Colloid cyst: Transcortical Approach Using Tubular Retractors
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Let's review the techniques for transcortical resection of a colloid cyst using the transfrontal approach via a tubular retractor system. This is a 26 year-old female who presented with progressive headaches. MRI evaluation revealed a colloid cyst slightly toward left frontal horn of the lateral ventricle, potentially some light products within the cyst. And again the location of this relatively large cyst, in relation to the Corpus callosum and the roof of the third ventricle is demonstrated on the sagittal image. Due to the presence of mild hydrocephalus, she under went through section of this colloid cyst. The left transfrontal approach was selected, since the cyst was directed more toward the left side and the left frontal horn was slightly larger. Small curvilinear incision, very minimal expanded bare hole craniotomy, a peel away sheath catheter was used via guidance of neuronavigation to cannulae the frontal horn of the lateral ventricle. Upon reaching the CSF, small amount of brain around the catheter was removed. Here's the tubular retractor system that we use. The corticotomy was slightly extended, as you can see, the size of the corticotomy is relatively small. This small resection is about three centimeter lateral to the midline and just around the area of the coronal suture. So about the location of the Corker's point, you can see the amount of brain debts being removed along the peel away sheath, just very small amount to create more space for the tubular retractor. A 12 millimeter diameter tubular retractor system is inserted. I believe this is the smallest diameter tubular retractor that you can use while retaining the ability to conduct microsurgery. The ventricle is entered. The position of the tubular retractor has to be adjusted so that the foramen of Monro is in view. This is a para-fascicular technique. In other words, we hope that the retractor is dissecting the, fibers in the frontal lobe, and entering the ventricle without significant injury to the fibers. Here you can see the choroid plexus entrained to the left frontal hole of the lateral ventricle is confirmed via examination of the orientation of the choroid plexus and a thalamostriate vein. Now the colloid cyst is identified. Often when you enter the ventricle, the cyst may not be even visible because the choroid plexus or other surrounding structures may be covering it. Now, here is the cyst, it's capsule was coagulated. Here's the wall of the third ventricle on the left side, working through the foramenal Monro to deflate the cyst and circumferentially dissect it from the surrounding structures. Forneases which are located more medially are carefully protected as much as possible. Here you can see a small ring curad evacuating the contents of the cyst. A key maneuver involves aggressive decompression of the cyst. So now you can see through the third ventricle easily, because of the blood products within the cyst. Additional dissection was necessary, inside the cyst so the relatively solid contents are removed. Here is dissection of the superior capsule of the cyst from the fornix. Despite the small diameter of the tubular retractor system, microsurgery is possible. I continue to dissect the wall. Again, here is the cyst wall. Here's the fornix. The manipulation of the fornix is minimized. The cyst is extracted from the roof of the third ventricle. Some of the chroidal vessels, maybe feeding the cyst along its posterior capsule. These vessels have to be coagulated and sharply cut. Further inspection reveals no residual, cyst contents or any pieces of its wall. I'm inspecting the contralateral side. An endoscope can be quite effective to look and examine the contralateral foramen of Monro. Most of the cerebrovascular structures appear intact. Post operative MRI demonstrated complete resection of the colloid cyst without any complicating features. You can see they're very small. Any disruption caused by the tubular retractor within the left frontal lobe and the T2 axial image, again reveals complete resection of the mass without any injury to the surrounding structures. Thank you.
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