Meningiomas are the most common primary intracranial tumors. They are generally benign and slow-growing, although as many as 10% can be more aggressive and faster-growing in nature.
Remember that the three meningeal layers include the pia, the arachnoid, and the dura. Meningiomas grow from the arachnoid layer. Because the arachnoid layer surrounds the entire central nervous system, meningiomas can be found anywhere in the head and spinal canal—including the ventricles.
Rather than growing from within the brain tissue, meningiomas tend to invaginate into and compress the surrounding brain. Meningiomas are thus known as extrinsic (or extra-axial) brain tumors.
Meningiomas generally occur later in life (usually in the sixth decade and beyond) and are more common in women. However, they can be occasionally found in younger patients and even rarely in children.
Meningiomas are more common in patients with neurofibromatosis, which is a genetic disorder that leads to nervous system tumors. They are also more commonly found in patients who have received radiation treatments to the head.
When should you consider meningioma as a possible diagnosis?
Signs and symptoms
Patients with a meningioma often first present with a new-onset seizure due to irritation of the adjacent brain. Up until the onset of the seizure, the patient may have been totally asymptomatic.
Patients with a meningioma may also present with progressive focal neurological deficits due to local compression of eloquent brain tissue. Because meningiomas can be found anywhere, these deficits can vary widely. For example, a meningioma compressing Broca’s area may cause speech deficits. Compression of the motor cortex can cause weakness in a group of muscles on the opposite side of the body, and compression of the spinal cord can cause paraparesis.
Because meningiomas are often very slow growing, many are asymptomatic and discovered by accident. The patient may undergo imaging of the brain for an unrelated reason and be found to have an extra-axial tumor consistent with a meningioma. In accidentally discovered tumors, one third show no growth over several years.
Some meningiomas can grow to tremendous sizes without any symptoms. This is particularly true for tumors growing into or under the frontal lobes. Given time, these patients may begin to show cognitive difficulties, but these can be quite subtle. Some patients may complain of headaches, but these are nonspecific. The headaches may be unrelated to the meningioma or due to increased intracranial pressure. Sometimes an ophthalmoscopic exam may show papilledema (evidence of increased intracranial pressure).
What to do if you suspect meningioma?
Evaluating a patient with a new-onset seizure or progressive focal neurological deficits will involve a thorough history, a physical examination, and a neurological exam. Eventually, the evaluation will lead to magnetic resonance imaging (MRI) of the brain.
On MRI, meningiomas are usually clearly discernable from normal brain tissue. However, they tend to be of the same intensity as the surrounding brain on non-contrast T1- and T2-weighted images.
Most meningiomas will enhance (e.g., become very bright) with the administration of intravenous contrast, so a meningioma will appear much brighter on a T1-weighted post-contrast MRI in comparison to a pre-contrast MRI.
When reviewing a meningioma on MRI, measure the tumor size at its greatest diameters. Look for associated brain compression, distortion, and associated shift of midline structures.
Also, look for a line of enhancement immediately adjacent to the tumor along the dura. This is known as a dural tail and is a common finding with meningiomas.
When examining the patient’s MRI, look for associated brain edema nearby. Edema will appear hyperintense on T2- and proton-weighted images and will show up as a brighter area of brain tissue surrounding the tumor.
On computed tomography (CT), there is often calcification in the tumor. Also, the adjacent skull may appear thickened and more dense than normal.
How do you treat meningiomas?
Anticonvulsants for meningioma-associated seizures
Small meningiomas causing no neurological deficits with no associated brain edema do not require surgery—even if the patient presents with seizures. If the patient did present with seizures, go ahead with a trial of anticonvulsants, and follow the tumor with imaging. Currently, oral levetiracetam (500–1 000 mg twice a day) is commonly employed.
Follow up regularly with MRI to monitor growth
If the tumor is to be monitored, repeat an MRI in four months to rule out rapid growth and then repeat yearly for several years. If the tumor shows no growth, no treatment is indicated.
Surgical resection for large, symptomatic meningiomas
Tumors that are large or are causing neurological deficits should be surgically resected. Resection can be curative, although this depends on the aggressiveness of the resection, such as the removal of the surrounding meninges.
Given enough time (e.g., decades), slow recurrence of the tumor is not uncommon—even when an aggressive resection has been achieved. As a result, these patients will need to be followed long-term.
In the hands of an experienced neurosurgeon, morbidity and mortality for tumor resection are quite low. However, some meningiomas can be quite a technical challenge due to their size, location, or critical structure involvement (e.g., vessels and cranial nerves). In these situations, morbidity can be substantial.
Particularly challenging are meningiomas found at the base of the skull. Although benign in nature, large tumors of the skull base can cause severe morbidity and death if not addressed. Many neurosurgeons specialize in surgery involving tumors of the skull base. Some of these tumors lend themselves to minimally invasive techniques, but others require radical approaches.
Under certain circumstances, stereotactic radiation has been used to treat meningiomas (or their postoperative residuals). But, it is not considered the best primary treatment for meningiomas. Stereotactic radiation may slow or stop tumor growth, but seldomly shrinks the tumor.
What happens after surgery for a meningioma?
Tumor pathology will be studied post-surgery, and subtypes that have a high risk of rapid recurrence will need close follow up and potentially adjuvant therapy. This will be determined by the neurosurgeons and neuro-oncologists. In general, no further treatment is indicated after an extensive resection. Obtain a follow-up MRI every year after tumor resection to screen for recurrence.
When seeing patients after a recent meningioma resection, look out for certain phenomena:
- Breakdown and infection of the wound
- Postoperative seizures
- Acute illness
- Hypo-adrenal crisis
Breakdown and infection of the wound
Check the wound routinely for any evidence of breakdown and infection.
Postoperative seizures are not uncommon, and patients will often be placed on anticonvulsants whether they had experienced seizures or not. These are often maintained for 6–12 months post-surgery. They can be discontinued if the patient remains seizure-free, but always obtain an electroencephalogram (EEG) before stopping anticonvulsants—particularly if the patient originally presented with seizures.
It is also not uncommon for patients to experience breakthrough seizures. Make sure you ask specifically about this in follow-up appointments. Anticonvulsant levels should be regularly checked. Also, check levels when indicated based on the patient’s signs and symptoms (such as breakthrough seizures or signs of toxicity).
Keep in mind that not all anticonvulsants have standard assays for serum levels. For example, phenytoin and sodium valproate levels are routinely assayed, but levetiracetam levels are not. If a patient experiences multiple breakthrough seizures (and anticonvulsant dosing and blood levels are appropriate), consider adding a second anticonvulsant or switching agents. Don’t be afraid to discuss this with the patient’s surgeons or consult neurology for assistance, since these seizures can be refractory.
Patients will often be given high dose corticosteroids in the perioperative period to combat brain swelling. However, this can suppress their natural corticosteroid production from the hypothalamic-pituitary-adrenal axis.
Patients will usually undergo a prolonged tapering of corticosteroids until they are discontinued. If the patient gets sick during this period (e.g., with a cold or flu), they may need a boost in the steroids to what is called stress dose levels. In this case, contact endocrinology specialists for recommendations on dosing.
For several months postoperatively, patients may present with a hypo-adrenal crisis if their adrenal function was significantly suppressed by steroid therapy. A hypo-adrenal crisis can be deadly.
Keep hypo-adrenal crisis in mind if a patient presents with unexplained changes in mental status and high fever weeks to a few months post-surgery. These patients will need to be emergently admitted and given stress dose corticosteroids until they stabilize. Thankfully, this is unusual and can be minimized by ensuring that the patient goes through an appropriate tapering off period of their perioperative steroids.
Patients may experience a frightening amount of scalp and facial swelling and bruising at or near the craniotomy site. This can last for weeks or even months. Advise sleeping with an elevated head and encourage patience. Most times the swelling is self-limited.
Ensure that the swelling is evaluated by the patient’s surgeon at some juncture. If a subcutaneous fluid collection seems to be continuously expanding, notify the patient’s neurosurgeon. Subcutaneous fluid collection can indicate developing hydrocephalus.
Meningitis or other infections
Do keep in mind the possibility of postoperative meningitis in the initial period after surgery. Keep an eye out for fever and meningeal signs.
What are some other important considerations to be aware of after a meningioma resection?
Patients will frequently experience headaches for many months after surgery. Avoid narcotic medications. Nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen often work well for postoperative headaches.
Patients who have experienced neurological deficits in the course of their disease should undergo aggressive multidisciplinary therapy over an extended period. Some may come to you after an extended period in a rehabilitation facility. Encourage daily exercise and continued work on activities of daily living (ADLs). Connect them with outpatient physical therapists and monitor their progress in activities of daily living.
Cognition and mental health
Patients often complain of cognitive slowing after surgery. This will improve with time. Reassure them and be prepared to support an extended absence from work. If the patient is particularly affected, consider baseline and follow-up evaluations with neuropsychologists.
Depression is also common after surgery. Consider prescribing selective serotonin reuptake inhibitor (SSRI) medications. If the patient’s depression is profound, seek psychiatric assistance.
In general, patients with meningiomas fare very well and are eventually delighted that they avoided a potentially disastrous disease progression. However, remind them that they should keep up with healthy habits, follow up routinely, and undergo imaging of the brain every year.
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- Cappabianca, P, Solari, D. 2018. Meningiomas of the Skull Base: Treatment Nuances in Contemporary Neurosurgery. 1st edition. New York: Thieme Medical Publishers Inc.
- Goldbrunner, R, Minniti, G, Preusser, M, et al. 2016. EANO guidelines for the diagnosis and treatment of meningiomas. Lancet Oncol. 17: e383–e391. PMID: 27599143
- Haddad, G, and Turkmani, A. 2020. Meningiomas. Medscape. https://emedicine.medscape.com/
- Traylor, JI and Kuo, JS. 2020. Meningiomas. American Association of Neurological Surgeons. https://www.aans.org/