BACKGROUND: Posterior fossa malformation (PFM) is a relatively uncommon prenatal brain malformation. Genetic diagnostic approaches, including chromosome karyotyping, copy number variant (CNV) testing, and whole-exome sequencing (WES), have been applied in several cases of fetal structural malformations. However, the clinical value of appropriate genetic diagnostic approaches for different types of PFMs has not been confirmed. Therefore, in this study, we aimed to analyze the value of different combined genetic diagnostic approaches for various types of fetal PFMs.
METHODS: This retrospective study was conducted at Beijing Obstetrics and Gynecology Hospital, Capital Medical University, Beijing Maternal and Child Health Care Hospital. Fifty-one pregnant women diagnosed with fetal PFMs who underwent genetic testing in our hospital from January 1, 2017 to December 31, 2022 were enrolled; women with an isolated enlarged cisterna magna were excluded. All participants were categorized into two groups according to the presence of other abnormalities: isolated and non-isolated PFMs groups. Different combined approaches, including karyotype analysis, CNV testing, and trio-based WES, were used for genetic analysis. The detection rates of karyotype analysis, CNV testing, and WES were measured in the isolated and non-isolated groups.
RESULTS: In isolated PFMs, pathogenic/likely pathogenic (P/LP) CNVs were detected in four cases (36.36%, 4/11), whereas G-banding karyotyping and WES showed negative results. In non-isolated PFMs, a sequential genetic approach showed a detection rate of 47.5% (19/40); karyotyping revealed aneuploidies in five cases (16.67%, 5/30), CNV testing showed P/LP CNVs in five cases (16.13%, 5/31), and WES identified P/LP variants (in genes CEP20, TMEM67, OFD1, PTPN11, ARID1A, and SMARCA4) in nine cases (40.91%, 9/22). WES showed a detection rate of 83.33% (5/6) in fetuses with Joubert syndrome. Only six patients (five with Blake\'s pouch cyst and one with unilateral cerebellar hemisphere dysplasia) survived.
CONCLUSIONS: We recommend CNV testing for fetuses with isolated PFMs. A sequential genetic approach (karyotyping, CNV testing, and WES) may be beneficial in fetuses with non-isolated PFMs. Particularly, we recommend WES as the first-line genetic diagnostic tool for Joubert syndrome.

OBJECTIVE: A cerebellar bulge prior to posterior fossa resection is an emergency condition during surgery. Intraoperative cerebellar bulging not only increases the difficulty of lesion resection but also brings additional postoperative complications. Currently, there are few systematic reports on this topic. The predictors of cerebellar bulge and how to effectively prevent intraoperative cerebellar bulge are discussed in this article.
METHODS: The clinical and imaging data of 527 patients with posterior fossa lesions who underwent resection at our hospital were retrospectively collected and analyzed. Perioperative clinical and imaging data were assessed. Variables were analyzed using univariate and multivariate regression analyses.
RESULTS: Overall, 10.4% (55/527) of patients had intraoperative acute bulges. Multivariate analysis revealed that age <60 years, body mass index ≥24, lesion size ≥30 (mm), cerebellar tonsillar herniation and/or hydrocephalus, and perilesional edema (moderate-severe) were predictors of cerebellar bulging. Relief of the cerebellar bulge can be accomplished by excising the lesion, releasing cerebrospinal fluid, and removing the cerebellum (the outer one-third). Obvious cerebellar-related complications occurred in 4 patients postoperatively, and the symptoms disappeared after 6 months of follow-up.
CONCLUSIONS: Cerebellar bulging during intraoperative posterior fossa resection deserves attention. Through the analysis of multiple factors related to cerebellar bulge, comprehensive evaluation and early intervention during the perioperative period are necessary. The incidence of cerebellar bulges can be reduced, and surgical complications related to cerebellar bulges can be avoided.

Due to deep location and for being adjacent to neurovascular structures, petroclival meningiomas (PCMs) are generally considered to be associated with a high rate of recurrence and cranial nerve deficits.1 This video presents a 49-year-old female patient reporting right trigeminal neuralgia for more than 1 year. The incidence of this symptom with PCMs is about 5%.2 According to the classification system proposed by Kawase et al.3 and Ichimura et al.,4 this is a tentorium type PCM. A modified anterior petrosectomy approach was adopted based on the tumor size and its origin. The case presentation, surgical technique, postoperative outcome are reviewed. The treatments to the intraoperative trochlear nerve injury and temporal bridging vein occlusion are displayed (Video 1). The patient gave verbal consent for participating in the procedure and surgical video.

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Posterior fossa epidural hematoma (PFEDH) is rare which accounts for just 4-12.9% of all EDH cases. Since its frequently subtle and nonspecific clinical presentation, CT scan has great importance for early diagnosis and treatment of PFEDH. However, indications for surgery depending on the findings of CT image are still controversial.
We retrospectively analyzed 40 pediatric cases of PFEDH. Their baseline characteristic, clinical presentation, imaging findings and outcomes were collected and analyzed. The ellipsoid volume equation X × Y × Z/2 was used to measure the hematoma volume. The Glasgow Outcome Scale (GOS) was used to assess the neurologic functional outcome.
A total of 40 pediatric PFEH patients were included with 8 patients having poor outcome and 32 patients having a relatively good prognosis. GCS score showed a significant difference between good and poor outcome groups (p < 0.001). Y value on CT image was significantly bigger in poor outcome group than good outcome group (p < 0.01). Similar results were got in X/Z value (p < 0.05) and Y/Z value (p < 0.01) which reflected the shape of hematoma. A predictive model with Y + X/Z showed the largest area under the ROC curve with a sensitivity of 75.0% and specificity of 93.7%.
GCS score at admission was closely related to the prognosis of the pediatric patients with PFEDH. The morphometry of PFEDH has a crucial role in judging the prognosis. Axial convex-shaped hematoma was associated with poor curative effect of surgical treatment.

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An intracranial nerve-enteric cyst is a relatively rare benign disease, and the main clinical manifestations are related to the location and size of the cyst. The main symptoms are caused by cyst compression. When the cyst is small without compression, it may have no obvious symptoms, and when the cyst increases to a certain degree, it may cause corresponding clinical manifestations. The diagnosis of this disease is mainly based on clinical manifestations, imaging examinations, and pathological examinations. The authors present a 47-year-old woman who was admitted to the hospital with \"dizziness\". Imaging was performed and revealed a small round lesion in the posterior cranial fossa in front of the brainstem. It was surgically removed and the postoperative pathology revealed an intracranial neuro-enteric cyst. The patient\'s dizziness disappeared after surgery and was reviewed 1 year later without recurrence.

Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI).
To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction.
Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ).
Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI.
Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI.