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PurposeBrain herniation into arachnoid granulations (BHAG) of the dural venous sinuses is a recently described finding of uncertain etiology. The purpose of this study was to investigate the prevalence of BHAG in a cohort of patients with pulsatile tinnitus (PT) and to clarify the physiologic and clinical implications of these lesions.MethodsThe imaging and charts of consecutive PT patients were retrospectively reviewed. All patients were examined with MRI including pre- and post-contrast T1- and T2-weighted sequences. Images were reviewed separately by three blinded neuroradiologists to identify the presence of BHAG. Their location, signal intensity, size, presence of arachnoid granulation, and associated dural venous sinus stenosis were documented. Clinical records were further reviewed for idiopathic intracranial hypertension, history of prior lumbar puncture, and opening pressure.ResultsTwo hundred sixty-two consecutive PT patients over a 4-year period met inclusion criteria. PT patients with BHAG were significantly more likely to have idiopathic intracranial hypertension than PT patients without BHAG (OR 4.2, CI 1.5-12, p = 0.006). Sixteen out of 262 (6%) patients were found to have 18 BHAG. Eleven out of 16 (69%) patients had unilateral temporal or occipital lobe herniations located in the transverse sinus or the transverse-sigmoid junction. Three out of 16 (19%) patients had unilateral cerebellar herniations and 2/16 (13%) patients had bilateral BHAG.ConclusionIn patients with PT, BHAG is a prevalent MRI finding that is strongly associated with the clinical diagnosis of IIH. The pathogenesis of BHAG remains uncertain, but recognition should prompt comprehensive evaluation for IIH.

Spontaneous intracranial hypotension is an uncommon etiology of secondary headaches in children. We report a unique case of a girl with kaposiform lymphangiomatosis who developed postural headaches and imaging features of spontaneous intracranial hypotension without a spinal extradural collection. The girl underwent dynamic computed tomography myelography which revealed a cerebrospinal fluid (CSF)-lymphatic fistula related to a lymphatic malformation associated with the right T10 nerve. She underwent surgical ligation of the CSF-lymphatic fistula, resulting in resolution of the headaches. Spinal CSF-lymphatic fistulas are rare and have previously been reported in two patients with Gorham-Stout disease. The current report suggests that patients with systemic lymphatic anomalies who develop postural headaches should undergo evaluation for spontaneous intracranial hypotension and a CSF-lymphatic fistula. If discovered, surgical ligation is a potential treatment.

The clinical syndrome of intracranial hypotension refers to the symptoms caused by cerebrospinal fluid hypovolemia and is primarily characterized by postural headaches, but can be associated with a multitude of other neurological symptoms. Imaging plays a critical role in helping to establish a diagnosis of intracranial hypotension, localize the source of cerebrospinal fluid leak, and assist in directing targeted treatments. Using the best available evidence, this document provides diagnostic imaging recommendations for the workup of intracranial hypotension across various clinical presentations. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation. [ABSTRACT FROM AUTHOR]

Thoracic back pain is a common site for inflammatory, neoplastic, metabolic, infectious, and degenerative conditions, and may be associated with significant disability and morbidity. Uncomplicated acute thoracic back pain and/or radiculopathy does not typically warrant imaging. Imaging may be considered in those patients who have persistent pain despite 6 weeks of conservative treatment. Early imaging may also be warranted in patients presenting with "red flag" history or symptoms, including those with a known or suspected history of cancer, infection, immunosuppression, or trauma; in myelopathic patients; or in those with a history of prior thoracic spine fusion. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation. [ABSTRACT FROM AUTHOR]

Background: Stenosis of a dural venous sinus is the most common cause of idiopathic intracranial hypertension (IIH) and can be classified as either intrinsic or extrinsic. Intrinsic stenoses are characterized by a focal filling defect within the sinus secondary to an enlarged arachnoid granulation or fibrous septa while extrinsic stenoses tend to be long and smooth-tapered and are most commonly secondary to external compression from the adjacent brain parenchyma. Brain herniations, or encephaloceles, into arachnoid granulations in dural venous sinuses have rarely been reported in the literature in patients with IIH. We propose that dural venous sinus stenting (VSS) may be a safe and effective treatment approach in patients with an encephalocele and IIH. Methods: We retrospectively analyze three cases of patients with encephalocele who underwent VSS for treatment of medically refractory IIH at our institution. Results: One patient underwent stenting ipsilateral and two patients underwent stenting contralateral to the side of their encephaloceles. No technical related issues or complications occurred during either of the three stenting procedures. Two out of the three patients had complete resolution in their IIH-related symptoms and normalization of cerebrospinal (CSF) pressures shortly after stenting. We await clinical follow-up in the third patient. Conclusions: Our results suggest that VSS is a technically feasible and effective approach in treating patients with medically refractory IIH and encephaloceles. [ABSTRACT FROM AUTHOR]

Background and Purpose: Brachial neuritis is a monophasic condition affecting the brachial plexus and its branches, manifesting as acute shoulder and upper arm pain, followed by weakness and paresthesias. It can be triggered by antecedent events, including procedures such as surgery. Misdiagnosis and delay in diagnosis is common. Imaging is important to confirm the diagnosis of post-procedural brachial neuritis and exclude other etiologies., Materials and Methods: Clinical, electrodiagnostic, and neuroimaging features of patients with post-procedural brachial neuritis from a single quaternary care institution were identified and analyzed., Results: Six (2 female) patients were identified with median age 62 (range 49-70) years. Antecedent procedures included 4 cervical spine surgeries, 1 rotator cuff repair, and 1 central venous catheter placement. Time to symptom onset ranged from 1-day to 2-weeks. The initial symptom for 5/6 patients was severe upper extremity pain followed by weakness. All patients had electrodiagnostic tests and MR neurography consistent with brachial neuritis. MR neurogram showed plexus and/or terminal branch abnormalities with associated muscular denervation edema. The C5 or C6 root, and/or upper trunk were always involved. The most common branches affected were the suprascapular, long thoracic, and axillary nerves. Hourglass constrictions of these nerves were seen in 3/6 patients. The average time to diagnosis was 3.4 (range 1.5-5) months., Conclusions: Post-procedural brachial neuritis is an underrecognized cause of acute upper extremity pain and weakness. MR neurography can exclude iatrogenic causes and document the presence of hourglass constrictions in affected nerves. Diagnostic neuroradiologists should be aware of this clinical entity and associated neuroimaging findings., Abbreviations: HGC = hourglass constriction; EDX = electrodiagnostic; IRB = Institutional Review Board; ACDF = anterior cervical discectomy and fusion; NRS = Numerical Rating Scale; MUAP = motor unit action potential., Competing Interests: Author Praveen V. Mummaneni serves as a consultant for Depuy Synthes and Globus; receives honoraria from BK Medical, SI Bone, Brainlab, and Medtronic; receives grant funding from the NREF, ISSG, AO Spine, NIH, Pacira, PCORI, SLIP II, DoD; receives royalties from Springer Publishing and Thieme Medical Publishers; and owns Discgenics stock. The remaining authors have no disclosures., (© 2024 by American Journal of Neuroradiology.)

Advanced imaging of peripheral nerves is occupying an increasingly important role in the diagnostic workup of peripheral nerve disorders. Advances in MR neurography (MRN) and high-resolution ultrasound have addressed historical challenges in peripheral nerve imaging related to nerves' small size and nonlinear course and difficult differentiation from surrounding tissues. Modern MRN depicts neuromuscular anatomy with exquisite contrast resolution, and MRN has become the workhorse imaging modality for peripheral nerve evaluation. MRN protocols vary across institutions and are adjusted in individual patients, although they commonly include nerve-selective sequences and diffusion-tensor imaging tractography. Ultrasound offers a dynamic real-time high-resolution assessment of peripheral nerves and is widely accessible and less costly than MRN. Ultrasound has greater ability to examine peripheral nerves at the fascicular level and provides complementary information to MRN. However, ultrasound of peripheral nerves requires substantial skill and experience and is operator-dependent. The two modalities have distinct advantages and disadvantages, and the selection between these depends on the clinical context. This article provides an overview of advanced imaging techniques used for evaluation of peripheral nerves, with attention to MRN and high-resolution ultrasound. We draw on our institutional experience in performing both modalities to highlight technical considerations for optimizing examinations.

Background and Purpose: CSF-venous fistula can be diagnosed with dynamic decubitus CT myelography. This study aimed to analyze the temporal characteristics of CSF-venous fistula visualization on multiphase decubitus CT myelography., Materials and Methods: A retrospective, multisite study was conducted on patients diagnosed with CSF-venous fistula at 2 institutions between June 2017 and February 2023. Both institutions perform decubitus CT myelography with imaging immediately following injection and usually with at least 1 delayed scan. The conspicuity of CSF-venous fistula was assessed on each phase of imaging., Results: Forty-eight patients with CSF-venous fistula were analyzed. CSF-venous fistulas were better visualized on the early pass in 25/48 cases (52.1%), the delayed pass in 6/48 cases (12.5%) and were seen equally on both passes in 15/48 cases (31.3%). Of 25 cases in which the CSF-venous fistula was better visualized on the early pass, 21/25 (84%) fistulas were still at least partially visible on a delayed pass. Of 6 cases in which the CSF-venous fistula was better visualized on a delayed pass, 4/6 (67%) were partially visible on the earlier pass. Six of 48 (12.5%) CSF-venous fistulas were visible only on a single pass. Of these, 4/6 (66.7%) were seen only on the first pass, and 2/6 (33.3%) were seen only on a delayed pass. One fistula was found with one pass only, and one fistula was discovered upon contralateral decubitus imaging without a dedicated second injection., Conclusions: A dynamic decubitus CT myelography imaging protocol that includes an early and delayed phase, likely increases the sensitivity for CSF-venous fistula detection. Further studies are needed to ascertain the optimal timing and technique for CSF-venous fistula visualization on dynamic decubitus CT myelography and its impact on patient outcomes., (© 2024 by American Journal of Neuroradiology.)