Volumetric segmentation in the context of posterior fossa-related pathologies: a systematic review.

BACKGROUND: Segmentation tools continue to advance, evolving from manual contouring to deep learning. Researchers have utilized segmentation to study a myriad of posterior fossa-related conditions, such as Chiari malformation, trigeminal neuralgia, post-operative pediatric cerebellar mutism syndrome, and Crouzon syndrome. Herein, we present a summary of the current literature on segmentation of the posterior fossa. The review highlights the various segmentation techniques, and their respective strengths and weaknesses, employed along with objectives and outcomes of the various studies reported in the literature. METHODS: A literature search was conducted in PubMed, Embase, Cochrane, and Web of Science up to November 2023 for articles on segmentation techniques of posterior fossa. The two senior authors searched through databases based on the keywords of the article separately and then enrolled joint articles that met the inclusion and exclusion criteria. RESULTS: The initial search identified 2205 articles. After applying inclusion and exclusion criteria, 77 articles were selected for full-text review after screening of titles/abstracts. 52 articles were ultimately included in the review. Segmentation techniques included manual, semi-automated, and fully automated (atlas-based, convolutional neural networks). The most common pathology investigated was Chiari malformation. CONCLUSIONS: Various forms of segmentation techniques have been used to assess posterior fossa volumes/pathologies and each has its advantages and disadvantages. We discuss these nuances and summarize the current state of literature in the context of posterior fossa-associated pathologies.

Nuances in detecting retained foreign bodies: a case report of a glass shard embedded in a child's scalp.

Foreign bodies (FBs) are a relatively common reason for admission to the emergency department, with subacutely embedded FBs presenting a diagnostic challenge to physicians. Retained FBs may cause the patient harm and result in litigation when missed. Diagnostic imaging is a powerful tool for localization of FBs and a physician's choice of modality should reflect its anticipated composition. This case report pertains to a 2-year-old boy with a glass shard embedded in his retro auricular scalp who presented with a painful subcutaneous lesion months after an overlying laceration repair at an outside emergency room. The attending neurosurgeon was able to identify a glass shard both on physical examination and axial T2-weighted MRI. Surgical exploration resulted in the removal of a 1-cm square glass shard. Key to the diagnostic potential of imaging is knowledge of a patient's relevant medical history and the composition of the suspected FB. Herein, we describe imaging modalities and their utility in the context of retained glass FBs.

Fat facets deubiquitylation of Medea/Smad4 modulates interpretation of a Dpp morphogen gradient.

The ability of secreted Transforming Growth Factor ß (TGFß) proteins to act as morphogens dictates that their influence be strictly regulated. Here, we report that maternally contributed fat facets (faf; a homolog of USP9X/FAM) is essential for proper interpretation of the zygotic Decapentaplegic (Dpp) morphogen gradient that patterns the embryonic dorsal-ventral axis. The data suggest that the loss of faf reduces the activity of Medea (a homolog of Smad4) below the minimum necessary for adequate Dpp signaling and that this is likely due to excessive ubiquitylation on a specific lysine. This study supports the hypothesis that the control of cellular responsiveness to TGFß signals at the level of Smad4 ubiquitylation is a conserved mechanism required for proper implementation of a morphogen gradient.