Responses to a clinical test of mechanical provocation of nerve tissue in whiplash associated disorder

Involvement of nerve tissue may contribute to the persistence of pain following a whiplash injury. This study aimed to investigate responses to the brachial plexus provocation test (BPPT) in 156 subjects with chronic whiplash associated disorder (WAD) with and without associated arm pain and 95 asymptomatic control subjects. The range of elbow extension (ROM) and visual analogue scale (VAS) pain scores were measured. Subjects with chronic WAD demonstrated significantly less ROM and higher VAS scores with the BPPT than the asymptomatic subjects (P<0.001). These effects occurred bilaterally. Within the whiplash population, subjects whose arm pain was reproduced by the BPPT demonstrated significantly less ROM on both the symptomatic and asymptomatic sides when compared to the whiplash subjects whose arm pain was not reproduced by the BPPT (P=0.003) and significantly less ROM and higher VAS scores than those whiplash subjects with no arm pain (P=0.003, 0.01). Only the whiplash subjects whose arm pain was reproduced by the BPPT demonstrated differences between the symptomatic and asymptomatic sides. These generalized hyperalgesic responses to the BPPT support the hypothesis of central nervous system hypersensitivity as contributing to persistent pain experienced by WAD patients.     

Scapular behavior in shoulder impingement syndrome.

OBJECTIVE: To quantify the contribution of each scapular rotation to the scapular total range of motion (ROM) in both shoulders of persons with a unilateral shoulder impingement syndrome (SIS), to compare 3-dimensional (3D) scapular attitudes of their symptomatic and asymptomatic shoulders in flexion and in abduction, and to characterize the scapular behavior of these subjects by classifying them into subgroups based on scapular tilting differences between their symptomatic and asymptomatic shoulders. DESIGN: Comparisons of 3D scapular attitudes, scapular total ROM, and percentage of contributions of each scapular rotation to the scapular total ROM. SETTING: A motricity laboratory. PARTICIPANTS: Fifty-one subjects, including 41 with a SIS (29 had an asymptomatic contralateral shoulder) and 10 healthy subjects. INTERVENTIONS: The 3D scapular attitudes were calculated with the subjects in a standardized seated position; with the arm at rest; or at 70 degrees, 90 degrees, and 110 degrees of shoulder flexion and abduction. Axial rotation angles were calculated using a fixed set of Cardanic angles. MAIN OUTCOME MEASURES: At 90 degrees of arm elevation, data from 10 shoulders of healthy subjects were used to set up normative values (99% confidence interval of mean 3D scapular attitudes) to compare with 3D scapular attitudes of symptomatic and asymptomatic shoulders of SIS subjects. We analyzed the scapula behavior of subjects with SIS and classified them into subgroups based on scapular anterior tilting asymmetry. RESULTS: In flexion, almost half of the scapular total ROM was provided by anterior tilting (48.2%-51.3%), whereas in abduction, external rotation (40.3%-42.4%) was the main contributor. Scapular total ROM was higher in abduction than in flexion in all arm positions for both shoulder groups (P <.01). Also, 3D scapular attitude patterns of both shoulders of SIS subjects were different from those of healthy subjects. At 90 degrees, scapular asymmetry in anterior tilting allowed us to classify SIS subjects with respect to more (lead) or less (lag) scapular tilting in the affected side (P <.0001) or no difference (P =.11) between the sides (symmetrical). No significant differences (P >.05), except for a small 2 degrees difference in transverse rotation during arm flexion at 110 degrees (P =.002), were observed in 3D scapular attitudes and scapular total ROM between both shoulders of SIS subjects. Patterns of 3D scapular attitudes and scapular total ROM were significantly different between flexion and abduction arm positions (P <.05). CONCLUSIONS: The contribution of rotations and scapular total ROM differed according to the plane of arm elevation in SIS subjects. Group analyses revealed no differences in 3D scapular attitudes between symptomatic and asymptomatic shoulders of subjects with unilateral SIS. This could be caused by the use, in SIS subjects, of inappropriate neuromuscular strategies affecting both shoulders. However, individual analyses revealed scapular asymmetry in the sagittal plane, which suggests that SIS subjects with less anterior tilting in the symptomatic shoulder, as compared with the asymptomatic contralateral one, may be at high risk of developing chronic SIS. This last finding provides scientific evidence to focus rehabilitation protocols toward a restoration of anterior tilting.     

Comparison of Median Nerve Mechanosensitivity and Pressure Pain Threshold in Patients With Nonspecific Neck Pain and Asymptomatic Individuals

Objective

The purpose of this study was to investigate the presence of median nerve mechanosensitivity by comparing median nerve neurodynamic test results of patients with nonspecific neck pain (NNP) and asymptomatic individuals.

Aberrant protective force generation during neural provocation testing and the effect of treatment in patients with neurogenic cervicobrachial pain

BACKGROUND: Observation of the occurrence of protective muscle activity is advocated in assessment of the peripheral nervous system by means of neural provocation tests. However, no studies have yet demonstrated abnormal force generation in a patient population. OBJECTIVES: To analyze whether aberrations in shoulder girdle-elevation force during neural tissue provocation testing for the median nerve (NTPT1) can be demonstrated, and whether possible aberrations can be normalized following cervical mobilization. STUDY DESIGN: A single-blind randomized comparative controlled study. SETTING: Laboratory setting annex in a manual therapy teaching practice. PARTICIPANTS: Twenty patients with unilateral or bilateral neurogenic cervicobrachial pain. METHODS: During the NTPT1, we used a load cell and electrogoniometer to record continuously the shoulder-girdle elevation force in relation to the available range of elbow extension. Following randomization, we analyzed the immediate treatment effects of a cervical contralateral lateral glide mobilization technique (experimental group) and therapeutic ultrasound (control group). RESULTS: On the involved side, the shoulder-girdle elevation force occurred earlier, and the amount of force at the end of the test was substantially, though not significantly, greater than that on the uninvolved side at the corresponding range of motion. Together with a significant reduction in pain perception after cervical mobilization, a clear tendency toward normalization of the force curve could be observed, namely, a significant decrease in force generation and a delayed onset. The control group demonstrated no differences. CONCLUSIONS: Aberrations in force generation during neural provocation testing are present in patients with neurogenic pain and can be normalized with appropriate treatment modalities.     

Quantitative in vivo studies of median nerve sliding in response to wrist, elbow, shoulder and neck movements

Objective. To examine median nerve sliding in response to upper limb movements in vivo. To determine whether the median nerve can be unloaded.

Design. Exploratory study in healthy subjects.

Background. Impaired sliding may lead to neuropathic symptoms. In vivo results for neural dynamics in normal subjects are essential to understand changes in upper limb disorders.

Methods. Ultrasound imaging of the median nerve during 40° wrist extension, 80° shoulder abduction, 90° elbow extension, and 35° contralateral neck side flexion. Frame by frame cross-correlation of image sequences to measure nerve sliding and strain.

Results. Nerve excursion in the forearm and upper arm ranged from 0.3 mm for neck side flexion to 10.4 mm for elbow extension. Additional strain in the forearm for wrist extension was 1.1% (SEM, 0.2%), for shoulder abduction 1.0% (SEM, 0.2%), and for neck side flexion 0.1% (SEM, 0.1%). With the limb flexed, sliding was delayed and sometimes the nerve or the nerve fascicles had a wavy appearance.

Conclusion. The median nerve is unloaded when the shoulder is adducted or elbow flexed. When the arm is extended (90° shoulder abduction, 60° wrist extension, and elbow straight) the total additional strain in the forearm will be 2.5–3.0%. Even in this position the strain is likely to be below levels that impair blood flow or conduction. Therefore, the median nerve appears well designed to cope with changes in bed length caused by limb movements.Relevance

These results will provide baseline data that can be used to examine entrapment neuropathies.     

Shoulder and elbow range of motion for the performance of activities of daily living: A systematic review

The loss of range of motion (ROM) in the upper extremities can interfere with activities of daily living (ADL) and, therefore, many interventions focus on improving impaired ROM. The question, however, is what joint angles are needed to naturally perform ADL. The present review aimed to compile and synthesize data from literature on shoulder and elbow angles that unimpaired participants used when performing ADL tasks. A search was conducted in PubMed, Cochrane, Scopus, CINAHL, and PEDro. Studies were eligible when shoulder (flexion, extension, abduction, adduction) and/or elbow (flexion, extension) angles were measured in unimpaired participants who were naturally performing ADL tasks, and angles were provided per task. Thirty-six studies involving a total of 66 ADL tasks were included. Results demonstrated that unimpaired participants used up to full elbow flexion (150°) in personal care, eating, and drinking tasks. For shoulder flexion and abduction approximately 130° was necessary. Specific ADL tasks were measured often, however, almost never for tasks such as dressing. The synthesized information can be used to interpret impairments on the individual level and to establish rehabilitation goals in terms of function and prevention of secondary conditions due to excessive use of compensatory movements.     

Kinematics of the contralateral and ipsilateral shoulder: a possible relationship with post-stroke shoulder pain.

OBJECTIVE: Post-stroke shoulder pain is a common phenomenon in hemiplegia and impedes rehabilitation. The aim of this study was to identify a possible relationship between post-stroke shoulder pain, scapula resting position and shoulder motion. METHODS: Shoulder kinematics of 27 patients after stroke (17 men) were compared with 10 healthy age-matched control subjects. Using an electromagnetic tracking device, the kinematics of both the contralateral and ipsilateral (i.e. paretic and non-paretic) arm during active and passive abduction and forward flexion were measured and expressed in Euler angles. RESULTS: Scapular lateral rotation relative to the thorax was increased in patients with post-stroke shoulder pain compared with both patients without post-stroke shoulder pain and control subjects at rest as well as during arm abduction and forward flexion. Additionally, glenohumeral elevation was decreased in patients with post-stroke shoulder pain during passive abduction. No differences were found regarding scapula position (displacement relative to the thorax). CONCLUSION: In patients with post-stroke shoulder pain a particular kinematical shoulder pattern was established, characterized by enhanced scapular lateral rotation and diminished glenohumeral mobility.     

A randomized controlled study of botulinum toxin A in the treatment of hemiplegic shoulder pain associated with spasticity

OBJECTIVES: To assess the effects of botulinum toxin A (BT-A) on hemiplegic shoulder pain associated with spasticity. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Outpatient clinic of a rehabilitation department. PARTICIPANTS: Patients, more than three months post stroke, with hemiplegic shoulder pain associated with shoulder adductor and elbow flexor spasticity, randomly assigned to BT-A or placebo. INTERVENTION: One-time injection of BT-A (500 units) into the pectoralis major and biceps brachii on the hemiplegic side. MAIN MEASURES: Visual analogue scale of shoulder pain (0 -10), shoulder adductor and elbow flexor tone using the Ashworth Scale and passive range of shoulder abduction. These were assessed at baseline, four weeks, eight weeks and 12 weeks post injection. RESULTS: Seventeen patients were enrolled, eight in the BT-A group and nine in the placebo group. At baseline, the median visual analogue scale score for shoulder pain was 6, the median Ashworth Scale shoulder adductor and elbow flexor spasticity score was 2 and the median range of shoulder abduction 76 degrees. Subjects who received BT-A showed significantly greater improvements in median shoulder adductor and elbow flexor Ashworth Scale scores than placebo at week 4 (P B / 0.01) but not at week 8 and 12. For shoulder pain and passive shoulder abduction range, all subjects showed postinjection improvements and no difference could be demonstrated between the two groups. DISCUSSION: Possible reasons for the negative finding in this study include the small sample size and the presence of causes of shoulder pain not related to spasticity which could have confounded outcome.     

Breast surgery and neural tissue mechanosensitivity

Arm pain is a complication following breast cancer surgery. This study examined the impact of breast surgery on the mechanosensitivity of upper quadrant neural tissues based on responses to a clinical provocation test. The responses of twenty patients to the ULTT 2a were recorded pre-operatively and six weeks post-operatively in terms of the available range of glenohumeral abduction and the area, nature and intensity of symptoms. The results indicated that there was a tendency towards increased neural tissue mechanosensitivity post-surgically, judged by a significant reduction in glenohumeral abduction range and a variance in symptoms in the operated arm. Unexpectedly, range of abduction reduced bilaterally suggesting that central as well as peripheral mechanisms may be involved in this response.     

Effectiveness of manipulative physiotherapy for the treatment of a neurogenic cervicobrachial pain syndrome: a single case study -- experimental design

A single case study ABC design was used to evaluate the effectiveness of manipulative physiotherapy in a 44-year-old woman with an 8-month history of neurogenic cervicobrachial pain. Clinical examination demonstrated significant signs of upper quadrant neural tissue mechanosensitivity indicating that neural tissue was the dominant tissue of origin for the subject's complaint of pain. Magnetic resonance imaging revealed correlating discal pathology at the C5/6 intersegmental level. The study involved a 4-week pre-assessment phase, a 4-week treatment phase and a 2-week home exercise phase. Functional disability was measured using the Northwick Park Neck Pain Questionnaire and pain was assessed using the McGill Short Form Pain Questionnaire. Cervical motion was measured by a cervical range of motion device (CROM) and the range of shoulder abduction with a mediclino inclinometer. Manipulative physiotherapy treatment involved a cervical lateral glide mobilization technique. Following treatment, visual analysis revealed beneficial effects on pain, functional disability as well as cervical and shoulder mobility. These improvements were maintained over the home exercise phase and at 1-month follow-up. The single case limits generalization of the findings, but the results support previous studies in this area and gives further impetus to controlled clinical trials.     

Rehabilitation of neck-shoulder pain in women industrial workers: a randomized trial comparing isometric shoulder endurance training with isometric shoulder strength training

OBJECTIVES: To study whether isometric shoulder endurance was more advantageous than isometric shoulder strength training in reducing pain and perceived exertion and to increase shoulder function through improved muscle endurance and strength. DESIGN: Randomized trial. SETTING: Three occupational health care centers. PARTICIPANTS: Women industrial workers with nonspecific neck-shoulder pain. The International Classification of Diseases, 10th Revision (ICD-10) diagnosis was "cervicobrachial syndrome" (M53.1). Thirty-eight patients completed the isometric shoulder endurance training and 31 patients completed the isometric shoulder strength training. INTERVENTION: Twelve weeks of training. MAIN OUTCOME MEASURES: Self-reported pain and rating of perceived exertion (RPE), arm motion performance test, shoulder muscle strength, shoulder muscle endurance, and shoulder functional tests, as well as follow-up after supervised training had ended. RESULTS: The isometric shoulder strength training resulted in an almost one-scale step decrease in RPE at work and a 5% to 15% improvement of arm motion performance compared with the endurance training. The isometric shoulder strength training more effectively improved left side shoulder abduction strength (p < .026), but no major differences were found for the other strength measurements. The isometric shoulder endurance training was not more successful than the strength training in the endurance test (p .51 to .81). CONCLUSIONS: Physical training programs for neck-shoulder pain may include isometric shoulder muscular strength exercise in addition to isometric shoulder endurance training, rather than endurance training only.     

A comparison of symptomatic and asymptomatic office workers performing monotonous keyboard work--2: neck and shoulder kinematics

Prolonged static posture has been identified as a major risk factor for work-related neck and upper limb disorders (WRNULD) in computer users. Previous research has mainly examined working postures in healthy pain-free individuals. The present study examined whether symptomatic subjects exhibited the same kinematic patterns as asymptomatic controls during a prolonged computer task. In a Case-Control comparison, female office workers performed the same computer task using the same adjustable computer workstation for 1h. Three-dimensional (3D) kinematics were measured in the head-neck, thorax and shoulder (upper arm) segments. Case Group subjects (n=21) displayed trends for increased head-neck flexion angles and greater ranges of movements than the Control Group (n=17). There were also small but significant differences between groups in side flexion and rotation angles of the head-neck region. The shoulder joints displayed significantly greater flexion and abduction angles on the right in both groups, although no group differences were observed. The increased neck flexion angles were associated with significantly higher activity in the upper trapezius muscle and with neck and shoulder discomfort. The individual differences in postural habits appeared to be independent of the physical environment. These results suggest motor control changes are associated with the presence of WRNULD.     

Comparison of acromiohumeral distance in symptomatic and asymptomatic patient shoulders and those of healthy controls

BackgroundThe reduction of the subacromial space has traditionally been linked to rotator cuff pathology. The contribution of this narrowing, both in the development and maintenance of rotator cuff tendinopathy, is still under debate. The objective of the present study was compare the acromiohumeral distance at 0 and 60 degrees of active shoulder abduction in scapular plane, static position, in both symptomatic and contralateral shoulders, between participants with unilateral rotator cuff related shoulder pain, and in asymptomatic participants.MethodThis was a cross-sectional observational study. Seventy-six participants with chronic shoulder pain were assessed. Forty participants without shoulder pain were also recruited to compare the acromiohumeral distance with symptomatic participants. The acromiohumeral distance was measured at 0 and 60 degrees of active shoulder abduction in all the groups by ultrasound imaging. Mean differences between symptomatic versus contralateral shoulders, and versus healthy controls, were calculated.FindingsThere were no statistical significant differences (p > .05) in the acromiohumeral distance at 0 degrees of shoulder elevation between the groups. However, significant differences were found at 60° between symptomatic and contralateral shoulder groups (0,51 mm; 95% CI: −0.90 to −0.12).InterpretationsDifferences in shoulder pain perception at 0° are not attributable to acromiohumeral distance differences. However, treatments focused on increasing AHD at 60° could be prescribed, as a significantly reduced AHD was found in symptomatic shoulders when compared with contralateral shoulders. Further research is needed to determine, not only static differences in AHD, but also dynamic differences.     

The Upper Limb Tension Test: Inter-tester Reliability for Assessing the Onset of Passive Resistance R 1

Abstract

The aim of this trial was to assess the inter-tester reliability of the Upper Limb Tension Test (ULTT). The onset of passive resistance (R1) of the left elbow was determined by four experienced manual therapists in a group of asymptomatic subjects. A recording of the degrees of elbow extension was obtained using a goniometer, having first positioned the upper extremity in a bracket maintaining 110 degrees of shoulder abduction and 10 degrees of shoulder extension. Each rater then moved the subjects' left shoulder into full external rotation and the forearm into full supination with the wrist and fingers in a neutral position. Data was collected four consecutive days. The data was analyzed by a two-way analysis of variance. The means of the readings among the four raters was found to be significantly different. It was concluded that the ULTT has a low inter-tester reliability when R1 is compared. Several suggestions are made for future research projects in this area.     

Forearm pain secondary to compression syndrome of the lateral cutaneous nerve of the forearm

This report describes a syndrome of compression of the lateral cutaneous nerve of the forearm (LCNF), the distal termination of the musculocutaneous nerve. Three patients presented with pain or numbness along the radial aspect of the distal forearm. There was a history of vigorous upper extremity exercise with elbow extension and arm pronation or resisted elbow flexion. Signs included: decreased sensation to pin and light touch in the distal forearm over the cutaneous distribution of the nerve; tenderness to palpation over the nerve where it pierces the deep fascia of the arm lateral to the bicipital tendon and proximal to the elbow crease; and decreased elbow extension with arm fully pronated. Electrodiagnostic studies revealed either a prolonged distal latency or decrease in amplitude of the evoked response of the lateral cutaneous nerve of the forearm in the symptomatic arm. Patients responded to treatment directed to the site of the lesion where the nerve pierces the deep fascia of the arm. Treatment methods included: restriction of upper extremity activity, use of a posterior splint to restrict elbow extension, transcutaneous electrical nerve stimulation (TENS), ultrasound, and surgical decompression. This syndrome may be readily differentiated from other causes of pain along the distal radial aspect of the forearm, making accurate diagnosis and treatment possible.     

Throwing kinematics and elbow varus torque relative to ball size in junior baseball players

[Purpose] The purpose of this study was to investigate changes in the shoulder and elbow joint angles, upper limb angular velocities, and elbow varus torque when throwing balls of two different sizes. [Participants and Methods] The pitching motion of 26 junior baseball players was analyzed using an optical motion capture system. The balls used were a standard baseball and a small ball of equal weight. Shoulder external rotation/abduction and elbow flexion were measured. The maximum values of shoulder joint internal rotation, elbow joint extension, wrist flexion angular velocity, and elbow joint varus torque were also evaluated. The ball velocity was determined as an index of pitching performance. [Results] The shoulder external rotation and elbow flexion angles were higher when pitching with a small ball. The joint angular velocity was also significantly higher when pitching with a small ball for all items examined. The ball speed was significantly higher with the small ball. The maximum varus torque of the elbow joint divided by the ball velocity was significantly lower for the small ball. [Conclusion] For a junior baseball player with a small hand length, using a small ball enables pitching with low stress on the elbow joint.     

Alterations in functional movement after axillary burn scar contracture: a motion analysis study

Children with axillary burns often develop scar contractures that restrict shoulder movement. Objective data on functional movement patterns after contracture formation is sparse. The purpose of this study was to determine how axillary contractures affect shoulder movement during activities of daily living (ADLs). This was a prospective study of children with axillary contractures scheduled for surgical release. Three-dimensional upper extremity kinematic analysis was used to assess shoulder, elbow, and trunk motion during two ADLs: high reach and hand to back pocket. Results were compared with a pool of 49 normal age-matched controls. Eleven children with axillary contractures were compared with controls. During high reach, significant decreases in shoulder flexion, shoulder internal rotation, arm pronation, and trunk extension occurred. Elbow flexion increased significantly. In the hand to back pocket task, shoulder extension and elbow flexion decreased and shoulder abduction increased. Axillary contractures result in quantifiable movement changes during ADLs. Aggressive rehabilitation is required to prevent contracture formation. Three-dimensional motion analysis is a unique tool for the quantification of functional limitations and provides an objective method to evaluate treatment efficacy in patients with axillary contractures.     

Mechanosensitivity of the median nerve and mechanically produced motor responses during Upper Limb Neurodynamic Test 1

Objectives

In spite of the widespread use and recognised importance of the Upper Limb Neurodynamic Test 1 (ULNT1) in clinical practice, controversy remains about the neurophysiological basis for sensory and motor responses to the test. The aims of this study were to determine the effects of two limb positions (neutral and ULNT1) on mechanosensitivity of the median nerve, and to investigate the mechanisms underlying muscle stiffness and loss of range during the elbow extension component of the ULNT1.

Design

In both limb positions, a KIN-COM^® dynamometer controlled passive elbow extension at 3°/second, and recorded both elbow extension range of movement and elbow flexor resistive torque.

Setting

Electrophysiology laboratory, School of Physiotherapy, University of South Australia.

Participants

Twenty-six asymptomatic subjects.

Main outcome measures

Range of elbow extension and elbow flexor resistive torque. Surface electrodes placed over 10 upper limb muscles recorded electromyographic (EMG) activity. Using a hand-held micro-switch, participants indicated occurrence of pain onset and pain that limited further movement.

Results

The median nerve was more sensitive to mechanical longitudinal stresses during passive elbow extension in the ULNT1 position than in the neutral position, as demonstrated by increased EMG activity and increased mean elbow flexor resistive torque (neutral position, 0.8 Nm, 95% confidence interval 0.7-0.9 Nm; ULNT1 position, 3.9 Nm, 95% confidence interval 3.8-4.0 Nm). Pain onset and pain limit occurred earlier in range in the ULNT1 position (pain onset, 45°, 95% confidence interval 40-50°) than in the neutral position (3°, 95% confidence interval 0-6°). In the ULNT1 position, EMG activity was greater in muscles responsible for an antalgic posture in the upper limb, although some EMG activity was evident prior to pain onset.

Conclusions

The mechanosensitivity of the median nerve was greater during elbow extension in the ULNT1 position than in the neutral position. The increased EMG activity that occurred primarily in muscles contributing to an antalgic posture with concurrent changes in resistive torque and range of movement may be explained by a flexor withdrawal response to pain that acts to reduce the stretch on the median nerve. Muscle activity prior to pain onset is probably due to mechanoreceptor activation following preferential stretch of the median nerve.     

A defective angina pectoris pain warning system: experimental findings of ischemic and electrical pain test

Ischemic pain threshold and tolerance levels using the tourniquet pain technique and electrical cutaneous pain thresholds were measured in patients with asymptomatic ischemic heart disease. Thirty asymptomatic patients, who repeatedly exhibited no angina pectoris pain during the occurrence of exercise-induced coronary ischemia (greater than or equal to 0.1 mV ST segment depression in exercise ECG) were compared to 30 randomly selected symptomatic control patients. In a smaller patient group (6 symptomatic, 6 asymptomatic) the degree of forearm ischemia during the tourniquet test was determined non-invasively by monitoring transcutaneous pO2. Results indicated that asymptomatic patients needed significantly more time to reach pain threshold following occlusion of forearm blood flow and exhibited significantly lower tcpO2 values at threshold than symptomatic patients. Electrical pain thresholds were also elevated in the asymptomatic group. These findings indicate that the phenomenon of asymptomatic myocardial ischemia can be explained by an extracardiac pain modifying mechanism.