E. Sander Connolly Jr.
William W. Ashley Jr., Sepideh Amin-Hanjani, Ali Alaraj, John H. Shin and Fady T. Charbel
✓Extracranial–intracranial bypass surgery has advanced from a mere technical feat to a procedure requiring careful patient selection and a justifiable decision-making paradigm. Currently available technologies for flow measurement in the perioperative and intraoperative setting allow a more structured and analytical approach to decision making. The purpose of this report is to review the use of flow measurement in cerebral revascularization, presenting algorithms for flow-assisted surgical planning, technique, and surveillance.
Ali Alaraj, William W. Ashley Jr., Fady T. Charbel and Sepideh Amin-Hanjani
The superficial temporal artery (STA) is the mainstay of donor vessels for extracranial–intracranial bypass in cerebral revascularization. However, the typically used STA anterior or posterior branch is not always adequate in its flow-carrying capacity. In this report the authors describe the use of the STA trunk at the level of the zygoma as an alternative donor and highlight the benefits and pitfalls of this revascularization option.
The authors reviewed the cases of 4 patients in whom the STA trunk was used as a donor site for anastomosis of a short interposition vein graft. The graft was implanted into the middle cerebral artery to trap a cartoid aneurysm in 2 patients, and the posterior cerebral artery for vertebrobasilar insufficiency in the other 2. Discrepancies in size between the interposition vein and STA trunk were compensated for by a beveled end-to-end anastomosis or by implanting the STA trunk into the vein graft in an end-to-side fashion.
Intraoperative flow measurements confirmed the significantly higher flow-carrying capacity of the STA trunk (54–100 ml/minute) compared with its branches (10–28 ml/minute). The STA trunk interposition graft has several advantages compared with an interposition graft to the cervical carotid, including a shorter graft and no need for a neck incision. However, in the setting of ruptured aneurysm trapping, with the risk of subsequent vasospasm, it is a poor conduit for endovascular therapies.
The STA trunk is a valuable donor option for cerebral revascularization, but should be avoided in the setting of subarachnoid hemorrhage.
David H. Jho, Sergey Neckrysh, Julian Hardman, Fady T. Charbel and Sepideh Amin-Hanjani
✓ The authors evaluated the effectiveness of a simple technique using ethylene oxide (EtO) gas sterilization and room temperature storage of autologous bone grafts for reconstructive cranioplasty following decompressive craniectomy. The authors retrospectively analyzed data in 103 consecutive patients who underwent cranioplasty following decompressive craniectomy for any cause at the University of Illinois at Chicago between 1999 and 2005. Patients with a pre-existing intracranial infection prior to craniectomy or lost to follow-up before reconstruction were excluded. Autologous bone grafts were cleansed of soft tissue, hermetically sealed in sterilization pouches for EtO gas sterilization, and stored at room temperature until reconstructive cranioplasty was performed.
Cranioplasties were performed an average of 4 months after decompressive craniectomy, and the follow-up after reconstruction averaged 14 months. Excellent aesthetic and functional results after single-stage reconstruction were achieved in 95 patients (92.2%) as confirmed on computed tomography. An infection of the bone flap occurred in eight patients (7.8%), and the skull defects were eventually reconstructed using polymethylmethacrylate with satisfactory results. The mean preservation interval was 3.8 months in patients with uninfected flaps and 6.4 months in those with infected flaps (p = 0.02). A preservation time beyond 10 months was associated with a significantly increased risk of flap infection postcranioplasty (odds ratio [OR] 10.8, p = 0.02). Additionally, patients who had undergone multiple craniotomies demonstrated a trend toward increased infection rates (OR 3.0, p = 0.13).
Data in this analysis support the effectiveness of this method, which can be performed at any institution that provides EtO gas sterilization services. The findings also suggest that bone flaps preserved beyond 10 months using this technique should be discarded or resterilized prior to reconstruction.
Mateo Calderon-Arnulphi, Ali Alaraj, Sepideh Amin-Hanjani, William W. Mantulin, Chiara M. Polzonetti, Enrico Gratton and Fady T. Charbel
There is great value in monitoring for signs of ischemia during neurovascular procedures. Current intraoperative monitoring techniques provide real-time feedback with limited accuracy. Quantitative frequency-domain near-infrared spectroscopy (Q-NIRS) allows measurement of tissue oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (tHb) concentrations and brain tissue oxygen saturation (SO2), which could be useful when monitoring for evidence of intraoperative ischemia.
Using Q-NIRS, the authors monitored 25 neurovascular procedures including aneurysm clip placement, arteriovenous malformation resection, carotid endarterectomy, superficial temporal artery–middle cerebral artery (MCA) bypass surgery, external carotid artery–MCA bypass surgery, encephaloduromyosynangiosis, and balloon occlusion testing. The Q-NIRS technology provides measurable cerebral oxygenation values independent from those of the scalp tissue. Thus, alterations in the variables measured with Q-NIRS quantitatively reflect cerebral tissue perfusion. Bilateral monitoring was performed in all cases.
Five of the patients exhibited evidence of clinical ischemic events during the procedures. One patient suffered blood loss with systemic hypotension and developed diffuse brain edema intraoperatively, one patient suffered an ischemic event intraoperatively and developed an occipital stroke postoperatively, and one patient showed slowing on electroencephalography intraoperatively during carotid clamping; in two patients balloon occlusion testing failed. In all cases of ischemic events occurring during the procedure, Q-NIRS monitoring showed a decrease in HbO2, tHb, and SO2, and an increase in HHb.
Quantitative frequency-domain near-infrared spectroscopy provides quantifiable and continuous real-time information about brain oxygenation and hemodynamics in a noninvasive manner. This continuous intraoperative oxygenation monitoring is a promising method for detecting ischemic events during neurovascular procedures.
Sepideh Amin-Hanjani, John H. Shin, Meide Zhao, Xinjian Du and Fady T. Charbel
To date, angiography has been the primary modality for assessing graft patency following extracranial–intracranial bypass. The utility of a noninvasive and quantitative method of assessing bypass function postoperatively was evaluated using quantitative magnetic resonance (MR) angiography.
One hundred one cases of bypass surgery performed over a 5.5-year period at a single institution were reviewed. In 62 cases, both angiographic and quantitative MR angiographic data were available. Intraoperative flow measurements were available in 13 cases in which quantitative MR angiography was performed during the early postoperative period (within 48 hours after surgery).
There was excellent correlation between quantitative MR angiographic flow and angiographic findings over the mean 10 months of imaging follow up. Occluded bypasses were consistently absent on quantitative MR angiograms (four cases). The flow rates were significantly lower in those bypasses that became stenotic or reduced in diameter as demonstrated by follow-up angiography (nine cases) than in those bypasses that remained fully patent (mean ± standard error of the mean, 37 ± 13 ml/minute compared with 105 ± 7 ml/minute, p = 0.001). Flows were appreciably lower in poorly functioning bypasses for both vein and in situ arterial grafts. All angiographically poor bypasses (nine cases) were identifiable by absolute flows of less than 20 ml/minute or a reduction in flow greater than 30% within 3 months. Good correlation was seen between intraoperative flow measurements and early postoperative quantitative MR angiographic flow measurements (13 cases, Pearson correlation coefficient = 0.70, p = 0.02).
Bypass grafts can be assessed in a noninvasive fashion by using quantitative MR angiography. This imaging modality provides not only information regarding patency as shown by conventional angiography, but also a quantitative assessment of bypass function. In this study, a low or rapidly decreasing flow was indicative of a shrunken or stenotic graft. Quantitative MR angiography may provide an alternative to standard angiography for serial follow up of bypass grafts.
Sepideh Amin-Hanjani, William E. Butler, Christopher S. Ogilvy, Bob S. Carter and Fred G. Barker II
Object. The authors assessed the results of extracranial—intracranial (EC—IC) bypass surgery in the treatment of occlusive cerebrovascular disease and intracranial aneurysms in the US between 1992 and 2001 by using population-based methods.
Methods. This is a retrospective cohort study based on data from the Nationwide Inpatient Sample (Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality, Rockville, MD). Five hundred fifty-eight operations were performed at 158 hospitals by 115 identified surgeons. The indications for surgery were cerebral ischemia in 74% of the operations (2.4% mortality rate), unruptured aneurysms in 19% of the operations (7.7% mortality rate), and ruptured aneurysms in 7% of the operations (21% mortality rate). Overall, 4.6% of the patients died and 4.7% of the patients were discharged to long-term facilities, 16.4% to short-term facilities, and 74.2% to their homes. The annual number of admissions in the US increased from 190 per year (1992–1996) to 360 per year (1997–2001), whereas the mortality rates increased from 2.8% (1992–1996) to 5.7% (1997–2001).
The median annual number of procedures was three per hospital (range one–27 operations) or two per surgeon (range one–21 operations). For 29% of patients, their bypass procedure was the only one recorded at their particular hospital during that year; for these institutions the mean annual caseload was 0.4 admissions per year. For 42% of patients, their particular surgeon performed no other bypass procedure during that year. Older patient age (p < 0.001) and African-American race (p = 0.005) were risk factors for adverse outcome. In a multivariate analysis in which adjustments were made for age, sex, race, diagnosis, admission type, geographic region, medical comorbidity, and year of surgery, high-volume hospitals less frequently had an adverse discharge disposition (odds ratio 0.54, p = 0.03).
Conclusions. Most EC—IC bypasses performed in the US during the last decade were performed for occlusive cerebrovascular disease. Community mortality rates for aneurysm treatment including bypass procedures currently exceed published values from specialized centers and, during the period under study, the mortality rates increased with time for all diagnostic subgroups. This technically demanding procedure has become a very low-volume operation at most US centers.
Nicholas C. Bambakidis, L. Fernando Gonzalez, Sepideh Amin-Hanjani, Vivek R. Deshmukh, Randall W. Porter, Philip C. Daspit and Robert F. Spetzler
Combined approaches to the skull base provide maximal exposure of the complex and eloquent anatomical structures contained within the posterior fossa. Common to these combined exposures are variable degrees of petrous bone removal. Understanding the advantages of each approach is critical when attempting to balance increases in operative exposure against the risk of potential complications. Despite their risks, aggressive combined exposures to the posterior fossa enable the greatest degree of visualization of the anatomy. Consequently, surgeons can approach lesions with maximal margins of safety, which cannot otherwise be realized. To minimize morbidity in all cases, the approach chosen must be applied individually, depending on the lesion and the patient's characteristics.