Dmitriy Petrov

Three-Dimensional Printed Modeling of an Arteriovenous Malformation Including Blood Flow

BACKGROUND Arteriovenous malformations (AVMs) represent a complex pathologic entity in terms of their associated angioarchitecture and blood flow dynamics. METHODS Using existing imaging data, we generated a patients giant AVM to scale. RESULTS A series of 3-dimensional (3D) models were generated and blood flow dynamics were represented. Faculty and resident surveys were positive regarding the technology. CONCLUSIONS This report represents a novel application of 3D printing in neurosurgery and a means to model dynamic blood flow in 3 dimensions. The 3D printed models may improve on our ability to plan for and treat complex vascular pathologies.

Dermatologic Presentations of Orthopedic Pathologies

Dermatologic presentations of orthopedic diseases are commonly encountered in the dermatology clinic. These disorders often necessitate prompt recognition in order to properly refer for definitive treatment as well as to avoid unnecessary diagnostic procedures. As such, the presentations of these diseases as well as the treatments available deserve special attention. This review aims to identify orthopedic diseases with dermatologic presentations and discuss the diagnosis and treatment of these pathologies. In conducting this review, a comprehensive literature search was conducted. Our inquiry was limited to conditions with a unitary orthopedic etiology. By excluding syndromic dysfunctions with both orthopedic and dermatologic manifestations, we were able to create a consistent approach to the review. At the same time, such exclusions created an omission of many important disease processes that require the cooperation of orthopedists and dermatologists. In all, 19 orthopedic disorders and disorder classes with dermatologic findings were identified and carefully examined.The orthopedic pathologies identified require varying diagnostic and therapeutic approaches. While some do not warrant further work-up or referral, the disease course of certain pathologies is drastically altered by timely recognition, cautious diagnostic interrogation, and prompt referral.

Endoscopic versus microscopic microvascular decompression for trigeminal neuralgia: equivalent pain outcomes with possibly decreased postoperative headache after endoscopic surgery

OBJECTIVE Endoscopic surgery has revolutionized surgery of the ventral skull base but has not yet been widely adopted for use in the cerebellopontine angle. Given the relatively normal anatomy of the cerebellopontine angle in patients with trigeminal neuralgia (TN), the authors hypothesized that a fully endoscopic microvascular decompression (E-MVD) might provide pain outcomes equivalent to those of microscopic MVD (M-MVD) but with fewer complications. METHODS The authors conducted a single-institution, single-surgeon retrospective study with patients treated in the period of 2006-2013. Before surgery, all patients completed a questionnaire that included a validated multidimensional pain-outcome tool, the Penn Facial Pain Scale (PFPS, formerly known as Brief Pain Inventory-Facial), an 11-point scale that measures pain intensity, interference with general activities of daily living (ADLs), and facial-specific ADLs. Using a standardized script, independent research assistants conducted follow-up telephone interviews. RESULTS In total, 167 patients were available for follow-ups (66.5% female; 93 patients underwent M-MVD and 74 underwent E-MVD). Preoperative characteristics (i.e., TN classification, PFPS components, and medication use) were similar for the 2 surgical groups except for 2 variables. Patients in the M-MVD group had slightly higher incidence of V3 pain, and the 2 groups differed in the date of surgery and hence in the length of follow-up (2.4 years for the M-MVD group and 1.3 years for the E-MVD group, p < 0.05). There was a trend toward not finding neurovascular conflict at the time of surgery more frequently in the M-MVD than in the E-MVD group (11% vs 7%, p = 0.052). Internal neurolysis was more often performed in the E-MVD group (26% vs 7%, p = 0.001). The 2 groups did not significantly differ in the length of the MVD procedure (approximately 2 hours). Self-reported headaches at 1 month postoperatively were present in 21% of the patients in the M-MVD group versus 7% in the E-MVD group (p = 0.01). Pain outcomes at the most recent followup were equivalent, with patients reporting a 5- to 6-point (70%-80%) improvement in pain intensity, a 5-point (85%) improvement in pain interference with ADLs, and a 6-point (85%) improvement in interference with facial-specific ADLs. Actuarial freedom from pain recurrence was equivalent in the 2 groups, with 80% pain control at 3 years. CONCLUSIONS Both the fully endoscopic MVD and the conventional M-MVD appear to provide patients with equivalent pain outcomes. Complication rates were also similar between the groups, with the exception of the rate of headaches, which was significantly lower in the E-MVD group 1 month postoperatively.

The Evolution of Neuroprosthetic Interfaces.

The ideal neuroprosthetic interface permits high-quality neural recording and stimulation of the nervous system while reliably providing clinical benefits over chronic periods. Although current technologies have made notable strides in this direction, significant improvements must be made to better achieve these design goals and satisfy clinical needs. This article provides an overview of the state of neuroprosthetic interfaces, starting with the design and placement of these interfaces before exploring the stimulation and recording platforms yielded from contemporary research. Finally, we outline emerging research trends in an effort to explore the potential next generation of neuroprosthetic interfaces.

The nasofrontal beak: A consistent landmark for superior septectomy during Draf III drill out.

Introduction Cerebrospinal fluid (CSF) leak occurs in 1-11% of endoscopic Draf III, or endoscopic modified Lothrop, procedures. CSF leak can occur during surgery during a superior nasal septectomy. This study investigated whether the posterior edge of the nasofrontal beak (NFB) at the level of the internal frontal ostium is a safe landmark to use to avoid skull base injury when beginning the superior septectomy. Methods Preoperative computed tomography maxillofacial scans were reviewed from 100 patients from the University of Pennsylvania sinus surgery data base. The narrowest anteroposterior distance between the posterior edge of the NFB and the anterior aspect of the olfactory fossa (OF) at the level of the internal frontal ostium was measured in each patient. Measurements were taken in the midline and to the left and right of midline. Six fresh cadaver heads were also dissected to evaluate these relationships. Results On computed tomography analysis, the NFB was anterior to the OF on the left and right of the midline in 100% of the patients, with mean distances of 6.04 and 6.41 mm, respectively. The NFB was anterior to the OF in the midline in 98% of patients, with a mean distance of 9.02 mm. In all six cadavers, the posterior edge of the NFB was anterior to the OF in the midline and to the left and right of midline at the level of the internal frontal ostia. Conclusions During Draf III, the posterior edge of the NFB was a reliable landmark for avoiding iatrogenic CSF leak during the superior septectomy.

Two- versus four-handed techniques for endonasal resection of orbital apex tumors.

Background Open versus endonasal resection of orbital apex (OA) tumors is generally based on tumor size, location, and pathology. For endonasal resection, two- and four-handed techniques have been reported, but whether one technique is more optimal based on these tumor features has not been evaluated. Objective To determine whether two- versus four-handed techniques result in better outcomes after endoscopic resection of OA tumors, and whether either technique is better suited for intra- versus extraconal location and for benign versus malignant pathology. Methods A retrospective review of all expanded endonasal approaches for OA tumors was performed at a single institution from 2009 to 2013. A PubMed database search was also performed to review series published on endonasal OA tumor resection. Across all the cases reviewed, the following data were recorded: two- versus four-handed techniques, intra- versus extraconal tumor location, and benign versus malignant pathology. The relationship between these variables and resection extent was analyzed by the Fisher exact test. Postoperative visual status and complications were also reviewed. Results Ten cases from the institution and 94 cases from 17 publications were reviewed. Both two- and four-handed techniques were used to resect extra-and intraconal OA tumors, for both benign and malignant pathology. Four-handed techniques included a purely endonasal approach and a combined endonasal-orbital approach. On univariate analysis, the strongest predictor of complete resection was benign pathology (p = 0.005). No significant difference was found between the extent of resection and a two- versus a four-handed technique. Visual status was improved or unchanged in 94% of cases, and other complications were rare. Conclusion Benign tumors that involve the medial extraconal and posterior inferomedial intraconal OA can be treated by either two- or four-handed endonasal techniques. Selecting two- versus four-handed techniques and endonasal versus endonasal-orbital four-handed techniques depends mainly on surgeons’ experience. Endonasal approaches for malignant OA tumors are less likely to result in complete resection.

De Novo Intraneural Arachnoid Cyst Presenting with Complete Third Nerve Palsy: Case Report and Literature Review

BACKGROUND Intraneural arachnoid cyst is an extremely rare etiology of isolated cranial nerve palsy. Although seldom encountered in clinical practice, this pathology is amenable to surgical intervention. Correct identification and treatment of the cyst are required to prevent permanent nerve damage and potentially reverse the deficits. We describe a rare case of isolated third nerve palsy caused by an intraneural arachnoid cyst. CASE DESCRIPTION A 49-year-old woman with a recent history of headaches experienced acute onset of painless left-sided third nerve palsy. According to hospital records ptosis, mydriasis, absence of adduction, elevation, and intorsion were noted in the left eye. Computed tomography and magnetic resonance imaging studies showed an extra-axial, 1-cm lesion along the left paraclinoid region, causing mild indentation on the uncus. There was dense fluid layering dependently concerning for hemorrhage, but no evidence of aneurysms. A pterional craniotomy was performed, revealing a completely intraneural arachnoid cyst in the third nerve. The cyst was successfully fenestrated. At 7-month follow-up, the left eye had recovered intact intorsion and some adduction, but the left pupil remained dilated and nonreactive. There was still no elevation and no afferent pupillary defect. Double vision persisted with partial improvement in the ptosis, opening up to more than 75% early in the day. CONCLUSION To our knowledge, this is the first report of an intraneural arachnoid cyst causing isolated third nerve palsy. This rare pathology proves to be both a diagnostic and therapeutic challenge.

Optically-Controlled \"Living Electrodes\" with Long-Projecting Axon Tracts for a Synaptic Brain-Machine Interface

Achievements in intracortical neural interfaces are compromised by limitations in specificity and long-term performance. A biological intermediary between devices and the brain may offer improved specificity and longevity through natural synaptic integration with deep neural circuitry, while being accessible on the brain surface for optical read-out/control. Accordingly, we have developed the first “living electrodes” comprised of implantable axonal tracts protected within soft hydrogel cylinders for the biologically-mediated monitoring/modulation of brain activity. Here we demonstrate the controlled fabrication, rapid axonal outgrowth, reproducible cytoarchitecture, and simultaneous optical stimulation and recording of neuronal activity within these engineered constructs in vitro. We also present their transplantation, survival, integration, and optical recording in rat cortex in vivo as a proof-of-concept for this neural interface paradigm. The creation and functional validation of these preformed, axon-based “living electrodes” is a critical step towards developing a new class of biohybrid neural interfaces to probe and modulate native circuitry.

Extracellular matrix-derived tissues for neurological applications

Nervous system injury and degeneration may result in debilitating conditions that limit quality of life. To facilitate nervous system repair and improve functional outcomes, clinicians and researchers are utilizing therapies that provide proregenerative cues and structural support using exogenous extracellular matrix (ECM) derived neurological implants. These strategies are generally intended to structurally replace excised tissues, facilitate tissue regrowth, aid in hemostasis, and/or assist in the delivery of bioactive substances. ECM-based products offer several distinct advantages over synthetic materials, including bioactivity, active remodeling, and decreased inflammatory and foreign body responses. A range of naturally occurring, ECM-based materials including laminin, collagen, hyaluronic acid, and fibronectin are being applied as biomaterial scaffolds, either alone or augmented with growth factors and/or living cells to promote nervous system repair and regeneration. The chapter presents the current uses of ECM-based neurological implants and future directions in the development of restorative ECM-based biomaterials, constructs, and other implants.

Dermatologic presentations of orthopedic pathologies: a review of diagnosis and treatment.

Dermatologic presentations of orthopedic diseases are commonly encountered in the dermatology clinic. These disorders often necessitate prompt recognition in order to properly refer for definitive treatment as well as to avoid unnecessary diagnostic procedures. As such, the presentations of these diseases as well as the treatments available deserve special attention. This review aims to identify orthopedic diseases with dermatologic presentations and discuss the diagnosis and treatment of these pathologies. In conducting this review, a comprehensive literature search was conducted. Our inquiry was limited to conditions with a unitary orthopedic etiology. By excluding syndromic dysfunctions with both orthopedic and dermatologic manifestations, we were able to create a consistent approach to the review. At the same time, such exclusions created an omission of many important disease processes that require the cooperation of orthopedists and dermatologists. In all, 19 orthopedic disorders and disorder classes with dermatologic findings were identified and carefully examined. The orthopedic pathologies identified require varying diagnostic and therapeutic approaches. While some do not warrant further work-up or referral, the disease course of certain pathologies is drastically altered by timely recognition, cautious diagnostic interrogation, and prompt referral.