Violation

Vascular neurosurgery is a refined art. The dexterity, grace, and precision of a master neurosurgeon are awe-inspiring; the movement of microsurgical instruments among arteries and nerves is like a ballet; and the otherworld of anatomy underneath the brain is exquisite. Vascular neurosurgeons pride themselves on their ability to reach remote territories through the subarachnoid space without having to violate the brain. Therefore, dissections that violate pia and transgress brain are disappointing and a little embarrassing. Brain transgression stirs an unnatural feeling, but resection of some brain has clear advantages in certain situations.

Gyrus Rectus

The gyrus rectus resection is the best example of tissue removal that improves access to and visualization of an aneurysm. This gyrus lies in the surgical corridor between the olfactory tract and the interhemispheric fissure and can block exposure of the ipsilateral A2 segment and proximal neck. Gentle retraction with a retractor blade lateral to the olfactory tract causes the brain tissue to bulge over the tip of the blade. Pia is coagulated and incised to enter the brain. Cautery and suction are used to remove tissue. The orbitofrontal artery often courses over the middle of the gyrus rectus, and two pial openings on both sides of the artery preserve it while allowing brain removal beneath it. Resection continues until pia on the opposite side of the lobule is reached or until sufficient room is created around the aneurysm. Bleeding is controlled within the resection cavity with cautery, and the retractor is repositioned with its tip at the deep pial plane.

Brain resection is performed subpially to safely avoid the aneurysm as well as arteries and veins in the subarachnoid space. Any artery of importance, specifically the recurrent artery of Heubner, is identified and dissected away from the lobule before any brain is resected. Inadvertent injury to this artery is the biggest risk of this maneuver, and it should not be performed if the artery cannot be protected. The recurrent artery of Heubner is freed completely from the frontal lobe, following a plane of dissection from the shoulder of its origin from the A2 segment, along the A1 segment, to well beyond the gyrus rectus.

After the gyrus rectus is resected, the subarachnoid plane is reestablished in the interhemispheric fissure. The inner surface of this deep pia is cauterized, inspected, and incised carefully to avoid injury to underlying arteries or the aneurysm itself. The ipsilateral A2 segment is identified in the fissure and traced proximally to the aneurysm.

Dome Avoidance

Brain transgression removes surgical obstacles such as the gyrus rectus, but is equally important in avoiding dangerous dissection adjacent to aneurysm domes. With middle cerebral artery (MCA) aneurysms, the dome may adhere to the superior temporal gyrus or the posterior pars orbitalis in the frontal lobe, thereby blocking access to the underlying inferior and superior trunks, respectively. With ophthalmic artery aneurysms, the dome may adhere to the medial orbital gyrus and limit frontal lobe retraction needed for an anterior clinoidectomy. With pericallosal artery aneurysms, the dome may adhere to the cingulate gyrus and interfere with the dissection of afferent arteries. By deliberately leaving the subarachnoid space, the sometimes tight plane between a thin aneurysm and the adherent pia is avoided. After reestablishing the subarachnoid plane beyond the point of adhesion, a thin patch of brain and pia remains attached to the aneurysm dome. The aneurysm becomes untethered and can be mobilized safely.

Brain Relaxation

Swollen Brain

In some cases of swollen brain without frank hematoma, resection of brain tissue may be needed to expose the aneurysm. For example, with a basilar bifurcation aneurysm and a swollen temporal lobe, the uncus may narrow the surgical corridor of the carotid-oculomotor triangle. Subpial resection of some uncus may facilitate retraction and widen the exposure. The uncus is not eloquent or associated with neurologic deficits after resection. Therefore, the advantages of facilitated dissection, enhanced exposure, and relieved intracranial pressure outweigh any morbidity from limited brain resection. In these instances, our natural aversion to brain transgression can and should be dismissed.