gms | German Medical Science

Objective: Lesions lateral to the lower brainstem in an area reaching from the Foraminae Luschkae to the Foramen magnum are rare and containing different pathologies. This surgical area is challenging and there exists no consensus with regard to the surgical approach of choice for the treatment of these lesions. Commonly used approaches include median suboccipital transvermal approach, lateral suboccipital approach as well as far lateral transcondylar approaches. We describe the anatomy of the midline suboccipital 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.

Method: The microsurgical features of the STA were examined in three ETOH fixed specimens in semi-sitting position using neurosurgical standard equipment. Distances were measured using a caliper rule. Additionally thirty one patients who underwent surgery using the STA from 2005 to 2011 were examined and evaluated with respect to the type of pathology, duration of surgery and postoperative period.

Results: The anatomical studies showed a distance between external occipital protuberance and Foramen magnum of 5 cm (SD ± 0,7 cm), between the occipital condyles of 3,4 cm (SD ± 0,26 cm). After retracting the tonsils 0,3 cm (SD ± 0,08 cm) we gain vision of PICA. Retraction to 0,35 cm (SD ± 0,17 cm) exposed spinal root of CN XI. Hypoglossal canal got visible after 0,9 cm (SD ± 0,09 cm), the root exit zone of glossopharyngeal nerve after 1,29cm (SD ± 0,15 cm), the jugular foramen after 1,59 cm (SD ± 0,3 cm), the inner auditory canal after 2,42 cm (SD ± 0,2 cm) of tonsil retraction. In the 31 cases using the STA the types of pathologies contained of Plexus papillomas, Schwannomas, Cystes, Aneurysms, Haemangioblastomas and vascular conflicts. The STA from skin incision to dural opening needed 40 min (± 10min). The middle surgery duration was 295 min (SD ± 115min). The time on ICU ranged from overnight stay to 37 days, with mean resting time of 6,14 days (SD ± 10,66 days). The mean period of hospitalization was 14,67 days (SD ± 9,65 days), with 14 cases shorter than 10 days and only three cases staying over 22 days.

Conclusions: The STA provides a straight and wide angle view to various types of pathologies in the cerebellomedullary and lateral premedullary cisterns with moderate degree of tonsil retraction. The pathology itself can help to reduce tonsillar pressure by displacing the tonsils and therefore giving space for surgery. Compared to other approaches we see benefit in the straightforward concept of the STA for these entities as time- and morbidity sparing approach.