Alterations in cortical thickness and white matter integrity in mild cognitive impairment measured by whole-brain cortical thickness mapping and diffusion tensor imaging.

BACKGROUND AND PURPOSE: Mild cognitive impairment (MCI) is a risk factor for Alzheimer disease and can be difficult to diagnose because of the subtlety of symptoms. This study attempted to examine gray matter (GM) and white matter (WM) changes with cortical thickness analysis and diffusion tensor imaging (DTI) in patients with MCI and demographically matched comparison subjects to test these measurements as possible imaging markers for diagnosis. MATERIALS AND METHODS: Subjects with amnestic MCI (n = 10; age, 72.2 +/- 7.1 years) and normal cognition (n = 10; age, 70.1 +/- 7.7 years) underwent DTI and T1-weighted MR imaging at 3T. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), and cortical thickness were measured and compared between the MCI and control groups. We evaluated the diagnostic accuracy of 2 methods, either in combination or separately, using binary logistic regression and nonparametric statistical analyses for sensitivity, specificity, and accuracy. RESULTS: Decreased FA and increased ADC in WM regions of the frontal and temporal lobes and corpus callosum (CC) were observed in patients with MCI. Cortical thickness was decreased in GM regions of the frontal, temporal, and parietal lobes in patients with MCI. Changes in WM and cortical thickness seemed to be more pronounced in the left hemisphere compared with the right hemisphere. Furthermore, the combination of cortical thickness and DTI measurements in the left temporal areas improved the accuracy of differentiating MCI patients from control subjects compared with either measure alone. CONCLUSIONS: DTI and cortical thickness analyses may both serve as imaging markers to differentiate MCI from normal aging. Combined use of these 2 methods may improve the accuracy of MCI diagnosis.

Complications of gamma knife surgery for Parkinson disease.

BACKGROUND: Many medical centers throughout the world offer radiosurgery with the gamma knife (GK) for pallidotomy and thalamotomy as a safe and effective alternative to radiofrequency ablative surgery and deep brain stimulation for Parkinson disease (PD). The reported incidence of significant complications varies considerably, and the long-term complication rate remains unknown. DESIGN: We describe 8 patients seen during an 8-month period referred for complications of GK surgery for PD. RESULTS: Of the 8 patients, 1 died as a result of complications, including dysphagia and aspiration pneumonia. Other complications included hemiplegia, homonymous visual field deficit, hand weakness, dysarthria, hypophonia, aphasia, arm and face numbness, and pseudobulbar laughter. In all patients, lesions were significantly off target. CONCLUSIONS: The 8 patients with PD seen in referral at our center for complications of GK surgery highlight a spectrum of potential problems associated with this procedure. These include lesion accuracy and size and the delayed development of neurological complications secondary to radiation necrosis. Gamma knife surgery may have a higher complication rate than has been previously appreciated due to delayed onset and underreporting. We believe that the risk-benefit ratio of the GK will require further scrutiny when considering pallidotomy or thalamotomy in patients with PD. Physicians using this technique should carefully follow up patients postoperatively for delayed complications, and fully inform patients of these potential risks.

Diffusion-weighted MR imaging of the normal human spinal cord in vivo.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging is a robust technique for evaluation of a variety of neurologic diseases affecting the brain, and might also have applications in the spinal cord. The purpose of this study was to determine the feasibility of obtaining in vivo diffusion-weighted images of the human spinal cord, to calculate normal apparent diffusion coefficient (ADC) values, and to assess cord anisotropy. METHODS: Fifteen healthy volunteers were imaged using a multi-shot, navigator-corrected, spin-echo, echo-planar pulse sequence. Axial images of the cervical spinal cord were obtained with diffusion gradients applied along three orthogonal axes (6 b values each), and ADC values were calculated for white and gray matter. RESULTS: With the diffusion gradients perpendicular to the orientation of the white matter tracts, spinal cord white matter was hyperintense to central gray matter at all b values. This was also the case at low b values with the diffusion gradients parallel to the white matter tracts; however, at higher b values, the relative signal intensity of gray and white matter reversed. With the diffusion gradients perpendicular to spinal cord, mean ADC values ranged from 0.40 to 0.57 x 10(-3) mm2/s for white and gray matter. With the diffusion gradients parallel to the white matter tracts, calculated ADC values were significantly higher. There was a statistically significant difference between the ADCs of white versus gray matter with all three gradient directions. Strong diffusional anisotropy was observed in spinal cord white matter. CONCLUSION: Small field-of-view diffusion-weighted images of the human spinal cord can be acquired in vivo with reasonable scan times. Diffusion within spinal cord white matter is highly anisotropic.

MR diffusion imaging of the cervical spine.

Although diffusion-weighted imaging (DWI) of the brain has gained widespread clinical acceptance, DWI of the spine and spinal cord is less well known. This article briefly reviews some of the principles and concepts of diffusion imaging, including technical considerations with regard to in vivo DWI of the spine and spinal cord, and summarizes the research and clinical experience to date. With further development and refinement, DWI eventually may provide useful and important insight into a variety of diseases of the spine and spinal cord.

MR characteristics of muslin-induced optic neuropathy: report of two cases and review of the literature.

Muslin-induced optic neuropathy is a rarely reported but important cause of delayed visual loss after repair of intracranial aneurysms. Most of the previously reported cases were published before the introduction of MR imaging. We describe the clinical features and MR appearance of two cases of delayed visual loss due to "muslinoma," and compare them with the 21 cases reported in the literature.

Mucopolysaccharidosis III (Sanfilippo syndrome) type B: cranial imaging in two cases.

We present the imaging findings in two patients with mucopolysaccharidosis III (Sanfilippo syndrome) type B, both with arachnoid cysts. We postulate that the deposition of glycosaminoglycans in the meninges may impair CSF flow and explain the development of arachnoid cysts also noted in patients with other forms of mucopolysaccharidoses.

Isolated straight sinus and deep cerebral venous thrombosis: successful treatment with local infusion of urokinase. Case report.

A 23-year-old woman presented with headache and progressive lethargy. The diagnosis of isolated thrombosis of the straight sinus and of the deep cerebral venous system was established using cranial computerized tomography, magnetic resonance imaging, phase-contrast magnetic resonance venography, and cerebral angiography. Because of the rapid deterioration in the patient's clinical condition, the authors used direct transcatheter infusion of urokinase into the straight sinus. This treatment resulted in a successful outcome.

Magnetization transfer imaging of the pituitary: further insights into the nature of the posterior "bright spot".

PURPOSE: After more than a decade of investigation, the chemical nature of the posterior pituitary "bright spot" remains elusive. Speculations into the source of this high signal have included relaxation of water by phospholipid vesicles, vasopressin, paramagnetic substances, and membrane-associated proteins. We hypothesized that if the T1 shortening observed in this structure were caused by water/macromolecular interactions, this interaction could be modulated by the use of magnetization transfer (MT) saturation. METHOD: Twenty-five normal subjects were recruited over a 2 month period who were identified on routine T1 sagittal head images to have pituitary bright spots with cross-sectional area of > 2 mm2. Thin section (4 mm), T1-weighted (SE 450/20) sagittal MR images were obtained both with and without the use of an MT suppression pulse (1,000 Hz offset, 200 Hz bandwidth, peak amplitude 7.3 microT). Region-of-interest measurements were made of the posterior pituitary lobe, anterior pituitary lobe, genu of corpus callosum, and pons, with MT ratios (MTRs) calculated for each structure. RESULTS: Relatively low (and similar) MTRs were observed in both parts of the pituitary gland: anterior lobe, 12.3%; posterior lobe 10.8%. Paired t test analysis demonstrated no statistically significant difference between the MTRs of the anterior and posterior pituitary lobes (p = 0.23). Considerable suppression of signal was noted in the genu (MTR = 25.0%) and pons (MTR = 21.9%). The MTRs of both portions of the pituitary differed significantly from those of the genu and pons (p < 0.00001). CONCLUSION: The high signal of the posterior pituitary gland suppresses only slightly on MT images, having a behavior similar to that in the anterior lobe but significantly different from the rest of the brain. These findings suggest that direct water/macromolecule, water/membrane, or water/phospholipid interactions are not likely to be responsible for the appearance of the bright spot. The experimental results are more consistent with water interacting with a paramagnetic substance or low molecular weight molecule (e.g., vasopressin, neurophysins).

Optimization of parameters for the detection of cerebral aneurysms: CT angiography of a model.

PURPOSE: To optimize parameters with computed tomographic angiography for the detection of cerebral aneurysms. MATERIALS AND METHODS: Model aneurysms were placed randomly at various branch points and scanned multiple times with spiral technique. The final analysis included 63 branch points and 22 aneurysms. Each spiral scan used a different parameter combination. Collimation ranged from 1.5 to 4.0 mm and pitch ranged from 1:1 to 1.5:1. Images were constructed with shaded surface display (SSD) and maximum intensity projection (MIP) algorithms and were interpreted by three readers for the presence or absence of aneurysm. RESULTS: The receiver operating characteristic (ROC) curve area for 1.5-mm collimation was greater than those of 3- or 4-mm collimation (P < .01 and P < .001, respectively). There was no statistically significant difference in the ROC curve areas between 3- and 4-mm collimation (P = .37). There was no statistically significant decrease in ROC curve area when increasing pitch from 1:1 to 1.5:1 for any value of collimation (P = .96). For all parameter combinations the ROC curve areas for SSD images was greater than that of MIP images (P < .0001). CONCLUSION: For cerebral aneurysm detection, narrow collimation is superior to wider collimation. Mild increases in pitch do not substantially degrade diagnostic accuracy. SSD offers improved diagnostic accuracy over MIP display in this model.

Breath-holding capability of adults. Implications for spiral computed tomography, fast-acquisition magnetic resonance imaging, and angiography.

PURPOSE: The breath-holding capabilities of various groups of individuals were evaluated to develop protocols so that patients undergoing spiral computed tomography (CT), digital angiography, and breath-hold magnetic resonance imaging (MRI) can be studied successfully. METHODS: Twenty-five outpatients and 25 inpatients (all adults) were studied before undergoing body CT. Each subject was asked to hold his or her breath for as long as possible. Then each patient was asked to perform as many repetitive 12-second breath holds as possible. These data were correlated with demographic and historical information. RESULTS: The maximum breath-hold time for inpatients and those outpatients who were heavy smokers or had chronic obstructive pulmonary disease (COPD) or congestive heart failure (CHF) was 18 to 32 seconds (95% confidence interval) with a mean of 25 seconds. For all other outpatients, breath-hold time was 38 to 56 seconds (mean = 45 seconds). The 95% confidence interval for the number of 12-second breath holds for these two groups was 4 to 6 breath holds (mean = 4.9) and 6 to 7 breath holds (mean = 6.6), respectively. One inpatient could not hold his breath at all and three others were only able to hold their breath once for short periods. The sex and age of the patient had no significant effect on breath-holding performance. CONCLUSIONS: Breath-holding protocols must account for the diminished capabilities of most inpatients, and outpatients who are heavy smokers or have COPD or CHF. Most outpatients who are not heavy smokers or without COPD or CHF can achieve a single breath hold of 38 seconds, or up to six 12-second breath holds.

Methods used for liver computed tomography scanning in community radiology practice.

RATIONALE AND OBJECTIVES: A survey conducted in 1987 of mostly academic radiologists revealed that 8 of 22 (36%) respondents used bolus enhanced dynamic technique when performing computed tomography (CT) of the liver. In the current study, the authors performed a new survey of private practice radiologists that was over four times larger and had more comprehensive questions. METHODS: An 18-item questionnaire was sent to 260 members of the American College of Radiology. The answers from 98 usable responses were tallied and analyzed. RESULTS: Forty-six percent of the radiologists polled use bolus enhanced dynamic CT. Thirty-three percent still use ionic contrast, and a significantly lower iodine dose was used when nonionic contrast was chosen. CONCLUSIONS: There is general agreement in the imaging literature that dynamic enhanced scanning is the method of choice for detecting liver masses with CT. The authors speculate that cost and convenience considerations strongly influence such decisions, because less than 50% of radiologists we polled use this somewhat more expensive and time-consuming technique.

Dose-dependent responses to macrophage-targeted glucocerebrosidase in a child with Gaucher disease.

Long-term studies of a child with Gaucher disease indicated that the response to treatment with macrophage-targeted glucocerebrosidase (glucosylceramidase) is dose dependent, and that the hematologic response precedes the skeletal response.

Incidence, determinants and significance of fixed retrograde conduction in the region of the atrioventricular node. Evidence for retrograde atrioventricular nodal bypass tracts.

Of 104 consecutive patients studied in our laboratory with His bundle electrograms, atrial and ventricular pacing and the atrial and ventricular extrastimulus techniques, 18 patients in whom the existence and utilization of ventriculoatrial (V-A) bypass tracts were excluded demonstrated evidence for fixed and rapid retrograde conduction in the region of the atrioventricular node (A-V) as suggested by the following: (1) short (36 +/- 2 msec [mean +/- standard error of mean]) and constant retrograde H2-A2 intervals during retrograde refractory period studies; (2) significantly (P less than 0.025) better V-A than A-V conduction; (3) significantly (P less than 0.025) shorter retrograde functional refractory period of the V-A conducting system than of the A-V conduction system; and (4) the retrograde effective refractory period of the A=V nodal region was not attainable in any of the 18 patients. Fourteen of the 18 patients (77 percent) had a history of palpitations and 10 (51 percent) had documented paroxysmal supraventricular tachycardia; in 13 (72 percent) single echoes or sustained reentrant supraventricular tachycardia, or both, could be induced during atrial pacing or atrial premature stimulation studies, or both. During tachycardia all these 13 patients had a short (37 +/- 2.4 msec) and constant conduction time in the retrograde limb (H-Ae interval) of the reentrant circuit that was identical to the H2-A2 interval. In conclusion, fixed and rapid retrograde conduction in the region of the A-V node (1) is seen in approximately 17 percent of patients, (2) is associated with a large incidence of reentrant paroxysmal supraventricular tachycardia, and (3) suggests the presence of A-V nodal bypass tracts (intranodal or extranodal functioning in retrograde manner).