Juxtafacet cysts of the lumbar spine: a positional MRI study.

BACKGROUND/AIMS: Juxtafacet cysts (JFC) are related to facet joint degeneration. Supine MRI is routinely used to evaluate JFC. However, some JFC are missed and found only intraoperatively. The present study addresses positional MRI features and factors leading to variation in the size of JFC. METHODS: Fifty patients in whom positional MRI had been performed were investigated retrospectively and 67 distinct intraspinal or intraneuroforaminal were JFC found. Signal intensity, size of the JFC, the presence and variance of a vertebral slip and the angular movement of affected segments were assessed in supine, neutral sitting, flexion (sitting) and extension (standing). The overall movement of the spine and the lordosis angle in different positions were measured. RESULTS: JFC varied in size in segments with unstable slip and increased angular movement (variation of the angle in the affected segment in function: 13.3 degrees compared to 8.7 degrees). JFC with bright signals tended to vary in size compared to JFC with intermediate or low signal intensity (all: p < 0.001). Joint effusion and displacement of effusion lead to formation and variations in the size of JFC. JFC were most prominent in extension: 6.7 mm, less prominent in supine: 5.5 mm and in neutral sitting position: 4.6 mm (all p < 0.05). The detection rate for JFC was 97% for extension, 89% for supine and 78% for neutral sitting. CONCLUSIONS: The detection rate of JFC improves with increasing lordosis of the spine and under weight-bearing conditions, particularly when standing. Unstable slipping or increased angular movement affects the size of JFC.

Spondylolysis and spondylolisthesis: prevalence of different forms of instability and clinical implications.

STUDY DESIGN: Imaging study with an evaluation of incidences and clinical correlation. OBJECTIVE: To evaluate the incidence of 3 different types of instabilities in patients with spondylolysis or isthmic spondylolisthesis. Clinical findings are correlated with imaging findings, and the imaging findings are analyzed with regard to their clinical implications. SUMMARY OF BACKGROUND DATA: Spondylolysis and isthmic spondylolisthesis are common disorders. An unstable slip is the most well-known form of instability, but other forms also exist. However, the incidence of these instabilities and their clinical implications are yet unclear. METHODS: A total of 140 patients with 141 levels of spondylolysis identified by MRI (magnetic resonance imaging) were included in this study. Using positional MRI, the instability of the slip, an increased angular movement, and movement in the spondylolytic cleft were assessed. On the basis of clinical findings, the patients were classified as presenting with either radicular or nonradicular symptoms. The incidence of the instabilities was recorded and correlated with the incidence of radicular symptoms. RESULTS: Fifteen patients had an unstable slip (anterior instability); 35, an increased angular movement (angular instability); and 34 patients, a movement in the spondylolytic cleft (posterior instability). All forms of instability could be found together. No instability at all was found in 76 patients. Radicular symptoms were found significantly more often in patients with one or more of the described instabilities compared with patients without instability. CONCLUSION: All 3 described forms of instability are common in spondylolysis or isthmic spondylolisthesis and associated with radicular pain. This finding stresses the value of positional MRI in the evaluation of patients with spondylolysis and isthmic spondylolisthesis, especially if radicular symptoms are present.

Postural effect on the size of the cisterna chyli.

BACKGROUND: The aim was to investigate the effect of patient position on the size of the cisterna chyli using positional MRI. The cisterna chyli is usually the only large lymphatic vessel that can be found on cross-sectional imaging. Not much is known about its postural behavior. However, animal studies suggest that the cisterna chyli varies in size according to physical activity. METHODS AND RESULTS: Retrospectively, 998 MRI scans of patients referred for positional MRI were reviewed. Ten patients had acquired axial scans in at least two positions at the level T12/L1 or/and L1/2 and were included in the study. The area representing the cisterna chyli was assessed on axial images and its size was compared in different positions. The size of the cisterna chyli determined as the cross-sectional area was 14.7 mm² ± 17.3 mm² in the supine position, 43.8 mm² ± 3.1 mm² in the sitting position, and 62.9 mm² ± 42.5 mm² in the standing position. Using the t-test, a statistically significant difference was found in the size of the cistern chyli between supine and standing positions and between supine and sitting positions. CONCLUSIONS: The size of the cisterna chyli shows postural variations. This finding is discussed in regards to possible implications of interventional procedures in the thoracic duct. Physicians reading MR images acquired in positions other than supine should be aware of these physiological changes.