Absent Vascular Signal on Time-of-Flight Magnetic Resonance Angiography Due to Recent Ferumoxytol Infusion.

Time-of-flight magnetic resonance angiography is used for craniocervical arterial evaluation. Absent flow-related signal may be the result of slow flow, complex flow, or focal susceptibility effects. We report a case with complete absence of flow-related signal in the intracranial and cervical vessels due to ferumoxytol infusion given 5 days before magnetic resonance angiography. Ferumoxytol is a newly approved parenteral therapy for iron-deficiency anemia in patients with renal failure and awareness of this drug-magnetic resonance imaging interaction is needed.

Computational fluid dynamic analysis of the posterior airway space after maxillomandibular advancement for obstructive sleep apnea syndrome.

PURPOSE: This study evaluated the soft tissue change of the upper airway after maxillomandibular advancement (MMA) using computational fluid dynamics. MATERIALS AND METHODS: Eight patients with obstructive sleep apnea syndrome who required MMA were recruited into this study. All participants underwent pre- and postoperative computed tomography and then MMA by a single oral and maxillofacial surgeon. Upper airway computed tomographic datasets for these 8 patients were created with high-fidelity 3-dimensional numerical models for computational fluid dynamics. The 3-dimensional models were simulated and analyzed to study how changes in airway anatomy affect the pressure effort required for normal breathing. Airway dimensions, skeletal changes, apnea-hypopnea index, and pressure effort of pre- and postoperative 3-dimensional models were compared and correlations were interpreted. RESULTS: After MMA, laminar and turbulent air flows were significantly decreased at every level of the airway. The cross-sectional areas at the soft palate and tongue base were significantly increased. CONCLUSIONS: This study showed that MMA increased airway dimensions by increasing the distance from the occipital base to the pogonion. An increase of this distance showed a significant correlation with an improvement in the apnea-hypopnea index and a decreased pressure effort of the upper airway. Decreasing the pressure effort will decrease the breathing workload. This improves the condition of obstructive sleep apnea syndrome.

Radiopaque jaw lesions: an approach to the differential diagnosis.

Radiopaque jaw lesions are frequently encountered at radiography and computed tomography, but they are usually underevaluated or underdescribed in radiology reports. A systematic approach to the evaluation of radiopaque jaw lesions is necessary to diagnose the lesion or at least provide a meaningful differential diagnosis. To evaluate a radiopaque jaw lesion, the first, most important step is to categorize the lesion according to its attenuation, its relationship to the teeth, and its location with respect to the tooth. These basic observations are essential to the evaluation of any type of jaw lesion. Once these observations have been made, it is easy to create a proper differential diagnosis. The presence of important characteristics, such as margination, a perilesional halo, bone expansion, and growth pattern, as well as whether the lesion is sclerotic, has ground-glass attenuation, or is mixed lytic and sclerotic, further narrows the differential diagnosis. It is important to note that some radiopaque jaw lesions may be entirely lucent early in their evolution. Awareness of the demographic distribution of these lesions and their associated clinical features, as well as the radiologic approach, is important to explore the "terra incognita" of radiopaque jaw lesions.

Radiation necrosis in the brain: imaging features and differentiation from tumor recurrence.

Radiation necrosis in the brain commonly occurs in three distinct clinical scenarios, namely, radiation therapy for head and neck malignancy or intracranial extraaxial tumor, stereotactic radiation therapy (including radiosurgery) for brain metastasis, and radiation therapy for primary brain tumors. Knowledge of the radiation treatment plan, amount of brain tissue included in the radiation port, type of radiation, location of the primary malignancy, and amount of time elapsed since radiation therapy is extremely important in determining whether the imaging abnormality represents radiation necrosis or recurrent tumor. Conventional magnetic resonance (MR) imaging findings of these two entities overlap considerably, and even at histopathologic analysis, tumor mixed with radiation necrosis is a common finding. Advanced imaging modalities such as diffusion tensor imaging and perfusion MR imaging (with calculation of certain specific parameters such as apparent diffusion coefficient ratios, relative peak height, and percentage of signal recovery), MR spectroscopy, and positron emission tomography can be useful in differentiating between recurrent tumor and radiation necrosis. In everyday practice, the visual assessment of diffusion-weighted and perfusion images may also be helpful by favoring one diagnosis over the other, with restricted diffusion and an elevated relative cerebral blood volume being seen much more frequently in recurrent tumor than in radiation necrosis.

An aberrant cerebellar artery originating from the internal carotid artery.

The aberrant origin of the cerebellar arteries from anterior cerebral circulation is a quite rare vascular variation. Herein, we report a 52-year-old white female with angiographically occult subarachnoid hemorrhage. Left superior and anterior inferior cerebellar arteries were not detected. An aberrant cerebellar artery was noted to arise from the left cavernous internal carotid artery and terminated in the distribution of the ipsilateral superior and anterior inferior cerebellar arteries. This variant artery might likely have resulted from an abnormal regression of fetal anterior-to-posterior circulation connections, and may represent a fetal-type cerebellar artery. A review of the anatomy and clinical significance of the variant is presented.

Imaging of petrous apex lesions: self-assessment module.

The educational objectives for this self-assessment module are for the participant to exercise, self-assess, and improve his or her understanding of the role of imaging in the evaluation of petrous apex lesions.

The oblique occipital sinus: a review of anatomy and imaging characteristics.

Variations of the dural venous sinuses may result in inaccurate imaging interpretation or complications during surgical approaches. One variation of the dural venous sinuses reported infrequently in the literature is the oblique occipital sinus. The present paper reviews this anatomy and offers illustrations of the cadaveric and imaging findings seen with this venous variation.

Clear and Consistent Imaging of Hippocampal Internal Architecture With High Resolution Multiple Image Co-registration and Averaging (HR-MICRA).

Magnetic resonance imaging of hippocampal internal architecture (HIA) at 3T is challenging. HIA is defined by layers of gray and white matter that are less than 1 mm thick in the coronal plane. To visualize HIA, conventional MRI approaches have relied on sequences with high in-plane resolution (≤0.5 mm) but comparatively thick slices (2-5 mm). However, thicker slices are prone to volume averaging effects that result in loss of HIA clarity and blurring of the borders of the hippocampal subfields in up to 61% of slices as has been reported. In this work we describe an approach to hippocampal imaging that provides consistently high HIA clarity using a commonly available sequence and post-processing techniques that is flexible and may be applicable to any MRI platform. We refer to this approach as High Resolution Multiple Image Co-registration and Averaging (HR-MICRA). This approach uses a variable flip angle turbo spin echo sequence to repeatedly acquire a whole brain T2w image volume with high resolution in three dimensions in a relatively short amount of time, and then co-register the volumes to correct for movement and average the repeated scans to improve SNR. We compared the averages of 4, 9, and 16 individual scans in 20 healthy controls using a published HIA clarity rating scale. In the body of the hippocampus, the proportion of slices with good or excellent HIA clarity was 90%, 83%, and 67% for the 16x, 9x, and 4x HR-MICRA images, respectively. Using the 4x HR-MICRA images as a baseline, the 9x HR-MICRA images were 2.6 times and 16x HR-MICRA images were 3.2 times more likely to have high HIA ratings (p < 0.001) across all hippocampal segments (head, body, and tail). The thin slices of the HR-MICRA images allow reformatting in any plane with clear visualization of hippocampal dentation in the sagittal plane. Clear and consistent visualization of HIA will allow application of this technique to future hippocampal structure research, as well as more precise manual or automated segmentation.

Tuberous sclerosis with multiple intracranial aneurysms: atypical tuberous sclerosis diagnosed in adult due to third nerve palsy.

Association between tuberous sclerosis and intracranial aneurysms is not well established and is at best suspicious. Sporadic cases of incidentally detected unruptured single, anterior circulation aneurysms have been reported in the literature in cases of typical tuberous sclerosis. We herein describe an unrecognised case of atypical tuberous sclerosis with bilateral PCom aneurysms which was diagnosed retrospectively while evaluating an unexplained intracranial hemorrhage with third nerve palsy. We intend this case would again strengthen a possible association between TS and intracranial aneurysms and lead to a systematic larger prospective/retrospective analysis.

Pneumocele of the frontal sinus producing orbital roof defect: case report and review of literature.

Type III frontal recess air cell as a cause of frontal sinus pneumocele has not been previously reported in literature. A 31-year-old woman with chronic history of sinusitis presented with pressure in the left eye on blowing the nose. Computed tomography examination of the orbits and paranasal sinuses with coronal and sagittal reformatted images showed abnormal collection of gas in the soft tissues at the superior aspect of the left orbit contiguous with the overlying left frontal sinus through a large defect in the orbital roof and a type III frontal recess air cell narrowing the left frontal recess.

Condylar jugular diverticulum.

We would like to present 6 instances of an internal jugular bulb diverticulum extending into the occipital condyle, which, to the best of our knowledge, has not been described in the English-language literature.This asymptomatic variant was detected incidentally on 6 patients. Computed tomography was performed on all 6 cases, and magnetic resonance imaging and magnetic resonance venography was performed in 2 cases. The condylar jugular diverticula presented as a well-defined defect in the occipital condyle contiguous with the jugular bulb on computed tomography. Magnetic resonance venography showed flow within the diverticulum. There was no definite relationship to a dominant transverse sinus. Recognition of this variant will help to avoid potential confusion with pathological lesions in the occipital condyle, especially on magnetic resonance imaging.

Drainage of the basal vein of Rosenthal into the confluence of sinuses.

An adult female was found to have a variation of the left basal vein of Rosenthal after presenting with complaints of headache. The vein, in this case, drained directly into the confluence of sinuses instead of the great vein of Galen. Variation of the basal vein is likely due to the embryonic development of the deep cerebral venous system as primitive structures either differentiate further or regress with age. Such changes may result in the uncommon presentation seen in this case. To our knowledge, this is the first case reported of the basal vein draining into the confluence of sinuses.

Management of intracranial aneurysm causing a third cranial nerve palsy: MRA, CTA or DSA?

The management of a patient with a suspected posterior communicating artery aneurysm is discussed with emphasis on neuroimaging including magnetic resonance angiography (MRA), computed tomography angiography (CTA) and intra-arterial digital subtraction angiography (DSA). This paper underscores the advantages and disadvantages of each neuroimaging modality, and is presented in an atlas-type format.

Intracranial Connections of the Vertebral Venous Plexus: Anatomical Study with Application to Neurosurgical and Endovascular Procedures at the Craniocervical Junction.

BACKGROUND: Descriptions of intracranial extensions of vertebral venous plexuses are lacking. OBJECTIVE: To identify vertebral venous plexuses at the craniocervical junction in cadavers and describe them. METHODS: The authors dissected 15 ink-injected, formalin-fixed, adult cadaveric heads and measured cranial extensions of the spinal venous plexuses. RESULTS: All specimens had vertebral venous plexuses at the craniocervical junction composed of multiple interwoven vessels concentrated anteriorly (anterior vertebral plexuses), posteriorly (posterior vertebral venous plexuses), and laterally (lateral vertebral venous plexuses). Veins making up the plexus tended to be largest for the anterior internal vertebral venous plexus. On 33%, a previously unnamed lateral internal vertebral venous plexus was identified that connected to the lateral marginal sinus. The anterior external vertebral venous plexus connected to the basilar venous plexus via transclival emissary veins in 13%; remaining veins connected either intracranially via small perforating branches through the anterior atlanto-occipital membrane (33%) or had no direct gross connections inside the cranium (53%). The anterior internal vertebral plexus, which traveled between layers of the posterior longitudinal ligament, connected to the anterior half of the marginal sinus in 33% and anterolateral parts of the marginal sinus in 20%. The posterior internal venous plexus connected to the posterior aspect of the marginal sinus on 80% and into the occipital sinus in 13.3%. The posterior external venous plexus connected to veins of the hypoglossal canal in 20% and into the posterior aspect of the marginal sinus in 13.3%. CONCLUSION: Knowledge of these connections is useful to neurosurgeons and interventional radiologists.

Imaging of Inflammatory Disorders of Salivary Glands.

Sialadenitis is among the most common conditions that affect the salivary glands. Inflammation of the salivary glands occurs as the end result of a variety of pathologic conditions, including infectious, autoimmune, and idiopathic causes. Clinically, inflammation of the salivary gland causes pain and localized swelling. The presentation may be acute or chronic, and can be recurrent. Because there is significant overlap of underlying disease mechanisms and clinical presentations, radiologic evaluation often plays a significant role in evaluation. This article is a brief review of sialadenitis, including disease mechanisms, causes, and the practical imaging of the salivary glands.

Hippocampal dentation: Structural variation and its association with episodic memory in healthy adults.

While the hippocampus has long been identified as a structure integral to memory, the relationship between morphology and function has yet to be fully explained. We present an analysis of hippocampal dentation, a morphological feature previously unexplored in regard to its relationship with episodic memory. "Hippocampal dentation" in this case refers to surface convolutions, primarily present in the CA1/subiculum on the inferior aspect of the hippocampus. Hippocampal dentation was visualized using ultra-high resolution structural MRI and evaluated using a novel visual rating scale. The degree of hippocampal dentation was found to vary considerably across individuals, and was positively associated with verbal memory recall and visual memory recognition in a sample of 22 healthy adults. This study is the first to characterize the variation in hippocampal dentation in a healthy cohort and to demonstrate its association with aspects of episodic memory.

Late-Onset Cerebral Toxoplasmosis After Allogeneic Hematopoietic Stem Cell Transplantation.

BACKGROUND Toxoplasmosis is an uncommon but potentially fatal complication following allogeneic hematopoietic stem cell transplantation (HCT). Post-transplant toxoplasmosis is often a reactivation of prior infection and typically occurs within the first 6 months of transplant. Herein, we report that cerebral toxoplasmosis may occur 22 months after allogeneic hematopoietic stem cell transplantation. CASE REPORT We describe a case of cerebral toxoplasmosis that occurred 22 months after an allogeneic HCT while the patient was on aerosolized pentamidine for Pneumocystis jiroveci pneumonia (PCP) prophylaxis. The disease was only diagnosed after brain biopsy because of atypical MRI appearance of the cerebral lesion and negative Toxoplasma gondii IgG antibody test result in the cerebrospinal fluid (CSF). The patient received pyrimethamine and sulfadiazine treatment, with dramatic improvement after several months. The patient is alive 2 years after infection diagnosis, with no evidence of disease and is off Toxoplasma prophylaxis. CONCLUSIONS Cerebral toxoplasmosis can occur late after allogeneic HCT while patients are on immunosuppression therapy, with atypical features on imaging studies and negative Toxoplasma gondii IgG antibody test result in the CSF. Pre-transplant serologic screening for T. gondii antibodies in allogeneic transplant candidates is warranted. Brain biopsy can be a helpful diagnostic tool for cerebral lesions.

Enlargement of Meckel's cave in patients with spontaneous cerebrospinal fluid leaks.

BACKGROUND: Spontaneous cerebrospinal fluid (CSF) leaks have imaging findings consistent with chronically elevated intracranial pressure, such as empty sella. Meckel's cave is a CSF-filled space that houses the trigeminal ganglion at the cranial base. Our objective in this study was to evaluate "dilated" Meckel's cave as a radiologic sign in patients with elevated intracranial pressure spontaneous CSF leaks and compare the dimensions with those from a control cohort. METHODS: Meckel's cave dimensions were measured in patients with spontaneous CSF leaks and documented elevated intracranial pressure. A control group of subjects who underwent magnetic resonance imagine (MRI) scans for unrelated diagnoses were also evaluated. Subjects were included only if suitable MRIs with T2-weighted sequences in the axial plane were available. RESULTS: Sixty-three patients with spontaneous CSF leaks and 91 normal control patients were included in the study. There was significant (p < 0.05) enlargement in all measured dimensions (length and width) for the spontaneous CSF leak group. When evaluating area, spontaneous CSF leak subjects again showed significant enlargement compared with controls (0.81 ± 0.35 cm2 vs 0.52 ± 0.15 cm2 ; p < 0.0001). Average intracranial pressure measurements were 25.9 ± 9.0 cmH2 O. CONCLUSION: Patients with spontaneous CSF leaks have evidence of enlarged Meckel's caves. Evaluation of Meckel's cave dimensions should be included in preoperative imaging assessment as an additional indicator of chronically elevated intracranial pressure.