Describing paraspinal EMG findings: inadequacy of the single 0-4+ score

Polysegmental innervation of the medial paraspinal lumbar muscles

A retrospective analysis was performed in a nine month period of the electrophysiological data, imaging and clinical findings of patients with monoradicular disc herniation compressing either the L5 or the S1 nerve root. The primary purpose of the analysis was to determine the distribution of pathological spontaneous activity in the medial paraspinal muscles on electromyographic examination in monoradicular L5 and S1 nerve root compression syndromes. Anatomically, the medial paraspinal muscles receive their innervation from a single root while the iliocostalis muscles and the longissimus muscle are thought to be innervated by multiple nerve roots. In the analysis, in single nerve root lesion of the L5 or S1 nerve root, electromyography of the medial paraspinal muscles revealed pathological spontaneous activity one to three vertebrae cranial to the disc herniation with extension to the opposite side of the lesion. In conclusion, the medial paraspinal muscles might be thought to be innervated by one single nerve root on anatomical studies, electrophysiologically the extension of axonal lesion signs of one single lumbar nerve root is much broader. The widespread distribution of the L5 and S1 nerve root must be taken into consideration on electromyographic examination of the medial paraspinal muscles.

Needle EMG has a lower false positive rate than MRI in asymptomatic older adults being evaluated for lumbar spinal stenosis

OBJECTIVE

False positive imaging tests--disk herniation or spinal stenosis--occur in a significant number of asymptomatic persons, increasing with age. A similar or greater prevalence probably occurs in people who present to physicians with mechanical back pain, potentially causing therapeutic misadventure. Electrodiagnostic testing may be normal in persons with asymptomatic pathology, but has not been directly tested.

METHODS

As part of a larger study of older persons with lumbar stenosis, 35 asymptomatic adults were evaluated by an extensive questionnaire, codified history and physical examination, masked electrodiagnostic testing, and masked lumbar magnetic resonance imaging, with repeated procedure at 18 months. Thirty-two subjects remained after removal of three with neuromuscular disease.

RESULTS

The radiologist characterized 18 (56%) asymptomatic subjects as having spinal stenosis. There was no relationship between electrodiagnostician diagnosis and radiologist diagnoses. Among the 13 whom the electrodiagnostician identified as abnormal, 2 had technical data within normal limits and the only abnormality in 5 was >2/10 polyphasic motor units (considered a 'soft' finding by many). One muscle in 1 subject had abnormal spontaneous activity, and 3 persons scored >4 on paraspinal mapping. Electrodiagnostic findings were normal in the 5 (16%) who had disk herniations. None of the 22 re-examined acquired symptoms over 18 months and follow-up electrodiagnosis was essentially normal (one muscle in 1 subject had 3/10 polyphasic motor units).

CONCLUSIONS

MRI changes, motor unit changes on EMG needle examination, and low paraspinal mapping scores are not uncommon in asymptomatic older adults with spinal stenosis or disk herniation and may lead to false positive tests. The stricter criterion of abnormal spontaneous activity on needle examination and paraspinal mapping scores greater than 6 offered in this paper lowers the risk of false positive EMG testing.

SIGNIFICANCE

EMG is less likely to be abnormal (false positive) in asymptomatic adults than MRI.

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.

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.

Paraspinal denervation and the spinal degenerative cascade

BACKGROUND CONTEXT

The aging of the spine has been reported to follow a degenerative cascade described by Kirkaldy-Willis. This cascade does not take into account the paraspinal muscles. Substantial recent knowledge of the anatomy, physiology and pathophysiology of the paraspinal muscles suggests that they should play a role in the degenerative cascade. Pain relates to paraspinal denervation in a number of disorders. Using new needle electromyographic technique, MiniPM, we may be able to quantify the extent of paraspinal muscle denervation.

PURPOSE

To explore the potential interactions between paraspinal muscle denervation and the degenerative cascade.

STUDY DESIGN

Literature review, reanalysis of a blinded electromyographic study and case reports.

PATIENT SAMPLE

A previously reported group of 35 asymptomatic paid volunteers, ages 18 to 58 years. Two elderly volunteers with moderate to severe spinal stenosis on magnetic resonance imaging (MRI), one significantly disabled, one asymptomatic.

OUTCOME MEASURES

Blinded electromyographic testing, including MiniPM, a codified, quantified needle electromyography technique for the paraspinal muscles. In the two case reports, magnetic resonance imaging and 15-minute timed ambulation.

METHODS

The 35 volunteers were tested by a blinded electromyographer using the MiniPM technique. The two older subjects underwent MRI, MiniPM and extensive electrodiagnostic evaluations, functional testing, complete history and physical examination.

RESULTS

The patient with symptomatic stenosis had a MiniPM score of 6 on each side, and the asymptomatic volunteer had a score of 0. In the asymptomatic subject group, reproducible evidence for denervation was found in 20 subjects (57%), sparsely distributed, but more caudal than cranial (p<.0001). Based on conservative estimates of nerve regeneration rates, the population averaged a detected axonotemesis denervating event approximately once every 120 days.

CONCLUSIONS

Paraspinal denervation may be proven to be a better marker than MRI findings for symptomatic spinal stenosis. Subtle paraspinal muscle denervation occurs frequently in asymptomatic persons. Whether a cause or an effect, paraspinal denervation might lead to hypermobility and thus progression along the degenerative cascade.