Midline Suboccipital Approach

S. Alexander König, Veronika Messelberger, and Uwe Spetzger

25.1 Introduction

The suboccipital approach is a midline approach to the posterior cranial fossa, which gives direct access to the suboccipital surface of the cerebellar hemispheres.

By opening the inferior medullary velum, the fourth ventricle as well as the brainstem can be accessed. The surgical approach can be tailored to accommodate the relevant pathology. Options include, supratentorial extension as well as the re moval of the posterior arch of the atlas (C1).

25.2 Indications

• Parenchymal lesions of the lower cerebellum (e.g., hemorrhages, metastases, von Hippel-Lindau angiomas).

• Parenchymal lesions of the upper cerebellum and lesions in the pineal region (supracerebellar infratentorial approach).

• Lesions of the fourth ventricle (e.g., ependymomas).

• Dorsal brainstem lesions (e.g., cavernomas).

• Meningiomas of the medial posterior fossa.

• Posterior inferior cerebellar artery (PICA) aneurysms.

• Dorsal meningiomas of the foramen magnum.

• Chiari malformation.

25.3 Patient Positioning (Figs. 25.1, 25.2)

• Position: The patient is positioned prone. The head is flexed and fixed to a Mayfield clamp.

• Body: The body is placed in a slight ‘Concorde’ position with 10 to 20° of reverse Trendelenburg.

• Head: The head is maintained straight and flexed, leaving a space of about 2 cm between the chin and the chest.

• Shoulders: Shoulders are slightly pulled down for a safe position of the arms on the armrests.

• The spinous process of the third dorsal vertebra (T3) should be the highest point of patient´s body.

• The inion is the highest point in the surgical field.

25.4 Skin Incision

• Straight skin incision on the midline

◦ Starting point: Incision starts 3 cm above the inion on the midline.

◦ Course: Incision line runs exactly along the midline.

◦ Ending point: It ends at the spinous process of the axis (C2).

25.4.1 Critical Structures

• None

25.5 Soft Tissues Dissection (Figs. 25.3–25.5)

• Myofascial level

◦ The myofascial level is incised along the midline, according to the course of the skin incision (Fig. 25.3)

• Muscles

◦ Origins of both trapezius muscles are detached from the occipital bone and reflected laterally (Figs. 25.3, 25.4).

Fig. 25.1 Patient positioning. The head is inclined ventrally and fixed by a Mayfield clamp, while the patient is in prone position.

Fig. 25.2 Patient positioning. Skin incision.
Abbreviations: C2sp = spinous process of C2; EOP = external occipital protuberance.

Fig. 25.3 Muscles dissection and bone exposure. By reflecting the skin inferior to the superficial muscle layer will merge. The trapezius muscle is detached from the occipital bone and the nuchal ligament in the midline (red lines).
Abbreviations: EOC = external occipital crest; EOP = external occipital protuberance; IL = incision line; LA = linea alba; MF = muscle fascia; OA = occipital artery; OB = occipital bone; TR = trapezius muscle.

◦ Further incision of the nuchal ligament along the midline is carried out.

◦ Semispinalis capitis is detached and reflected laterally (Fig. 25.4).

◦ Rectus capitis posterior minor and rectus capitis posterior major are detached and reflected laterally (Fig. 25.5).

• Bone exposure

◦ Subperiosteal dissection of the occipital squama laterally from the midline to both sides is performed (Fig. 25.5).

◦ Subperiosteal dissection of the posterior arch of the C1 vertebra is carried out.

• Vertebral arteries

◦ The vertebral arteries are identified by dissecting the muscle layer laterally from the posterior atlanto-occipital membrane (blunt dissection) at the cranial edge of the C1 lamina.