Parasagittal Arachnoid Markings on the Inner Skull on Three-Dimensional CT: Relation between Hydrocephalus and Arachnoid Granules

The purpose of the study was to evaluate the number and size of arachnoid markings on the inner plate of the skull on 3D-CT. The subjects included 16 hydrocephalus and 26 non-hydrocephalus cases. We evaluated the correlation between age and both the number and sizes of the arachnoid markings, and compared them between hydrocephalus and non-hydrocephalus cases. We also evaluated cases exhibiting a “smooth cranium” that had no arachnoid markings at all on the inner plate. There was a positive correlation between age and the number of the arachnoid markings. There were no statistically significant differences in arachnoid markings between hydrocephalus and non-hydrocephalus cases, while, there were statistically significant differences in the frequency of “smooth cranium” findings in the population under ten years old. The “smooth cranium” can only be seen in hydrocephalus cases. These findings may be a clue to the morphological or functional changes of the arachnoid villi in hydrocephalus cases.

Diffusion anisotropy and diffusivity of white matter tracts within the temporal stem in Alzheimer disease: evaluation of the "tract of interest" by diffusion tensor tractography

PURPOSE

Our aim was to determine whether diffusion anisotropy and diffusivity of white matter tracts of the temporal stem in patients with Alzheimer (AD) can be evaluated independently by using diffusion tensor tractography.

MATERIALS AND METHODS

Subjects included 15 patients with AD (11 women and 4 men; mean age, 74 years) and 15 age-matched control subjects (11 women and 4 men; mean age, 72 years). Diffusion tensor images were acquired by using echo-planar imaging. We drew tractographies of the uncinate fasciculus, inferior occipitofrontal fasciculus, and Meyer's loop, with diffusion tensor analysis software. We measured diffusion anisotropy, diffusivity, and the number of voxels along the "tracts of interest" and used the Student t test to compare results between patients with AD and controls.

RESULTS

Values of diffusion anisotropy of the bilateral uncinate fasciculus and left inferior occipitofrontal fasciculus were significantly lower for patients with AD than for controls. Also, values of diffusivity in the bilateral uncinate fasciculus were significantly greater for patients with AD than for controls. There was no significant difference in diffusion anisotropy or diffusivity along Meyer's loop between the 2 groups. There was no significant difference in the number of voxels included in all constructed tracts between patients with AD and controls.

CONCLUSION

White matter tracts of the temporal stem can be evaluated independently by using diffusion tensor tractography, which appears to be a promising technique for determining changes in white matter in degenerative diseases.

Palmaz stent deployment for subclavian and brachiocephalic arterial occlusive disease. Factors predictive of restenosis

SUMMARY

Palmaz stent deployment is a useful method for subclavian and brachiocephalic arterial occlusive disease. We evaluated restenosis or intimal thickening after Palmaz stent deployment for nine lesions of subclavian or brachiocephalic arterial occlusive disease focusing on stent diameter, atheroma thickness near the stent, and degree of coverage for the lesion. Follow up DSA and IVUS at 5-14 months (mean 9) after therapy showed no significant changes in the size or shape of the stent itself There were two lesions of thin in-stent intimal hyperplasia and five lesions of thick hyperplasia. There was no close relationship between intimal hyperplasia and stent diameter or atheroma size (relative thickness). There was some relationship between the degree of coverage of the lesion by the stent and degree of intimal hyperplasia, but to determine statistical significance, accumulation of a greater number of cases is necessary.

Detection of early venous filling in gliomas on MRI: preliminary study by 2D time-resolved dynamic contrast-enhanced MR angiography with echo-sharing technique

We evaluated the detection of early venous filling of gliomas by 2D time resolved dynamic contrast enhanced MR digital subtraction angiography (MR-DSA) with echo-sharing technique and compared the results with those of conventional contrast digital subtraction angiography (C-DSA). C-DSA and MR-DSA examinations were performed in eight patients with malignant gliomas and compared with regard to the visualization of early filling veins; time intensity curves of arteries, early filling veins and normal veins were made, and rise time and time to peak were evaluated. MR-DSA visualized 12 out of 17 early filling veins depicted on C-DSA. The failure of five veins to be depicted may be due to the overlapping of other structures, such as other vessels and tumor stain. On time intensity curves, the mean difference in rise time was 0.9 sec between the artery and early filling vein, and the mean difference of time to peak was 1.6 sec. C-DSA has been the modality of choice in demonstrating early venous filling, a useful finding in the differential diagnosis of gliomas. However the high temporal resolution of MR-DSA with echo-sharing technique provides sufficient visualization of early venous filling of gliomas. Additional information for precise differential diagnosis may be obtained by adding MR-DSA to the imaging protocol for gliomas.

Enhancement pattern of normal extraocular muscles in dynamic contrast-enhanced MR imaging with fat suppression

PURPOSE

To evaluate the internal structure of normal extraocular muscles on fat-suppressed dynamic contrast-enhanced MR imaging.

MATERIAL AND METHODS

Ten subjects were examined using fat-suppressed dynamic contrast-enhanced MR imaging. We evaluated the enhancement pattern (C-shaped or ring-like) of extraocular muscles and quantified the maximum ratios of enhancement (Rmax) and maximum ratios of signal increase (Vmax). We also quantified Rmax and Vmax in the central and peripheral portions of medial rectus muscles.

RESULTS

In the early phase of dynamic contrast-enhanced MR imaging, a C-shaped or ring-like pattern was observed in 100% of inferior rectus, 95% of medial rectus, 55% of superior rectus, 20% of lateral rectus, and 15% of superior oblique muscles. Overall mean Rmax and Vmax values showed statistically significant differences to the temporal muscles. For the peripheral portion of medial rectus muscles, mean Rmax and Vmax values were greater than for the central portion.

CONCLUSION

Using fat-suppressed dynamic contrast-enhanced MR imaging, the C-shape or ring-like internal structure of the extraocular muscles could be visualized, and were considered to reflect their structure of orbital and global layers. Potential usefulness of the fat-suppressed dynamic contrast-enhanced MR imaging for detecting pathological status is suggested.

Efficacy of Palmaz Stent Deployment for Subclavian Artery Stenosis

Percutaneous angioplasty is a useful method for improvement of posterior circulation of the brain in subclavian artery stenosis and occlusion. Recently, the Palmaz stent was introduced for peripheral vessels stenosis. We evaluated the efficacy and care point of Palmaz stent deployment for subclavian artery stenosis in seven cases (5 stenosis and 2 occlusion) with symptoms and a mean age of 65.1 years. The stents could be deployed exactly at the stenotic region in all cases.

The pressure gradient disappeared in all cases, and the clots were fixed between vessel wall and stent. Antegrade circulation and significant clinical symptoms improvement were obtained in all cases. In angioplasty of subclavian artery stenosis, as compared with balloon angioplasty alone, Palmaz stent is a very useful device with fewer complications including distal thrombosis of the vertebrobasilar circulation.

Age correlation of the time lag in signal change on EPI-fMRI

PURPOSE

We measured the time lags between the start or end of tasks and signal changes in functional MRI (fMRI) for various age groups and evaluated the age correlation of the time lags.

METHODS

Forty subjects, 20-76 years old, were evaluated. fMRI was performed with and echo planar imaging sequence at 0.5 s intervals. We measured the time for the signal of the precentral gyrus to make a half-maximal increase after starting the task (T-inc) and the time to reach the initial level after ceasing the task (T-dec).

RESULTS

Average T-inc was 3.09 s and T-dec was 6.63 s. The values of T-inc could be correlated to age. T-dec had no age correlation.

CONCLUSION

The time lag in fMRI was revealed to be prolonged with increasing age. Our results suggest that the time lag in fMRI is influenced by some factors associated with aging.

Normal myelination of anatomic nerve fiber bundles: MR analysis

PURPOSE

In order to establish milestones of brain maturation by MR imaging, we examined the initiation of myelination of fiber bundles and of surrounding white matter.

METHODS

The subjects included 54 healthy infants ranging in age from 35 to 145 weeks by corrected gestational age. Images were obtained on a 1.5-T MR unit. In 24 sites of 18 fiber bundles in eight cross sections obtained perpendicular to the long axis of the brain stem, we analyzed the initiation of myelination and the age at which fiber bundles become indistinguishable owing to myelination of the surrounding white matter (blurring).

RESULTS

The fiber bundles were classified into two groups on the basis of the presence or absence of blurring. The first group (no blurring) was further divided into group 1A, in which myelination began at 35 weeks or less, and group 1B, in which myelination began at 44 weeks or later. The second group (blurring) was divided into group 2A, in which myelination began at 35 weeks or less and blurring occurred at 43 to 49 weeks; group 2B, in which myelination started at 35 weeks or less and blurring began at 67 to 145 weeks; and group 2C, in which myelination began at 36 weeks or later and blurring occurred at 67 to 145 weeks.

CONCLUSION

The time of blurring, when myelinated fiber bundles become indistinguishable from surrounding white matter owing to the initiation of myelination, is considered to be a useful parameter of brain maturation in infancy.

Venous architecture of cerebral hemispheric white matter and comments on pathogenesis of medullary venous and other cerebral vascular malformations

The parenchymal veins, especially the deep medullary veins, of the cerebral hemispheres were studied in detail by analyzing the stereoroentgenograms of multiple brain slices of postmortem injected brain specimens (injected into the internal carotid arteries in 17 cases and into the jugular veins in 12 cases). The presence of four zones--the first (or outer), the second (or candelabra), the third (or palmate) and the fourth (or subependymal) zone--of venous convergence was confirmed within the centrum semiovale, particularly in the frontoparietal area. Other venous convergences such as those related to the optic radiation in the para-atrial area were also found. Arterial branching zones were also observed in the areas similar to those of the medullary veins. It appears that these converging zones are created by rapidly growing crossing nerve fiber tracts, i.e., projection, commissural, and association fibers which grow rapidly during intrauterine and postnatal life. Pathogenesis of medullary venous malformation is also discussed from anatomical viewpoint, venoarchitecture of the pial, parenchymal, and subependymal veins and of the dural venous sinuses. The possibility of a similar mechanism (partial, mild, repetitive venoocclusive disease developing over a long period with fluctuating venous pressure) leading to formation of most (if not all) cases of medullary venous malformation and in some, if not many, cases of cerebral vascular malformations [aside from gene abnormality (chromosome 7) in familial cavernous angiomatosis, particularly in Hispanic American or other familial hereditary conditions] has been postulated.

[Correlation between MR imaging and histopathological findings of cystic metastatic brain tumors]

To clarify the correlation between the histopathological findings and MR signal intensity of the cyst wall, fifteen cystic metastatic brain tumors of eleven patients were imaged using a 0.5T MR unit just before surgery, and the MRI findings were correlated with the histopathological findings of resected lesions. On T2-weighted images, all cyst walls showed hypointensity. On T1-weighted images, the intensity of the cyst wall could be classified into three groups, compared with the cerebral cortex. Walls with hyperintensity on T1WI(group H; n = 6) consisted of ample tumor cells, blood vessels and connective tissues, suggesting viable tumor cells. Iso-intense walls on T1W1(group I; n = 3)had abundant reactive glial tissues. Hypointense walls on T1W1 (group L; n = 5)revealed hemorrhage and/or hemosicerin in the wall, suggesting hemorrhagic necrosis. Thus a good correlation was demonstrated between the MR signal intensities and histopathological findings of cyst walls of cystic metastatic brain tumors. This may contribute not only to more precise diagnosis on MRI but also to more planning for treatment of cystic brain metastases.

Fast fluid-attenuated inversion recovery (FAST-FLAIR) of ischemic lesions in the brain: comparison with T2-weighted turbo SE

PURPOSE

We compared fast fluid-attenuated inversion recovery (FAST-FLAIR) images with Turbo SE T2-weighted images to evaluate the detectability of small ischemic lesions in the brain.

MATERIALS AND METHODS

Thirty-six cases of multiple cerebral ischemic lesions were examined with FAST-FLAIR and Turbo SE imaging. The detectability of lesions, ability to discriminate lesions from the cortex, visualization of perivascular space, and visualization of brainstem lesions were compared between the two sequences.

RESULTS

The total number of lesions detected on both sequences was 534 in 36 cases. Six lesions in three cases were detected only on FAST-FLAIR, and one lesion in one case was detected only on the Turbo SE. All the 52 lesions located close to the cortex could be discriminated from the cortex on the FAST-FLAIR images, while 23 of these lesions could not be discriminated on the Turbo SE. Perivascular spaces were not visualized as areas of high signal on the FAST-FLAIR images. Pontine lesions that were visualized in four cases were clearer on the Turbo SE images than on the FAST-FLAIR images.

CONCLUSION

The FAST-FLAIR images were shown to be useful in the detection of ischemic lesions and in distinguishing them from the surrounding normal structures. The FAST-FLAIR sequence is expected to become a new additional routine sequence.

Identification of pre- and postcentral gyri on CT and MR images on the basis of the medullary pattern of cerebral white matter

The authors illustrate a new method to identify the pre- and postcentral gyri on computed tomographic (CT) and magnetic resonance (MR) images of the brain on the basis of the pattern of the medullary branches of the cerebral white matter. The most commonly used method to identify the gyri depends on recognition of the central sulcus by surface arrangement of the sulci. The two methods were compared by analysis of CT images of 104 subjects who had normal findings (age range, newborn to 60 years; 57 males and 47 females). The usefulness of the new method was also determined in angiographic studies of nine patients with space-occupying lesions. The method is especially helpful for identification of gyri on the lower level of the centrum semiovale and if space-occupying lesions are present that may result in a blurred depiction of sulci. Since MR imaging depicts the medullary branches more clearly than does CT, this new method should facilitate identification of the gyri with either modality.

Left-right asymmetry of the temporal and parietal regions in children: based on the medullary pattern of cerebral white matter

Lateralization of the posterior temporal lobe and inferior parietal lobule in childhood was studied on CT of 276 cases and compared with those in adulthood of 371 cases. CT images were analyzed based on the morphological features of medullary branches of the cerebral white matter. In children below 5 years of age, the left planum temporale was already more posteriorly located than the right in 56%, while the right was more so in 21%. The asymmetry of the middle temporal gyrus was similar to those of the planum temporale. The folding of the inferior parietal lobule was extensive and intricate on the left side in 63% and on the right side in 8% of children, almost identical to those in the adult. The visualization rates of the intraparietal sulcus were lower compared to those of the adult, but the higher visualization of the left side was a common tendency regardless of age. These alterations in left-right asymmetry seemed to be a morphologic substratum indicating the processes of localization of auditory function to those association areas.

MR and CT of tuberous sclerosis: linear abnormalities in the cerebral white matter

A review of MR and CT images in five patients, 8 months to 22 years old, diagnosed as having tuberous sclerosis, revealed linear abnormalities in the cerebral white matter. A linear abnormality connecting a subependymal nodule to a subcortical lesion was shown in two patients as an area of hypointensity on T1-weighted MR images and as an area of hyperintensity on T2-weighted images. These appeared as faintly high-density areas on CT images. Seventeen linear abnormalities extending from the ventricle to the cortex with a subependymal nodule or subcortical lesion on each end were visible in all five patients as areas of hyperintensity on the T2-weighted images. On the T1-weighted images, only nine hypointense lines were noted. CT scans did not show these latter lines. Linear abnormalities in cerebral white matter are suggestive of lesions of demyelination, dysmyelination, hypomyelination, or lines of migration disorder. MR imaging, especially T2-weighted, is particularly sensitive in detecting these abnormalities.