Using Provocative Discography and Computed Tomography to Select Patients with Refractory Discogenic Low Back Pain for Lumbar Fusion Surgery.

Background Context Controversy remains over the use of provocative discography in conjunction with computed tomography (CT) to locate symptomatic intervertebral discs in patients with chronic, low back pain (LBP). The current study explores the relationship between discogenic pain and disc morphology using discography and CT, respectively, and investigates the efficacy of this combined method in identifying surgical candidates for lumbar fusion by evaluating outcomes. Methods 43 consecutive patients between 2006 and 2013 who presented with refractory low back pain and underwent discography and CT were enrolled in the study. For this study, "refractory LBP" was defined as pain symptoms that persisted or worsened after 6 months of non-operative treatments. Concordant pain was defined as discography-provoked LBP of similar character and location with an intensity of ≥ 8/10. Fusion candidates demonstrated positive-level discography and concordant annular tears on CT at no more than two contiguous levels, and at least one negative control disc with intact annulus. Surgical outcomes were statistically analyzed using Visual Analog Scale (VAS), Oswestry Disability Index (ODI), and Short Form-36 (SF-36) for back-related pain and disability preoperatively, and 2 weeks, 3, 6, 12, and 24 months postoperatively. Results Annular tears were found in 87 discs. Concordant pain was reported by 9 (20.9%) patients at L3-L4, 21 (50.0%) at L4-L5, and 34 (82.9%) at L5-S1; pain occurred significantly more often in discs with annular tears than those without (p<0.001). Painless discs were independent of annulus status (p=0.90). 18 (42%) of the original 43 patients underwent lumbar fusion at L3-L4 (n=1(6%)), L4-L5 (n=6 (33%)), L5-S1 (n=5 (28%)), and two-level L4-S1 (n=6 (33%)) via a minimally invasive transforaminal lumbar interbody fusion (MITLIF) approach with the aim to replace the nucleus pulposus with bone graft material. Median follow-up time was 18 months (range: 12-78 months). VAS, ODI, and SF-36 scores demonstrated significant improvements at 10 out of 12 postoperative time points compared with preoperative baseline. Conclusions Lumbar discography with post-discography CT can be an effective method to evaluate patients with discogenic back pain refractory to non-operative treatments. Those patients with one- or two-level high concordant pain scores with associated annular tears and negative control disc represent good surgical candidates for lumbar interbody spinal fusion.

Correlation of paraspinal atrophy and denervation in back pain and spinal stenosis relative to asymptomatic controls.

OBJECTIVE: To determine the relationship among spinal stenosis, back pain, paraspinal muscle denervation, and paraspinal muscle atrophy. DESIGN: A prospective masked, double-controlled study. SETTING: A university hospital and outpatient spine clinic. PARTICIPANTS: Ten asymptomatic subjects, 10 subjects with mechanical low back pain, and 15 subjects with symptomatic spinal stenosis; age range, 55-80 years old. INTERVENTIONS: Magnetic resonance imaging measurements of minimum spinal canal diameter, paraspinal muscle cross-sectional area at the level of the L5-S1 disk, and quantified paraspinal electrodiagnostic testing (MiniPM) were performed by examiners blinded to each other's results and to the participants' clinical information. MAIN OUTCOME MEASUREMENTS: Paraspinal muscle cross-sectional area and MiniPM scores. RESULTS: A paraspinal cross-sectional area decreased significantly from asymptomatic subjects (3872 mm(2)) to subjects with low back pain (3627 mm(2)) and to subjects with spinal stenosis (2985 mm(2)). In the stenosis group, there was a trend toward increased paraspinal denervation in the subjects with severe spinal stenosis, but this was not statistically significant. CONCLUSIONS: Symptomatic spinal stenosis results in greater paraspinal muscle atrophy than low back pain alone. The extent of paraspinal atrophy was not significantly explained by the extent of denervation, thus, it may be reversible, and the role of paraspinal muscle rehabilitation in patients with spinal stenosis deserves further study.

Incremental ability of needle electromyography to detect radiculopathy in patients with radiating low back pain using different diagnostic criteria.

OBJECTIVE: To determine the incremental ability of different needle electromyography diagnostic criteria to detect lumbar radiculopathy. DESIGN: Blinded cross-sectional study. SETTING: University hospital. PARTICIPANTS: Subjects aged 55 to 80 years with radiating low back pain (n=48; mean age ± SD, 67.9±7.3y) and who were asymptomatic (n=30; mean age ± SD, 65.4±8y). INTERVENTIONS: Electrodiagnostic evaluation by a blinded electromyographer. A monopolar needle was used to evaluate 5 leg muscles and the lumbar paraspinal muscles. MAIN OUTCOME MEASURES: Presence or absence of radiculopathy using different electrodiagnostic criteria. RESULTS: When only positive sharp waves or fibrillations were considered, and at least 2 muscles innervated by the same root level and different peripheral nerves were counted as abnormal, 27.1% (13/48) of participants had positive results for radiculopathy. When at least 30% motor unit action potential changes in the limb muscles were also considered, participants with positive results increased to 45.8% (22/48), which was significant when compared with the first criterion (P=.002). When the mini-paraspinal mapping (MiniPM) test as well as at least a 30% motor unit cutoff was used, participants with positive results increased to 50% (24/48), which was significant when compared with the first criterion (P=.001). CONCLUSIONS: In addition to the presence of positive sharp waves or fibrillations, considering greater than or equal to 30% motor unit action unit potential changes as well as the MiniPM score maintains good specificity and improves the ability of the needle electromyography study to detect lumbar radiculopathy in subjects with radiating low back pain.

Differential aging of median and ulnar sensory nerve parameters.

INTRODUCTION: Nerve conduction velocity slows and amplitude declines with aging. METHODS: Median and ulnar sensory nerves were tested at the annual meetings of the American Dental Association. Seven hundred four subjects had at least two observations. The rate of change in the nerve parameters was estimated while controlling for gender, age, change in hand temperature, baseline body mass index (BMI), and change in BMI. RESULTS: Amplitudes of the median sensory nerve action potentials decreased by 0.58 µV per year, whereas conduction velocity decreased at a rate of 0.41 m/s per year. Corresponding values for the ulnar nerve were 0.89 µV and 0.29 m/s per year. The rates of change in amplitudes did not differ, but the median nerve demonstrated a more rapid loss of conduction velocity. CONCLUSIONS: The rate of change for the median conduction velocity was higher than previously reported. The rate of change of median conduction velocity was significantly greater than for the ulnar nerve.

Specificity of needle electromyography for lumbar radiculopathy in 55- to 79-yr-old subjects with low back pain and sciatica without stenosis.

OBJECTIVE: The aim of this study was to determine the specificity of needle electromyography for lumbar radiculopathy in subjects with low back pain and sciatica without stenosis. DESIGN: Subjects 55 yrs or older with diagnoses of low back pain and sciatica underwent a standardized monopolar needle evaluation by blinded electromyographers as part of a spinal stenosis study. The presence or absence of radiculopathy was determined using different electrodiagnostic criteria. RESULTS: Seventy-two subjects with a mean age of 64.6 years (SD, 7.0 yrs) were studied. When only positive sharp waves or fibrillations were considered abnormal, most of the diagnostic criteria--two limb muscles + associated lumbar paraspinal muscle abnormal, two limb muscles abnormal, or one limb muscle + associated lumbar paraspinal muscle abnormal--had 97%, 96%, and 92% specificity, respectively. When 30% or greater polyphasia in the limb muscles was also considered abnormal, the respective specificities were 90%, 81%, and 85%. When 20% or greater polyphasia in the limb muscles was also considered abnormal, the respective specificities were 90%, 74%, and 71% [corrected]. CONCLUSIONS: There is good specificity for lumbosacral radiculopathy when appropriate diagnostic criteria are used.

Spinal canal size and clinical symptoms among persons diagnosed with lumbar spinal stenosis.

OBJECTIVE: Clinical symptoms associated with lumbar spinal stenosis (LSS) are believed to be due to neurogenic claudication caused by narrowing of the central and lateral spinal canals. However, there is a paucity of published data on these relationships. The purpose of the present study was to examine the relationship between clinical symptoms associated with LSS and osseous anterior-posterior (AP) spinal canal diameter as measured on axial magnetic resonance imaging. DESIGN: Cross-sectional study conducted at a University Spine Program. Fifty persons with a clinical diagnosis of LSS were administered measures of clinical pain and perceived function. Walking distance in the laboratory and community was also assessed. Participants also underwent magnetic resonance imaging of the spine. RESULTS: Using recommended upper limits from the literature, patients with smaller canals reported greater perceived disability, but no other group differences emerged. In the entire sample, AP spinal canal diameter was not significantly associated with any of the clinical symptom measures examined. Body mass index was found to be significantly related to walking distance, but not perceived function or pain. CONCLUSIONS: AP spinal canal diameter is not predictive of clinical symptoms associated with LSS. The findings also suggest that body mass may play a significant role in functional limitations observed in this population.

Comparing saphenous nerve conduction study techniques at the knee and at the ankle and their relationship to body mass index.

OBJECTIVE: To evaluate the saphenous sensory response by 2 methods and the correlation of obtaining responses bilaterally with body mass index (BMI). DESIGN: Twenty patients evaluated by 1 electromyographer and 10 patients evaluated by 2 blinded electromyographers. SETTING: University electromyography laboratory. PARTICIPANTS: Thirty healthy adult volunteers. INTERVENTIONS: Saphenous sensory response with the recording electrode at the level of the medial malleolus, saphenous sensory response with the recording electrode at the level of the proximal tibia, and sural sensory response with the recording electrode posterior to the lateral malleolus. MAIN OUTCOME MEASURES: Sensory-evoked amplitude and distal latency. RESULTS: The saphenous sensory response was obtained bilaterally at the knee in 77% of subjects, whereas it was obtained bilaterally at the ankle in only 50% of subjects (P<.05). BMI of greater than 25 kg/m2 resulted in more difficulty in obtaining the saphenous sensory response at the ankle compared with the response at the knee (P<.05). CONCLUSIONS: The saphenous sensory response at the knee is more consistently obtained than the saphenous sensory response at the ankle, and it is not affected by BMI.

Electromyographic and magnetic resonance imaging to predict lumbar stenosis, low-back pain, and no back symptoms.

BACKGROUND: Magnetic resonance imaging is commonly used to diagnose lumbar spinal stenosis. Some persons without symptoms have a small lumbar spinal canal. Electrodiagnosis has been used to diagnose spinal stenosis for over sixty years, but we are aware of no masked, controlled trials of the use of electrodiagnosis for that purpose. This study was performed to evaluate the relationships of magnetic resonance imaging measures and electrodiagnostic data with the clinical syndrome of spinal stenosis. METHODS: One hundred and fifty persons between the ages of fifty-five and eighty years old, including asymptomatic volunteers and persons referred for lumbar magnetic resonance imaging, underwent clinical examination, electrodiagnosis, and magnetic resonance imaging. Subjects were excluded if they had neuromuscular disease, sacral cancer, or inadequate test results, which left 126 subjects for the final analysis. The final cohort was divided into three groups--no back pain, mechanical back pain, and clinical spinal stenosis--on the basis of the impression of the examining physician, for whom the results of the magnetic resonance imaging and electrodiagnostic testing were masked. A spine surgeon also reviewed both the imaging and clinical examination data. RESULTS: The examining physician's diagnosis of clinical spinal stenosis was significantly related to the neurological findings on examination (p < 0.05) and to the spine surgeon's diagnosis (p < 0.001). The diagnosis of clinical spinal stenosis was also significantly related to the presence of fibrillations on electrodiagnostic testing (p < or = 0.003), the minimum anteroposterior diameter of the spinal canal on the magnetic resonance images (p = 0.016), and the average of the two smallest spinal canal diameters (p = 0.008) on the images. Measurements on magnetic resonance imaging did not differentiate subjects with clinical spinal stenosis from controls better than chance, whereas paraspinal mapping electrodiagnosis scores did. CONCLUSIONS: This prospective, controlled, masked study of electrodiagnosis and magnetic resonance imaging for older subjects showed that imaging does not differentiate symptomatic from asymptomatic persons, whereas electrodiagnosis does. We believe that radiographic findings alone are insufficient to justify treatment for spinal stenosis.

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.

Ability of early response to predict discharge outcomes with physical therapy for chronic low back pain.

OBJECTIVE: To determine how well early responses to physical therapy for chronic low back pain predict outcomes at discharge. METHODS: A prospective single cohort study of chronic low back pain patients seen at a university spine physical therapy clinic. Self-reported pain severity on a 100-mm visual analog scale was measured before each physical therapy visit. The predictive variables were the change in pain score at the second, third, and fourth visits. The first outcome variable was discharge change in pain severity for a correlation analysis. The second outcome variable was a dichotomous variable of whether the subjects had achieved at least a 30% reduction in pain severity at discharge for a discriminant analysis. RESULTS: Spearman's rank order correlation coefficient showed that early responses at the second (r = 0.324, P = 0.02) third (r = 0.342, P = 0.01), and fourth visits (r = 0.615, P < 0.001) were all significantly correlated with discharge change in pain. The discriminant analysis showed that early responses from the second to fourth visits were able to correctly predict 80.4% of the discharge outcomes (P < 0.001). CONCLUSIONS: Early responses with physical therapy help predict discharge outcomes for chronic low back pain.

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.

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.

Interexaminer reliability of three methods of combining test results to determine side of sacral restriction, sacral base position, and innominate bone position.

CONTEXT: Sacroiliac joint dysfunction is diagnosed based on the combined results of several palpatory examinations. Previous studies have compared the interexaminer reliability of only one of these methods of diagnosis. OBJECTIVE: To compare the interexaminer reliability of three methods of combining palpatory examinations to determine the side of sacroiliac joint dysfunction, sacral base position, and innominate bone position. DESIGN: Blinded single-cohort reliability study. METHODS: Patients with low back pain underwent two identical sets of palpatory examinations given by two physicians, separately, at a university spine center. The results of each set were compiled and interpreted by three methods: using the test result with the highest interexaminer reliability (method 1), requiring at least one test result to be abnormal for the variable to be abnormal (method 2), and requiring all test results to be abnormal for the variable to be abnormal (method 3). The kappa was calculated for each method. RESULTS: There were 24 subjects (mean age, 68.3 years), of which 15 (62%) were women. The kappa was consistently higher with method 1, at 0.47, 0.08, and 0.32 for the sacral position, innominate bone position, and side of sacroiliac joint dysfunction, respectively. Corresponding values for method 2 were 0.09, 0.4, and 0.16, and for method 3 were 0.16, 0.1, and -0.33. CONCLUSION: Using the results of the most reliable examination consistently has the best interexaminer reliability.

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.

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.

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.

Manual acupuncture for analgesia during electromyography: a pilot study.

OBJECTIVES: To evaluate the analgesic effect of acupuncture for needle electromyography and to validate a sham acupuncture needle. DESIGN: Randomized, double-blinded, controlled study. SETTING: University-based electrodiagnostics laboratory. PARTICIPANTS: Fifty-one subjects referred for electrodiagnostic evaluation. INTERVENTIONS: Before the electromyography examination, either real acupuncture needles or telescopic sham needles were applied. MAIN OUTCOME MEASURES: Visual analog scale of pain and unpleasantness after 3 muscles were examined with electromyography. Pretest pain was subtracted to give a measurement of pain attributable to the electromyography. Subjects were asked which needle they thought they had received. RESULTS: Twenty-six subjects were randomized to the treatment group and 25 to the sham group. Pain in the treatment group (-.96) was less than in the control group (9.68), but it was not statistically significant (P=.13). Post hoc analysis, excluding 5 subjects known to have been treated by the novice acupuncturist, showed a significant difference of 14.4mm (P=.02). The proportion of subjects who thought they received real needles in the acupuncture group (69%) did not differ from the proportion in the control group (48%) (P=.13). CONCLUSIONS: Acupuncture may represent an effective form of analgesia for electromyography. This is the first study to suggest independently the telescopic sham acupuncture needle as an effective control.

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.

Effect of aging on sensory nerve conduction study parameters.

Research evaluating the changes in nerve conduction with time has been limited to cross-sectional studies. We present a cohort study estimating how sensory nerve conduction study (NCS) parameters change with time when subjects are measured at two time-points. We evaluated 440 working adults by performing median and ulnar antidromic sensory NCS of both hands on two occasions, about 5.4 years (range, 4.3-7.0 years) apart. The rate of change in the NCS parameters was estimated using a mixed-models analysis controlling for each hand, gender, age, and body mass index (BMI). After controlling for gender, age, height, and BMI, the amplitudes of the median sensory nerve action potentials (SNAP) decreased by about 2.3 microV, peak latencies increased by 0.11 ms, onset latencies increased by 0.07 ms, and conduction velocities decreased by 1.1 m/s over 5 years. Corresponding values for the ulnar nerve were 1.75 microV, 0.06 ms, 0.04 ms, and 0.71 m/s, respectively. The findings are consistent with the findings of previous cross-sectional studies. The rate of change over time was not affected by hand (dominant versus nondominant hand), gender, age, or BMI at baseline. The rate of change seen with some of the median nerve parameters was significantly greater than that with the ulnar nerve.

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%.