Posttraumatic smell loss: relationship of psychophysical tests and volumes of the olfactory bulbs and tracts and the temporal lobes

RATIONALE AND OBJECTIVES: The purpose of this study was to define the primary sites of injury in patients with posttraumatic anosmia and hyposmia with magnetic resonance (MR) imaging and to determine if these sites correlated with the results of psychophysical olfactory tests. MATERIALS AND METHODS: Thirty-six patients with subjective loss in olfaction after head trauma underwent volumetric MR studies of the olfactory bulbs and tracts and temporal lobes. Pearson correlations were computed between olfactory bulb and tract and temporal lobe volumes and the patients' scores on tests of odor identification (including the University of Pennsylvania Smell Identification Test [UPSIT]), detection, and memory. Analysis of variance was used to compare volumes of the control subjects and the posttraumatic patients. RESULTS: The olfactory bulbs and tracts (32 [89%] of 36 patients), the subfrontal lobes (22 [61%] of 36 patients), and the temporal lobes (11 [31%] of 36 patients) showed the highest incidence of posttraumatic encephalomalacia. Left olfactory bulb and tract volumes showed a statistically significant correlation with left and total UPSIT scores. A statistically significant difference (P < .001) was found in the right and left olfactory bulb and tract volumes between anosmic and hyposmic patients and between posttraumatic patients and control subjects. CONCLUSION: Olfactory bulb and tract damage may correlate with deficits in odor identification. Olfactory bulb and tract and frontal lobe encephalomalacia coexist in many patients.     

磁共振弥散张量成像对正常大脑白质纤维束构象的初步研究

目的利用磁共振弥散张量成像(DTI)研究正常成人脑内各部位各向异性程度及正常白质纤维束构象特征.方法对25名正常志愿者进行常规MR及DTI序列检查,重建FA图及三维彩色编码张量图.分别在半卵圆中心、基底节区和大脑脚层面测量主要白质束的FA值.结果DTI显示灰质与白质区各向异性存在显著差异,不同部位的白质纤维束各向异性程度亦不相同,且左右两侧基本对称,重建FA图和三维彩色编码张量图可显示白质内大部分主要的白质纤维束.结论DTI可清晰显示脑内白质纤维束的走行及分布,为了解脑功能与白质通路间关系提供了有力研究手段.     

Intraoperative diffusion-tensor MR imaging: shifting of white matter tracts during neurosurgical procedures--initial experience

PURPOSE: To prospectively evaluate the location of white matter tracts with diffusion-tensor imaging (DTI) during neurosurgical procedures. MATERIALS AND METHODS: Ethical committee approval and signed informed consent were obtained. A 1.5-T magnetic resonance imager with an adapted rotating surgical table that is placed in a radiofrequency-shielded operating theater was used for pre- and intraoperative imaging. DTI was performed by applying an echo-planar imaging sequence with six diffusion directions in 38 patients (20 female patients, 18 male patients; age range, 7-77 years; mean age, 45.6 years) who were undergoing surgery (35 craniotomy and three burr hole procedures). Color-encoded maps of fractional anisotropy were generated by depicting white matter tracts. A rigid registration algorithm was used to compare pre- and intraoperative images. RESULTS: Intraoperative DTI was technically feasible in all patients, and no major image distortions occurred in the areas of interest. Pre- and intraoperative color-encoded maps of fractional anisotropy could be registered; these maps depicted marked and highly variable shifting of white matter tracts during neurosurgical procedures. In the 27 patients who underwent brain tumor resection, white matter tract shifting ranged from an inward shift of 8 mm to an outward shift of 15 mm (mean shift +/- standard deviation, outward shift of 2.5 mm +/- 5.8). In 16 (59%) of 27 patients, outward shifting was detected; in eight (30%), inward shifting was detected. In eight patients who underwent temporal lobe resections for drug-resistant epilepsy, shifting was only inward and ranged from 2 to 14 mm (9 mm +/- 3.3). In two of the three patients who underwent burr hole procedures, outward shifting occurred. CONCLUSION: Intraoperative DTI can depict shifting of major white matter tracts that is caused by surgical intervention.     

Diagnosis of fistulae and sinus tracts in patients with Crohn disease: value of MR imaging

To investigate the potential of MR imaging in the evaluation of sinus tracts or fistulae associated with Crohn disease, 17 patients with pelvic or abdominal fistulae or sinus tracts underwent MR imaging with multislice spin-echo techniques, 500/15 and 1600/22,80 (TR/TE). The presence of fistulae and/or sinus tracts was confirmed by contrast-enhanced CT (n = 17) and/or sonography (n = 8), sinography (n = 6), or barium studies (n = 4). In all but three cases the fistulae and extramucosal inflammatory abnormalities were shown by MR. T1-weighted images provided excellent delineation of the extension of the fistulae relative to sphincters and adjacent hollow viscera and showed inflammatory changes in fat planes. T2-weighted images showed fluid collections within the fistulae, localized fluid collections in extraintestinal tissues, and inflammatory changes within muscles. The supralevator and infralevator compartments were well defined on coronal images. Thus, the perirectal spread of fistulae and sinus tracts with respect to the levator ani could be demonstrated in all cases. Our results suggest that MR imaging is useful for the demonstration and evaluation of pelvic and abdominal sinus tracts or fistulae associated with Crohn disease.     

Normal and abnormal white matter tracts shown by MR imaging using directional diffusion weighted sequences

A pulsed magnetic field gradient spin echo technique was used to study the brain of two volunteers and eight patients. The pulsed gradients were applied both perpendicular and parallel to the image slice. Striking changes in signal intensity were demonstrated in white matter depending on the direction in which pulsed gradients were applied. These effects enabled specific white matter tracts to be identified depending on the direction of their fibres. Abnormalities were also demonstrated in these tracts in patients with a variety of diseases, including cases where only minor abnormalities were seen with conventional, highly T2-weighted sequences. The effects were attributed to anisotropically restricted diffusion within white matter. The technique may have application in a wide range of neurological disease and result in better localisation of lesions and improved detection of disease.     

Malformations of cortical development: high-resolution MR and diffusion tensor imaging of fiber tracts at 3T

Patients with malformations of cortical development and epilepsy may have a variety of abnormal brain findings, including abnormal gyral patterns, cortical thickening, decreased volume of white matter, and increased diffusion of white matter. The status of individual white matter fiber tracts, however, is unknown. We present a case of bilateral frontal schizencephaly and subcortical heterotopia and illustrate alterations of white matter fascicles by combined structural and functional diffusion tensor imaging at 3 T.     

Calcification of the olfactory bulbs in three patients with hyposmia

An estimated two million Americans suffer from chemosensory disorders. We present the clinical and imaging findings in three hyposmic patients with bilateral olfactory bulb calcification detected by CT. To our knowledge, these are the first cases of olfactory bulb calcification reported in the literature. A review of the literature concerning calcification of cranial nerves, olfactory neuritis, and the potential etiology and clinical significance of olfactory bulb calcification in our patients is presented.     

Holoprosencephaly in children: diffusion tensor MR imaging of white matter tracts of the brainstem--initial experience

PURPOSE: To determine technical success with percutaneous abscess drainage (PAD) in patients with Crohn disease during 14 years. MATERIALS AND METHODS: Medical records of 32 patients with Crohn disease who underwent PAD from 1985 to 1999 were reviewed. Results of abscess drainage and nature of subsequent surgical procedures were recorded. Factors assessed included postoperative or spontaneous nature of the abscess, documentation of a proved fistula, history of occurrence of prior abscesses, duration of Crohn disease, and use of steroid treatment. Technical success was defined as complete abscess drainage. Short-term success was defined as avoidance of surgery within 60 days of drainage. Long-term success was defined as avoidance of surgery beyond the initial 60-day period. Short-term avoidance of surgery was assessed as a predictor of the need for surgery in the long term. Statistical analysis was performed with the chi(2) test to evaluate predictors of short-term success and to assess short-term success as a predictor of long-term success. RESULTS: The technical success rate was 96%. In 16 (50%) of 32 patients, the need for surgery in the short term was avoided, and surgery was more likely to be avoided in patients with postoperative abscesses than in those with spontaneous abscesses (P =.07). At long-term follow-up, short-term avoidance of surgery did not significantly increase the likelihood of need for surgery in the long term, which occurred in nine of 16 short-term successes versus five of 15 short-term failures (P =.55). Recurrent abscesses occurred in seven (22%) patients, a rate comparable to that with surgical abscess drainage; four (44%) of nine cases of re-drainage were successful. CONCLUSION: PAD has a high technical success rate of 96%. Half of patients may avoid surgery in the short term.     

帕金森病小脑和嗅束白质完整性损害的扩散张量成像研究

帕金森病(Parkinson's disease,PD)患者有运动和非运动系统的临床症状,嗅觉减退为其主要非运动症状之一.DWI及DTI已经成功应用于PD和帕金森叠加综合征的诊断和鉴别诊断[1].咖是研究脑白质纤维结构完整性改变的一种先进技术,而基于体素分析法(voxel based analysis,VBA)可以不依赖操作者从全脑角度客观分析局部脑白质的改变[2].     

Heavily T2-weighted MR imaging of white matter tracts in the hypothalamus: normal and pathologic demonstrations

BACKGROUND AND PURPOSE: The MR appearance of white matter tracts in the hypothalamus and the role of the hypothalamus as a memory mechanism have not been sufficiently described in clinical settings. Heavily T2-weighted black-and-white reversed (T2R) images were assessed to reveal their visualization and clinical significance. METHODS: One hundred healthy subjects and three patients with hypothalamic lesions underwent fast spin-echo MR imaging to reveal the postcommissural fornix (PF) and mammillothalamic tract (MT). RESULTS: The PF was identifiable in axial and/or coronal sections in all healthy subjects. No remarkable asymmetry of its size or course was evident. Both anteroposterior and vertical dimensions ranged from 10.5 to 14 mm. The MT was visible in one or two axial sections above the mammillary body in 64% of healthy subjects and in a coronal section in 36%. Two patients with glioblastoma multiforme and lacunar infarct at the hypothalamus presented with anterograde amnesia; T2R imaging revealed involvement of both the PF and MT. The third patient had a suprasellar craniopharyngioma with PF injury sparing the MT resulting from surgical manipulation and was free of memory deficit. Anterograde amnesia was evident only when both the PF and MT were injured. CONCLUSION: T2R images have made a high rate of detection of the PF and MT possible and could provide a more detailed correlation of hypothalamic neuroanatomy and memory mechanism in clinical settings.     

Identification of the corticospinal tracts achieved using blood-oxygen-level-dependent and diffusion functional MR imaging in patients with brain tumors

Diffusion-weighted MR imaging was used to delineate the corticospinal tract (CST) successfully and to depict its relationship to adjacent brain tumors. The CST was defined by a method by which it seems possible to delimit the distance from the CST to the main tumor mass and to show displacement and infiltration of the tract by the neoplasia. This information cannot be gathered from routine anatomic MR imaging.     

MR evaluation of spinal dermal sinus tracts in children

The MR studies of seven pediatric patients with surgically proved spinal dorsal dermal sinuses were reviewed retrospectively. Five of the seven had associated congenital tumors (three epidermoids, two dermoids). The subcutaneous portions of the spinal tracts and intramedullary portions of tumor were easily identified with the use of standard spin-echo techniques. However, except for limited areas where they were lined by fat, the intraspinal portions of the dermal sinuses were poorly seen. Moreover, diffuse subarachnoid tumor was missed in two patients. Three-dimensional Fourier transform gradient-echo acquisition using a volumetric radiofrequency pulse as a "spoiler" proved to be helpful in evaluating these abnormalities. Optimal radiologic workup of patients with dorsal dermal sinuses awaits the development of new MR imaging sequences. For now, heavily T1-weighted MR sequences should be obtained and supplemented with sonography in infants and with CT myelography in older children.     

MR physics of body MR imaging

This article reviews the major challenges of body imaging, describes the problems that arise from motion, and the many attempts at reducing this problem. Fast imaging sequences and approaches to reducing the data acquired without sacrificing image quality are described.     

Osteoarthritis and MR imaging

Although osteoarthritis (OA) is a common disease affecting millions of Americans, OA treatment is difficult to monitor because of the lack of consistent, objective disease standards. This article reviews the diagnosis and treatment of OA, with particular emphasis on the role of magnetic resonance (MR) in imaging the disease. After completing this article, readers will be able to: List the known risk factors for OA. Discuss normal and abnormal joint anatomy and physiology. Recognize OA symptoms. Describe diagnostic criteria for OA. Discuss the appearance of articular joint structures on MR. Explain the nonpharmacological and pharmacological treatment of OA. Discuss the role of MR in OA research.     

Diffusion tensor MR imaging tractography of the pyramidal tracts correlates with clinical motor function in children with congenital hemiparesis

BACKGROUND AND PURPOSE: Children with congenital hemiparesis have greater asymmetry in diffusion parameters of the pyramidal tracts compared with control subjects. We hypothesized that the asymmetry correlates with the severity of hemiparesis and that diffusion metrics would be abnormal in the affected tracts and normal in the unaffected tracts. MATERIALS AND METHODS: Fifteen patients with congenital hemiparesis and 17 age-matched control subjects were studied with diffusion tensor MR imaging tractography. Hemipareses were scored as mild, moderate, or severe. We measured tract-specific diffusion parameters (fractional anisotropy, mean, and directional diffusion coefficients) of the pyramidal tracts. We compared tract-specific parameters and asymmetry between the right and left tracts of the differing severity groups and control subjects. RESULTS: We observed many different causes of congenital hemiparesis including venous infarction, arterial infarction, and polymicrogyria. Clinical severity of hemiparesis correlated with asymmetry in fractional anisotropy (P < .0001), transverse diffusivity (P < .0001), and mean diffusivity (P < .03). With increasing severity of hemiparesis, fractional anisotropy decreased (P < .0001) and transverse diffusivity (P < .0001) and mean diffusivity (P < .02) increased in the affected pyramidal tract compared with controls. Diffusion metrics in the unaffected tract were similar to those in the control subjects. CONCLUSION: Asymmetry in fractional anisotropy, transverse diffusivity, and mean diffusivity, as well as the degree of abnormality in the actual values of the affected pyramidal tracts themselves, correlates with the severity of motor dysfunction in infants and children with congenital hemiparesis from different causes. This suggests that abnormalities detected by diffusion tensor MR imaging tractography in the affected pyramidal tract are related to the functional ability of the affected pyramidal tract, regardless of the etiology of motor dysfunction.     

MR urography: evaluation of different techniques in non-dilated tracts

OBJECTIVE: To assess the effectiveness of different MRI sequences for the visualisation of the different components of the non-dilated urinary tract. METHOD: 20 asymptomatic individuals were prospectively evaluated using 2 different heavily T2 weighted sequences, and after the injection of 2 different doses of gadolinium (Gd-DTPA). Images were independently scored. RESULTS: The low dose Gd-DTPA enhanced MR urography (MRU) sequence was the best overall sequence for the visualisation of both the pelvicalyceal systems and ureters. The combination of information from the other sequences was additive. CONCLUSIONS: Combined use of heavily T2 weighted and Gd-DTPA enhanced MRU produces diagnostic images and does not require pre-imaging preparation other than oral hydration.