Tag: Cisterna magna

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Posterior Fossa Midline Epidermoid Tumors: Role of the Inferior Medullary Velum and a Proposed New Imaging Classification

Neurosurgery 93:112–119, 2023

Posterior fossa midline epidermoid tumors (PFMETs) include the epidermoid tumors of the cisterna magna (CM) and fourth ventricle (FV).

OBJECTIVE: To report tumor epicenter-based classification of PFMETs and its clinical and surgical implications with outcome. METHODS: On retrospective analysis of operated cases of intracranial epidermoid tumors, 19 (N = 19) patients having tumor epicenter within FV, CM, or both were included. Cerebellopontine and prepontine cistern epidermoid were excluded. Tumor location was decided based on preoperative MRI and intraoperative findings. Major complication was defined as new onset or worsening of cranial nerve (CN) deficit, sensory motor impairment, or tracheostomy.

RESULTS: The mean (±SD) age of the patients was 42.0 ± 11.6 years (range 25-61 years), with no sex predilection (male: female: 1:0.9). The most common symptoms were cerebellar dysfunction, headache, vomiting, and diplopia. Common CNs affected were VII, V, lower cranial nerve, and VI. The PFMETs were classified based on tumor epicenter as type 1 (tumor epicenter in CM, n = 4/21.1%), type 2 (FV, n = 5/26.3%), and type 3 (involved CM and FV, n = 10/52.6%). Type 2 tumors had a higher incidence of raised intracranial pressure and only facial nerve palsy as preoperative CN deficit. Type 1 tumors had the least incidence of postoperative major complications. Type 3 tumors were the largest and had a greater incidence of brainstem adhesion and postoperative complications. The tumor size, duration of symptoms, and patient age were higher in patients with brainstem adhesion (5.3 ± 1.0 cm, 21 ± 16 months, 44.1 ± 9.2 years) as against its absence (4.8 ± 1.3 cm, 11.2 ± 7.3 months, 38.2 ± 11.7 years). Inferior medullary velum and tela choroidea have a critical role in tumorogenesis, tumor extension, and brainstem adhesion.

CONCLUSION: PFMETs can be classified into 3 subtypes based on tumor epicenter having clinical and surgical implications. Less aggressive dissection and near total excision in the presence of brainstem adhesion yield favorable outcomes.

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The human foramen magnum—normal anatomy of the cisterna magna in adults

The human foramen magnum type A

Neuroradiology (2013) 55:1333–1339

The goal of this study was to radiologically describe the anatomical characteristics of the cisterna magna (CM) with regard to presence, dimension, and configuration.

Methods In this retrospective study, 523 records were reviewed. We defined five CM types, the range of which covered all normal variants found in the study population. Characteristics of the CM were recorded and correlations between various posterior fossa dimensions and CM volume determined.

Results There were 268 female (mean age 50.9±16.9 years) and 255 male (mean age 54.1±15.8 years) patients. CMvolume was smaller in females than in males and correlated with age (Pearson correlation, r =0.1494, p =0.0006) and gender (unpaired t test, r2=0.0608, p <0.0001). Clivus length correlated with CM volume (Pearson correlation, r =0.211, p <0.0001) and gender (unpaired t test, r2=0.2428, p <0.0001). Tentorial angle did not correlate with CM volume (Pearson correlation, r =−0.0609, p <0.1642) but did correlate with gender (unpaired t test, r2=0.0163, p <0.0035). The anterior–posterior dimension of cerebrospinal fluid anterior to the brainstem correlated with CM volume (Pearson correlation, r =0.181, p <0.0001) and gender (unpaired t test, r2=0.0205, p =0.001).

Conclusion The anatomical description and simple classification system we define allows for a more precise description of posterior fossa anatomy and could potentially contribute to the understanding of Chiari malformation anatomy and management.

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