Indications
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Most lesions in the posterior fossa
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Developmental anomalies such as Chiari malformations
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Brain tumors such as meningiomas, ependymomas, astrocytomas, and medulloblastomas
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Vascular lesions such as aneurysms, cavernous malformations, and arteriovenous malformations
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Figure 5-1:
Cavernous malformation.
Contraindications
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If lesions extend rostral to the tentorium, consideration should be given to a combined supracerebellar and supratentorial approach.
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If the lesion extends from the posterior fossa to the middle fossa, consideration should be given to a combined middle and posterior fossa approach.
Planning and positioning
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Preoperative antibiotics are given, and mannitol is given for brain relaxation.
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Depending on surgeon preference, lumbar subarachnoid drain placement for cerebrospinal fluid drainage can help with brain relaxation. This drain is particularly useful in situations in which the location of the lesion may prohibit early access to critical cisterns (i.e., cisterna magna).
Figure 5-2:
Patient position is prone for a straight midline posterior fossa approach. The prone position is optimal for lesions located caudally and at the craniocervical junction. For midline lesions, it is important to translate the head posteriorly and flex as much as possible to open the foramen magnum–C1 interval as much as possible, facilitating any bone work. Surgical navigation can be registered at this point per the preference of the surgeon and depending on the likely pathology. Tumors are more likely to require surgical navigation than vascular lesions in general.
