E. Sander Connolly Jr.
Sukhraaj Basati, Bhargav Desai, Ali Alaraj, Fady Charbel and Andreas Linninger
Experimental data about the evolution of intracranial volume and pressure in cases of hydrocephalus are limited due to the lack of available monitoring techniques. In this study, the authors validate intracranial CSF volume measurements within the lateral ventricle, while simultaneously using impedance sensors and pressure transducers in hydrocephalic animals.
A volume sensor was fabricated and connected to a catheter that was used as a shunt to withdraw CSF. In vitro bench-top calibration experiments were created to provide data for the animal experiments and to validate the sensors. To validate the measurement technique in a physiological system, hydrocephalus was induced in weanling rats by kaolin injection into the cisterna magna. At 28 days after induction, the sensor was implanted into the lateral ventricles. After sealing the skull using dental cement, an acute CSF drainage/infusion protocol consisting of 4 sequential phases was performed with a pump. Implant location was confirmed via radiography using intraventricular iohexol contrast administration.
Controlled CSF shunting in vivo with hydrocephalic rats resulted in precise and accurate sensor measurements (r = 0.98). Shunting resulted in a 17.3% maximum measurement error between measured volume and actual volume as assessed by a Bland-Altman plot. A secondary outcome confirmed that both ventricular volume and intracranial pressure decreased during CSF shunting and increased during infusion. Ventricular enlargement consistent with successful hydrocephalus induction was confirmed using imaging, as well as postmortem. These results indicate that volume monitoring is feasible for clinical cases of hydrocephalus.
This work marks a departure from traditional shunting systems currently used to treat hydrocephalus. The overall clinical application is to provide alternative monitoring and treatment options for patients. Future work includes development and testing of a chronic (long-term) volume monitoring system.
Michael Chan, Ali Alaraj, Mateo Calderon, Sebastian Ramon Herrera, Weihua Gao, Sean Ruland and Ben Zion Roitberg
Patients with subarachnoid hemorrhage treated using external ventricular drainage due to obstructive hydrocephalus commonly remain shunt-dependent. Based on identified risk factors for external ventricular drain (EVD) challenge failure, the authors sought to determine the likelihood that a patient will require a permanent shunt.
The authors reviewed 89 consecutive cases of aneurysmal subarachnoid hemorrhage with obstructive hydrocephalus for parameters associated with EVD challenge failure and permanent shunt requirement. Significant parameters were combined in a discriminant function analysis to create a failure risk index (FRI). Linear regression analysis was performed correlating the FRI with the actual rate of shunt dependency.
Patients requiring a permanent shunt had: a larger third ventricular diameter (7.0 vs 5.4 mm; p = 0.02) and a higher Hunt and Hess grade (3 vs 2; p = 0.02) at the time of admission; and a larger third ventricular diameter (6.6 vs 5.2 mm; p = 0.04), a larger bicaudate diameter (31.9 vs 30.2 mm; p = 0.03), and higher CSF protein levels (76.5 vs 40.3 mg/dl; p < 0.0001) at the onset of EVD challenge. These patients were also more likely to be female (p = 0.01) and have a posterior circulation location of their aneurysm (p = 0.01). The FRI score was calculated based on a weighted combination of the above parameters. Linear regression analysis between FRI values and the percentage of patients who required a permanent shunt had a correlation coefficient of 91%; the risk of a permanent shunt requirement increased linearly with a rising FRI score.
An FRI score created by discriminant function analysis can predict whether or not a permanent shunt is required, even if separate factors are not in agreement with each other or show a weak correlation when considered separately. An increased FRI score was strongly and linearly correlated with the risk of EVD challenge failure. A prospective study is necessary to validate the FRI.
Ali Alaraj, Troy Munson, Sebastian R. Herrera, Victor Aletich, Fady T. Charbel and Sepideh Amin-Hanjani
Cerebrospinal fluid hypotension, or “brain sag,” is a recently described phenomenon most commonly seen following craniotomy for the clipping of ruptured aneurysms along with preoperative lumbar drain placement. The clinical features and CT findings have been previously described. Clinical presentation can be similar to and often mistaken for cerebral vasospasm. In this study, the authors report on the angiographic findings in patients with brain sag.
Five cases of brain sag were diagnosed (range 1–4 days) after the surgical treatment of ruptured aneurysms at the University of Illinois at Chicago. All patients met the clinical and CT criteria for brain sag. Admission cerebral angiograms and subsequent angiograms during symptoms of brain sag were obtained in all patients. In 3 patients, angiography was performed after the resolution of symptoms.
In all 5 patients, the level of the basilar artery apex was displaced inferiorly with respect to the posterior clinoid processes during brain sag. This displacement was significant enough to create a noticeable kink in the basilar artery (“cobra sign”) in 3 patients. Other angiographic findings included foreshortening or kinking of the intracranial vertebral artery. In all patients, the posterior cerebral arteries were displaced medially and inferiorly. Three patients were treated for simultaneous severe radiological vasospasm. In 4 patients, the brain sag was recognized, and the patients' conditions improved when they were placed flat or in the Trendelenburg position, at times combined with an epidural blood patch. Patients with follow-up angiography studies after the symptoms had resolved displayed a reversal of the angiographic features.
Brain sag appears to be associated with characteristic angiographic features. Recognizing these features may help to diagnose brain sag as the cause of neurological deterioration in this patient population.
Daniel M. Birk, Matthew K. Tobin, Heather E. Moss, Eric Feinstein, Fady T. Charbel and Ali Alaraj
The most commonly described indications for surgical management of closed depressed skull fractures are hematoma evacuation and repair of extensive cosmetic deformity. Venous sinus injury, which occurs in a subset of depressed skull fractures, is not typically listed as an indication for surgical treatment due to the potential for major venous hemorrhage associated with surgery near these structures. However, if patients exhibit signs and symptoms of intracranial hypertension and radiographic findings demonstrate sinus compromise, surgical elevation of the depressed skull fragments is indicated. The authors present the case of a 25-year-old woman with a depressed skull fracture secondary to a gunshot wound with symptomatic compromise in venous outflow of the posterior one-third of the superior sagittal sinus. The patient was treated with surgical decompression via bilateral craniectomy along with intracranial pressure–lowering medical therapy and had almost full resolution of her presenting symptoms with documented improvement in flow through the superior sagittal sinus. While the use of surgical treatment for these types of injuries is highly debated, the authors demonstrate here that safe, effective surgical management of these patients is possible and that surgical decompression should always be considered in the case of symptomatic venous sinus flow obstruction.
Omar M. Qahwash, Ali Alaraj, Victor Aletich, Fady T. Charbel and Sepideh Amin-Hanjani
The goal of this study was to demonstrate feasibility and evaluate technical aspects of early endovascular access through extracranial-intracranial (EC-IC) bypass grafts.
Patients undergoing endovascular interventions through the graft in the acute postoperative period following EC-IC bypass are presented. Results, complications, and technical nuances are reviewed.
Fourteen endovascular procedures were performed in 5 patients after EC-IC bypass for ruptured aneurysms in 4 patients and posterior circulation ischemia in 1 patient. In 2 patients, a saphenous vein graft (SVG) was used to bypass the common carotid artery (CCA) to the middle cerebral artery (MCA). One patient underwent a superficial temporal artery (STA)–MCA bypass, and in 2 other patients the STA stump was connected to the intracranial circulation via an interposition SVG. The interval from surgery to endovascular intervention spanned 2–18 days; the indication was intracranial vasospasm in all patients. One case involved angioplasty of the proximal anastomosis on postoperative Day 14. All other interventions entailed proximal access through the bypass conduit for intraarterial infusion of vasodilators. Significant vasospasm of the STA itself was encountered in 2 patients during endovascular manipulation, and it was treated with intraarterial nitroglycerin. There were no cases of anastomotic disruption.
Endovascular catheterization and intervention involving a recent EC-IC bypass is feasible. The main limitation in this series was catheter-induced vasospasm involving the STA. A vein graft may be the more appropriate option in patients with subarachnoid hemorrhage who may require subsequent endovascular intervention for vasospasm.
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.
Alexander Ivanov, Andreas Linninger, Chih-Yang Hsu, Sepideh Amin-Hanjani, Victor A. Aletich, Fady T. Charbel and Ali Alaraj
The use of digital subtraction angiography (DSA) for semiquantitative cerebral blood flow(CBF) assessment is a new technique. The aim of this study was to determine whether patients with aneurysmal subarachnoid hemorrhage (aSAH) with higher Hunt and Hess grades also had higher angiographic contrast transit times (TTs) than patients with lower grades.
A cohort of 30 patients with aSAH and 10 patients without aSAH was included. Relevant clinical information was collected. A method to measure DSA TTs by color-coding reconstructions from DSA contrast-intensity images was applied. Regions of interest (ROIs) were chosen over major cerebral vessels. The estimated TTs included time-to-peak from 0% to 100% (TTP0–100), TTP from 25% to 100% (TTP25–100), and TT from 100% to 10% (TT100–10) contrast intensities. Statistical analysis was used to compare TTs between Group A (Hunt and Hess Grade I-II), Group B (Hunt and Hess Grade III-IV), and the control group. The correlation coefficient was calculated between different ROIs in aSAH groups.
There was no difference in demographic factors between Group A (n = 10), Group B (n = 20), and the control group (n = 10). There was a strong correlation in all TTs between ROIs in the middle cerebral artery (M1, M2) and anterior cerebral artery (A1, A2). There was a statistically significant difference between Groups A and B in all TT parameters for ROIs. TT100–10 values in the control group were significantly lower than the values in Group B.
The DSA TTs showed significant correlation with Hunt and Hess grades. TT delays appear to be independent of increased intracranial pressure and may be an indicator of decreased CBF in patients with a higher Hunt and Hess grade. This method may serve as an indirect technique to assess relative CBF in the angiography suite.
Sophia F. Shakur, Ali Alaraj, Nasya Mendoza-Elias, Muhammad Osama and Fady T. Charbel
The pathogenesis of cerebral aneurysms in patients with internal carotid artery (ICA) occlusion is hypothesized to be hemodynamic. For the first time, the authors quantify the hemodynamic characteristics associated with aneurysm formation in patients with ICA occlusion.
Records of patients with unilateral ICA stenosis or occlusion ≥ 90% who underwent hemodynamic assessment before treatment using quantitative MR angiography were retrospectively reviewed. The patients were classified into 2 groups based on the presence or absence of aneurysms. The hemodynamic parameters of flow volume rate, flow velocity, and wall shear stress (WSS) were measured in each vessel supplying collateral flow—bilateral A1 segments and bilateral posterior communicating arteries—and then compared between the groups.
A total of 36 patients were included (8 with and 28 without aneurysms). The mean flow (72.3 vs 48.9 ml/min, p = 0.10), flow velocity (21.1 vs 12.7 cm/sec, p = 0.006), and WSS (22.0 vs 12.3 dynes/cm2, p = 0.003) were higher in the A1 segment contralateral to the side of the patent ICA in patients with versus without aneurysms. All de novo or growing aneurysms in our cohort were located on the anterior communicating artery (ACoA) or P1 segment.
Flow velocity and WSS are significantly higher across the ACoA in patients who harbor an aneurysm, and de novo or growing aneurysms are often located on collateral vessels. Thus, robust primary collaterals after ICA occlusion may be a contributing factor in cerebral aneurysm formation.