Dynamic physiologic changes in lumbar CSF volume quantitatively measured by three-dimensional fast spin-echo MRI

STUDY DESIGN

Lumbar MRI of normal adults. Image analysis to measure lumbar CSF volumes at rest and during physiologic maneuvers.

OBJECTIVES

1) Validate an MRI technique to measure CSF volumes, 2) use this technique to measure the resting volume of lumbar CSF, 3) measure changes in CSF volume with physiologic maneuvers, and 4) demonstrate the anatomic basis for these volume changes.

SUMMARY OF BACKGROUND DATA

Studies using radiograph and radionuclide myelography in dogs and humans in the 1960s-1980s qualitatively showed decreases in spinal CSF volume with physiologic maneuvers. Theories were proposed to explain these changes, but they could not be confirmed because only the contrast-laden CSF was visualized using these techniques.

METHODS

Four adult volunteers had lumbar MRI using a fat-saturated T2-weighted three-dimensional fast spin-echo sequence. Quantitative analysis of images was used to measure lumbar CSF volume; the technique was validated using a water phantom. Lumbar CSF volume was measured 1) at rest, 2) with hyperventilation, 3) with abdominal compression, and 4) with both hyperventilation and abdominal compression.

RESULTS

Resting lumbar CSF volume ranged from 28 to 42 mL. Reversible changes in lumbar CSF volume resulting from physiologic maneuvers are visualized by MR myelography and measured. The volume change (10% reduction in volume with hyperventilation, 28% with compression, and 41% with combined hyperventilation and abdominal compression) is directly visualized to be caused by engorgement of the epidural venous plexus, compressing the thecal sac.

CONCLUSIONS

MRI provides a noninvasive means to measure spinal CSF volume and demonstrates the anatomic basis of physiologic volume changes. This has important implications for spinal anesthesia.

Periventricular leukomalacia: relationship between lateral ventricular volume on brain MR images and severity of cognitive and motor impairment

PURPOSE

To evaluate the utility of lateral ventricular volume measurements in predicting motor and cognitive impairment severity in children with periventricular leukomalacia (PVL), with or without seizures.

MATERIALS AND METHODS

The charts of children with spastic cerebral palsy and PVL documented on brain magnetic resonance (MR) images were reviewed. Affected children were grouped by motor and cognitive impairment severity and seizure disorder. An age-matched control group was established. Lateral ventricular volumes were measured on two-dimensional T2-weighted spin-echo MR images. Analysis of variance was used to identify significant differences in mean lateral ventricular volume between groups. Paired analyses of differences were performed with the Bonferroni t method.

RESULTS

Thirty-six children (24 boys, 12 girls) with spastic cerebral palsy and PVL and 21 age-matched control subjects (14 boys, seven girls) were identified. Mean lateral ventricular volumes of the moderate and marked motor deficit groups were significantly larger than those of the control and mild motor deficit groups (F = 29.24; alpha = .01). Mean lateral ventricular volumes of all cognitive impairment groups were significantly larger than those of the control and no-cognitive-impairment groups (F = 21.101 alpha = .01). There was no difference in mean lateral ventricular volume between children with PVL with or without seizures.

CONCLUSION

Lateral ventricular volume measurements can be used as quantitative markers of clinical impairment severity and as clinical outcome predictors before formal testing is possible.

Common bile duct in children: sonographic dimensions

PURPOSE

To determine the normal caliber and rate of growth of the extrahepatic biliary ducts in the pediatric population.

MATERIALS AND METHODS

The diameter of the common bile duct was measured with sonography in 173 children aged 1 day to 13 years (mean, 6.0 years; median, 5.0 years) who were examined for reasons other than hepatic or biliary tract disease. Results were subjected to regression analysis and compared with similar measurements of the extrahepatic portal vein and hepatic artery. The size of the gallbladder was subjectively estimated as distended, moderately full, and contracted. Differences in the diameter of the common bile duct in these three groups were evaluated with the Mann-Whitney U test.

RESULTS

The average diameter of the common bile duct in this population was 1.27 mm +/- 0.67 (< 3.3 mm in all patients and < 1.2 mm in children aged 3 months or less). The slope of the curve describing the growth of the common bile duct was relatively flat, similar to that of the hepatic artery and half that of the portal vein. There was a significant difference in the diameter of the common bile duct between patients with distended gallbladders and those with contracted gallbladder (P = .02).

CONCLUSION

The pediatric common bile duct is significantly smaller than adult norms; it is a distensible structure responsive to fluctuations in prandial bile flow.

Three-dimensional CT imaging in postsurgical "failed back" syndrome

One hundred consecutive patients with postsurgical "failed back" syndrome (PSFBS) without fusion and 100 patients with PSFBS with fusion were evaluated with direct CT, two-dimensional (2D) multiplanar, and three-dimensional (3D) imaging. In the patients with and without fusion, 3D images were found to best display the following: the surgical procedure and its extent, lateral neural foraminal narrowing, and fractures of the posterior elements. The 3D images enabled optimal demonstration of fusion: solidity, pseudarthrosis, incorporation of transverse processes and facet joints, and transitional syndrome. In the patients without fusion, 3D images provided improved appraisal of surgical results in 31%; it showed additional fracture(s) in 9%, better displayed lateral neural foraminal narrowing in 42%, and showed additional posterior element fractures in 11% as compared to axial and 2D multiplanar reconstructed (MPR) scans. Three-dimensional imaging uncovered incomplete fusion in 17%, transitional syndrome in 13%, and pseudarthrosis in 6%. Thus, the 3D imaging provided additional information over the direct axial and MPR images (2D images) in 56 of 100 patients without fusion and 76 of 100 patients with fusion. At our institution, this imaging modality is now routinely performed in this patient population.

3-D CT for cranial facial and laryngeal surgery

Three-dimensional imaging is a new digital technology which interpolates two-dimensional computer tomography information to render a "life-like" anatomic display of the diagnostic information. We have found that this new methodology significantly improves the assessment and therapy of patients undergoing surgical procedures of the head and neck. The technique has been used in cranial-facial and laryngeal pathology, and in preoperative planning of tumor resection, particularly skull-base neoplasms. The use of three-dimensional computer tomography improves the display of the location and volume of pathology and affords accurate therapeutic and surgical planning. The choice and extent of surgery is better defined, and precise bone removal can be performed. In reconstructive surgery, an accurate prefabricated model of the bony defect can be made to aid reconstruction. Representative cases demonstrating the use of three-dimensional computer tomography in head and neck surgery, and its benefits in saving operative time and improving the postoperative result, will be discussed.