Bone marrow fat and bone mineral density on proton MR spectroscopy and dual-energy X-ray absorptiometry: their ratio as a new indicator of bone weakening.

OBJECTIVE: Bone weakening can be affected by agents other than bone mineral density (BMD). Increased bone marrow fat may have a direct link to bone loss. This pilot study analyzes the relationship between bone marrow fat and BMD in subjects with normal and structurally weakened vertebrae. SUBJECTS AND METHODS: Twenty-six subjects underwent both dual-energy X-ray absorptiometry and proton MR spectroscopy of 71 lumbar vertebrae. Fifteen subjects had normal-appearing vertebrae on MRI, and 11 had signs of bone weakening. RESULTS: We found that high bone marrow fat did not consistently equate with low BMD. Bone marrow fat can indicate bone weakening nearly as well as BMD, but neither parameter alone is suitable to be used independently as an indicator. The bone marrow fat/BMD ratio showed significant diagnostic power to detect bone weakening, even in this relatively small subject sample. CONCLUSION: An inverse relationship between bone marrow fat and BMD could not be confirmed. Bone marrow fat can be used to diagnose reduced bone strength nearly as well as BMD. The bone marrow fat/BMD ratio is a significant diagnostic indicator of bone weakening.

The value of magnetic resonance imaging of the lumbar spine to predict low-back pain in asymptomatic subjects : a seven-year follow-up study.

BACKGROUND: In 1989, a group of sixty-seven asymptomatic individuals with no history of back pain underwent magnetic resonance imaging of the lumbar spine. Twenty-one subjects (31%) had an identifiable abnormality of a disc or of the spinal canal. In the current study, we investigated whether the findings on the scans of the lumbar spine that had been made in 1989 predicted the development of low-back pain in these asymptomatic subjects. METHODS: A questionnaire concerning the development and duration of low-back pain over a seven-year period was sent to the sixty-seven asymptomatic individuals from the 1989 study. A total of fifty subjects completed and returned the questionnaire. A repeat magnetic resonance scan was made for thirty-one of these subjects. Two neuroradiologists and one orthopaedic spine surgeon interpreted the original and repeat scans in a blinded fashion, independent of clinical information. At each disc level, any radiographic abnormality, including bulging or degeneration of the disc, was identified. Radiographic progression was defined as increasing severity of an abnormality at a specific disc level or the involvement of additional levels. RESULTS: Of the fifty subjects who returned the questionnaire, twenty-nine (58%) had no back pain. Low-back pain developed in twenty-one subjects during the seven-year study period. The 1989 scans of these subjects demonstrated normal findings in twelve, a herniated disc in five, stenosis in three, and moderate disc degeneration in one. Eight individuals had radiating leg pain; four of them had had normal findings on the original scans, two had had spinal stenosis, one had had a disc protrusion, and one had had a disc extrusion. In general, repeat magnetic resonance imaging scans revealed a greater frequency of disc herniation, bulging, degeneration, and spinal stenosis than did the original scans. CONCLUSIONS: The findings on magnetic resonance scans were not predictive of the development or duration of low-back pain. Individuals with the longest duration of low-back pain did not have the greatest degree of anatomical abnormality on the original, 1989 scans. Clinical correlation is essential to determine the importance of abnormalities on magnetic resonance images.

Potential value of vertebral proton MR spectroscopy in determining bone weakness.

BACKGROUND AND PURPOSE: Increased fat content in vertebrae may indicate bone weakness. Vertebral proton MR spectroscopy ((1)H MRS) quantitatively measures vertebral fat relative to water. Thus, (1)H MRS measurements of percent fat fraction (%FF) and spectral line width (LW) of vertebral bone marrow may differ between subjects with and those without MR imaging evidence of weakened bone. METHODS: We measured %FF and LW in 22 subjects with (15 men and 7 women, aged 26 to 80 years) and 72 control subjects without (33 male and 39 female subjects, aged 15 to 87 years) MR findings of weakened bone, including prominent Schmorl's nodes, endplate depression, vertebral wedging, and vertebral compression fractures. In those with bone weakness, (1)H MRS data were sampled from an intact vertebra, usually L2. Data were analyzed for differences by age and sex. We compared the mean %FF and LW in subjects with and in those without bone weakness by use of Student's t test. RESULTS: The %FF increased linearly with age in the control subjects, ranging from 20.5% in the second and third decades of life to 49.4% in eighth or ninth decades of life. Across all age groups, male control subjects had a higher aggregate %FF than did female control subjects. Male control subjects tended to have a greater LW than did female control subjects, but differences between the sexes within or across age groups were not significant. Contrary to expectations, LW was greatest in the oldest control subjects and lowest among younger control subjects, but there were insufficient data points to make definitive conclusions. Overall, %FF was a relative 45% higher in subjects with weakened bone compared with control subjects (48.8 vs 33.6 [P <.001]). The subjects with evidence of vertebral bone weakness also had a higher overall mean LW (37 vs 29 Hz [P <.002]), but this finding is of uncertain importance. CONCLUSION: The %FF was significantly higher within the L2 vertebral body in 22 subjects with weakened bone compared with the control group, suggesting that it could serve as a measure of bone quality. The LW measurements did not yield meaningful conclusions.

The fetus at term: in utero volume-selected proton MR spectroscopy with a breath-hold technique--a feasibility study.

In three healthy gravidas at 38 and 39 weeks gestation, fetal MR spectroscopy was performed with a breath-hold technique by using the following pulse sequences: single voxel point-resolved spectroscopy, or PRESS, for liver and heart studies and stimulated-echo acquisition mode, or STEAM, for brain studies. Signal peaks of lipid from heart and liver were detected, as were the signal peaks of choline, creatine, and N-acetylaspartate from fetal brain. Findings demonstrated the feasibility of performing proton MR spectroscopy to assess mobile fetal structures.

Normal lumbar vertebrae: anatomic, age, and sex variance in subjects at proton MR spectroscopy--initial experience.

Fifty-seven subjects underwent proton magnetic resonance (MR) spectroscopy of the second lumbar vertebra to evaluate single-voxel and multivoxel techniques. Measurements included lipid-to-water ratios, lipid fractions, and line width. These data provide information about vertebral fat content. There was an age-dependent linear increase in fat content and sex dependence. A higher fat concentration was found in men. The observed spectra provide a basis for future study to determine clinical utility of vertebral proton MR spectroscopy.

A vascular sarcoid mass mimicking a convexity meningioma.

We report a 48-year-old woman with a left posterior temporal extra-axial mass that had the imaging characteristics of a meningioma on preoperative CT, MRI and angiography. However, a biopsy diagnosis of sarcoidosis was made. This case illustrates that dural-based sarcoid masses can be very vascular and radiographically indistinguishable from meningiomas. Characteristic imaging features of extra- and intra-axial sarcoid lesions are discussed.

2D CSI proton MR spectroscopy of human spinal vertebra: feasibility studies.

This report focuses on proton magnetic resonance spectroscopy (1H MRS) of spine vertebra acquired with two-dimensional chemical shift imaging (2D CSI), utilizing the stimulated echo acquisition mode (STEAM) sequence. Both validity and reproducibility studies were performed. To validate the 2D CSI method, its spectra were compared with those obtained with the single-voxel (SV) method. Five normal volunteers were scanned. The reproducibility of 2D CSI was examined by performing spectroscopy on two different occasions, on three normal volunteers. Data show that the STEAM 2D CSI technique results in MRI spectra comparable to those obtained with the STEAM SV method. 2D CSI offers significant time savings and convenient multi-voxel spectral analysis at a substantially higher signal-to-noise ratio. The 2D CSI method was then applied to a patient with a small vertebral hemangioma. The results demonstrated that the voxels containing the hemangioma exhibit different spectra than the neighboring voxels of the same vertebra. Additionally, a case of vertebral osteoporosis was investigated. Results showed a significant increase in the lipid-to-water ratio (LWR). It is suggested that 2D CSI may be powerful in identifying physiological as well as pathological changes of the bone marrow. Furthermore, covering a more extensive area of the vertebral body will maximize the chances of depicting a small focus of pathologic tissue. A more detailed bone marrow pattern was noticed in on one subject whose spectra show more lipid peaks.

Taste memory induces brain activation as revealed by functional MRI.

PURPOSE: Our goal was to use functional MRI (fMRI) to measure brain activation in response to imagination of tastes in humans. METHOD: fMR brain scans were obtained in 31 subjects (12 men, 19 women) using multislice FLASH MRI and echo planar imaging (EPI) in response to imagination of tastes of salt and sweet in coronal sections selected from anterior to posterior temporal brain regions. Activation images were derived using correlation analysis, and ratios of areas of brain activated to total brain areas were calculated. Total activated pixel counts were used to quantitate regional brain activation. RESULTS: Activation was present in each section in all subjects after imagination of each tastant. Activation was similar in response to imagination of either salt or sweet and was quantitatively similar to that previously reported in response to imagination of odors of banana and peppermint. Activation was similar in both men and women as opposed to previous results of odor memory in which activation in men was greater than in women. However, subjective responses of intensity of imagined tastes were significantly greater than those previously obtained for odor memory and were consistently, albeit not significantly, greater in women than in men, similar to results previously reported for odor memory. Brain regions activated in response to taste imagination were consistent with regions previously described as involved with actual taste perception in both humans and animals. Regional brain localization for salt and sweet memories could not be differentiated. CONCLUSION: These studies indicate that (a) tastes can be imagined, (b) brain regions activated for taste imagination are consistent with regions previously described for actual taste perception, and (c) similar to odor memory for banana and menthone, regional brain localization for salt or sweet taste memories could not be differentiated.

Odor memory induces brain activation as measured by functional MRI.

PURPOSE: Our goal was to use functional MRI (fMRI) to measure brain activation in response to imagination of odors in humans. METHOD: fMR brain scans were obtained in 21 normal subjects (9 men, 12 women) using multislice FLASH MRI in response to imagination of odors of banana and peppermint and to the actual smells of the corresponding odors of amyl acetate and menthone, respectively, in three coronal sections selected from anterior to posterior temporal brain regions. Similar studies were obtained in two patients with hyposmia using FLASH MRI and in one patient with hyposmia using echo planar imaging, both before and after theophylline treatment, which returned smell function to or toward normal in each patient. Activation images were derived using correlation analysis, and ratios of areas of brain activated to total brain areas were calculated. RESULTS: Activation was present in each section in all normal subjects and in each patient after imagination of each vapor. In normal subjects, brain activation in response to imagination of odors was significantly less than that in response to the actual smell of these odors, and activation following imagination of banana odor was significantly greater in men than in women, as was previously reported for the actual smell of the odor of amyl acetate. However, in relative terms, albeit at an absolute lower brain activation level, the ratio of brain activation by imagination of banana to activation by actual amyl acetate odor was about twice as high in women as in men. Before treatment, in patients with hyposmia, brain activation in response to odor imagination was greater than after presentation of the actual odor itself. After treatment, in patients with hyposmia in whom smell acuity returned to or toward normal, brain activation in response to odor imagination was not significantly different quantitatively from that before treatment; however, brain activation in response to the actual odor was significantly greater than that in response to imagination of the corresponding odor. Brain regions activated by both odor imagination and actual corresponding odor were similar and consistent with regions previously described as responding to odors. CONCLUSION: These studies indicate that (a) odors can be imagined and similar brain regions are activated by both imagined and corresponding actual odors; (b) imagination of odors elicits quantitatively less brain activation than do actual smells of corresponding odors in normal subjects; (c) absolute brain activation in men by odor imagination is greater than in women for some odors, but on a relative basis, the ratio for odor imagination to actual smell in women is twice that in men; (d) odor imagination, once the odor has been experienced, is present, recallable, and capable of inducing a relatively constant degree of brain activation even in the absence of the ability to recognize an actual corresponding odor.

Increased brain activation in response to odors in patients with hyposmia after theophylline treatment demonstrated by fMRI.

PURPOSE: Our goal was to demonstrate that medical therapy in patients with smell loss (hyposmia) that restored olfactory function toward or to normal could be verified and quantitated by functional MRI (fMRI) of brain and that visual representation of these changes could be used to identify these patients. METHOD: Multislice FLASH MR or echo planar MR brain scans were obtained in four patients with hyposmia in response to three olfactory stimuli both before and after treatment with theophylline. Activation images were derived using correlation analysis, and ratios of brain area activated to total brain area were obtained. RESULTS: Prior to treatment, all patients stated that they could not smell; these losses were confirmed by standard psychophysical tests. At this time, fMRI brain activation in response to odors was significantly less than that measured in normal volunteers and similar to activation measured previously in other patients with a similar type of hyposmia. After treatment, subjective smell function improved in three patients and no improvement occurred in one; results were confirmed by psychophysical tests. In each patient in whom smell acuity improved, brain activation in response to each odor increased in each section and mean activation increased significantly for each odor. Activation increased in all regions previously associated with olfactory stimulation and was particularly apparent in orbitofrontal cortex, frontal lobe component of cingulate gyri, temporal lobe gyri, and hippocampus. There also was consistent activation in superior, middle, and inferior frontal lobe gyri. There were no changes in brain activation after treatment in the patient in whom smell did not improve. CONCLUSION: These results demonstrate that theophylline is an effective therapeutic agent to correct hyposmia in some patients with smell loss. These changes have been documented by fMRI brain scans using olfactory stimuli. This is the first study in which this type of objective improvement following medical treatment has been demonstrated in patients with hyposmia.

Mapping brain activation to odorants in patients with smell loss by functional MRI.

PURPOSE: Our goal was to use functional MRI (fMRI) to develop an objective, noninvasive technique by which patients with smell loss can be identified, their abnormalities quantitated, their results compared with findings in normal subjects, and visual representation of their CNS pathology obtained. METHOD: Functional MR brain scans were obtained in eight patients with hyposmia in response to three olfactory stimuli (pyridine, menthone, amyl acetate) in three coronal brain sections selected from anterior to posterior temporal brain regions using multislice FLASH MRI. Results were compared with similar studies performed in 17 normal subjects. Activation images were derived using correlation analysis, and ratios of area of brain activated to total brain area were obtained. RESULTS: Brain activation to each stimulus was lower in each section in patients compared with normal subjects and reached statistical significance for mean activation for each odor and in six of the nine individual sections studied. Activation in patients was found in regions previously associated with CNS processing of olfactory stimuli in normal subjects, but activation in patients was much less, particularly in inferior frontal and cingulate gyral regions of frontal cortex and in regions of medial and posterior temporal cortex. CONCLUSION: These results demonstrate quantitative CNS changes in smell function in response to olfactory stimuli in patients with hyposmia, demonstrate a novel, objective method by which these patients can be identified, and provide maps of the CNS changes associated with their smell loss.

Functional MRI of human olfaction.

PURPOSE: Our goal was to use functional MRI (fMRI) to measure brain activation in response to olfactory stimuli. METHOD: fMRI brain scans were obtained in 17 normal subjects (9 men, 8 women) using-multislice FLASH MRI in response to three olfactory stimuli (pyridine, menthone, amyl acetate) in three coronal brain sections selected from anterior to posterior temporal brain regions. Activation images were derived using correlation analysis, and ratios of areas of brain activated to total brain areas were calculated. RESULTS: Activation was present in each section in all subjects. Subjective estimation of vapor intensity followed relative vapor pressure of stimuli presented (pyridine > amyl acetate > menthone) and were similar for both men and women. However, brain activation did not follow subjective responsiveness order but rather pyridine > menthone > amyl acetate, a pattern demonstrated by both men and women. Brain activation in women was consistently lower than in men for all vapors in all brain sections, although regions of activation did not differ. Activation occurred in regions previously recognized as associated with olfactory stimulation, including orbitofrontal and entorhinal cortex; however, extensive regions within frontal cortex including cingulate gyrus were also activated. Brain regions activated to odors considered pleasant or unpleasant did not differ. CONCLUSION: The techniques used in this study demonstrated that brain activation to olfactory stimuli could be measured quantitatively such that differences between groups of subjects (in this case men and women) could be compared. Although localization of brain activation was not the major thrust of this study, activation to olfactory stimuli was found not only in brain regions previously associated with processing of olfactory information but also in several other areas of frontal cortex, in cingulate gyrus, and in several components of the limbic system. This is the first study in which activation in human brain parenchyma of normal humans to olfactory stimuli has been quantitated by fMRI.

Patterns of anterior spinal canal involvement by neoplasms and infections.

PURPOSE: To show that retrovertebral extension of neoplastic and infectious disease proceeds in a predictable manner, with the anatomic superstructure determining the shape of the advancing process. METHODS: We examined 58 patients who had neoplastic (n = 44) and infectious (n = 14) processes that caused canal compromise. In total, 140 levels were examined by means of MR imaging only (48 patients), CT only (1 patient), CT plus MR imaging (3 patients), and MR imaging plus CT myelography (6 patients). RESULTS: At 136 levels, the retrovertebral disease process took the shape of a smoothly marginated, bilobulated mass that was broad-based against the posterior surface of the vertebra. Various degrees of mass effect were observed: symmetric on 108 levels and asymmetric on 28 levels; on 4 levels, expansion of the anterior epidural space was unilobar, reflecting unilateral canal invasion. With advanced stages of canal invasion, this bilobulated pattern was maintained but there was a tendency toward detachment of the midline septum (20 levels). CONCLUSION: The observed patterns are determined by the particular anatomy of the anterior epidural space. The shape of the mass is imposed by the posterior longitudinal ligament and by the attached lateral membranes, with the central tether produced by the attached midline septum. The two compartments expand independently.

Orientation of the lumbar facet joints: association with degenerative disc disease.

The orientation of the lumbar facet joints was studied with magnetic resonance imaging in 140 subjects to determine if there is an association between facet tropism and intervertebral disc disease or between the orientation of the facet joints and degenerative spondylolisthesis. The 140 subjects were divided into four groups: sixty-seven asymptomatic volunteers, forty-six of whom did not have a herniated disc on magnetic resonance scans (Group I) and twenty-one who did (Group II); forty-six symptomatic patients who had a herniated disc confirmed operatively (Group III); and twenty-seven patients who had degenerative spondylolisthesis at the interspace between the fourth and fifth lumbar vertebrae (Group IV). Axial scans were made at each lumbar level and digitized, and the facet joint angle was measured by two independent observers with use of image analysis software in a personal computer. The technique of measurement of the facet angles on magnetic resonance scans was validated with a subset of subjects who also had computed tomography scans made. Similar values were obtained with the two methods (r = 0.92; p = 0.00001). For the forty-six asymptomatic volunteers who did not have a herniated disc on the magnetic resonance scans (Group I), the median facet tropism was 5 to 6 degrees and was more than 10 degrees in 24 per cent (eleven) of the subjects. There was no association between increased facet tropism and disc degeneration. At the level of the fourth and fifth lumbar vertebrae, the median facet tropism was 10.3 degrees in the symptomatic patients who had a herniated disc at the same level and 5.4 degrees in the asymptomatic volunteers (Group I) (p = 0.05). The mean orientation of the lumbar facet angles relative to the coronal plane was more sagittal at all levels in the patients who had degenerative spondylolisthesis. The greatest difference was at the level of the fourth and fifth lumbar vertebrae (p = 0.000001). The mean facet angle was 41 degrees (95 per cent confidence interval, 37.6 to 44.6 degrees) in the asymptomatic volunteers and 60 degrees (95 per cent confidence interval, 52.7 to 67.1 degrees) in the patients who had degenerative spondylolisthesis. Furthermore, both the left and the right facet joints were more sagittally oriented in the patients who had degenerative spondylolisthesis. An individual in who both facet-joint angles at the level of the fourth and fifth lumbar vertebrae were more than 45 degrees relative to the coronal plane was twenty-five times more likely to have degenerative spondylolisthesis (95 per cent confidence interval, seven to ninety-eight times). The increase in facet angles at levels other than that of the spondylolisthesis suggests that increased facet angles represent variations in anatomy rather than a secondary result of spondylolisthesis.

Flow-sensitive magnetic resonance imaging in the evaluation of cerebrospinal fluid leaks.

Cerebrospinal fluid (CSF) leaks involving the skull base are associated with considerable morbidity and mortality, and often present a diagnostic challenge. Current diagnostic methods are invasive and cumbersome and involve substantial radiation exposure of the patient. The authors identified seven patients with clinically suspected CSF leaks and evaluated them with a flow-sensitive magnetic resonance imaging (MRI) sequence in addition to more conventional studies. In cases with active CSF leakage, flow characteristics were documented with slow-flow and diffusion-weighted MRI. Unlike current approaches, MRI offers the advantages of rapidity, non-invasiveness, and absence of ionizing radiation. Preliminary results suggest that flow-sensitive MRI may have a role in the evaluation of CSF leaks involving the skull base and temporal bone.

Atypical cerebral aneurysm in a young child.

Autopsy findings are described of an atypical aneurysm of a large cerebral artery in a young child. The lesion is believed to have been an infective (mycotic) aneurysm. Antibiotics were administered at the time of the first leakage which had been thought to be due to a sinus infection. The sac wall exhibited a subacute pleomorphic inflammatory cell response indicative of a resolving infective aneurysm, and appearance that is likely to be encountered more often in the future.

A clinical and neuropathologic study of silk suture as an embolic agent for brain arteriovenous malformations.

PURPOSE: To evaluate the safety and efficacy of silk suture as an agent for preoperative embolization of cerebral arteriovenous malformations. METHODS: Clinical and histopathologic results were analyzed in six patients who underwent embolization of cerebral arteriovenous malformations using silk suture in combination with other agents. RESULTS: Three of the patients treated with silk hemorrhaged after embolization, and two of these patients died. Neuropathologic analysis of four patients showed acute perivascular inflammation, sometimes quite severe. CONCLUSIONS: The inflammatory response to silk may explain its effectiveness in producing vascular occlusion. However, a fulminate vasculitis theoretically can predispose to delayed hemorrhage. Other problems with silk include the pressure required to inject the agent and the inability to determine the final site of deposition of the silk. Although other embolic agents may share some of these potential difficulties, we feel that the disadvantages outweigh the advantages of silk as an embolic agent.

Sacral meningeal cysts: evaluation with MR imaging.

It is often difficult for the radiologist to determine if a given sacral meningeal cyst is causing symptoms. Radiographic criteria for identifying cysts likely to be symptomatic are needed. Using conventional magnetic resonance (MR) imaging along with a specifically designed flow-sensitive sequence, the authors characterized 24 cysts (19 patients) with respect to diameter and communication with the subarachnoid space. They found no significant difference in size between symptomatic and asymptomatic cysts (P > .05) but did observe a clear-cut disparity in the context of communication: Five of five asymptomatic cysts were shown to communicate on MR flow studies, while seven of seven symptomatic cysts were not shown to communicate. The authors propose that flow-sensitive MR imaging is useful in differentiating communicating from noncommunicating sacral meningeal cysts and that this information may be of value in classifying these lesions as more or less likely to be symptomatic.

Isolation of the fourth ventricle causing transtentorial herniation: neurosonographic findings in premature infants.

OBJECTIVE: Significant posthemorrhagic enlargement of the fourth ventricle occurs only in a small minority of patients. Although entrapment or isolation of any ventricle can occur, the fourth ventricle is the most common site. This study was undertaken to better understand enlargement of the fourth ventricle after intraventricular hemorrhage and the neurosonographic features of isolation and transtentorial herniation. MATERIALS AND METHODS: The sonographic records of 1535 premature neonates were reviewed for evidence of intracranial hemorrhage and ventriculomegaly. Cranial sonography was performed within the first 3 days of life in all neonates born in our hospital and within the first week of admission for transferred neonates. Follow-up sonograms were obtained at weekly intervals until discharge from the nursery. Intracranial hemorrhages were classified as severe when the hemorrhage was associated with hydrocephalus, intraparenchymal hemorrhage, or both. RESULTS: Intracranial hemorrhage occurred in 761 (50%) of 1535 patients, with severe hemorrhages in 229. Ten had massive enlargement of the fourth ventricle with isolation in six of the 10 after shunt placement. Isolation of the fourth ventricle causing transtentorial herniation occurred in three. Of the patients with isolation of the fourth ventricle, two had associated infection and ventriculitis caused by Klebsiella oxytoca and one had Candida ventriculoencephalitis. CONCLUSION: The early recognition of the neurosonographic features of an enlarged fourth ventricle causing transtentorial herniation has important therapeutic implications. Although isolation can occur after intraventricular hemorrhage alone, infection and ventriculitis are significant factors in the development of an isolated fourth ventricle.

MR of slow CSF flow in the spine.

PURPOSE: To evaluate a slow-flow MR sequence in normal CSF flow and in CSF flow disturbance in cases of spinal stenosis. METHOD: The method was tested for flow sensitivity and applied to 67 sites of spinal canal compromise. RESULTS: Phantom studies show that flow can be depicted at a velocity of 0.5-1 mm/sec. On clinical images, stagnant CSF is black, flowing CSF is bright. Typically, in high-grade (90%-100%) stenosis, CSF above and below the site of spinal canal compromise (SCC) is black. With intermediate stenosis (50%-89%), CSF above the SCC remains white but becomes black distal to the SCC. Low-grade stenosis shows only localized flow disturbances. CONCLUSION: This easy-to-use sequence can solidify the MR diagnosis of high-grade stenosis when a distinct flow pattern is recognized. Flow patterns for intermediate and low-grade stenosis are less reliable.