Abnormal magnetic-resonance scans of the cervical spine in asymptomatic subjects.

Previous investigations with plain radiography, myelography, and computed tomography have shown that degenerative disease of the cervical spine frequently occurs in the absence of clinical symptoms. We studied the magnetic resonance-imaging scans ofsixty-three volunteers who had no history of symptoms indicative of cervical disease. The scans were mixed randomly with thirty-seven scans of patients who had a symptomatic lesion of the cervical spine, and all of the scans were interpreted independently by three neuroradiologists. The scans were interpreted as demonstrating an abnormality in 19 per cent of the asymptomatic subjects: 14 per cent of those who were less than forty years old and 28 per cent of those who were older than forty. Of the subjects who were less than forty, 10 per cent had a herniated nucleus pulposus and 4 per cent had foraminal stenosis. Of the subjects who were older than forty, 5 per cent had a herniated nucleus pulposus; 3 per cent, bulging of the disc; and 20 per cent, foraminal stenosis. Narrowing of a disc space, degeneration of a disc, spurs, or compression of the cord were also recorded. The disc was degenerated or narrowed at one level or more in 25 per cent of the subjects who were less than forty years old and in almost 60 per cent of those who were older than forty. The prevalence of abnormal magnetic-resonance images of the cervical spine as related to age in asymptomatic individuals emphasizes the dangers of predicating operative decisions on diagnostic tests without precisely matching those findings with clinical signs and symptoms. The decision to operate on many patients who have a symptomatic cervical lesion has traditionally depended on the correlation of the mechanical origin of neurogenic symp* No benefits in any form have been received or will be received from a commercial party related directly or indirectly tothe subject ofthis article. No funds were received in support of this study. t Read in part at the Annual Meeting of the Cervical Spine Research Society, New Orleans, Louisiana, December 7, 1989, and at the Annual Meeting of the North American Spine Society, Monterey, California, August 10, 1990 recipient of the 1990 AcroMed Award for Spinal Research. t George Washington University Medical Center, 2150 Pennsylvania Avenue, NW. , Washington. D.C. 20037. § Georgetown University Medical Center, 3800 Reservoir Road, NW. , Washington, D.C. 20007. toms with abnormalities seen on imaging with contrast medium. Until recently, plain radiography, myelography, and computerized tomography, alone or in combination, have been utilized, but now the use of magnetic resonance imaging is increasing. This is an attractive diagnostic alternative because it is non-invasive, involves no radiation, is not known to be associated with any side effects, and provides superior resolution of the anatomy of soft-tissue structures. Excellent sensitivity (a low prevalence of false-negative findings) has been reported for magnetic resonance imaging in the identification of neural compression by mechanical lesions in the cervical and lumbar spine3’4’79”0. However, the important issue of specificity (the prevalence of false-positive findings) needs clarification. Recently, in an investigation of the lumbar spine in asymptomatic subjects, we found a major abnormality on the magnetic resonance images of 22 per cent of the subjects who were less than forty years old and 57 per cent of those who were more than forty’ . To our knowledge, no analogous studies have been done on the cervical spine. The purpose of this report was to document the prevalence of clinically false-positive interpretations of magnetic resonance scans of the cervical spine in an asymptomatic control population. Abnormal interpretations were defined as falsely positive if the subject had no symptoms or signs. Materials and Methods A full magnetic-resonance scan of the cervical spine was made for sixty-three volunteer subjects. They ranged in age from twenty to seventy-three years (average, forty years). The normal subjects were solicited by advertisements and calls for volunteers for a study on an unspecified topic. The respondents were then screened, as was described, and, when possible, we included the spouses of the subjects to balance the distribution of age and sex. There were twenty-five men and thirty women. Subjects were screened prospectively with a standardized questionnaire and with personal interviews, and only those who had no history of cervical pain or trauma, pain in the shoulder, or radicular symptoms referable to the cervical nerve-roots were included in the study. Multiplane magnetic-resonance scans of the cervical spine were made with a 1 . 5-tesla imaging system (Signa; ABNORMAL MAGNETIC-RESONANCE SCANS OF THE CERVICAL SPINE 1 179 VOL. 72-A, NO. 8, SEPTEMBER 1990 TABLE I DIAGNOSIS, AS DETERMINED BY MAGNETIC RESONANCE IMAGING, CLASSIFIED BY AGE IN SIXTY-THREE ASYMPTOMATIC SUBJECTS* <40 Yrs. Old (N = 40) >40 Yrs. Old (N = 23) Total (N = 63) Herniated disc 4 (10%) 1 (5%) 5 (8%) Bulging disc 0 1 (3%) 1 (2%) Forarninal stenosis 1 (4%) 5 (20%) 6 (9%) 8 The abnormality was graded as major for at least one disc level. General Electric, Milwaukee, Wisconsin) and a circular surface coil. First, a sagittal localizing series was performed with a repetition time of 400 milliseconds, an echo time of twenty milliseconds, a slice thickness of five millimeters and a one-millimeter interslice gap, a twenty-four-centimeter field ofview, a 256-by-l28 matrix, and one excitation (scan time, fifty-six seconds). Next, Ti-weighted sagittal images were made with a repetition time of 600 milliseconds, an echo time of thirty milliseconds, a slice thickness of three millimeters and a one-millimeter interslice gap, a twenty-four-centimeter field of view, a 256-by-i92 matrix, and four excitations (scan time, seven minutes and fortyfour seconds). Gradient echo imaging was then used to generate T2* weighted images (not so-called pure T2weighted images, but close to it, using gradient echo rather than spin echo technique) with a repetition time of fifty milliseconds, an echo time of thirteen milliseconds, a flip angle of 6 degrees, a slice thickness of five millimeters and no gap, a twenty-four-centimeter field of view, a matrix of 256 by 128, and eight excitations (scan time, four minutes and seventeen seconds). Axial T2* weighted images were obtained with a repetition time of thirty-five milliseconds, an echo time of fifteen milliseconds, a flip angle of 5 degrees, a slice thickness of two millimeters and no gap, a twenty-centimeter field of view, a matrix of 256 by 128, and two excitations (scan time, nine minutes and thirty-four seconds; additional reconstruction time, four minutes). The sixty-three studies of the asymptomatic volunteer subjects were mixed randomly with thirty-seven scans, made with the same protocol and the same scanner, of patients who had an unequivocal abnormality (either a herniated nucleus pulposus or foraminal stenosis) and who had well defined clinical symptoms or signs that were associated with the abnormality. The 100 scans were presented separately, in a randomized sequence, to three independent neuroradiologists who had no knowledge of the identity of the subject or patient. Each neuroradiologist graded each disc level (from the second cervical level to the first thoracic level) for the presence and severity of spurs, narrowing of the disc space, degeneration of the disc, herniated nucleus pulposus, bulging of the disc, foraminal stenosis, and impingement or compression of the cord. A forced-choice grading sheet was used, with the severity of each abnormal finding being rated as mild, moderate-no (not important), moderate-yes (important), or severe. Due to limited space on the film, axial images of the disc space between the seventh cervical and the first thoracic vertebrae were not evaluated in twenty patients. Since precise definitions of some lesions of cervical discs vary among radiologists, there was a spectrum of interpretations from the three independent neuroradiologists, all of whom were experienced in magnetic resonance imaging of the cervical spine. Precise definitions were not agreed on before the grading, but general guidelines were established. Disc-space narrowing was considered to be a loss of height relative to the cephalad disc space. It was graded as mild if less than 25 per cent of the height had been lost, moderate-no if the loss was 25 to 50 per cent, moderate-yes if it was 50 to 75 per cent, and severe if it was 75 per cent or more. Degeneration of the disc was usually seen in conjunction with loss of height, and it was characterized by a decreased signal in the disc on the T2* weighted images. Herniated nucleus pulposus was considered to be an extrusion, mainly focal, beyond the osseous confines of the vertebral body, of tissue in which the signal was of intermediate intensity (on the Ti-weighted image) and high in-