This is a relatively short chapter, as there is nothing specific to the anatomy of recurrent gliomas which make the functional anatomy different than first-time surgery. But they are harder, without a doubt, and these challenges and some advice for tackling them are provided as are some examples.
15.2 Issues Unique to Recurrent Gliomas
Wound issues are a much bigger deal: This is especially true with a history of Avastin, but previous radiotherapy can also make this worse, and a poorly healing glioma wound can spell more of a disaster than the tumor was.
There was a previous surgeon: If it was someone else, they may have placed an incision in a way I would never want to be forced to reuse. If it was me, there is a good chance the tumor recurred on the margin of the resection cavity, which in my case was probably eloquent (I usually leave it for a reason).
The arteries may have been radiated: Radiated arteries are more prone to injury, even if you are careful.
The anatomy is abnormal: If the previous resection was aggressive, and involved a complete or partial lobectomy, the remaining normal anatomy probably has shifted into the cavity. For example, I expect to find the IFOF and possibly the MCA near the floor of the middle fossa if I have done an aggressive lobectomy (Fig. 15.1).
The dura is stuck to the brain: Even if you are careful, you can injure eloquent cortices opening the dura and lose the chance to map before the case has even got started. Less obviously, if the brain is stuck to the dura, every move may transmit force to the dura and cause pain making the patient less cooperative. If I did the past surgery, it is likely that the leading edge next to the cavity was eloquent.
The patients are often less functional: They are often less able to map due to tumor recurrence and the long term effects of radiotherapy.
It is often less clear what to take out: At the first surgery, anything enhancing is probably tumor as is more of the T2 hyperintense brain. All bets are off at a repeat surgery: enhancement can be radiation necrosis or pseudoprogression and T2 change could be tumor or radiation effect, or encephalomalacia. Often it is less certain that we should be operating, let alone doing something aggressive (Fig. 15.2).
The mandate is less clear: The data are more variable for repeat surgery, especially for GBM.
There is less brain than before and it’s more likely that what’s left is eloquent: This is more specific to those who do aggressive resections the first time.
One thing to note is that all of these rules primarily apply to true recurrence surgeries and less to cases where an inadequate first surgery is being followed with a more complete surgery, as these surgeries are more like first time cases.
15.3 Strategies for Addressing these Problems
Make the surgery count: The only thing worse than operating in a radiated repeat wound for a small recurrence, is missing part of that recurrence because you were not thorough. This seems like an obvious statement, but it’s quite easy to do when the anatomy is abnormal and the tumor is small.
Expose the minimal amount of brain possible: The less surface area of adherent dura you need to peel off of potentially eloquent brain to achieve your goal of surgery the better. Often I will plan surgery for recurrence in deeper areas of a resection cavity to only open a small area over the cavity so that no cortex is put at risk and will start subcortical mapping immediately after opening the dura (Fig. 15.3,Fig. 15.4). There is no rule that one has to expose cortex in a re-do craniotomy.
Make functional vs oncologic trade-offs rationally: I call this the “bang-for-your-buck” rule. If removing a tumor, or part of a tumor involves a great deal of risk to a functional system to remove 1 cc of enhancement, then this is not a good trade off compared to chemotherapy alone. Alternately, removing a large amount of tumor in a nonfunctioning system or a disconnected part of the brain is a good trade off (Fig. 15.5). Less intuitive is the idea that the system may be working, but unlikely to be salvaged for long. For example, a patient with a mostly paralyzed leg and a big tumor in the motor strip, is probably going to lose the leg motor function completely in the near future, and the decision to leave this tumor because “I don’t want to hurt his leg function,” is irrational as well-performed surgery can only improve on that natural history (Fig. 15.6).
Stay out of the old wound, if possible: The best way to avoid radiated wound problems is to not reopen it if you can avoid doing so. Often, a different cut or angle can achieve a good resection safely and stay out of the wound. Using large resection cavities can also help achieve this goal. Another trick is to use an eyebrow approach to address recurrences in the inferior frontal lobe from previously operated temporoinsular tumors (Fig. 15.7). You can also decide not to open the full wound in some cases.
Get a running start: Sometimes a small recurrence can look deceptively easy. It looks like a lump sitting at the bottom of a resection cavity which should just pluck out. It is worth noting that to pluck it out, you generally need to cut into some brain and separate this lump from the brain. Just trying to shave off a few layers and stop will often leave some tumor in the brain, and is largely inconsistent with our understanding of gliomas. Even small tumor recurrences should be removed with a J-shaped or C-shaped cut using anatomic and/or functional boundaries to define resection goals (Fig. 15.8).
Develop a realistic goal: Some recurrent tumors are bad, and the patient is going to lose function no matter what you do. Other times you have to try to get the patient into the best situation you can and rely on adjuvant therapy to do the rest. On the other hand, you must always remember that you are treating a tumor which is highly capable of killing this patient in rapid and terrible fashion, and that you are not going to help the situation by quitting.