[Juxta- or trans-condylar lateral extension of the posterior suboccipital approach. Anatomical study, surgical aspects].

In order to improve the surgical approach to tumors and aneurysms of the anterior or antero-lateral aspect of the foramen magnum, some authors have proposed a lateral extension of the posterior sub-occipital approach to the occipital condyle including in some cases its partial or complete resection. The evaluation of this close medio-condylar or trans-condylar suboccipital approach has been performed on eight coloured-latex injected specimens in the conditions of a microsurgical operation. The extra- and intradural steps have been studied so as to define the optimal position of the patient's head and the surgeon and to precise the accessible anatomical structures: Vertebral artery (and its control), Cranial nerves IX, X, XI & XII, Posterior-inferior cerebellar artery and collaterals, Vertebro-basilar junction, antero-lateral aspect of the brain stem and spinal cord. Depending on the extent of the condylar resection, the lateral extension of the posterior sub-occipital approach may be defined as minimal, moderate or large. Based on anatomical and surgical constations it appears that a complete resection of the occipital condyle (resulting in occipito-cervical instability) should be reserved for those very extensive lesions. Yet a partial drilling of the condyle provides a better angle of approach, minimises the hazards of retraction of nervous structures and enables the surgeon to take the best advantage of the dissection and control of the vertebral artery.