Skull Base Chordoma

Skull Base Chordoma: Symptoms, Causes, Types, Diagnosis, and Treatments

Skull base chordoma is a rare and challenging tumor arising at the base of the skull, often affecting critical structures near the brainstem and nerves. This slow-growing but locally aggressive cancer can cause serious neurological problems if not diagnosed and treated properly. In this comprehensive guide, we will explore the symptoms, causes, types, diagnosis, and treatment options for skull base chordoma, equipping you with a clear understanding of this complex condition.

What is Skull Base Chordoma?

Chordomas are rare, malignant tumors originating from remnants of the notochord — a primitive structure present during embryonic development that normally disappears before birth. When notochordal cells persist abnormally, they may transform into chordomas. These tumors can develop anywhere along the spine, but the skull base (clivus region) and sacrum are the two most common sites.

Skull base chordomas arise at the base of the skull near the clivus bone — the slope of bone just in front of the brainstem. Because of their location, they can compress vital nerves and brain structures, leading to various neurological symptoms. Though slow growing, these tumors are locally invasive and have a tendency to recur, posing significant treatment challenges.

Epidemiology and Risk Factors

• Chordomas account for about 1-4% of all primary bone tumors.
• Skull base chordomas are rarer compared to sacral chordomas.
• They mostly affect adults between 40 and 70 years old but can occur at any age.
• No clear environmental or hereditary risk factors have been conclusively identified.
• Slight male predominance is noted.
• Some studies suggest genetic mutations (e.g., in the T gene or brachyury gene) may predispose individuals.

Symptoms of Skull Base Chordoma

Because the tumor grows near the brainstem and multiple cranial nerves, symptoms often relate to nerve compression and increased pressure inside the skull. Symptoms typically develop gradually due to the tumor’s slow growth.

Common Symptoms

• Headaches: Often persistent and localized near the forehead or back of the head.
• Visual disturbances: Double vision, blurred vision, or loss of vision caused by pressure on the optic nerves.
• Facial numbness or weakness: Compression of the trigeminal nerve may cause facial pain, numbness, or muscle weakness.
• Difficulty swallowing or speaking: Involvement of cranial nerves IX, X, and XII can affect swallowing, speech, and tongue movement.
• Hearing loss or tinnitus: When the tumor affects nerves near the ear.
• Balance and coordination problems: Tumor pressure on the brainstem can cause dizziness, unsteadiness, or difficulty walking.
• Other cranial nerve palsies: Including eyelid drooping (ptosis), facial muscle weakness, or difficulty moving the eyes.

Advanced Symptoms

• Hydrocephalus: Blockage of cerebrospinal fluid pathways leading to increased intracranial pressure.
• Severe neurological deficits: If the tumor compresses the brainstem or vital arteries.

Because these symptoms overlap with other neurological disorders, skull base chordomas are often initially misdiagnosed or detected late.

Causes and Pathophysiology

Origin of Chordomas

Chordomas arise from notochordal remnants that fail to regress during fetal development. These cells have the potential for abnormal proliferation, leading to tumor formation.

Molecular and Genetic Factors

• Brachyury gene (T gene): Overexpression or mutation of this transcription factor is strongly linked to chordoma development. Brachyury is essential for notochordal cell survival and differentiation.
• Other genetic alterations: Involving genes controlling cell growth and apoptosis may contribute.

Why Skull Base?

The notochord extends from the base of the skull to the coccyx. Remnants located near the clivus region can give rise to skull base chordomas, which grow within the bone and can invade adjacent tissues.

Risk Factors

There are no well-established external risk factors like smoking or radiation exposure. Research continues into the role of genetic susceptibility.

Types of Skull Base Chordoma

Chordomas are classified based on their histological features. Understanding the type helps predict tumor behavior and tailor treatment.

Conventional (Classic) Chordoma

• Most common type.
• Comprised of physaliphorous cells (cells with bubbly cytoplasm).
• Shows moderate nuclear atypia.
• Slow growing but locally aggressive.
• Tends to recur after treatment.

Chondroid Chordoma

• Contains cartilage-like (chondroid) areas.
• Typically found in the skull base region.
• Generally has a better prognosis than conventional chordoma.
• Histologically resembles both chordoma and chondrosarcoma.

Dedifferentiated Chordoma

• Rare and aggressive variant.
• Shows high-grade sarcomatous components alongside typical chordoma cells.
• Associated with rapid growth, metastasis, and poor prognosis.

Diagnosis of Skull Base Chordoma

Diagnosing skull base chordoma requires a combination of clinical evaluation, imaging studies, and tissue biopsy.

Clinical Examination

• Detailed neurological examination focusing on cranial nerve function.
• Assessment of visual acuity, facial sensation, swallowing, and hearing.

Imaging Studies

Magnetic Resonance Imaging (MRI)

• Preferred imaging modality.
• Shows tumor location, size, and involvement of adjacent soft tissues.
• Tumor appears as a lobulated, well-defined mass, often with heterogeneous signal intensity.
• T2-weighted MRI usually reveals high-intensity signal.
• MRI helps in surgical planning.

Computed Tomography (CT) Scan

• Provides detailed bone anatomy.
• Demonstrates bony destruction or erosion of the clivus.
• Useful in preoperative planning.

Positron Emission Tomography (PET)

• Sometimes used to assess tumor metabolic activity and detect metastasis.

Biopsy and Histopathology

• Tissue biopsy confirms diagnosis.
• Histological examination reveals characteristic physaliphorous cells.
• Immunohistochemical staining is positive for:
  • Brachyury (specific marker)
  • Cytokeratins
  • S-100 protein

Differential Diagnosis

• Chondrosarcoma (especially the chondroid variant)
• Meningioma
• Metastatic tumors
• Pituitary adenoma

Treatment of Skull Base Chordoma

Treating skull base chordoma is complex due to the tumor’s proximity to critical brain structures and its tendency to recur. A multidisciplinary approach involving neurosurgeons, radiation oncologists, and medical oncologists is essential.

Goals of Treatment

• Maximal safe tumor removal.
• Preservation of neurological function.
• Prevention of recurrence.
• Control of symptoms.

Surgery

Surgical resection is the primary treatment modality.

• Objective: Achieve gross total resection while minimizing neurological damage.
• Approaches vary based on tumor location and size:
  • Endoscopic endonasal approach (through the nose)
  • Transcranial approaches (through the skull)
• Complete removal can be difficult due to tumor infiltration into critical structures.
• Surgery may be staged or combined with other therapies.
• Risks include cranial nerve deficits, cerebrospinal fluid leaks, and infection.

Radiation Therapy

Radiation plays a crucial role, especially after subtotal resection or for inoperable tumors.

• Proton Beam Therapy: Preferred due to its ability to deliver high doses to the tumor with minimal damage to surrounding tissues.
• Photon-based Radiotherapy: Used where proton therapy is unavailable.
• Stereotactic Radiosurgery (Gamma Knife): May be used for small residual tumors.
• Radiation reduces recurrence rates and improves local control.

Therapy

Currently, there is no established chemotherapy for chordoma.

• Some experimental treatments target molecular pathways:
  • Tyrosine kinase inhibitors (e.g., imatinib)
  • Other targeted agents are under clinical trials.
• Medical therapy is mainly palliative or for recurrent/metastatic cases.

Follow-Up and Monitoring

• Lifelong monitoring is necessary due to the high risk of recurrence.
• Regular MRI scans every 6 to 12 months.
• Assessment of neurological status and symptom changes.

Prognosis

• Prognosis depends on the extent of resection, tumor type, and response to radiation.
• Five-year survival rates range from 50-80%.
• Recurrence is common and may require repeat surgery or radiation.
• Dedifferentiated chordomas have a poorer prognosis.
• Early diagnosis and complete surgical removal improve outcomes.

Living with Skull Base Chordoma

• Patients often need rehabilitation for neurological deficits.
• Psychological support is vital due to the tumor’s chronic nature.
• Multidisciplinary care teams provide the best support.

Summary

Skull base chordoma is a rare, slow-growing but aggressive tumor arising from notochordal remnants near the base of the skull. Its location near vital brain structures leads to diverse neurological symptoms including headaches, vision problems, and facial numbness. Diagnosis relies on imaging and biopsy. Treatment is challenging and involves surgery and radiation, especially proton therapy, to control growth and prevent recurrence. Advances in molecular biology may lead to new targeted therapies in the future. Early diagnosis and a coordinated multidisciplinary approach are key to improving patient outcomes.

Frequently Asked Questions (FAQs) About Skull Base Chordoma

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