Absence of abnormal vessels in the subarachnoid space on conventional magnetic resonance imaging in patients with spinal dural arteriovenous fistulas.

Spinal dural arteriovenous fistula (DAVF) is an uncommon condition that can be difficult to diagnose. This often results in misdiagnosis and treatment delay. Although conventional MRI plays an important role in the initial screening for the disease, the typical MRI findings may be absent. In this article, the authors present a series of 4 cases involving patients with angiographically proven spinal DAVFs who demonstrated cord T2 prolongation on conventional MRI but without abnormal subarachnoid flow voids or enhancement. These cases suggest that spinal DAVF cannot be excluded in symptomatic patients with cord edema based on conventional MRI findings alone. Dynamic Gd-enhanced MR angiography (MRA) was successful in demonstrating abnormal spinal vasculature in all 4 cases. This limited experience provides support for the role of spinal MRA in patients with abnormal cord signal and symptoms suggestive of DAVF even when typical MRI findings of a DAVF are absent.

Unruptured Arteriovenous Malformations in the Multidetector Computed Tomography Era: Frequency of Detection and Predictable Failures.

OBJECTIVES: While hemorrhage arising from ruptured arteriovenous malformations (AVMs) is usually evident on multidetector non-contrast computed tomography (NCCT), unruptured AVMs can be below the limits of detection. We performed a retrospective review of NCCT of patients with a proven diagnosis of unruptured AVM to determine if advances in CT technology have made them more apparent and what features predict their detection. MATERIAL AND METHODS: Twenty-five NCCTs met inclusion criteria of having angiography or MR proven AVM without hemorrhage, prior surgery, or other CNS disease. Demographic variables, clinical symptoms at presentation, abnormal CT imaging findings, attenuation of the superior sagittal sinus (SSS), and Spetzler-Martin grade of each AVM were recorded. We examined the relationship between AVM detection and SSS attenuation through Kruskal-Wallis test. Exploratory serial logistic principal components analysis was performed including demographics, symptoms, and CT features in the multivariate model. RESULTS: About 80% of the NCCTs showed an abnormality while 20% were normal. All those with an identifiable abnormality showed hyperdensity (80%). Logistic regression models indicate that clustered associations between several CT features, primarily calcifications, hyperdensity, and vascular prominence significantly predicted Spetzler-Martin grade (likelihood ratio 7.7, P = 0.006). SSS attenuation was significantly lower in subjects with occult AVMs when compared to those with CT abnormalities (median 47 vs. 55 HU, P < 0.04). CONCLUSION: Abnormal hyperdensity was evident in all detectable cases (80%) and multiple CT features were predictive of a higher Spetzler-Martin AVM grade. Moreover, SSS attenuation less than 50 HU was significantly correlated with a false-negative NCCT.

Economic impact of selective use of contrast for routine follow-up MRI of patients with multiple sclerosis.

BACKGROUND AND PURPOSE: Imaging and autopsy studies show intracranial gadolinium deposition in patients who have undergone serial contrast-enhanced MRIs. This observation has raised concerns when using contrast administration in patients who receive frequent MRIs. To address this, we implemented a contrast-conditional protocol wherein gadolinium is administered only for multiple sclerosis (MS) patients with imaging evidence of new disease activity on precontrast imaging. In this study, we explore the economic impact of our new MRI protocol. METHODS: We compared scanner time and Medicare reimbursement using our contrast-conditional methodology versus that of prior protocols where all patients received gadolinium. RESULTS: For 422 patients over 4 months, the contrast-conditional protocol amounted to 60% decrease in contrast injection and savings of approximately 20% of MRI scanner time. If the extra scanner time was used for performing MS follow-up MRIs in additional patients, the contrast-conditional protocol would amount to net revenue loss of $21,707 (∼3.7%). CONCLUSIONS: Implementation of a new protocol to limit contrast in MS follow-up MRIs led to a minimal decrease in revenue when controlled for scanner time utilized and is outweighed by other benefits, including substantial decreased gadolinium administration, increased patient comfort, and increased availability of scanner time, which depending on type of studies performed could result in additional financial benefit.

Calcifications of the Medial Choroid in the Velum Interpositum: An Unrecognized Site of Physiologic Calcifications Evident on Multidetector Computed Tomography.

OBJECTIVE: In adult patients undergoing multidetector computed tomography (CT) of the brain, we observed linear calcification along the deep venous system on thin (<3 mm) sagittal reconstructions. We found no reports of this finding in the velum interpositum (VI) in the imaging literature. We performed a focused examination of the VI on 2 autopsy cases and retrospectively reviewed sagittal, thin-section reconstructions of CT scans of 273 consecutive adult patients. METHODS: On 2 routine autopsies of the brain, sampling and histologic evaluation was performed of structures within the VI. A series of 273 unselected, sequentially acquired clinical head CT scans of patients ≥60 years old were retrospectively reviewed on a three-dimensional workstation to determine the incidence of this finding and its correlation with patient age. RESULTS: In 1 of the autopsy cases, calcified choroid plexus was identified in the region of the VI; this was also visible on the patient's premorbid CT. In the series of CT scans, linear calcification of ≥9 mm along the deep venous system was evident in 24.5% of cases. The median age of the cases without calcifications was 72 years, while the median age of the cases with calcification was 82; this difference was statistically significant (χ2, P < 0.0005). CONCLUSIONS: Evidence supports that linear midline calcification along the internal cerebral veins represents age-related, physiologic calcification of extraventricular choroid plexus within the VI. Awareness of this previously unreported finding on CT will prevent mistaking these physiologic calcifications on CT for evidence of underlying venous pathology. This finding provides additional support that the midline choroid plexus lies within the VI rather than in the third ventricle and expands our understanding of the detailed anatomy of the VI.

An Initiative to Reduce Unnecessary Gadolinium-Based Contrast in Multiple Sclerosis Patients.

OBJECTIVE: Patients with multiple sclerosis (MS) routinely undergo serial contrast-enhanced MRIs. Given concerns regarding tissue deposition of gadolinium-based contrast agents (GBCAs) and evidence that enhancement of lesions is only seen in patients with new disease activity on noncontrast imaging, we set out to implement a prospective quality improvement project whereby intravenous contrast would be reserved only for patients with evidence of new disease activity on noncontrast images. METHODS: To prospectively implement such a protocol, we leveraged our in-house computer-assisted detection (CAD) software and 3-D laboratory radiology technologists to perform real-time preliminary assessments of the CAD-processed T2 fluid attenuated inversion recovery (FLAIR) noncontrast images as a basis for deciding whether to inject contrast. Before implementation, we held multidisciplinary meetings with neurology, neuroradiology, and MR technologists and distributed surveys to objectively assess opinions and obstacles to clinical implementation. We evaluated reduction in GBCA utilization and technologist performance relative to final neuroradiologist interpretations. RESULTS: During a 2-month trial period, 153 patients were imaged under the new protocol. Technologists using the CAD software were able to identify patients with new or enlarging lesions on FLAIR images with 95% accuracy and 97% negative predictive value relative to final neuroradiologist interpretations, which allowed us to avoid the use of contrast and additional imaging sequences in 87% of patients. DISCUSSION: A multidisciplinary effort to implement a quality improvement project to limit contrast in MS patients receiving follow-up MRIs allowed for improved safety and cost by targeting patients that would benefit from the use of intravenous contrast in real-time.

Utility of multislice computed tomography and reformatted images: identification of migratory intraventricular clot exacerbating obstructive hydrocephalus.

Multidetector CT has become widely available and with it the ability to rapidly create detailed reformatted images. Multiplanar images can be created depicting the anatomy in planes other than the traditional axial plane, using isotropic to near-isotropic data. It is important for both clinicians and radiologists to be aware of this capability in order to take advantage of such images. To illustrate the value of this type of imaging, the authors present a case of a third ventricular clot that migrated into the cerebral aqueduct exacerbating hydrocephalus.

Event-related functional magnetic resonance imaging of response inhibition in obsessive-compulsive disorder.

BACKGROUND: Obsessive-compulsive disorder (OCD) has been hypothesized to involve inhibitory control dysfunction related to abnormal frontal-striatal-thalamic-cortical (FSTC) circuitry. METHODS: We examined the neural substrates of response inhibition in adults with OCD using functional magnetic resonance imaging (fMRI) and a go/no-go task. Participants consisted of 12 adults with OCD and 14 healthy comparison subjects. RESULTS: During response inhibition, healthy adults showed predominantly right-hemisphere activation including the right inferior frontal gyrus, whereas the patient group showed a more diffuse, bilateral pattern of activation. Furthermore, the OCD group demonstrated less activation than the comparison group in several right-hemisphere regions during response inhibition, including inferior and medial frontal gyri. Symptom severity was inversely correlated with activation in right orbitofrontal and anterior cingulate gyri and positively correlated with thalamic and posterior cortical activations. Neither depressed mood nor medication status could account for the results. CONCLUSIONS: These findings indicate that adults with OCD demonstrate underactivation of FSTC circuitry during response inhibition. Results suggest that the thalamus and related circuitry may play a role in the expression or intensity of OCD symptoms, whereas right frontal subregions may be involved in the suppression of symptoms.

Prototypical metal/polymer hybrid cerebral aneurysm clip: in vitro testing for closing force, slippage, and computed tomography artifact. Laboratory investigation.

OBJECT: The aim of this study was to explore the possibility that a hybrid aneurysm clip with polymeric jaws bonded to a metal spring could provide mechanical properties comparable to those of an all-metal clip as well as diminished artifacts on computed tomography (CT) scanning. METHODS: Three clips were created, and Clips I and 2 were tested for mechanical properties. Clip 1 consisted of an Elgiloy spring (a cobalt-chromium-nickel alloy) bonded to carbon fiber limbs; Clip 2 consisted of an Elgiloy spring with polymethylmethacrylate (PMMA) jaws; and Clip 3 consisted of PMMA limbs identical to those in Clip 2 but bonded to a titanium spring. Custom testing equipment was set up to measure the aneurysm clip clamping forces and slippage. Clips 2 and 3 were visualized in vivo using a 64-slice CT unit, and the slices were reformatted into 3D images. RESULTS: According to the testing apparatus, Clip 2 had a similar closing force but less slippage than three similar commercial aneurysm clips. The artifact from the cobalt alloy spring on CT scanning largely offset the advantage of the nonmetal PMMA limbs, which created no artifact. The hybrid titanium/PMMA clip (Clip 3) created very little artifact on CT and allowed visualization of the phantom through the limbs. CONCLUSIONS: It is feasible to build a potentially biocompatible hybrid cerebral aneurysm clip with mechanical properties that closely resemble those of conventional metallic clips. Further testing should be directed toward establishing the reliability and biocompatibility of such a clip and optimizing the contour and surface treatments of the polymer

Optimizing computed tomography to reduce artifacts from titanium aneurysm clips: an in vitro study. Technical note.

OBJECT: At many institutions digital subtraction angiography remains the standard imaging procedure for the postoperative evaluation of patients following placement of a cerebral aneurysm clip largely because of the artifacts produced by the clip on computed tomography (CT). The authors evaluated the effect of various imaging parameters on the quality of 3D reconstructions from CT scans while imaging a phantom to optimize the CT angiograms. METHODS: Using multidetector CT scanners with submillimeter detector collimation (0.625 mm), the authors scanned a silicone phantom with attached commercial aneurysm clips. Slice thickness, reconstruction overlap, kilovolt level, milliampere level, and pitch were varied. Neuroradiologists, who were blinded to the scanning parameters, rated the reconstructions for image quality and artifact reduction. RESULTS: Images of the titanium clip using 140 kV and 380 mA with 0.625-mm overlapping reconstructed slices provided excellent 3D visualization of both the clip and the aneurysm model, even when using two adjacent clips. CONCLUSIONS: Overlapping reconstructions combined with thin-section acquisition can provide detailed images of titanium clips and surrounding tissues without the use of low-pitch values.

Perilesional Hyperintensity on T1-Weighted Images in Intra-Axial Brain Masses other than Cavernous Malformations.

BACKGROUND AND PURPOSE: Hyperintensity on T1-weighted imaging in perilesional vasogenic edema has been reported as a useful sign for differentiating cavernous malformation from other hemorrhagic intra-axial masses. In this study, we investigated the frequency of perilesional hyperintensity on T1-weighted imaging in patients with intra-axial hemorrhagic and nonhemorrhagic brain masses. METHODS: The study was performed with the approval of the institutional review board. Magnetic resonance images of 218 patients with 282 intra-axial brain masses (129 metastases, 46 gliomas, 18 primary central nervous system lymphomas [PCNSLs], 25 intracerebral hemorrhages, 50 cavernous malformations, and 14 patients with brain abscesses) were evaluated. The signal intensity in perilesional area was qualitatively evaluated on T1-weighted sequences. In addition, signal intensity in perilesional area was quantitatively measured on T1-weighted sequences and normalized to the contralateral white matter. RESULTS: Hyperintensity on T1-weighted imaging in perilesional vasogenic edema was found in 12 (9%) of 129 metastases, 8 (16%) of 50 cavernous malformations, 1 (4%) in 25 nonneoplastic intracerebral hemorrhages, and none of the patients with high-grade glioma, PCNSL, or abscess. All of the lesions with perilesional hyperintensity showed either acute or subacute hemorrhage. Pairwise comparison of qualitative hyperintensity on T1-weighted imaging demonstrated no significant difference between the groups. Perilesional hyperintensity on T1-weighted imaging showed high specificity in both metastasis and cavernous malformation groups (94%). CONCLUSION: Perilesional hyperintensity on T1-weighted imaging is not limited to cavernous malformations and frequently evident with melanoma and other hemorrhagic metastasis to the brain. In our experience, it was not seen in high-grade glioma, PCNSL, and brain abscess.

Increased brain activation during working memory in cognitively intact adults with the APOE epsilon4 allele.

OBJECTIVE: Altered patterns of brain activity during cognitive tasks have been demonstrated using functional magnetic resonance imaging (fMRI) in mild cognitive impairment and Alzheimer's disease. However, there have been few studies of adults at genetic risk for Alzheimer's disease prior to the onset of symptoms. The purpose of this study was to determine whether brain activation patterns associated with working memory differ as a function of apolipoprotein E (APOE) genotype in cognitively intact adults. METHOD: Participants were cognitively intact, healthy adults who completed genotyping, comprehensive neuropsychological testing, and structural and functional neuroimaging. Twenty-two participants had the APOE epsilon3/epsilon3 genotype, and 13 participants had the APOE epsilon3/epsilon4 genotype. The study employed an auditory verbal N-back task to probe working memory-related brain activity. RESULTS: The epsilon3/epsilon3 and epsilon3/epsilon4 groups did not differ in demographic characteristics, cognitive ability, mood, or in-scanner task performance. The epsilon3/epsilon4 group showed greater activity during working memory in the medial frontal and parietal regions bilaterally and in the right dorsolateral prefrontal cortex. There were no regions in which the epsilon3/epsilon3 group showed greater activation than the epsilon3/epsilon4 group. CONCLUSIONS: These results indicate that differences in brain activity are evident in cognitively intact individuals who are at risk for late-onset Alzheimer's disease by virtue of their APOE allele status. As neuroprotective interventions become available, early detection will increase in importance. The combination of genetic and functional neuroimaging strategies may prove useful for monitoring individuals at risk for Alzheimer's disease before the onset of cognitive symptoms.

The fornix and mammillary bodies in older adults with Alzheimer's disease, mild cognitive impairment, and cognitive complaints: a volumetric MRI study.

The fornix and mammillary bodies are important limbic structures that have not been systematically investigated in the earliest stages of preclinical dementia. The present study examined volumetric changes in the fornix and mammillary bodies and improved previously established tracing guidelines to increase reliability and provide more comprehensive measurements. Volumetric measurements were made in euthymic older adults, including 16 patients with mild Alzheimer's disease (AD), 20 patients with amnestic mild cognitive impairment (MCI), 20 individuals with cognitive complaints (CC) but normal neuropsychological test performance, and 20 demographically matched healthy controls (HC). Structural magnetic resonance imaging included a T1-weighted 1.5-mm coronal volume, acquired on a GE 1.5T LX scanner. After adjustment for total intracranial volume (ICV), significant volume reductions were observed in the fornix and mammillary bodies in patients with AD as compared with HC, CC, and MCI participants. No volume differences were seen between the HC, CC, and MCI groups. Study findings are consistent with previous research showing volume decreases of the fornix and mammillary bodies in AD, and provide new data on the relative preservation of these structures in preclinical disease stages. Results suggest that atrophy of the fornix and mammillary bodies becomes apparent at the point of conversion from MCI to AD. Longitudinal assessments are needed to delineate the time course and extent of the observed volumetric changes.

The Many Faces of Cerebral Developmental Venous Anomaly and Its Mimicks: Spectrum of Imaging Findings.

Developmental venous anomalies (DVAs) are the most common cerebral vascular malformations and are usually found incidentally on neuroimaging studies. Despite the benign nature of DVAs, occasionally, they can be symptomatic. The objective of this article is to review the spectrum of imaging findings of DVAs on conventional and advanced imaging studies. In addition, neuroimaging findings of symptomatic DVAs as well as imaging mimicks will also be described to assist in the approach to differential diagnosis.

Focal lesion in the splenium of the corpus callosum on FLAIR MR images: a common finding with aging and after brain radiation therapy.

BACKGROUND AND PURPOSE: Focal high signal intensity in the splenium of the corpus callosum on fluid-attenuated inversion-recovery (FLAIR) images is generally considered an abnormal MR finding. We identified high signal intensity in the splenium on FLAIR images in patients of advanced age with otherwise normal images and in patients who had received brain radiation therapy. We undertook an investigation to determine the frequency of this finding in these patient groups. METHODS: We reviewed the FLAIR images and medical records of 67 patients (group 1) imaged for suspicion of CNS disease and of 18 consecutive patients (group 2) with history of brain radiation therapy. All FLAIR images were evaluated for focal signal intensity abnormalities in the splenium and for diffuse white matter abnormalities. Also, autopsy specimens from two cases not part of either study group were examined. RESULTS: Among the initial 67 patients in group 1, focal high signal intensity in the splenium was associated with aging, radiation therapy, and white matter changes. Focal high signal intensity in the splenium was evident on FLAIR images in 16 of the 18 patients in the post-radiation therapy group. Histologic examination of the splenium in one autopsy case with a history of chest and neck radiation therapy demonstrated isomorphic gliosis. CONCLUSION: High signal intensity in the splenium of the corpus callosum on FLAIR images is a common finding after brain radiation therapy and can be seen with aging. The radiologist should be aware of this common finding and not mistake it for more commonly recognized causes of splenial lesions.

Mitochondrial DNA depletion in Leigh syndrome.

Leigh syndrome is a heterogenous neurologic disease characterized by seizures, developmental delay, muscle weakness, respiratory abnormalities, optic abnormalities, including atrophy and ophthalmoplegia, and progressive cranial nerve degeneration with early onset in infants and children. Diagnosis can be confirmed by characteristic pathologic findings of necrosis in the basal ganglia, thalamus, and brainstem. Severe dysfunction of mitochondrial energy metabolism is generally present and involved in the etiology of this degenerative central nervous system disease. At the molecular level, a number of point mutations have been located in mitochondrial DNA genes, including ATPase6 and tRNA(Lys) genes, and in nuclear genes encoding subunits of oxidative enzymes, such as pyruvate dehydrogenase. Biochemically these mutations are responsible for enzymatic defects in either respiratory complexes (I, IV, or V) or pyruvate dehydrogenase. We describe here the first case of Leigh syndrome with marked depletion of mitochondrial DNA levels in skeletal muscle and abnormal activities in skeletal muscle of mitochondrial respiratory complexes I, III, IV, and V.