A meningioma is a tumor that develops from the meninges, the protective layers covering the brain and spinal cord. These are the most common primary brain tumors and are often benign, meaning they are not cancerous and grow slowly. The term “tentorial” specifies the tumor’s location on the tentorium cerebelli, a durable fold of the brain’s outer layer that separates the cerebrum from the cerebellum.
Associated Symptoms of a Tentorial Meningioma
Symptoms of a tentorial meningioma result from the tumor pressing on nearby brain structures, such as the cerebellum and brainstem. The onset is gradual, with symptoms becoming more noticeable as the tumor enlarges.
Headaches are a common initial sign and are often more intense in the morning. As the tumor exerts pressure on the cerebellum, which coordinates movement, individuals may experience balance issues, a clumsy gait, or a lack of coordination known as ataxia. Pressure on the brainstem and cranial nerves can also affect other functions.
This pressure can lead to other symptoms, including:
- Vision changes, such as double vision or blurriness, if the tumor impacts nerves controlling eye movement.
- Hearing loss in one ear or a persistent ringing sound called tinnitus.
- Facial numbness or tingling.
- Weakness in facial muscles if the nerves responsible for muscle control are compressed.
Causes and Known Risk Factors
The specific trigger for a tentorial meningioma is unknown in most cases. It is understood that something alters cells within the meninges, causing them to multiply uncontrollably, but the precise reason is not clear. However, several risk factors are known to increase a person’s likelihood of developing a meningioma.
One significant risk factor is prior exposure to ionizing radiation directed at the head for other medical conditions. The risk also increases with age, and these tumors occur more often in women, suggesting female hormones may play a role in their growth.
Certain inherited genetic disorders are also linked to a higher risk. Individuals with neurofibromatosis type 2 (NF2), a condition characterized by the growth of noncancerous tumors in the nervous system, have a greater predisposition for developing meningiomas. While these factors are associated with an increased risk, they do not guarantee that a person will develop a tumor.
The Diagnostic Process
Diagnosing a tentorial meningioma begins with a medical history and a physical examination. This is followed by a neurological exam to assess functions that may be affected by the tumor, such as balance, vision, hearing, and reflexes.
When a brain tumor is suspected, imaging studies are used to visualize the brain’s internal structures. Magnetic Resonance Imaging (MRI) with a contrast agent is the preferred method for diagnosing a meningioma. The contrast dye, injected into a vein, makes the tumor appear brighter on the scan, allowing doctors to see its size, location, and relationship to nearby structures.
A Computed Tomography (CT) scan is another imaging technique that may be used to detect calcification within the tumor or changes in the adjacent skull bone. Although imaging provides a strong indication of a meningioma, a definitive diagnosis and the tumor’s grade require microscopic examination of a tissue sample obtained during surgery.
Approaches to Treatment
The treatment for a tentorial meningioma is tailored to the individual, considering the tumor’s size, location, symptoms, and the patient’s overall health. For small, asymptomatic tumors, observation is often the initial approach. This “watch and wait” strategy involves regular MRI scans to track any changes in the tumor’s size.
For tumors that are growing or causing significant symptoms, surgical removal is the most common treatment. In a procedure known as a craniotomy, a neurosurgeon creates an opening in the skull to access and remove the tumor. The primary goal is complete removal to reduce the likelihood of recurrence. Surgery in this region is complex due to the proximity of the brainstem, major veins, and cranial nerves.
When a tumor cannot be removed completely or for patients who are not surgical candidates, radiation therapy may be used. Stereotactic radiosurgery (SRS) is a focused form of radiation that delivers a high dose to the tumor while minimizing exposure to healthy brain tissue. It can be a primary treatment for smaller tumors or an additional therapy after surgery to target remaining cells.
Prognosis and Recurrence
The long-term outlook for a person with a tentorial meningioma is favorable, especially when the tumor is benign and treated effectively. The prognosis is tied to the tumor’s grade, which is determined by a pathologist examining the tissue. The World Health Organization (WHO) classifies meningiomas into three grades that indicate how quickly the tumor is likely to grow.
WHO Grade I tumors are the most common; they are benign and slow-growing. If a Grade I tumor is completely removed surgically, the prognosis is excellent with low recurrence rates. WHO Grade II tumors, known as atypical meningiomas, are more aggressive and have a higher likelihood of returning. WHO Grade III tumors are malignant, grow rapidly, and have the highest rate of recurrence.
The risk of recurrence is related to both the tumor’s grade and the extent of the surgical removal. If the entire tumor is removed, the chance of it returning is significantly lower. For tumors that are not completely removed or for higher-grade tumors, follow-up imaging is used to monitor for any signs of recurrence.