What are Skull Base Problems?
The skull is made up of facial bones and the cranium, which encases the brain. The base of the skull on which the brain sits is called the skull base. It is made up of bones that form the roof of the nasal cavities, orbital (eye) cavities, inner ears, and some sinuses. The skull base is a complex area having multiple openings which accommodate the spinal cord, nerves, and blood vessels. Skull base problems or disorders are conditions that arise out of issues with one or more of these structures. These structures supply the brain with oxygen and nutrients and are critical to functions such as hearing, smell, vision, breathing, and facial movement. Skull base conditions are often close to critical areas of the brain, such as the brainstem and major blood vessels and nerves, making it a very difficult and complex region to treat.
Types of Skull Base Problems
The skull base is an extremely complex region of the body that can be commonly affected by benign (non-cancerous) or malignant (cancerous) tumors, trauma, and infections. Some of the skull base problems include:
- Acoustic neuroma: Acoustic neuroma, also called vestibular schwannoma, is a noncancerous tumor usually seen in middle-aged people. It develops gradually on the main nerve leading from the inner ear to the brain. This nerve controls hearing and balance. So, as the acoustic neuroma grows, it leads to hearing loss and problems with balance.
- Glomus tumors: Glomus tumors, also known as paraganglioma, are benign vascular tumors of the ear that can often involve the major venous and arterial vascular structures that travel from the neck into the temporal bone of the ear. While these tumors are benign, they can be quite aggressive and spread beyond the margins of the ear, in some instances extending down towards the neck, and erode through the bone separating the ear from the brain.
- Sinonasal tumors: Sinonasal tumors are abnormal growths that occur in the area of the sinuses and nasal cavities. These tumors may be benign or malignant. Examples of benign tumors include juvenile nasopharyngeal angiofibroma (JNA), inverted papilloma, and osteoma. Examples of malignant tumors include sinonasal undifferentiated carcinoma (SNUC), esthesioneuroblastoma, adenocarcinoma, and adenoid cystic carcinoma.
- Pterygopalatine and infratemporal fossa tumors: The pterygopalatine fossa and infratemporal fossa are complex spaces behind the sinuses and just under the skull base. They are many times difficult to access because of all of the surrounding structures that enclose them. Tumors can grow within these spaces. These tumors may be benign or malignant. Benign tumors, such as schwannomas and juvenile nasopharyngeal angiofibroma (JNA), will not spread to other regions of the body but may crowd other structures in the skull base and create other problems. Cancerous tumors like adenoid cystic carcinoma and squamous cell carcinoma present a risk of spreading to other parts of the body.
- Orbital and optic nerve tumors/optic nerve compression: Orbital and optic nerve tumors are growths that develop in the skull’s eye socket (orbit) or on the nerve that transmits information from the eye to the brain (optic nerve). These growths are caused by the body’s cells growing out of control. Orbital and optic nerve tumors can be benign or malignant. Both benign and malignant orbital and optic nerve tumors can create pressure on the nerves that allow the eye to function, causing vision problems. This is called optic nerve compression.
- Nasopharyngeal tumors: The nasopharynx is a term for the upper portion of the throat, behind the nose. Sometimes, cells in the nasopharynx can begin to grow out of control. This causes a nasopharyngeal tumor to develop. A nasopharyngeal tumor can be benign or malignant. Benign tumors are rare but are found most commonly in children and young adults. Although these benign tumors will not spread to other parts of the body, they can grow in size and cause health complications. Hence, they typically need to be removed surgically. Malignant tumors can indicate one of several types of cancer, including nasopharyngeal carcinoma (NPC), lymphoma, adenocarcinoma, and adenoid cystic carcinoma. Treatments may vary depending on the type of cancer that is found.
- Cancers of the ear canal and temporal bone: Cancers of the external auditory canal and temporal bone are extremely rare. The most common types of these cancers are squamous cell carcinoma and basal cell carcinoma. They require aggressive treatment, including surgery and sometimes radiation therapy. Unlike cancers that grow on the ear lobe or other parts of the skin, cancers of the ear canal and temporal bone are often quite aggressive. These tumors can spread into the temporomandibular joint and involve the muscles responsible for the movement of the jaw and chewing. Tumors may involve the salivary gland in front of the ear (parotid gland).
- Petrous apex lesions: The petrous apex is a triangular region of hard bone that is located deep in the inner ear. Petrous apex lesions most commonly include cholesterol granulomas and cholesteatomas, known as epidermoid tumors. There are other lesions that are less common.
- Pituitary tumors: A pituitary tumor is a tumor that arises from the pituitary gland, the gland primarily responsible for regulating your hormones. The bean-sized pituitary gland is found just behind your eyes at the base of the brain. Pituitary tumors can have a big impact on your quality of life because of the pituitary gland’s crucial role in regulating your body’s hormones.
Signs and Symptoms of Skull Base Problems
Common signs and symptoms of skull base problems include:
- Weakness
- Numbness
- Tingling
- Pain
- Trouble breathing and swallowing
- Discharge from the ear (otorrhea).
- Hearing loss
- Loss of balance/dizziness
- Headaches
- Nose bleeds
- Nasal blockage
- Loss of sense of smell
- Tinnitus (ringing in ears)
- Changes in voice
- Changes in vision
Diagnosis of Skull Base Problems
Your doctor will review your medical history and symptoms and based on this a physical examination will be performed. Diagnostic tests to confirm skull base problems can include blood work, tissue biopsy, nasal endoscopy, hearing test, magnetic resonance imaging (MRI) scan, computed tomography (CT) Scan, and ultrasound.
Treatment for Skull Base Problems
Treatments for skull base problems are customized for each patient. Tumor characteristics including size and location of the tumor, involvement of critical structures, as well as the patient’s personal health and preferences are factored in prior to deciding the treatment approach. Treatment options may include:
- Watchful Waiting/Observation
- Chemotherapy
- Radiotherapy
- Microsurgical Resection
- Stereotactic Radiosurgery
- Advanced Microscopic, Laser and Ultrasonic Techniques
- Restorative and Reconstructive Facial and Skull Base Surgery
- Minimally Invasive Endoscopic Surgical Techniques
- Open Skull Surgery
From a surgical perspective, the two most common ways to approach the skull base are:
- Endoscopic approach: This is a minimally invasive approach that involves accessing the tumor through the natural openings of your nose or mouth by passing an endoscope (a lighted tube). Surgical instruments are guided through the endoscope with imaging devices. This approach is preferable as it carries little risk and is associated with faster healing following surgery.
- Open approach: This is a traditional surgical approach that involves making incisions in the cranium and facial bones, and occasionally removing bone to allow access to the skull base. This approach is necessary for complicated conditions.
Skull base surgery requires a multidisciplinary approach involving ENT surgeons (ear, nose, and throat), neurosurgery, and radiology.
