Chondrosarcoma of the brain is a rare, slow-growing cancerous tumor that arises from cartilage-producing cells. These tumors develop at the base of the skull where bone and cartilage meet, most often in the clivus or the sphenoid bone. The exact cause is not fully understood, but they may originate from cartilage cells left over from embryonic development. Affecting about one in a million people, this cancer is most commonly seen in adults between the ages of 40 and 70.
Symptoms and Associated Conditions
The symptoms of a skull base chondrosarcoma result from the tumor pressing on adjacent cranial nerves and brain structures. The specific neurological issues a person experiences depend on which parts of the brain are compressed, affecting both sensory and motor functions.
Common symptoms can include:
- Vision disturbances such as double vision or a partial loss of sight
- Hearing loss or tinnitus (ringing in the ears)
- Persistent headaches, facial pain, or numbness
- Difficulty with balance and coordination
- Trouble swallowing
While most chondrosarcomas develop spontaneously, they are sometimes linked to rare genetic conditions that increase risk. The two primary associated conditions are Ollier disease and Maffucci syndrome. Both are characterized by the growth of multiple benign cartilage tumors, called enchondromas, within the bones. Maffucci syndrome is distinguished by the additional presence of benign vascular growths. Malignant transformation of these enchondromas into chondrosarcomas is a known complication of both disorders.
The Diagnostic and Grading Process
Diagnosing a chondrosarcoma of the skull base involves detailed imaging tests. Both Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans are used to identify the tumor’s size, location, and characteristics. An MRI is effective for showing the tumor’s extent and its relationship to soft tissues, while a CT scan provides a clearer view of the bone and any calcification.
While imaging can suggest a chondrosarcoma, a biopsy is required for a definitive diagnosis. During this procedure, a small sample of tumor tissue is surgically removed and examined by a pathologist. This histological analysis confirms the diagnosis and is also used to determine the tumor’s grade.
Tumor grading classifies the cancer based on how quickly the cells are likely to grow and spread. Grade I tumors are low-grade; their cells look more like normal cartilage and grow slowly with a low risk of spreading. Grade II tumors are intermediate, and Grade III tumors are high-grade, appearing more abnormal and behaving more aggressively.
Standard Treatment Protocols
The standard treatment for chondrosarcoma of the skull base is a combined approach of surgery followed by radiation therapy. The objective of surgery is to achieve a complete resection, meaning the entire tumor is removed. Skull base surgery is complex due to the tumor’s proximity to cranial nerves, the brainstem, and major blood vessels. These operations are often performed by specialized neurosurgeons using minimally invasive techniques.
Following surgery, radiation therapy is recommended to destroy any cancer cells that may have been left behind. Proton beam therapy is often preferred for skull base tumors over traditional radiation. This form of radiation delivers a highly precise dose directly to the tumor, minimizing damage to surrounding healthy brain and spinal cord tissues.
Proton therapy treatments are administered five days a week for up to eight weeks. The process is non-invasive and painless, allowing many patients to continue with their daily activities. Traditional chemotherapy is not an effective treatment for the slow-growing chondrosarcoma and is rarely used.
Prognosis and Recovery
The long-term outlook for an individual with a skull base chondrosarcoma is tied to the success of the surgical removal and the tumor’s grade. Patients with low-grade (Grade I) tumors that are completely resected during surgery have a positive long-term prognosis, with a 5-year survival rate of around 90%.
Despite successful treatment, the tumor can recur, sometimes many years later. The treatment approach influences this risk. For patients who undergo surgery alone, the 5-year recurrence rate can be as high as 44%. Adding radiation therapy can lower this rate to approximately 9%.
Because of the risk of recurrence, long-term follow-up care is a necessary part of recovery. This involves regular monitoring with MRI scans to detect any signs of the tumor returning. Early detection allows for prompt intervention if the tumor does come back.