Dr Handler: We choose by the area that seems most accessible. Remember that by definition these will look very uniform, so no particular benefit to select one area over another. However, as the “typical one” is still “allowed” to have an area of enhancement and central necrosis, we would select both the margin of that area and the center as well.

Dr Handler: Typically, a couple of cm. Need to get through muscle at the back of the neck to get to bone, so the depth requires a little length of incision.

Dr Handler: Cerebellum controls for smooth movements and balance. The middle cerebellar peduncle, the anticipated approach, can be penetrated safely with a brain canula safely, with no expected consequence.

Dr Handler: Yes and no. the image guidance system stores an MRI image of the brain. The “real time tracking” shows the position of the needle in relation to the stored image of the brain. It does not update with new images as you go.

Dr Handler: I am not sure where I talked about a “track record” per se. I can say that there are nearly 400 documented stereotactic brain stem biopsies in the literature, both in kids and adults. a very substantial number of the series are in kids alone, though I do not have the exact number at my fingertips. There is no difference in the technique between kids and adults other than the thickness of the skull and the amount of pressure that is applied to the pins which stabilize the head in position so that there is no movement during the insertion of the brain biopsy instrument (=”needle” colloquially)

Dr Handler: It would allow appropriate diagnosis in the context that these tumors, on biopsy or autopsy, have proven to be at least 4 different types. Treatment of, for example, PNET and glioblastoma is different in other parts of the brain, so should appropriately be different here as well. In addition, determining the molecular genetics of a tumor may suggest that certain of the more “experimental” therapies might be more beneficial for an individual patient than another of the experimental therapies. Right now, we throw them all into the same bag, and may be muddling our results so that we cannot understand what is happening.

Dr Handler: Assuming no complications, as long as they are now.

Dr Handler: Need is relative. We would likely put a child in the PICU overnight whether he/she wakes up neurologically unchanged or not. The ICU stay after most brain tumor operations, including this type, is to make sure that IF there is a late neurological deterioration it is picked up quickly. Most kids will stay only overnight.

Dr Handler: Yes, but then, all of these kids are intubated for the purpose of putting in a permanent IV for long term therapy so not an “extra” anesthetic, just an extension of one that would happen anyhow.

Dr Handler: In theory yes, though in practice, these kids still are receiving high dose steroids, and are in hospital for stabilizing and planning for radiation therapy, and most have deficits which would preclude swimming anyhow. Kids don’t get back to their prior baseline for a while, after radiation has begun.

Dr Handler: Typically, worsening of an existing weakness, visual disturbance, balance issue, or the like. Usually a few days. So for example, a child with an atypical tumor who was at our hospital recently and biopsied a few days ago, became more somnolent and had worsened weakness of the arm and leg, which then cleared three days later.

Dr Handler: In theory yes. In fact there is no hard and fast rule about when to start radiation. So, for example, one would wait till after a weekend to start radiation, anyhow, just because unless there is a potential for imminent demise or catastrophic irriversible neurological collapse, we don’t do radiation emergently. Families may take a while to decide how to proceed, or until a child who has hydrocephalus has had a drain converted to a shunt, or whatever, can delay therapy without apparent compromise.

Dr Handler: Yes, certainly. This is the focus of an old debate, and a question for which there is no right answer. There is no doubt that the more tissue that is taken out, the more confident one can be that the specimen is representative of the tumor as a whole. And the more opportunity one has to do additional tests on the tissue. However, a stereotactic biopsy involves a very small incision, a small hole in the bone, and in the covering of the brain the dura, and minimal disturbance of the brain equals “minimal morbidity.” An open biopsy of this deep lesion requires a large incision in the muscles of the neck, which hurts, a much larger opening in the bone, and greater risk of bleeding and so on. The brain has to be manipulated to gain access to the area of the biopsy, which introduces risk from pressure on the brain. Then, the more tissue you take out, the greater the risk of a greater degree of neurological deficit and the greater the chance that the deficit would be permanent.

Dr Handler: The data shows that to be relatively small, but the risk we accept in exchange for the lesser surgical risk and the decreased time of recovery after the procedure. For example, if the sample showed that the tumor was a low grade glioma, would the treatment be different than if the tumor were a GBM? Yes If so, how? Less toxic therapy with smaller risk of treatment related complications. If not, why do the biopsy? Historically, the observation has been that “they all die anyhow” so why do it. It is not really clear that that is right. We have all seen kids who by that formula should have died quickly, but did not, presumably because of the inaccuracy of the initial diagnosis.

Dr Handler: Rebiopsy if the clinical situation warrants it, just as we do in tumors elsewhere in the brain.

Dr Handler: Again, the idea is that the biopsy should drive the therapy. We can only work on the data we have. And we will always have to balance the risk of taking more tissue and thereby doing more damage, with the risk of making the wrong diagnosis (which can sometime happen even with open operations)

Dr Handler: Not really. Most stereotactic biopsies are accurate enough that we keep doing them, rather than to abandon the technique.

Dr Handler: Yes. One would never irradiate a small child with a low grade tumor. That child would get a different chemotherapy

With no biopsy? Irradiation, possible experimental therapy
With a biopsy showing that the tumor was low grade? Low grade chemo regimen
With a biopsy showing that the tumor was not a glioma, but a PNET? Radiation and chemo for PNET
With a biopsy showing that the tumor was a GBM? Radiation, possible experimental therapy