The Common Vein Copyright 2010
Introduction
On cross sectional imaging the midbrain is relatively short and has similar shape to other structures in the region. In general it is almost butterfly shaped.
Two Rectangles Two Ovals and a Tiny Sphere |
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The midbrain consists conceptually of twoanteroleaterally positioned rectancles, and two posterocentrally placed ovals (purple), surrounding the small aqueduct of Sylvius (white). Courtesy Ashley Davidoff MD copyright 2010 all rights reserved 94074b09b01a0910.8s |
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Baseline Shape of the Midbrain Sting Like a Butterfly |
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The midbrain is almost butterfly shaped with rounded posterior borders (colliculi) and rectangular shaped wings – the cerebral peduncles. It is very similar in shape to the pons and medulla on axial imaging but a a few characteristics distinguish it from these structures, most specific of which is the aqueduct of Sylvius that run right through its substance posteriorly shown as a black circle Davidoff art Courtesy Ashley Davidoff MD copyright 2010 all rights reserved 94074b08a.82s |
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| 94074b09b01a08.8s The midbrain consists conceptually of two anteroleaterally positioned rectancles, and two posterocentrally placed ovals (purple), surrounding the small aqueduct of Sylvius (white).
Courtesy Ashley Davidoff MD copyright 2010 all rights reserved |
The Midbrain within the Context of the Whole Brain T2 Weighted MRI |
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The T2 weighted MRI series focuses on the midbrain with characteristic shape and the small aqueduct of Sylvius posteriorly. It is surrounded by portions of the frontal lobe anteriorly, temporal lobes laterally and perhaps small portions of the occipital lobes posteriorly. Davidoff art Courtesy Ashley Davidoff MD copyright 2010 all rights reserved 94081.4kc01.8s |
Cerebral Crura and Colliculi Tectum and Tegmentum |
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The posterior end of the midbrain is bordered by the colliculi (purple) in the tectum (roof) of the nidbrain. The anterior border is bordered by the crura cerebri (green) in the cerebral peduncles and tegmentum (floor of the midbrain) Davidoff Drawing Davidoff art Courtesy Ashley Davidoff MD copyright 2010 all rights reserved 94074b09b05b.8s |
Peduncles Substantia Nigra Tegmentum Colliculi and Tectum |
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The anterior border iof the midbrain incorporates the cerbral peduncles(green), and the substantia nigra (black – just posterior to the peduncles. Between the substantia nigra and the aqueduct is an area of the midbrain called the tegmentum (floor of the midbrain) The posterior end of the midbrain is bordered by the colliculi (purple) in the tectum (roof) of the nidbrain. Davidoff art Courtesy Ashley Davidoff MD copyright 2010 all rights reserved 94074b09b05b.83s |
The Cerebral Crura and the Colliculi The Tegmentum and the Tectum |
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The T2 weighted MRI series focuses on the midbrain with characteristic shape and the small aqueduct of Sylvius posteriorly. The cerebral crura are now shown anteriorly (green) in the cerebral peduncles, and the colliculi are shown posteriorly in the tectum or roof posteriorly Davidoff art Courtesy Ashley Davidoff MD copyright 2010 all rights reserved 94081.4kb07.8s |
The Cerebral arteries Characteristically Surround the Midbrain |
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The MRI T2 weighted series now focuses on another very characteristic feature of the midbrain in that it is surrounded by the anterior and posterior cerebral circulations, and in this case portions of the arteries are seen with parts of the middle cerebral seen anteriorly and parts of the posterior cerebral seen posteriorly Davidoff art Courteys Ashley Davidoff MD copyright 2010 all rights reserved 94081.4kc02.8s |
The Face of a Baby Pig |
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As we start to delve into the complexity of the nuclii of the midbrain the shape takes the form of the head of a baby pig Davidoff art Courtesy Ashley Davidoff MD copyright 2010 all rights reserved 94074b08a06b1b.8s |