Acoustic Neuroma: The Sitting Position
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Let's review some of the advantages and shortcomings, of the sitting position for resection of acoustic tumors. This is a 32 year-old female, who presented with right-sided hearing loss and was diagnosed with a 2.5 cm acoustic neuroma. The typical appearance of the tumor is apparent. Patient was placed in the sitting position. I use a curvilinear incision, for this position, as the scalp flap or the myocutaneous flap, came reflected anteriorly. Appropriate measures for Venous air embolism are taken. The head of the table is used as an armrest. Despite all the measures taken, you can see that this operative position is somewhat taxing, and relatively uncomfortable for the surgeon. However, there are major advantages involved for dissection of the mass, in the siting position as gravity clears the operative field, and allows bimanual dissection without the use of suction. You can see the long operative distance, and the posture of the arms of the surgeon. Let's focus on the operative field now. The edges of the dural venous sinuses are unroofed. The cerebellum is gently elevated, and the cisterna magna opened to drain additional CSF. Next, the posterior capsule, the tumor is mapped, using the monopolar mapping probe or the stimulating probe. The capsule has subsequently coagulated, and the tumor is generously debulked. Maximal decompression of the tumor internally, is a key factor for improving the efficiency, and safety of the operation. Here are the lower cranial nerves. The neurovascular structures are being dissected away from the tumor capsule, inferiorly. Mapping continues around the circumference of the tumor. Here's the mapping procedure, along the lower pole of the tumor. Next, the tumor is further debulked, using an ultrasonic aspirator. Here's the dissection process, again at the lower pole of the tumor. Here's the eighth cranial nerve, that was disconnected. Here's the major advantage of the sitting position. You can see that I'm conducting, bimanual dissection, and the gravity's clearing the operative field, the suction is not used. And the fine forceps dissect, and carefully mobilized the arachnoid bands, atraumatically. Further tumor debulking is continued. The facial nerve is identified, draped over the superior pole of the tumor. Again, irrigation is used to clear the operative field. The tumor is gently mobilize away from the nerve, and fine forceps, disconnect the arachnoid bands. Here's the facial nerve. The tumor is further debulked. After the tumor is unroofed within the canal. The vestibular portion of the nerve is being disconnected. You can see the facial nerve and its route. It remains intact. And the tumor is completely removed. This is the cisternal segment, and this is the intracanalicular segment. Again, the cisternal segment, and the intracanalicular segment. This tumor was stimulated, at 0.5 milliamps, which means very nice facial function after surgery. Here's the funnel operative corridor. Dural closure. And this patient recovered from her surgery effectively, and had relatively normal fascia function after surgery. Therefore, the major advantages of the sitting position, are the ability, to use bimanual dissection, without the use of suction to dissect nerve, and the pial membranes of that brainstem. However, the risk of venous air embolism is real, and many of the anesthesiologists in the United States feel uncomfortable, with the use of this posture. Thank you.
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