Middle Cerebral Artery Aneurysms: Pterional (Frontotemporal) Craniotomy for Clipping




Indications




  • •

    We prefer surgical clipping of most ruptured and unruptured middle cerebral artery (MCA) aneurysms because of the accessibility of their location and the relatively low morbidity and durability of clipping compared with endovascular therapy. The exception is in patients in poor neurologic condition (Hunt and Hess grade III, IV, or V); for these patients, we generally prefer endovascular treatment if feasible.


  • •

    The decision to treat an unruptured MCA aneurysm is based on an understanding of the natural history and must be weighed against the risk of surgical intervention. Factors that must be considered include the patient’s age, general health, clinical presentation (headaches, seizures), smoking history, family history of subarachnoid hemorrhage, and aneurysm size.





Contraindications




  • •

    Relative contraindications include advanced age, the presence of serious medical comorbidities, and poor neurologic condition. If treatment is contemplated in patients with these relative contraindications, endovascular coiling may be a reasonable alternative.





Planning and positioning




  • •

    Preoperative evaluation includes assessment of the patient’s cardiopulmonary status, laboratory values (complete blood count, basic metabolic profile, coagulation profile), chest x-ray, and electrocardiogram. The aneurysm configuration and associated vascular anatomy are defined by digital subtraction angiography with or without three-dimensional reconstruction, computed tomography angiography, or magnetic resonance angiography.


  • •

    The patient is given a dose of preoperative antibiotics before skin incision. Brain relaxation is achieved with intravenous mannitol and mild hyperventilation.




    Figure 24-1:


    The patient is positioned supine with the head elevated above the level of the heart. The head is placed in a three-pin fixation device and turned 30 degrees contralateral to the side of surgery with slight extension so that the malar eminence is highest in the surgical field. The scalp is shaved and sterilized in a standard fashion.



    Figure 24-2:


    The planned skin incision is marked starting at the level of the zygomatic arch just anterior to the tragus, to avoid injury to the frontalis branch of the facial nerve, and extended anterosuperiorly behind the hairline as a gentle curve to the midline.



    Figure 24-3:


    The skin is covered with self-adhesive transparent plastic. The incision line is infiltrated with a mixture of local anesthetic and epinephrine.





Procedure





Figure 24-4:


The skin incision is made layer by layer starting anteriorly where the scalp overlies the bone. An attempt is made to identify and preserve the frontal branch of the superficial temporal artery, which may be used for a bypass graft if needed. Raney clips are applied to the full thickness of the scalp to control bleeding. The temporalis fascia and muscle are cut posteriorly along the same line of the skin incision.



Figure 24-5:


A, Muscle is detached from the bone by subperiosteal dissection and elevated along with the scalp flap as a single musculocutaneous unit until the orbital rim and frontozygomatic suture are exposed. B, The scalp flap is reflected anteriorly over a roll of gauze to prevent acute angulation, which may compromise the vascular supply to the flap, and retracted with blunt fish hooks. Vigorous downward retraction of temporalis muscle toward the temporal fossa is important to avoid overhanging of muscle and obstruction of view. This retraction may be facilitated by cutting the anterior attachments of the muscle fibers and should be performed deep to the fat pad between the temporalis fascia and muscle to avoid injury of the frontalis branch. It is important to resuture the muscle anteriorly during closure to avoid a cosmetically unpleasant depression over the pterional region.

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Jun 15, 2019 | Posted by in NEUROSURGERY | Comments Off on Middle Cerebral Artery Aneurysms: Pterional (Frontotemporal) Craniotomy for Clipping

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