Petroclival meningioma is a benign and slow-growing tumor that occurs deep within the center of the skull base, which is a very difficult location to reach surgically. Patients may experience headaches, double vision, hearing loss, dizziness, facial pain or numbness, facial weakness, and loss of coordination.
Treatment options include observation in incidental cases, surgery, radiation, or a combination of these options. Because of the location of this tumor and its proximity to critical structures, surgical tumor removal is challenging. However, advances in microsurgical techniques and radiation therapies have greatly improved patient survival and outcomes.
What Is a Petroclival Meningioma?
Petroclival meningioma is a benign and slow-growing tumor that arises from the outer covering of the brain (meninges) and is located deep within the skull base. Because these tumors often grow slowly and might not cause symptoms for years, they can be large by the time they are diagnosed. The tumor can press on critical nearby structures such as the brainstem, cranial nerves, and major blood vessels and cause symptoms.
Figure 1. A petroclival meningioma (bright white) sitting at the base of the skull.
What Are the Symptoms?
Headache is the most common symptom, but patients can also experience double vision, hearing loss, dizziness, facial pain (trigeminal neuralgia) or numbness, facial weakness or muscle spasms, loss of coordination, and difficulties speaking or swallowing.
What Are the Causes?
The cause of petroclival meningiomas is not currently known. Risk factors include previous radiation treatment to the head and certain inherited disorders such as neurofibromatosis 2.
How Common Is It?
Meningiomas are the most common brain and nervous system tumor, comprising 40% of tumors overall. However, only 2% of these tumors are petroclival meningiomas. Benign meningiomas are 2.3 times more common in females than in males and more commonly affect older adults aged 40 to 70 years.
How Is It Diagnosed?
Petroclival meningiomas are usually diagnosed by magnetic resonance imaging (MRI). Computed tomography (CT) is used to evaluate the anatomy of the underlying skull before surgery and to view the composition of the tumor. Angiography and venography are performed also to observe the course of large vessels that should be protected during surgery.
What Are the Treatment Options?
Petroclival meningiomas are treated primarily with surgery and radiotherapy, but observation might be preferred for incidental tumors that do not produce symptoms.
Patients who have no symptoms but are incidentally diagnosed might be observed over time.
Surgery for petroclival meningiomas is often recommended if a patient suffers from neurologic deficits or if tumor growth is observed. Although surgery is a curative treatment option, aggressive removal can result in damage to nearby vulnerable nerves and blood vessels and lead to permanent neurologic effects.
If the tumor is in a particularly sensitive location, the surgeon might plan to leave some tumor behind. This residual tumor can be treated with stereotactic radiosurgery. The patient then must undergo regular MRI follow-up to ensure that the tumor is not growing. After surgery, the patient is observed in the intensive care unit overnight. Depending on the complexity of the surgery, the patient might stay for 1 week or longer in the hospital.
The surgical approach depends on the specific location of the tumor but is generally classified as either anterior (closer to the eyes) or posterior (closer to the back of the head) petrosectomy. Both approaches involve removing pieces of the petrous (“rock-like”) part of the temporal bone near the ear. Your surgeon will discuss the specific surgical approach to be used for you.
Figure 2. Patient positioning for an anterior (top left) or posterior (top right) petrosectomy. (Bottom) The tumor is carefully removed from surrounding nerves and blood vessels.
Due to their location, surgical removal of petroclival meningiomas is challenging. Despite significant improvements in surgical technique and safety of this procedure, 30% to 40% of patients can have at least temporary cranial nerve dysfunctions after surgery, which commonly manifest as double vision, facial weakness, and difficulty swallowing or chewing. Other possible complications include cerebrospinal fluid leak, a buildup of fluid within the brain (hydrocephalus), and infection.
Radiation is another option for treating petroclival meningiomas and is often used in combination with surgery. There are 2 ways to delivery this treatment—radiosurgery, in which a large dose of radiation is aimed at the tumor, and fractionated radiotherapy, in which multiple small doses of radiation are delivered over several weeks. These procedures are noninvasive and require no hospital stay for recovery.
During radiosurgery, hundreds of small, concentrated beams of radiation are aimed at the tumor with 1 of the 3 currently available radiosurgical devices—Gamma Knife, Cyber Knife, or Novalis. The procedure itself takes 30 to 50 minutes, and the patient is placed in a stereotactic headframe on the day of the procedure, which stabilizes the patient’s head and enables the treatment team to calibrate the machine to the patient’s head and tumor. This treatment is used in rare cases in which the tumor is well separated from surrounding sensitive structures and might be better for smaller petroclival meningiomas.
The patients who undergo fractionated radiotherapy receive smaller doses of radiation over several visits. Each visit takes only 5 to 15 minutes, and the patient is able to go about his or her business before and after the visit. Fractionated radiotherapy can be performed for residual and recurrent petroclival meningiomas.
It is important to note that radiation therapy does not remove the tumor. It can, in some cases, cause it to shrink. The main goal of radiation is to stop the tumor from growing. As a result, the patient must return for MRI scans on a yearly basis to check for any new growth.
Possible complications of radiation therapy include visual loss and hormone abnormalities. Radiation-induced optic neuropathy is a late complication of radiotherapy that results in sudden, painless vision loss in one or both eyes. This is rare but can occur months to years after treatment.
What Is the Recovery Outlook?
The current survival rate for patients with a petroclival meningioma is favorable, with progression-free survival at approximately 80% at 10 years. However, complications such as double vision and facial weakness can decrease a patient’s quality of life. Recurrent tumors can be treated with radiation. A multidisciplinary team of specialists in oncology and ophthalmology may be involved to maximize and maintain patient wellness after treatment.
Cerebrospinal fluid—clear fluid surrounding the brain and spinal cord
Meninges—outer membranous covering of the brain and spinal cord
Contributor: Gina Watanabe BS
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