Clival tumors are growths on the clivus, a portion of bone at the base of the skull. When clival tumors grow, they may invade and damage important nearby structures: cranial nerves, the internal carotid arteries and the brainstem, for example. The most common surgical treatments for tumors of the clivus are craniotomy and transsphenoidal surgery. At Columbia’s Skull Base Tumor Center, our neurosurgeons specialize in providing care for patients with clival tumors.
Two types of tumors grow in the clivus: chordomas and chondrosarcomas.
Chordomas are rare, benign tumors that arise from cells that were once part of an embryonic structure called a notochord. Normally, notochord remnants form part of the intervertebral discs. A chordoma occurs when additional notochord cells are enclosed by the developing bones.
Chordomas in the skull have a slow-growing nature and are typically benign. Despite their mild behavior, however, they can still cause significant damage by invading nearby structures. Chordomas tend to recur after treatment.
The second type of clival tumor, chondrosarcoma, is even rarer. Chondrosarcomas are slow-growing tumors that arise in cartilage. (During development, the cartilage in the skull eventually hardens and is replaced by bone.) Although chondrosarcomas are malignant, they rarely spread to other areas. Like chordomas, chondrosarcomas tend both to invade nearby structures and to recur after treatment.
Since both tumor types grow in the clivus and may affect nearby structures, their symptoms are very similar.
Chordomas may cause headaches and diplopia. Larger tumors tend to affect speech, voice, facial feeling and the ability to swallow. Sometimes large tumors block the flow of fluid that bathes and cushions the brain, which can lead to a condition called hydrocephalus.
The most common symptoms of chondrosarcoma are headache, vision changes, and hearing changes.
A neurological examination is usually conducted to identify any problems. This exam includes evaluation of eye movements, hearing, sensation, motor function, swallowing, sense of smell, balance, and coordination.
Imaging studies are key to diagnosing clival tumors.
Plain X-ray, computed tomography (CT) scan and magnetic resonance imaging (MRI) can be used to visualize the tumor. MRI is the preferred method due to its abilities to differentiate chordomas and chondrosarcomas from meningiomas, and to reveal the extent to which the tumor has invaded brain tissue. MRI or CT scans may be performed with or without contrast enhancement.
Biopsy is required to confirm a diagnosis of chordoma or chondrosarcoma. The tissue sample may be removed either before surgery or as part of the tumor removal surgery.
As with most brain tumors, the cause of clival tumors is not well understood.
Chordomas make up about 0.2 percent of primary brain tumors. They are slightly more common in men, and they typically arise in people between the ages of 40 and 70, but they can occur at any age.
Most chordomas occur sporadically and are not inherited. However, some genetic basis seems likely as individuals with the rare genetic condition tuberous sclerosis complex have a greater likelihood of developing a chordoma. The gene brachyury is also believed to play a part in chordoma; most people who have a chordoma have a slight change in this gene. There are many people, however, who have the identical gene change and never develop a chordoma. Research in this area is ongoing.
Chondrosarcomas tend to occur in older adults and occur slightly more often in men than women. Individuals with certain rare conditions like Ollier disease, Maffucci syndrome, and Paget disease are more likely to develop chondrosarcomas.
Historically, clival tumors have been difficult to treat because they are located at the skull base. Surrounded by and filled with crucial structures, the skull base is considered an exceedingly hard-to-reach location.
At Columbia, our neurosurgeons use the latest surgical techniques to reach and treat these difficult tumors, providing the best possible results. Whenever possible, our surgeons perform a radical resection, removing the entire clival tumor along with its blood supply. It is not always possible to determine before surgery whether a total resection will be possible, and many surgical decisions must be made during the surgery itself. Our experienced neurosurgeons remove as much of the tumor as safely possible, while also preserving brain tissue and overall function.
Advances in the field of skull base surgery allow neurosurgeons to remove clival tumors in one of two ways: craniotomy or transsphenoidal surgery. During a craniotomy, a neurosurgeon removes part of the bony skull. Then, using the tools and techniques of microsurgery, the neurosurgeon exposes and removes the tumor.
During transsphenoidal surgery, the neurosurgeon accesses the tumor through the nose. This procedure is commonly performed using an endoscope, which the surgeon navigates into the nostrils, through the nose and eventually to the clival tumor. The neurosurgeon uses other specialized instruments to remove the tumor, withdrawing it through the nose.
Clival tumors do not generally respond to chemotherapy, and it is rarely used.
Radiation therapy may be used after surgery, especially in cases of subtotal resection. Even with radiation therapy, clival tumors may recur, requiring additional surgery or radiation therapy.