32 Posterior Communicating Artery Aneurysm

Case 32 Posterior Communicating Artery Aneurysm

Pascal M. Jabbour and Erol Veznedaroglu

Fig. 32.1 Computed tomography scan of the head showing diff use subarachnoid hemorrhage.

Fig. 32.2 Cerebral angiogram, right carotid injection showing a cerebral aneurysm.

Clinical Presentation

A 64-year-old right-handed woman with a history of high blood pressure and smoking presents to the emergency room after experiencing the worst headache of her life while she was driving her car.

She does not have a history of migraine headaches and never complained of headaches before this episode.

Her familial history is significant—a maternal aunt died 10 years ago from a ruptured brain aneurysm.

Neurologic evaluation showed that the patient was alert, awake-oriented, with a dilated nonreactive pupil on the right side, with decreased ocular motility upward, inward and downward.

A computed tomography (CT) scan of the head is shown in Fig. 32.1 and a cerebral angiogram is shown in Fig. 32.2.

Questions

What is the most likely diagnosis based on clinical history?
What are this patient’s Hunt & Hess and Fisher grades?
What are the risk factors for subarachnoid hemorrhage (SAH) in this patient?
How are the findings on the clinical examination of this patient relevant; and where is most likely the anatomical location of the lesion based on the imaging studies provided?
What are the treatment options available for this patient?
You opt to proceed with surgical repair. Describe the details of the operation including positioning, opening, details of dissection and repair, closure, and other assistive measures.

Answers

What is the most likely diagnosis of this patient?

The patient experienced the worst headache of her life, with no previous history of headaches. This is highly suspicious of SAH.

What are this patient’s Hunt & Hess and Fisher grades?

The patient has a Hunt & Hess grade 2 and a Fisher grade 3.1,2
What are the risk factors for SAH in this patient?
- Female, high blood pressure, smoker, and familial history of aneurysms.³
How are the findings on the clinical examination of this patient relevant and where is the most likely anatomic location of the lesion based on the imaging studies provided?
- The patient has a partial third nerve palsy involving the pupil.
- Most probably the patient has a right posterior communicating artery (PCOM) aneurysm because of the proximity of the third nerve to the PCOM.
What are the treatment options available for this patient?
- The patient’s treatment options are either open surgery and clip ligation of the aneurysm or endovascular treatment with coils, depending on the patient’s comorbidities, the shape of the aneurysm and the neck, and the preference of the surgeon. The literature is not clear about whether any of the modalities are better for the third nerve recovery.^4–6
You opt to proceed with surgical repair. Describe the details of the operation including positioning, opening, details of dissection and repair, closure and other assistive measures.
- Positioning and preoperative preparation
  - Supine, shoulder roll, head rotated 45 degrees, Mayfield 3-point fixation
  - Preoperative antibiotics, mannitol, furosemide available
  - Phenobarbital or etomidate available
  - Ventriculostomy ready to be placed
  - Assistive devices: microscope, loops, headlight, ultrasound; if have intraoperative angiography, have it ready
  - Retractors: Greenberg, Fukushima; Lela bar or Budde halo
  - Consider somatosensory evoked potential, electroencephalogram intraoperatively if feasible.
  - Anesthetize the pin sites before pinning.
  - Prepare the neck for possible early proximal control.
- Opening and dissection
  - Curvilinear incision, pterional craniotomy
  - Take down sphenoid wing extradurally down to the meningo-orbital artery.
  - Clinoid may have to be partially removed to obtain adequate exposure and proximal control of the internal carotid artery.
  - Wax all bone edges to prevent air embolism.
  - Place tack-up sutures.
  - Open the dura based on sphenoid wing.
  - Split the fissure under the microscope from proximal to distal.
  - Open between the veins and frontal cortex.
  - May place retractors on frontal lobe and gently start sharp dissection.
  - Identify the optic nerve and carotid artery and dissect the carotid to be able to place a proximal clip.
  - Work your way back to identify the carotid bifurcation.
  - Wide opening of the sylvian fissure greatly facilitates the safety of clipping.
  - Dissection done with caution in laterally projecting aneurysms to avoid avulsion of the fundus from the temporal lobe attachments.
  - Approach directed more frontal is preferred until the aneurysm neck is visualized.
- Clipping and precautions
  - May then place temporary clips and work on dissecting the neck and dome
  - Note: Can temporarily clip internal carotid artery up to 15 minutes before opening and reperfusing the brain.
  - Use systemic hypertension, phenobarbital or etomidate, mild hypothermia, mannitol during temporary clip.
  - Dissect neck before the dome, then place clip, then dissect dome and check for perforators
  - Advance the clip just beyond the course of the PCOM, without compromising the patency of that artery or that of the anterior thalamoperforators, internal carotid perforators, or anterior choroidal artery.
  - Use ultrasound to the dome to verify that there is no flow.
  - If no flow and no perforators, open the dome.
  - Open the membrane of Liliequist widely to visualize and release any tethering or compromise of the PCOM and its thalamoperforating vessels.
  - Obtain intraoperative angiogram if possible to confirm patency.
- Closure
  - Close and transfer to intensive care unit.
  - Obtain immediate postoperative CT and angiogram as well as neurologic exam.^7,8