Normal brain anatomy in the transversal plane.
The two hemispheres are subdivided into four lobes: the frontal lobe, the parietal lobe, the temporal lobe and the occipital lobe fig. The brain is covered from inside out by the pia mater, the arachnoid mater, the dura mater and the skull roof fig. In this space are blood vessels and the cerebrospinal fluid. A venous hemorrhage may cause an artificial subdural space between the arachnoid mater and dura mater see subdural hematoma in Pathology section. The outer layer of the dura mater is attached to the skull roof. Cerebrospinal fluid, often abbreviated as CSF, is produced in the choroid plexus, located in the ventricles.
The CSF then flows through the foramina to the subarachnoid space over the convexity of the brain and around the spinal cord fig. Resorption takes place in the venous sinus through the arachnoid granulation, fig 7. The CSF acts as a transport medium of nutrients and waste and as a cushion for the brain and spinal cord.
Figure 6. Circulation of the cerebrospinal fluid in the coronal plane a and sagittal plane b. The subarachnoid space is enlarged in certain places; the subarachnoid cisterns. Sylvian fissure and quadrigeminal cistern W shape in the transversal plane. Suprasellar cistern pentagon in the transversal plane. Prepontine cisterns moon shape in the transversal plane. Fourth ventricle IV. In a subarachnoid hemorrhage, the blood is located in the subarachnoid spaces fig. Figure Detailed illustration of a subarachnoid hemorrhage.
The blood is located between the pia mater and the arachnoid mater.
Brain in the coronal plane. The subarachnoid hemorrhage follows the gyri sulci pattern and spreads out over the left convexity. The hemorrhage may be secondary to a head trauma. Other non-traumatic causes include: an AV malformation, eclampsia and hypertensive hemorrhage.
A CT examination without contrast is the first diagnostic choice. Characteristic on a CT without contrast fig :. Subarachnoid blood in the prepontine cisterns hyperdense obliteration of the moon shape. Blood along the right cerebral convexity. The blood follows the cortical gyri sulci pattern, characteristic of subarachnoid blood. J Clin Diagn Res. Koehler, Sylvius, Franciscus. Encyclopedia of the Neurological Sciences. Edit article Share article View revision history Report problem with Article.
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Cases and figures. Location of surgically treated aneurysms.
After surgical treatment of patients with UIAs, The vasospasm rate was as expected the highest in HH 4 and 5. Figure 4 ]. Association of SAH severity, vasospasm and infarction. The rate of vasospasm red line is increasing significantly when bleeding occurs. Even when vasospasm rate increases significantly in HH 1 and 2 the infarction rate in this group is similar to incidental aneurysms without bleeding which has a low number of patients with spasms. Figure 5 illustrates the outcome of the treated patients in the different patient groups. Severity of SAH and patient outcome.
Yasargil described four anatomical variants of the SF. In the present study, the anatomical variants of the SF were determined on preoperative CCTs and correlations of the different anatomical categories with the patients postoperative outcome had been studied. The rate of ischemic stroke, however, or occurrence of DCI did not seem to correlate with the SF variants, rendering other factors responsible for DCI like vasospasms, injury of veins during surgery, or injury of perforating arteries. Nevertheless, the clear correlation of more complex SF anatomical variants with brain edema cannot exclude the logical implication of such an edema in worsening the formation of a delayed neurological deficit in collaboration with other cofactors.
Since different approaches to aneurysms are described, which are based on the pterional approach and use the SF as their pathway, the anatomical variants of the SF as seen on the preoperative CCTs should be taken into consideration when the extend of the pterional approach is planned. In a complex anatomical variant of the SF, a sphenoid ridge keyhole approach as described by Nathal et al.
In contrast, the role of neuroanesthesia helps tremendously in reducing brain tension and promoting a slack brain. The SF is only partially open.
Projecting the CTAs in the direction of the approach can also be of substantial help for the preoperative planning. Another interesting point considering the anatomy of the SF is the preoperative knowledge of the anatomical variant for neurovascular surgeons in training. SF category 3 and 4 requires more brain retraction to reach the aneurysm lying in a complex SF. Hence, complex SF anatomy should not be the first surgical experience for the neurovascular rookie.
Microsurgical Anatomy of the Temporal Lobe and Its Implications on Temporal Lobe Epilepsy Surgery
SF category I is the easiest anatomical variant to approach an aneurysm and can be more suitable for a neurosurgeon who just started clipping procedures. The preoperative examination of the CCTs allows a safe identification of the SF anatomy and this anatomical variant should be always taken into consideration when planning the approach to the aneurysm in order to avoid complications. As already shown in the pioneering reports of Fisher[ 5 ] and Hunt and Hess[ 7 , 8 ] and confirmed by many others, the Fisher grade of an SAH as well as the HH grade are negative prognostic factors.
In the analysis of our patients treated on SAH we also showed, in accordance to the well-known literature, that the amount of blood as well as the HH grade significantly increase the rate of vasospasm and DCI, as well as the mortality rate. It is interesting that HH 4 has a much less mortality rate than HH grade 5. Other factors like patient age, aneurysm location, shape, and size were similar between the studied groups showing a satisfying conformity of the studied groups. In this retrospective study, we show that the anatomical variants of the SF can be associated to postoperative complications like formation of brain edema or ischemic lesions.
Preoperative knowledge of the SF anatomy and possibly consecutive adapted extend of the surgical approach can decrease procedure-related morbidity. Advertisers in SNI did not ask for, nor did they receive access to this article prior to publication.
Subarachnoid cisterns - Wikipedia
National Center for Biotechnology Information , U. Journal List Surg Neurol Int v. Surg Neurol Int. Published online Sep Hannah M. Athanasios K. Author information Article notes Copyright and License information Disclaimer. Ngando: ed. Petridis: moc. Received Apr 17; Accepted Aug 6. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
This article has been cited by other articles in PMC. Abstract Background: The sylvian fissure SF is the anatomical pathway used in a pterional approach, which leads to most aneurysms. Results: Postsurgically brain edema formation correlated significantly with more complex anatomical variants of the SF in patients with UIAs and in patients with Hunt and Hess 1 and 2.
Conclusion: The classification of the SF as proposed by Yasargil is more than a pure anatomical observation. Keywords: Aneurysm, sylvian fissure, subarachnoid hemorrhage. Open in a separate window. Figure 2.
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Figure 3. Table 1 Characteristics of brain infarcts in non SAH patients. Figure 4. Aneurysm location As shown in Suppl. Vasospasms and ischemic lesions After surgical treatment of patients with UIAs, Outcome Suppl. Figure 5.