Prof. Dr. Dr. med. Konstantinos Gousias is a distinguished expert in the fields of neurosurgery and spinal surgery, demonstrating his extensive expertise at the Athens Medical Center in Athens. His impressive professional career and his work at leading international university centers underscore his exceptional skills and his status as a leading specialist in his field.
Prof. Dr. Gousias is a member of the 15-member Commission on Surgical Neuro-Oncology of the European Society for Neurosurgery and specializes in particular in the surgery of brain and spinal cord tumors, skull base surgery, and complex and endoscopic spinal procedures. His expertise encompasses the treatment of a wide range of neurological and neurosurgical conditions, including central nervous system tumors, aneurysms, and arteriovenous malformations, trigeminal neuralgia, and other pain syndromes. His approach is characterized by the use of precise microsurgical, robotic, and endoscopic techniques, which enable minimally invasive treatments and significantly shorten patients’ recovery times.
As Chief of the Department of Neuroscience at Athens Medical Center—a facility distinguished by interdisciplinary collaboration and state-of-the-art equipment—Prof. Dr. Gousias ensures high-quality patient care. Close collaboration with other specialists and the use of the latest technologies in the operating room enable him and his team to effectively perform complex surgical procedures and tailor treatments to each patient’s individual needs.
Prof. Dr. Gousias is not only active in clinical practice but is also deeply involved in research and teaching. He is an academic member of three medical schools, has authored numerous scientific publications, and serves as a clinical principal investigator in international and national studies. His teaching activities and his commitment to the continuing education of young physicians contribute significantly to the ongoing advancement of neurosurgery. Through his extensive experience, his dedication to research, and his patient-centered care, Prof. Dr. Gousias has established himself as a leading figure in neurosurgery. His patients appreciate both his professional expertise and his empathetic approach, through which he develops individualized treatment plans and ensures patients receive comprehensive information.
The editorial team of the Leading Medicine Guide gained additional insights into benign brain tumors, known as meningiomas, through a conversation with Prof. Dr. Gousias.
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Meningiomas present a complex medical challenge because, although they do not metastasize, their growth exerts pressure on surrounding brain tissue and can even encase some cranial nerves. These tumors arise from the cells that protect the brain—specifically, the middle soft meninges, also known as the arachnoid membrane—and are characterized by slow but steady growth. The effects on patients can vary depending on the tumor’s size, type, and location and may manifest as neurological symptoms such as headaches, visual disturbances, or motor impairments.
“Meningiomas are the most common primary tumors of the central nervous system that arise from a layer of the meninges, the protective membranes surrounding the brain. They account for about 40 percent of all brain tumors. These tumors typically develop more slowly than other types of tumors and may be asymptomatic or present with symptoms such as headaches, neurological deficits, or seizures. The incidence of meningiomas varies by gender, but they occur more frequently in women (about four times as often), suggesting possible hormonal influences. Unfortunately, there are no clear reasons for this. However, one significant difference must be noted: while the higher incidence in women pertains to benign tumors, malignant tumors predominate in men, occurring at twice the rate seen in women. Although children are also affected, these tumors—which grow very slowly and usually without symptoms—are often not detected at all or are only discovered incidentally, for example during a CT scan,” explains Prof. Dr. Gousias.
Meningiomas are classified by the WHO (World Health Organization) into three main types based on their biological behavior:
Benign WHO Grade 1 meningiomas: This is the most common form, accounting for about 80–90% of all meningiomas. They grow slowly, are often well-defined, and have a low recurrence rate. However, depending on their location, they can cause neurological symptoms.
WHO Grade 2 meningiomas (mostly atypical meningiomas): These tumors grow faster, are more invasive, and carry a higher risk of recurrence. About 10% of all meningiomas fall into this category. They are still benign.
Anaplastic (malignant) meningiomas (WHO Grade 3): These malignant tumors are rare (approximately 2–3%), aggressive, and grow rapidly. They have the highest recurrence rate, tend to invade surrounding tissue, and are incurable. In these cases, surgery alone is not sufficient; radiation therapy must also be administered.
“Over the years, benign tumors can also develop into malignant tumors. The recurrence rate is also approximately 14% within ten years after the initial surgery. A long-term study was conducted in Bonn (North Rhine-Westphalia) involving approximately 1,000 patients. This study showed that recurrences can occur at various grades; that is, they do not necessarily correspond to the grade of the primary tumor but also depend on other factors, such as the extent of tumor resection,” notes Prof. Dr. Gousias, explaining how the grade of the tumor is determined: “Before surgery, it is relatively difficult to determine the exact grade of a meningioma, especially when it comes to grades 1 and 2. It is also difficult to predict whether the meningioma will behave invasively or not. A definitive diagnosis is made after surgery, or more specifically, after a biopsy. For grade 3 tumors, there are classic imaging findings on MRI and CT prior to surgery that suggest malignant growth. For example, these scans can reveal larger areas of swelling around the tumor and also indicate whether the tumor’s morphology is heterogeneous, which suggests a more aggressive tumor. Similarly, bone destruction is an indicator. Today, there are also significantly more advanced diagnostic procedures such as PET (positron emission tomography) and, more specifically, FDG-PET, which uses molecules to determine whether the tumor is malignant or invasive. Then there is also the option of using AI (artificial intelligence)—here, we can link MRI images with clinical data, for example, and then obtain information in the form of a probability calculation regarding how the tumor is likely to develop. However, this method is only used in larger hospitals in Germany.”
PET (positron emission tomography) is an imaging technique used to diagnose and monitor diseases. FDG-PET is a specialized form of PET used to diagnose and monitor various tumors. This method employs a glucose (sugar)-like, radioactively labeled substance called fludeoxyglucose, which specifically binds to receptors on tumor cells. Tumor cells require more energy—and therefore more sugar—than healthy cells to sustain their uncontrolled growth. This labeling makes it possible to visualize tumors in the body and precisely detect their spread. FDG-PET is particularly useful for identifying tumor recurrences or residual tumors.
The location and size of a meningioma have a significant influence on the choice of therapeutic approach.
Regarding the treatment strategy, Prof. Dr. Gousias explains: “If the tumor is malignant, surgery is always necessary. However, a small benign tumor without symptoms should usually only be monitored regularly. In this case, the location of the benign tumor actually determines the treatment strategy. Imaging techniques are indispensable here for making an accurate diagnosis and planning treatment. Magnetic resonance imaging (MRI) is the gold standard for determining the location and extent of the tumor, as well as for assessing its relationship to surrounding tissues and structures. It can also provide information about the tumor’s blood supply. Computed tomography (CT) can be used as a supplement to detect bone changes and calcifications, which frequently occur in meningiomas. If the tumor is located in critical regions, such as the motor or language centers, it is important to speak with the patient and explain that the benign tumor could cause problems in the near future and that it might be a good idea to remove it quickly as a precaution before any potential problems arise. It is important to emphasize at this point that a meningioma originates from a layer of the meninges, not from the brain tissue itself, and grows by displacement—it does not “eat away” at tissue or infiltrate the brain. This means that during surgery, only the tumor is actually removed, and not any brain tissue.”
Meningiomas located in superficial and more easily accessible areas of the brain can generally be removed more easily and completely through surgery. This minimizes the risk of postoperative complications and often leads to a better prognosis. However, the situation becomes more challenging with tumors located in deeper or critical areas, such as the skull base or near vital structures. In such cases, complete resection may be associated with higher risks, which is why subtotal resection in combination with radiation therapy is often considered.
The growth of a meningioma can significantly affect the patient’s neurological function, as these tumors can exert pressure on surrounding brain structures due to their location and size.
The size of the tumor plays an important role. Smaller meningiomas are frequently observed, especially when they are asymptomatic and grow slowly. For larger meningiomas that cause symptoms or grow rapidly, surgical intervention is generally the goal to relieve pressure on adjacent structures and alleviate symptoms.
“A meningioma grows very slowly, on average 1–2 mm per year. This means there’s usually no rush. It can also be effectively treated with anti-inflammatory medications such as cortisone. Personally, however, I wouldn’t plan any upcoming surgery too far in the future, precisely to avoid potential symptoms. After all, even sudden seizures can be caused by a tumor exerting pressure. In this regard, if a meningioma is deemed suitable for surgery, I would advise the patient to undergo surgery as soon as possible—which, following a consultation, could take place as early as two weeks later,” recommends Prof. Dr. Gousias.
Headaches, seizures, visual disturbances, speech and memory problems, and motor deficits are among the possible symptoms of a meningioma. The severity and nature of the symptoms depend on whether the tumor is pressing on sensitive areas of the brain or affecting important nerve pathways.
The shift from a “wait-and-see” approach to intervention is particularly necessary when tumor growth reaches a point that increases the risk of permanent neurological damage or poses a threat to the patient’s life. In such cases, surgery, radiation therapy, or other therapeutic measures may be required to remove or reduce the size of the tumor, thereby relieving pressure on the brain and protecting neurological function.
In recent years, several innovative surgical techniques and minimally invasive procedures have proven effective in neurosurgery, particularly in the treatment of meningiomas.
“The larger the tumor, the larger the access incision must be to enable its radical removal. Only then can we minimize the risk of recurrence. In approximately 50% of patients, the tumor is located at the base of the skull, which is not easily accessible. In the past, very large incisions were made here, resulting in significant damage to the surrounding tissue (bone or muscle) in the area of the access site. Today, thanks to endoscopic techniques, this is no longer necessary. For example, access to the tumor is gained through keyhole incisions above the eyebrows, behind the ear, or through the nose—using very small incisions or a small drill hole. The duration of the surgery naturally depends on the location and size of the tumor, but on average it lasts about two hours. For larger tumors, the surgery can sometimes take up to five hours. After 2–3 days in the hospital, the patient can usually go home. “We sometimes keep some patients in the hospital a little longer for observation, as the brain may swell after the procedure—and this is the case with larger atypical skull base meningiomas,” explains Prof. Dr. Gousias, adding important information regarding sensitive regions within the skull:
“We can only alleviate patients’ natural anxiety through thorough education, but the anxiety remains. With meningiomas—even if they are benign—it is simply the case that they can interfere with sensitive areas such as the optic nerve. A meningioma has a hard structure, and when this hard tumor adheres to a nerve pathway, it is difficult to remove it completely without disturbing the nerve. This can lead to postoperative neurological deficits, which may be either temporary or permanent. The goal of neuro-oncological surgery is always to avoid causing permanent damage. The patient should not develop new, lasting symptoms as a result of the surgery. And if, during the operation, I see that it’s ultimately better for the patient to leave a small portion of the tumor within important structures, Then subsequent radiosurgical treatment or radiation therapy makes more sense. Fortunately, neurosurgery has advanced to the point where residual tumors rarely need to be left behind these days.”
Neuro-navigation and intraoperative imaging, based on real-time MRI or CT data, allow for precise navigation and verification of tumor removal during the procedure. “Radiosurgery, such as Gamma Knife or CyberKnife—a non-invasive form of radiation therapy for meningiomas—is primarily used for patients who do not wish to undergo surgery. In this case, the tumor is not removed, and it is important to note that benign tumors are generally not as sensitive to radiation—so the effect of radiation therapy is not as effective as tumor removal,” Prof. Dr. Gousias explains.
The risk of recurrence depends on various factors, including the extent of tumor resection, the type and grade of the tumor, and its molecular characteristics.
Prof. Dr. Gousias explains: “As mentioned earlier, there remains a risk that the tumor will return. Out of 100 patients who undergo surgery for a meningioma, we expect approximately 14 patients to experience a recurrence within the first 10 years. The likelihood of recurrence depends, on the one hand, on the biology of the tumor—which we cannot change—and, on the other hand, on surgical factors. If the tumor could be radically removed—including the base of the tumor and, in cases of doubt, affected bone structures were also drilled away to remove all tumor remnants—then the risk of recurrence is significantly reduced. Following a limited resection, the aforementioned risk more than doubles. If any residual tumor remains, the next steps are discussed in the tumor board to determine whether this residue requires follow-up radiation therapy.”
In neurosurgery, the recurrence rate is often assessed using the so-called Simpson classification, which ranges from complete removal of the tumor and its attachments (Grade I) to partial resection (Grade V). In cases of complete tumor removal (Simpson Grade I–II), the frequency of follow-up may be lower than in cases of incomplete resection (Grade III–V), where the risk of recurrence is higher. Additionally, the histological classification of the meningioma plays a role. Benign meningiomas (WHO Grade 1) have a lower risk of recurrence, whereas atypical (WHO Grade 2) or anaplastic (WHO Grade 3) meningiomas may recur more frequently and aggressively, requiring more frequent monitoring.
Regular follow-up examinations and imaging studies play a central role in the treatment and monitoring of patients after the removal of a meningioma.
“The patient definitely needs follow-up care. A sensible follow-up plan begins with postoperative MRI and monitoring in the hospital after surgery, followed by an annual checkup or, in some cases, every six months. If everything remains stable, a checkup every two years is sufficient. The patient can continue their life as normal after surgery. There are no known factors that promote the growth or recurrence of a meningioma after surgery,” explains Prof. Dr. Gousias, adding at the conclusion of our conversation:
“In Germany (and also here in Athens), the necessary interdisciplinary tumor board—comprising neurologists, oncologists, radiation oncologists, surgeons, and neurosurgeons—works very well. I believe there will be significant improvements in diagnostics to enhance early detection. Molecular imaging using AI (artificial intelligence) is already very effective today. Treatment options are already much better today than they were a few years ago. What is currently being tested extensively is a complementary drug therapy. Several studies are currently underway in this area, and we will certainly hear about them soon.”
Thank you very much, Professor Dr. Gousias, and best regards to Athens!
