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Erdheim-Chester Disease (ECD) is a rare, multisystem histiocytic disorder characterized by its variable clinical presentations. Central Nervous System (CNS) involvement is observed in approximately half of ECD patients (up to 76% in some series), and often carries a poorer prognosis. While CNS involvement may remain asymptomatic, others may experience a range of neurological symptoms, including cognitive decline, neuropsychiatric disturbances, motor deficits, cranial or peripheral neuropathies, and endocrine abnormalities.Neuroimaging findings in CNS-ECD are diverse, including neurodegeneration manifesting as cerebral or cerebellar volume loss, solitary or multifocal variably enhancing intraparenchymal lesions along the neuroaxis, meningeal infiltration, involvement of the Hypothalamo-pituitary axis, perivascular sheathing or basal ganglia lesions. Other well documented sites of involvement include the craniofacial region, orbits and spine. Awareness of these findings is relevant, not only because of the non-specific nature of these findings, but also given the high proportion of CNS involvement in ECD as well as the higher mortality associated with CNS involvement.This review provides an in-depth overview of the various manifestations of CNS involvement in ECD and their imaging features, along with a brief overview of the differential considerations which include other histiocytic and non-histiocytic processes.ABBREVIATIONS: ECD＝Erdheim-Chester Disease; RDD＝Rosai-Dorfman Disease; LCH= Langerhans cell histiocytosis., (© 2024 by American Journal of Neuroradiology.)

Abstract: A 19-year-old man presented with 3 years of gradually progressive, painless vision loss in both eyes. The ophthalmic examination showed bilateral diminished visual acuity, dyschromatopsia, and temporal optic nerve pallor. The neurological examination was consistent with a mild myelopathy with decreased pin-prick sensation starting at T6-T7 and descending through the lower extremities. Hyperreflexia was also present in the lower more than upper extremities. Infectious, inflammatory, and nutritional serum workup and cerebrospinal fluid analysis were both unrevealing. MRI of the brain and spinal cord showed abnormal T2 hyperintensity of the fornix, corpus callosum, optic nerves, and lateral columns of the cervical and thoracic spine, with diffusion restriction in the inferior-posterior corpus callosum and fornix. Biotinidase serum enzyme activity was tested and showed a decreased level of activity. Biotinidase gene testing showed a homozygous pathogenic variant, c.424C>A (p.P142T), confirming the diagnosis of biotinidase deficiency and prompting oral biotin supplementation. Three months after starting treatment, the patient's visual acuity, color vision, visual fields, and MRI spine abnormalities all improved significantly. Biotinidase deficiency is an important diagnostic consideration in patients with unexplained optic neuropathy and/or myelopathy., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 by North American Neuro-Ophthalmology Society.)

Background and Purpose: Cushing disease is typically caused by a pituitary adenoma that frequently is small and challenging to detect on conventional MR imaging. High-field-strength 7T MR imaging can leverage increased SNR and contrast-to-noise ratios compared with lower-field-strength MR imaging to help identify small pituitary lesions. We aimed to describe our institutional experience with 7T MR imaging in patients with Cushing disease and perform a review of the literature., Materials and Methods: We performed a retrospective analysis of 7T MR imaging findings in patients with pathology-proved Cushing disease from a single institution, followed by a review of the literature on 7T MR imaging for Cushing disease., Results: Our institutional experience identified Cushing adenomas in 10/13 (76.9%) patients on 7T; however, only 5/13 (38.5%) lesions were discrete. Overall, the imaging protocols used were heterogeneous in terms of contrast dose as well as type of postcontrast T1-weighted sequences (dynamic, 2D versus 3D, and type of 3D sequence). From our institutional data, specific postgadolinium T1-weighted sequences were helpful in identifying a surgical lesion as follows: dynamic contrast-enhanced, 2/7 (28.6%); 2D FSE, 4/8 (50%); 3D sampling perfection with application-optimized contrasts by using different flip angle evolution (SPACE), 5/6 (83.3%); and 3D MPRAGE, 8/11 (72.7%). The literature review identified Cushing adenomas in 31/33 (93.9%) patients on 7T., Conclusions: 7T MR imaging for pituitary lesion localization in Cushing disease is a new technique with imaging protocols that vary widely. Further comparative research is needed to identify the optimal imaging technique as well as assess the benefit of 7T over lower-field-strength MR imaging., (© 2024 by American Journal of Neuroradiology.)

Competing Interests: The authors report no conflicts of interest.

Purpose: Radiographic review of pathologies that associate with third window syndrome., Methods: Case series and literature review., Results: Eight unique third window conditions are described and illustrated, including superior, lateral, and posterior semicircular canal dehiscence; carotid-cochlear, facial-cochlear, and internal auditory canal-cochlear dehiscence, labyrinthine erosion from endolymphatic sac tumor, and enlarged vestibular aqueduct., Conclusion: The present study highlights the characteristic imaging features and symptoms to differentiate third window pathologies for expedient diagnosis and management planning., Competing Interests: Declaration of competing interest The authors report no relevant conflict of interest in submitting this article for publication., (Copyright © 2023. Published by Elsevier Inc.)

Background and Purpose: Recent introduction of photon counting detector (PCD) computed tomography (CT) scanners into clinical practice further improve CT angiography (CTA) depiction of orbital arterial vasculature compared to conventional energy integrating detector (EID) CT scanners. PCD-CTA of the orbit can provide a detailed arterial roadmap of the orbit which can de diagnostic on its own or serve as a helpful planning adjunct for both diagnostic and therapeutic catheter-based angiography of the orbit., Methods: For this review, EID and PCD-CT imaging was obtained in 28 volunteers. The volume CT dose index was closely matched. A dual-energy scanning protocol was used on EID-CT. An ultra-high-resolution (UHR) scan mode was used on PCD-CT. Images were reconstructed at 0.6 mm slice thickness using a closely matched medium-sharp standard resolution (SR) kernel. High-resolution (HR) images with the sharpest quantitative kernel were also reconstructed on PCD-CT at the thinnest slice thickness of 0.2 mm. A denoising algorithm was applied to the HR image series., Results: The imaging description of the orbital vascular anatomy presented in this work was derived from these patients' PCD-CTA images in combination with review of the literature. We found that orbital arterial anatomy is much better depicted with PCD-CTA, and this work can serve primarily as an imaging atlas of the normal orbital vascular anatomy., Conclusion: With recent advances in technology, arterial anatomy of the orbit is much better depicted with PCD-CTA as opposed to EID-CTA. Current orbital PCD-CTA technology approaches the necessary resolution threshold for reliable evaluation of central retinal artery occlusion.

Background and Purpose: Artifact from cochlear implant electrodes degrades image resolution on CT. Here, we describe the use of coregistered pre- and postoperative CT images to reduce metallic artifact from the electrodes to assess its position more accurately within the cochlear lumen., Methods: Pre- and postoperative CTs were reviewed after coregistration/overlay of both exams. Images were evaluated by two neuroradiologists for scalar location of electrodes tip (± scalar translocation), tip fold over, and angular depth of insertion., Results: Thirty-four patients were included in the final cohort. Transscalar migration was present in three (8.8%) cases (one case demonstrated tip fold over), with initial disagreement regarding transscalar migration in 1 out of 34 patients (2.9%). Agreement regarding depth of insertion was present in 31 (91.1%) cases. Five-point Likert scales were used to compare the ability to resolve the proximity of electrodes to the lateral/outer cochlear wall without and with overlay, which is a qualitative measure of artifact from the array. Likert scores showed definitive benefit of metal artifact reduction using overlayed images with an average score of 4.34., Conclusion: This study demonstrates a novel technique of using fused coregistration of pre- and postoperative CTs for the purpose of artifact reduction/electrode localization. It is anticipated that this technique will permit more accurate localization of the electrodes for improvement in surgical technique and electrode array design., (© 2023 American Society of Neuroimaging.)

Spontaneous intracranial hypotension (SIH) is caused by spinal cerebrospinal fluid (CSF) leaks, which result in continued loss of CSF volume and multiple debilitating clinical manifestations. The estimated annual incidence of SIH is 5/100,000. Diagnostic methods have evolved in recent years due to improved understanding of pathophysiology and implementation of advanced myelographic techniques. Here, we synthesize recent updates and contextualize them in an algorithm for diagnosis and treatment of SIH, highlighting basic principles and points of practice variability or continued debate. This discussion includes finer points of SIH diagnosis, CSF leak classification systems, less common types and variants of CSF leaks, brain MRI Bern scoring, potential SIH complications, key technical considerations, and positioning strategies for different types of dynamic myelography. The roles of conservative measures, non-targeted or targeted blood patches, surgery, and recently developed endovascular techniques are presented., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)