Midline Suboccipital Subtonsillar Approach to the Cerebellomedullary Cistern and the Craniocervical Junction and Its Structures: Anatomical Considerations and Clinical Application

Objective: Lesions lateral to the lower brainstem are rare and harbor different pathologies. No consensus exists with regard to the surgical approach of choice for the treatment of these lesions. We describe the anatomy of the suboccipital-midline-subtonsillar-approach (STA). The STA provides a straight and wide angle view to various types of pathologies in the cerebellomedullary cistern and the craniocervical junction. Methods: The microsurgical features of the STA were examined in three ETOH fixed specimens in semisitting position. In addition 31 patients who underwent surgery using the STA from 2006 to 2012 were examined and evaluated with respect to the type of pathology, morbidity of surgery, and postoperative period. Results: The anatomical studies showed a distance between occipital protuberance and foramen magnum of 5 cm, between the occipital condyles of 3.4 cm. After retracting the tonsils 0.3 cm we gain vision of PICA. Retraction to 0.35 cm exposed spinal root of CN XI. Hypoglossal canal got visible after 0.9 cm, the root exit zone of glossopharyngeal nerve after 1.3 cm, the jugular foramen after 1.5 cm, the IAC after 2.4 cm of tonsil retraction. In 31 cases using the STA pathologies contained plexus-papillomas, hypoglossal-schwannomas, aneurysms, hemangioblastomas, and vascular conflicts. The STA approach from skin incision to dural opening was 40 minutes. The mean duration of surgery was 295 minutes. Conclusions: The STA provides a straight and wide angle view to various types of pathologies in the cerebellomedullary and lateral-premedullary cistern with moderate degree of tonsil retraction. The pathology itself helps to avoid spatula pressure by displacing the tonsils and giving space for surgery.