Intraaxial lesions of the foramen magnum

According to their strategic location, intraaxial lesions of the foramen magnum may cause severe symptoms. The primary goal of surgery is to decompress the lower brain stem and upper cervical cord without additionally impairing the neurological function, or, as in vascular lesions, to eliminate the risk of recurrent bleeding. Secondary goals of surgery are to preserve the atlanto-occipital stability, to minimize traumatization of various muscles in the craniovertebral region, to preserve the sigmoid sinus and jugular bulb and to avoid air embolism or excessive venous bleeding during surgery. The most common intraaxial lesions encountered at the level of the foramen magnum are cavernous malformations, gliomas, ependymomas, and hemangioblastomas. They are located either in the medulla oblongata (up to the pontomedullary junction) or within the cervical cord at the level of C1. These lesions may be located either totally intraaxially, with or without contact to the surface of the brain stem or spinal cord, or, in other instances, they may be partially exophytic (1). Moreover, from the surgical point of view, particularly in terms of accessibility, lesions located in the dorsal and lateral region of the brain stem and spinal cord significantly differ from those located anteriorly or anterolaterally. Hemangioblastomas may sometimes involve the proximal intradural vertebral artery and its branches.