Foramen magnum meningioma surgery
Approaches
Since the initial pathological description of an foramen magnum meningioma in 1872, various surgical approaches have been described with the aim of achieving radical tumor resection 1).
They are challenging lesions because of the vicinity of the medulla oblongata, the lower cranial nerves, and the vertebral artery.
The surgical treatment of FMMs has evolved considerably due to the progress in microsurgical techniques and the development of a multitude of skull base approaches.
Standard midline suboccipital approach
Posterior and posterolateral FMMs can be safely resected via a standard midline suboccipital approach. However, controversy still exits regarding the optimal management of anterior or anterolateral lesions.
Based on anatomical and surgical constations it appears that a complete resection of the occipital condyle (resulting in occipito-cervical instability) should be reserved for those very extensive lesions. Yet a partial drilling of the condyle provides a better angle of approach, minimises the hazards of retraction of nervous structures and enables the surgeon to take the best advantage of the dissection and control of the vertebral artery 2).
The main advantage of the dorsolateral, suboccipital, transcondylar route is the direct view it offers to the anterior rim of the foramen magnum without requiring brain stem retraction 3).
Posterior FMMs
Posterior and posterolateral FMMs can be safely resected via a standard midline suboccipital approach.
Independently of technical variations and the degree of bone removal, all modern surgical approaches to the lower clivus and anterior foramen magnum derive from the posterolateral (or far-lateral) craniotomy originally described by Roberto Heros and Bernard George 4).
Innovation
The primary innovation consists in the use of the lateral approach, with the addition of partial resection of the lateral mass of C1. Baranowski etal., present the case of a patient with a meningioma located at the level of the dens of the epistropheus, on the anterior surface of the spinal cord. The lateral approach used in this case allowed for complete resection of the tumour with minimum operative risk, and the patient's recovery has been excellent 5).