Showing papers in "American Journal of Neuroradiology in 2002"

Diffusion tensor MR imaging in diffuse axonal injury.

Abstract: BACKGROUND AND PURPOSE: Disruption of the cytoskeletal network and axonal membranes characterizes diffuse axonal injury (DAI) in the first few hours after traumatic brain injury. Histologic abnormalities seen in DAI hypothetically decrease the diffusion along axons and increase the diffusion in directions perpendicular to them. DAI therefore is hypothetically associated in the short term with decreased diffusion anisotropy. We tested this hypothesis by measuring the diffusion characteristics of traumatized brain tissue with use of diffusion tensor MR imaging. METHODS: Five patients with mild traumatic brain injuries and 10 control subjects were studied with CT, conventional MR imaging, and diffusion tensor imaging. All patients were examined within 24 hours of injury. In each participant, diffusion tensor indices from homologous normal-appearing white matter regions of both hemispheres were compared. These indices were also compared between homologous regions of each patient and the control group. In two patients, diffusion tensor images from the immediate posttrauma period were compared with those at 1 month follow-up. RESULTS: Patients displayed significant reduction of diffusion anisotropy in several regions compared with the homologous ones in the contralateral hemisphere. Such differences were not observed in the control subjects. Significant reduction of diffusion anisotropy was also detected when diffusion tensor results from the patients were compared with those of the controls. This reduction was often less evident 1 month after injury. CONCLUSION: White matter regions with reduced anisotropy are detected in the first 24 hours after traumatic brain injury. Therefore, diffusion tensor imaging may be a powerful technique for in vivo detection of DAI.

Posterior reversible encephalopathy syndrome: prognostic utility of quantitative diffusion-weighted MR images.

Abstract: BACKGROUND AND PURPOSE: The recently described posterior reversible encephalopathy syndrome (PRES) classically consists of reversible vasogenic edema in the posterior circulation territories, although conversion to irreversible cytotoxic edema has been described. We hypothesized that the extent of edema has prognostic implications and that diffusion-weighted MR imaging (DWI) can help predict the progression to infarction. METHODS: Twenty-two patients with PRES and 18 control subjects were examined with isotropic DWI. Nineteen regions of interest (ROIs) were systematically placed, and apparent diffusion coefficients (ADCs) were computed and correlated with T2 and DWI signal intensity in each ROI. RESULTS: T2 signal abnormalities were always present in territories of the posterior circulation. Anterior circulation structures were involved in 91% of patients. ADC values in areas of abnormal T2 signal were high. More extensive T2 signal abnormalities were seen in patients with a poor outcome than in patients who recovered. In six patients (27%), areas of high DWI signal intensity were seen with ADC values that were paradoxically normal, which we called pseudonormalized. Abnormal T2 signal intensity and high ADC values surrounded these areas. Follow-up images in two patients showed progression to infarction in pseudonormalized regions. CONCLUSION: Vasogenic edema in PRES involves predominantly the posterior circulation territories, but anterior circulation structures are also frequently involved. The extent of combined T2 and DWI signal abnormalities correlate with patient outcome. High DWI signal intensity and pseudonormalized ADC values are associated with cerebral infarction and may represent the earliest sign of nonreversibility as severe vasogenic edema progresses to cytotoxic edema.

Age-Related Total Gray Matter and White Matter Changes in Normal Adult Brain. Part I: Volumetric MR Imaging Analysis

Abstract: BACKGROUND AND PURPOSE: A technique of segmenting total gray matter (GM) and total white matter (WM) in human brain is now available. We investigated the effects of age and sex on total fractional GM (%GM) and total fractional WM (%WM) volumes by using volumetric MR imaging in healthy adults. METHODS: Fifty-four healthy volunteers (22 men, 32 women) aged 20–86 years underwent dual-echo fast spin-echo MR imaging. Total GM, total WM, and intracranial space volumes were segmented by using MR image-based computerized semiautomated software. Volumes were normalized as a percentage of intracranial volume (%GM and %WM) to adjust for variations in head size. Age and sex effects were then assessed. RESULTS: Both %GM and %WM in the intracranial space were significantly less in older subjects (≥50 years) than in younger subjects ( CONCLUSION: GM volume loss appears to be a constant, linear function of age throughout adult life, whereas WM volume loss seems to be delayed until middle adult life. Both appear to be independent of sex. Quantitative analysis of %GM and %WM volumes can improve our understanding of brain atrophy due to normal aging; this knowledge may be valuable in distinguishing atrophy of disease patterns from characteristics of the normal aging process.

Diffusion-tensor MR imaging of gray and white matter development during normal human brain maturation.

Abstract: BACKGROUND AND PURPOSE: Conventional MR imaging findings of human brain development are thought to result from decreasing water content, increasing macromolecular concentration, and myelination. We use diffusion-tensor MR imaging to test theoretical models that incorporate hypotheses regarding how these maturational processes influence water diffusion in developing gray and white matter. METHODS: Experimental data were derived from diffusion-tensor imaging of 167 participants, ages 31 gestational weeks to 11 postnatal years. An isotropic diffusion model was applied to the gray matter of the basal ganglia and thalamus. A model that assumes changes in the magnitude of diffusion while maintaining cylindrically symmetric anisotropy was applied to the white matter of the corpus callosum and internal capsule. Deviations of the diffusion tensor from the ideal model predictions, due to measurement noise, were estimated by using Monte Carlo simulations. RESULTS: Developing gray matter of the basal ganglia and developing white matter of the internal capsule and corpus callosum largely conformed to theory, with only small departures from model predictions in older children. However, data from the thalamus substantially diverged from predicted values, with progressively larger deviations from the model with increasing participant age. CONCLUSION: Changes in water diffusion during maturation of central gray and white matter structures can largely be explained by theoretical models incorporating simple assumptions regarding the influence of brain water content and myelination, although deviations from theory increase as the brain matures. Diffusion-tensor MR imaging is a powerful method for studying the process of brain development, with both scientific and clinical applications.

Fragile X Premutation Carriers: Characteristic MR Imaging Findings of Adult Male Patients with Progressive Cerebellar and Cognitive Dysfunction

Abstract: BACKGROUND AND PURPOSE: Our purpose was to characterize the findings of MR imaging of the brain of adult male fragile X premutation carriers with a recently identified disorder characterized by ataxia, tremor, rigidity, and cognitive dysfunction. METHODS: MR imaging studies of the brain of 17 male patients were characterized for signal intensity and for size of ventricles, cerebral and cerebellar sulci, and brain stem. Comparison was made with age- and sex-matched control participants. Southern blot and/or polymerase chain reaction methods were used to analyze CGG trinucleotide repeats in the fragile X mental retardation 1 gene. RESULTS: Fifteen of 17 patients showed symmetrically decreased T1 and increased T2 signal intensity in cerebellar white matter lateral, superior, and inferior to the dentate nuclei. Fourteen of 17 had similar signal intensity alterations in the middle cerebellar peduncles. Cerebellar cortical atrophy was present in 16 of 17 and cerebral atrophy in 17 of 17. Evan’s Index as a measure of ventricular size averaged 0.35 (range, 0.25–0.46), with that for age-matched control participants averaging 0.28 (range, 0.24–0.31) (P CONCLUSION: MR imaging findings in symptomatic male fragile X premutation carriers are characteristic of this disorder. Recognition of these alterations may support a specific diagnosis and may have implications for the potential occurrence of fragile X syndrome in the children of reproductive age female relatives.

Analysis and Classification of Cerebellar Malformations

Abstract: BACKGROUND AND PURPOSE: Because of improved visualization of posterior fossa structures with MR imaging, cerebellar malformations are recognized with increasing frequency. Herein we attempt to describe and propose a rational classification of cerebellar malformations. METHODS: MR images obtained in 70 patients with cerebellar malformations were retrospectively reviewed. The cerebellar malformations were initially divided into those with hypoplasia and those with dysplasia. They were then divided into focal and diffuse malformations. Finally, they were separated according to other features, such as brain stem involvement and cerebral involvement. RESULTS: All patients with diffuse cerebellar dysplasia (muscular dystrophy [n = 10], cytomegalovirus [n = 6], lissencephaly [n = 3],) had abnormalities of the cerebrum. Patients with focal cerebellar dysplasia of the Joubert (n = 12) and rhombencephalosynapsis (n = 8) types had variable cerebral dysplasia. Patients with nonsyndromic focal cerebellar dysplasia (isolated focal cerebellar cortical dysplasia [n = 2], cerebellar heterotopia with cerebellar cortical dysplasia [n = 1], idiopathic diffuse cerebellar dysplasia [n = 1], Lhermitte-Duclos syndrome [n = 1]) and those with cerebellar hypoplasia (isolated cerebellar hypoplasia [n = 6], pontocerebellar hypoplasia type 1 [n = 1]) had normal cerebra. Patients with features of Dandy-Walker malformation (n = 19) had both hypoplasia and dysplasia of the cerebellum. No notable difference was found between the cerebella of patients with large fourth ventricle cysts (Dandy-Walker malformations) and those without large fourth ventricle cysts (isolated cerebellar hypoplasia). Therefore, the Dandy-Walker malformation seems to be heterogeneous. CONCLUSION: Use of this classification system helps in the segregation and understanding of the relationship among cerebellar malformations. Although it will undoubtedly require revisions, this classification is a first step in combining imaging with molecular biology to facilitate understanding of cerebellar development and maldevelopment.

Brain abscess and necrotic brain tumor: discrimination with proton MR spectroscopy and diffusion-weighted imaging.

Abstract: BACKGROUND AND PURPOSE: Discriminating pyogenic brain abscesses from cystic or necrotic tumors is sometimes difficult with CT or MR imaging. We compared findings of proton MR spectroscopy (1H-MRS) with those of diffusion-weighted imaging to determine which technique was more effective for this differential diagnosis. METHODS: Fourteen patients (necrotic or cystic tumor [n = 7]; pyogenic abscess [n = 7]) who underwent 1.5-T 1H-MRS and diffusion-weighted imaging and had findings of ring-shaped enhancement after contrast agent administration were enrolled in this study. Diffusion-weighted imaging was performed with a single-shot spin-echo echo-planar pulse sequence (b = 1000 s/mm2). The apparent diffusion coefficient and ratio were also measured. RESULTS: Spectra for two patients were unacceptable because of either poor shimming conditions or contamination from neighboring fat. Spectra in three of five patients with abscess had lactate, amino acids (including valine, alanine, and leucine), and acetate peaks; one of the three spectra had an additional peak of succinate. In one patient with abscess treated by antibiotics, only lactate and lipid peaks were detected. Spectra for four of seven patients with cystic or necrotic tumors showed only lactate peaks. Lactate and lipids were found in three patients with tumors. Hyperintensity was seen in all the pyogenic abscess cavities and hypointensity in all the cystic and necrotic tumors on diffusion-weighted images. CONCLUSION:1H-MRS and diffusion-weighted imaging are useful for differentiating brain abscess from brain tumor, but the latter requires less time and is more accurate than is 1H-MRS. 1H-MRS is probably more limited in cases of smaller peripheral lesions, skull base lesions, and treated abscesses.

The craniocervical venous system in relation to cerebral venous drainage.

Abstract: BACKGROUND AND PURPOSE: Passing from the supine to the upright position favors cerebral venous outflow into vertebral venous systems rather than into the internal jugular veins. We sought to determine venous connections between dural venous sinuses of the posterior cranial fossa and craniocervical vertebral venous systems. METHODS: Corrosion casts of the cranial and cervical venous system were obtained from 12 fresh human cadavers, and anatomic confirmation was made by dissection of three previously injected fresh human specimens. MR venography was performed to provide radiologic correlation. RESULTS: The lateral, posterior, and anterior condylar veins and the mastoid and occipital emissary veins were found to represent the venous connections between the dural venous sinuses of the posterior cranial fossa and the vertebral venous systems. This study revealed the nearly constant presence of the anterior condylar confluent (ACC) located on the external orifice of the canal of the hypoglossal nerve. The ACC offered multiple connections with the dural venous sinuses of the posterior cranial fossa, the internal jugular vein, and the vertebral venous system. All these structures were shown by MR venography. CONCLUSION: The lateral, posterior, and anterior condylar veins and the mastoid and occipital emissary veins connect the dural venous sinuses of the posterior cranial fossa with the vertebral venous systems. These connections are clinically relevant, because encephalic drainage occurs preferentially through the vertebral venous system in the upright position. The ACC is a constant anatomic structure that may play an important role in the redirection of cerebral blood in the craniocervical region.

Diffusion-Weighted MR Imaging in Normal Human Brains in Various Age Groups

Abstract: BACKGROUND AND PURPOSE: Few studies have concerned the absolute apparent diffusion coefficient (ADC) values in the normal human brain and the effect of aging on diffusion. Therefore, our purpose was to determine whether the average ADC (ADCav) values in the various regions of the brain differ with age, sex, or hemisphere and to establish reference values of the absolute ADCav for further studies. METHODS: Subjects (40 men and 40 women) were chosen from a healthy population; age groups were 20–34, 35–49, and 50–64 years and 65 years or older (n = 20 each). All subjects were examined with MR imaging, including conventional and diffusion-weighted imaging in three orthogonal directions with two b values (0 and 1000 s/mm2) at 1.5 T. Bilateral ADCav values were determined in 36 regions of interest encompassing the entire brain. RESULTS: ADCav values were highest in the cortical gray matter ([0.89 ± 0.04] × 10−3 mm2/s; range, 0.78–1.09 × 10−3), lower in the deep gray matter ([0.75 ± 0.03] × 10−3 mm2/s; range, 0.64–0.83 × 10−3), and lowest in the white matter ([0.70 ± 0.03] × 10−3 mm2/s; range, 0.62–0.79 × 10−3). The ADCav values did not significantly change with aging, except for an increase in the lateral ventricles. No difference was observed between women and men or between the hemispheres. CONCLUSION: The data reported herein are representative, and the ADCav values can be used for reference in future studies and in clinical settings.

Detection and characterization of very small cerebral aneurysms by using 2D and 3D helical CT angiography.

Abstract: BACKGROUND AND PURPOSE: Many cases of subarachnoid hemorrhage are due to rupture of small cerebral aneurysms. Our purpose was to evaluate the usefulness of helical CT angiography (CTA) in the detection and characterization of very small ( METHODS: One hundred eighty consecutive patients underwent CTA for suspected intracranial aneurysms. All aneurysms prospectively detected by CTA were confirmed by digital subtraction angiography (DSA) or at surgery. CT angiograms and digital subtraction angiograms were reviewed by two independent blinded radiologists who performed aneurysm detection, quantitation, and characterization using 2D multiplanar reformatted and 3D volume-rendering techniques. RESULTS: Fifty-one patients harboring 41 very small intracranial aneurysms were included in this series. Eighty-one percent (33 of 41 aneurysms) were ≤4 mm in maximal diameter, and 37% (15 of 41 aneurysms) were ≤3 mm in maximal diameter. Sensitivity of CTA for very small intracranial aneurysm detection ranged from 98% to 100% (95% confidence intervals, 0.871, 0.999, 0.914, and 1.0), compared with 95% for DSA. The specificity of CTA and DSA for very small intracranial aneurysms was 100% (26 of 26 aneurysms). Positive predictive value ranged from 98% to 100%. Negative predictive value ranged from 96% to 100%. Accuracy of CTA for detection of very small intracranial aneurysms was 99% and 100% (κ = 0.969 − 1.0 ± 0.1221). Forty-eight percent of aneurysms were detected in the presence of subarachnoid hemorrhage. CONCLUSION: The sensitivity of CTA for the detection of cerebral aneurysms ≤5 mm is higher than that of DSA, with equal specificity and high interoperator reliability. High quality, noninvasive CTA aneurysm detection and characterization can be performed using routine clinical CT scanners and commercially available image processing workstations.

Diffusion tensor MR imaging of high-grade cerebral gliomas.

Abstract: BACKGROUND AND PURPOSE: Optimizing high-grade glioma treatment requires the delineation of edematous and normal brain from tumor, perhaps by using potential differences in the absolute diffusion parameters of water. Our purpose was to determine whether mean diffusivity 〈D〉 and diffusion anisotropic MR imaging data help in this differentiation. METHODS: Nine patients with high-grade cerebral glioblastoma underwent contrast-enhanced structural and diffusion tensor MR imaging before therapy. Tumor, edematous brain, and apparently normal white matter regions were determined on T2-weighted and contrast-enhanced T1-weighted structural images. Fractional anisotropy (FA) and 〈D〉 were measured in each tissue type. Differences in these values among the tissue types were assessed with a standard analysis of variance. RESULTS: 〈D〉 was highest in the necrotic tumor core (1825.38 ±404.06) × 10 −6 mm 2 /s, followed by edematous brain (1411.23 ± 322.31) × 10 −6 mm 2 /s, enhancing tumor core (1308.67 ± 292.50) × 10 −6 mm 2 /s, enhancing tumor margin (1229.80 ± 206.80) × 10 −6 mm 2 /s, and normal brain (731.53 ± 35.21) × 10 −6 mm 2 /s. FA was highest in normal brain (0.47 ± 0.08) and lowest in the necrotic core (0.09 ± 0.03). 〈D〉 was significantly different in enhancing tumor margins and edematous brain in all patients; FA was significantly different in only seven. These values were significantly different from those of normal brain in all cases in which they were measurable. CONCLUSION: 〈D〉 values can be used to differentiate normal white matter, edematous brain, and enhancing tumor margins. Diffusion anisotropic data added no benefit to tissue differentiation. Further studies are required to determine if a 〈D〉 value that corresponds to the limit of tumor invasion can be identified.

Evaluation of the stability of aneurysms after embolization using detachable coils: correlation between stability of aneurysms and embolized volume of aneurysms.

Abstract: BACKGROUND AND PURPOSE: The long-term outcome of aneurysmal coil embolization has not been determined. We retrospectively analyzed the results of our cases treated with detachable coils and evaluated the long-term stability of embolized aneurysms. METHODS: This study involved 100 aneurysms in 93 patients who underwent follow-up angiography ≥3 months after initial treatment between December 1993 and December 1999. The percentage of the coil volume occupying the aneurysm lumen (embolized volume) was used as an index to evaluate the stability of embolized aneurysms. The reliability of the embolized volume was also evaluated by comparing angiographic percentage occlusion. RESULTS: Follow-up angiographic assessment was conducted 12 ± 8.5 months after initial treatment. Angiographic evaluation of percentage occlusion at initial treatment did not always predict long-term stability of embolized aneurysms. Of 49 aneurysms judged as being totally occluded at initial treatment, 44 remained unchanged and five showed recanalization. The embolized volume of unchanged aneurysms was 30.8 ± 10.2%, and that of recanalized aneurysms was 19.9 ± 10.6%. There was a significant difference between these two groups ( P =.03). Of 29 subtotally occluded aneurysms, nine had further thrombosis (embolized volume = 31.8 ± 12.7%), nine remained unchanged (embolized volume = 23.2 ± 10.3%), and 11 had recanalization (embolized volume = 14.1 ± 6.1%). The mean embolized volume of 11 recanalized aneurysms was significantly lower than in the thrombosed group and the unchanged group ( P =.002 and P CONCLUSION: There is a significant correlation between embolized volume and stability of embolized aneurysms. Embolized volume is a more objective index than is subjectively angiographic percentage occlusion. In addition to angiographic assessment, measurement of embolized volume could be useful to predict angiographic changes of aneurysms.

Brain Atrophy in Mild or Moderate Traumatic Brain Injury: A Longitudinal Quantitative Analysis

Abstract: BACKGROUND AND PURPOSE: Although mild or moderate traumatic brain injury (TBI) is known to cause persistent neurologic sequelae, the underlying structural changes remain elusive. Our purpose was to assess decreases in the volume of brain parenchyma (VBP) in patients with TBI and to determine if clinical parameters are predictors of the extent of atrophy. METHODS: We retrospectively assessed the total VBP in 14 patients with mild or moderate TBI at more than 3 months after injury and in seven patients at two time points more than 3 months apart. VBP was calculated from whole-brain MR images and then normalized by calculating the percent VBP (%VBP) to correct for intraindividual variations in cranial size. Clinical parameters at the time of trauma were evaluated for potential predictors of atrophy. Findings were compared with those of control subjects of similar ages. RESULTS: In the single time-point analysis, brain volumes, CSF volumes, and %VBP were not significantly different between patients and control subjects. In the longitudinal analysis, the rate of decline in %VBP (0.02 versus 0.0064 U/day, P = .05) and the change in %VBP between the first and second time points (−4.16 ± 1.68 versus −1.49 ± 1.7, P = .022 [mean ±SD]) were significantly greater in patients. Change in %VBP was significantly greater in patients with loss of consciousness (LOC) than in those without LOC ( P = .023). CONCLUSION: Whole-brain atrophy occurs after mild or moderate TBI and is evident at an average of 11 months after trauma. Injury that produces LOC leads to more atrophy. These findings may help elucidate an etiology for the persistent or new neurologic deficits that occur months after injury.

Quantification of brain gray matter damage in different MS phenotypes by use of diffusion tensor MR imaging.

Abstract: BACKGROUND AND PURPOSE: Increasing evidence exists that cerebral gray matter (GM) from patients with multiple sclerosis (MS) is not spared. This study was performed to quantify in vivo the extent of cerebral GM pathologic abnormality in patients with relapsing-remitting (RR), secondary progressive (SP), and primary progressive MS, by using diffusion tensor (DT) MR imaging. METHODS: Dual-echo and DT MR imaging of the brain were performed in 102 patients with MS and 30 healthy volunteers. After GM segmentation using a technique based on diffusion anisotropy thresholding, average diffusivity (D) histograms of the cerebral GM were produced for all participants. RESULTS: All D histogram-derived metrics of the GM were significantly different between control volunteers and the whole MS population. No significant difference was found for any of the D histogram-derived metrics between control volunteers and patients with RRMS, whereas significant differences were found for D and D histogram peak location between control volunteers and patients with PPMS. All the D histogram-derived metrics differed significantly between patients with RRMS and patients with SPMS. Patients with SPMS also had significantly lower D than did patients with PPMS. All D histogram-derived metrics of the GM were strongly correlated with the T2 lesion volume. CONCLUSIONS: This study confirms the presence of brain GM changes in patients with MS. It also shows that the extent of such changes is greater during the progressive forms of the disease.

Incidental Findings on Pediatric MR Images of the Brain

Abstract: BACKGROUND AND PURPOSE: Previous studies have addressed the prevalence of incidental findings in symptomatic and healthy adult populations. Our study aims to elucidate the prevalence of incidental findings in a healthy pediatric population. METHODS: We retrospectively reviewed 225 conventional brain MR imaging studies obtained during structural and functional brain imaging research in a cohort of neurologically healthy children (l00 boys [44%] and 125 girls [56%]) ranging in age from younger than 1 month to 18 years. All MR images were reviewed, and two board-certified neuroradiologists categorized the findings by consensus. RESULTS: Incidental abnormalities were detected in 47 subjects (21%), while 79% of the images were normal. Of the 47 abnormalities detected, 17 (36%) required routine clinical referral; a single lesion (2%) required urgent referral. The occurrence of these findings in the male cohort was twice that of the female cohort; however, the percentage of subjects requiring either routine or urgent referral did not differ by sex (male subjects, 34%; female subjects, 39%). CONCLUSION: Although the frequency of clinically important incidental abnormalities was not high in the sample of children studied, the presence and variety of findings in any pediatric group is particularly important for both the welfare of the subject and for research in which knowledge of the subject’s neurologic status is vital to the interpretation of the results. Despite the limitations of the study in terms of the age and ethnic distribution, this work highlights the need for the routine involvement of trained radiologists in these studies to ensure that such incidental findings are detected and that appropriate follow-up is provided. With the advent of MR imaging as a powerful means of detecting both anatomic and functional information about the brain in health and disease, large numbers of presumably neurologically healthy volunteers have participated in imaging research studies over the past decade. From a research point of view, the confidence in the findings from such studies resides, at least in part, in the confidence that subjects are of the neurologic status intended. However, several groups have reported incidental radiologic findings in symptomatic and healthy adult populations. To our knowledge, the occurrence and management of incidental radiologic findings in a pediatric population, in whom the lifelong implications of such findings may be profound, have not been documented or well established. Moreover, from a subject-welfare point of view, MR imaging studies involving volunteers are frequently performed by persons other than physicians, and a trained radiologist may never review the images. Any unanticipated findings on these images may therefore go unrecognized, and the subjects may not receive the appropriate referral. The goals of the present study were 1) to determine the frequency and severity of incidental findings in a sample population of specifically of children who underwent brain MR imaging for research, and 2) to consider the implications of routinely involving neuroradiologists in these research studies.

Imaging findings of cochlear nerve deficiency.

Abstract: BACKGROUND AND PURPOSE: High-resolution T2-weighted fast spin-echo MR imaging provides excellent depiction of the cisternal and intracanalicular segments of the vestibulocochlear and facial nerves. Absence or reduction in caliber of the cochlear nerve (deficiency) has been described in association with congenital sensorineural hearing loss (SNHL). Depiction of cochlear nerve integrity may be important for diagnosis and management of SNHL. METHODS: We retrospectively reviewed high-resolution T2-weighted fast spin-echo MR images of 22 patients examined for SNHL who had deficiency of the cochlear nerve. Images were evaluated for the presence and comparative size of the component nerves (facial, cochlear, superior vestibular, and inferior vestibular nerves), relative size of the internal auditory canal (IAC), and any associated inner ear abnormalities. The clinical history, results of the clinical examination, and audiometric findings were reviewed for each patient. RESULTS: Deficiency of the cochlear nerve was observed in 12 patients with congenital SNHL and in 10 patients with acquired SNHL. Hypoplasia of the IAC was observed in association with congenital deficiency of the cochlear nerve in 11 of 12 patients. Deficiency of the cochlear nerve was observed in association with acoustic schwannoma in two cases and with acquired labyrinthine abnormalities in seven cases. Hypoplasia of the IAC was not observed in association with acquired SNHL. CONCLUSION: Deficiency of the cochlear nerve can be shown by high-resolution T2-weighted fast spin-echo MR imaging. Deficiency may be observed in association with congenital or acquired SNHL and may be important in the assessment of patients for cochlear implantation. Hypoplasia of the IAC is an indicator of congenital cochlear nerve deficiency.

Change in Brain Size During and After Pregnancy: Study in Healthy Women and Women With Preeclampsia

Abstract: BACKGROUND AND PURPOSE: Qualitative decreases in maternal brain size have been observed late in pregnancy. The aim of this study was to quantitatively evaluate changes to the maternal brain during and after healthy pregnancy and to compare these changes with those observed in cases of preeclampsia. METHODS: Three-dimensional T1-weighted MR volume images were obtained in nine healthy participants before and after delivery. Additional images were obtained in some of these participants before pregnancy, during pregnancy, and within 52 weeks after delivery. Five women with preeclampsia were examined before delivery and 6 weeks after delivery. Three of these patients were examined within 52 weeks after delivery. Images were registered, and both brain and ventricular volumes were calculated by using a semiautomated computer program. RESULTS: Both the healthy and preeclamptic groups had a reduction in brain size during pregnancy that was maximal at term and that reversed by 6 months after delivery. The ventricular size showed a corresponding increase in size during pregnancy and a decrease in size after delivery. In the preeclamptic patients, brain size was significantly smaller (P = .05) than in healthy participants, both before and after delivery. CONCLUSION: The brain decreases in size during pregnancy and increases in size after delivery. The changes follow a consistent time course in each woman. The mechanism and physiologic importance of these findings are speculative at the present time.

Cerebral Aneurysm Perforations Complicating Therapy with Guglielmi Detachable Coils: A Meta-Analysis

Abstract: BACKGROUND AND PURPOSE: The risk of intraprocedural aneurysm perforation in patients with previously ruptured aneurysms tends to be higher than that of patients with previously unruptured aneurysms, but a statistically significant difference has not been shown. Our purpose was to define the rates of occurrence and of morbidity and mortality associated with aneurysmal perforation associated with coil embolization. METHODS: A meta-analysis of the results from 17 published retrospective reports of aneurysm perforations complicating therapy with Guglielmi detachable coils (GDCs) was performed. Rates of perforation and associated morbidity and mortality in previously ruptured and unruptured aneurysms were calculated. The mechanism of perforation was noted. RESULTS: The risk of intraprocedural perforation was significantly higher in patients with ruptured aneurysms compared with patients with unruptured aneurysms (4.1% vs 0.5%; P < .001). The combined risk of permanent neurologic disability and death associated with intraprocedural aneurysm perforation was 38% for ruptured aneurysms and 29% for unruptured aneurysms. The morbidity and mortality rates with perforations caused by coils (39%) and microcatheters (33%) were similar. The morbidity and mortality rate for microguidewire perforations was considerably lower (0%, n 4) than the rates for coils and microcatheters, but number of cases was too low to indicate statistical significance. CONCLUSION: The risk of aneurysm perforation during GDC therapy is much higher in patients with previously ruptured aneurysms than in those with unruptured aneurysms. The morbidity and mortality rates are substantial for perforations caused by coils and microcatheters, whereas they seem to be much lower for perforations caused by microguidewires.

Age-Related Total Gray Matter and White Matter Changes in Normal Adult Brain. Part II: Quantitative Magnetization Transfer Ratio Histogram Analysis

Abstract: BACKGROUND AND PURPOSE: The magnetization transfer ratio (MTR) is a sensitive and quantitative identifier of underlying structural changes in the brain. We quantitatively evaluated age- and sex-related MTR changes in global gray matter (GM) and global white matter (WM) in healthy adults. METHODS: Fifty-two healthy volunteers (21 men, 31 women) aged 20–86 years underwent dual-echo fast spin-echo and magnetization transfer imaging performed with and then without a saturation pulse. GM and WM were distinguished by using a computer-assisted semiautomated segmentation technique. MTR histograms were generated for each segmented tissue in each subject and compared among age and sex groups. RESULTS: The mean, median, first quartile, and peak height of the MTR histogram were significantly lower in the older group (≥50 years) than those in the younger group ( CONCLUSION: The different MTR values for both GM and WM in the two age groups suggest that notable microscopic changes occur in GM and WM with advancing age, yet no significant sex-related variations in MTR measurements were found in these neurologically healthy adults. Such normative data based on the inherent contrast in MTRs are essential in studies of specific disorders of aging, and they may have implications for our understanding of the gross structural changes in both GM and WM in the aging brain.

Comparison of three-dimensional rotational angiography with digital subtraction angiography in the assessment of ruptured cerebral aneurysms.

Abstract: BACKGROUND AND PURPOSE: Rotational angiography (RA) and digital subtraction angiography (DSA) together may depict more intracranial aneurysms than DSA alone. We compared the diagnostic value of 3D RA and biplanar DSA in detecting, classifying, and planning treatment for ruptured intracranial aneurysms. METHODS: A total of 53 patients with acute subarachnoid hemorrhage (Hunt and Hess grades I-V) underwent angiography with both methods. DSA was performed in two to six standard projections in every vascular territory. Three-dimensional RA datasets were evaluated by using surface-shaded display and maximum intensity projection. The usefulness of DSA images and 3D datasets in detecting aneurysms (number, configuration) and treatment planning were retrospectively analyzed in a blinded manner. RESULTS: In 42 patients, 56 aneurysms were detected, (one to five per patient; size, 0.6-20.4 mm); no aneurysm was found in 11 patients. RA revealed seven aneurysms not seen at conventional DSA. RA failed to depict one aneurysm visible only in a compression series. Delineation of the aneurysmal neck improved with RA in 71% of cases; the parent vessel and its relationship to adjacent vessels was demonstrated better with RA than with DSA in 45% and 50%, respectively. Endovascular treatment was proposed in nine patients; microsurgical therapy, in 26. In seven patients, both options were rated as being equal. Actual treatment consisted of eight endovascular procedures and 30 neurosurgical operations. Four patients died before therapy. CONCLUSION: Compared with DSA, 3D RA allows more exact depiction of anatomic details that are important in planning surgery and interventional therapy for intracranial aneurysms. RA depicted more aneurysms.

Proton Magnetic Resonance Spectroscopy of the Thalamus in Patients with Chronic Neuropathic Pain after Spinal Cord Injury

Abstract: BACKGROUND AND PURPOSE: Spinal cord injury (SCI) results in a number of consequences; one of the most difficult to manage is chronic neuropathic pain. Thus, defining the potential neural and biochemical changes associated with chronic pain after SCI is important because this may lead to development of new treatment strategies. Prior studies have looked at the thalamus, because it is a major sensory relay station. The purpose of our study was to define alterations in metabolites due to injury-induced functional changes in thalamic nuclei by using single-voxel stimulated echo acquisition mode MR spectroscopy. METHODS: Twenty-six men were recruited: 16 patients with SCI and paraplegia (seven with pain, nine without pain) and 10 healthy control subjects. Pain was evaluated in an interview, which included the collection of information concerning the location, quality, and intensity of pain, carefully identifing the dysesthetic neuropathic pain often seen in SCI. Localized single-voxel (8-cm3 volume) proton spectra were acquired from the left and right thalami. RESULTS: The concentration of N -acetyl (NA) was negatively correlated with pain intensity ( r = −0.678), and the t test showed that NA was significantly different between patients with pain and patients without pain ( P = .006). Myo -inositol was positively correlated with pain intensity ( r = 0.520); difference between patients with pain and those without pain was almost significant ( P = .06). CONCLUSION: The observed differences in metabolites in SCI patients with and pain and in those without pain suggest anatomic, functional, and biochemical changes in the thalamic region.

Contrast-enhanced 3D MR angiography of the carotid artery: comparison with conventional digital subtraction angiography.

Abstract: BACKGROUND AND PURPOSE: Since 1996, several preliminary studies have shown the usefulness of contrast material–enhanced MR angiography for imaging supraaortic vessels. The aim of this study was to compare the accuracy of contrast-enhanced 3D MR angiography with that of digital subtraction angiography (DSA) in the evaluation of carotid artery stenosis. METHODS: A blinded comparison of first-pass contrast-enhanced MR angiography with conventional DSA was performed in 120 patients (240 arteries). MR angiography was performed with a 1.5-T magnet with gradient overdrive equipment, by using a coronal radiofrequency-spoiled 3D fast low-angle–shot sequence after the intravenous injection of gadodiamide. The guidelines of the North American Symptomatic Carotid Endarterectomy Trial for measuring stenosis of the internal carotid artery were applied on maximum intensity projection (MIP) images and conventional catheter angiograms. RESULTS: Grading of stenoses on MR angiograms agreed with grading of stenoses on DSA images in 89% of arteries. In the severe stenosis group (70–99%), agreement was 93%. All internal carotid occlusions (n = 28) and seven of nine pseudo-occlusions were accurately detected with contrast-enhanced MR angiography. The correlation between MR angiography and DSA for determination of minimal, moderate, and severe stenoses and occlusion was statistically significant (r = 0.91, P CONCLUSIONS: This investigation with a large number of patients confirms that contrast-enhanced MR angiography could become a diagnostic alternative to DSA in the treatment of patients with carotid artery disease.

Cytoarchitecture of the human cerebral cortex: MR microscopy of excised specimens at 9.4 Tesla.

Abstract: BACKGROUND AND PURPOSE: The laminar patterns displayed by MR microscopy (MRM) form one basis for the classification of the cytoarchitectonic areas (Brodmann areas) It is plausible that in the future MRM may depict Brodmann areas directly, and not only by inference from gross anatomic location Our purpose was to depict the laminar cytoarchitecture of excised, formalin-fixed specimens of human cerebral cortex by use of 94-T MR and to correlate MR images with histologic stains of the same sections METHODS: Formalin-fixed samples of human sensory isocortex (calcarine, Heschl’s, and somatosensory cortices), motor isocortex (hand motor area of M1), polar isocortex (frontal pole), allocortex (hippocampal formation), and transitional periallocortex (retrosplenial cortex) were studied by MRM at 94 T with intermediate-weighted pulse sequences for a total overnight acquisition time of 14 hours 17 minutes for each specimen The same samples were then histologically analyzed to confirm the MR identification of the cortical layers Curves representing the change in MR signal intensity across the cortex were generated to display the signal intensity profiles for each type of cortex RESULTS: High-field-strength MR imaging at a spatial resolution of 78 × 78 × 500 μm resolves the horizontal lamination of isocortex, allocortex, and periallocortex and displays specific intracortical structures such as the external band of Baillarger The signal intensity profiles demonstrate the greatest hypointensity at the sites of maximum myelin concentration and maximum cell density and show gradations of signal intensity inversely proportional to varying cell density CONCLUSION: MRM at 94 T depicts important aspects of the cytoarchitecture of normal formalin-fixed human cortex

Comparison of 2D and 3D Digital Subtraction Angiography in Evaluation of Intracranial Aneurysms

Abstract: BACKGROUND AND PURPOSE: Although digital subtraction angiography (DSA) is considered the criterion standard for depiction of intracranial aneurysms, it is often difficult to determine the relationship of overlapping vessels to aneurysms when using 2D DSA. We compared 2D and 3D DSA in evaluation of intracranial aneurysms. METHODS: Thirty-six consecutive patients with cerebral aneurysms underwent 2D and 3D DSA. After standard 2D DSA, rotational DSA was performed. Maximum intensity projection (MIP) and shaded surface display (SSD) images were created from the rotational DSA data sets. All images were assessed randomly for overall image quality, presence of aneurysm, presence of aneurysmal lobulation, visualization of aneurysmal neck, and relationship to adjacent vessels. Data analysis was conducted for 40 aneurysms treated by clip placement. RESULTS: One aneurysm that was not detected at 2D DSA was classified as uncertain on the basis of rotational DSA. All aneurysms were classified as probably or definitively present on the basis of MIP and SSD findings. Overall image quality of rotational DSA, MIP, and SSD was statistically inferior to that of the standard 2D DSA for visualization of distal arteries. However, MIP and SSD images were significantly superior to those of standard 2D DSA for all other evaluations. For detection of lobulation, SSD images were significantly superior to other images, and for visualization of aneurysmal neck and relationship to neighboring arteries, SSD images were significantly superior to those of rotational DSA. For evaluation of the relationship to neighboring arteries, MIP images were significantly superior to those of rotational DSA. CONCLUSION: Three-dimensional DSA, especially SSD, provided more detailed information for evaluating cerebral aneurysms than did standard 2D and rotational DSA.

Temporal Lobe Morphology in Normal Aging and Traumatic Brain Injury

Abstract: BACKGROUND AND PURPOSE: Little is known regarding changes in the temporal lobe associated with traumatic brain injury (TBI) in early-to-mid adulthood. We report on two quantitative MR studies: study 1 addressed age-related changes of the temporal lobe in subjects aged 16–72 years; information obtained in this study provided a normative database for comparison with findings in 118 patients with TBI who were included in study 2. We expected stable morphology in healthy subjects and trauma-related atrophy in patients with TBI. METHODS: MR multispectral tissue segmentation was used to calculate bilateral temporal lobe gyrus and sulcus, sylvian fissure CSF, hippocampus, and temporal horn volumes and to measure the white matter (WM) temporal stem. RESULTS: With normal aging, gyral volume remained stable, decreasing approximately 0.26% per year (total, ≈11%). Sulcal CSF volume doubled. Hippocampal volume decreased (minimally, significantly); temporal horn volume increased (not significantly) and was minimally related to hippocampal volume. WM measurements were constant. Trauma changed morphology; WM measures decreased. Gyral volumes were not different between the groups. In TBI, CSF volume increased significantly, was most related to reduced WM measurements, and was relatively independent of gyral volume. Temporal horn dilatation was related more to WM atrophy than to hippocampal atrophy. In TBI, subarachnoid sulcal and temporal horn CSF volumes were most related to WM atrophy, which was relatively independent of gyral volume; gyral and hippocampal volumes and WM measures were related to memory performance. CONCLUSION: Age-related changes cause minimal temporal lobe gyral, hippocampal, temporal horn, and WM atrophy. Only subarachnoid sulcal CSF volume changed robustly. Trauma produced disproportionate WM loss associated with increased temporal horn and sulcal CSF volumes; it caused substantial hippocampal atrophy, which was related to memory impairment. Gyral volume did not decrease, although it was related to memory performance.

Intraarterially administered verapamil as adjunct therapy for cerebral vasospasm: safety and 2-year experience.

Abstract: BACKGROUND AND PURPOSE: Despite the widespread use of angioplasty, adjunct chemical therapy is often needed to treat patients with cerebral vasospasm. In this study, we examined the safety of intraarterial administration of verapamil to patients with cerebral vasospasm. We herein summarize our 2-year experience with this treatment. METHODS: We retrospectively reviewed the procedure reports, anesthesia records, clinical charts, and brain images of 29 patients who received intraarterially administered verapamil in 34 procedures for the treatment of vasospasm after subarachnoid hemorrhage from July 1998 to June 2000. The average changes in mean arterial pressure and heart rate were used to measure cardiovascular side effects. The neurologic effects were assessed by angiographic findings, the results of neurologic examinations performed before and after the procedure, and findings of CT of the head. RESULTS: The average dose of verapamil per patient was 3 ± 0 mg or 44 ± 5 mcg/kg. The average changes in mean arterial pressure at 10 and 20 minutes were −5 ± 1 mm Hg and −2 ± 1 mm Hg or −3.8 ± 1.0% and −1.7 ± 1.1%, respectively. No significant change of heart rate was observed at 10 minutes. The patients showed no sign of increased intracranial pressure by hemodynamic parameters, neurologic examination, or CT of the head. On 10 occasions, when the effect of verapamil infusion was assessed angiographically, there was 44 ± 9% increase of vessel diameter in the spastic segment. Neurologic improvement was noted after five of 17 procedures when verapamil was used as the sole treatment. CONCLUSION: Low dose verapamil is safe when administered intraarterially to patients with cerebral vasospasm. Beneficial effects are achieved in some patients, prompting further study of its efficacy.

Cerebral ischemia detected with diffusion-weighted MR imaging after stent implantation in the carotid artery

Abstract: BACKGROUND AND PURPOSE: Concern regarding the safety of stent implantation in the carotid artery exists because of the risk of cerebral embolization during the procedure. The purpose of this prospective study was to determine the incidence of new areas of cerebral ischemia, as detected by using diffusion-weighted MR imaging after stent implantation in the carotid artery. METHODS: Diffusion-weighted MR imaging of the brain was performed in 67 patients with 70 high-grade stenoses of the carotid artery before and 24 hours after stent implantation. RESULTS: The neurologic status of the patients was unchanged after 69 of 70 procedures. During one procedure, symptomatic cerebral embolization occurred. Diffusion-weighted MR images showed new ipsilateral lesions after stent implantation in 20 patients (29%), including the symptomatic patient, and new contralateral lesions in six patients (9%). Fifty-two of 59 postprocedural lesions occurred in the vascular territory supplied by the treated vessel. The occurrence of new postprocedural ipsilateral lesions was not significantly correlated with patient demographic data, characteristics of the stenoses, or details of the procedure. CONCLUSION: In 29% of the procedures, stent implantation in the carotid artery was associated with new areas of cerebral ischemia, as detected by using diffusion-weighted MR images; these findings indicated the occurrence of cerebral microemboli during such procedures. In all patients except one, the new lesions were clinically silent.

N-butyl cyanoacrylate embolization of cerebral arteriovenous malformations: Results of a prospective, randomized, multi-center trial

Abstract: BACKGROUND AND PURPOSE Liquid N-butyl cyanoacrylate (n-BCA) use for the treatment of arteriovenous malformations (AVM) in the brain has become part of medical practice. However, no study has led to the Food and Drug Administration's approval of n-BCA for intravascular use. The purpose of this study was to verify the effectiveness and safety of an n-BCA/Tantalum Powder/Ethiodized Oil mixture, compared with conventional treatment (Trufill polyvinyl alcohol [PVA]) for preoperative embolization of cerebral AVM. METHODS Between October 15, 1996, and March 24, 1999, 104 patients at 13 centers were prospectively randomized to undergo embolization using an n-BCA/Tantalum Powder/Ethiodol mixture or Trufill PVA. The pre-embolization therapy goals were determined in terms of the number of pedicles to be embolized and the percent of nidus reduction expected. Embolization results were evaluated by a central laboratory. Subsequent surgical resection data were recorded. Safety evaluation data included recording device complications, procedure complications, and intracranial events/overall neurologic outcomes, which could be either device-related, procedure-related, or both. RESULTS The reduction of AVM dimensions (79.4% in the n-BCA group and 86.9% in the PVA group) and the mean number of vessels embolized (2.2 in the n-BCA group and 2.1 in the PVA group) was similar in the two groups. Coils were used more commonly with PVA embolization (P<.0001). No differences were detected in surgical resection time, number of patients who required transfusion, volume and number of transfusion units, or type and volume of fluid replacement. Glasgow Outcome Scale scores were not significantly different between the two groups before treatment, after embolization, or after resection. Two of 42 patients who underwent resection and had been treated with n-BCA experienced post-resection hematoma, compared with eight of 45 patients who underwent resection and had been treated with PVA (P<.05). CONCLUSION This prospective, randomized trial showed that n-BCA is equivalent to PVA as a preoperative embolic agent for treatment of cerebral AVM as determined by percent of nidus reduction and number of feeding pedicles embolized.

New expandable hydrogel-platinum coil hybrid device for aneurysm embolization.

Abstract: This study introduces a new, hybrid embolic device that in addition to offering all the important attributes of existing detachable platinum coils also shows an enhanced ability to fill aneurysm cavities. The device consists of a carrier platinum coil coupled to an expandable hydrogel material, which undergoes a ninefold increase in volume when placed into a physiological environment. Distinct from previous devices aimed at speeding the organization of thrombus, the new device has been designed to entirely fill the aneurysm cavity, with complete or near-complete exclusion of thrombus. Unlike thrombus, the hydrogel material is stable and unaffected by natural thrombolytic processes and thus may diminish observed rates of aneurysm recanalization. We report the angiographic and histologic findings of the new, hybrid device used to treat experimental aneurysms in rabbits.

Paradoxical cerebral arterial embolization of cement during intraoperative vertebroplasty: Case report

Abstract: Paradoxical cerebral embolism of cement occurred in a 78-year-old woman after cement-assisted transpedicular spinal fixation surgery. Multiple pulmonary emboli of polymethylmethacrylate precipitated pulmonary hypertension and right-to-left shunting into the systemic circulation through a patent foramen ovale. This rare complication occurred because of failure to recognize venous migration of cement during the procedure and the injection of multiple levels in one setting. Although this was an open procedure, the technical aspects were the same as for vertebroplasty and the precautions should be applied to percutaneous vertebroplasty.