Faculty Bibliography

Purpose: To investigate the integrity of the default-mode network (DMN) by using independent component analysis (ICA) methods in patients shortly after mild traumatic brain injury (MTBI) and healthy control subjects, and to correlate DMN connectivity changes with neurocognitive tests and clinical symptoms. Materials and Methods: This study was approved by the institutional review board and complied with HIPAA regulations. Twenty-three patients with MTBI who had posttraumatic symptoms shortly after injury (<2 months) and 18 age-matched healthy control subjects were included in this study. Resting-state functional magnetic resonance imaging was performed at 3 T to characterize the DMN by using ICA methods, including a single-participant ICA on the basis of a comprehensive template from core seeds in the posterior cingulate cortex (PCC) and medial prefrontal cortex (MPFC) nodes. ICA z images of DMN components were compared between the two groups and correlated with neurocognitive tests and clinical performance in patients by using Pearson and Spearman rank correlation. Results: When compared with the control subjects, there was significantly reduced connectivity in the PCC and parietal regions and increased frontal connectivity around the MPFC in patients with MTBI (P < .01). These frontoposterior opposing changes within the DMN were significantly correlated (r = -0.44, P = .03). The reduced posterior connectivity correlated positively with neurocognitive dysfunction (eg, cognitive flexibility), while the increased frontal connectivity correlated negatively with posttraumatic symptoms (ie, depression, anxiety, fatigue, and postconcussion syndrome). Conclusion: These results showed abnormal DMN connectivity patterns in patients with MTBI, which may provide insight into how neuronal communication and information integration are disrupted among DMN key structures after mild head injury. (c) RSNA, 2012.

AQP4 water channels are thought to be the target of autoimmune attack in neuromyelitis optica-spectrum disorders (NMOsd). AQP4 are highly expressed on ventricular ependyma. The objective of this study was to describe a novel pattern of linear, 'pencil-thin' enhancement of ventricular ependyma in NMOsd. We report two NMOsd patients with pencil-thin ependymal enhancement along the frontal and occipital horns of lateral ventricles. Differential diagnosis of ependymal enhancement should include NMOsd alongside with infectious and neoplastic etiologies. Pencil-thin ependymal enhancement may be a helpful radiological marker of NMOsd that can be used to differentiate this condition from multiple sclerosis.

BACKGROUND AND PURPOSE: There is no standardized curriculum currently available at most institutions for establishing procedural competency in trainees performing cervicocerebral angiography. The purpose of this study was to evaluate a simple learning program to supplement the teaching of basic cervicocerebral angiography. MATERIALS AND METHODS: An 11-session interactive curriculum was implemented covering anatomic, clinical, and radiographic topics for the novice cervicocerebral angiographer. The target learner was the neuroradiology fellow. Data were gathered regarding fellow comfort level on topics relating to cervicocerebral angiography by using a 5-point Likert scale. Improvement in scores on knowledge-based questions after completion of the curriculum was calculated (McNemar test). Trainee-perceived utility of the program was also recorded by using a 5-point Likert scale. Focus sessions were held at the completion of the curriculum to gather feedback regarding the strengths and weaknesses of the program from participants. RESULTS: Ten subjects were enrolled in this pilot study for 3 years. Topics where participants reported a poor initial comfort level (4 or higher) included selection of injection rates and volumes and reformation of reverse-curve catheters. Trainees demonstrated a statistically significant change in the distribution of scores of 29.3% (49.4%-78.7% correct response rate, P < .0001). The average perceived utility was 1.5 (1 = most useful, 5 = least useful). CONCLUSIONS: This simple learning program was a useful adjunct to the training of fellows in diagnostic cervicocerebral angiography, resulting in quantitative improvements in knowledge.

OBJECTIVE: Perfusion CT is being increasingly used as a diagnostic tool for the evaluation of acute ischemic stroke. It can be performed rapidly and aids in the detection of salvageable tissue (penumbra) from the unsalvageable core infarct. The purpose of this article is to provide an overview of the imaging technique, interpretation pearls, and common pitfalls encountered in perfusion CT of the brain. CONCLUSION: Perfusion CT has proven to be a valuable tool in the diagnosis of acute ischemic stroke. The knowledge provided by these cases will allow the reader not only to confidently identify the presence of acute ischemic stroke, but also to recognize the common pitfalls and limitations of perfusion CT in this setting.

PURPOSE: To compare neoplastic and nonneoplastic disease in the anterior extradural space (AES) with regard to the contour of the disease and the tethering of the central septum, as seen on axial magnetic resonance (MR) images. MATERIALS AND METHODS: In this institutional review board-approved HIPAA-compliant study, the data of patients who had AES disease determined at MR imaging and underwent diagnostic biopsy were studied. Two blinded observers reviewed the MR images and assigned the patients to one of two groups on the basis of the contour of AES disease: those with a centrally convex disease contour posteriorly and those whose disease contour was tethered in the midline to the posterior aspect of the vertebral body. Biopsy results served as the standard of reference. The two-tailed Fisher exact test, the Breslow-Day test, and kappa statistics were used to compare groups. The sensitivity, specificity, and accuracy of the midline tethered contour of AES disease for the detection of neoplasm were calculated. RESULTS: The data of 32 patients (16 men, 16 women; mean age, 68 years) were studied. Seventeen patients had malignant epidural disease. Fifteen patients had nonneoplastic epidural disease: Six patients had hematomas, and nine had abscesses. A greater proportion of AES neoplasms (13 [76%] and 14 [82%] of 17 lesions for observers 1 and 2, respectively) than nonneoplastic AES lesions (four [27%] and three [20%] of 15 lesions for observers 1 and 2, respectively) demonstrated midline tethering of the central septum. For observers 1 and 2, a unilobed or bilobed appearance of AES disease had sensitivities of 76% (13 of 17 lesions) and 82% (14 of 17 lesions), respectively; specificities of 73% (11 of 15 lesions) and 80% (12 of 15 lesions), respectively; and accuracies of 75% (24 of 32 lesions) and 81% (26 of 32 lesions), respectively, for the detection of neoplasm. The mean kappa value for interobserver variability was 0.62 (95% confidence interval: 0.35, 0.90). CONCLUSION: AES disease preserving the midline tethering of the central septum is more common with neoplastic disease than with infections or hematomas.

OBJECTIVE: Dural metastases and meningiomas are extraaxial lesions that may be difficult to distinguish using conventional imaging methods. This distinction, however, is clinically important. Perfusion MRI may play a role in preoperative assessment. The aim of this study was to evaluate the utility of perfusion parameters in differentiating between these two entities. In particular, we evaluated two new metrics that reflect the first-pass wash-in characteristics of perfusion. MATERIALS AND METHODS: Patients with intracranial extraaxial masses who underwent perfusion MRI were included. Region-of-interest analysis was performed and several perfusion metrics were calculated including relative cerebral blood volume (rCBV), mean transit time and time to peak (TTP) enhancement from initial bolus enhancement (T0), calculated as TTP-T(0). Two new metrics characterizing first pass wash-in enhancement were also measured: relative wash-in time and wash-in slope. Lesions were divided into two groups: meningioma and metastasis. Comparisons between the two groups were made using Wilcoxon rank sum and Fisher exact tests. RESULTS: Twenty lesions were studied (12 meningioma and 8 metastases). Compared with meningiomas, relative wash-in time was statistically lower in metastases (p < 0.05). No other statistically significant differences were observed. Specifically, there was no difference between the two study groups in rCBV. CONCLUSION: First-pass wash-in characteristics of dural lesions may be useful for evaluating and characterizing lesions. In particular, a metric describing the wash-in phase of perfusion-that is, relative wash-in time-was found to be lower in metastases compared with meningiomas. Contrary to a prior report, we found rCBV to be limited in the evaluation of extraaxial lesions.

A case of Whipple's disease with development of antibiotic resistance is reported. The patient's symptomatology correlated with evolution of diffusion abnormality rather than with lesion enhancement. The lesion demonstrated no hyperperfusion, moderately elevated choline, and decreased N-acetylaspartate. Conventional magnetic resonance (MR) imaging findings of central nervous system Whipple's disease are nonspecific and may mimic neoplasm. MR perfusion and spectroscopy findings are reported, which may assist in diagnosis. Change in diffusion restriction appears to be a potential imaging indicator of clinical progression and response to therapy

OBJECTIVE: Diffusion tensor imaging (DTI) allows in vivo delineation of brainstem white matter tracts. The purpose of this study was to determine whether or not abnormalities of DTI metrics and fiber tractography correlate with neurological deficits and clinical status in patients with primary posterior fossa tumors. METHODS: A review of patients with primary posterior fossa tumors who underwent magnetic resonance imaging with DTI was performed. Patients were stratified by tumor type (well-circumscribed or infiltrating lesions). Fractional anisotropy (FA) color maps were used to localize the corticospinal tracts within the brainstem. FA, mean diffusivity, and eigenvalues were measured. Tractography was performed. Correlations between DTI metrics and clinical status and between DTI metrics and neurological examination findings were assessed within each patient group using Bonferroni correction for multiple comparisons. Comparisons of DTI metrics were also made between patient groups (infiltrating lesions versus well-circumscribed lesions). RESULTS: Thirty patients were studied (mean age, 14.1 yr; 16 male, 14 female). Eighteen patients had infiltrating lesions and 12 had well-circumscribed lesions. Twelve patients (four well-circumscribed and eight infiltrating) demonstrated motor weakness on physical examination (four right, three left, five bilateral). Patients with well-circumscribed lesions and weakness had higher mean diffusivity and lower FA in the contralateral corticospinal tract (P < 0.05). No such association was seen in patients with infiltrating tumors. In 102 total patient-years of follow-up (average follow-up period, 4.2 yr), 17 patients (six well-circumscribed and 11 infiltrating lesions) demonstrated complete response or stable disease and six patients (three well-circumscribed and three infiltrating lesions) demonstrated progressive disease or death. No differences were seen in terms of DTI metrics between patients with infiltrating lesions and those with well-circumscribed lesions. Patients with well-circumscribed tumors and a bad outcome had significantly lower transverse eigenvalue measures in the corticospinal tracts compared with those with a more favorable clinical status (P < 0.05). CONCLUSION: In patients with well-circumscribed primary posterior fossa masses, higher mean diffusivity and lower FA in the brainstem corticospinal tract are associated with contralateral motor deficits; lower transverse eigenvalue may be observed with an unfavorable clinical outcome