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Helena Karlberg Hippard, Mehernoor Watcha, Amber J. Stocco and Daniel Curry

Object

Deep brain stimulation (DBS) has become accepted therapy for intractable dystonia and other movement disorders. The accurate placement of DBS electrodes into the globus pallidus internus is assisted by unimpaired microelectrode recordings (MERs). Many anesthetic and sedative drugs interfere with MERs, requiring the patient to be awake for target localization and neurological testing during the procedure. In this study, a novel anesthetic technique was investigated in pediatric DBS to preserve MERs.

Methods

In this paper, the authors describe a sedative/anesthetic technique using ketamine, remifentanil, dexmedetomidine, and nicardipine in 6 pediatric patients, in whom the avoidance of GABAergic stimulating drugs permitted excellent surgical conditions with no detrimental effects on intraoperative MERs. The quality of the MERs, and the frequency of its use in making electrode placement decisions, was reviewed.

Results

All 6 patients had good-quality MERs. The data were of sufficient quality to make a total of 9 trajectory adjustments.

Conclusions

Microelectrode recordings in pediatric DBS can be preserved with a combination of dexmedetomidine and ketamine, remifentanil, and nicardipine. This preservation of MERs is particularly crucial in electrode placement in children.

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Joshua J. Chern, Akash J. Patel, Andrew Jea, Daniel J. Curry and Youssef G. Comair

Object

Focal cortical dysplasia (FCD) is an important cause of intractable epilepsy and is at times treatable by resection. The now widespread use of MR imaging and recent advancement of functional imaging have increased the number of patients undergoing surgical treatment for FCD. The objective of this review is to critically examine and to provide a summary of surgical series on FCD published since 2000.

Methods

Studies concerning surgery for FCD were identified from MEDLINE and references of selected articles and book chapters. Data from these included studies were summarized and analyzed to identify factors correlated with seizure outcome.

Results

Sixteen studies were identified, and 469 patients met our selection criteria. Seizure-free outcome at 1-year postoperatively was achieved in 59.7% of the patients. Children and adults were equally likely to benefit from the surgery. Complete resection (OR 13.7, 95% CI 6.68–28.1; p < 0.0001) and temporal location (OR 2.15, 95% CI 1.26–3.69; p = 0.0073) were two positive prognostic indicators of seizure-free outcome. Utilization of invasive monitoring did not affect the chance of seizure remission, but firm conclusions could not be drawn because patients were not randomized.

Conclusions

The advancement of modern imaging has transformed the process of surgical candidate selection for partial epilepsy due to FCD. Patients from recent surgical series were more homogeneous in their clinical presentations and might represent FCD as an independent pathological entity. This likely explained the improved surgical outcome for this group of patients. These reports also documented the increased utilization of functional imaging, but their efficacy needs to be verified with further studies.

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Ashwin Viswanathan, Katherine Relyea, William E. Whitehead, Daniel J. Curry, Thomas G. Luerssen and Andrew Jea

The authors describe a rare case of pneumothorax as a complication of thoracic pedicle screw placement in an 11-year-old girl undergoing posterior segmental instrumentation for a kyphotic deformity. Spontaneous pneumothorax after posterior fusion for adolescent idiopathic scoliosis has been reported in the orthopedic literature; however, to the best of the authors' knowledge, pneumothorax directly related to pedicle screw placement for spinal deformity has not been previously described. The authors discuss the anatomical and technical aspects leading to this complication and the lessons learned from it.

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Sudhakar Vadivelu, Matthew Willsey, Daniel J. Curry and John W. McDonald III

Chronic neuropathic pain is a debilitating disease process associated with several medical disorders. Different from pain caused by inflammation, neuropathic pain is a diffuse pain disorder often found to be recalcitrant to the limited medical treatments available. Intractable nerve pain may benefit from other therapies capable of longer-lasting pain coverage or greater efficacy. A growing number of reports have emerged suggesting a role for stem cells as a cellular delivery source with neuroprotective agents opposing the effects of nerve damage. Here, the authors review the current experimental therapies examining the use of stem cells for the treatment of neuropathic pain disorders.

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Roukoz B. Chamoun, William E. Whitehead, Daniel J. Curry, Thomas G. Luerssen and Andrew Jea

Object

The use of C-1 lateral mass screws provides an alternative to C1–2 transarticular screws in the pediatric population. However, the confined space of the local anatomy and unfamiliarity with the technique may make the placement of a C-1 lateral mass screw more challenging, especially in the juvenile or growing spine.

Methods

A CT morphometric analysis was performed in 76 pediatric atlases imaged at Texas Children's Hospital from October 1, 2007 until April 30, 2008. Critical measurements were determined for potential screw entry points, trajectories, and lengths, with the goal of replicating the operative technique described by Harms and Melcher for adult patients.

Results

The mean height and width for screw entry on the posterior surface of the lateral mass were 2.6 and 8.5 mm, respectively. The mean medially angled screw trajectory from an idealized entry point on the lateral mass was 16° (range 4 to 27°). The mean maximal screw depth from this same ideal entry point was 20.3 mm. The overhang of the posterior arch averaged 6.3 mm (range 2.1–12.4 mm). The measurement between the left- and right-side lateral masses was significantly different for the maximum medially angled screw trajectory (p = 0.003) and the maximum inferiorly directed angle (p = 0.045). Those measurements in children < 8 years of age were statistically significant for the entry point height (p = 0.038) and maximum laterally angled screw trajectory (p = 0.025) compared with older children. The differences between boys and girls were statistically significant for the minimum screw length (p = 0.04) and the anterior lateral mass height (p < 0.001).

Conclusions

A significant variation in the morphological features of C-1 exists, especially between the left and right sides and in younger children. The differences between boys and girls are clinically insignificant. The critical measurement of whether the C-1 lateral mass in a child could accommodate a 3.5-mm-diameter screw is the width of the lateral mass and its proximity to the vertebral artery. Only 1 of 152 lateral masses studied would not have been able to accommodate a lateral mass screw. This study reemphasizes the importance of a preoperative CT scan of the upper cervical spine to assure safe and effective placement of the instrumentation at this level.

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R. Loch Macdonald, Daniel J. Curry, Yasuo Aihara, Zhen-Du Zhang, Babak S. Jahromi and Reza Yassari

Object. Interest has developed in the use of magnesium (Mg++) as a neuroprotectant and antivasospastic agent. Magnesium may increase cerebral blood flow (CBF) and reduce the contraction of cerebral arteries caused by various stimuli. In this study the authors tested the hypothesis that a continuous intravenous infusion of Mg++ reduces cerebral vasospasm after experimental subarachnoid hemorrhage (SAH).

Methods. A dose-finding study was conducted in five monkeys (Macaca fascicularis) to determine what doses of intravenous MgSO4 elevate the cerebrospinal fluid (CSF) concentrations of Mg++ to vasoactive levels and to determine what effects these doses have on the diameters of cerebral arteries, as shown angiographically. After a standard dose of MgSO4 had been selected it was then administered in a randomized, controlled, blinded study to 10 monkeys (five animals/group) with SAH, beginning on Day 0 and continuing for 7 days, at which time angiography was repeated. A 0.086-g/kg bolus of MgSO4 followed by an infusion of 0.028 g/kg/day MgSO4 significantly elevated serum and CSF levels of Mg++ (five monkeys). Magnesium sulfate significantly elevated the serum level of total Mg++ from a control value of 0.83 ± 0.04 mmol/L to 2.42 ± 1.01 mmol/L on Day 7 and raised the CSF level from 1.3 ± 0.04 mmol/L to 1.76 ± 0.14 mmol/L. There was no angiographic evidence of any effect of MgSO4 on normal cerebral arteries. After SAH, the vasospasm in the middle cerebral artery was not significantly reduced (46 ± 8% in the MgSO4-treated group compared with 35 ± 6% in the placebo [vehicle]-treated group, p > 0.05, unpaired t-test).

Conclusions. Magnesium sulfate did not significantly reduce cerebral vasospasm after SAH in the doses tested. An investigation of SAH is warranted mainly to test whether a benefit can be achieved by neuroprotection or by augmentation of CBF by dilation of small vessels and/or collateral pathways.

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Daniel J. Curry, David A. Wright, Raphael C. Lee, Un Jung Kang and David M. Frim

Object. The surfactant, poloxamer 188 (P-188), has been found to protect against tissue injury in various experimental models. Its protective mechanism may involve the effects of the surfactant against oxidative stress and inflammation. The authors investigated the role of P-188 in the reduction of tissue injury and macrophage response in a model of excitotoxic brain injury in the rat striatum.

Methods. Fifteen Sprague—Dawley rats underwent stereotactic injection of 120 nmol of quinolinic acid into the striatum and received intracisternal injection of vehicle or P-188 (40 mg/kg) at 10 minutes and 4 hours postinjury. Rats were killed after 1 week, and the histological score was determined based on the degree of overall tissue injury (Grades 1–4) at the lesion site. The number of macrophages within the lesioned striatum was compared with that found within the striatum on the nonoperated contralateral side. The scores related to tissue damage and the macrophage ratios of each group were then compared using t-tests.

Striatal injection of the toxin produced a lesion characterized by necrosis and inflammation surrounding the injection site in all six control animals. In rats in which intracisternal P-188 was administered, significantly less tissue injury was demonstrated (mean score 2.45 ± 0.74) than in controls (mean score 3.14 ± 0.75) (p = 0.045). The rats that received intracisternal surfactant also had significantly less macrophage infiltrate (mean ratio 1.06 ± 0.18) than control animals (mean ratio 2.00 ± 0.48) (p = 0.004).

Conclusions. The surfactant P-188 reduces tissue loss and macrophage infiltrate after excitotoxic brain injury in the rat. Possible mechanisms of this effect may include direct surfactant modulation of inflammatory cell membrane fluidity.

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Daniel K. Fahim, Keyne K. Johnson, William E. Whitehead, Daniel J. Curry, Thomas G. Luerssen and Andrew Jea

Periosteal chondromas located in the spine are rare. The authors document an even more infrequent occurrence of a recurrent periosteal chondroma in the cervical spine of a 6-year-old boy. During the operation, a giant (> 7 cm in diameter) periosteal chondroma with involvement of the C-5 and C-6 vertebral bodies was resected. The vertebral column was reconstructed with anterior-posterior instrumentation. The pathological examination revealed that the tumor consisted of chondroid tissue with typical chondrocytes, confirming the diagnosis of periosteal chondroma.

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Joshua J. Chern, Charles G. Macias, Andrew Jea, Daniel J. Curry, Thomas G. Luerssen and William E. Whitehead

Object

Patients with CSF shunts often present to the emergency department (ED) with suspected shunt malfunction. Timely assessment and treatment are important factors affecting patient outcomes. A protocol was implemented at a tertiary children's hospital ED to expedite the care of these patients. This study evaluated the effectiveness of this protocol.

Methods

The protocol assigned all patients with CSF shunts into 1 of 3 pathways. If a patient presented with altered mental status, the Cushing triad, acute focal neurological deficit, ongoing seizure activity, or severe dehydration due to emesis, an ED physician was immediately notified (emergency pathway). If a patient presented with emesis, headache, increasing frequency of seizure, or parental concern for shunt malfunction, the patient entered the expedited pathway, and imaging studies were ordered prior to physician evaluation. All other patients entered the default pathway, in which a physician would evaluate the patient before deciding on further workup. Outcomes of interest included measures of timeliness in the ED and clinical outcomes. Comparisons were made between preprotocol and protocol periods and among the 3 pathways.

Results

The total time to complete both ED physician evaluation and to initiate imaging studies was significantly shorter in the protocol period than in the preprotocol period (104 vs 147 minutes). Similar time saving over the 2 processes was demonstrated comparing expedited and default pathways during the protocol period (95 vs 134 minutes, a 29% difference). Clinically, more patients underwent surgery in the expedited pathway than the default pathway (36% vs 17%), and patients in the expedited pathway had a shorter hospital stay (3.4 ± 0.9 days vs 5.7 ± 4.0 days; p = 0.02).

Conclusions

An ED-based protocol helped identify patients at risk for shunt failure early in the triage process and shortened the assessment process prior to neurosurgical intervention. Improving the timeliness of care for patients with shunt failure is important because morbidity and mortality associated with shunt failure are time dependent.

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Akash J. Patel, Jacob Cherian, Benjamin D. Fox, William E. Whitehead, Daniel J. Curry, Thomas G. Luerssen and Andrew Jea

Object

National and international meetings, such as the Congress of Neurological Surgeons (CNS) and the American Association of Neurological Surgeons (AANS) meetings, provide a central location for the gathering and dissemination of research. The purpose of this study was to determine the publication rates of both oral and poster presentations at CNS and AANS meetings in peer-reviewed journals.

Methods

The authors reviewed all accepted abstracts, presented as either oral or poster presentations, at the CNS and AANS meetings from 2003 to 2005. This information was then used to search PubMed to determine the rate of publication of the abstracts presented at the meetings. Abstracts were considered published if the data presented at the meeting was identical to that in the publication.

Results

The overall publication rate was 32.48% (1243 of 3827 abstracts). On average, 41.28% of oral presentations and 29.03% of poster presentations were eventually published. Of those studies eventually published, 98.71% were published within 5 years of presentation at the meeting. Published abstracts were published most frequently in the Journal of Neurosurgery and Neurosurgery.

Conclusions

Approximately one-third of all presentations at the annual CNS and AANS meetings will be published in peer-reviewed, MEDLINE-indexed journals. These meetings are excellent forums for neurosurgical practitioners to be exposed to current research. Oral presentations have a significantly higher rate of eventual publication compared with poster presentations, reflecting their higher quality. The Journal of Neurosurgery and Neurosurgery have been the main outlets of neurosurgical research from these meetings.