Training in microsurgical techniques is the first step to allow procedures in the central nervous system. One of them is the dissection of human placenta. Others include mannequin head 1 , virtual reality environment 2 , animal and cadaver dissections 3 . The human placenta is a maternalfetal structure constituted of a bigger fetal portion and a smaller maternal portion. The fetal membranes and the placenta are responsible for protection, nutrition, breath, excretion and hormone production 4 . The placenta usually shows an ovoid shape with a 16-20 cm diameter and a 2-3 cm thickness 4 . It weighs between 500 and 600 gr 4 . The umbilical cord is usually composed of a vein and two arteries. The fetal surface has a fetal corion -amniotic membrane which is very similar to the cerebral arachnoid and a rich vascular component with 1-6 mm diameter vessels 4 . The anterior cerebral artery has 1-3 mm diameter and the medium cerebral artery one is between 2.4 and 4.6 mm. On the other hand, the vertebral artery has 0.92-4.09 mm diameter, the posterior cerebral and the lower posterior cerebelar arteries ones are between 0.65 and 1.78 mm.Therefore, the human placenta is an excellent material for microsurgical technique training 3,5,6 . METHOdThis study was developed at the Microsurgery Laboratory of the Hospital Beneficência Portuguesa de São Paulo and was also approved by the local ethics committee.Twenty-five human placentas were analyzed to check if they were suitable for microvascular exercising. The available length and diameter of the vessel were measured and different microvascular anastomoses were performed. The used microsurgical materials were 3,5,6 : forceps; microsurgery scissors; microsurgical knife; microsurgery needle holders; vascular clip appliers; neurovascular surgery clips; suture thread 10.0; Insulin syringe and needle; saline solution 0.9%.

RESUMO PALAVRAS-CHAVEInfarto da artéria cerebral média, cirurgia. Acidente cerebrovascular. Craniectomia descompressiva. ABSTRACT Massive cerebral infarction and decompressive craniectomy. Literature review KEY WORDSMiddle cerebral artery infarction, surgery. Cerebrovascular accident. Decompressive craniectomy.

Purpose The location of paraclinoid aneurysms is determinant for evaluation of its intradural compartment and risk of SAH after rupture. Advanced MRI techniques have provided clear visualization of the distal dural ring (DDR) to determine whether an aneurysm is intracavernous, transitional or intradural for decision-making. We analyzed the diagnostic accuracy of MRI in predicting whether a paraclinoid aneurysm is intracavernous, transitional or intradural. Methods We conducted a prospective cohort between January 2014 and December 2018. Patients with paraclinoid aneurysms underwent 3D fast spin-echo MRI sequence before surgical treatment. The DDR was the landmark for MRI characterization of the aneurysms as follow: (i) Intradural; (ii) Transitional; and (iii) Intracavernous. The MRI sensitivity, specificity, positive and negative likelihood ratios were determined compared to the intraoperative findings. We also evaluated the intertechnique agreement using the Cohen’s kappa coefficient (κ) for dichotomous classifications (cavernous vs non-cavernous). Results Twenty patients were included in the cohort. The accuracy of MRI showed a sensitivity of 86.7% (95%CI:59.5–98.3) and specificity of 90.0% (95%CI:55.5–99.8). Analyzing only patients without history of SAH, accuracy test improved with a sensitivity of 92.3% (95%CI:63.9–99.8) and specificity reached 100% (95%CI: 63–100). Values of Cohen’s kappa (κ), intertechnique agreement was considered substantial for dichotomous classifications (κ = 0.754; p < 0.001). For patients without previous SAH, intertechnique agreement was even more coincident for the dichotomous classification (κ = 0.901; p < 0.001). Conclusion 3D fast spin-echo MRI sequence is a reliable and useful technique for determining the location of paraclinoid aneurysms in relation to the cavernous sinus, particularly for patients with no history of SAH.

Intracranial aneurysms (IAs) found in the subarachnoid compartment of the internal carotid artery are at risk of rupturing and producing hemorrhage into this space, producing all the known serious pathological manifestations of subarachnoid hemorrhage. On the other hand, those who are exclusively in the intracavernous segment have this negligible risk. It is in this context that a peculiar class of IAs fits, the paraclinoid aneurysms, which are characterized by their complex anatomical relationships with the optic apparatus, anterior clinoid process, the first supraclinoidal arterial branches of the carotid artery, the oculomotor nerve and the segment mainly said clinoid, which is delimited by the proximal and distal dural rings. It is of crucial importance, and challenging, to determine the location of paraclinoid aneurysms and their exact relationship with the cavernous sinus, given the need to establish an adequate line of treatment for each case. Through preoperative studies of 3 t Magnetic Resonance, comparison with 3D bio models and microsurgical exploration, it was possible to accurately demarcate these anatomical relationships. Therefore, today it is possible to establish the accurate location of the paraclinoid aneurysm in relation to the cavernous sinus by means of MR images and to carry out an adequate, effective, and safe operative planning.

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