The relation among spinal geometry on MRI, paraspinal electromyographic abnormalities, and age in persons referred for electrodiagnostic testing of low back symptoms.
Spine (Phila Pa 1976) 2002;
27:1918-25; discussion 1924-5. [PMID:
12221358 DOI:
10.1097/00007632-200209010-00019]
[Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
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.
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