♦ Preoperative
Testing
Noninvasive
- Full medical work-up including evaluation of cardiac and other causes of poor collateral perfusion (e.g., medications, poor diet, etc.)
Invasive
- Balloon test occlusion (BTO) of vessel likely to be sacrificed by surgical resection and assessment of patient tolerance and collateral flow
Operative Planning
Imaging
- Review computed tomography (CT) scan, perfusion study (CT perfusion, CT xenon, magnetic resonance imaging perfusion, positron emission tomography regional oxygen extraction fraction), angiography, and/or BTO results
Graft Selection
- Superficial temporal artery (STA) grafts (versus radial artery or reversed saphenous vein) provide:
- Low to moderate flow for reperfusion
- Limited intraoperative versatility and reach to recipient vessels
- Similar diameter to distal middle cerebral artery (MCA) branch vessels (i.e., low anastomotic disproportion risk)
- Low risk of postoperative spasm
- Low to moderate flow for reperfusion
- Review angiography to ensure either the posterior (preferably) or anterior STA are patent and of suitable size
- Determine other suitable grafts should the STA fail
Special Equipment
- Doppler probe (preferably with back-up Doppler probe at the ready)
- Radiolucent Mayfield head holder
- Aneurysm clip tray
- Electroencephalogram (EEG) monitoring
- Fluoroscopy for intraoperative angiography
- Operating microscope
Operating Room Set-up
- Standard craniotomy
Anesthetic Issues
- Avoid agents that may lead to hypotension during case.
- Avoidance of hyperventilation that may lead to vasoconstriction; prefer pCO2 > 32 mm Hg
- Once need for bypass established, have anesthesiologist give an antiplatelet medication; if need for bypass known, start antiplatelet the night before surgery
♦ Intraoperative
Positioning
- Confirm (and reconfirm) side of surgery as the bypass may not always be on side of the lesion or symptoms
- Place patient supine in the radiolucent Mayfield head holder; degree of head rotation 10 to 80 degrees depending on location of pathology
Technique
- Use a Doppler probe and marking pen to trace both the posterior and anterior STA branches from the zygoma. Draw the line of incision several millimeters behind the posterior branch; should the posterior branch not be suitable, the anterior branch can be accessed within the flap.
- Strip shave over the appropriate STA branch using an electric razor.
- Place EEG leads away from surgical site.
- Standard sterile preparation of scalp and re-mark the line of incision. A linear incision will suffice if the posterior branch is viable; however, have the scalp prepared to turn a reverse-question mark flap allowing access to the anterior STA from within.
- Consider sterile preparation of ipsilateral neck (for carotid exposure), ipsilat-eral forearm (for radial graft if needed), and ipsilateral/contralateral thigh (for saphenous vein graft if needed).
- Incise the epidermis and dermis with extreme care to avoid damage to STA (especially proximally). Identify the STA under the loose connective tissue and create two longitudinal channels, distal to proximal, down to temporalis fascia on either side of the vessel using blunt dissection. Small branches can be ligated, 2 to 3 mm away from the main branch, with bipolar electrocautery and microscissors. Mark the outer portion of the vessel with a marking pen to help identify kinking or twisting later on. Once an adequate length of vessel has been exposed (typically 8 cm), protect the cuff with a papaverine-soaked Cottonoid.
- Tailor a bone flap suitable to view a portion of the sylvian fissure and/or deal with other intracranial pathology.
- Incise the dura in a cruciate manner and identify cortical branches of the MCA and the arachnoid planes of the sylvian fissure.
- Split the fissure, if needed, from lateral to medial looking for suitable recipient M3 or M2 vessel. Typically vessels > 1.5 mm are required.
- Free the recipient vessel from arachnoidal attachments 4 to 5 mm proximal and distal to the anastomosis site taking care not to disturb branching vessels. Place a contrast media underneath the recipient vessel to help with visualization.
- Protect the cortex with a moist gauze while turning you attention to the STA. Clear any loose connective tissue from the distal STA end ~2 to 3 cm proximal. Place a temporary clip midway on the STA, cut the distal-most portion of the STA, and control any back bleeding. Re-cut the distal end at ~45 degrees and reconfirm adequate flow by releasing the proximal clip. Irrigate the cut end of the STA with heparinized saline flush and gently move the graft into position. Ensure that graft is not on stretch or twisted in this position. If possible, allow for STA to assume its native configuration.
- Temporary clips should be place both proximal and distal to the anastomosis site on the recipient vessel. A linear incision is then made with a Beaver blade or no. 11 blade on the dorsum of the recipient vessel to a length approximating the diameter of the graft mouth.
- Use a single-armed 9–0 Prolene suture to anchor the donor at the apices and continue in an interrupted fashion. Our experience suggests this allows for better graft maturation and less anastomotic stricture. Sutures should be placed from outside the donor to inside the recipient. During suturing frequently flush the anastomosis with heparinized saline.
- Unclamp vessels in order: distal MCA, proximal MCA, then proximal STA. Ensure adequate flow through graft and recipient vessel with micro-Doppler. An intraoperative angiogram can be performed at this time as well.
- The dura can be loosely closed and Gelfoam (Pfizer, New York, NY) placed on top. Use a drill to create a notch in the bone flap to provide sufficient protection against STA kinking or occlusion. Close galea and skin with care not to damage STA. Consider applying occlusive dressing to incision site only. If head wrap applied, ensure it is loose fitting.
- Tailor a bone flap suitable to view a portion of the sylvian fissure and/or deal with other intracranial pathology.
♦ Postoperative
Immediate Recovery
- Assess for gross motor movements prior to extubation; if hemiparesis noted, consider reopening
- Perform and document a full neurologic exam on awakening to test for new deficits; clearly document old deficits as well
- Maintain normovolemia and ensure episodes of hypotension are avoided; be vigilant for subtle neurologic changes
- Transcutaneous Doppler examinations should be performed regularly to assess graft patency
- An angiogram is typically performed within the first 24 to 36 hours
Regular Floor Stay
- Ambulation should be encouraged early; however, a step-wise approach should be taken to avoid orthostatic hypotension
Discharge
- Compliance with antiplatelet medications, adequate hydration and nutrition, and avoidance of major antihypertensives are paramount in the immediate period after discharge
- Angiography is typically performed at 3 months, 6 months, and then as needed
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