Biopsy [3]

Biopsies can be categorized into excisional biopsies or an incisional biopsies. When a tumor or a specific area is surgically removed, the process is calles excisional biopsy. If the occasion is taking samples of a tissue, the surgery is called incisional biopsy. With the guidance of computer assisted imaging, a very thin needle is inserted into the brain, which removes tumor tissue at its tip. 

Risks:

The removed sample of tissue does not belong to the targeted tumor cell, as the sample is very tiny and could miss the tumor. In addition to that, the sample can be a fragment, which does not reflect the overall tumor, but a part of it with a lower tumor grade. Also, biopsies can lead to local bleedings.

This surgery setup for biopsy fixes the biopsy needle with a frame in order to
help being precise and avoid shaking, as it can be very harmful. [Source]

Craniotomy/Craniectomy [4,5]

In order to perform a biopsy, a portion of the skull has to be removed. This skull opening is called craniotomy. It can either be done under general anesthesia or a local anesthesia, if brain functions needs to be assessed during the surgery. After the skin incision in the tumor near area, the skin and muscles are lifted of the bone and folded back. Then a drill is performed to get into the skull. Then, the dura, the protective covering of the brain, is opened to get to the tumor area. After the problem is solved, the dura is sutured and the bone flap is replaced with plates and screws, which retain permanently as a support to the area. If this replacement is not done, this process is called craniectomy. This allows swelling of the brain without complications due to pressure on other brain regions.

The image on the left side depicts each step of a 
craniectomy. [Source] 

Partial Removal/Debulking [6,7]

Sometimes, tumor cells cannot be completely removed, because it is too risky as structures which controls vital functions are nearby or the affected brain cells are critical themselves. Therefore, a precess called debulking is performed, which reduces the tumor volume or the tumor is removed partially. Hence, the effectiveness of other therapy methods such as radiation or chemotherapy increases. Both methods can also be palliative therapies and can lead to extend the patient’s life.

Note that the tumor's size decreased, but
the position of it seems to be critical. [Source]

The image above shows the general setup of a cerebral shunt.
[Source] 

Shunt [10,11]

A shunt is a tube, which helps with redirecting CSF to other locations in the body where it can be absorbed. Basically, a shunt is helpful for preventing overswelling, that means a high concentration of CSF, which can lead to pressure on other brain parts and major complications. The tube itself consists of the inflow catheter, the valve and the outflow catheter. The direct connection to the CSF is handled by the inflow catheter. The valve regulates the flow of CSF, whereas the outflow catheter directs the fluid to part where it is absorbed as part of the circulatory process.

The Surgery is undergone in general anesthesia. The first entry to the brain is placed behind the ear, where the first catheter is inserted(inflow). A second catheter is placed under the skin, starts near the first entry and leads to the abdominal cavity, where the absorption process happens.

Risks

•  infection in the shunt or brain
•  blood clots
•  bleeding in the brain
•  damage to brain tissue
•  swelling of the brain

Ommaya Reservoir [8,9]

In this method, a small container is inserted under the scalp. It is attached to a small tube, which ends in the ventricle, where the CSF is produced. The ommaya reservoir enables the so called intrathecal chemotherapy, where the drug is given into the fluid which surrounds the brain. As most chemotherapy drugs are blocked by the blood-brain barrier, the ommaya reservoir is used as the alternative way in order to reach the cancer cells directly. The surgery for installing the reservori is performed under general anesthesia. WIth the help of MRI, the ommaya reservoir is placed at the right place. After the process, there will be a small bump on the patient’s head.

This image illustrates the inserted Ommaya reservoir
with the general brain anatomy. [Source]