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Zhi-Hong Zheng, Yi Lin, Pin-Shuo Su, Peng-Wei Wang, Wei-Ting Tsai and Dueng-Yuan Hueng

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Stephen J. Monteith, Asterios Tsimpas, Aaron S. Dumont, Stavropoula Tjoumakaris, L. Fernando Gonzalez, Robert H. Rosenwasser and Pascal Jabbour

Object

Despite advances in surgical and endovascular techniques, fusiform aneurysms remain a therapeutic challenge. Introduction of flow-diverting stents has revolutionized the treatment of aneurysms with wide necks and of complex morphology. The authors report their experience with the endovascular treatment of fusiform aneurysms using the Pipeline Embolization Device.

Methods

A retrospective review of 146 patients with cerebral aneurysms treated with the Pipeline Embolization Device between June 2011 and January 2013 was performed. Twenty-four patients were identified as having fusiform aneurysms. Twenty-four aneurysms in these 24 patients were treated. The mean patient age was 59 years. There were 9 men and 15 women. Angiographic and clinical data (including the modified Rankin Scale [mRS] score) were recorded at the time of treatment and at follow-up. The aneurysms were located in the internal carotid artery in 8 patients (33.3%), middle cerebral artery in 8 patients (33.3%), anterior cerebral artery in 1 patient (4%), and vertebrobasilar circulation in 7 patients (29%). The aneurysms were smaller than 10 mm in 3 patients, 10–25 mm in 16 patients, and larger than 25 mm in 5 patients. The mean largest dimension diameter was 18 mm.

Results

Stent deployment was successful in all cases. The minor procedural morbidity was 4% (1 case). Morbidity and mortality related to aneurysm treatment were 4.2% and 4.2%, respectively. The mean mRS scores preoperatively and at clinical follow-up (median 6.0 months, mean 6.9 months) were 0.71 and 1.2, respectively (91.7% presented with an mRS score of 2 or better, and 79.2% had an mRS score of 2 or better at the 6.0-month follow-up). At clinical follow-up, 82.6% of patients were stable or had improved, 13.0% worsened, and 4.2% had died. Twenty-two (91.7%) of 24 patients had follow-up angiography available (mean follow-up time 6.3 months); 59% had excellent angiographic results (> 95% or complete occlusion), 31.8% had complete aneurysm occlusion, 27.3% had greater than 95% aneurysm occlusion, 18.2% had a moderate decrease in size (50%–95%), 4.5% had a minimal decrease in size (< 50%), 13.6% had not changed, and 4.5% had an increase in size.

Conclusions

This series demonstrates that endovascular treatment of fusiform cerebral aneurysms with flow diversion was a safe and effective treatment. Procedural complications were low. Long-term morbidity and mortality rates were acceptable given the complex nature of these lesions.

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Edward H. Oldfield, Johanna J. Loomba, Stephen J. Monteith, R. Webster Crowley, Ricky Medel, Daryl R. Gress, Neal F. Kassell, Aaron S. Dumont and Craig Sherman

Object

Intravenous sodium nitrite has been shown to prevent and reverse cerebral vasospasm in a primate model of subarachnoid hemorrhage (SAH). The present Phase IIA dose-escalation study of sodium nitrite was conducted to determine the compound's safety in humans with aneurysmal SAH and to establish its pharmacokinetics during a 14-day infusion.

Methods

In 18 patients (3 cohorts of 6 patients each) with SAH from a ruptured cerebral aneurysm, nitrite (3 patients) or saline (3 patients) was infused. Sodium nitrite and saline were delivered intravenously for 14 days, and a dose-escalation scheme was used for the nitrite, with a maximum dose of 64 nmol/kg/min. Sodium nitrite blood levels were frequently sampled and measured using mass spectroscopy, and blood methemoglobin levels were continuously monitored using a pulse oximeter.

Results

In the 14-day infusions in critically ill patients with SAH, there was no toxicity or systemic hypotension, and blood methemoglobin levels remained at 3.3% or less in all patients. Nitrite levels increased rapidly during intravenous infusion and reached steady-state levels by 12 hours after the start of infusion on Day 1. The nitrite plasma half-life was less than 1 hour across all dose levels evaluated after stopping nitrite infusions on Day 14.

Conclusions

Previous preclinical investigations of sodium nitrite for the prevention and reversal of vasospasm in a primate model of SAH were effective using doses similar to the highest dose examined in the current study (64 nmol/kg/min). Results of the current study suggest that safe and potentially therapeutic levels of nitrite can be achieved and sustained in critically ill patients after SAH from a ruptured cerebral aneurysm. Clinical trial registration no.: NCT00873015 (ClinicalTrials.gov).

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Stephen J. Monteith, Sagi Harnof, Ricky Medel, Britney Popp, Max Wintermark, M. Beatriz S. Lopes, Neal F. Kassell, W. Jeff Elias, John Snell, Matthew Eames, Eyal Zadicario, Krisztina Moldovan and Jason Sheehan

Object

Intracerebral hemorrhage (ICH) is a major cause of death and disability throughout the world. Surgical techniques are limited by their invasive nature and the associated disability caused during clot removal. Preliminary data have shown promise for the feasibility of transcranial MR-guided focused ultrasound (MRgFUS) sonothrombolysis in liquefying the clotted blood in ICH and thereby facilitating minimally invasive evacuation of the clot via a twist-drill craniostomy and aspiration tube.

Methods and Results

In an in vitro model, the following optimum transcranial sonothrombolysis parameters were determined: transducer center frequency 230 kHz, power 3950 W, pulse repetition rate 1 kHz, duty cycle 10%, and sonication duration 30 seconds. Safety studies were performed in swine (n = 20). In a swine model of ICH, MRgFUS sonothrombolysis of 4 ml ICH was performed. Magnetic resonance imaging and histological examination demonstrated complete lysis of the ICH without additional brain injury, blood-brain barrier breakdown, or thermal necrosis due to sonothrombolysis. A novel cadaveric model of ICH was developed with 40-ml clots implanted into fresh cadaveric brains (n = 10). Intracerebral hemorrhages were successfully liquefied (> 95%) with transcranial MRgFUS in a highly accurate fashion, permitting minimally invasive aspiration of the lysate under MRI guidance.

Conclusions

The feasibility of transcranial MRgFUS sonothrombolysis was demonstrated in in vitro and cadaveric models of ICH. Initial in vivo safety data in a swine model of ICH suggest the process to be safe. Minimally invasive treatment of ICH with MRgFUS warrants evaluation in the setting of a clinical trial.

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Oded Goren, Stephen J. Monteith, Moshe Hadani, Mati Bakon and Sagi Harnof

This paper reviews the current intraoperative imaging tools that are available to assist neurosurgeons in the treatment of intracerebral hemorrhage (ICH). This review shares the authors' experience with each modality and discusses the advantages, potential limitations, and disadvantages of each.

Surgery for ICH is directed at blood clot removal, reduction of intracranial pressure, and minimization of secondary damage associated with hematoma breakdown products. For effective occlusion and safe obliteration of vascular anomalies associated with ICH, vascular neurosurgeons today require a thorough understanding of the various intraoperative imaging modalities available for obtaining real-time information. Use of one or more of these modalities may improve the surgeon's confidence during the procedure, the patient's safety during surgery, and surgical outcome.

The modern techniques discussed include 1) indocyanine green–based video angiography, which provides real-time information based on high-quality images showing the residual filling of vascular pathological entities and the patency of blood vessels of any size in the surgical field; and 2) intraoperative angiography, which remains the gold standard intraoperative diagnostic test in the surgical management of cerebral aneurysms and arteriovenous malformations. Hybrid procedures, providing multimodality image-guided surgeries and combining endovascular with microsurgical strategies within the same surgical session, have become feasible and safe. Microdoppler is a safe, noninvasive, and reliable technique for evaluation of hemodynamics of vessels in the surgical field, with the advantage of ease of use. Intraoperative MRI provides an effective navigation tool for cavernoma surgery, in addition to assessing the extent of resection during the procedure. Intraoperative CT scanning has the advantage of very high sensitivity to acute bleeding, thereby assisting in the confirmation of the extent of hematoma evacuation and the extent of vascular anomaly resection. Intraoperative ultrasound aids navigation and evacuation assessment during intracerebral hematoma evacuation surgeries. It supports the concept of minimally invasive surgery and has undergone extensive development in recent years, with the quality of ultrasound imaging having improved considerably.

Image-guided therapy, combined with modern intraoperative imaging modalities, has changed the fundamentals of conventional vascular neurosurgery by presenting real-time visualization of both normal tissue and pathological entities. These imaging techniques are important adjuncts to the surgeon's standard surgical armamentarium. Familiarity with these imaging modalities may help the surgeon complete procedures with improved safety, efficiency, and clinical outcome.

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Stephen J. Monteith, Neal F. Kassell, Oded Goren and Sagi Harnof

Intracerebral hemorrhage remains a significant cause of morbidity and mortality. Current surgical therapies aim to use a minimally invasive approach to remove as much of the clot as possible without causing undue disruption to surrounding neural structures. Transcranial MR-guided focused ultrasound (MRgFUS) surgery is an emerging technology that permits a highly concentrated focal point of ultrasound energy to be deposited to a target deep within the brain without an incision or craniotomy. With appropriate ultrasound parameters it has been shown that MRgFUS can effectively liquefy large-volume blood clots through the human calvaria. In this review the authors discuss the rationale for using MRgFUS to noninvasively liquefy intracerebral hemorrhage (ICH), thereby permitting minimally invasive aspiration of the liquefied clot via a small drainage tube. The mechanism of action of MRgFUS sonothrombolysis; current investigational work with in vitro, in vivo, and cadaveric models of ICH; and the potential clinical application of this disruptive technology for the treatment of ICH are discussed.

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Stephen J. Monteith, Ricky Medel, Neal F. Kassell, Max Wintermark, Matthew Eames, John Snell, Eyal Zadicario, Javier Grinfeld, Jason P. Sheehan and W. Jeff Elias

Object

Transcranial MR-guided focused ultrasound surgery (MRgFUS) is evolving as a treatment modality in neurosurgery. Until now, the trigeminal nerve was believed to be beyond the treatment envelope of existing high-frequency transcranial MRgFUS systems. In this study, the authors explore the feasibility of targeting the trigeminal nerve in a cadaveric model with temperature assessments using computer simulations and an in vitro skull phantom model fitted with thermocouples.

Methods

Six trigeminal nerves from 4 unpreserved cadavers were targeted in the first experiment. Preprocedural CT scanning of the head was performed to allow for a skull correction algorithm. Three-Tesla, volumetric, FIESTA MRI sequences were performed to delineate the trigeminal nerve and any vascular structures of the cisternal segment. The cadaver was positioned in a focused ultrasound transducer (650-kHz system, ExAblate Neuro, InSightec) so that the focus of the transducer was centered at the proximal trigeminal nerve, allowing for targeting of the root entry zone (REZ) and the cisternal segment. Real-time, 2D thermometry was performed during the 10- to 30-second sonication procedures. Post hoc MR thermometry was performed on a computer workstation at the conclusion of the procedure to analyze temperature effects at neuroanatomical areas of interest. Finally, the region of the trigeminal nerve was targeted in a gel phantom encased within a human cranium, and temperature changes in regions of interest in the skull base were measured using thermocouples.

Results

The trigeminal nerves were clearly identified in all cadavers for accurate targeting. Sequential sonications of 25–1500 W for 10–30 seconds were successfully performed along the length of the trigeminal nerve starting at the REZ. Real-time MR thermometry confirmed the temperature increase as a narrow focus of heating by a mean of 10°C. Postprocedural thermometry calculations and thermocouple experiments in a phantom skull were performed and confirmed minimal heating of adjacent structures including the skull base, cranial nerves, and cerebral vessels. For targeting, inclusion of no-pass regions through the petrous bone decreased collateral heating in the internal acoustic canal from 16.7°C without blocking to 5.7°C with blocking. Temperature at the REZ target decreased by 3.7°C with blocking. Similarly, for midcisternal targeting, collateral heating at the internal acoustic canal was improved from a 16.3°C increase to a 4.9°C increase. Blocking decreased the target temperature increase by 4.4°C for the same power settings.

Conclusions

This study demonstrates focal heating of up to 18°C in a cadaveric trigeminal nerve at the REZ and along the cisternal segment with transcranial MRgFUS. Significant heating of the skull base and surrounding neural structures did not occur with implementation of no-pass regions. However, in vivo studies are necessary to confirm the safety and efficacy of this potentially new, noninvasive treatment.

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Stephen J. Monteith, Robert M. Starke, John A. Jane Jr. and Edward H. Oldfield

Object

Subnormal postoperative serum cortisol levels indicate successful surgery and predict long-term remission of Cushing disease. Given the short serum half-lives of adrenocorticotropic hormone (ACTH) and cortisol, it is unclear why the decline in cortisol postoperatively is delayed for 18–36 hours. Furthermore, the relevance of the rate of cortisol drop immediately after surgery has not been investigated.

Methods

Patient data were analyzed from a prospectively accrued database. After surgery, cortisol replacement was withheld and serum cortisol measurements were obtained every 6 hours until values of 1.0–2.0 μg/dl or less were reached. The authors selected patients in whom serum cortisol dropped to 2 μg/dl or less after surgery (101 patients). Tumor resection was categorized as follows: 1) complete resection using the histological pseudocapsule as a surgical capsule, 2) complete piecemeal resection), 3) known incomplete resection, and 4) total hypophysectomy.

Results

The median time to reach a cortisol level of less than or equal to 2.0 μg/dl was 9.9, 19.4, 25.3, and 29.5 hours with hypophysectomy, pseudocapsule, incomplete resection, and piecemeal techniques, respectively. Pseudocapsule resection produced a faster decline in cortisol than piecemeal techniques (p = 0.0001), but not as rapid a decline as hypophysectomy (p = 0.033).

Conclusions

Complete resection by other techniques is associated with delayed cortisol decline compared with pseudocapsule surgery, which may represent the product of residual tumor cells and therefore may explain the higher rate of recurrent disease associated with piecemeal techniques. The prompt drop in cortisol after hypophysectomy compared with patients with pseudocapsule surgery suggests that the corticotrophs of the normal gland can secrete ACTH for 10–36 hours after surgery despite prolonged and severe hypercortisolism.

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Editorial

Arteriovenous malformations

Douglas Kondziolka

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Chun Po Yen, Stephen J. Monteith, James H. Nguyen, Jessica Rainey, David J. Schlesinger and Jason P. Sheehan

Object

The aim of this study was to evaluate the long-term imaging and clinical outcomes of intracranial arteriovenous malformations (AVMs) in children treated with Gamma Knife surgery (GKS).

Methods

Between 1989 and 2007, 200 patients with AVMs who were 18 years of age or younger were treated at the University of Virginia Health System. Excluding 14 patients who had not reached 2-year follow-up, 186 patients comprised this study. Hemorrhage was the most common presenting symptom leading to the diagnosis of AVMs (71.5%). The mean nidus volume was 3.2 cm3 at the time of GKS, and a mean prescription dose of 21.9 Gy was used.

Results

After initial GKS, 49.5% of patients achieved total angiographic obliteration. Forty-one patients whose AVM nidi remained patent underwent additional GKS. The obliteration rate increased to 58.6% after a second or multiple GKS. Subtotal obliteration was achieved in 9 patients (4.8%). Forty-nine patients (26.3%) still had a patent residual nidus. In 19 patients (10.2%), obliteration was confirmed on MR imaging only. Ten patients had 17 hemorrhages during the follow-up period. The hemorrhage rate was 5.4% within 2 years after GKS and 0.8% between 2 and 5 years. Six patients developed neurological deficits along with the radiation-induced changes. Two patients developed asymptomatic meningiomas 10 and 12 years after GKS. After a mean clinical follow-up of 98 months, less than 4% of patients had difficulty attending school or developing a career.

Conclusions

Gamma Knife surgery offers a reasonable chance of obliteration of an AVM in pediatric patients. The incidence of symptomatic radiation-induced changes is relatively low; however, long-term clinical and imaging follow-up is required to identify delayed cyst formation and secondary tumors.