Interview

Challenges and Solutions in Modern Brain Tumor Surgery

AccumulationCells_Brain
Updated mayo 13, 2022 8 minute read

This article explores the challenges within current surgical approaches used to identify and remove brain tumors and how the field of neurosurgery is changing and improving based on current innovation in medical technology.

May is Brain Tumor Awareness Month

As part of our efforts to raise awareness, we summarized three key challenges related to brain tumor surgery and asked our Director Clinical Affairs, Dr. Susanne Hager, what solutions modern technology offers to overcome these hurdles.

Dr. Hager has worked in the field of neurosurgery for 15+ years. Prior to joining Brainlab she worked as attending neurosurgeon at the Städtische Kliniken München GmbH. As a highly experienced medical expert, she contributes major insights into the validation and development of Brainlab products for neurosurgery. Dr. Hager also has an MHBA in Health Economics from the Friedrich-Alexander-University Erlangen-Nuremburg.


First, why are brain tumors so difficult to treat?

  1. Brain tumors often infiltrate into or adjacent to functionally relevant tissue of the healthy brain and may be located in regions difficult to reach with surgery, therefore surgical treatment must be very precise. Brain tumors cannot be operated on with a “safety margin.”
  2. Each brain tumor is very diverse and has complex morphological, molecular-biological and genetic characteristics, even within the same single tumor. This requires thorough and well-targeted diagnosis and treatment.
  3. The brain is protected by the blood-brain barrier. This network of blood vessels and tissue only allows specific substances to pass through while keeping many other substances, often including anticancer drugs, from reaching the tumor [].
  4. Space within the skull is limited. As tumors grow and become space occupying, they can cause life threatening pressure which makes treatment even more demanding.

Given the space occupying and infiltrative characteristics, the often low radiosensitivity of brain tumors and the limitations caused by the blood-brain barrier, treatment of brain tumors requires a multimodal approach. In this treatment concept, surgery is still the first and most common therapy for most patients with brain tumors. For some tumors, surgical removal and continued monitoring may be the only treatment needed [], but for most brain tumors a multidisciplinary approach is often needed.

Brain tumor diagnosis

When doctors observe an abnormality on an MRI or CT scan, they often conduct a biopsy to extract a sample of tissue for closer examination in order to obtain a proper diagnosis of the lesion. In the case of a potential brain tumor, neurosurgeons may opt to use a surgical procedure called stereotactic biopsy which includes the insertion of a thin needle into a patient’s brain to extract the tissue [].

This is where the first challenge comes into play—maintaining high accuracy and precision when inserting the needle to avoid at-risk structures in the brain, prevent complications that could range from some bleeding to—in rare cases—epileptic seizures and successfully remove the tissue needed for diagnosis.

Challenge 1: Maintaining high accuracy and precision during stereotactic biopsy procedures to prevent surgery-related complications.

Solution

Dr. Hager: “Getting an appropriate diagnosis of a brain tumor is a decisive step for the treatment of these types of tumors. In order to accurately interpret the entire tumor biology, often several targets within one tumor need to be accessed and therefore, several samples need to be obtained. Considering the tumor location, infiltration of functional brain tissue or close relation to vulnerable structures, such as vessels, a dedicated planning step before surgery is required. This will ensure that the surgical procedure will be conducted in a way to duly avoid injury of functional tissue and to prevent subsequent complications such as bleedings, neurological deterioration or epileptic seizures.

Modern planning software can illustrate the brain, its functional areas and organs at risk, the trajectory representing the biopsy needle for the operation as well as the targets that are to be accessed. All relevant information from a variety of imaging modalities such as MR, CT or PET scans should be used for planning.

The established “gold standard“ for stereotactic biopsies has been the frame-based solution for many years. This requires mounting a bulky frame onto the patient’s head for registration. Planning can only be done after the registration CT scan with the frame on the patient’s head and not before surgery. After obtaining the plan, a coordinate system is mounted onto the frame to guide the biopsy needle onto the correct path to the target(s) in the tumor. The frame-based technique is highly accurate but requires specific equipment and more rigorous training for the surgeon.

In recent years, frameless biopsy based on well-established navigation software has been introduced enabling preoperative planning that does not require a bulky frame. The surgical plan can be matched to the patient’s anatomy in the operating room by registration. The most precise registration is automatic registration with intraoperative scanners to obtain sub millimetric accuracy for the procedure. Precise tools, such as robots, have been developed to align the biopsy needle to the planned trajectory and guide it to the target with the help of the navigation software. These frameless procedures can absolutely compete with frame-based procedures in terms of accuracy, diagnostic yield and complication rates.

My vision for the future is that intelligent algorithms, such as Artificial Intelligence, might determine biopsy targets and organs at risk automatically. They may even be able to predict diagnoses with high reliability in order to get rid of invasive biopsy procedures.”

For more information about the solutions, refer to these related studies:

Accuracy of VarioGuide Frameless Stereotactic System Against Frame-Based Stereotaxy: Prospective, Randomized, Single-Center Study 

Reliable navigation registration in cranial and spine surgery based on intraoperative computed tomography 

Brain tumor surgery

Following the clear diagnosis of a brain tumor, the next step for a patient may be to undergo surgery. The first step to perform brain tumor removal requires opening the skull—also known as a craniotomy. To perform this procedure, the patient’s scalp is shaved so that an incision can be made and a piece of bone can be removed to expose the area of the brain over the tumor. After this, the outermost layer of brain tissue, the dura mater, is opened so that the tumor can be located and removed [].

While the steps to performing a craniotomy are well-defined, the surgical procedure itself requires considerable preparation. For example, it is important to identify the right access to the lesion. While this is similar to preparing for a stereotactic biopsy, the access path for tumor resection requires a larger trajectory—a surgical corridor. In addition, neurosurgeons aim to create the smallest incision possible to avoid complications caused by access alone.

All this leads to the next major challenge—determining the least invasive and most precise access path to the lesion.  

Challenge 2: Determining the least invasive and most precise access path to the lesion.


Solution

Dr. Hager: Surgeons need to assess and understand the risks and goals for any given surgery before they go into the operating room. The patient also needs to be informed of the risks associated with the procedure as well as given clear guidance on if the tumor can be removed entirely.

A dedicated preoperative planning software can provide this information. It can help surgeons understand the topographic anatomical relationship between the tumor and adjacent or even infiltrated important brain structures and the accessibility of the tumor. It can also be used to visualize functional tissue, such as fiber tracts, and therefore help define the surgical access path.

The ultimate goal is to determine the safest, least invasive and optimal route to the tumor in order to reach the surgical goal of resection. This may either be gross total resection in which the entire tumor is removed or partial resection in which only a part of the tumor is removed. For example, if functionally infiltrated tissue cannot be resected without expected neurological deterioration of the patient, or if the tumor is very large and occupies a lot of space, a surgeon may opt to conduct a partial resection simply to reduce the tumor burden and pressure. Currently, preoperative planning software supports surgeons in determining the most suitable craniotomy size, location and access to the tumor.

My vision for the future is that we can aggregate surgical planning data with outcome data from an extensive pool of  patients and then apply AI algorithms to automatically determine surgical risks per possible access path for the respective tumor. This would enable surgeons to determine the extent of surgical resection with the lowest risk while incorporating other treatment options, such as radiotherapy, chemotherapy or other local tumor therapies.”

For more information about the solutions, refer to these related studies:

Risk Assessment by Presurgical Tractography Using Navigated TMS Maps in Patients with Highly Motor- or Language-Eloquent Brain Tumors 

Reliability of Semi-Automated Segmentations in Glioblastoma 

Brain tumor resection

Building on the section before, we know that preoperative planning is an essential part of increasing the safety and efficiency of brain tumor surgery. However, even with strategic presurgical planning, once the dura is opened, the patient is susceptible to brain shift. Brain shift is defined as a deformation of the brain due to a variety of factors such as gravity, fluid drainage and tissue resection, etc. [].

Moreover, when it comes to tumor resection, surgeons may not be able to see or differentiate the tumor from normal tissue, even when using a microscope. This combined with brain shift expose the final key challenge related to brain tumor removal surgery—managing considerable obstacles that may arise during surgery.

Challenge 3: Managing brain shift and other potential obstacles during brain tumor removal surgery.


Solution

Dr. Hager: “Once the craniotomy is performed and the tumor is accessed, tumor resection is the next step. By opening the dura and accessing the brain, the anatomy of the patient will not be the same as it was at the time of the brain imaging scans. Tumor tissue will be resected, cerebrospinal fluid will be lost and gravity and brain spatulae will lead to the movement of brain tissue. All this will in turn cause significant brain shift and morphological changes during surgery.

At the same time, tumor tissue and healthy brain tissue is often not possible to differentiate—neither with the naked eye nor with a microscope. The overarching challenge is therefore to acquire updated information on the anatomical and functional areas of the brain throughout the operation.

Various options are possible and used multimodally in order to receive up-to-date information. For example, intraoperative functional monitoring can provide information on functional tissue around the access path or tumor borders by continuous monitoring or live stimulation of tissue. The challenge is the documentation of the results of stimulation—they are not linked to the morphological information in the navigation software and, as such, are not “visible” to the surgeon. Some surgeons help themselves with numbered paper pieces. This is cumbersome and a dated approach to brain tumor surgery. So, we must find ways of incorporating this important functional information into the image data space.

The current gold standard of imaging for the brain is MRI scanning, at least for preoperative diagnostic purposes. These machines are also available for the operating room, but they require specific O.R. design, a tremendous workflow interruption and acquisition time as well as specific, non-magnetic equipment. They are also very costly.

In comparison, ultrasound scans of the brain are a reliable, versatile and more cost-effective alternative to MRI scanners. By integrating ultrasound images into the navigation system, a registration update and navigation on these images and fused MRI images is possible making the interpretation of ultrasound images easier. Elastic fusion algorithms will soon be available to update the preoperative MRI images based on intraoperative ultrasound scans thus revolutionizing the morphological update during brain surgery.

My vision for the future is that access to the brain will be minimized and techniques will be developed to treat the tumor by inserting minimally invasive tools, such as needles or catheters. These software and potentially robotically guided tools might locally ablate, remove or destroy the tumor and be able to apply treating substances, such as chemotherapy, in a scalable and predictable way. Intelligent algorithms will predict the most applicable treatment strategy.”

For more information about the solutions, refer to these related studies:

Challenges and Opportunities of Intraoperative 3D Ultrasound With Neuronavigation in Relation to Intraoperative MRI 

Supratentorial high-grade gliomas: maximal safe anatomical resection guided by augmented reality high-definition fiber tractography and fluorescein 

Tractography for Subcortical Resection of Gliomas Is Highly Accurate for Motor and Language Function: ioMRI-Based Elastic Fusion Disproves the Severity of Brain Shift 

1. National Cancer Institute. Definition of blood-brain barrier. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/blood-brain-barrier .

2. Mellinghoff Ingo K. Brain Tumors: Challenges and Opportunities to Cure. https://ascopubs.org/doi/10.1200/JCO.2017.74.2965 . Published 20 Jul 2017.

3. UR Medicine. Neurosurgery: Brain and Spinal Tumor Program. https://www.urmc.rochester.edu/neurosurgery/services/brain-spinal-tumor/treatments/stereotactic-biopsy.aspx .

4. Precision Brain, Spine & Pain. Craniotomy. https://www.precisionhealth.com.au/healthcare-services/advanced-neurosurgery-spinal-surgery/procedures-and-surgery/craniotomy/ 

5. golby lab Image Guided Neurosurgery Laboratory. Brain Shift. https://golbylab.bwh.harvard.edu/brain-shift/ 

Dr. Susanne Hager

Autor

Director Clinical Affairs

Joanne Tudorica

Autor

Content Development Manager

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