Hydrophilic polymer embolization following flow diversion of cerebral aneurysms.

Foreign body embolization is a rare and potentially under-recognized complication of neuroendovascular procedures. This complication should be considered in the differential diagnosis for clinical or radiological deterioration following neurovascular interventions. We report a case of foreign body hydrophilic coating embolization that occurred following an attempted flow diversion of an intracranial aneurysm with dramatic flare-up after repeat exposure. We also provide a literature review of all reported cases of hydrophilic polymer embolization following flow diversion procedures.

Magnetic Resonance Spectroscopy of the Head and Neck: Principles, Applications, and Challenges.

Several investigations have revealed the utility of magnetic resonance spectroscopy (MRS) as an adjunct in the evaluation of lesions of the head and neck. This technique remains a challenge in the head and neck because of its low signal-to-noise ratio and long acquisition times. In this review article, the basics of image acquisition technique and reported clinical utilities of head and neck MRS are presented.

Spontaneous Resolution of Post-Traumatic Direct Carotid-Cavernous Fistula.

Post-traumatic carotid-cavernous fistulas are due to a tear in the wall of the cavernous carotid artery, leading to shunting of blood into the cavernous sinus. These are generally high-flow fistula and rarely resolve spontaneously. Most cases require endovascular embolization. We report a case of Barrow type A carotid-cavernous fistula which resolved spontaneously.

Is bone density associated with intervertebral disc pressure in healthy and degenerated discs?

The coupling of the intervertebral disc (IVD) and vertebra as a biomechanical unit suggests that changes in the distribution of pressure within the IVD (intradiscal pressure, IDP) as a result of disc degeneration can influence the distribution of bone density within the vertebra, and vice versa. The goal of this study was to assess the correspondence between IDP and bone density in the adjacent vertebrae, with emphasis on how this correspondence differs between healthy and degenerated IVDs. Bone density of the endplates and subchondral bone in regions adjacent to the anterior and posterior annulus fibrosus (aAF and pAF, respectively) and nucleus pulposus (NP) was measured via quantitative computed tomography (QCT) in 61 spine segments (T7-9, T9-11, T10-12; 71±14years). IDP was measured in the aAF, NP, and pAF regions in 26 of the spine segments (68±16years) while they were tested in flexed (5°) or erect postures. Disc degeneration was assessed by multiple grading schemes. No correlation was found between bone density and IDP in either posture (p>0.104). Regional variations in IDP and, to a greater extent bone density, were found to change with advancing degeneration: both IDP (p=0.045) and bone density (p=0.024) decreased in the NP region relative to the aAF region. The finding of only a modest correspondence between degeneration-associated changes in IDP and bone density may arise from complexity in how IDP relates to mechanical force transmission through the endplate and from limitations of the available IVD grading schemes in estimating the mechanical behavior of the IVD.

Duplication of the Posterior Cerebral Artery and the 'True Fetal' Variant.

We present a rare case of bilateral posterior cerebral artery variant anatomy seen in a patient presenting with acute ischemic stroke. An embryological explanation of the variant configuration is discussed along with demonstrative radiologic images and a display of the vascular territory supplied.

Elastic Anisotropy of Trabecular Bone in the Elderly Human Vertebra.

Knowledge of the nature of the elastic symmetry of trabecular bone is fundamental to the study of bone adaptation and failure. Previous studies have classified human vertebral trabecular bone as orthotropic or transversely isotropic but have typically obtained samples from only selected regions of the centrum. In this study, the elastic symmetry of human vertebral trabecular bone was characterized using microfinite element (µFE) analyses performed on 1019 cubic regions of side length equal to 5 mm, obtained via thorough sampling of the centrums of 18 human L1 vertebrae (age = 81.17 ± 7.7 yr; eight males and ten females). An optimization procedure was used to find the closest orthotropic representation of the resulting stiffness tensor for each cube. The orthotropic elastic constants and orientation of the principal elastic axes were then recorded for each cube and were compared to the constants predicted from Cowin's fabric-based constitutive model (Cowin, 1985, "The Relationship Between the Elasticity Tensor and the Fabric Tensor," Mech. Mater., 4(2), pp. 137-147.) and the orientation of the principal axes of the fabric tensor, respectively. Deviations from orthotropy were quantified by the "orthotropic error" (van Rietbergen et al., 1996, "Direct Mechanics Assessment of Elastic Symmetries and Properties of Trabecular Bone Architecture," J. Biomech., 29(12), pp. 1653-1657), and deviations from transverse isotropy were determined by statistical comparison of the secondary and tertiary elastic moduli. The orthotropic error was greater than 50% for nearly half of the cubes, and the secondary and tertiary moduli differed from one another (p < 0.0001). Both the orthotropic error and the difference between secondary and tertiary moduli decreased with increasing bone volume fraction (BV/TV; p ≤ 0.007). Considering only the cubes with an orthotropic error less than 50%, only moderate correlations were observed between the fabric-based and the µFE-computed elastic moduli (R2 ≥ 0.337; p < 0.0001). These results indicate that when using a criterion of 5 mm for a representative volume element (RVE), transverse isotropy or orthotropy cannot be assumed for elderly human vertebral trabecular bone. Particularly at low values of BV/TV, this criterion does not ensure applicability of theories of continuous media. In light of the very sparse and inhomogeneous microstructure found in the specimens analyzed in this study, further work is needed to establish guidelines for selecting a RVE within the aged vertebral centrum.

Effect of specimen-specific anisotropic material properties in quantitative computed tomography-based finite element analysis of the vertebra.

Intra- and inter-specimen variations in trabecular anisotropy are often ignored in quantitative computed tomography (QCT)-based finite element (FE) models of the vertebra. The material properties are typically estimated solely from local variations in bone mineral density (BMD), and a fixed representation of elastic anisotropy ("generic anisotropy") is assumed. This study evaluated the effect of incorporating specimen-specific, trabecular anisotropy on QCT-based FE predictions of vertebral stiffness and deformation patterns. Orthotropic material properties estimated from microcomputed tomography data ("specimen-specific anisotropy"), were assigned to a large, columnar region of the L1 centrum (n = 12), and generic-anisotropic material properties were assigned to the remainder of the vertebral body. Results were compared to FE analyses in which generic-anisotropic properties were used throughout. FE analyses were also performed on only the columnar regions. For the columnar regions, the axial stiffnesses obtained from the two categories of material properties were uncorrelated with each other (p = 0.604), and the distributions of minimum principal strain were distinctly different (p ≤ 0.022). In contrast, for the whole vertebral bodies in both axial and flexural loading, the stiffnesses obtained using the two categories of material properties were highly correlated (R2 > 0.82, p < 0.001) with, and were no different (p > 0.359) from, each other. Only moderate variations in strain distributions were observed between the two categories of material properties. The contrasting results for the columns versus vertebrae indicate a large contribution of the peripheral regions of the vertebral body to the mechanical behavior of this bone. In companion analyses on the effect of the degree of anisotropy (DA), the axial stiffnesses of the trabecular column (p < 0.001) and vertebra (p = 0.007) increased with increasing DA. These findings demonstrate the need for accurate modeling of the peripheral regions of the vertebral body in analyses of the mechanical behavior of the vertebra.

Asymmetric posterior reversible encephalopathy syndrome complicating hemodynamic augmentation for subarachnoid hemorrhage-associated cerebral vasospasm.

BACKGROUND: Posterior reversible encephalopathy syndrome (PRES) is a rare complication of hemodynamic augmentation for subarachnoid hemorrhage (SAH)-associated vasospasm. The roles of hyperperfusion and hypoperfusion in the genesis of PRES remain uncertain. METHODS: Case report. RESULTS: We admitted a 35-year-old woman with Hunt & Hess grade II SAH secondary to rupture of a right middle cerebral artery (MCA) aneurysm. This was surgically clipped. Beginning on hospital day 3, she developed recurrent symptomatic vasospasm of the right MCA despite hemodynamic augmentation to a MAP as high as 130 mmHg and endovascular therapy. On hospital day 7, after 36 h of sustained MAP 120-130 mmHg, her level of arousal progressively declined, culminating in stupor and two generalized tonic-clonic seizures. MRI showed widespread, yet markedly asymmetric changes consistent with PRES largely sparing the right MCA territory. After the MAP was decreased to 85-100 mmHg, she had no further seizures. 2 days later she was fully alert with mild left hemiparesis. CONCLUSIONS: PRES is a rare complication of hemodynamic augmentation that should be considered in the differential diagnosis of delayed neurological decline in patients with aneurysmal SAH-associated cerebral vasospasm. The markedly asymmetric distribution of PRES lesions with sparing of the territory affected by vasospasm supports the hypothesis that hyperperfusion underlies the pathophysiology of this disorder.

Thunderclap headache from complicated sinusitis.

We report a case of complicated pansinusitis presenting with thunderclap headache. The patient quickly developed left ophthalmoplegia and imaging demonstrated extension of inflammation from the sphenoid sinus into the sellar region. Thunderclap headache is well known to occur from a variety of intracranial events, but complicated sinusitis presenting this way is seldom described. The patient recovered completely with appropriate treatment.

Intracranial pathology in elders with blunt head trauma.

OBJECTIVES: To examine presentations and prevalence of head injury among elder victims of blunt trauma and to estimate the prevalence of occult injuries associated with a normal level of consciousness, absence of neurologic deficit, and no evidence of significant skull fracture. METHODS: The study population consisted of all patients aged 65 years or older enrolled in the National Emergency X-Radiography Utilization Study (NEXUS) II head injury cohort. The authors assessed the prevalence and patterns of intracranial injuries among this cohort and compared the prevalence of specific presenting signs and symptoms among injured and uninjured patients. An occult injury subcohort was also constructed, and injury prevalence was examined among this group. RESULTS: A total of 1,934 elder patients were identified among the 13,326 subjects in NEXUS II (14.5%). Significant intracranial injury, defined as an injury that typically requires procedural intervention or is associated with persistent neurologic impairment or long-term disability, was found in 178 elder patients (9.2%; 95% confidence interval = 8.0% to 10.6%) as compared with 697 individuals among 11,392 younger patients (6.1%; 95% confidence interval = 5.7% to 6.6%). Focal neurologic deficits were present in 55.8% of elder patients with injury. Prevalence of specific injuries among elder and younger patients, respectively, included the following: subdural hematoma, 4.4% and 2.4%; contusion, 4.0% and 3.2%; epidural hematoma, 0.5% and 1.0%; and depressed skull fracture, 0.2% and 0.5%. Forty-two elder patients (2.2%) had an occult injury, compared with only 92 younger patients (0.8%). CONCLUSIONS: Elder patients with head trauma are at higher risk of developing a significant intracranial injury, including subdural and epidural hematoma. An occult presentation is also more common in elders.

Impact of MDCT angiography on the use of catheter angiography for the assessment of cervical arterial injury after blunt or penetrating trauma.

OBJECTIVE: The objective of our study was to assess the impact of the increasing use of MDCT angiography in the setting of blunt and penetrating neck trauma on the use of digital subtraction angiography (DSA) at our institution, a level 1 trauma center. MATERIALS AND METHODS: From January 2001 to December 2003, 57 patients were referred for CT angiography or DSA of the neck after blunt or penetrating neck trauma. All CT angiograms were acquired with a 4-MDCT scanner. The patients were divided into three groups on the basis of consecutive 12-month periods (2001, 2002, and 2003), and the initial imaging technique was recorded. The results of CT and digital subtraction angiograms were compared with operative findings and with clinical course, when available. RESULTS: In 2001, 12 patients were referred for imaging: nine patients were evaluated initially with DSA and three patients were evaluated with CT angiography and subsequently with DSA. In 2002 and 2003, 11 and 34 patients, respectively, underwent CT angiography as the initial imaging examination. During these 2 years, no patient underwent DSA as the initial diagnostic test, but five patients underwent DSA after CT angiography for the following indications: evaluation of nondiagnostic CT angiograms (n = 1), confirmation of findings when requested by the clinical service (n = 2), and catheter-guided therapy (n = 2). CONCLUSION: CT angiography has essentially replaced DSA as the study of choice for the initial evaluation of the neck vessels in the setting of blunt or penetrating trauma at our institution. CT angiography is adequate for the initial evaluation, allows appropriate triage of patients to conventional angiography or surgery for appropriate treatment, and can guide conservative management when appropriate.

Radiation necrosis versus glioma recurrence: conventional MR imaging clues to diagnosis.

BACKGROUND AND PURPOSE: Conventional MR imaging findings are considered to be inadequate for reliably distinguishing radiation necrosis from tumor recurrence in patients with glioma. Despite this belief, we hypothesized that certain conventional MR imaging findings, alone or in combination, though not definitive, may favor one or another of these diagnoses in proton beam-treated patients with new enhancing lesions on serial scanning. METHODS: MR imaging findings (axial T1-, T2-, and post-gadolinium T1-weighted) of 27 proton beam radiation therapy patients with high-grade gliomas were retrospectively reviewed. Entry criteria included new MR imaging enhancing lesions after treatment and histologically unequivocal biopsy proof of diagnosis. Readers rated corpus callosum involvement, midline spread, subependymal spread, new discrete multiple enhancing foci, a "spreading wavefront" appearance, and septum pellucidum involvement. Statistical analysis was by the Fisher exact test. RESULTS: Corpus callosum involvement in combination with multiple other findings was highly associated with progressive glioma. These combinations included involvement of the corpus callosum with multiple enhancing foci (P = .02), involvement of the corpus callosum with crossing the midline and multiple enhancing lesions (P = .04), and involvement of the corpus callosum with subependymal spread and multiple enhancing lesions (P = .01). CONCLUSIONS: In proton beam-treated patients with glioma, corpus callosum involvement, in conjunction with multiple enhancing lesions with or without crossing of the midline and subependymal spread, favors predominant glioma progression. Overall, combinations of enhancement patterns were more likely than individual patterns to distinguish necrosis from predominant tumor progression. Together with clinical and functional imaging findings, these results may assist in determining the need for biopsy.

Diffusion-weighted imaging of cerebral malaria.

Cerebral malaria occurs in 2% of patients infected by Plasmodium falciparum. Magnetic resonance imaging findings of small white matter infarcts due to cerebral malaria have been previously reported, however nonspecific. Since diffusion-weighted imaging can differentiate acute embolic infarcts from other chronic or nonspecific white matter lesions, it may aid diagnosis of this illness in patients who travel to endemic areas.

Glial tumor grading and outcome prediction using dynamic spin-echo MR susceptibility mapping compared with conventional contrast-enhanced MR: confounding effect of elevated rCBV of oligodendrogliomas [corrected].

BACKGROUND AND PURPOSE: The MR imaging characteristics of oligodendrogliomas and astrocytomas on spin-echo (SE), echo-planar relative cerebral blood volume (rCBV) maps, to our knowledge, have not previously been emphasized. We compared the specificity of SE rCBV mapping with that of conventional, contrast material-enhanced MR imaging in differentiating high- from low-grade glial tumors and in predicting survival of patients with these lesions. METHODS: Thirty consecutive adult patients with suspected gliomas underwent conventional and rCBV MR imaging. Representative maximal rCBV regions of interest were chosen from each lesion. Resultant values were normalized to those of corresponding, contralateral, uninvolved regions. These normalized CBV (nCBV) values were correlated with degree of contrast enhancement, histopathologic tumor grade, and survival. RESULTS: Twenty-two patients had astroctyomas and eight had oligodendrogliomas. With an nCBV cutoff ratio of 1.5, 13 of 13 high-grade astrocytomas were correctly categorized, three of which did not enhance. Seven of nine low-grade astrocytomas were correctly classified by their nCBV values, including one enhancing lesion. Of eight oligodendrogliomas, four of four high-grade and two of four low-grade tumors had elevated nCBV values; two low-grade oligodendrogliomas enhanced, one with nCBV greater than 1.5 and one with nCBV less than 1.5. In 19 patients with astrocytoma for whom survival data were available, correlation with survival was better for nCBV (mean survival 91 +/- 14 months for nCBV < 1.5 versus 24 +/- 27 months for nCBV > 1.5, P <.0001) than for enhancement (mean survival 61 +/- 35 months without enhancement versus 22 +/- 29 months with enhancement, P =.03). CONCLUSION: Elevated SE rCBV was a sensitive, but not specific, marker for high-grade histopathology: all high-grade tumors had nCBV foci values greater than 1.5. No tumor with nCBV region of interest less than 1.5 was high grade (100% predictive value for excluding high grade). Degree of nCBV elevation was a stronger predictor of both tumor grade and survival than was degree of enhancement. A significant proportion of low-grade glial neoplasms, most notably oligodendrogliomas, may display high rCBV foci not reflective of high-grade histopathology.

"Computed tomography-negative" intracerebral hemorrhage: case report and implications for management.

BACKGROUND: Noncontrast computed tomographic (CT) scanning of the brain is the main imaging modality recommended for the initial emergency evaluation of acute stroke. The main role of CT in this setting is to rule out intracerebral hemorrhage, especially in subjects who are potential candidates for thrombolytic therapy. OBJECTIVES AND RESULTS: We studied a patient who had symptoms suggestive of a transient ischemic attack. Although serial CT scans showed no evidence of hemorrhage, a subacute intracerebral hemorrhage was demonstrated by magnetic resonance imaging. CONCLUSIONS: This case suggests that an alternative to CT scanning should be considered in patients with acute stroke to lower the risk of an undetected intracerebral hemorrhage, especially in patients being considered for thrombolytic or anticoagulant therapy. There is evidence in the literature of other "CT-negative" cases of intracerebral hemorrhage, as well as the availability of alternative imaging techniques such as gradient echo ("susceptibility-weighted") magnetic resonance imaging sequences, which can enhance the ability of magnetic resonance imaging to detect an acute intracerebral hemorrhage.

Brain microembolism.

PURPOSE: To alert clinicians about the occurrence of a subtype of brain infarction, its suspected etiology, and its detection by specific neuroimaging techniques. METHODS: The article presents 5 nonconsecutive patients admitted to the stroke services of 2 tertiary care hospitals, who presented with acute or subacute symptoms suspicious, but at times atypical, of brain ischemia. FINDINGS: Each patient had evidence of 3 to > 20 small areas of recent brain infarction detected by diffusion-weighted imaging (DWI). When available, brain computerized tomography images were not helpful for the diagnosis of these recent infarcts. Most lesions were present on magnetic resonance imaging fluid-attenuated inversion recovery sequences, but the diffusion-weighted images allowed the determination of their acuity. Further evaluation revealed a potential source of embolism in each patient. Brain microembolism was suspected in all cases. CONCLUSION: Small and multiple areas of acute or subacute brain infarction occasionally present with clinical features atypical for brain embolism. They can be detected by magnetic resonance DWI studies.

Approach to imaging the patient with neck pain.

Neck pain is a common complaint of patients seeking care in the outpatient setting, and the cases seen vary widely in severity and cause. A careful history and physical exam, followed by appropriate imaging studies, are essential for the orderly work-up and management of neck pain in the ambulatory patient. Available imaging studies include plain film radiography, computed tomography (CT), magnetic resonance, and CT myelography. The general considerations necessary to select the appropriate imaging study are discussed for a broad spectrum of common disorders.