Update from the 5th Edition of the WHO Classification of Nasal, Paranasal, and Skull Base Tumors: Imaging Overview with Histopathologic and Genetic Correlation.

Sinonasal and skull base tumors are a heterogeneous group of neoplasms with considerable histologic variation and overlapping imaging features. In 2022, the World Health Organization updated the head and neck tumor classification, further emphasizing the importance of molecular data and genetic alterations in sinonasal neoplasms. The changes include the addition of new entities and discussion of emerging entities, as well as changes to the taxonomy and characterization of tumors. The new classification focuses on entities that develop in these sites either exclusively (eg, olfactory neuroblastoma) or most frequently. Another change includes reduction in the number of categories by creating separate category-specific chapters for soft-tissue, hematolymphoid, and neuroectodermal lesions. In this review, we briefly discuss the various categories in the new classification with a more detailed description of the 2 new entities (SWItch/Sucrose Non-Fermentable complex-deficient sinonasal carcinomas and human papillomavirus-related multiphenotypic sinonasal carcinoma). We also highlight the emerging entities including IDH-mutant sinonasal malignancies and DEK-AFF2 carcinoma, presently classified as sinonasal undifferentiated carcinoma and nonkeratinizing squamous cell carcinoma, respectively.

High-Resolution 7T MR Imaging of the Trochlear Nerve.

BACKGROUND AND PURPOSE: The trochlear nerve has traditionally been difficult to identify on MR imaging. The advent of 7T MR imaging promises to greatly benefit visualization of small structures due to gains in the signal-to-noise ratio allowing improved spatial resolution. We investigated the utility of a clinically feasible ultra-high-resolution 7T MR imaging protocol for identification of the trochlear nerve, as well as assessment of normal trochlear nerve anatomy. MATERIALS AND METHODS: Coronal high-resolution 2D T2-weighted TSE images used in a 7T epilepsy protocol of 50 subjects at our institution were reviewed by 2 independent radiologists for visualization of the trochlear nerve at the nerve origin and cisternal, tentorial, and cavernous segments. The frequency of nerve visibility within these segments and their anatomy were documented, and disagreements were resolved by joint review. RESULTS: Of the 100 nerves reviewed in 50 subjects, at least 2 segments of the trochlear nerve from the brainstem to the cavernous sinus were identified in 100% of cases. The origins from the brainstem and cisternal segment were visible in 65% and 93% of nerves, respectively. The trochlear nerve was identified at the trochlear groove in 100% of cases and in the posterior wall of the cavernous sinus in 74% of cases. CONCLUSIONS: Coronal high-resolution 2D TSE at 7T reliably identified the trochlear nerve throughout its course and is a promising tool for imaging patients with suspected trochlear nerve pathology.

Neck Imaging Reporting and Data System: More Than Just a Template.

The Neck Imaging Reporting and Data System (NI-RADS) is a guide developed and introduced in 2017 by head and neck radiologists who worked in an academic radiology department. Based on the Breast Imaging Reporting and Data System, the initial goals of NI-RADS were to make posttreatment head and neck cancer imaging dictations more succinct and efficient, guide treating physicians in the next appropriate steps when recurrence was suspected, and encourage institutional and national research. NI-RADS is more than a dictation template, and it is best instituted after a head and neck imaging practice is established. We support the use of NI-RADS once a radiologist understands the nuances of head and neck cancer, including the biology, common subsites involved, essentials of tumor staging, common posttreatment benign imaging appearances, and subtleties of recurrent disease.

Brain Abnormalities and Epilepsy in Patients with Parry-Romberg Syndrome.

BACKGROUND AND PURPOSE: Parry-Romberg syndrome is a rare disorder characterized by progressive hemifacial atrophy. Concomitant brain abnormalities have been reported, frequently resulting in epilepsy, but the frequency and spectrum of brain involvement are not well-established. This study aimed to characterize brain abnormalities in Parry-Romberg syndrome and their association with epilepsy. MATERIALS AND METHODS: This is a single-center, retrospective review of patients with a clinical diagnosis of Parry-Romberg syndrome and brain MR imaging. The degree of unilateral hemispheric atrophy, white matter disease, microhemorrhage, and leptomeningeal enhancement was graded as none, mild, moderate, or severe. Other abnormalities were qualitatively reported. Findings were considered potentially Parry-Romberg syndrome-related when occurring asymmetrically on the side affected by Parry-Romberg syndrome. RESULTS: Of 80 patients, 48 (60%) had brain abnormalities identified on MR imaging, with 26 (32%) having abnormalities localized to the side of the hemifacial atrophy. Sixteen (20%) had epilepsy. MR imaging brain abnormalities were more common in the epilepsy group (100% versus 48%, P < .001) and were more frequently present ipsilateral to the hemifacial atrophy in patients with epilepsy (81% versus 20%, P < .001). Asymmetric white matter disease was the predominant finding in patients with (88%) and without (23%) epilepsy. White matter disease and hemispheric atrophy had a higher frequency and severity in patients with epilepsy (P < .001). Microhemorrhage was also more frequent in the epilepsy group (P = .015). CONCLUSIONS: Ipsilateral MR imaging brain abnormalities are common in patients with Parry-Romberg syndrome, with a higher frequency and greater severity in those with epilepsy. The most common findings in both groups are white matter disease and hemispheric atrophy, both presenting with greater severity in patients with epilepsy.

Absence of Meckel Cave: A Rare Cause of Trigeminal Neuralgia.

Trigeminal neuralgia is a debilitating condition with numerous etiologies. In this retrospective case series, we report a cohort of patients with a rarely described entity, absence of Meckel cave, and propose this as a rare cause of trigeminal neuralgia. A search of the electronic medical record was performed between 2000 and 2020 to identify MR imaging reports with terms including "Meckel's cave" and "hypoplasia," "atresia," "collapse," or "asymmetry." Images were reviewed by 2 blinded, board-certified neuroradiologists. Seven cases of the absence of Meckel cave were identified. Seven patients (100%) had ipsilateral trigeminal neuralgia and ipsilateral trigeminal nerve atrophy, suggesting an association between absence of Meckel cave and trigeminal neuralgia. Absence of Meckel cave is a rare entity of unknown etiology, with few existing reports that suggest the possibility of an association with trigeminal neuralgia. Its recognition may have important implications in patient management. Future studies and longitudinal data are needed to assess treatment outcomes and added risks from surgical intervention in these patients.

The Updated Neuroradiology Milestones: Synapsing from 1.0 to 2.0.

The Accreditation Council for Graduate Medical Education is currently in the process of specialty-by-specialty revision of the Milestones. As a result, the Neuroradiology Milestones 2.0 Workgroup was created to refine a system of competency-based assessments for fellow educational growth and development. Strengths of the new Milestones include decreased complexity and uniformity within a subcompetency as it relates to a specific educational development trajectory. The Supplemental Guide serves to decrease clutter in the Milestones 2.0 document and provides a more practical resource for guidance. This article serves to review the history of the Neuroradiology Milestones, followed by a summary of the timeline of events and discussions of the workgroup for development of Neuroradiology Milestones 2.0 and a synopsis of major changes. The plan is for the updated Neuroradiology Milestones to take effect in 2021 or 2022 based on public commentary.