The skull base is the anatomical region on which the brain rests. It is a complex anatomical area deep in the face, under the brain and in front of the brainstem. It is one of the most complex anatomical regions of the body.
The multiple bone structures that compose it are crossed by:
– The vessels that irrigate the brain (internal carotid artery, vertebral artery …),
– The spinal cord that passes into the spinal canal at the occipital foramen,
– The nerves that control:
- The Sense organs (sight, smell, hearing, taste)
- The oculomotor muscles allowing the eye to move
- The muscles of the face
- Sensitivity of the face,
The skull base is thus an entanglement of bone, sensory, nervous, vascular and muscular structures highly functional and vital.
Type of lesions
Skull base surgery treats lesions deeply located between the skull base and the brain or inside the skull base. The most common pathologies affecting the skull base are tumors. These tumors may be histologically “benign” (meningioma, acoustic neuroma, pituitary adenoma, craniopharyngioma) or malignant (cancerous) tumors (sinus, bone, cartilage, ear or salivary glands) :
- NEURINOMA or SCHWANNOMA
- CHOLESTEROL GRANULOMA
- FORAMEN JUGULAR TUMOR
- CAVERNOUS SINUS TUMOR
- PETROUS BONE TUMOR
- TUMOR OF THE ORBIT
Symptoms and diagnosis
Early diagnosis and multidisciplinary management is key to effectively treat these tumors.
Because of their location, skull base lesions can cause a variety of symptoms such as decreased vision, hearing loss, loss of smell, balance issues, swallowing difficulties, headaches, asymmetry of the face, sensitivity disorders and / or facial pains, obstruction of the nose, vertigo…
Imaging studies used to diagnose these lesions are mainly CT scanner and MRI. CT scanner accurately assesses bone structures but does not have good spatial resolution for the soft tissues. MRI allows accurate assessment of soft tissue, the lesion and its relationship to surrounding structures. Other examinations may be required depending on the suspected type of lesion and its location:
– CT angio, angio-MR, cerebral angiography in order to evaluate the vascularization of the lesion, its relationship with critical vessels that irrigate the brain such as the internal carotid artery and the vertebral artery and the anatomy of the brain draining veins
– Ophthalmological examination
– ENT checkup to assess hearing, balance or swallowing function
– Endocrinological workup to evaluate the impact of the lesion on the pituitary gland, which is a small gland, connected to the brain and located at the center of the skull base
Strategies and surgical techniques
This complex surgery involves breaking through the skull base (as though through a minefield) to access, expose, and remove the lesion while preserving the nerves and critical vessels that cross the skull base and avoiding brain retraction. The concept of skull base surgery is to select the ideal and most adapted pathway to the lesion. The surgical approach to the tumor can sometimes last several hours. In some cases, surgery is performed in 2 stages: A first step in order to access and expose the lesion and a second stage to remove it.
The removal of these lesions is challenging because of their proximity to critical neurovascular structures and the resection of these tumors, which are among the most complex tumors to operate in the body, is sometimes associated with a significant surgical risk.
Our department is specialized in skull base surgery and masters all the surgical approaches, techniques and technologies used to perform this type of operations.
Endoscopic endonasal pathways
The endoscopic endonasal approach (EEE) is an innovative surgical technique used to treat brain, skull base and craniocervical pathologies (mainly tumors) through the nose using an endoscope and suitable instruments.
A specially designed endoscope provides a light and a lens for viewing and transmitting internal images. Specific instruments are used along the endoscope to expose and remove the tumor.
The endoscopic endonasal approach allows the surgeon to treat many difficult-to-reach tumors without crossing the face or skull.
The neurosurgery department of Lariboisière was one of the pioneering departments in this field. We continue to develop in our laboratory new and less invasive endoscopic strategies for approaching complex and deep areas of the skull.
Transpetrosal approaches consist in creating a pathway through the bone on the side of the skull, in which are located the organ of hearing and balance as well as many critical nerves and vessels. Transpetrosal make it possible to reach deep and complexe lesions with a more suitable angle of attack, thus minimizing the retraction of the brain, which is very poorly tolerated and sometimes causes significant morbidity and sequelae. These approches use high-speed motors and diamond burs, which allow skeletalization and preservation of the nerves, sense organs and vessels passing through the bone.
Anterolateral approach and fronto-temporal orbito-zygomatic approach
These surgical corridors pass along the orbit to access lesions located deep in the brain or below the brain in the central part of the head. In order to have a more ascending line of sight and avoid brain retraction, the orbital rim behind the eyebrow, a part of the body of the maxillary (behind the chick) and the zygomatic arch can be removed to improve the exposure of the tumor and are replaced at the end of the surgery.
Minimally invasive keyhole-like approaches and endoscopic assisted microsurgery
In addition to endoscopic endonasal approaches that remove tumors through the nose, our team develops other mini-invasive transcranial techniques to minimize the size of the incision and bone opening. These techniques most often combine the use of an operating microscope and an endoscope to remove deeply located lesions with minimal morbidity.
For the supraorbital approach which is on of the most common keyhole approach that we use, the incision is placed in the eyebrow and a small bone opening the size of a coin is performed. The benefits for patients of these mini-invasive approaches are:
– Faster postoperative recovery
– Decreased postoperative pain
– Shorter hospital stay
– Less brain exposure and retraction
– A better cosmetic result
The use of an endoscope in combination with these small openings also allows seeing areas located “behind the corner” that the microscope couldn’t visualize.
Our technical platform:
Our surgeries are performed in dedicated operating theaters with highly qualified paramedical staff and state of the art surgical equipment
- Operating microscope with integration of neuronavigation and endoscopy
- High Definition Endoscope (HD)
- Ultrasonic scalpel
- Intraoperative monitoring of cranial nerves
- Intraoperative motor and sensory evoked potential
- Intraoperative scanner (being acquired)
Our common goal is to provide the best possible surgical result with the least side effects and maximum quality of life.
Multidisciplinary management – Skull base tumor board
Because of their difficult location and complexity, skull base lesion must be treated by specialized teams dedicated to skull base surgery. In addition to surgery, chemotherapy and / or radiotherapy may be necessary, depending on the type of tumor and residual tumor after surgery. Parts of the tumor sometimes cannot be removed because of a high risk of postoperative sequelae and morbidity.
The participation of multiple specialists (neurosurgeons, ENT surgeons, radiotherapists, oncologists, radiologists…) in the decision-making makes it possible to define for a given patient, the most adapted therapeutic strategy: Surgery, radiation therapy, radiosurgery, and chemotherapy. The ultimate goal is to control the lesion with restoration or preservation of the quality of life.
Skull base tumors are treated with the support of a multidisciplinary team:
- Neurosurgery department
- ENT department
- Ophthalmology department
- Orsay Proton Therapy center
- Radiation oncology department of the Pitié-Salpetrière hospital
- The Hartmann radiotherapy center
- The Curie Institute
- The Gustave Roussy Institute
The Neurosurgery Department collaborates closely with the Orsay Proton Therapy Center. Proton beam therapy is a specific radiotherapy technology particularly suited to high-dose radiation of deep lesion located in the immediate vicinity of critical structures. This treatment is particularly suitable for patients with chondrosarcoma or chordoma in addition to a surgical resection as complete as possible.
Training and research
The department continually develops surgical, minimally invasive, more conservative and more appropriate surgical approaches, as well as the technological tools to address and treat them more effectively. For this purpose the service has an experimental Neurosurgery laboratory where new techniques and technology are tested and evaluated.
Our team also organizes and participates in many skull base training courses around the world.