Significant Temporal Evolution of Diffusion Anisotropy for Evaluating Early Response to Radiosurgery in Patients with Vestibular Schwannoma: Findings from Functional Diffusion Maps • Y.-C. Lin, C.-C. Wang, Y.-Y. Wai, Y.-L. Wan, S.-H. Ng, Y.-L. Chen, H.-L Liu, and J.-J. Wang
It has been shown that immediately after radiation or chemotherapy, brain tumors (particularly metastases) may have changes in apparent diffusion coefficient, suggesting an alteration of their cellular arrangements that may be related to a better prognosis. Here, the authors evaluated this same concept as it applies to vestibular schwannomas treated with stereotactic radiosurgery. Six patients underwent diffusion tensor and MR imaging after treatment that showed a change in tumor size did not happen until 6 months after irradiation. An initial transient decrease in mean diffusivity and a continuous decrease in fractional anisotropy were observed in all tumors. The authors concluded DTI allows early detection of therapy-induced changes in these tumors and because morphologic changes take some time to become evident, incorporating DTI in their evaluation may be useful. I think this is an interesting observation that will need to be confirmed by a larger series of patients.
Prediction of Response to Chemoradiation Therapy in Squamous Cell Carcinomas of the Head and Neck Using Dynamic Contrast-Enhanced MR Imaging • S. Kim, L.A. Loevner, H. Quon, A. Kilger, E. Sherman, G. Weinstein, A. Chalian, and H. Poptani
This study is somewhat similar to my previous choice in that it looks at the utility of a newer imaging technique (in this case, dynamic contrast-enhanced MR imaging) as it relates to the response of head and neck cancers to therapy. The authors performed DCE-MRI in 33 patients with squamous cell cancers before chemoradiation to see if the results were predictive of response. Patients with complete remission showed a significantly higher Ktrans than nonresponders, but no other parameters were found to have significant correlations. The results indicate pretreatment DCE-MRI can potentially predict response of head and neck squamous cell carcinomas to chemoradiation.
Atrophic Enlargement of CSF Volume after Subarachnoid Hemorrhage: Correlation with Neuropsychological Outcome • P. Bendel, T. Koivisto, M. Äikiä, E. Niskanen, M. Könönen, T. Hänninen, and R. Vanninen
Patients with intracranial hemorrhages will undergo subsequent and progressive atrophy of the brain. Does the atrophy correlate with neurologic and cognitive impairments seen in these patients? These investigators performed volumetric MR imaging in 75 such patients 1 year after subarachnoid hemorrhage and correlated their findings with neurocognitive examinations obtained at the same time. They found that presence of hydrocephalus, higher Hunt and Hess grade, higher Fischer grade, and focal parenchymal lesions were associated with enlarged ventricles (the type of treatment was not). They also found enlargement of CSF-containing spaces was significantly associated with neuropsychologic deficits. The fact that the volumes of gray matter were diminished implies the enlargement of the CSF-containing spaces was due to atrophy of the brain.
In Vivo Proton MR Spectroscopy Evaluation of Pyogenic Brain Abscesses: A Report of 194 Cases • D. Pal, A. Bhattacharyya, M. Husain, K.N. Prasad, C.M. Pandey, and R.K. Gupta
Although most of us are familiar with the utility of MR spectroscopy in the evaluation of brain abscess and its findings, I have included this article because of its very large number of cases. The authors retrospectively re-evaluated MRS studies obtained at 1.5T in 194 patients with proven pyogenic brain abscesses. Amino acids were observed in 80% of abscesses. Obligate anaerobes showed lipids, lactate, and amino acids whereas most obligate aerobes show lactate and amino acids but no lipids. The authors concluded that though most pyogenic brain abscesses show amino acids, some do not, and the presence of acetate with or without succinate favors an anaerobic bacterial origin, but this finding is also not completely reliable. Because we never interpret MRS isolated from MR imaging, this study confirms MRS is useful as an adjunct when a brain abscess is suspected.
FELLOWS’ JOURNAL CLUB
Contrast-Enhancement of the Anterior Eye Segment in Patients with Retinoblastoma: Correlation between Clinical, MR Imaging, and Histopathologic Findings • P. de Graaf, P. van der Valk, A.C. Moll, S.M. Imhof, A.Y.N. Schouten-van Meeteren, D.L. Knol, and J.A. Castelijns
We have all been taught to look behind the orbit in patients with retinoblastoma because this tumor not uncommonly extends there and this finding predicts a poorer prognosis. Less well-known and less common is tumor extension into the anterior segment of the eye. The importance of this type of invasion is that it also increases the risk of metastases. The authors evaluated 42 children with RB and had all of the enucleated eyes for comparison. MR showed moderate or strong contrast enhancement of the anterior segment in nearly 70% of patients. What is the reason for this? Enhancement of the anterior eye segment is due to either simple angiogenesis or tumor invasion. However, tumor extension anteriorly seems to be present mostly with large tumors, many already extending into the optic nerve. Thus, enhancement of the anterior eye segment is not always due to tumor extension.
Value of Coronal Reformations in the CT Evaluation of Acute Head Trauma • S.C. Wei, S. Ulmer, M.H. Lev, S.R. Pomerantz, R.G. González, and J.W. Henson
This study looks at a simple issue: are coronal reformatted images obtained from routine brain CT scans useful in acute head trauma? With the ability to do this rapidly, is it something our residents and fellows (and we) should do in patients with acute head trauma? The authors included all acute brain trauma patients undergoing noncontrast head CTs studied in a 6-month period. The original images were done at 5-mm thickness and the coronal reformatted ones at 5-mm and 2.5-mm thickness. In 14% of patients with intracranial hemorrhage, the lesions were only seen in the coronal reformats. The coronal images excluded suspicious findings in a nearly equal number of patients. Overall, coronal images aided interpretation in 28% of instances and thus were considered helpful.
Familial versus Sporadic Cavernous Malformations: Differences in Developmental Venous Anomaly Association and Lesion Phenotype • T.A. Petersen, L.A. Morrison, R.M. Schrader, and B.L. Hart
We all know about the association between cerebral cavernomas and developmental venous anomalies. Most of us also know about the syndrome of multiple familial cerebral cavernomas. In this retrospective study, the authors looked at the MR imaging studies in a large series of patients with this syndrome in an attempt to determine if their cavernomas were also associated with DVAs. They evaluated more than 2200 cavernomas, most syndromic. They found nearly one-half of nonsyndromic cavernomas were accompanied by DVAs, but only 1:2176 familial ones had a DVA. Conclusion: familial cavernous malformations are almost never associated with DVAs so they may be a different disease than sporadic cavernomas.
The Safety of Dedicated-Team Catheter-Based Diagnostic Cerebral Angiography in the Era of Advanced Noninvasive Imaging • R. Thiex, A.M. Norbash, and K.U. Frerichs
More information on the common question: how safe is catheter angiography? This question is more relevant now than ever because of the high quality of noninvasive vascular studies. In this article, the safety of angiography done by dedicated individuals in a high-volume teaching hospital was assessed. The authors looked at their results in more than 1700 patients studied in a 9-year period. Specifically, they looked for those instances of patients who had suffered a transient ischemic attack or stroke presumably due to the angiogram (only 40 underwent diffusion-weighted imaging). There were no clinical strokes, 2 instances of abnormal punctate lesions on DWI, and 1 TIA. In 9 patients, non-neurologic complications occurred. They concluded that in this specific setting, complications from cerebral catheter angiography approach zero.