Biomedical subjects

Andrew J Haig

Publications and source records attributed to Andrew J Haig.

At least 19 recordsLinked to original sources

PubMed2006

Predictors of pain and function in persons with spinal stenosis, low back pain, and no back pain.

STUDY DESIGN: Longitudinal masked, double-controlled cohort study. OBJECTIVES: To determine prognosis and predictors of function and pain in persons with spinal stenosis. SUMMARY OF BACKGROUND DATA: The clinical syndrome of spinal stenosis is common and disabling, but not clearly related to anatomic measures. Prognosis not well studied. METHODS: Persons 55 to 80 years of age with and without stenosis on preliminary review of magnetic resonance imaging (MRI), and asymptomatic volunteers underwent screening, questionnaires, physical examination, ambulation testing, masked electromyogram (EMG), and masked MRI scans; these were repeated at >18 months. RESULTS: Twenty-three asymptomatic, 28 back pain, and 32 clinically diagnosed stenosis subjects underwent follow-up. Although initial and follow-up diagnosis tended to agree (kappa = 0.394, P < 001), there were substantial shifts between the three groups. Among persons with clinically diagnosed stenosis, every measure trended for improvement, including significant changes in pain, ambulation, and EMG. Ambulation velocity and Pain Disability Index at follow-up were predicted by initial disability measures. Pain was predicted by initial sleep difficulty but not initial pain. EMG and MRI did not predict function or pain. CONCLUSION: Clinically recognized spinal stenosis is fluctuating and largely improving, and in continuum with back pain and no symptoms. Since anatomic and neurologic deficits do not predict future function, they should not be weighed heavily in surgical risk-benefit discussions.

Aged↗

PubMed2006

Comparing pain severity and functional status of older adults without spinal symptoms, with lumbar spinal stenosis, and with axial low back pain.

BACKGROUND: Functional status has been quantified in the adult low back pain (LBP) population, but has not been characterized for older adults with spinal symptoms. OBJECTIVES: To compare pain severity and functional status of older adults with and without spinal symptoms, and to determine what factors are associated with quality of life in the spinal stenosis and axial LBP groups. METHODS: In 24 subjects greater than 55-years old with lumbar spinal stenosis, 12 with LBP, and 12 without spinal symptoms, obtain the following: pain severity with 10-cm visual analog scale (VAS), 15-minute walk test, 7-day walking distance, Quebec Back Pain Disability Scale (QBPDS), and Pain Disability Index (PDI). RESULTS: The mean scores were worst for the stenosis group, were intermediate for the LBP group, and were the best for the asymptomatic group. Analysis of variance showed that the pain VAS (p < 0.001), 15-minute walk test (p = 0.01), 7-day walk (p = 0.02), QBPDS (p < 0.001), and PDI (p < 0.001) were different between at least two groups. All the variables in the stenosis group were worse than in the asymptomatic group, but only the pain VAS, QBPDS, and PDI in the LBP group were worse than in the asymptomatic group. In both the stenosis and LBP group the QBPDS and PDI were only related to pain VAS. CONCLUSION: Seniors with spinal stenosis and LBP have more disability than asymptomatic seniors. The 15-minute walking test with the stenosis group was slower than with the asymptomatic seniors. However, they compensate so that their 7-day walking distance is not as significantly decreased.

Activities of Daily Living↗

PubMed2006

The Spine Team Assessment for chronic back pain disability. Part 1: basic protocol and performance in 500 patients.

PURPOSE: For persons with chronic back pain disability, customized, effective, and efficient treatment depends on the initial assessment. Functional capacity evaluations and intake screenings for particular programs are not independent or goal-directed. This paper describes a standardized independent multidisciplinary assessment for treatment planning, and characteristic findings in a population of chronically disabled persons. METHODS: The Spine Team Assessment (STA), a (1/2)-day assessment including extensive intake information, evaluations by therapists and counselors, a team meeting with a physician, and a comprehensive report, was performed on 500 consecutive persons with chronic back pain. RESULTS: Representative findings included maximum cardiac performance of 5.33 (+/-4.08 SD) METS; Progressive Isoinertial Lifting Evaluation floor-to-waist of 36.4% (+/-23.9% of norms, and CESD depression scores of 24.7 (+/-13.5 SD). Fear and avoidance and poor physiologic effort were common. CONCLUSION: Deconditioning, psychosocial factors and functional deficits are common, complex, and variable among chronic back pain patients. This description of the STA provides a potentially reproducible standard for research into individualized treatment. The work provides benchmark data for independent multidisciplinary assessments.

Adult↗

PubMed2006

The Spine Team Assessment for chronic back pain disability. Part 2: team decision making and a preliminary outcome study.

PURPOSE: Back pain disability is complex, involving medical, physical, functional, social, and financial issues. This study aims to develop the first codified decision making process for individualized treatment planning. METHODS: In a multidisciplinary assessment protocol for chronic low back pain disability, the Spine Team Assessment (see Part I), a 'case law' qualitative approach to decision making began with a basic framework. Details were established over 103 cases at a community hospital. Through 500 more cases, a university spine program developed new exceptions, definitions, and rule clarifications. RESULTS: The final framework includes physical deconditioning, psychosocial factors, and potential for cure, with dozens of subcategories. Seventeen different combinations of therapy were recommended. Of 68 persons referred to one multidisciplinary treatment protocol, at 6 - 12 months the 17 completers had less work disability (31 vs. 62%, p = 0.032) and tended towards fewer subsequent diagnostic tests (17.6 vs. 34.7%) and less surgery (0 vs. 4). CONCLUSIONS: The data suggests that the process is complex, that customization did occur, and that at least one team decision led to better outcomes. While derived qualitatively, this decision-making tree provides a road map for less experienced teams and a precedent for researchers who wish to study individualized treatment.

Adult↗

PubMed2006

The bent spine syndrome: myopathy + biomechanics = symptoms.

BACKGROUND CONTEXT: The bent spine syndrome, which mimics spinal stenosis, is thought to be a focal paraspinal myopathy, but because paraspinal fatigue with ambulation is not a feature of more severe myopathies, the cause of symptoms is not clear. PURPOSE: To evaluate electromyographic and biomechanical aspects of the bent spine syndrome. STUDY DESIGN/SETTING: University spine clinic. METHODS: A patient with severe disability from the bent spine syndrome was compared with a fortuitously discovered asymptomatic research subject with the syndrome, in terms of physical examination, magnetic resonance imaging, and electrodiagnostic testing. RESULTS: Both subjects had fatty paraspinal replacement on magnetic resonance imaging and electromyography. More detailed electromyography of the patient showed abnormalities medially and caudally, but changes including apparent myopathic motor units up to the high thoracic region. The research subject had no hip flexion contracture, whereas the patient had severe contracture. Correction of contracture increased ambulation from 20 to 300 meters. CONCLUSIONS: Bent spine syndrome is likely a paraspinal myopathy, but symptoms do not occur unless there is also a hip flexion contracture.

Aged↗

PubMed2006

Spinal stenosis, back pain, or no symptoms at all? A masked study comparing radiologic and electrodiagnostic diagnoses to the clinical impression.

OBJECTIVE: To assess the relations between clinically recognized lumbar spinal stenosis and the conclusions of masked radiologists and electrodiagnosticians. DESIGN: Prospective, masked, double-controlled trial. SETTING: University spine center. PARTICIPANTS: One hundred fifty persons age 55 to 80 years with or without back pain and with or without magnetic resonance imaging (MRI)-demonstrated stenosis, screened for neuropathy risk, previous surgery, or cancer. INTERVENTIONS: Questionnaires on pain and function; ambulation testing and physical examination; and masked electrodiagnotics and MRI. MAIN OUTCOME MEASURE: Diagnostic impressions of the examining clinician, radiologist, and electrodiagnostician. RESULTS: Following application of post hoc exclusion criteria and elimination of patients due to incomplete or inadequate test data, the clinical diagnosis was lumbar stenosis in 50 subjects, back pain in 44 subjects, and no pain in 32 subjects. Radiologic and clinical impression had no relation (P = .80 vs asymptomatic, P = .99 vs back pain controls). Electrodiagnostic impression trended to relate to clinical impression (P = .14 vs asymptomatic, P = .09 vs back pain). Retrospective application of age-related electrodiagnostic norms for paraspinal electromyographic and limb motor unit changes, established in this study, reclassified 13 of the 17 asymptomatic persons whom the electrodiagnostician thought had stenosis. The clinical impression did correspond to history and physical examination findings typically associated with spinal stenosis and to the independent impression of a neurosurgeon who examined MRI and clinical, but not to the electrodiagnostic data. CONCLUSIONS: The impression obtained from an MRI scan does not determine whether lumbar stenosis is a cause of pain. Electrodiagnostic consultation may be useful, especially if age-related norms obtained in this study are applied.

Activities of Daily Living↗

PubMed2006

Assessment of the validity of masking in electrodiagnostic research.

OBJECTIVES: Performed by thousands of specialists and researched for >60 yrs, electrodiagnostic testing rates poorly in evidence-based guidelines in part because there are no valid masked research studies. This study assesses whether the electrodiagnostic examination can be adequately masked. DESIGN: Prospective, controlled, masked trial. A total of 150 persons aged 55-80 yrs, thought clinically to be asymptomatic (n = 32), with low back pain (n = 46), or with spinal stenosis (n = 63), underwent needle electromyography and nerve conduction studies by specialists in physical medicine and rehabilitation who were not permitted to ask any clinical information or to perform a formal examination. Examiners rated potential bias and recorded clues that might bias the examination. RESULTS: Examiners noted potential for bias in conversation in 17 and due to pain behavior in one. Half of these potential unmaskings pointed away from the correct clinical diagnosis, leaving potential for bias in <6% of the subjects. The clinical diagnosis had no relationship to electrodiagnostician rating of pain behavior in response to testing or repositioning, to limb atrophy, and to arthritis (P > 0.05 all instances). CONCLUSIONS: The electrodiagnostic examination can be successfully masked. This information will help future research in electrodiagnostics meet the criteria of evidence-based medicine.

Aged↗

PubMed2006

Changes in posture and perceived exertion in adolescents wearing backpacks with and without abdominal supports.

OBJECTIVE: The goal was to examine whether backpacks with an abdominal support device improve posture and decrease exertion while walking among adolescents. DESIGN: Double-blinded trial, with 20 subjects, performed at a University Spine Center. On day 1, adolescents walked on a treadmill for 5 mins with photographic measurement of posture and responded to the Borg scale of perceived exertion before and after ambulation. On day 2, they repeated the trial four more times wearing a backpack randomly loaded with either 10% or 20% of body weight and with or without the Back Balancer abdominal support. Postural measures were recorded by a blinded observer. RESULTS: Postural changes (forward lean) wearing a backpack with abdominal support were significantly lower while carrying both 10% and 20% of body weight (P = 0.024 and P = 0.008, respectively) vs. no abdominal support. In addition, perceived exertion at 10% and 20% of body weight was significantly greater without abdominal support (P = 0.042 and P = 0.018, respectively). CONCLUSIONS: Forward lean and perceived exertion while wearing backpacks in adolescents can be significantly decreased with abdominal support. This may increase comfort and decrease complications, such as back pain, that may arise from backpack use.

Abdomen↗

PubMed2006

Specificity of needle electromyography for lumbar radiculopathy and plexopathy in 55- to 79-year-old asymptomatic subjects.

OBJECTIVE: Determine specificity of needle electromyography for lumbar radiculopathy and plexopathy using a blinded study design. DESIGN: Asymptomatic community volunteers ages 55 and older, as part of a spinal stenosis study, were given a standardized electrodiagnostic evaluation by a blinded electromyographer. A monopolar needle was used to evaluate five leg muscles and the lumbar paraspinal muscles. The specificities of different diagnostic criteria for radiculopathy and plexopathy were then calculated. RESULTS: There were 30 subjects with a mean age of 65.4 yrs (SD 8.0). When only positive sharp waves or fibrillations were counted as abnormal, most of the diagnostic criteria (two limb muscles plus associated lumbar paraspinal muscle abnormal, two limb muscles abnormal, or one limb muscle plus associated lumbar paraspinal muscle abnormal) had 100% specificity. When we also included at least 30% polyphasia in the limb muscles as abnormal, the respective specificities were 97, 90, and 87%. When we also included at least 20% polyphasia in the limb muscles as abnormal, the respective specificities were 77, 60, and 60%. The specificity for plexopathy was 100% when only positive sharp waves or fibrillations were used, and it remained 100% when increased polyphasia was added. CONCLUSION: Needle electromyography has excellent specificity for lumbosacral radiculopathy and plexopathy when appropriate diagnostic criteria are used.

Aged↗

PubMed2005

The sensitivity and specificity of electrodiagnostic testing for the clinical syndrome of lumbar spinal stenosis.

STUDY DESIGN: Prospective, masked, double controlled diagnostic trial. OBJECTIVES: To determine the sensitivity and specificity of electrodiagnostic consultation (EDX) for the clinical syndrome of lumbar spinal stenosis. SUMMARY OF BACKGROUND DATA: EDX has been used for more than 50 years to diagnose spinal disorders but has not met the new standards of evidence-based medicine. METHODS: A total of 150 subjects (asymptomatic volunteers and patients with MRIs suggesting back pain or spinal stenosis; 55-80 years of age) underwent physiatrist history and physical examination, MRI, and review of this data by a neurosurgeon, with each clinician masked to any outside information, leading to a unanimous consensus on diagnosis in 55. After masked EDX testing, 7 subjects with undiagnosed neuromuscular disease were discovered. EDX findings were related to "clinical gold standard" diagnoses in 48 persons. RESULTS: Paraspinal mapping EMG score of >4 had 100% specificity and 30% sensitivity for stenosis compared with either the back pain or asymptomatic groups (each, P < 0.04). A composite limb and paraspinal fibrillation score had a sensitivity of 47.8% and specificity of 87.5% (P = 0.008), and H-wave sensitivity was 36.4, specificity 91.3 (P = 0.026) for stenosis versus all controls. CONCLUSIONS: This first masked study in the 60-year history of needle electromyography also introduces anatomically validated needle placement, quantified and reproducible examination of the paraspinal muscles, and dual control populations to EDX research in spinal disorders. EDX has statistically significant, clinically meaningful specificity for spinal stenosis and detects neuromuscular diseases that may masquerade as stenosis.

Aged↗

PubMed2005

Paraspinal electromyography: age-correlated normative values in asymptomatic subjects.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: To determine if the amount of lumbar paraspinal denervation increases with age and present normative data on the amount of denervation present in asymptomatic subjects. SUMMARY OF BACKGROUND DATA: To our knowledge, there are no data on the relationship of paraspinal denervation with age or normative data on the amount of denervation expected in asymptomatic older adults. METHODS: We combined the data from our current study of asymptomatic adults, age 55-79 years, and a previous study of asymptomatic adults, age 18-58 years, who underwent lumbar paraspinal muscle needle electromyography using a validated needle electromyography (MiniPM) technique. We then compared the results of the age group 55-79 to that of the age group 18-54. RESULTS: The older group scored significantly higher than the younger group by 1.7 (P = 0.008, 95% confidence interval 0.5-3.0). Linear regression showed that age was a significant predictor of the MiniPM score (beta = 0.04, and P = 0.04). For subjects 55 years and older, mean MiniPM score on one side was 2.3 (standard deviation 3.6). The upper range of the 95th percentile was 10. CONCLUSIONS: The amount of lumbar paraspinal muscle denervation does increase with age. Understanding the range of findings in asymptomatic subjects will help us interpret lumbar paraspinal needle electromyography findings in patients with spinal disorders.

Adult↗

PubMed2005

A meta-analytic review of surface electromyography among persons with low back pain and normal, healthy controls.

UNLABELLED: Significant differences in surface electromyography (SEMG) have been reported between persons with low back pain (LBP) and normal, healthy controls. This manuscript presents a systematic meta-analytic review of studies examining SEMG differences between these groups. Forty-four articles were identified using MEDLINE and a review of reference lists in articles. For static SEMG, the largest effect size was observed for SEMG while standing, with subjects having LBP demonstrating higher SEMG. The effect size for flexion/relaxation measures was found to be very high (d = -1.71). Studies examining SEMG during isometric exercise or muscle recovery following exercise produced inconsistent findings. Sensitivity and specificity of SEMG for dynamic SEMG measures averaged 88.8% and 81.3%. Most classification schemes were statistically determined and utilized a combination of measures. Only one published study prospectively validated a classification scheme. SEMG measures of flexion-relaxation appear to distinguish LBP subjects from controls with good accuracy, and the sensitivity and specificity of SEMG can be increased by using multiple measures. Further research is needed to determine the combination of measures that are cost-effective, reliable, valid and discriminate with a high degree of accuracy between healthy persons and those with LBP. PERSPECTIVE: SEMG is a simple and noninvasive measure of muscle activity. SEMG measures hold promise as an objective marker of LBP.

Action Potentials↗

PubMed2003

Alcohol use self report in chronic back pain--relationships to psychosocial factors, function performance, and medication use.

BACKGROUND CONTEXT: Alcohol consumption is a known risk factor for spinal disability, but there is no data on the relationship between reported alcohol consumption and behaviours in persons who are disabled. PURPOSE: To determine the interaction between reported alcohol consumption, physical performance, and medication use in this group. To determine psychosocial correlates of reported alcohol consumption in this group. METHODS: A retrospective review 147 men and 136 women with more than 3 months disability who underwent a multidisciplinary physical, functional and psychosocial Spine Team Assessment. Questions about alcohol consumption were related to outcome measures. RESULTS: None of the women reported more than 5 drinks/week. Ten men reported more than 12 drinks per week. These performed significantly better on the Progressive Isoinertial Lifting Evaluation (PILE) low lift and the Functional Assessment Screening Test (FAST) 5 minute twisting test, and trended towards better performance on all other tests (the PILE high lift, all 4 other FAST components, Sorenson trunk extension test, and bicycle ergometer submaximal stress test). They had less back pain disability (Quebec p = 0.061), but no difference in depression (CESD), pain (visual analog scale) or fear (Tampa). They used fewer Non-steroidal medications, but similar narcotic medications as the others. No significant differences in the SF-36 were noted. CONCLUSIONS: This first assessment of the relationship of alcohol consumption with back pain disability suggests that women with chronic back pain disability seldom report heavy alcohol consumption. Men with back pain disability who consume large amounts of alcohol have less physical disability despite similar pain. Despite potential interactions, heavy drinkers with pain do not use fewer narcotic analgesics than light drinkers.

Adult↗

PubMed2003

Low back pain in adult female caregivers of children with physical disabilities.

BACKGROUND: Low back pain (LBP) in occupational settings has been studied extensively. There are fewer studies on LBP in domestic settings, especially in an informal caregiving setting. OBJECTIVES: To compare the prevalence of LBP in adult female primary caregivers of children with physical disabilities who need assistance with transfers (eg, moving from a bed to a wheelchair) with the prevalence of LBP in adult female primary caregivers of children with nondisabling medical illnesses and to evaluate the factors associated with LBP. DESIGN: A 15-minute, self-administered, cross-sectional survey. SETTING: University-based clinics. Subjects Ninety consecutive adult female caregivers of children presenting to a pediatric physical medicine and rehabilitation clinic and 23 consecutive adult female caregivers of children presenting to a pediatric endocrine clinic were studied. General exclusionary criteria included the following: male sex, a history of back surgery or fracture, the caregiver was younger than 18 years old at the time of the completion of the questionnaire, or the caregiver was caring for any child younger than 2 years old. Caregivers visiting the pediatric endocrine clinic were excluded if they were caring for 1 or more children needing assistance with transfers. MAIN OUTCOME MEASURES: The dependent variable was the presence of LBP. The independent variables were mood, work status, amount of lifting at work, physical functioning of the child, demographic variables of the caregiver, and demographic variables of the child. RESULTS: The prevalence of having LBP (71.1%) in the physical medicine and rehabilitation group is higher than the prevalence (43.5%) in the endocrine clinic group (odds ratio, 3.2; 95% confidence interval, 1.25-8.21). The prevalence of having LBP (80.3%) when the child required physical assistance with transfers was significantly higher than the prevalence (40.5%) when the child did not require physical assistance with transfers (odds ratio, 2.56; 95% confidence interval, 2.56-14.0). Forward multiple logistic regression showed that the factors related to LBP in the caregiver were the transferability of the child, mood of the caregiver, and a history of LBP in the caregiver. CONCLUSIONS: The prevalence of LBP is higher in caregivers of children needing assistance with transfers. This increased prevalence is associated with the transferability of the child and mood of the caregiver. Results of this study suggest that physical and psychological factors both contribute to the presence of nonoccupational LBP.

Adult↗

PubMed2003

The accuracy of needle placement in lower-limb muscles: a blinded study.

OBJECTIVE: To assess the accuracy of common anatomic guides for electromyographic needle placement in muscles. DESIGN: Blinded study. The dissector identified different needle placements by a random number attached to a wire in the insertion site. SETTING: A university anatomy laboratory. CADAVERS: Ten cadaver lower limbs. INTERVENTIONS: By using techniques published in texts by Gieringer and Delagi and Perotto, clinical electromyographers palpated and measured appropriate locations for needle placement. A thin wire was inserted through the needle into 36 different muscles in 10 cadavers, resulting in 263 targeted muscles. An anatomist blinded to intended location dissected and recorded muscles and other tissues that the wire pierced or passed near. MAIN OUTCOME MEASURES: Targeted muscle penetration, final resting place of the wire tip, and proximity to vital structures. RESULTS: Fifty-seven percent of insertions penetrated the intended muscle. The wire tip was in the intended muscle 45% of the time. Seventeen percent of insertions penetrated or passed within 5mm of an important structure, including nerve (9.1%), tendon (3.0%), named artery (2.7%), vein (2.7%), or joint (0.8%). Specific muscle accuracy was highly variable, from 0% for 12 tries in various deep hip muscles to 100% of 10 tries in the vastus medialis. CONCLUSION: The accuracy of blind needle placement varied according to muscle. With the blind insertion technique, more accurate and safe needle placement strategies can be developed.

Cadaver↗

PubMed2003

The effect of order of testing in functional performance in persons with and without chronic back pain.

Batteries of individually standardized physical and functional tests are commonly used to assess persons with chronic back pain disability. The order of testing may affect performance on later tests. One hundred and fifty patients with > 3 months of back pain disability underwent a multidisciplinary Spine Team Assessment involving Physical Therapy, Occupational Therapy, Pain Psychology, and Vocational Rehabilitation Counselor assessments at a university spine clinic. Seventeen back healthy volunteers performed the physical component of the assessment. For the volunteers the order of testing was randomized to OT tests first or PT test first, with 0.5 h rest between the tests. For patients the order of testing was arbitrarily set by an alternating schedule, with 1 h psychological testing between the two components. For both the patients and volunteers, among the 14 test components, there was no significant difference (p > 0.05) in performance with order of testing. This held true for the subgroup of patients who put out good cardiac effort. Volunteers performed better than patients on all individual tests (p < 0.001). Results suggest that the order of physical testing during a Spine Team Assessment does not affect test performance either in chronic low back disabled patients or in volunteers.

Adult↗

PubMed2003

Paraspinal electromyography that compares concentric with monopolar needles: a blinded study.

OBJECTIVE: To establish interrater reliability for paraspinal muscle needle electromyography study with both monopolar and concentric needles in symptomatic and asymptomatic persons and to further establish normative data for paraspinal needle study. DESIGN: At a university spine center, participants with and without radiating low back pain were evaluated with the mini-paraspinal mapping paraspinal needle technique by an unblinded and a blinded electromyographer. RESULTS: In the symptomatic group, the intraclass correlation coefficient between concentric and monopolar needles was 0.793; between monopolar needles, it was 0.876; and between concentric needles, it was 0.966. In the asymptomatic group, the mean total score was 0.25. CONCLUSIONS: The good interrater reliability with the same needle type helps support the validity of the needle electromyography study of the paraspinal muscles. The good correlation between the concentric and monopolar needles shows the data published using monopolar needle data also apply to studies using paraspinal needle electromyography with concentric needles. The low score with the asymptomatic group reaffirms that using a cutoff score of >2 as abnormal has a false-positive rate of <5%.

Adolescent↗

PubMed2002

The relation among spinal geometry on MRI, paraspinal electromyographic abnormalities, and age in persons referred for electrodiagnostic testing of low back symptoms.

STUDY DESIGN: A retrospective EMG study with blinded radiologic measurement was conducted. OBJECTIVE: To determine the relation among spinal measurements on MRI, paraspinal denervation, and age in patients referred for electrodiagnostic and radiologic evaluation of low back pain. SUMMARY OF BACKGROUND DATA: Spinal pathology, including disc herniation and spinal stenosis, can cause denervation of the paraspinal muscles. Various mechanisms including direct compression, inflammation, vascular compromise, and mechanical stretch of the posterior primary ramus may play a role in denervation. The relation between the amount of denervation and the size of the spinal canal can assist in understanding the pathophysiology of back pain. Since paraspinal denervation may increase with age in asymptomatic persons, age is an important covariable. METHODS: At a university hospital, 44 patients referred to undergo both electrodiagnostic evaluation and MRI for low back pain were studied. The study investigated the relation among the following: 1) axial MRI spinal measurements (canal transverse diameter, anteroposterior diameter, and area; thecal sac anteroposterior diameter and area; and the radiologist's overall impression at each level) and denervation measurements in terms of scores on the MiniPM, a quantified needle electromyographic measure of paraspinal denervation; 2) various models of multilevel spinal compression (smallest, smallest two, and average spinal levels for each measurement) and MiniPM scores; and 3) MRI spinal canal measurements and age. RESULTS: Although individual MRI measurements and combinations of measurements did not relate to MiniPM scores, the radiologist's impression was significantly related. The "smallest two" levels measurement had the strongest relation (r = 0.400; P < 0.007). Age related to the MiniPM scores (P = 0.004) and radiologic impression (P = 0.031). A regression suggested that MiniPM was an independent predictor of age. CONCLUSIONS: The radiologist's overall impression is more accurate than axial image measurements in predicting paraspinal denervation. A combination score of the smallest two levels is the most accurate, perhaps relating to the vascular pathophysiology of stenosis. There is more denervation with increasing age in this symptomatic population.

Age Factors↗