Mary Gaskill-Shipley

Corpus Callosal Changes Associated with Hydrocephalus: A Report of Two Cases

OBJECTIVE AND IMPORTANCE Focal or diffuse corpus callosal changes can occur in patients with active hydrocephalus who undergo shunting procedures. The neural compression caused by active hydrocephalus and the conditions that follow ventricular shunting may contribute to the development of these changes. CLINICAL PRESENTATION Two patients who underwent successful shunting for hydrocephalus subsequently developed thickening and diffuse signal changes in the corpus callosum, which were revealed by magnetic resonance imaging. The abnormal signal intensity extended laterally and linearly along the callosal fiber tracts and was not associated with mass effect. These changes persisted despite clinical improvement after the shunts were implanted. INTERVENTION Detailed neuropsychological testing showed no evidence of residual cognitive impairment or any interruption of the interhemispheric transfer of information. It has been proposed that the impingement of the corpus callosum by the rigid falx may contribute to symptomatic hydrocephalus. Impingement may cause partial hemispheric disconnection, resulting from callosal axonal dysfunction. Our patients showed radiographic evidence of dramatic changes within the corpus callosum after ventricular shunting, consistent with a transcallosal demyelinating process. Patients demonstrated neither clinical nor neuropsychological evidence of callosal disconnection, even though the callosal changes persisted. In these two patients, it is reasonable to assume that the relative sparing of the splenium accounts for the lack of neuropsychological deficits. CONCLUSION Based on our findings, conservative management, rather than a stereotactic biopsy or other forms of intervention, seems reasonable when these characteristic changes of the callosum are noted by magnetic resonance imaging after a shunt for hydrocephalus has been implanted in the patient.

Cumulative Total Effective Whole-Body Radiation Dose in Critically Ill Patients

BACKGROUND Uncertainty exists about a safe dose limit to minimize radiation-induced cancer. Maximum occupational exposure is 20 mSv/y averaged over 5 years with no more than 50 mSv in any single year. Radiation exposure to the general population is less, but the average dose in the United States has doubled in the past 30 years, largely from medical radiation exposure. We hypothesized that patients in a mixed-use surgical ICU (SICU) approach or exceed this limit and that trauma patients were more likely to exceed 50 mSv because of frequent diagnostic imaging. METHODS Patients admitted into 15 predesignated SICU beds in a level I trauma center during a 30-day consecutive period were prospectively observed. Effective dose was determined using Hudas method for all radiography, CT imaging, and fluoroscopic examinations. Univariate and multivariable linear regressions were used to analyze the relationships between observed values and outcomes. RESULTS Five of 74 patients (6.8%) exceeded exposures of 50 mSv. Univariate analysis showed trauma designation, length of stay, number of CT scans, fluoroscopy minutes, and number of general radiographs were all associated with increased doses, leading to exceeding occupational exposure limits. In a multivariable analysis, only the number of CT scans and fluoroscopy minutes remained significantly associated with increased whole-body radiation dose. CONCLUSIONS Radiation levels frequently exceeded occupational exposure standards. CT imaging contributed the most exposure. Health-care providers must practice efficient stewardship of radiologic imaging in all critically ill and injured patients. Diagnostic benefit must always be weighed against the risk of cumulative radiation dose.

Critical Role of Imaging in the Neurosurgical and Radiotherapeutic Management of Brain Tumors

Abbreviations: ADC = apparent diffusion coefficient, AF = arcuate fasciculus, BOLD = blood oxygen level–dependent, CBV = cerebral blood volume, CNS = central nervous system, CST = corticospinal tract, CTV = clinical target volume, DSC = dynamic susceptibility contrast, DTI = diffusion tensor imaging, DW = diffusion-weighted, ESM = electrocortical stimulation mapping, FLAIR = fluid-attenuated inversion recovery, GBM = glioblastoma multiforme, GTV = gross tumor volume, NAA = N-acetylaspartate, TE = echo time

MR spectroscopy of intracranial tuberculomas: A singlet peak at 3.8 ppm as potential marker to differentiate them from malignant tumors

Purpose The diagnosis of intracranial tuberculomas is often challenging. Our purpose is to describe the most common metabolic patterns of tuberculomas by MR spectroscopy (MRS) with emphasis on potential specific markers. Methods Single-voxel MRS short echo time was performed in 13 cases of tuberculomas proven by histology and/or response to anti-mycobacterial therapy. For comparison MRS was also performed in 19 biopsy-proven malignant tumors (13 high-grade gliomas and six metastasis). Presence of metabolic peaks was assessed visually and categorical variables between groups were compared using chi-square. Metabolite ratios were compared using Mann-Whitney test and diagnostic accuracy of the metabolite ratios was compared using receiver-operating characteristic (ROC) curves analysis. Results Spectroscopic peaks representing lipids and glutamate/glutamine (Glx) as well as a peak at ∼3.8 ppm were well defined in 77% (10/13), 77% (10/13) and 69% (nine of 13) of tuberculomas, respectively. Lipid and Glx peaks were also present in most of the malignant lesions, 79% (15/19) and 74% (14/19) respectively. However, a peak at ∼3.8 ppm was present in only 10% (two of 19) of the tumor cases (p < 0.001). Higher Cho/Cr and mI/Cr ratios helped discriminate malignant lesions with an area under the ROC curve of 0.86 (SE: 0.078, p < 0.002, CI: 0.7–1) and 0.8 (SE: 0.1, p < 0.009, CI: 0.6–1), respectively. Threshold values between 1.7–1.9 for Cho/Cr and 0.8–0.9 for mI/Cr provided high specificity (91% for both metabolites) and adequate sensitivity (75% and 80%, respectively) for discrimination of malignant lesions. Conclusion A singlet peak at ∼3.8 ppm is present in the majority of tuberculomas and absent in most malignant tumors, potentially a marker to differentiate these lesions. The assignment of the peak is difficult from our analysis; however, guanidinoacetate (Gua) is a possibility. Higher Cho/Cr and mI/Cr ratios should favor malignant lesions over tuberculomas. The presence of lipids and Glx is non-specific.

Neoplastic and Paraneoplastic Involvement of the Spinal Cord

Neoplasia of the spinal cord, including both primary and metastatic tumors, is relatively rare, representing 4%-10% of all central nervous system tumors, and can present a diagnostic challenge to the radiologist. More than 90% of primary spinal cord neoplasms are derived from the glial cell lineage, including the 2 most common tumors ependymoma and astrocytoma. However, less common spinal cord tumors, including metastatic disease, as well as nonneoplastic and paraneoplastic processes should be considered in the diagnosis of intramedullary spinal cord lesions.

Imaging of Common Adult and Pediatric Primary Brain Tumors

p n a he primary goals of brain tumor imaging are lesion detection, localization, delineation of extent, and characerization. This information is used to formulate an approprite differential diagnosis that is extremely helpful for the eferring neuro-surgeons and the neuro-oncologists.1,2 In adition, imaging studies play a vital role in therapy planning, uch as stereotactic location for surgery or radiotherapy, and ssessing response to therapy.3 This article discusses the imaging characteristics of several ommon pediatric and adult primary central nervous system CNS) tumors. The review will focus on the initial imaging iagnostic workup and will give a useful radiological aproach based on age, localization, imaging characteristics, nd relative frequency of brain tumors. Advanced magnetic esonance (MR) techniques including spectroscopy and perusion can provide additional information of brain tumors. hese techniques will be discussed separately in this suppleent.

Early detection of postoperative residual tumor using image subtraction

The detection after surgery of residual tumor from magnetic resonance (MR) images is difficult due to the low contrast level of the images. Gadolinium-enhanced MR imaging has been found valuable in detecting residual enhancing tumor when performed within 72 hours after surgery. The patient is scanned by the MR scanner with and without infusion of gadolinium, a contrast agent. Usually, the estimation of post-operative tumor volume is done by visual comparison of the T1 MR images obtained with and without gadolinium infusion. The T1 MR images, in most cases, without contrast demonstrates areas of hyper intensities (high brightness levels), consistent with hemorrhage. These hyper intense areas often make it difficult to detect residual tumor in post contrast images. This is due to the presence of both acute hemorrhage and gadolinium enhancement which have high brightness levels in T1 MR images. Even in MR images taken within 72 hours after surgery, detection of tumor enhancement in areas of increased T1 signal produced by blood products or by postoperative changes can be difficult when performed by the naked eye. Due to these problems, the quantification of residual tumor becomes a subjective issue among neuro-radiologists. Thus to reduce errors produced by the human factor, an automated procedure to detect residual tumor is required. We have developed a technique to differentiate tumor enhancement from postoperative changes and blood products on MR imaging. The technique involves fusion of pre- and post-gadolinium MR images performed in the immediate postoperative period. Computerized slice based substraction is then done on the corresponding fused images of the two sets. The subtraction process results in a composite slice, which is examined for differences between pre- and post-gadolinium studies. The presented technique was tested on 14 cases in which MR images were obtained from brain tumor patients within 72 hours after surgery. The subtraction technique easily distinguished residual enhancing tumor from postoperative surgical changes and was simple to perform. The technique proposed and developed has given good results and will be used in clinical trial and diagnosis. Future potentials of the technique are discussed and illustrative cases presented.