The clue is in the kidneys: greater renal contrast medium accumulation on ipsilateral side down CT myelogram after lateral decubitus digital subtraction myelogram as a predictor of laterality of cerebrospinal fluid leak.

AIM: To assess the potential correlation of the laterality of a cerebrospinal fluid (CSF)-venous fistula with the laterality of decubitus computed tomography (CT) myelogram (post decubitus digital subtraction myelogram) based on which side demonstrated more renal contrast medium excretion. MATERIALS AND METHODS: Patients with CSF-venous fistulas diagnosed at lateral decubitus digital subtraction myelograms were reviewed retrospectively. Patients who did not have CT myelogram following one or both left and right lateral decubitus digital subtraction myelograms were excluded. Two neuroradiologists independently interpreted the CT myelogram for the presence or absence of renal contrast, and whether subjectively more renal contrast medium was visualised on the left or right lateral decubitus CT myelogram. RESULTS: Renal contrast medium was seen in lateral decubitus CT myelograms in 28 of 30 (93.3%) patients with CSF-venous fistulas. Having more renal contrast medium in right lateral decubitus CT myelogram was 73.9% sensitive and 71.4% specific for the diagnosis of a right-sided CSF-venous fistula, whereas having more renal contrast medium in the left lateral decubitus CT myelogram was 71.4% sensitive and 82.6% specific for a left-sided CSF-venous fistula (p=0.02). CONCLUSION: When the CSF-venous fistula lies on the dependent side of a decubitus CT myelogram performed after decubitus digital subtraction myelogram, relatively more renal contrast medium is visualised compared to when the fistula lies on the non-dependent side.

Utility of Photon-Counting Detector CT Myelography for the Detection of CSF-Venous Fistulas.

CSF-venous fistulas are an increasingly recognized type of CSF leak that can be particularly challenging to detect, even with recently improved imaging techniques. Currently, most institutions use decubitus digital subtraction myelography or dynamic CT myelography to localize CSF-venous fistulas. Photon-counting detector CT is a relatively recent advancement that has many theoretical benefits, including excellent spatial resolution, high temporal resolution, and spectral imaging capabilities. We describe 6 cases of CSF-venous fistulas detected on decubitus photon-counting detector CT myelography. In 5 of these cases, the CSF-venous fistula was previously occult on decubitus digital subtraction myelography or decubitus dynamic CT myelography using an energy-integrating detector system. All 6 cases exemplify the potential benefits of photon-counting detector CT myelography in identifying CSF-venous fistulas. We suggest that further implementation of this imaging technique will likely be valuable to improve the detection of fistulas that might otherwise be missed with currently used techniques.

Fluoroscopy- and CT-Guided Gold Fiducial Marker Placement for Intraoperative Localization during Spinal Surgery: Review of 179 Cases at a Single Institution-Technique and Safety Profile.

BACKGROUND AND PURPOSE: Wrong-level spinal surgery, especially in the thoracic spine, remains a challenge for a variety of reasons related to visualization, such as osteopenia, large body habitus, severe kyphosis, radiographic misinterpretation, or anatomic variation. Preoperative fiducial marker placement performed in a dedicated imaging suite has been proposed to facilitate identification of thoracic spine vertebral levels. In this current study, we report our experience using image-guided percutaneous gold fiducial marker placement to enhance the accuracy and safety of thoracic spinal surgical procedures. MATERIALS AND METHODS: A retrospective review was performed of all fluoroscopy- or CT-guided gold fiducial markers placed at our institution between January 3, 2019, and March 16, 2022. A chart review of 179 patients was performed detailing the procedural approach and clinical information. In addition, the method of gold fiducial marker placement (fluoroscopy/CT), procedure duration, spinal level of the gold fiducial marker, radiation dose, fluoroscopy time, surgery date, and complications (including whether wrong-level surgery occurred) were recorded. RESULTS: A total of 179 patients (104 female) underwent gold fiducial marker placement. The mean age was 57 years (range, 12-96 years). Fiducial marker placement was performed by 13 different neuroradiologists. All placements were technically successful without complications. All 179 (100%) operations were performed at the correct level. Most fiducial markers (143) were placed with fluoroscopy with the most common location at T6-T8. The most common location for placement in CT was at T3 and T4. CONCLUSIONS: All operations guided with gold fiducial markers were performed at the correct level. There were no complications of fiducial marker placement.

Conebeam CT as an Adjunct to Digital Subtraction Myelography for Detection of CSF-Venous Fistulas.

Lateral decubitus digital subtraction myelography is an effective technique for precisely localizing CSF-venous fistulas, a common cause of spontaneous intracranial hypotension. However, despite an optimal imaging technique, digital subtraction myelography fails to identify some CSF-venous fistulas for a variety of reasons. Here, we describe a technique involving conebeam CT performed during intrathecal contrast injection as an adjunct to digital subtraction myelography, allowing identification of some otherwise-missed CSF-venous fistulas.

The Monro-Kellie Doctrine: A Review and Call for Revision.

The Monro-Kellie doctrine is a well-accepted principle of intracranial hemodynamics. It has undergone few consequential revisions since it was established. Its principle is straightforward: The combined volume of neuronal tissue, blood, and CSF is constant. To maintain homeostatic intracranial pressure, any increase or decrease in one of these elements leads to a reciprocal and opposite change in the others. The Monro-Kellie doctrine assumes a rigid, unadaptable calvaria. Recent studies have disproven this assumption. The skull expands and grows in response to pathologic changes in intracranial pressure. In this review, we outline what is known about calvarial changes in the setting of pressure dysregulation and suggest a revision to the Monro-Kellie doctrine that includes an adaptable skull as a fourth component.

Sacral CSF-Venous Fistulas and Potential Imaging Techniques.

This is the first study to describe CSF-venous fistulas involving the sacrum, a location that may be underrecognized on the basis of current imaging techniques. We describe a delayed decubitus flat CT myelogram technique that may be useful to identify sacral CSF-venous fistulas.

Reassessing the Carotid Artery Plaque "Rim Sign" on CTA: A New Analysis with Histopathologic Confirmation.

BACKGROUND AND PURPOSE: The CTA "rim sign" has been proposed as an imaging marker of intraplaque hemorrhage in carotid plaques. This study sought to investigate such findings using histopathologic confirmation. MATERIALS AND METHODS: Included patients had CTA neck imaging <1 year before carotid endarterectomy. On imaging, luminal stenosis and the presence of adventitial (<2-mm peripheral) and "bulky" (≥2-mm) calcifications, total plaque thickness, soft-tissue plaque thickness, calcification thickness, and the presence of ulcerations were assessed. The rim sign was defined as the presence of adventitial calcifications with internal soft-tissue plaque of ≥2 mm in maximum thickness. Carotid endarterectomy specimens were assessed for both the presence and the proportional makeup of lipid material, intraplaque hemorrhage, and calcification. RESULTS: Sixty-seven patients were included. Twenty-three (34.3%) were women; the average age was 70.4 years. Thirty-eight (57.7%) plaques had a rim sign on imaging, with strong interobserver agreement (κ = 0.85). A lipid core was present in 64 (95.5%) plaques (average, 22.2% proportion of plaque composition); intraplaque hemorrhage was present in 52 (77.6%), making up, on average, 13.7% of the plaque composition. The rim sign was not associated with the presence of intraplaque hemorrhage (P = .11); however, it was associated with a greater proportion of intraplaque hemorrhage in a plaque (P = .049). The sensitivity and specificity of the rim sign for intraplaque hemorrhage were 61.5% and 60.0%, respectively. CONCLUSIONS: The rim sign is not associated with the presence of intraplaque hemorrhage on histology. However, it is associated with a higher proportion of hemorrhage within a plaque and therefore may be a biomarker of more severe intraplaque hemorrhage, if present.

Percutaneous CT-Guided Core Needle Biopsies of Head and Neck Masses: Review of 184 Cases at a Single Academic Institution, Common and Special Techniques, Diagnostic Yield, and Safety.

BACKGROUND AND PURPOSE: Percutaneous CT-guided core needle biopsies of head and neck lesions can be safely performed with vigilant planning. This largest-to-date single-center retrospective study evaluates multiple approaches with consideration of special techniques and examines the histopathologic yield. MATERIALS AND METHODS: Retrospective review of CT-guided core biopsies of head and neck lesions from January 1, 2010, to October 30, 2020, was performed. We recorded the following: patient demographics, sedation details, biopsy needle type and size, lesion location and size, approach, patient positioning, preprocedural intravenous contrast, proceduralists' years of experience, complications, and pathology results. RESULTS: One hundred eighty-four CT-guided core biopsies were evaluated. The initial diagnostic yield was 93% (171/184). However, of 43/184 (23%) originally "negative for malignancy" biopsies, 4 were eventually positive for malignancy via rebiopsy/excision, resulting in a 2% false-negative rate and an adjusted total diagnostic yield of 167/184 (91%). Biopsies were performed by 16 neuroradiologists with variable experience. The diagnostic yield was essentially the same: 91% (64/70) for proceduralists with ≤3 years' experience, and 90% (103/114) with >3 years' experience. The diagnostic yield was 93% (155/166) for lesions of >10 mm. The diagnostic yield per biopsy needle gauge was the following: 20 ga, 81% (13/16); 18 ga, 93% (70/75); 16 ga, 90% (64/71); and 14 ga, 91% (20/22). There were 4 asymptomatic hematomas, with none requiring intervention. CONCLUSIONS: Percutaneous CT-guided core needle biopsies are safe procedures for superficial and deep head and neck lesions with a high diagnostic yield. Careful planning and special techniques may increase the number of lesions accessible percutaneously while minimizing the risk of complications.

Imaging Review of Paraneoplastic Neurologic Syndromes.

Paraneoplastic syndromes are systemic reactions to neoplasms mediated by immunologic or hormonal mechanisms. The most well-recognized paraneoplastic neurologic syndrome, both clinically and on imaging, is limbic encephalitis. However, numerous additional clinically described syndromes affect the brain, spinal cord, and peripheral nerves. Many of these syndromes can have imaging findings that, though less well described, are important in making the correct diagnosis. Moreover, imaging in these syndromes frequently mimics more common pathology, which can be a diagnostic challenge for radiologists. Our goal is to review the imaging findings of paraneoplastic neurologic syndromes, including less well-known entities and atypical presentations of common entities. Specifically, we discuss limbic encephalitis, paraneoplastic cerebellar degeneration, paraneoplastic brain stem encephalitis, cranial neuropathy, myelitis, and polyneuropathy. We also demonstrate common diagnostic pitfalls that can be encountered when imaging these patients.

Imaging Findings Related to the Valsalva Maneuver in Head and Neck Radiology.

Forced exhalation against a closed glottis, known as the Valsalva maneuver, is an important clinical diagnostic and therapeutic tool due to its physiologic effects. Several unique conditions and anatomic changes can occur with repetitive or acute changes in pressure from the Valsalva maneuver. We will discuss and review various pertinent head and neck imaging cases with findings resulting from induced pressure gradients, including the Valsalva maneuver. Additionally, we will demonstrate the diagnostic utility of the Valsalva maneuver in head and neck radiology.