Dott. Giannantonio Spena
Director of Neurosurgery Unit
Fondazione IRCCS Policlinico San Matteo
Pavia, Italy
Fondazione IRCCS Policlinico San Matteo
Pad. Nuovo Ospedale "DEA"
Piano +7 - Corpo A
Secretary + 39 382 502780
For Private Outpatient Appointment
Policlinico San Matteo: you can book an appointment by calling +39 382 501788 or by filling out the online form.
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The posterior cranial fossa and the posterior skull base represent the portion of the skull located immediately below the nape of the neck. This area of the skull is covered and protected by several layers of muscle, making surgical approaches quite complex.
The posterior cranial fossa is smaller than the upper portion of the skull and vaguely funnel-shaped. Despite this, it houses some of the most delicate and vital structures of the central nervous system (cerebellum, brainstem, cranial nerves V, VI, VII, VIII, IX, X, XI, and XII, vertebral arteries, and the basilar artery).
Surgical approaches to the posterior fossa and posterior skull base require in-depth anatomical knowledge and extensive surgical practice. There is no single best surgical approach for all cases, but rather, the best approach for each individual patient must be chosen.
For this reason, our hospital maintains a close collaboration between the neurosurgeon and the ENT specialist, aimed at exploiting the potential of all neurosurgical and ENT approaches in the safest and most effective way.
Furthermore, all surgical procedures for the removal of tumors of the posterior cranial fossa and posterior skull base are performed with the aid of extensive neurophysiological monitoring. These techniques ensure continuous monitoring of the integrity of the cranial nerves being manipulated, as well as the brainstem connections.
Immediately after the acoustic-vestibular neuromas in terms of frequency are meningiomas, dermoid/epidermoid cysts and, even less frequently, neuromas of the other cranial nerves (for example neuromas of the fifth nerve, the trigeminal nerve).
All these tumors are mostly benign and very slow growing, although they can "slowly" reach considerable dimensions and seriously threaten the patient's autonomy.
Indications for surgical treatment are influenced by many factors including size, location, age, brainstem compression, and clinical symptoms.
While the tumor's location for vestibular acoustic neuromas is always around the internal auditory canal, for meningiomas or dermoid/epidermoid cysts, the location can vary greatly depending on where the tumor began to form. This will determine the type and extent of the proposed surgical approach.
Skull Base Tumors
In-depth analysis
Intraoperative electrophysiological monitoring
This technique requires the presence in the operating room of a neurophysiologist, i.e. a doctor expert in electrophysiological monitoring of nerves and the brain.
Monitoring allows for highly precise and safe real-time information on the functional status of a nerve. The principle is based on the application of a series of receiving electrodes (microscopic needles inserted into the muscles corresponding to the nerve being monitored, such as the facial muscles) and the application of very low-voltage currents to the nerve being examined. This provides information not only on the extent to which the nerve is being manipulated and irritated, but also on its functional integrity.
Surgery for tumors of the posterior cranial fossa and posterior skull base requires these monitoring procedures.
Our hospital offers a dedicated and highly experienced team in intraoperative electrophysiological monitoring.
Examples of surgical treatment
Petro-clival Meningioma of the left side
A 62-year-old patient with a large meningioma of the apex of the left cranial bone (left images). Surgery was performed using a retrosigmoid approach in the sitting position with electrophysiological monitoring of the 5th to 11th cranial nerves and sensory evoked potentials (SEPs). The postoperative MRI showing total tumor resection is shown on the right. After approximately 2 months of rehabilitation, the patient resumed a normal life.
Schwannoma of the fifth cranial nerve on the right
A 37-year-old patient with a large tumor involving the posterior fossa and the gasserian ganglion region. Surgery was performed via a retrosigmoid and suprameatal approach in the sitting position with electrophysiological monitoring of the 5th to 11th cranial nerves and sensory evoked potentials (SEPs). Below, the postoperative MRI shows almost complete tumor resection. A small residual tumor remains in the cavernous sinus, which is stable after 3 years. The patient leads a normal life and has a right trigeminal nerve deficit.
Meningioma of the right foramen magnum region
The tumor was removed using a far lateral approach, which allows access to the deepest and most anterior portion of the posterior skull base.
As can be seen in the image below, the tumor had eroded a large portion of the articulation between the skull and the cervical spine on the right. Additionally, additional bone had to be removed to reach the tumor. Therefore, occipitocervical stabilization was applied (photo below right).
Large meningioma of the apex of the left petrous bone
For several months this patient had been complaining of double vision and dizziness as well as the sensation of having the lower half of his face on the left side asleep.
The photo below shows a brain MRI showing a large meningioma at the apex of the left petrous bone. The patient then underwent surgical removal (bottom photo) of the meningioma via a retrosigmoid approach in the sitting position. Two months after surgery, the patient has fully resumed his normal life and presents only with mild and intermittent double vision and a slight decrease in sensation in the left jaw.
Below, on the left, is a preoperative brain MRI of a patient with a tumor infiltrating the lateral orbital wall, causing anterior dislocation of the eyeball. On the right, a postoperative MRI shows complete removal of the mass with reconstruction of the lateral orbital wall.
Here is a preoperative brain MRI of a patient with a malignant tumor infiltrating and destroying the left occipital condyle and the C1 joint (red arrows). The tumor had very close ties to the jugular vein (orange arrow) and the vertebral artery (purple arrow). The lower panel shows the postoperative CT scan, which demonstrates complete removal of the mass (green arrows) and placement of a craniocervical fixation system (turquoise arrow).
A 56-year-old patient with a long history of neck pain presented with progressive difficulty moving the right limbs.
The preoperative brain MRI (first image) shows a large mass occupying the foramen magnum region, causing severe compression of the junction between the brainstem and the spinal cord.
In addition, the vertebral arteries are displaced, and the right vertebral artery is completely encased by the tumor (red arrows).
The most likely diagnosis is a foramen magnum meningioma.
The patient underwent surgery using a far-lateral approach with extensive electrophysiological monitoring.
The lower image shows complete removal of the mass.
After a hospital stay of about 20 days, the patient was discharged home. She underwent physical therapy and is currently fully independent in all activities.
She reports some mild difficulty in tongue movements.
Below is a case of a left jugular foramen meningioma.
The patient underwent surgery using a retrosigmoid approach (A modified park bench position: the “Dormeuse” position. Spena G, Guerrini F, Grimod G. Acta Neurochir (Wien). 2019 Sep;161(9):1823–1827. doi: 10.1007/s00701-019-04013-0. Epub 2019 Jul 19).
