January 16, 2015
There are very rare circumstances during a Retromastoid Craniotomy, where the petrous bone can have a significant high proptosis covering the area of the trigeminal nerve. This finding often can block the view of the surgeon, and can prevent a thorough inspection of the nerve for decompression. I'm going to use the case of one of my patients to describe this phenomenon. As you can see in this case, this is a right-sided Retromastoid Craniotomy that dura has been opened, and this is the right side of the trigeminal nerve. You can see this high prosthic swelling at the level of the petrous bone that blocks most of the trigeminal nerve, and prevents any efficient, and a thorough inspection of the nerve. In these situations, it's best to persist, and remove this bone very carefully in order to be able to conduct thorough inspection. There could be vascular compression, just along the more distal cisternal segment of the nerve that will be missed if this bony high proptosis is not removed. It is also important to remind all of us that the cisternal segment of the nerve is vulnerable to vascular compression, leading to trigeminal neuralgia. When we use the drill to remove this bone, it is very important, to have much control over the drill, as the slippage of the drill over the bone can injure any of the vital surrounding Cerebrovascular structures. I use a site cutting Cavitron or ultrasonic aspirator, or in other words, Sonopet in this case, this gives me more control without necessarily the regular drill that can slide over the bone, and uncontrollably injure the surrounding structures. As I removed more of this high prosthetic area, more of the nerve was visible. You can see removal of that high prosthetic area revealed a sizable compressive vessel at the level of the trigeminal nerve that would have been otherwise missed. I'll go ahead and mobilize the vessel, and place a piece of shredded a Teflon to prevent any further contact between the vessel and the nerve.
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