The Ventricular System of the Brain: Anatomy and Normal Variations Lindsay Stratchko, DO,* Irina Filatova, MD,* Amit Agarwal, MD,* and Sangam Kanekar, MD*,†

The cerebral ventricular system is intimately associated with the forebrain and brainstem. The ventricular system functions to produce and circulate cerebrospinal ﬂuid, which plays an important role in mechanical protection and regulation of homeostasis in the central nervous system. This article discusses anatomy and neuroimaging of the ventricular system and highlights normal anatomical variations that may be mistaken for pathology. Applied surgical anatomyisreviewedwithemphasisonoperativeapproach and potential risk to adjacent central nervous system structures. Semin Ultrasound CT MRI 37:72-83 C 2016 Elsevier Inc. All rights reserved.

Introduction Lastly, applied surgical anatomy is discussed, highlighting operative approach and potential risk to adjacent structures. he ventricular system is composed of a set of adjoining Tcavities that produce and circulate cerebrospinal fluid (CSF) within the brain. CSF is produced within the ventricular Anatomy system by specialized ependymal cells known as choroid plexus. This fluid serves many purposes, including mechanical Lateral Ventricles protection, regulation of homeostasis within the cerebral The paired lateral ventricles are composed of the body and atria interstitial fluid, as well as facilitation of brain development. centrally with the anterior (frontal), inferior (temporal), and CSF travels through the ventricular system in a unidirectional, posterior (occipital) horns forming a C-shape, extending rostrocaudal fashion and ultimately communicates with the peripherally in their respective cerebral lobes. The lateral cranial and spinal subarachnoid space, which is the predom- ventricles are intimately associated with portions of the inant location of CSF reabsorption (Fig. 1). diencephalon and telencephalon and communicate with the Knowledge of anatomical relationships between the ven- third ventricle through the foramen of Monroe. tricular system and the surrounding brain parenchyma is The anterior, or frontal, horns of the lateral ventricle extend essential in understanding intraventricular pathology and the from the frontal lobe, connecting with the body of the lateral potential risks associated with surgical management. It is ventricle at the level of the foramen of Monroe (Fig. 2). The important to be familiar with several anatomical variations to corpus callosum wraps around the frontal horn forming the avoid false diagnosis as well as prompt further investigation for superior, anterior, and inferior boundaries. The corpus cal- fl fi associated central nervous system (CNS) abnormalities. This losum is a broad, at group of nerve bers situated midline in article aims to review pertinent ventricular anatomy with the supratentorial brain. It is the largest white matter tract and emphasis on recent advances in neuroimaging. We provide is responsible for interhemispheric communication. The an overview of anatomical variations of the ventricular system corpus callosum is divided into the genu, body, and splenium and their association with other structural CNS anomalies. extending from anterior to posterior, with a small portion termed the rostrum (from the Latin “beak”) projecting inferior and posterior from the genu. The genu of the corpus callosum *Department of Radiology, Hershey Medical Center, Penn State University, defines the roof and anterior wall of the frontal horn, and the Hershey, PA. rostrum forms the floor. The frontal horns are separated by the † Department of Neurology, Hershey Medical Center, Penn State University, septum pellucidum, and they are bordered laterally by the Hershey, PA. Address reprint requests to Sangam Kanekar, MD, Departments of Radiology head of the caudate nucleus (Fig. 2). & Neurology, Hershey Medical Center, The Pennsylvania State University, The bodies of the lateral ventricles are situated superior to 500 University Dr, Hershey, PA 17033. E-mail: [email protected] the thalamus. The anterior-most aspect of the body is the

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Figure 1 CSF flow study. Sagittal images of the CSF flow study, (A and B) normal flow in the prepontine cistern through the foramen magnum into the cervical canal. foramen of Monroe, and the posterior boundary is defined by of decussating fibers of the corpus callosum that radiate the convergence of the fornix and corpus callosum. The roof is laterally, overlying the lateral ventricles, also forming the formed by the body of the corpus callosum, which parallels lateral boundaries of the trigones as well as the occipital and and defines at least a portion of the superior border of each temporal horns. The caudate nucleus also contributes to the segment of the lateral ventricles. The caudate nucleus forms the lateral wall of the atrium, situated anterior to the tapetum. lateral border of the lateral ventricle body. Medially, the corpus callosum and calcar avis (or hippocampus The atrium of the lateral ventricle, also referred to as the minor) form the superior and inferior margin of the atrium, trigone, extends from the posterior aspect of the body and is respectively. The floor of the atrium is defined by the collateral contiguous with the paired inferior (temporal) and posterior trigone. (occipital) horns. The body, splenium, and tapetum of the The posterior horns, also referred to as the occipital horns of corpus callosum delineate the superior border of the atrium. the lateral ventricles, converge medially as they extend into The tapetum, from the Latin tapete or “carpet,” is composed occipital lobes. In the supine patient, the occipital horns are the

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Figure 2 Normal anatomy and relationships of lateral ventricle. Midline sagittal T1 WI image, (A) corpus callosum (arrow) that forms the superior border of the lateral ventricles, fornix (arrowhead) that forms the superior margin of the third ventricle. T is thalamus. Axial T2 WI, (B) frontal horns (arrowheads) and trigone (spiral arrows) of the lateral ventricle lined laterally by caudate head (CH). Lateral drain in the third ventricle (thick arrow) via foramen Monroe (thin arrow). p, putamen; t, thalamus. Axial T1 WI slightly superior to (B), body of the lateral ventricles (arrows) surrounded by body of the caudate nucleus (arrowheads). WI, weighted image. Download English Version: https://daneshyari.com/en/article/2737508

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