A hockey stick incision is started in the midline at the level of the C2 spinous process, and extended superiorly to 2 cm above the inion (Fig. 5.2a, b). It is continued laterally above the superior nuchal line to a point directly superior to the mastoid process and then turned inferiorly to end at the mastoid tip. The occipital artery is preserved if required later in the procedure, as is pericranium for potential duraplasty. Dissection through the midline aponeurosis decreases muscle trauma and allows for early identification of the C1 lamina at a distance from the vertebral artery (Fig. 5.2c). The trapezius and sternocleidomastoid muscles overlie the semispinalis capitis and splenius capitis, which together conceal the suboccipital triangle. The superficial muscles are reflected as a single flap, maintaining a cuff along the superior nuchal line for a tight closure to decrease risk of cerebrospinal fluid leak (Fig. 5.2d). The muscle mass is elevated in the subperiosteal plane and swept laterally to expose the mastoid process and digastric groove (Fig. 5.2e). The attachments of longissimus capitis and posterior belly of digastric muscle are then released. As the technique aims to approach the ventral brainstem from a lateral trajectory, adequate inferolateral retraction is necessary to prevent encroachment upon the exposure by muscle bulk; hooked retractors on elastics serve this function better than hinged self-retaining retractors.

Incisions including the linear/curvilinear retromastoid incision and the S-shaped incision , beginning in the retromastoid region and extending medially to the midline, reduce the lateral bulk by directing the exposure through the musculature. However, these approaches increase muscle trauma and likelihood of sectioning the occipital artery and nerve, and place the vertebral artery at greater risk of injury as bony landmarks are not readily identified. Alternatively, the lateral muscle bulk can be decreased by individually identifying and dividing the sternocleidomastoid, splenius capitis, and semispinalis capitis and reflecting the muscles medially, although this approach increases the risk of wound dehiscence.

As the subperiosteal dissection continues inferiorly, the occipital attachments of the rectus capitis posterior minor, rectus capitis posterior major, and obliquus capitis superior are released. These latter two muscles, along with the obliquus capitis inferior, form the suboccipital triangle, which overlies the V3 segment of the vertebral artery and the C1 nerve root. The rectus capitis posterior major arises from the spinous process of C2 and forms the medial border of the suboccipital triangle. The obliquus capitis superior arises from the transverse process of C1 and forms the superior border, and the obliquus capitis inferior arises from the spinous process of C2 and inserts on the transverse process of C1, forming the inferior border. Elevation of the muscles laterally exposes the foramen magnum rim and lamina of C1, and the vertebral artery.

After the vertebral artery ascends through the C1 transverse foramen, it turns medially behind the atlanto-occipital joint and crosses the sulcus arteriosus of C1 in the depths of the suboccipital triangle. It then passes under the inferior border of the posterior atlanto-occipital membrane, and finally penetrates the dura (Fig. 5.2f). A rich venous plexus surrounds the artery and can cause brisk bleeding; coagulation and packing with hemostatic agents generally suffice to control it, although in some instances it may need to be resected. This segment of the artery is particularly vulnerable, as an aberrant loop toward the occipital bone may be injured during muscle dissection, or it may be compressed or avulsed against an ossified atlanto-occipital membrane arch. Electrocautery should be avoided when dissecting in the lower suboccipital area, as a sharp inadvertent arteriotomy is more readily repaired than a thermal injury. In addition, the muscular and posterior meningeal branches that arise in this segment may need to be divided in order to mobilize the artery. However, the posterior spinal artery or posterior inferior cerebellar artery (PICA) may have an extradural origin [1] and must be distinguished from muscular branches. Thorough preoperative imaging investigations provide forewarning about such variations and can guide decisions about repair or sacrifice of an injured vessel.

The suboccipital craniotomy extends superolaterally from the rostral extent of the pathology to inferomedially across the midline at the foramen magnum (Fig. 5.3a). The posterior arch of C1 is likewise removed from beyond the midline to the sulcus arteriosus near the lateral mass of C1, approximately 1 cm lateral to the dural ring surrounding the vertebral artery (Fig. 5.3b). Variations in anatomy such as an incomplete C1 arch or assimilation of C1 must be recognized and are ideally anticipated on preoperative imaging. Removal of bone around the foramen magnum continues to the occipital condyle (Fig. 5.3c). This extensive lateral exposure forms the crux of the far lateral approach, allowing for an inferolateral approach to the anterior brainstem while avoiding retraction; the lateral lip of the foramen magnum is thus analogous to the greater sphenoid wing in the pterional craniotomy. As the foramen edge becomes more vertical, further bone removal is facilitated by use of a high-speed drill while the surgical assistant retracts and protects the vertebral artery and its venous plexus (Fig. 5.3d). At the posterior aspect of the condyle, bleeding may be encountered from the posterior condylar emissary vein, which communicates the vertebral venous plexus with the sigmoid sinus. It traverses the condylar canal, the extracranial opening of which lies at the base of a depression, the condylar fossa (Fig. 5.3e). Exposure of the emissary vein denotes the lateral limit of the basic far lateral approach (Figs. 5.3f and 5.4).