Far Lateral (Transcondylar)

Heros described the lateral suboccipital approach for vertebral and vertebrobasilar artery lesions in 1986^[1], and Bertalanffy and Seeger described the dorsolateral transcondylar approach to the lower clivus and anterior craniocervical junction in 1991^[2]. Wen, Rhoton and colleagues defined the anatomy of the transcondylar, supracondylar and paracondylar extensions, which are added to the basic far-lateral approach according to the target^[3].

• Ventral and ventrolateral foramen magnum meningiomas.
• Aneurysms of the vertebral artery, the vertebrobasilar junction and proximal PICA.
• Lower clival and craniocervical chordomas and chondrosarcomas.
• Jugular-foramen tumours with intradural extension and hypoglossal schwannomas.
• Cavernous malformations of the lower brainstem (medulla).

The suboccipital triangle, bounded by the rectus capitis posterior major and the superior and inferior obliques, contains the horizontal (V3) segment of the vertebral artery on the posterior arch of C1, surrounded by a venous plexus. The occipital condyle lies anterolateral to the foramen magnum; the hypoglossal canal runs above the junction of its posterior and middle thirds. The condylar emissary vein and the posterior condylar canal are useful landmarks. Intradurally, the approach exposes the vertebral artery, PICA and the lower cranial nerves (IX–XII), and the spinal accessory nerve rises along the cord^[3].

• Park-bench position, head flexed, rotated away and tilted down toward the floor to open the craniocervical angle.
• Hockey-stick or C-shaped incision; dissect the muscles in layers to the suboccipital triangle.
• Identify and control the vertebral artery at C1; the venous plexus around it bleeds briskly.
• Lateral suboccipital craniotomy extending to the foramen magnum and the sigmoid sinus, with hemilaminectomy of C1.
• Drill the posterior third of the condyle (transcondylar) as far as needed to see the ventral foramen magnum; extra bone removal above the condyle (supracondylar) opens the hypoglossal canal and the lower clivus, and lateral removal (paracondylar) reaches the jugular foramen.
• Open the dura in a curve along the lateral margin; work through the spaces between the lower cranial nerves.

• Lower cranial-nerve palsy with dysphagia and aspiration: the most important morbidity; monitor the lower cranial nerves and assess swallowing before feeding.
• Vertebral artery injury: identify the artery early and know its variations (extradural PICA origin, persistent first intersegmental artery).
• Craniocervical instability after removal of more than about half of the condyle; consider occipitocervical fusion.
• CSF leak and pseudomeningocele: watertight dural closure.