The midline suboccipital subtonsillar approach to the hypoglossal canal: surgical anatomy and clinical application

Abstract

Primary lesions of the hypoglossal canal, such as hypoglossal schwannomas, are rare. No consensus exists with regard to the surgical approach of choice for treatment of these lesions. Usually, lateral transcondylar approaches have been used. The authors describe the surgical anatomy of the midline subtonsillar approach to the hypoglossal canal. This approach includes a midline suboccipital craniotomy, dorsal opening of the foramen magnum and elevation of ipsilateral cerebellar tonsil to expose the hypoglossal nerve and its canal. The midline subtonsillar approach permits a straight primary intradural view to the hypoglossal canal. There is no necessity of condylar resections. The surgical anatomy of the subtonsillar approach is described and illustrated by an example of a case.

Morphometric Analysis Related to the Transcondylar Approach in Dry Skulls and Computed Tomography

“…Table II and Figures 1 to 7, with no significant differences in regard to sex. The laterality was significantly different between the right and left sides only in the measurement shown in between the HC and the OC is crucial in the TA (Bozbuga et al, 1998), and the OC maximum pierceable amount without opening the posterior edge of the HC is 1 / 3 or 1⁄2 posterior of the long axis of the OC (Rhoton;Marin Sanabria et al 2002;Tatagiba et al, 2006). The values of 10.3 mm on the right side, and of 11.3 mm on the left side for the mean distance between the HC and the posterior edge of the OC, found in this study (Table I, (Table I, A4) are also in accordance to the values reported by Muthukumar et al and Barut et al The structure of the septum of the HC must also be examined, because if two or three parts of the canal are not identified prior to surgery, the nerve of the HC can be injured (Katsuta et al, Table I.…”

Excision of hypoglossal neurinoma by condyle sparing suboccipital keyhole approach

“…The approaches have been lateral transcondylar, suboccipital or midline suboccipital subtonsillar. [147] Ichimura et al . preserved the FM and condyle in one out of seven patients; this patient had largely extradural tumor eroding the jugular foramen.…”

“…[3] Midline subtonsillar approach provides adequate approach in most of the cases allowing tumor removal with the brainstem, posterior inferior cerebellar artery and lower cranial nerves under direct vision. [4] The goal of tumor removal can be achieved by keeping it simple, and avoiding the morbidity associated with the extensive transcondylar approaches. postoperative day.…”

Meningioma arising in the hypoglossal canal: the midline suboccipital subtonsillar approach

“…The STA gives excellent access, providing a panoramic view of the foramen of Luschka laterally and up to the middle cerebellar peduncle [ 4 ]. However, the STA has not yet been described for resecting meningiomas of the hypoglossal canal although the suboccipital midline approach allows tumor removal through a direct angle of view.…”

“…The choice of treatment approach depends on several factors, including tumor type, size, compression of neural structures, patient age, symptoms and co-morbid conditions. Should surgery be considered, there is currently no consensus regarding the ideal surgical approach for treating these lesions [ 4 ]. Commonly used approaches for accessing the hypoglossal canal are the lateral transcondylar and far-lateral supracondylar approaches [ 3 , 4 ].…”