A COMBINED INTRADURAL PRESIGMOID-TRANSTRANSVERSARIUM-TRANSCONDYLAR APPROACH TO THE WHOLE CLIVUS AND ANTERIOR CRANIOSPINAL REGION - ANATOMICSTUDY

Surgical exposure of the clivus is difficult because of its proximity to vital neuro-vascular structures. The anatomic bases of a new surgic al approach to this area are discussed. A supra-auricular skin incisio n is extended toward the posterior border of the sternocleidomastoid m uscle. The vertebral artery is exposed from C2 to the occiput unroofin g the foramen transversarium of C1. The bone removal consists of a pos terior temporal craniotomy, a suboccipital craniectomy, including mast oidectomy with sigmoid sinus unroofing, removal of the lateral margin of the foramen magnum, of the medial third of the occipital condyle, a nd retrolabyrinthine petrous drilling. Posterior retraction of the ver tebral artery facilitates occipital condyle drilling. Intradural expos ure of the petroclival region is achieved by L-shaped cutting of the d ura with the long branch placed infratentorially anterior to the sigmo id sinus. Intradural exposure of the craniospinal/upper cervical areas is achieved by cutting of the dura medial to the distal sigmoid sinus and by longitudinal cutting of the dura anterior to the vertebral art ery. This approach allows multiple ports of entry to the clivus with f ull control of the vertebrobasilar system, and of the dural sinuses, a nd is anatomically suited for controlled removal of tumors located in these areas. This approach, or segments of it, has been used successfu lly in the treatment of large neoplasms of the craniovertebral junctio n.