THE CLOSE MEDIO-CONDYLAR OR TRANS-CONDYLA R LATERAL EXTENSION OF THE POSTERIOR SUBOCCIPITAL APPROACH - ANATOMICAL STUDY AND SURGICAL CONSIDERATIONS

In order to improve the surgical approach to tumors and aneurysms of t he anterior or antero-lateral aspect of the foramen magnum, some autho rs have proposed a lateral extension of the posterior sub-occipital ap proach to the occipital condyle including in some cases its partial or complete resection. The evaluation of this close medio-condylar or tr ans-condylar suboccipital approach has been performed on eight coloure d-latex injected specimens in the conditions of a microsurgical operat ion. 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 pre cise the accessible anatomical structures : Vertebral artery (and its control), Cranial nerves IX, X, XI & XII, Postero-inferior cerebellar artery and collaterals, Vertebro-basilar junction, antero-lateral aspe ct of the brain stem and spinal cord. Depending on the extent of the c ondylar resection, the lateral extension of the posterior sub-occipita l approach may be defined as minimal, moderate or large. Based on anat omical and surgical constatations 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 dr illing of the condyle provides a better angle of approach, minimises t he hazards of retraction of nervous structures and enables the surgeon to take the best advantage of the dissection and control of the verte bral artery.