Pterional craniotomy for Posterior Communicating Artery Aneurysm

 

  • Introduction- The posterior communicating artery aneurysm is an aneurysm that neurosurgeons are very familiar with but as Dr. Lawton warns “it’s not just a PComm”. This aneurysm needs to be taken seriously and approached thoughtfully
  • Anatomy- The posterior communicating artery (PComm) originates from the posterior wall of the internal carotid artery (ICA) and divides the carotid into ophthalmic and communicating segments. The PComm travels posteriorly to communicate with the posterior cerebral artery (PCA). The oculomotor nerve (CN III) is closely associated with the PComm and patients will often present with a 3rd nerve palsy.  The most closely related artery is the distally located anterior choroidal artery.
  • Preop- Set-up the microscope so the observer scope is as high as possible otherwise the observer (probably you) will be very uncomfortable. A Layla bar is helpful so make sure that the attachment is on the contralateral side of the bed
  • Positioning
    • The patient’s ipsilateral shoulder is bumped with a saline bag.
    • For a Right PComm: Single pin of the Mayfield in the left mid-pupillary line. Double pins straddling the inion. Tighten to 80 pounds.
    • Start with the head neutral. Extend 20-30 degrees and rotate to the left 20 degrees so that the malar eminence of the zygoma is highest point of the field.
  • Incision
    • The incision will extend from the root of the zygoma (within 1cm from the tragus) to the midline. To draw the incision place your hand on the eye, start at the zygoma, and draw an arc to the widow’s peak (midline)
    • Mark out a spot for EVD (Kocher’s point)
  • Operative details
    • Incision- Start at the midline and take the knife all the way to the bone until you get to the superior temporal line. Extend the incision above the temporalis fascia and place raney clips. Open the temporalis down to the root of the zygoma with the bovie and reflect the flap with a periosteal
    • Craniotomy- Place burr holes inferiorly (squamous temporal bone above the zygoma), posteriorly along the superior temporal line, and anteriorly at the keyhole. Turn the bone flap up onto the frontal bone within 5cm of midline, as close to the frontal sinus as you dare, low on the sphenoid wing, and temporally. Drill the sphenoid wing down as much as possible as this is going to be your route down to the opticocarotid triangle. To remove the sphenoid wing use a Leksell, mastoid, and then a drill. Control bleeding from the bone with bone wax on a penfield 4 or a direct injection of surgiflo (pack with a patty). Once you open the dura it is a pain to remove more bone so spend enough time to optimize your dural exposure.
    • Dural opening- Make a curvilinear incision from the frontal à temporal and reflect the dura anteriorly. Tack (don’t sew to flap) as you may have to do a dolenc (but probably not)
    • Place Greenberg (Medium blade frontal, Large sylvian, Small temporal.
    • Approach- Under the microscope. Place a large “Drake sized and cut” gelfoam covering/protecting the frontal and temporal lobes while allowing access to the sylvian fissure. Follow the sphenoid wing anteriorly inferiorly as the anterior clinoid process will point at the optic nerve. The dura of the anterior cranial fossa floor converges with the cisternal arachnoid directly over the optic nerve. Open the arachnoid over the optic nerve and place the frontal retractor. Open the chiasmatic cistern medially to the interoptic triangle and posterolaterally to the opticocarotid triangle (carotid cistern) and sylvian cistern. Open the proximal (aka sphenoidal segment) of the sylvian fissure. There is usually a small vein that needs to be taken to split the proximal fissure. Connect the split sylvian fissure to the carotid in the opticocarotid recess.
    • Pitfalls: Resist the temptation to place a retractor on the temporal lobe as the aneurysm dome may be adherent to the uncus and can increase the risk of rupture
    • Proximal Control- To get good proximal control, follow the ICA anteriorly to where it cross under CN 2. You may have to open the falciform ligament slightly to get a temporary clip around the ICA.
  • Aneurysm dissection- with proximal control established and the sylvian fissure split begin the dome dissection
    • The PComm origin is heading away from you and underneath the ICA (ie it’s hard to see). Try to dissect the proximal end of the dome and then open the opticocarotid triangle more widely to see the distal PComm.
    • You have probably already found the Anterior choroidal and can follow the ICA back proximally to find the distal neck of the aneurysm.
    • Clipping- place a clip (normally an aesculap 727 clip) across the dome
    • Inspect, remove temporary clip (if placed), and evaluate with Doppler/ICG
  • Postop Orders
    • SBP <160 (generalize BP parameters once clipped)
    • Drain EVD at Pop 15
    • 0400 Head CT

 

 

Joseph MillerPterional craniotomy for Posterior Communicating Artery Aneurysm

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