What is Intraventricular Meningioma?
Intraventricular meningiomas, which are types of brain tumors, have similar traits to the ones found outside the brain’s main mass (extra-axial space). Though they originate from identical cells, their location sets them apart. Meningiomas outside the brain come from the cells known as arachnoid cap cells, typically found near veins and the dural edges, which are the protective covering layers of the brain and spinal cord.
On the other hand, intraventricular meningiomas, those located within the brain’s ventricles—or fluid-filled spaces—come from a portion of the choroid plexus. The choroid plexus is a structure in the brain that creates the fluid that surrounds and cushions the brain and spinal cord. These tumors most often develop at a place called the tela choroidea.
The arachnoid cells seen here are due to the way the choroid plexus forms during embryonic development. Most meningiomas are slow-growing and considered benign (non-cancerous) by the World Health Organization (WHO), which they rate as grade I. However, some of these tumors can become atypical or anaplastic, which are more challenging types of tumors to treat.
What Causes Intraventricular Meningioma?
Most meningiomas, or tumors that start in the membranes around the brain and spinal cord, happen by chance, but they can also be linked to certain genetic conditions or mutations. Even those that happen spontaneously often involve a mutation on chromosome 22. This same mutation is also observed in a condition called neurofibromatosis type 2, which causes multiple schwannomas, meningiomas, and ependymomas, types of tumors. The alteration of chromosome 22q is found in 89% of meningiomas that occur in the brain’s ventricles, while 44% have chromosome 1p mutations.
Interestingly, up to 72% to 90% of these tumors have receptors for progesterone, a hormone. This might be the reason why women, especially during pregnancy when progesterone levels are high, are more likely to experience worsening symptoms of meningiomas. Additionally, these tumors also carry receptors for estrogen and androgen, other types of hormones—though less frequently for estrogen and more so for androgen.
Another established risk factor for developing meningiomas is exposure to ionizing radiation.
Risk Factors and Frequency for Intraventricular Meningioma
Meningiomas represent around 37% of primary tumors found in the central nervous system, and 50% of these are non-cancerous. These types of tumors are more common in females than males. However, when these tumors occur in the brain ventricles (cavities), they make up only 5% of all meningiomas. The most usual places for these tumors to appear are on the outer surface of the brain (convexity, 35%), by the top middle segment of the brain (parasagittal, 20%), the ridge at the base of the skull (sphenoid ridge, 20%) and other areas.
Ventricular meningiomas frequently occur in people aged between 30 and 60, and the average age of diagnosis is around 42 years. These tumors appear slightly more in women than men, although not as much as other meningiomas. They constitute around 1% to 5% of all tumors in the ventricles. About 90% of these are the least serious type of tumor (WHO grade I).
The most common place for these tumors is the lateral ventricle (88.4%), with fewer found in the fourth (8.7%) or third ventricle (2.9%). They can occur in any area of the ventricles that have choroid plexus (a network of blood vessels). The area where the temporal and occipital horns of the brain meet, often where these tumors are spotted, is known as the atrium. Some studies suggest these tumors are commonly detected on the left side of the brain.
In children, ventricular meningiomas are fairly common, showing up in around 20% of cases, usually diagnosed between the ages of 12 and 14. These are slightly more usual in boys than girls, and about 93.3% are classified as WHO grade I, signifying they are less severe. Compared to adults, children tend to have a higher percentage of benign subtypes of ventricular meningiomas.
Signs and Symptoms of Intraventricular Meningioma
Intraventricular meningiomas are usually benign, meaning they are not cancerous and grow very slowly. These meningiomas are typically discovered by accident or start to cause symptoms when they block the pathways for the cerebrospinal fluid causing a condition known as hydrocephalus. People with this condition will often experience recurring headaches that do not improve with over-the-counter medication, vision issues, or hydrocephalus. Occasionally, these growths can cause issues with attention and memory. It’s important to note that seizures are rare in these cases.
A persistent headache on one side is commonly seen in patients. This happens because of fluid build-up (edema) around the tissue near the meningioma. If doctors find this fluid in imaging studies, they might consider surgery because this could indicate that the growth could be malignant or imitating a cancerous meningioma.
Hydrocephalus, often mentioned as symptoms of increased fluid on the brain, can make the patient complain of headaches, nausea, blurry vision, excessive sleepiness, fatigue or even coma. In some severe conditions, patients may experience high blood pressure, a slow heartbeat, and irregular breathing which together form symptoms known as Cushing’s Triad. An examination of the eyes usually shows swelling of the optic nerve on both the sides. There can also be weakness or paralysis on one or both sides of the sixth cranial nerve.
A loss of vision in one of the quarters of the field of vision on the opposite side to the location of the lesion–known as contralateral homonymous quadrantanopia–can occur due to damage to adjacent optic radiations. Often, the visual loss is identified during an eye examination because the patient isn’t aware of the issue. Sometimes, they could complain about having trouble seeing objects in the top corner of the field of vision on the side opposite to the lesion.
Testing for Intraventricular Meningioma
When examining internal brain abnormalities, such as intraventricular lesions, the best method to use is a brain magnetic resonance imaging (MRI) scan with and without contrast. An intraventricular meningioma, a type of brain tumor, will appear on these scans as a distinct, solid mass that stands out against the other images. The mass can be the same intensity (iso-intense) or less intense (hypo-intense) than the surrounding tissues on T1 and T2-weighted images. When contrast enhancement is used, it appears evenly distributed.
In addition to a brain MRI, a head computed tomography (CT) scan and brain digital subtraction angiography (DSA) can provide more useful information. In a head CT scan, calcifications are easy to see. DSA allows doctors to identify the specific blood vessels feeding the tumor. In case of large tumors, they can be blocked off, known as embolization, before surgery. These tumors usually get their blood supply from the anterior choroidal artery. In bigger lesions, the posterior choroidal artery also contributes. Typically, these tumors have a high amount of blood vessels and drain into the deep ventricular veins.
Other types of brain imaging techniques like diffusion tensor imaging and functional MRI can help plan surgical procedures. These techniques help doctors see the white matter fiber tracts, the parts of the brain involved in transmitting nerve signals. This information can help surgeons decide the best surgical approach.
Treatment Options for Intraventricular Meningioma
Intraventricular meningiomas are usually non-cancerous, slow-growing tumors found in the brain. These tumors are often discovered by chance through brain MRI scans. As these tumors are deeply located within the brain, the surgical treatment can be quite challenging and occasionally comes with high risk.
Small tumors (less than 3cm) that don’t cause any symptoms are usually not removed immediately. Instead, they are closely monitored through regular brain MRI scans, which are typically done every six months for the first 1-2 years and then annually. However, if these small tumors start to cause symptoms or grow rapidly, different treatment methods might be considered.
In young, healthy individuals, large tumors (over 3cm) that don’t cause any symptoms are generally removed through surgery. The surgical removal of the whole tumor, if possible, is the recommended treatment since it has a high success rate and can confirm the diagnosis. Modern technology, called neuronavigation, can assist surgeons in planning and verifying the exact path they will take during the surgery.
If a tumor is hard to remove completely due to its location near blood vessels, steps to reduce the blood supply to the tumor through a process called embolization may be attempted before the surgery. If total removal is still not possible, a combination of a partial removal followed by radiation therapy is a safe alternative. For those who aren’t good surgical candidates, a needle biopsy might be performed to confirm the diagnosis, followed by radiation therapy.
Tumors causing symptoms like blockage of the fluid in the brain (hydrocephalus) or swelling of the brain tissue (edema) generally need to be fully removed through surgery. In emergency cases, a temporary drainage procedure may be used until surgery can take place.
The specific surgical approach varies depending on which part of the ventricles (fluid-filled structures in the brain) the tumor is located in, as well as the tumor’s size and spread.
Various techniques are used to gain access to the tumor depending on its location, but these surgical approaches sometimes carry risks of complications like vision problems or difficulties with language and calculation.
For example, the temporal horn of the lateral ventricle can be approached through a few different methods. The occipital horn of the lateral ventricle can be accessed using an approach that requires careful navigation. Similarly, the third and fourth ventricles require different surgical approaches depending on the tumor’s specific location.
In essence, the treatment plan for intraventricular meningiomas is very individual and depends on several factors, including the size of the tumor, its location in the brain, the patient’s overall health status, and whether the tumor is causing any symptoms.
What else can Intraventricular Meningioma be?
When examining a patient for brain-related issues, the healthcare provider could be considering various conditions. These might include:
- Choroid plexus papilloma, a slow-growing brain tumor.
- Choroid plexus carcinoma, a malignant brain tumor.
- Ependymoma, a type of brain tumor that can occur anywhere along the brain and spinal cord.
- Choroid plexus metastases, which involve the spread of cancer from other parts of the body to the choroid plexus in the brain.
- Renal cell carcinoma metastasis, where kidney cancer has spread to the brain.
- High-grade astrocytoma, a fast-growing brain tumor.
- Melanoma, a type of skin cancer that can sometimes spread to the brain.
- Primary central nervous system lymphoma, a rare form of brain lymphoma.
Each of these conditions requires a different treatment approach, making correct diagnosis crucial.
What to expect with Intraventricular Meningioma
Intraventricular meningiomas, a type of brain tumor, typically have a good prognosis, with 90% of them being classified as WHO grade I, which is a less aggressive form of this disease. Complete removal of the tumor through surgery usually leads to a full recovery. But some patients, about 10%, have a more aggressive form of intraventricular meningiomas (WHO grade II and III), and may need additional treatment such as radiosurgery. The mortality rate of these more aggressive cases is around 4%. Recurrence, meaning the tumor comes back, occurs in about 5.3% of the cases, but only 0.6% of these cases show an increase in the severity of the tumor (from WHO grade I to II/III).
In terms of long-term survival, 86% of patients lived up to five years without the disease getting worse. For those with the less aggressive type (WHO grade I), the 10-year survival rate is 84%. For those with more aggressive types (WHO grade II & III), the survival rate drops to 62% over ten years.
The recurrence and death rates for intraventricular meningiomas are generally lower because there’s often a higher success rate in completely removing the tumor through surgery.
Possible Complications When Diagnosed with Intraventricular Meningioma
Following brain surgery, a patient may develop epilepsy. This occurs when the operation affects the function of the local areas of the brain, which can disrupt the brain’s normal functioning.
Depending on the specific location approached during surgery, different symptoms may appear:
Approach through the dominant parietal lobe can result in:
- Gerstmann syndrome (a disorder of the inferior parietal lobule)
- Difficulty writing (Agraphia)
- Difficulty with calculations (Acalculia)
- Unable to identify their fingers (Finger agnosia)
- Confusion between left and right
Approach through the non-dominant parietal lobe can result in:
- Reading difficulty without writing difficulty (Alexia without agraphia)
Damage to the optic radiations, which are located on the floor and roof of the lateral ventricle, can cause:
- Loss of half the field of view on the opposite side of the body (Contralateral homonymous hemianopsia) or loss of a quarter of the field of view (quadrantanopia).
Moreover, there could be other complications such as:
- Bleeding within the brain (Intracerebral hemorrhage)
- Damage to a blood vessel, potentially leading to a stroke (Vascular injury and stroke)
- Excessive accumulation of fluid in the brain (Hydrocephalus)
- Blood clot in the lung (Pulmonary embolism)
- Surgical infection
- Loss of consciousness (Coma)
- Possible risk of death
Preventing Intraventricular Meningioma
Intraventricular meningiomas, which are tumors in the fluid-filled spaces (ventricles) of the brain, can’t be prevented. Many times, these tumors are discovered by chance during other medical procedures. Typically, these tumors can become quite large before they start causing symptoms. These tumors most commonly occur in people between 30 and 60 years old, with the average age being 42.2 years old – younger than those who get meningiomas in other parts of the brain. The nature and distribution of these tumors are comparable to those appearing elsewhere in the brain, although, they’re less likely to come back or prove fatal.
Surgery to remove these tumors can be quite complicated. Nonetheless, complete removal is often possible, and it’s here where the chances of these tumors coming back are typically minimal. However, some patients might experience neurological issues, particularly concerning vision. To improve surgical outcomes, doctors use advanced imaging techniques like functional brain mapping, diffusion tensor imaging, and white matter tractography. These methods help doctors to determine the best way to approach the surgery.
