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Irving J. Sherman, Ryan M. Kretzer and Rafael J. Tamargo

✓ Walter Edward Dandy (1886–1946) began his surgical training at the Johns Hopkins Hospital in 1910 and joined the faculty in 1918. During the next 28 years at Johns Hopkins, Dandy established a neurosurgery residency training program that was initially part of the revolutionary surgical training system established by William S. Halsted but eventually became a separate entity. Dandy’s residents were part of his “Brain Team,” a highly efficient organization that allowed Dandy to perform over 1000 operations per year, not counting ventriculograms. This team also provided rigorous training in the Halsted mold for the neurosurgical residents. Although exacting and demanding, Dandy was universally admired by his residents and staff. This article describes Dandy’s neurosurgical residency program at Johns Hopkins, and provides personal recollections of training under Walter Dandy.

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Ryan M. Kretzer, Alexander L. Coon and Rafael J. Tamargo

Although Walter E. Dandy (1886–1946) is appropriately credited with the first surgical clipping of an intracranial aneurysm in 1937—a procedure that established the modern field of vascular neurosurgery—his numerous other contributions to this specialty are not as well known. Dandy can be credited with the first detailed description of the vein of Galen malformation, the first description of x-ray visualization of an intracranial aneurysm, the first characterization of basilar artery dolichoectasia, and the publication of the first comprehensive operative case series of arteriovenous malformations, cavernous malformations, and developmental venous anomalies. In addition, Dandy performed the first surgical trapping of a cavernous internal carotid artery (ICA) aneurysm by clipping the supraclinoid ICA and ligating the cervical ICA, and he also executed the first intracranial surgical clipping of the ICA to treat a carotid-cavernous fistula. In this article the authors describe Dandy's contributions to the field of vascular neurosurgery.

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Editorial

Translaminar screws

Andrew Jea

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Wesley Hsu, Ryan M. Kretzer, Michael J. Dorsi and Ziya L. Gokaslan

Wrong-site surgery (WSS) is a rare occurrence that can have devastating consequences for patient care. There are several factors inherent to spine surgery that increase the risk of WSS compared with other types of surgery. Not only can a surgeon potentially operate on the wrong side of the spine or the wrong level, but there are unique issues related to spinal localization that can be challenging for even the most experienced clinicians. The following review discusses important issues that can help prevent WSS during spinal procedures.

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Veit Rohde and Uzma Samadani

Object

Currently no adequate surgical treatment exists for spontaneous intracerebral hemorrhage (ICH). Implantable polymers can be used effectively to deliver therapeutic agents to the local site of the pathological process, thus reducing adverse systemic effects. The authors report the use of stereotactically implanted polymers loaded with tissue plasminogen activator (tPA) to induce lysis of ICH in a rabbit model.

Methods

Ethylene vinyl acetate (EVAc) polymers were loaded with bovine serum albumin (BSA) only or with BSA plus tPA. In vitro pharmacokinetic (three polymers) and thrombolysis (12 polymers) studies were performed. For the in vivo study, 12 rabbits were fixed in a stereotactic frame, and 0.2 ml of clotted autologous blood was injected into the right frontal lobe parenchyma. After 20 minutes, control BSA polymers were stereotactically implanted at the hemorrhage site in six rabbits, and experimental BSA plus tPA polymers were implanted in six rabbits. Animals were killed at 3 days, and blood clot volume was assessed.

The pharmacokinetic study showed release of 146 ng of tPA over 3 days. The tPA activity correlated with in vitro thrombolysis. In the in vivo study, the six animals treated with tPA polymers had a mean (±standard error of the mean [SEM]) thrombus volume of 1.43 ±0.29 mm3 at 3 days, whereas the six animals treated with blank (BSA-only) polymers had a mean (±SEM) thrombus volume of 19.99 ±3.74 mm3 (p <0.001).

Conclusions

Ethylene vinyl acetate polymers release tPA over the course of 3 days. Stereotactic implantation of tPA-loaded EVAc polymers significantly reduced ICH volume. Polymers loaded with tPA may be useful clinically for lysis of ICH without the side effects of systemic administration of tPA.

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Quoc-Anh Thai, Gustavo Pradilla, Federico G. Legnani, Ryan M. Kretzer, Wesley Hsu and Rafael J. Tamargo

Object

Currently no adequate surgical treatment exists for spontaneous intracerebral hemorrhage (ICH). Implantable polymers can be used effectively to deliver therapeutic agents to the local site of the pathological process, thus reducing adverse systemic effects. The authors report the use of stereotactically implanted polymers loaded with tissue plasminogen activator (tPA) to induce lysis of ICH in a rabbit model.

Methods

Ethylene vinyl acetate (EVAc) polymers were loaded with bovine serum albumin (BSA) only or with BSA plus tPA. In vitro pharmacokinetic (three polymers) and thrombolysis (12 polymers) studies were performed. For the in vivo study, 12 rabbits were fixed in a stereotactic frame, and 0.2 ml of clotted autologous blood was injected into the right frontal lobe parenchyma. After 20 minutes, control BSA polymers were stereotactically implanted at the hemorrhage site in six rabbits, and experimental BSA plus tPA polymers were implanted in six rabbits. Animals were killed at 3 days, and blood clot volume was assessed.

The pharmacokinetic study showed release of 146 ng of tPA over 3 days. The tPA activity correlated with in vitro thrombolysis. In the in vivo study, the six animals treated with tPA polymers had a mean (± standard error of the mean [SEM]) thrombus volume of 1.43 ± 0.29 mm3 at 3 days, whereas the six animals treated with blank (BSA-only) polymers had a mean (± SEM) thrombus volume of 19.99 ± 3.74 mm3 (p < 0.001).

Conclusions

Ethylene vinyl acetate polymers release tPA over the course of 3 days. Stereotactic implantation of tPA-loaded EVAc polymers significantly reduced ICH volume. Polymers loaded with tPA may be useful clinically for lysis of ICH without the side effects of systemic administration of tPA.

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Camilo Molina, Daniel M. Sciubba, Christopher Chaput, P. Justin Tortolani, George I. Jallo and Ryan M. Kretzer

Object

Translaminar screws (TLSs) were originally described as a safer alternative to pedicle and transarticular screw placement at C-2 in adult patients. More recently, TLSs have been used in both the cervical and thoracic spine of pediatric patients as a primary fixation technique and as a bailout procedure when dysplastic pedicle morphology prohibits safe pedicle screw placement. Although authors have reported the anatomical characteristics of the cervical and thoracic lamina in adults as well as those of the cervical lamina in pediatric patients, no such data exist to guide safe TLS placement in the thoracic spine of the pediatric population. The goal of this study was to report the anatomical feasibility of TLS placement in the thoracic spine of pediatric patients.

Methods

Fifty-two patients (26 males and 26 females), with an average age of 9.5 ± 4.8 years, were selected by retrospective review of a trauma registry database after institutional review board approval. Study inclusion criteria were an age from 2 to 16 years, standardized axial bone-window CT images of the thoracic spine, and the absence of spinal trauma. For each thoracic lamina the following anatomical features were measured using eFilm Lite software: laminar width (outer cortical and cancellous), laminar height (LH), maximal screw length, and optimal screw trajectory. Patients were stratified by age (an age < 8 versus ≥ 8 years) and sex.

Results

Collected data demonstrate the following general trends as one descends the thoracic spine from T-1 to T-12: 1) increasing laminar width to T-4 followed by a steady decrease to T-12, 2) increasing LH, 3) decreasing maximal screw length, and 4) increasing ideal screw trajectory angle. When stratified by age and sex, male patients older than 8 years of age had significantly larger laminae in terms of both width and height and allowed significantly longer screw placement at all thoracic levels compared with their female counterparts. Importantly, it was found that 78% of individual thoracic laminae, regardless of age or sex, could accept a 4.0-mm screw with 1.0 mm of clearance. As expected, when stratifying by age and sex, it was found that older male patients had the highest acceptance rates.

Conclusions

Data in the present study provide information regarding optimal TLS length, diameter, and trajectory for each thoracic spinal level in pediatric patients. Importantly, the data collected demonstrate no anatomical limitations within the pediatric thoracic spine to TLS instrumentation, although acceptance rates are lower for younger (< 8 years old) and/or female patients. Lastly, given the anatomical variation found in this study, CT scanning can be useful in the preoperative setting when planning TLS use in the thoracic spine of pediatric patients.

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Daniel M. Sciubba, Michael J. Dorsi, Ryan Kretzer and Allan J. Belzberg

✓Use of computed tomography (CT) imaging for evaluation of the cervical spine following blunt trauma is both an efficient and reliable method for detecting injury. As a result, many trauma centers and emergency departments rely exclusively on CT scans to acutely clear the cervical spine of injury. Although quite sensitive for detecting bone injury, CT may be associated with a low sensitivity for detecting herniated discs, injured soft tissue or ligaments, and dynamic instability. In addition, CT-generated artifact may obscure pathological findings. In this case report, we describe the course of a patient whose CT scan harbored CT-generated artifact that suggested traumatic subluxation of the cervical spine. Clinicians should be aware of such artifact and how to recognize it when basing clinical management on such studies.

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Ryan M. Kretzer, Ranice W. Crosby, David A. Rini and Rafael J. Tamargo

✓ Dorcas Hager Padget was a pioneer in the fields of neurosurgical illustration and neuroembryology who practiced during the early 20th century at The Johns Hopkins University. Without a college degree, she trained as a medical illustrator in the Johns Hopkins School of Medicine's Department of Art as Applied to Medicine under Max Brödel. She began her career working for Walter Dandy as his medical artist, gaining worldwide recognition for her neurosurgical illustrations. With Dandy's encouragement, Hager Padget undertook her own scientific research, studying neurodevelopment and aneurysm formation in the circle of Willis by using human embryos from the world-renowned Carnegie Collection. She made lasting contributions to the field of neuroembryology, publishing the first major work on neurodevelopment of the cerebral arterial and venous systems. Following Dandy's death in 1946, Hager Padget began a full-time career as a scientific researcher, first at the Department of Embryology at the Carnegie Institution of Washington in Baltimore and later at the University of Maryland School of Medicine. She continued to make contributions to the field of congenital malformations of the brain and spine, coining the term “neuroschisis” to describe a possible mechanism of neural tube damage leading to the creation of a myelomeningocele. The authors describe Dorcas Hager Padget's contributions to neurosurgical illustration and neuroembryology, as well as her remarkable career.

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Ryan M. Kretzer, Daniel M. Sciubba, Carlos A. Bagley, Jean-Paul Wolinsky, Ziya L. Gokaslan and Ira M. Garonzik

Object

The use of pedicle screws (PSs) for instrument-assisted fusion in the cervical and thoracic spine has increased in recent years, allowing smaller constructs with improved biomechanical stability and repositioning possibilities. In the smaller pedicles of the upper thoracic spine, the placement of PSs can be challenging and may increase the risk of damage to neural structures. As an alternative to PSs, translaminar screws can provide spinal stability, and they may be used when pedicular anatomy precludes successful placement of PSs. The authors describe the technique of translaminar screw placement in the T-1 and T-2 vertebrae.

Methods

Seven patients underwent cervicothoracic fusion to treat trauma, neoplasm, or degenerative disease. Nineteen translaminar screws were placed, 13 at T-1 and six at T-2. A single asymptomatic T-2 screw violated the ventral laminar cortex and was removed.

The mean clinical and radiographic follow up exceeded 14 months, at which time there were no cases of screw pull-out, screw fracture, or progressive kyphotic deformity.

Conclusions

Rigid fixation with translaminar screws offers an attractive alternative to PS fixation, allowing the creation of sound spinal constructs and minimizing potential neurological morbidity. Their use requires intact posterior elements, and care should be taken to avoid violation of the ventral laminar wall.