Made up of 29 bones, the skull is essential for protecting the brain from injury. At the bottom, there lies a skull base, which acts as the floor for connecting the brain to the rest of the body via nerves and blood vessels.
Unfortunately, the skull base can also be the site of an uncontrolled, abnormal growth called a tumour.
And while brain tumours are already one of the most frightening diagnoses a doctor can give, skull base tumours—though rare—are among the deadliest.
Skull Base: Explained
The skull base can be defined as the floor of the cranial cavity, the bone which supports the brain. Beginning from the anterior side, skull base constitute the following bones, which are separated from each other by sutures-
- Frontal bone
- Ethmoid bone
- Sphenoid bone
- Temporal bones
- Occipital bone
- Parietal bones
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Skull Base Tumours: Overview
Skull base tumours are a form of rare tumour that may arise within the base of the cranium or between the brain and base of the skull. They are called meningitis.
Skull base tumours can be both benign and malignant.
Some of the common examples of skull base tumours include
- Schwannomas: These are benign tumours that arise from the cells that surround the nerves known as schwann cells. They are often slow-growing and can be surgically removed.
- Meningiomas: These benign tumours originate from the meninges, the protective membranes surrounding the brain and spinal cord. They can be surgically removed or treated with radiation therapy.
- Chordomas: These rare, slow-growing tumours develop from remnants of the notochord, a structure that forms the backbone during embryonic development. They are often surgically removed.
- Chondrosarcomas: These are malignant tumours that arise from cartilage cells. They can be slow-growing or fast-growing, and treatment may involve surgery, radiation therapy, or chemotherapy.
- Endolymphatic Sac tumours (ELSTs): These rare, benign tumours develop in the endolymphatic sac, a fluid-filled sac located near the inner ear. They can cause hearing loss and dizziness.
- Craniopharyngiomas: These benign tumours arise from remnants of Rathke’s pouch, a structure that helps form the pituitary gland. They can cause hormonal imbalances and vision problems.
- Carcinomas: These are malignant tumours that arise from epithelial cells, which line the surfaces of organs and tissues. They can be divided into various types, such as squamous cell carcinoma and adenocarcinoma.
- Neuroblastomas: These are malignant tumours type that originate from immature nerve cells. They are most common in children, and treatment may involve surgery, chemotherapy, and radiation therapy.
Once these tumours start growing in size, they start putting pressure on vital structures present in the brain, such as the optic nerve and the carotid arteries. If not checked on time, they severely damage the brain and affect the functioning of the body.
Common Causes and Risk Factors
Neurosurgeons have suggested that the cause of the skull base tumours is idiopathic, which means the exact cause is still unknown
Genetic causes
Some genetic disorders, such as Neurofibromatosis Type 2 (NF2), predispose individuals to the development of acoustic neuroma and other nerve sheath tumours. Another example is Familial Isolated Pituitary Adenoma (FIPA), a rare genetic condition that increases the risk of developing pituitary adenomas.
Environmental factors
- Much evidence has suggested that patients who have been previously exposed to radiation to treat head, neck, or brain cancers, have an increased risk of developing skull base tumours.
- Chemical exposure: Some chemicals, such as vinyl chloride, arsenic, and herbicides, have been linked to an increased risk of nasal cancers, which can sometimes involve the skull bases.
Skull base tumours: Symptoms and Diagnosis
A frequently asked question is: Can the symptoms of skull base tumours be detected early? Below are some of the early symptoms of skull base tumours.
- Altered sense of smell
- Blurred vision
- Difficulty breathing
- Headaches
- Hearing loss
- Loss of balance
- Memory loss
- Nausea and vomiting
- Nose bleeds
- Trouble swallowing
The challenge is that these symptoms typically emerge gradually, making them easy to overlook or misinterpret. As the tumour grows, however, these signs can become more pronounced and aggressive, heralding a severe underlying issue.
Some of the complications associated with skull base tumours which should never be overlooked are as follows:
- Pressure on adjacent nerves and blood vessels—As the tumour grows, it exerts pressure on nearby cranial nerves. This pressure can lead to pain, neurological problems, and symptoms such as facial numbness.
- Disruption of Blood Flow—Tumours may interfere with blood vessels, leading to poor blood supply or increased intracranial pressure, which can cause headaches and dizziness.
- Hormonal imbalance: Tumours affecting the pituitary gland or other endocrine structures can lead to hormonal imbalances, which can result in symptoms like weight changes, fatigue, or menstrual irregularities.
- Fluid accumulation: Tumours may cause fluid buildup or lead to oedema (swelling), increasing intracranial pressure and contributing to symptoms such as headaches and nausea.
- Inflammatory Response: The presence of a tumour can trigger an inflammatory response in the surrounding tissues, contributing to pain, swelling, and other symptoms.
Skull Base Tumours: Treatment Options
Like any other brain tumour, skull base tumours are manageable and can be treated with a combination of therapies and surgical approaches. Some of the common treatment approaches for skull base tumours are listed below.
Skull base tumour surgery
This is a surgical procedure to precisely remove the skull base tumour by making an incision. However, the approach could be minimally invasive as well, and the complexity of the surgery depends on the type, size, and location of the tumour.
Some of the standard surgical procedures are listed below.
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Craniotomy
- This is a traditional surgical method in which an onco surgeon removes a portion of the skull to access the tumour. After reaching the tumour, they remove the tumour from the skull.
- It is often recommended for larger tumours or those located deeper within the skull and are not easily accessible.
The cost of craniotomy in India ranges from INR 2,50,000 to INR 6,00,000 (USD 4500 to USD 9500).
Endoscopic endonasal surgery
- This is a minimally invasive approach in which the tumour is located and accessed through the patient’s nose by an endoscope.
- This surgery is often recommended for smaller tumours located near the nasal cavity or sinuses.
Fractionated Stereotactic Radiotherapy (FSRT)
It is an advanced form of photon beam radiation therapy that targets tumours from multiple angles.
The photon beams used are invisible and don’t cause any pain to the patient as they pass through the skin to reach the tumour.
This causes minimal damage to the surrounding healthy tissue.
The treatment is typically divided into several sessions, based on the patient’s brain imaging, the extent of tumour growth, and other diagnoses.
Stereotactic Radiosurgery (SRS)
SRS is a precise method of delivering a high dose of radiation to a skull base tumour or a part of a tumour that couldn’t be completely removed surgically.
It’s generally completed in one session, ideal for patients with small skull base tumours (usually less than 3cm).
Oncologists perform this on patients who are not the suitable candidates for invasive surgery due to their age or other associated complications.
Despite its name, radiosurgery is not an actual surgical procedure as the radiation is delivered non-invasively.
Some of the advanced SRS being utilised in skull base tumour treatment are X-Knife, CyberKnife, Clinac, Gamma Knife, etc.
Conclusion
Living with skull base tumours can be a daunting experience, but it’s important to remember that there are many people who have successfully overcome this condition. With the proper treatment and support, it’s possible to manage the complexities of skull base tumours and continue to lead a healthy life.
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