Arterial

Internal Carotid Artery

The most important vessel that is related to the transsphenoidal approach is the ICA. The cavernous ICA is the most common segment that is encountered during routine transsphenoidal surgery. However, with the advent of endoscopy, more extended transsphenoidal approaches are being done where other segments of ICA, starting from the petrous ICA to the supraclinoid ICA, are exposed. Fig. 37.1A illustrates a standard view of transsphenoidal surgery, showing the anatomy of the ICA in relation to sella. Intercarotid distance (ICD) between cavernous carotid arteries (CCAs) is 15 to 17 mm on MR coronal images in healthy individuals. This distance increases to 20 to 22 mm for patients with pituitary adenomas. Anterior and posterior parts of the CCAs are usually closer to the midline sagittal plane in comparison with the middle part of the CCAs. The anterior horizontal segment of the CCA was close to the pituitary gland in most of the specimens in an anatomic study. Renn and Rhoton found the shortest distance between the two carotid arteries in the supraclinoid area in 82% of cases, in the cavernous sinus along the side of the sella in 14%, and in the sphenoid sinus in 4%. In 10% of cases, CCAs were within 4 mm of the midline. Ectasia of cavernous ICA or kissing carotid artery can pose a significant challenge and may force the surgeon to access a different route. This dolichoectasia may be seen in pituitary fossa, sphenoid bone or sinus, and it is more common in acromegalic patients. Protrusion of ICA into sphenoid sinus occurs in 25% to 30% of cases. The dehiscence of the bony sphenoidal wall of the ICA occurred in about 10% of cases. Bilateral involvement may be seen in 1% of cases. The anatomic differences must be noted especially in acromegalic patients where the ICD is significantly smaller than in nonacromegalic patients. Interestingly, cavernous sinus invasion of adenoma was found to be independently associated with ICD contraction >2 mm (P = 0.027) in postoperative images. But a pituitary adenoma encasing ICA rarely causes compression of the artery (only 1.7%).

Illustrations showing endoscopic anatomy of the sellar region (A) and the sphenopalatine artery (B); (a) intercarotid distance (ICD) at anterior aspect of sella near planum sphenoidate; (b) ICD at the middle part of sella; (c) ICD at posterior aspect of sella near clivus. AICS, Anterior intercavernous sinus; CA, carotid artery; CL, clivus; CO, choanae; CS, cavernous sinus; NPA, nasopalatine artery; PG, pituitary gland; PICS, posterior intercavernous sinus; PNA, posterior nasal artery; PS, planum sphenoidate; SPA, sphenopalatine artery; SSO, sphenoid sinus osteum. Note: Anterior and posterior intercavernous sinuses are observed as two blue lines during pituitary surgery and guide the limit of the dural opening.

Arterial bleeding may also arise from the branches of ICA, such as the inferior hypophyseal artery or a small capsular artery. With the increasing use of the endoscope, an injury to the A1–A2 complex with its perforating vessels or basilar or posterior cerebral arteries is possible while approaching suprasellar and retrosellar pathologies.

Association of intracranial aneurysm and pituitary adenoma has been discussed in the literature. Though this rare occurrence does not merit any added workup, the possibility should be kept in mind in the context of an anticipated torrential bleeding.

Venous

Intercavernous sinuses are seen as two blue lines in the anterior and posterior part of the pituitary gland, which guides the anterior and posterior limit of the dural opening, respectively. The variation in the anatomy of the intercavernous sinus must be emphasized while planning dural opening. In case of microadenoma, especially in a case of Cushing’s disease, the entire sellar dura may be covered by a venous channel, and torrential bleeding may initiate as soon as the incision is placed on the dura.

Steps to Control Torrential Bleeding

It is preferable that two surgeons be engaged, allowing one surgeon to control the bloodstream, directing it away from the endoscope, while the other obtains visualization to attempt hemostasis. The packing of sella and/or of the sphenoid sinus should be performed by moving the endoscope back to the level of the head of the middle turbinate and inserting the hemostatic substances under endoscopic control. Two large-bore (10F) suction devices and a lens cleaning system for the endoscope will be helpful in this scenario. An endoscope equipped with an irrigating system enables continuous cleaning of the distal lens. The primary surgeon may place the endoscope down the contralateral side, using the posterior septal edge as a shield from the blood flow. Also he must try to clear blood ahead of the endoscope using the second suction device. A pedicled septal flap should also be cleared and pushed into the nasopharynx. At the same time, the second surgeon uses suction downside the nose with predominant bleeding to direct flow away from the other side. The second surgeon is then free to “hover” the suction device directly over the site of injury to help gain visualization for the primary surgeon. Nevertheless, neurosurgeons with less training on the endoscope must be prepared to swap the endoscope for the speculum and the microscope to avoid delay in endoscopic control of bleeding.

Hemostasis: Maneuvers and Materials

Several maneuvers have been discussed in the literature to aid the control of bleeding. The efficacy of head elevation and controlled hypotension, a common practice, is doubtful. Ipsilateral common carotid artery compression can allow time for adequate nasal packing. Weidenbecher et al. advocated bilateral carotid artery compression in the neck with concurrent surgical widening of the sphenoid sinus ostium to facilitate nasal pack placement. It is also widely recommended that normotension be maintained through resuscitative measures to preserve adequate cerebral perfusion. Several packing agents have been described in the literature. These include Teflon (Medox Medical, Oakland, NJ) and methyl methacrylate patch, fibrin glue, Gelfoam (Pfizer, New York City, NY), oxidized cellulose packing thrombin-gelatin matrix, oxygel, and glue and muslin gauze. Muscle patch from fascia lata, sternocleidomastoid, or quadriceps may be used, along with oxidized cellulose and fibrin glue. Despite numerous options, gauze was most frequently used due to its availability and ease of use. Packing is not without its own complications. Overpacking can contribute to ICA occlusion/stenosis leading to increased morbidity and mortality.

Open and Endovascular Treatment Options

A direct suture repair or a Sundt-type clip graft has been described. A U-clip anastomotic device or T2 aneurysm clip (Mizuho, Tokyo, Japan) may be useful as well. Electrocauterization is often performed to gain rapid hemostasis, but this can potentially lead to carotid occlusion or delayed secondary hemorrhage and therefore cannot be recommended. However, bleeding from intercavernous sinus may be successfully controlled with electrocautery, if two layers of dura can be approximated together.

Endovascular options have become frontline choices in present days. However, treatment options may vary according to type of injury and time of identification. Though ICA preservation is always the goal, sacrificing ICA remains the definitive treatment in acute uncontrollable bleeding. Balloon occlusion test (BOT) or some form of angiographic assessment of collateral circulation should be performed before sacrifice of ICA because permanent neurologic complication occurs in approximately one-fifth of them. A covered stent may be considered as a valuable option in active bleeding or Carotico-Cavernous fistula (CCF) (JoStent: Jomed International and Symbiot self-expanding stent). However, the rigidity of a covered stent can be a concern because negotiation into tortuous cavernous ICA may be difficult and occlusion of branching arteries is not uncommon. Vasospasm and in-stent thrombosis are other potential complications. Kim et al. have advised use of abciximab to treat in-stent thrombosis.

Patients with pseudoaneurysm should be started with dual antiplatelet therapy whenever possible. A covered stent is a reasonable option here as well. A stent-assisted coiling (Enterprise and Neuroform) is useful for wide-necked and traumatic pseudoaneurysms. Pipeline embolization device, the first flow-diverting device approved by US Food and Drug Administration for intracranial use, can successfully lead to complete exclusion of a pseudoaneurysm in 2 weeks to 6 months. Coil embolization without stent placement should be considered in pseudoaneurysms with poor collateral circulation. This strategy obviates the need for dual antiplatelet therapy. Luo et al. expressed doubt over use of coils alone for treatment of acute traumatic carotid aneurysms, citing inherent fragility, wide neck, and indistinct anatomy of these aneurysms. But it can certainly be considered as a bridge therapy. Onyx embolization may be another good treatment option.

What a Neurosurgeon Can Offer

Sacrifice of ICA with endovascular coiling should be considered strongly in cases of acute, uncontrolled bleeding. BTO may be considered to assess the collateral circulation before ICA sacrifice. It is difficult to perform any concrete test when the patient is already under general anesthesia, and neurologic deficit may be unavoidable. With increasing realm of endovascular surgery, ICA sacrifice may be discarded only as a last resort/salvage therapy. A high-flow extracranial-intracranial (EC-IC) bypass can be considered for patients with inadequate collaterals where vessel preservation is deemed difficult or proved a failure. A bypass surgery may be especially useful where the collateral is not adequate and a tortuous course of cavernous ICA prevents the implant of a stent.

Medical Treatment

Dual antiplatelet therapy is advised after stent graft or flow diverter placement to minimize the risk of stent thrombosis and distal emboli. However, the timing to start the treatment is controversial because the benefit must be weighed against the risk of increased perioperative hemorrhage. An active bleeding, a large pseudoaneurysm, and a significant mechanism of injury warrant immediate start of this therapy. The presence of a residual tumor could be a contraindication for initiation of dual antiplatelet therapy considering the increased risk of bleeding from healing vasculature within the tumor.