20 Omental–Cranial Transposition
Abstract
Selective moyamoya disease (MMD) patients have progressive neurological deterioration despite previous revascularization, and many have exhausted typical sources for bypass or have wide ischemic areas needing further revascularization. Omental–cranial transposition, a technique used sparingly, can be performed efficiently and safely. In this chapter, we highlight the steps and nuances in performing the laparoscopic omental harvest (which is better tolerated than laparotomy), the techniques used to ensure a thin, homogeneous, pedicled omental flap to provide wide cerebral hemispheric coverage, and illustrate with the appropriate case examples. We also include the preoperative workup, intraoperative strategies with step-by-step descriptions of key procedures, and postoperative management with long-term clinical and radiological outcome. With this method, we can achieve excellent angiographic revascularization and symptoms resolution for selective patients with resistant MMD.
20.1 Background
Revascularizations for moyamoya disease (MMD), either by direct or indirect procedures, are an accepted and effective treatment for the prevention of future ischemic events. However, small subsets of patients have persistent or new symptoms due to inadequate collateralization, hence, repeat revascularizations are performed. These repeat surgeries are technically more challenging due to scar tissue from the previous surgery, the meticulous attention required to avoid violating the previous bypass donor and its collateralization, and the lack of suitable local donor grafts. We describe the omental–cranial transposition as one of the rescue strategies that could be employed in these circumstances.
20.1.1 History
1936—O’Shaughnessy sutured a pedicle of omentum to the heart.
1962 to 1975—Vineberg explored clinical omental transposition to the heart.
1973—Goldsmith et al described the first experimental omental–cranial flap in dogs to promote brain revascularization.
1974 and 1977—Yasargil, Yonekawa, and their colleagues explored the use of omentum transplantation in animal models for the treatment of hydrocephalus and cerebral ischemia.
1980—Karasawa et al described the first use of an omental flap in a patient with MMD who presented with ischemic symptoms. Anastomoses were made between the corresponding artery and vein of the superficial temporal and gastroepiploic vessels. The patient was free of ischemic attacks at 2 years follow-up.
20.2 Indications
Revascularization of MMD in the absence of superficial temporal artery (STA), occipital artery or muscle donor.
Large cortical surface areas to be revascularized, including bilateral hemispheres.
Commonly employed strategy for repeat revascularization of MMD.
20.3 Key Principles
Laparoscopic omental graft harvest in conjunction with the general surgeon.
Preservation of gastroduodenal artery/vein and right gastroepiploic artery/vein blood supply.
Careful delivery of the omentum to the cranial compartment.
20.4 SWOT Analysis
20.4.1 Strength
Stretches and conforms easily to cover a large cortical area.
20.4.2 Weakness
Technically challenging, potential associated morbidity with abdominal surgery.
20.4.3 Opportunity
Stem cells in omentum produce angiogenesis-promoting cytokines, for example, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF).
20.4.4 Threat
The viability of the omental graft could be compromised if the gastroepiploic artery is not preserved during harvest, or significant graft torsion occurs in the process of extraperitoneal omental delivery or tunneling to the cranial compartment.
20.5 Contraindications
Previous complex abdominal surgery.
Abdominal adhesion (peritonitis, peritoneal dialysis).
Scarred down chest wall, difficulty with tunneling (relative contraindication).
20.6 Special Considerations
History of previous major abdominal surgery should be carefully considered when contemplating omental–cranial harvest.
Cortical areas to be revascularized: if located superior in the cerebral hemispheres (difficulty revascularizing using donor vessels due to inadequate length and small size of distal vessel), or a wide cortical surface area is to be reperfused (including bilateral hemispheres), the omental graft is a very good option.
20.7 Risk Assessment: Our Experience
At Stanford, we have performed 25 omental–cerebral transpositions for MMD (with 10 additional for non-MMD stroke patients).
1991 to 2000: 9 cases with laparotomy for omental graft harvest (3 pedicled and 6 free grafts).
2011 to 2016: 16 cases with laparoscopic harvesting of pedicled omental grafts.
In our laparoscopic omental–cranial transposition experience, 17 hemispheres in 16 patients were revascularized.
Ages ranged from 5 to 45 years old, mean follow-up of 10.8 years (range: 1–27 years).
Three patients had small postoperative diffusion weighted imaging (DWI) plus infarcts on MRI of the brain associated with contralateral arm and/or hand weakness, which recovered to preoperative baseline over 2 to 3 months. Two additional patients developed transient neurological deficits (TNDs) in the 30-day postoperative period that resolved.
At the last follow-up, angiographic and MR findings of all cases showed patent grafts as well as viable omentum, and all patients experienced preoperative symptom resolution or improvement.
20.8 Preoperative Workup
Preoperatively, patients undergo a thorough medical, cardiac, and anesthetic assessment with routine preoperative labs and the relevant diagnostic imaging, including five-vessel cerebral angiogram, MRI of the brain, and cerebral perfusion imaging with and without Diamox (positron emission tomography, MR perfusion, CT perfusion, single-photon emission computed tomography [SPECT], transcranial Doppler). At our institution, we perform MR perfusion with and without Diamox, and patients who demonstrate poor cerebrovascular reserve (CVR) with steal phenomenon (indicating that the affected vascular territory is already maximally vasodilated to promote flow) are considered, especially patients of high risk for ongoing ischemia without treatment. These patients are also at higher risk for perioperative ischemic complications; thus, particular care is taken to avoid hypotension perioperatively and during the recovery period. Intraoperatively, each patient’s blood pressure is maintained at or above the preoperative baseline at all times.
20.8.1 Specific Consideration with Anticoagulation
For patients with mechanical heart valves or recent venous thromboembolism, we would restart anticoagulation at 2 to 4 weeks postoperatively after a head CT confirmed no significant hemorrhage.
Aspirin is continued through the preoperative day and restarted on postoperative day 1.
20.9 Patient Preparation
20.9.1 Patient Position with Skin Incision
The laparoscopic surgical and neurosurgical teams work simultaneously.
The patient is positioned supine.
The head is positioned on a doughnut headrest to bring the cortical area to be revascularized uppermost.
A transverse lower neck incision is made for tunneling of the omental graft from the peritoneal cavity to the cervical region over the chest wall. A retroauricular pocket is also created to connect the craniotomy site to the cervical incision.
A lithotomy position is used.
Laparoscopic port site insertion (three times), a subxiphoid incision is made to deliver the omentum after harvest.
Fig. 20.1 Patient positioned with the neurosurgical and pediatric laparoscopic surgical team working simultaneously. (Used with permission from Navarro R, Chao K, Gooderham PA, Bruzoni M, Dutta S, Steinberg GK. Less invasive pedicled omental-cranial transposition in pediatric patients with moyamoya disease and failed prior revascularization. Neurosurgery. 2014;10:1–14.)
20.10Surgical Steps
20.10.1 Key Procedural Step 1: Omental Harvest
Fig. 20‑2 a–c illustrates the key anatomical landmarks of the omental harvest stage. Fig. 20‑2 d–f shows the senior author’s early technique with open omental harvest.
Laparoscopic omental harvest through working ports.
Omentum dissected off the transverse colon, then splenic flexure (avoiding splenic vessel injury), and hepatic flexure.
Dissection is along the greater curve of the stomach, preserving the right gastroepiploic artery and vein; the left gastroepiploic is cut.
The pedicle is preserved at the pylorus.
Fig. 20.2 (a) Anatomy of the greater omentum relative to the greater curve of the stomach and transverse colon. (b) Blood supply to the greater omentum including the gastroepiploic artery and the arch of Barkow. (c) The course of the right gastroepiploic artery along the greater curve of the stomach, and subsequent division at the left gastroepiploic artery during the omental harvest. (d) The open omental harvest technique as performed in the senior author’s early experience, dividing the greater omentum from the transverse colon. (e) Division of the greater omentum from the greater curve of stomach, preserving the right gastroepiploic artery, and dividing the left gastroepiploic artery. (f) An illustration of how to lengthen the omental graft and preserving the blood supply by dividing along the arches of the anterior epiploic branches. Panel (a) is from Henry Gray (1918) Anatomy of the Human Body. Available at: Bartleby.com: Gray‘s Anatomy, Plate 1035. Panel (b) is reprinted from The Technique of Omentum Harvest for Intrathoracic Use. Boulton BJ and Force S. 2010, with permission from Elsevier. Panel (c) is with permission from Jensen, Surgical Anatomy and Mastery of Open Operations: A Multimedia Curriculum for Training Residents, Wolters Kluwer. Panels (d–f) are used with permission from Cockroft KM, Mahoney ME, Cobb LF, Steinberg GK: Omental Cerebral Transposition. In: Steinberg GK, (Ed.). Techniques in Neurosurgery: Cerebral Revascularization Techniques. Philadelphia, PA: Lippincott Williams and Wilkins, 2000 (vol. 6, issue 2), pp. 172–181.
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