Indications
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Ruptured or unruptured aneurysms of the vertebral artery, vertebrobasilar junction, and proximal posterior inferior cerebellar artery (PICA) have a particularly high rerupture rate and morbidity and mortality if left untreated. Unless the patient is tenuously unstable medically, treatment is indicated.
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In aneurysms deemed appropriate for surgical management, the far-lateral approach provides appropriate access to these lesions that are ventral or ventrolateral to the brainstem and below the mid-clival region.
Contraindications
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As with all aneurysms, open and endovascular approaches should be considered. If aneurysms in these locations have anatomy favorable for embolization, this approach should be attempted before open surgery if possible.
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If PICA aneurysms are distal and involve the telovelotonsillar or cortical segments of the PICA, they may be more midline, and a far-lateral approach may be inappropriate. A midline suboccipital or combined lateral and medial suboccipital approach may provide requisite access to the aneurysm.
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Patients who are medically unstable may not tolerate open surgery.
Planning and positioning
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The three-dimensional anatomy of the aneurysm and its relationship to its parent vessel must be clearly delineated. We routinely employ high-resolution computed tomography (CT) angiography with three-dimensional reformatting in preoperative planning. The bony anatomy detail on CT angiography studies is particularly useful in planning the far-lateral suboccipital exposure. In some cases, conventional catheter-based cerebral angiography is necessary to clarify the aneurysm better. Using either approach, it is critical to determine the relevant vascular anatomy, including (1) whether the PICA is duplicated, (2) whether PICA territory is supplied by neighboring vessels, (3) the size of the posterior communicating artery, and (4) the orientation of the aneurysm dome relative to its neck.
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Antibiotics and dexamethasone (Decadron) are routinely administered before skin incision.
Figure 26-1:
High-resolution CT angiography studies are becoming increasingly important for preoperative planning. Thin-section source images ( A ) are reformatted into three-dimensional images that can be easily manipulated on a radiology workstation ( B ).
Figure 26-2:
There are multiple surgical approaches to the vertebral artery, PICA, and vertebrobasilar junction. The appropriate approach is dictated primarily by the specific location of the aneurysm in this region. This schematic diagram summarizes our surgical approach strategies.
Figure 26-3:
The patient is placed in a straight lateral position with a pad placed under the axilla. The ipsilateral arm rests on pillows. The ipsilateral shoulder is pulled down using thick adhesive tape to allow greater freedom of movement with the microscope, and the head is tilted approximately 30 degrees toward the ipsilateral shoulder to facilitate venous and cerebrospinal fluid drainage. When the final position is obtained, the head is secured in a Mayfield head holder, and the patient’s body should be well secured with tape and blankets.Related posts:
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