Publications by authors named "Chandan Krishna"

45 Publications

Microvascular Decompression Technique for Trigeminal Neuralgia Using a Vascular Clip.

World Neurosurg 2021 Jul 6;154. Epub 2021 Jul 6.

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona, USA; Department of Otolaryngology, Mayo Clinic, Phoenix, Arizona, USA; Department of Radiology, Mayo Clinic, Phoenix, Arizona, USA; Precision Neuro-therapeutics Innovation Lab, Mayo Clinic, Phoenix, Arizona, USA; Neurosurgery Simulation and Innovation Lab, Mayo Clinic, Phoenix, Arizona. Electronic address:

Microvascular decompression (MVD) surgery is a well-established, effective treatment option for trigeminal neuralgia and hemifacial spasm. In 1967, Janetta et al introduced the concept of MVD surgery and pioneered the Janetta technique in which Teflon felt implants are placed between the trigeminal nerve and offending vessel. Though many cases are successfully managed with Teflon interposition, alternative techniques have been developed with the objective to alleviate vascular compression symptoms indefinitely, including transposition using biological glue, vascular clips, and a variety of "sling" techniques. In Video 1, we demonstrate a fenestrated clip transposition technique in the treatment of trigeminal neuralgia. We present the case of a 72-year-old female who presented with classic trigeminal neuralgia pain along the V2 and V3 distributions. Magnetic resonance imaging revealed evident compression of the trigeminal nerve by the superior cerebellar artery (SCA). A retrosigmoid craniotomy was performed, and the vascular loop of the SCA was visualized compressing the root entry zone with significant indentation of the trigeminal nerve. Wide arachnoid dissection along the SCA was carried out in order to mobilize the SCA away from the nerve. A small slit was created in the undersurface of the tentorium, and then the SCA loop was transposed to the tentorium using a fenestrated aneurysm clip. The postoperative course was uneventful, and the patient had complete resolution of her facial pain at 6-month follow-up. This method is likely an effective and durable method of decompression for trigeminal neuralgia.
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http://dx.doi.org/10.1016/j.wneu.2021.06.124DOI Listing
July 2021

Uncertainty quantification in the radiogenomics modeling of EGFR amplification in glioblastoma.

Sci Rep 2021 Feb 16;11(1):3932. Epub 2021 Feb 16.

Department of Radiology, Mayo Clinic Arizona, 5777 E. Mayo Blvd, Phoenix, AZ, 85054, USA.

Radiogenomics uses machine-learning (ML) to directly connect the morphologic and physiological appearance of tumors on clinical imaging with underlying genomic features. Despite extensive growth in the area of radiogenomics across many cancers, and its potential role in advancing clinical decision making, no published studies have directly addressed uncertainty in these model predictions. We developed a radiogenomics ML model to quantify uncertainty using transductive Gaussian Processes (GP) and a unique dataset of 95 image-localized biopsies with spatially matched MRI from 25 untreated Glioblastoma (GBM) patients. The model generated predictions for regional EGFR amplification status (a common and important target in GBM) to resolve the intratumoral genetic heterogeneity across each individual tumor-a key factor for future personalized therapeutic paradigms. The model used probability distributions for each sample prediction to quantify uncertainty, and used transductive learning to reduce the overall uncertainty. We compared predictive accuracy and uncertainty of the transductive learning GP model against a standard GP model using leave-one-patient-out cross validation. Additionally, we used a separate dataset containing 24 image-localized biopsies from 7 high-grade glioma patients to validate the model. Predictive uncertainty informed the likelihood of achieving an accurate sample prediction. When stratifying predictions based on uncertainty, we observed substantially higher performance in the group cohort (75% accuracy, n = 95) and amongst sample predictions with the lowest uncertainty (83% accuracy, n = 72) compared to predictions with higher uncertainty (48% accuracy, n = 23), due largely to data interpolation (rather than extrapolation). On the separate validation set, our model achieved 78% accuracy amongst the sample predictions with lowest uncertainty. We present a novel approach to quantify radiogenomics uncertainty to enhance model performance and clinical interpretability. This should help integrate more reliable radiogenomics models for improved medical decision-making.
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http://dx.doi.org/10.1038/s41598-021-83141-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7886858PMC
February 2021

Initiation of a Robotic Program in Spinal Surgery: Experience at a Three-Site Medical Center.

Mayo Clin Proc 2021 05 28;96(5):1193-1202. Epub 2020 Dec 28.

Department of Neurologic Surgery, Mayo Clinic, Rochester, MN.

Objective: To highlight the early experience of implementing a robotic spine surgery program at a three-site medical center, evaluating the impact of increasing experience on the operative time and number of procedures performed.

Patients And Methods: A retrospective chart review of patients undergoing robotic screw placement between September 4, 2018, and October 16, 2019, was conducted. Baseline characteristics as well as intraoperative and post-operative outcomes were obtained.

Results: For a total of 77 patients, the mean age (SD) was 55.7 years (11.5) and 49.4% (n=38) were female. A total of 402 screws were placed (384 pedicle screws, 18 cortical screws) using robotic guidance with a median of two operative levels (interquartile range [IQR], 1 to 2). Median (IQR) estimated blood loss was 100 mL (50 to 200 mL) and the median (IQR) operative time was 224 minutes (193 to 307 minutes). With accrual of surgical experience, operative time declined significantly (R=-0.39; P<.001) whereas the number of procedures performed per week increased (R=0.30; P=.05) throughout the study period. Median (IQR) length of hospital stay following surgery was 2 days (IQR, 2 to 3 days). There were two screws requiring revision intraoperatively. No postoperative revisions were required, and no complications were encountered related to screw placement.

Conclusion: Early experience at our institution using a spinal robot has demonstrated no requirement for postoperative screw revisions and no complications related to screw malposition. The increased operative times were reduced as the frequency of procedures increased. Moreover, procedural times diminished over a short period with a weekly increasing number of procedures.
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http://dx.doi.org/10.1016/j.mayocp.2020.07.034DOI Listing
May 2021

Quality of Life of Patients with Unruptured Intracranial Aneurysms Before and After Endovascular Coiling: A HEAT Trial Secondary Study and Systematic Review of the Literature.

World Neurosurg 2021 02 27;146:e492-e500. Epub 2020 Oct 27.

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona, USA; Department of Otolaryngology, Mayo Clinic, Phoenix, Arizona, USA; Department of Radiology, Mayo Clinic, Phoenix, Arizona, USA; Precision Neuro-therapeutics Innovation Lab, Mayo Clinic, Phoenix, Arizona, USA; Neurosurgery Simulation and Innovation Lab, Mayo Clinic, Phoenix, Arizona, USA. Electronic address:

Background: The study of quality of life (QOL) in patients with asymptomatic diseases receiving interventional treatment provides an essential metric for the assessment of procedural benefits in the surgical patient population. In this study, we analyzed QOL data collected from patients with unruptured intracranial aneurysms (UIAs) before and after endovascular coiling in the HEAT Trial, alongside a systematic review on QOL in unruptured brain aneurysms.

Methods: HEAT was a randomized controlled trial comparing recurrence rates in aneurysms treated with either bare platinum coils or hydrogel coils. Patients enrolled in this trial completed a short form-36 (SF-36) QOL questionnaire before treatment and at the 3- to 12- and 18- to 24-month follow-ups. The change in QOL before and after treatment was assessed. Regression analysis evaluated the effect of select baseline characteristics on QOL change.

Results: A total of 270 patients were eligible for analysis. There was an increase in the role physical (P = 0.043), vitality (P = 0.022), and emotional well-being (P < 0.001) QOL components at the 18- to 24-month follow-up compared with baseline scores. Regression analysis showed that age younger than 60 and absence of serious adverse events were associated with improved social functioning and vitality. The literature review showed a mixed effect of intervention on QOL in patients with UIAs.

Conclusions: Our analysis has revealed that patients with 3- to 14-mm UIAs had improvements in some physical and emotional components of QOL at 18-24 months following aneurysm coiling in the HEAT study. The literature remains indeterminate on this issue. Further studies are needed to better understand the effects of the diagnosis of UIAs and their treatment on QOL.
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http://dx.doi.org/10.1016/j.wneu.2020.10.120DOI Listing
February 2021

Troubleshooting an unusual complication following intrathecal chemotherapy delivered via Ommaya catheter: A case report.

Mol Clin Oncol 2020 Jul 22;13(1):76-79. Epub 2020 Apr 22.

Department of Neurology, Mayo Clinic, Phoenix, AZ 85054, USA.

The authors report the case of a 39-year-old woman with leukemic meningitis. A right frontal Ommaya reservoir was placed for intrathecal chemotherapy. During and immediately following the first injection of chemotherapy, the patient developed an episode of nausea, emesis, frontal headache and diarrhea. These same symptoms were later elicited during a second and third administration of chemotherapy. Post-placement head computed tomography showed the tip of the catheter projecting approximately 1.5 cm inferior to the floor of the left frontal ventricle. After a revision of the Ommaya catheter due to suboptimal positioning, subsequent intrathecal chemotherapy administration was tolerated without any of the adverse symptoms previously encountered. The case documents an unusual complication arising from catheter migration in the setting of intrathecal chemotherapy and also demonstrates the value in troubleshooting Ommaya reservoir complications rather than prematurely abandoning its use in favor of lumbar puncture.
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http://dx.doi.org/10.3892/mco.2020.2032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7241235PMC
July 2020

Metal Hypersensitivity After Spinal Instrumentation: When to Suspect and How to Treat.

World Neurosurg 2020 07 24;139:471-477. Epub 2020 Apr 24.

Department of Neurosurgery, Mayo Clinic, Scottsdale, Arizona, USA.

Background: Metal hypersensitivity is a rare complication after spinal implant placement but is related to significant clinical challenges including implant failure and poor wound healing. The incidence is likely underreported secondary to challenges with diagnosis and retreatment options.

Case Description: We present the case of a 41-year-old woman with metal hypersensitivity 6 years status post anterior lumbar interbody fusion after a previously failed revision procedure who presented with low back pain and abdominal pain with food intolerance. Diagnostics revealed presacral fluid collection, which was negative for infection. A detailed workup ruled out other possible differential diagnoses and confirmed hypersensitivity to nickel. Intraoperatively, the interbody was loose but difficult to remove secondary to scar tissue. Ultimately, it was successfully replaced with a polyetheretherketone interbody, which did not contain nickel.

Conclusions: Metal hypersensitivity is likely an underreported complication in spine literature that is associated with poor outcomes. Further research to create evidence-based guidelines on diagnosis and retreatment options will facilitate diagnosis, reduce time to revision surgery, and ultimately decrease patient suffering.
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http://dx.doi.org/10.1016/j.wneu.2020.04.093DOI Listing
July 2020

Extended Lateral Orbital Craniotomy: Anatomic Study and Initial Clinical Series of a Novel Minimally Invasive Pterional Approach.

J Neurol Surg B Skull Base 2020 Feb 21;81(1):88-96. Epub 2019 Feb 21.

Department of Neurological Surgery, Mayo Clinic Arizona, Phoenix, Arizona, United States.

 Of the minimally invasive "keyhole" alternatives to the pterional region, the supraorbital eyebrow approach is the most widely adopted. Yet it can prove disadvantageous when a more direct lateral microsurgical trajectory of attack to the Sylvian fissure and anterior middle fossa are needed.  The extended lateral orbital (XLO) approach was designed to be direct and minimally invasive, with the sphenoid ridge at the center of exposure.  Five injected cadaver heads were used for anatomic study of the XLO approach. The anatomic course of the frontalis branch of facial nerve was studied in relation to the XLO incision. Following XLO incision, the bone exposure was measured. The intracranial microsurgical exposure was assessed subjectively. Application of the technique in representative clinical operative cases is provided.  The frontalis nerve was protected in the subgaleal fat pad, with an average minimum distance of 2.3 cm from the XLO incision. The mean calvarial area exposure was 4.95 cm and consistently centered on the sphenoid ridge. Excellent access to ipsilateral Sylvian's fissure, perisylvian regions, and supra-/parasellar structures was possible. The main limitations related to exposure of the posterior Sylvian fissure and the expected limitations of microsurgical instrument manipulation from a smaller craniotomy.  The XLO approach is a minimally invasive keyhole approach to the pterional region that affords a unique lateral trajectory via a craniotomy centered on the sphenoid ridge. Excellent exposure to properly selected lesions is possible. The incision is at a safe distance from the frontalis branch and shows excellent cosmetic healing.
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http://dx.doi.org/10.1055/s-0038-1677470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6997024PMC
February 2020

Restoring Speech Using Neuroprosthetic Technology: A New Frontier for Patients with Aphasia.

World Neurosurg 2019 Dec 19;132:437-438. Epub 2019 Nov 19.

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona, USA; Department of Otolaryngology, Mayo Clinic, Phoenix, Arizona, USA; Department of Radiology, Mayo Clinic, Phoenix, Arizona, USA; Precision Neuro-therapeutics Innovation Lab, Mayo Clinic, Phoenix, Arizona, USA; Neurosurgery Simulation and Innovation Lab, Mayo Clinic, Phoenix, Arizona, USA.

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http://dx.doi.org/10.1016/j.wneu.2019.09.069DOI Listing
December 2019

Vascular Transposition of the Superior Cerebellar Artery Using a Fenestrated Clip and Fibrin Glue in Trigeminal Neuralgia: 2-Dimensional Operative Video.

Oper Neurosurg (Hagerstown) 2020 07;19(1):E50-E51

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona.

This is the case of an 86-yr-old gentleman who presented with left facial pain exacerbated by eating, drinking, chewing, and shaving (distribution: V2, V3). The patient was diagnosed with trigeminal neuralgia and was refractory to medications. Imaging showed a superior cerebellar artery (SCA) loop adjacent to the trigeminal nerve root entry zone and a decision to perform a microvascular decompression of the fifth nerve was presented to the patient. After patient informed consent was obtained, a standard 3 cm × 3 cm retrosigmoid craniotomy was performed with the patient in a supine head turned position and in reverse Trendelenburg. The arachnoid bands tethering the SCA to the trigeminal nerve were sharply divided. A slit was then made in the tentorium and a 3 mm fenestrated clip was then used to secure the transposed SCA away from the trigeminal nerve. The SCA proximal to this was slightly patulous in its course so a small amount of a fibrin glue was also used to secure the more proximal SCA to the tentorium. The patient was symptom-free postoperatively and no longer required medical therapy. Additionally, imaging was consistent with adequate separation of the nerve from adjacent vessels.1-5.
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http://dx.doi.org/10.1093/ons/opz291DOI Listing
July 2020

Tulip Giant Aneurysm Amputation and "Shingle Clip Cut Clip" Technique for Microsurgical Reconstruction of a Giant Thrombosed Middle Cerebral Artery Aneurysm.

World Neurosurg 2019 Nov 2;131:166. Epub 2019 Aug 2.

Department of Neurologic Surgery, University of Texas Southwestern Medical Center, Houston, Texas, USA.

In this video, we present the case of a 61-year-old female who was brought to the emergency department after she had partial complex seizures. Computed tomography and magnetic resonance imaging of the brain revealed a right temporal lobe mass, which was initially thought to be a tumor. The patient was therefore referred to us for further management. The round nature of the lesion raised suspicion for an aneurysm. Computed tomography angiography was performed, followed by a diagnostic conventional cerebral angiogram, and confirmed the presence of a giant thrombosed aneurysm. Giant aneurysms represent 3%-5% of all cerebral aneurysms. They are more common in females with a ratio of 2:1 to 3:1. They have a high risk of rupture up to 50% in the posterior circulation and 40% in the anterior circulation over 5 years according to the International Study of Unruptured Intracranial Aneurysms Investigators. Their treatment can be complex and treacherous. Treatment options vary widely from parent artery sacrifice in select cases to clip reconstruction to an array of endovascular approaches such as flow diversion. In some cases a combination of both open and endovascular approaches might be necessary. In our case, we opted for an open surgical clip reconstruction. A superior temporal artery-middle cerebral artery bypass was attempted to allow for trapping of the aneurysm without risking ischemic complication distal to it. Unfortunately, the patient's vessels were too atherosclerotic to maintain patency. A strategy was then devised, which consisted of cutting the dome of the aneurysm and clearing the distal two thirds of the clot ("tulip technique") and then completing thrombus resection under temporary occlusion. Once clot removal was completed, the aneurysm was clipped using the "shingle clip cut clip" technique (Video 1). The patient's postoperative course was uneventful, and the patient remained seizure free.
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http://dx.doi.org/10.1016/j.wneu.2019.07.192DOI Listing
November 2019

Letter: Management of a Previously Coiled Anterior Cerebral Artery Aneurysm in a Child: 3-Dimensional Operative Video.

Oper Neurosurg (Hagerstown) 2019 08;17(2):E93-E94

Department of Neurological Surgery Mayo Clinic Phoenix, Arizona.

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http://dx.doi.org/10.1093/ons/opz144DOI Listing
August 2019

Thrombectomy for a Patient with Concomitant Acute Cervical Internal Carotid and Middle Cerebral Artery Occlusion: Video Case.

Neurosurgery 2019 07;85(suppl_1):S74-S75

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona.

We present the case of a 62-yr-old female who presented with ground-level fall and new onset of left-sided weakness of 30 min duration. CT angiogram revealed right ICA pseudo-occlusion and thrombus filling the right proximal M1 segment of the right MCA. On detailed neurological exam patient was noted to have NIHSS of 25. Patient was started on IV TPA infusion and was taken to interventional angiography suite after an informed consent was obtained. Diagnostic angiography was performed which demonstrated critical stenosis of the right proximal internal carotid artery. Right carotid artery stenting and balloon angioplasty of the carotid stent with distal embolic protection device was performed. Post carotid stent angiogram once again confirmed proximal right M1 pseudo-occlusion in the right MCA distribution. The clot was removed using a stent retriever, thus achieving complete recanalization (TICI 3) of the right cerebral hemisphere. The patient returned to baseline neurological status and a 1 mo follow-up diagnostic angiogram revealed patent carotid stent. Following the case presentation, we present the nuances of acute ischemic stroke management of large vessel occlusion with an emphasis on technical nuances, recent published guidelines1 and the literature.2-8.
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http://dx.doi.org/10.1093/neuros/nyz084DOI Listing
July 2019

Diagnosis and Endovascular Embolization of a Sacral Spinal Arteriovenous Fistula with "Holo-Spinal" Venous Drainage.

World Neurosurg 2019 Aug 20;128:328-332. Epub 2019 May 20.

Department of Neurosurgery, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA; Department of Radiology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York, USA; Department of Neurosurgery, Gates Vascular Institute at Kaleida Health, Buffalo, New York, USA; Canon Stroke and Vascular Research Center, University at Buffalo, Buffalo, New York, USA. Electronic address:

Background: Spinal dural arteriovenous fistulas are the most common spinal vascular pathology, accounting for up to 70% of spinal vascular malformations. They most commonly present with insidious and progressive myelopathy and bowel, bladder, and sexual dysfunction. Although noninvasive imaging (e.g., magnetic resonance imaging, magnetic resonance angiography) may suggest the presence of a spinal arteriovenous fistula (AVF), the diagnosis requires confirmation with spinal angiography.

Case Description: A 65-year-old woman presented with progressive myelopathy. Traditional spinal angiography of the paired radicular arteries failed to demonstrate any vascular malformation. However, injection of the right internal iliac artery demonstrated an AVF arising from the artery of Desproges-Gotteron with retrograde venous drainage to the upper thoracic region.

Conclusions: Selective transarterial catheterization and embolization with n-butyl cyanoacrylate resulted in complete occlusion of the AVF. Clinical improvement was also noted on postprocedural day 1. This case highlights the importance of internal iliac injections as a critical component of spinal angiography during an evaluation for vascular malformation.
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http://dx.doi.org/10.1016/j.wneu.2019.05.099DOI Listing
August 2019

The Use of Recombinant Poliovirus for the Treatment of Recurrent Glioblastoma Multiforme.

World Neurosurg 2019 Jan 22. Epub 2019 Jan 22.

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona; Precision Neuro-therapeutics Innovation Lab, Mayo Clinic, Phoenix, AZ; Neurosurgery Stimulation and Innovation Lab, Mayo Clinic, Phoenix, AZ; Department of Otolaryngology, Mayo Clinic, Phoenix, AZ; Department of Radiology, Mayo Clinic, Phoenix, AZ.

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http://dx.doi.org/10.1016/j.wneu.2019.01.050DOI Listing
January 2019

Use of 4D Computer Tomographic Angiography to Accurately Identify Distal Internal Carotid Artery Occlusions and Pseudo-Occlusions: Technical Note.

J Vasc Interv Neurol 2018 Jun;10(1):39-44

Department of Neurosurgery, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY, USA.

Background And Purpose: Traditional methods of computed tomographic angiography (CTA) can be unreliable in detecting carotid artery pseudo-occlusions or in accurately locating the site of carotid artery occlusion. With these methods, lack of adequate distal runoff due to pseudo-occlusion or intracranial occlusion can result in the inaccurate diagnoses of complete occlusion or cervical carotid occlusion, respectively. The site of carotid occlusion has important therapeutic and interventional considerations. We present several cases in which 4D CTA was utilized to accurately and noninvasively diagnose carotid pseudo-occlusion and intracranial internal carotid artery (ICA) occlusion.

Methods: We identified five patients who presented to our institute with ischemic stroke symptoms and evaluated images from traditional CTA protocols and 4D CTA protocols in each of these patients, comparing diagnoses rendered by each imaging technique.

Results: In two patients, traditional CTA suggested the presence of complete ICA occlusion. However, 4D CTA demonstrated pseudo-occlusion. Similarly, in three patients, traditional CTA demonstrated cervical ICA occlusion, whereas the 4D CTA demonstrated intracranial ICA occlusion.

Conclusion: 4D CTA may be a more effective noninvasive imaging technique than traditional CTA to detect intracranial carotid artery occlusions and carotid artery pseudo-occlusions. Accurate, rapid, and noninvasive diagnosis of carotid artery lesions may help tailor and expedite endovascular intervention.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5999302PMC
June 2018

Microsurgical Resection of a Type 1 Spinal Dural Arteriovenous Fistula: A 3-Dimensional Operative Video.

Oper Neurosurg (Hagerstown) 2018 03;14(3):313

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona.

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http://dx.doi.org/10.1093/ons/opx115DOI Listing
March 2018

Assessment of the Interrater Reliability of the Congress of Neurological Surgeons Microanastomosis Assessment Scale.

Oper Neurosurg (Hagerstown) 2017 02;13(1):108-112

Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona.

Background: The potential for simulation-based learning in neurosurgical training has led the Congress of Neurosurgical Surgeons to develop a series of simulation modules. The Northwestern Objective Microanastomosis Assessment Tool (NOMAT) was created as the corresponding assessment tool for the Congress of Neurosurgical Surgeons Microanastomosis Module. The face and construct validity of the NOMAT have been previously established.

Objective: To further validate the NOMAT by determining its interrater reliability (IRR) between raters of varying levels of microsurgical expertise.

Methods: The NOMAT was used to assess residents' performance in a microanastomosis simulation module in 2 settings: Northwestern University and the Society of Neurological Surgeons 2014 Boot Camp at the University of Indiana. At Northwestern University, participants were scored by 2 experienced microsurgeons. At the University of Indiana, participants were scored by 2 postdoctoral fellows and an experienced microsurgeon. The IRR of NOMAT was estimated by computing the intraclass correlation coefficient using SPSS v22.0 (IBM, Armonk, New York).

Results: A total of 75 residents were assessed. At Northwestern University, 21 residents each performed microanastomosis on 2 model vessels of different sizes, one 3 mm and one 1 mm. At the University of Indiana, 54 residents performed a single microanastomosis procedure on 3-mm vessels. The intraclass correlation coefficient of the total NOMAT scores was 0.88 at Northwestern University and 0.78 at the University of Indiana.

Conclusion: This study indicates high IRR for the NOMAT. These results suggest that the use of raters with varying levels of expertise does not compromise the precision or validity of the scale. This allows for a wider adoption of the scale and, hence, a greater potential educational impact.
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http://dx.doi.org/10.1227/NEU.0000000000001403DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6312083PMC
February 2017

Hemicraniectomy for Ischemic and Hemorrhagic Stroke: Facts and Controversies.

Neurosurg Clin N Am 2017 Jul;28(3):349-360

Department of Neurological Surgery, Mayo Clinic Hospital, Mayo Clinic, 5777 East Mayo Boulevard, Phoenix, AZ 85054, USA; Precision Neuro-theraputics Innovation Lab, Mayo Clinic Hospital, Mayo Clinic, 5777 East Mayo Boulevard, Phoenix, AZ 85054, USA; Neurosurgery Simulation and Innovation Lab, Mayo Clinic Hospital, Mayo Clinic, 5777 East Mayo Boulevard, Phoenix, AZ 85054, USA; Department of Radiology, Mayo Clinic Hospital, Mayo Clinic, 5777 East Mayo Boulevard, Phoenix, AZ 85054, USA; Department of Otolaryngology, Mayo Clinic Hospital, Mayo Clinic, 5777 East Mayo Boulevard, Phoenix, AZ 85054, USA. Electronic address:

Malignant large artery stroke is associated with high mortality of 70% to 80% with best medical management. Decompressive craniectomy (DC) is a highly effective tool in reducing mortality. Convincing evidence has accumulated from several randomized trials, in addition to multiple retrospective studies, that demonstrate not only survival benefit but also improved functional outcome with DC in appropriately selected patients. This article explores in detail the evidence for DC, nuances regarding patient selection, and applicability of DC for supratentorial intracerebral hemorrhage and posterior fossa ischemic and hemorrhagic stroke.
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http://dx.doi.org/10.1016/j.nec.2017.02.010DOI Listing
July 2017

Awake Surgery for Brain Vascular Malformations and Moyamoya Disease.

World Neurosurg 2017 Sep 2;105:659-671. Epub 2017 Apr 2.

Department of Neurological Surgery, Neurovascular and Skullbase Program, Mayo Clinic, Phoenix, Arizona, USA; Department of Otolaryngology, Mayo Clinic, Phoenix, Arizona, USA; Department of Radiology, Mayo Clinic, Phoenix, Arizona, USA; Precision Neuro-therapeutics Innovation Lab, Mayo Clinic, Phoenix, Arizona, USA; Neurosurgery Simulation and Innovation Lab, Mayo Clinic, Phoenix, Arizona, USA. Electronic address:

Objective: Although a significant amount of experience has accumulated for awake procedures for brain tumor, epilepsy, and carotid surgery, its utility for intracranial neurovascular indications remains largely undefined. Awake surgery for select neurovascular cases offers the advantage of precise brain mapping and robust neurologic monitoring during surgery for lesions in eloquent areas, avoidance of potential hemodynamic instability, and possible faster recovery. It also opens the window for perilesional epileptogenic tissue resection with potentially less risk for iatrogenic injury.

Methods: Institutional review board approval was obtained for a retrospective review of awake surgeries for intracranial neurovascular indications over the past 36 months from a prospectively maintained quality database. We reviewed patients' clinical indications, clinical and imaging parameters, and postoperative outcomes.

Results: Eight consecutive patients underwent 9 intracranial neurovascular awake procedures conducted by the senior author. A standardized "sedated-awake-sedated" protocol was used in all 8 patients. For the 2 patients with arteriovenous malformations and the 3 patients with cavernoma, awake brain surface and white matter mapping was performed before and during microsurgical resection. A neurological examination was obtained periodically throughout all 5 procedures. There were no intraoperative or perioperative complications. Hypotension was avoided during the 2 Moyamoya revascularization procedures in the patient with a history of labile blood pressure. Postoperative imaging confirmed complete arteriovenous malformation and cavernoma resections. No new neurologic deficits or new-onset seizures were noted on 3-month follow-up.

Conclusions: Awake surgery appears to be safe for select patients with intracranial neurovascular pathologies. Potential advantages include greater safety, shorter length of stay, and reduced cost.
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http://dx.doi.org/10.1016/j.wneu.2017.03.121DOI Listing
September 2017

Spontaneous resolution of ruptured intracranial pial arteriovenous fistula following spinal surgery.

Neuroradiol J 2017 Apr 2;30(2):175-179. Epub 2017 Feb 2.

Mayo Clinic in Arizona, USA.

Pial arteriovenous fistulae (AVFs) are rare vascular abnormalities that are distinct from arteriovenous malformations and dural AVFs. These vascular lesions have been linked with trauma, ischemic syndromes, venous thrombotic diseases, and intracranial surgical procedures. In this report we describe a case of an intracranial ruptured pial AVF immediately following uneventful spinal surgery in an elderly patient with subsequent spontaneous resolution. He was a previous heavy smoker with a 60-pack-year history and alcohol abuse. His examination was positive for morbid obesity and mild weakness of the anterior tibialis and gastrocnemius muscles bilaterally. He underwent uneventful spinal surgery, suffering a generalized seizure shortly after extubation. Imaging studies demonstrated acute subarachnoid hemorrhage and cerebral angiography identified a pial AVF. He was stabilized medically and follow-up angiography demonstrated spontaneous resolution of the pial AVF. This case highlights a rare vascular malformation with rupture following uneventful spinal surgery.
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http://dx.doi.org/10.1177/1971400916689576DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5433589PMC
April 2017

Understanding Rupture Risk Factors for Intracranial Aneurysms: Which Ticking Time Bomb Needs to be Defused?

Neurosurgery 2016 10;79(4):N11-2

*Department of Neurological Surgery, Northwestern Memorial Hospital and McGaw Medical Center, Chicago, Illinois ‡Department of Neurological Surgery, Mayo Clinic, Phoenix, Arizona.

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http://dx.doi.org/10.1227/01.neu.0000499704.12972.1cDOI Listing
October 2016

Stent Retriever-Assisted Mechanical Thrombectomy for Acute Basilar Artery Occlusion: Single US Institution Experience.

Oper Neurosurg (Hagerstown) 2016 Sep;12(3):250-259

Department of Neurosurgery, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York.

Background: Acute basilar artery occlusion causes devastating strokes that carry high mortality and morbidity.

Objective: To report the outcomes of mechanical thrombectomy in the posterior circulation with a focus on safety and efficacy of stent retrievers.

Methods: We retrospectively reviewed our endovascular database for all patients treated with stent retrievers for posterior circulation stroke between June 2012 and June 2014. Twelve patients were identified. The following data were analyzed: thrombus location, previous stroke or transient ischemic attack, thrombus etiology, comorbidities, time from presentation to initiation of endovascular treatment, time from start of angiography to revascularization, and whether intravenous tissue plasminogen activator was administered pre-thrombectomy. Outcome was considered poor when modified Rankin Scale score was >2.

Results: Mean patient age was 63.42 years (median, 64.5; range, 28-83 years); 7 were women. Successful recanalization (Thrombolysis in Cerebral Infarction grade 2b or 3) was achieved in 11 of 12 patients (91.7%). Mean discharge modified Rankin Scale score was 2.3 (median, 2.0; standard deviation 1.96; range, 0-6), with a favorable discharge outcome in 9 of 12 (75%) patients. Two patients died as inpatients. Mean follow-up modified Rankin Scale score was 1.4 (median, 1.00; standard deviation 1.075; range, 0-4). Good outcome was achieved in 9 of 10 (90%) patients at last follow-up (mean follow-up duration, 132.42 days [median, 90.50; standard deviation 80.2; range, 8-378 days]).

Conclusion: Our single-institution study has shown that good clinical outcomes and successful recanalization with acceptable mortality can be achieved with current stent retrievers.
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http://dx.doi.org/10.1227/NEU.0000000000001163DOI Listing
September 2016

Spinal Schwannoma and Meningioma Mimicking a Single Mass at the Craniocervical Junction Subsequent to Remote Radiation Therapy for Acne Vulgaris.

World Neurosurg 2016 Sep 20;93:484.e13-6. Epub 2016 Jul 20.

Department of Neurosurgery, Houston Methodist Neurological Institute, Houston, Texas, USA.

Background: Schwannomas and meningiomas are relatively common tumors of the nervous system. They have been reported in the literature as existing concurrently as a single mass, but very rarely have they been shown to present at the craniocervical junction.

Case Description: We present a rare and interesting case of a patient previously treated with radiation therapy for acne vulgaris and who presented to us with a concurrent schwannoma and meningioma of the craniocervical junction mimicking a single mass.

Conclusions: These tumors can be solitary or mixed masses, and are known to be associated with certain disease processes such as long-term sequelae of radiation therapy and neurofibromatosis type 2. The precise mechanism behind the formation of these tumors is unknown; however, molecular cues in the tumor microenvironment may play a role.
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http://dx.doi.org/10.1016/j.wneu.2016.07.046DOI Listing
September 2016

Minimally Invasive Tubular Resection of Lumbar Synovial Cysts: Report of 40 Consecutive Cases.

World Neurosurg 2016 Oct 9;94:188-196. Epub 2016 Jul 9.

Department of Neurological Surgery, Mayo Clinic, Arizona. Electronic address:

Background: Lumbar synovial cysts are a relatively common clinical finding. Surgical treatment of symptomatic synovial cysts includes computed tomography-guided aspiration, open resection and minimally invasive tubular resection. We report our series of 40 consecutive minimally invasive microscopic tubular lumbar synovial cyst resections.

Methods: Following Institutional Review Board approval, a retrospective analysis of 40 cases of minimally invasive microscopic tubular retractor synovial cyst resections at a single institution by a single surgeon (B.D.B.) was conducted. Gross total resection was performed in all cases.

Results: Patient characteristics, surgical operating time, complications, and outcomes were analyzed. Lumbar radiculopathy was the presenting symptoms in all but 1 patient, who presented with neurogenic claudication. The mean duration of symptoms was 6.5 months (range, 1-25 months), mean operating time was 58 minutes (range, 25-110 minutes), and mean blood loss was 20 mL (range, 5-50 mL). Seven patients required overnight observation. The median length of stay in the remaining 33 patients was 4 hours. There were 2 cerebrospinal fluid leaks repaired directly without sequelae. The mean follow-up duration was 80.7 months. Outcomes were good or excellent in 37 of the 40 patients, fair in 1 patient, and poor in 2 patients.

Conclusions: Minimally invasive microscopic tubular retractor resection of lumbar synovial cysts can be done safely and with comparable outcomes and complication rates as open procedures with potentially reduced operative time, length of stay, and healthcare costs. Patient selection for microscopic tubular synovial cyst resection is based in part on the anatomy of the spine and synovial cyst and is critical when recommending minimally invasive vs. open resection to patients.
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http://dx.doi.org/10.1016/j.wneu.2016.06.125DOI Listing
October 2016

Patency of anterior circulation branch vessels after Pipeline embolization: longer-term results from 82 aneurysm cases.

J Neurosurg 2017 Apr 10;126(4):1064-1069. Epub 2016 Jun 10.

Departments of 1 Neurosurgery.

OBJECTIVE The Pipeline Embolization Device (PED) has become increasingly used for the treatment of intracranial aneurysms. Given its high metal surface area coverage, there is concern for the patency of branch vessels that become covered by the device. Limited data exist regarding the patency of branch vessels adjacent to aneurysms that are covered by PEDs. The authors assessed the rate of intracranial internal carotid artery, anterior circulation branch vessel patency following PED placement at their institution. METHODS The authors retrospectively reviewed the records of 82 patients who underwent PED treatment between 2009 and 2014 and in whom the PED was identified to cover branch vessels. Patency of the anterior cerebral, posterior communicating, anterior choroidal, and ophthalmic arteries was evaluated using digital subtraction angiography preoperatively and postoperatively after PED deployment and at longer-term follow-up. RESULTS Of the 127 arterial branches covered by PEDs, there were no immediate postoperative occlusions. At angiographic follow-up (mean 10 months, range 3-34.7 months), arterial side branches were occluded in 13 (15.8%) of 82 aneurysm cases and included 2 anterior cerebral arteries, 8 ophthalmic arteries, and 3 posterior communicating arteries. No cases of anterior choroidal artery occlusion were observed. Patients with branch occlusion did not experience any neurological symptoms. CONCLUSIONS In this large series, the longer-term rate of radiographic side branch arterial occlusion after coverage by a flow diverter was 15.8%. Terminal branch vessels, such as the anterior choroidal artery, remained patent in this series. The authors' series suggests that branch vessel occlusions are clinically silent and should not deter aneurysm treatment with flow diversion.
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http://dx.doi.org/10.3171/2016.4.JNS16147DOI Listing
April 2017

Impact of transfer status on hospitalization cost and discharge disposition for acute ischemic stroke across the US.

J Neurosurg 2016 May 9;124(5):1228-37. Epub 2015 Oct 9.

Departments of 1 Neurosurgery.

OBJECT In this study, the authors used information provided in the Nationwide Inpatient Sample (NIS) to study the impact of transferring stroke patients from one facility to a center where they received some form of active stroke intervention (intravenous tissue plasminogen activator, thrombectomy, or a combination of both therapies). METHODS Patient demographic characteristics and hospital factors obtained from the 2008-2010 acute stroke NIS data were analyzed. Discharge disposition, hospitalization cost, and mortality were the dependent variables studied. Univariate analysis and multivariate binary logistic regression analysis were performed. Data analysis focused on the cohort of acute stroke patients who received some form of active intervention (55,913 of 1,311,511 patients in the NIS). RESULTS When overall outcome was considered, transferred patients had a significantly higher number of other-than-routine (OTR, i.e., other than discharge to home without home health care) discharge dispositions (p < 0.0001). In multivariate regression analysis including pertinent patient and hospital factors, transfer-in patients had significantly worse OTR discharge disposition (p < 0.0001, odds ratio [OR] 2.575, 95% CI 2.341-2.832). Mean hospitalization cost including an intervention was $70,325.11 for direct admissions and $97,546.92 for transferred patients. Transfer from another facility (p < 0.001, OR 1.677, 95% CI 1.548-1.817) was associated with higher hospitalization cost. CONCLUSIONS The study showed that hospital cost for acute stroke intervention is significantly higher for a transferred patient than for a direct admission. Moreover, the frequency of OTR discharge was significantly higher among transferred patients than direct admissions. Future strategies should focus on ways and means of transporting patients appropriately and directly to stroke centers.
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http://dx.doi.org/10.3171/2015.4.JNS141631DOI Listing
May 2016
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