic resonance imaging (MRI) techniques have been developed and extensively used in the study of animal models of human diseases. Standard MRI methods are frequently used in clinical studies and in the general clinical practice of human neurological diseases. This generates a need for similar studies in experimental animal research. Because small rodents are the most commonly used species as animal models of neurological diseases, the MRI techniques need to be able to provide microscopic resolution and high signal-to-noise ratio images in relatively short time. Small animal MRI systems use very high field-strength magnets, which results in higher signal to noise ratio; however, the contrast characteristics of live tissue are different at these field strengths. In addition to standard MRI techniques, several new applications have been implemented in experimental animals, including diffusion and perfusion studies, MR angiography, functional MRI studies, MRI tractography, proton and phosphorous spectroscopy, cellular and molecular imaging using novel contrast methods. Here we give an overview of how to establish a small animal imaging facility with the goal of CNS imaging. We describe the basic physical processes leading to MR signal generation, highlighting the differences between standard clinical MRI and small animal MRI. Finally, typical findings in the most common neurological disease categories and novel MRI/magnetic resonance spectroscopy methods used in their study are also described.

High-resolution MR imaging of the rat spinal cord in vivo in a wide-bore magnet at 17.6 Tesla

The objective was to demonstrate the feasibility and to evaluate the performance of high-resolution in vivo magnetic resonance (MR) imaging of the rat spinal cord in a 17.6-T vertical wide-bore magnet. A probehead consisting of a surface coil that offers enlarged sample volume suitable for rats up to a weight of 220 g was designed. ECG triggered and respiratory-gated gradient echo experiments were performed on a Bruker Avance 750 wide-bore spectrometer for high-resolution imaging. With T*2 values between 5 and 20 ms, good image contrast could be obtained using short echo times, which also minimizes motion artifacts. Anatomy of healthy spinal cords and pathomorphological changes in traumatically injured rat spinal cord in vivo could be visualized with microscopic detail. It was demonstrated that imaging of the rat spinal cord in vivo using a vertical wide-bore high-magnetic-field system is feasible. The potential to obtain high-resolution images in short scan times renders high-field imaging a powerful diagnostic tool.

Correlation of functional activation in the rat spinal cord with neuronal activation detected by immunohistochemistry

The relationship between neuronal activity in the rat cervical and lumbar spinal cord was examined using functional magnetic resonance imaging (fMRI) and immunohistochemistry. Neuronal activity determined by c-fos staining was greatest between L4 and L6, and C5 to C7 spinal cord segments during noxious electrical stimulation of the rat hindpaw and forepaw, respectively. Areas of activity determined by fMRI are consistent with spinal cord physiology, and are predominantly found in regions of the spinal cord associated with pain, namely the dorsal horn. Activity in the ventral region of the cord was also observed, as expected. Combined results from repeated experiments demonstrated consistent areas of activity in response to stimulation, and show a high degree of reproducibility. Good correspondence was observed between functional MRI and sites of neuronal activity determined by c-fos labeling.