eli5: How do surgeons remove a brain tumor without damaging the brain?



I’ve been watching Grey’s Anatomy (I know) and I’m curious- I know that you have to move around the ‘important parts’ to access a tumor if you’re able to even operate at all. But, how is any part of the brain ‘not important’? Meaning, how are surgeons able to touch and manipulate parts of the brain without it 1) turning into mush 2) being damaged and affected permanently ? Thank you and sorry if this is a dumb question, Grey’s has me real into this.

In: Biology


They don’t. The idea is that the damage they cause during surgery is insignificant compared to the immediate risks associated with not removing the tumor.

The literal answer to your question is: they can’t. Any surgery causes damage, this is especially true of a wad of soft tissues that are covered in layers of blood vessles/goo and squeezed into an elaborate series of fused bone plates. The number of ACTUAL brain surgeries (where you’re getting into and screwing around in the soft tissues) is very low for this reason. Most ‘neurosurgery’ is related to the bones and connective tissues attached to the CNS.

Not a dumb question. The probability is that there will be some damage depending on tumor location. They will have the person be awake during the surgery when poking the brain (there are no pain receptors in the brain itself) and test an area with a small electric current (I think) and ask what the patient is experiencing. The calculation is what damage is worth getting the tumor out.

Functions arent strictly localized like you see in cartoons or the movies. Some adaptation is possible. If it is a small area at the surface you may never notice anything missing (might have been signals anbout 1 cm on your rump) something deep and the surgeon may be roughly choosing between loss of some vision, some mobility, some sensory integration or some judgement.

The brain is a bit more flexible than we used to think and the consequences interact with our life situation. The same damage size and location in a person who is a seamstress/tailor who thinks spatially about how pieces fit and what relates to what vs a lawyer who has to speak correctly according to a set of verbal rules and think quickly about various options could have very different life effects. One may be devastated and the other barely notice.

Not a surgeon. But my husband had brain surgery 3 weeks ago. Brain Surgeons have had enough experience and research over the years to know what they can remove and how best to remove it. The lump my husband had was right smack bang in the middle of his brain. (behind his eyes, under the cortex and in front of the cerebelllum) Surgeon went in from the back and slightly to the left. Surgery is also robot assisted. Brain surgery means all the liquid your brain floats in has to be drained away and it has the regenerate after the operation. This give you a headache. Your brain doesn’t like being dry. Going in from the back of the brain makes you very nauseated.

Going in from the front has risks of seizures and epilepsy.

Brain surgery isn’t without risks. Hubby has had a few complications, but he couldn’t keep the lump either.

I’m under the impression that the brain is so soft that, as long as you treat it gently, is extremely hard to damage. Like massaging Jello.


This is because I underwent Deep Brain Stimulation 7-8 years ago to help control my Dystonia. Dystonia is basically where your brain sends too many instructions to certain muscle groups, but how it differs from Essential Tremor or Parkinsons…


Even Mayo Clinic doesn’t know WHY it works, just that it does(I had asked how introducing MORE electricity into an already overactive brain wouldn’t adversely affect things, like memory). DBS is a battery in the chest area programed to send a certain degree of voltage through an underskin wire into electrodes implanted in the brain. It has GREATLY improved my Quality of Life, but it was a bit scary.


Even more scary is that there was a news story maybe a year before my surgery about a world class musician who underwent DBS for his Essential Tremor. I was ‘lucky’ enough that my torso movement made it too dangerous to be awake for the surgery. He was put lightly under, bolted into a halo, then awoken so they could place the electrodes and get feedback on how much it was helping contain his movement. That’s the NORMAL surgical procedure. brr
Edit: They want to keep you awake and get your feedback so they can reposition the electrodes to provide the most benefit.

Ive seen a few sinus operations done by ENT docs (sinusses are in your skull close to your brain) and what also helps the surgeons is that they make a brain scan before the surgery and they can use it as a interactive map during the surgery to know where their equipment is located.

In neurosurgery they can use MRI ‘neuronavigation’ even during the operation itself. Tumor tissue can look very similar to normal brain tissue but looks more different on scans, so very useful 🙂