John D. Port

A meta-analysis of functional neuroimaging in obsessive-compulsive disorder.

Recent neurobiological models of obsessive-compulsive disorder (OCD) posit that a dysfunction in orbitofrontal-subcortical circuitry underlies the etiology of this disorder. Much of the empirical support for these theories comes from studies using neuroimaging techniques to compare brain activity in OCD patients with that in non-OCD controls. Qualitative reviews of this literature implicate the orbitofrontal cortex, caudate nuclei, and thalamus. In this study, a meta-analysis was conducted to summarize the results of studies using positron emission tomography (PET) and single photon emission computed tomography (SPECT) to investigate brain activity in OCD. Results suggest that differences in radiotracer uptake between patients with OCD and healthy controls have been found consistently in the orbital gyrus and the head of the caudate nucleus. No other significant differences were found. The implications of these results for theories regarding the etiology of OCD are discussed.

Incidental Findings in Imaging Research Evaluating Incidence, Benefit, and Burden

BACKGROUND Little information exists concerning the frequency and medical significance of incidental findings (IFs) in imaging research. METHODS Medical records of research participants undergoing a research imaging examination interpreted by a radiologist during January through March 2004 were reviewed, with 3-year clinical follow-up. An expert panel reviewed all IFs generating clinical action to determine medical benefit/burden on the basis of predefined criteria. The frequency of IFs that generated further clinical action was estimated by modality, body part, age, and sex, along with net medical benefit or burden. RESULTS Of 1426 research imaging examinations, 567 (39.8%) had at least 1 IF (1055 total). Risk of an IF increased significantly by age (odds ratio [OR], 1.5; 95% confidence interval, 1.4-1.7 per decade increase). Abdominopelvic computed tomography generated more IFs than other examinations (OR, 18.9 vs ultrasonography; 9.2% with subsequent clinical action), with computed tomography of the thorax and magnetic resonance imaging of the head next (OR, 11.9 and 5.9; 2.8% and 2.2% with action, respectively). Of the 567 examinations with an IF, 35 (6.2%) generated clinical action, resulting in clear medical benefit in 1.1% (6 of 567) and clear medical burden in 0.5% (3 of 567). Medical benefit/burden was usually unclear (26 of 567 [4.6%]). CONCLUSIONS Frequency of IFs in imaging research examinations varies significantly by imaging modality, body region, and age. Research imaging studies at high risk for generating IFs can be identified. Routine evaluation of research images by radiologists may result in identification of IFs in a high number of cases and subsequent clinical action to address them in a small but significant minority. Such clinical action can result in medical benefit to a small number of patients.

A magnetic resonance spectroscopy investigation of obsessive–compulsive disorder and anxiety

The aim of the current study was to use proton magnetic resonance spectroscopy (MRS) to investigate potential irregularities in neurochemical compounds in obsessive-compulsive disorder (OCD) and the extent to which these irregularities are related to state anxiety. Single voxel MRS was used to image the head of the caudate nucleus (HOC) and orbitofrontal white matter (OFWM) bilaterally in adult patients with OCD and a control group. The results indicated that patients with OCD had increased levels of a combined measure of glutamate and glutamine (Glx/Cr) and N-acetyl-l-aspartic acid (NAA/Cr) relative to creatine in the right OFWM and reduced levels of myo-inositol relative to creatine (mI/Cr) in the HOC bilaterally. Correlational analyses indicated that Glx/Cr in the OFWM was related to OCD symptoms, while mI/Cr in the HOC was related to trait and/or state anxiety. Reanalysis of the significant group differences controlling for state anxiety symptoms erased three of the four group differences. These results are discussed in context of the methodological difficulties facing this area of research.

Imaging features of copper deficiency myelopathy: a study of 25 cases

Acquired copper deficiency presents with a spastic gait and sensory ataxia. Spinal cord magnetic resonance imaging (MRI) in patients with copper deficiency myelopathy may show increased T2 signal, most commonly in the dorsal midline cervical and thoracic cord. These imaging findings may be reversible with normalization of serum copper. The clinical and imaging picture is very similar to the subacute combined degeneration seen in patients with vitamin B12 deficiency. Neuroradiologists should consider this possibility when a long segment of symmetric dorsal spinal cord T2-hyperintensity is identified.

Quantification and minimization of magnetic susceptibility artifacts on GRE images

Purpose The purpose of this work was to determine the optimal imaging parameters for minimization of metallic susceptibility artifacts during gradient echo (GRE) imaging. Method We performed GRE imaging of titanium screws in a nickel-doped agarose gel phantom, systematically varying several parameters to characterize and quantify susceptibility artifacts. Results The greatest reduction in artifact size came from using a short TE; increasing the frequency matrix and decreasing the slice thickness also contributed substantially to reducing the artifact size. Whenever possible, implanted prostheses should be aligned with the main magnetic field to minimize artifact size. Parameters with negligible effect on artifact size included bandwidth, phase encode matrix, and field of view. Conclusion Radiologists can easily adjust the above parameters in their imaging protocols to improve GRE image quality in patients with implanted metallic devices.

Decompressive craniectomy for intractable cerebral edema: Experience of a single center

Several case reports and small clinical series have reported benefits of decompressive hemicraniectomy in patients with intractable cerebral edema and early clinical herniation. Specific indications and timing for this intervention remain unclear. We present our experience with this procedure in a subset of 18 patients with massive cerebral edema refractory to medical management, treated with decompressive craniectomy over a 3-year period (1997 to 2000). Computerized tomography (CT) scans were independently analyzed by a neuroradiologist blinded to clinical outcome. Eleven male and seven female patients, ages 20 to 69 years (mean ± SEM, 46 ± 14 years), underwent hemicraniectomy for the following diagnoses: 12 hemispheric infarcts, 3 traumatic intracerebral hemorrhages/contusions, 2 nontraumatic intraparenchymal hemorrhages (ICH), and 1 subdural empyema. This population included four patients with aneurysmal subarachnoid hemorrhage (SAH). Patients were followed for a mean of 10 months. Clinical factors including age, side of lesion, preoperative herniation signs, and early surgery (<12 or <24 hours) were not significantly associated with mortality or Glasgow outcome score (GOS). Preoperative CT evidence of transtentorial herniation (present in 5/17 patients) was associated with mortality (P = 0.04), while preoperative uncal herniation (8/17 patients) was associated with poor outcome (GOS > 1) (P = 0.01). Favorable outcome (GOS > 3) occurred in six patients, three with spontaneous or traumatic focal hematomas. Of four patients with SAH, one died while the others were severely disabled (GOS 3). Seven of nine patients with malignant MCA infarctions unrelated to SAH had poor outcomes. The overall mortality was 4/18 (22%). Patients with refractory cerebral swelling secondary to focal hematomas may have better outcomes following decompressive craniectomy. Patients with preexisting SAH seem to have poor outcomes, possibly related to other neurologic comorbidities. Hemicraniectomy requires definition of proper timing. Preoperative CT findings, especially transtentorial and uncal herniation may be useful in defining when decompressive surgery should not be performed.

Update on the Use of MR for Assessment and Diagnosis of Psychiatric Diseases

The lack of quantitative objective measures of psychiatric diseases such as anxiety and depression is one reason that the causative factors of psychiatric diseases remain obscure. The fact that human behavior is complex and cannot be easily tested in laboratories or reproduced in animal models further complicates our understanding of psychiatric diseases. During the past 3 decades, several magnetic resonance (MR)-based tools such as MR morphometry, diffusion-tensor imaging, functional MR imaging, and MR spectroscopy have yielded findings that provide tangible evidence of the neurobiologic manifestations of psychiatric diseases. In this article, we summarize major MR findings of schizophrenia, bipolar disorder, anxiety disorders, and attention deficit-hyperactivity disorder as examples to illustrate the promise that MR techniques hold for not only revealing the neurobiological underpinnings of psychiatric disorders but also enhancing our understanding of healthy human behavior. However, many radiologists remain skeptical about the diagnostic value of MR in psychiatric disease. Many inconsistent, noncomparable reports in the literature contribute to this skepticism. The aims of this article are to (a) illustrate the most reported MR findings of major psychiatric disorders such as schizophrenia, mood disorders, anxiety disorders, and attention deficit-hyperactivity disorder; (b) inform radiologists of the potential roles of MR imaging in psychiatric imaging research; and (c) discuss several confounding factors in the design and interpretation of MR imaging findings in psychiatry.

Reversible leukoencephalopathy associated with re-infusion of DMSO preserved stem cells

We report a case of posterior reversible leuko- encephalopathy (PRL) following the infusion of dimethylsulfoxide (DMSO) cryopreserved autologous stem cells in the setting of myeloablative chemotherapy in a patient with recurrent Ewing’s sarcoma. Magnetic resonance (MR) imaging revealed white matter changes which resolved over the next 2 months. Bone Marrow Transplantation (2000) 26, 797–800.

Single neurons with both form/color differential responses and saccade-related responses in the nonretinotopic pulvinar of the behaving macaque monkey

The nonretinotopic portion of the macaque pulvinar complex is interconnected with the occipitoparietal and occipitotemporal transcortical visual systems where information about the location and motion of a visual object or its form and color are modulated by eye movements and attention. We recorded from single cells in and about the border of the dorsal portion of the lateral pulvinar and the adjacent medial pulvinar of awake behaving Macaca mulatta in order to determine how the properties of these two functionally dichotomous cortical systems were represented. We found a class of pulvinar neurons that responded differentially to ten different patterns or broadband wavelengths (colors). Thirty-four percent of cells tested responded to the presentation of at least one of the pattern or color stimuli. These cells often discharged to several of the patterns or colors, but responded best to only one or two of them, and 86% were found to have statistically significant pattern and/or color preferences. Pattern/color preferential cells had an average latency of 79.1 +/- 46.0 ms (range 31-186 ms), responding well before most inferotemporal cortical cell responses. Visually guided and memory-guided saccade tasks showed that 58% of pattern/color preferential cells also had saccade-related properties, e.g. directional presaccadic and postsaccadic discharges, and inhibition of activity during the saccade. In the pulvinar, the mean presacadic response latency was earlier, and the mean postsaccadic response latency was later, than those reported for parietal cortex. We also discovered that the strength of response to patterns or colors changed depending upon the behavioral setting. In comparison to trials in which the monkey fixated dead ahead during passive presentations of pattern and color stimuli, 92% of the cells showed attenuated responses to the same passive presentation of patterns and colors during fixation when these trials were interleaved with trials which also required active saccades to pattern and color targets in the periphery. We conclude that properties which represent the functionally dichotomous object and spatial visual systems are found together in single pulvinar neurons and that the responses of these cells to pattern or color stimuli are influenced by the focus of spatial attention. The pulvinar is the first structure in the brain shown to have neurons which integrate both object and spatial properties and the response latencies indicate that this information is processed before that in cortex. These results are discussed in terms of role of the pulvinar in visual attention as well as its unique role in providing both object feature and spatial location information to the inferotemporal cortex.

Measurement of human skeletal muscle oxidative capacity by 31P‐MR spectroscopy: A cross‐validation with in vitro measurements

To cross‐validate skeletal muscle oxidative capacity measured by 31P‐MR spectroscopy with in vitro measurements of oxidative capacity in mitochondria isolated from muscle biopsies of the same muscle group in 18 healthy adults.