Indications
The suboccipital craniotomy is used for most lesions in the posterior fossa. Its indications are:
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Brain tumors such as meningiomas, ependymomas, gliomas, medulloblastomas, acoustic neuromas and metastatic lesions.
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Vascular lesions such as aneurysms, cavernous malformations, arteriovenous malformations and intraparenchymal hemorrhages.
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Developmental anomalies such as Chiari malformations.
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Posterior fossa infections.
Contraindications
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Cervical spine pathology that would oppose flexion and reduction of the neck.
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The sitting positioning is contraindicated in patients with patent foramen ovale (this position requires a preoperative echocardiogram to rule out patent foramen ovale).
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If lesions extend above the tentorium, special consideration should be given to a combined approach, e.g. a supracerebellar and a supratentorial approach, to have good visualization of the lesion to be resected.
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If the lesion extends from the posterior fossa to the middle fossa, a combined or staged lateral approach may be considered.
Surgical Procedure
Patient Positioning
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Various sitting positions can be used depending on the location of the lesion, patient’s body habitus and other potential medical conditions (i.e. patent foramen ovale).
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Park bench position ( Figure 6.1 ) : This is a modification of the lateral position, and used more commonly for more laterally positioned lesions including lesions of the lateral cerebellar hemisphere and cerebellopontine angle, as well as the far lateral approach (see Chapter 22 ). The head is flexed and the vertex of the head is tilted towards the floor. Excessive neck flexion and/or side bending may impede venous return. The patient is well padded to avoid pressure injuries, especially to the ulnar nerve, brachial plexus and popliteal fossa.
Figure 6.1
Park bench position for suboccipital approach: patient positioning and padding. Caution is necessary to avoid brachial plexus injury. Several craniotomies can be performed to approach the cerebellar lesions. A small suboccipital approach is sufficient for localized lesions in the cerebellar hemisphere or vermis. A larger craniotomy will be required for larger pathology or pathology extending to the pineal region, venous sinuses or supratentorial space. The torcula and transverse sinus may be exposed and a supracerebellar–infratentorial or supracerebellar–transtentorial approach can be implemented. More lateral and ventral lesions would require a far lateral approach.
Reproduced with permission from Pascual, J.M., Prieto, R., 2012. Surgical management of severe closed head injury in adults. In Quiñones-Hinojosa, A. (Ed.), Schmidek & Sweet, Operative Neurosurgical Techniques: Indications, Methods and Results, sixth ed. Saunders, Elsevier Inc., Philadelphia.
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Prone Concorde position ( Figure 6.2 ) : The position is more commonly used for midline lesions located caudally and at the craniocervical junction. The patient is anesthetized in the supine position and then turned prone and placed on chest rolls. For the Concorde position the head is flexed and reduced, the thorax is elevated, Trendelenburg position is applied and the legs flexed at the knees.
Figure 6.2
Concorde position for midline posterior fossa approaches. Neck flexion must be achieved. Bed tilting is required.
© A. Quiñones-Hinojosa.
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Sitting position: This is less frequently used because of its potential complications (e.g. air embolism, increased risk of pneumocephalus), but its advantages include improved venous drainage and gravity retraction of the cerebellar hemispheres. It can be used for pineal region tumors and/or a supracerebellar infratentorial approach.
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Surgical navigation is registered after positioning. The surgical field should be perpendicular to the ground. The surgical field is sterilely prepped and local anesthetic is applied.
Skin Incision
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The incision is made depending on the location of the lesion and the position of the patient. Options include midline or paramedian incisions, and the potential shapes can be a straight line, C- or S-shaped incision, or hockey stick incision. The shape depends on the area that needs to be exposed.
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Straight midline: The patient is typically prone for a straight midline posterior fossa approach for centrally located or extensive lesions, or a lesion located caudally at the craniocervical junction. A linear skin incision is made in the midline extending from 4–5 cm above the inion down to the spinous process of the second cervical vertebra (C2). The length of the incision allows for wide lateral exposure of the posterior cervical fascia ( Figure 6.3 ). A similar linear midline skin incision is made if the patient is in the sitting position.
