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Concept: Posterior cranial fossa


BACKGROUND AND PURPOSE: The diagnosis of Chiari malformation type I (CMI) relies on MRI identification of a tonsillar descent (TD) through the foramen magnum, reflecting the overcrowding of an underdeveloped posterior cranial fossa (PCF). However, TD occurs in some patients with normal-sized PCF and, conversely, some patients with borderline or no TD have small PCF. We thus sought to identify a set of prototypic PCF measures for the diagnosis of CMI. METHODS: We performed nineteen measurements of the PCF on sagittal MRI of 100 cases with cerebellar TD ≥5 mm and 50 control individuals, compared the average values in both cohorts and used logistic regression to devise a probability model to predict CMI status. RESULTS: Significant decrements were detected for several PCF-related measures in the patients' cohort. We developed a probability model that combined seven of these parameters to predict diagnosis with 93% sensitivity and 92% specificity. CONCLUSIONS: The addition of simple morphometric measurements in the diagnostic work-up of patients with suspected CMI may facilitate radiological diagnosis. Moreover, identification of the subset of CMI that arise from basichondrocranium underdevelopment is important for both, selection of the most appropriate therapeutic approach as well as proper CMI categorization in research studies.

Concepts: Regression analysis, Positive predictive value, Type I and type II errors, Sensitivity and specificity, Foramen magnum, Arnold-Chiari malformation, Posterior cranial fossa


Objectives The central location and complex neurovascular structures of the posterior cranial fossa make tumor resection in this region challenging. The traditional surgical approach is a suboccipital craniotomy using a microscope for visualization. This approach necessitates a large surgical window and cerebellar retraction, which can result in patient morbidity. With the advances in endoscopic technology, minimally invasive access to the cerebellopontine angle can be achieved with minimal manipulation of uninvolved structures, reducing the complications associated with the suboccipital approach.Methods An endoscopic and microscopic approach was completed on anatomic specimens. To access the central structures of the posterior cranial fossa, a retrosigmoidal approach was undertaken. A keyhole craniotomy was made in the occipital bone posterior to the junction of the transverse and sigmoid sinuses. The endoscope was advanced and photographs were obtained for review. The exposure was compared with that obtained with a microscope.Results The endoscopic retrosigmoidal approach to the posterior cranial fossa provided increased exposure to the midline structures while minimizing the surgical window. The relevant anatomy was identified without difficulty.Conclusion An endoscopic retrosigmoidal approach to the midline structures of the posterior cranial fossa is anatomically feasible. The morbidity associated with retraction of the cerebellum could possibly be avoided, improving patient outcomes. Retrosigmoidal endoscopy provides access to anatomical structures that is not possible using a microscope in a suboccipital approach. Further understanding of the endoscopic anatomy of the posterior fossa can allow for advances in cranial base surgery with improved safety and efficacy.

Concepts: Medicine, Biology, Physician, Anatomy, Human anatomy, Endoscopy, Posterior cranial fossa, Superficial anatomy


It has been well documented that along with tonsillar herniation, Chiari Malformation Type I (CMI) is associated with smaller posterior cranial fossa (PCF) and altered CSF flow and tissue motion in the cranio-cervical junction (CCJ).

Concepts: Arnold-Chiari malformation, Posterior cranial fossa


Nonprojectile penetrating skull base injuries as a result of falls have rarely been confronted in normal neurosurgery although a few nonmissile injuries have been reported. These kinds of injuries represent a life-threatening emergency.

Concepts: Report, Posterior cranial fossa


Endoscopic endonasal approaches (EEA) have gained popularity and acceptance in skull base surgery over the last two decades. So-called expanded EEA allow access in the sagittal plane from the frontal sinus to the odontoid process. The endoscopic endonasal transclival approach allows a unique trajectory into the midline clivus and skull base that is unachievable from traditional craniotomy approaches to lesions such as chondrosarcomas, chordomas, and posterior fossa meningiomas. In this review, we will assess the benefits and drawbacks to using an endoscopic endonasal approach versus transcranial approach to these challenging lesions, assess the anatomical limits of endoscopic endonasal transclival surgery, and discuss the published literature on the topic.

Concepts: Skull, Anatomy, Anatomical terms of location, Coronal plane, Sagittal plane, Posterior cranial fossa


The aim of this study was to investigate prognostic factors for microvascular decompression (MVD) in patients with primary trigeminal neuralgia (TN), with a particular focus on the morphology of the posterior cranial fossa (PCF).

Concepts: Trigeminal neuralgia, Microvascular decompression, Posterior cranial fossa


congratulations to your excellent article: A prospective study on fetal posterior cranial fossa assessment for early detection of open spina bifida at 11-13 weeks. Your work is asking the most important questions clarifying this issue.

Concepts: Question, Spina bifida, Posterior cranial fossa


The management issues of 15 cases of giant and dumbbell shaped facial neurinomas that extended both in the middle and in the posterior cranial fossa is reported.

Concepts: Cranial nerves, Posterior cranial fossa, Power pop


Posterior cranial fossa (PCF) hemangioblastomas are benign, highly vascularized, and well-differentiated tumors with well-described histopathologic features. Although relatively rare, this tumor is the most prevalent primary tumor of the cerebellum in adults.

Concepts: Medicine, Cancer, Anatomical pathology, Benign tumor, Tumor, Posterior cranial fossa


OBJECTIVE The current diagnostic criterion for Chiari malformation Type I (CM-I), based on tonsillar herniation (TH), includes a diversity of patients with amygdalar descent that may be caused by a variety of factors. In contrast, patients presenting with an overcrowded posterior cranial fossa, a key characteristic of the disease, may remain misdiagnosed if they have little or no TH. The objective of the present study was to use machine-learning classification methods to identify morphometric measures that help discern patients with classic CM-I to improve diagnosis and treatment and provide insight into the etiology of the disease. METHODS Fifteen morphometric measurements of the posterior cranial fossa were performed on midsagittal T1-weighted MR images obtained in 195 adult patients diagnosed with CM. Seven different machine-learning classification methods were applied to images from 117 patients with classic CM-I and 50 controls matched by age and sex to identify the best classifiers discriminating the 2 cohorts with the minimum number of parameters. These classifiers were then tested using independent CM cohorts representing different entities of the disease. RESULTS Machine learning identified combinations of 2 and 3 morphometric measurements that were able to discern not only classic CM-I (with more than 5 mm TH) but also other entities such as classic CM-I with moderate TH and CM Type 1.5 (CM-1.5), with high accuracy (> 87%) and independent of the TH criterion. In contrast, lower accuracy was obtained in patients with CM Type 0. The distances from the lower aspect of the corpus callosum, pons, and fastigium to the foramen magnum and the basal and Wackenheim angles were identified as the most relevant morphometric traits to differentiate these patients. The stronger significance (p < 0.01) of the correlations with the clivus length, compared with the supraoccipital length, suggests that these 5 relevant traits would be affected more by the relative position of the basion than the opisthion. CONCLUSIONS Tonsillar herniation as a unique criterion is insufficient for radiographic diagnosis of CM-I, which can be improved by considering the basion position. The position of the basion was altered in different entities of CM, including classic CM-I, classic CM-I with moderate TH, and CM-1.5. The authors propose a predictive model based on 3 parameters, all related to the basion location, to discern classic CM-I with 90% accuracy and suggest considering the anterior alterations in the evaluation of surgical procedures and outcomes.

Concepts: Diagnosis, Surgery, Corpus callosum, Agenesis of the corpus callosum, Foramen magnum, Arnold-Chiari malformation, Morphometrics, Posterior cranial fossa