Daniel J. Curry

MR-guided stereotactic laser ablation of epileptogenic foci in children☆

OBJECTIVE For about 30% of epilepsy patients, pharmaceutical therapy fails to control their seizures. MR-guided laser interstitial thermal therapy (MRgLITT) allows for real-time thermal monitoring of the ablation process and feedback control over the laser energy delivery. We report on minimally invasive surgical techniques of MRgLITT and short-term follow-up results from the first five pediatric cases in which this system was used to ablate focal epileptic lesions. METHODS We studied the patients with MRI of the brain, localized the seizure with video-EEG and used the Visualase Thermal Therapy 25 System for laser ablation of their seizure foci. RESULTS All 5 patients are seizure free and there were no complications as of 2-13-month follow-up. CONCLUSION MR-guided laser interstitial thermal therapy has a significant potential to be a minimally invasive alternative to more conventional techniques to surgically treat medically refractory epilepsy in children.

Hypothalamic hamartomas: optimal approach to clinical evaluation and diagnosis.

Hypothalamic hamartomas (HHs) present a difficult medical problem, manifested by gelastic seizures, which are often medically intractable. Although existing techniques offer modest surgical outcomes with the potential for significant morbidity, the relatively novel technique of magnetic resonance imaging (MRI)–guided stereotactic laser ablation (SLA) offers a potentially safer, minimally invasive method with high efficacy for the HH treatment. We report here on 14 patients with medically refractory gelastic epilepsy who underwent stereotactic frame–based placement of an MR‐compatible laser catheter (1.6 mm diameter) through a 3.2‐mm twist drill hole. A U.S. Food and Drug Administration (FDA)–cleared laser surgery system (Visualase, Inc.) was utilized to ablate the HH, using real‐time MRI thermometry. Seizure freedom was obtained in 12 (86%) of 14 cases, with mean follow‐up of 9 months. There were no permanent surgical complications, neurologic deficits, or neuroendocrine disturbances. One patient had a minor subarachnoid hemorrhage that was asymptomatic. Most patients were discharged home within 1 day. SLA was demonstrated to be a safe and effective minimally invasive tool in the ablation of epileptogenic HH. Because use of SLA for HH is being adopted by other medical centers, further data will be acquired to help treat this difficult disorder.

Effects of two non-endurance exercise protocols on established bone loss in ovariectomized adult rats

SummaryThe effects of non-endurance exercise on bone properties were evaluated in 9-month-old sham-operated (SH) and ovariectomized (OVX) rats. The studies were started 3 months postsurgery, after bone mass was decreased in OVX rats. The sham and OVX rats were either kept sedentary (SED) or were trained to run with one of two protocols: 12 m/minute, 50 minutes/day, 4 days/week (low intensity, frequent, EX-1); or 21 m/minute, 40 minutes/day, 1 day/week (moderate intensity, infrequent, EX-2). A group of seven rats evaluated at the beginning of the study served as baseline control. The bone mineral was assessed by the ash weight of the left femur, tibia, and 4th lumbar vertebra. Biomechanical (strength, deformation, stress, strain, and stiffness) and morphometric (length, cortical and medullary area, moment of inertia) properties were evaluated for the right femur. There was a significantly lower bone mineral and mechanical properties in OVX-SED (n=7) than in SH-SED (n=10) rats. The OVX-EX-1 (n=6) rats had higher ash content of femur and tibia than OVX-SED rats, but the change was significant only for tibia. The EX-2 had no effect on the ash content, but femur stress was higher in OVX-EX-2 (n=8) than in OVX-SED rats. The femur yield force and deformation were improved in OVX rats with both exercise protocols, whereas the vertebra ash weight, femur strain, modulus of elasticity, length, cortical area, and moment of inertia were not changed. Non-endurance exercise did not affect bone properties in either SH-EX-1 (n=7) or SH-EX-2 (n=8) groups. We conclude that non-endurance exercise has beneficial effects on established osteopenia in ovariectomized rats.

Effects of endurance exercise on bone histomorphometric parameters in intact and ovariectomized rats

Physical activity is important for maintenance of bone mass. The effects of exercise on bone histomorphometry were studied in 9-month-old intact (INT) and ovariectomized (OVX) rats. The rats were either kept sedentary (SED) or were exercised (EX) on a treadmill at 21 m/min for 1 h/day 5 days/week for 3 months. Bone resorption as well as formation parameters were significantly higher in OVX-SED than in INT-SED rats, indicating increased bone turnover in OVX rats. In OVX rats, lower osteoclast perimeter and number, lower labeled perimeter but higher mineral apposition rate (MAR) and bone formation rate (BFR) were associated with higher trabecular bone in OVX-EX compared with OVX-SED rats. In intact rats, trabecular bone mass and osteoclast number and perimeter were not affected by exercise. Labeled perimeter was slightly lower while MAR was higher and BFR was insignificantly higher in INT-EX than in INT-SED rats. Thus, exercise resulted in fewer resorption-formation sites, as indicated by lower labeled perimeter, but higher activity of individual osteoblasts, as indicated by higher MAR, both in estrogen-depleted and estrogen-replete states.

USE OF AXIAL AND SUBAXIAL TRANSLAMINAR SCREW FIXATION IN THE MANAGEMENT OF UPPER CERVICAL SPINAL INSTABILITY IN A SERIES OF 7 CHILDREN

OBJECTIVEThe management of upper cervical spinal instability in children continues to represent a technical challenge. Traditionally, a number of wiring techniques followed by halo orthosis have been applied; however, they have been associated with a high rate of nonunion and poor tolerance for the halo. Alternatively, C1–C2 transarticular screws and C2 pars/pedicle screws allow more rigid fixation, but they are technically demanding and associated with vertebral artery injuries. Recently, C2 translaminar screws have been added to the armamentarium of the pediatric spine surgeon as a technically simple and biomechanically efficient method of fixation. However, subaxial translaminar screws have not been described in the pediatric population. We describe our experience with axial and subaxial translaminar screws in 7 pediatric patients. METHODSSeven pediatric patients with the diagnosis of upper cervical spinal instability required surgical fixation (age, 19 months–14 years; sex, 4 boys and 3 girls; follow-up, 4–21 months; etiology, trauma [3 patients], os odontoideum/os terminale [2 patients], hypoplastic dens [2 patients]). All patients underwent axial and/or subaxial translaminar screw insertion. Iliac crest bone graft was used for fusion in 4 patients; bone morphogenic protein and cancellous morselized allograft was used for fusion in 3 patients. A rigid cervical collar was applied for 12 weeks postoperatively in all cases. No intraoperative image guidance was used for insertion of the translaminar screws. RESULTSAll patients had a postoperative computed tomographic scan. Two patients underwent placement of bilateral crossing C2 translaminar screws. Two patients had subaxial translaminar screw placement at C3 and the upper thoracic spine, respectively. Hybrid constructs (a C2 translaminar screw combined with a C2 pars screw) were incorporated in 3 patients. No patients were found to have a breach of the ventral laminar cortex. All patients achieved solid fusion. One patient had a perioperative complication: prolonged dysphagia probably related to C1 lateral mass screw insertion rather than C2 translaminar screw placement. CONCLUSIONTo our knowledge, this report represents the only series of pediatric patients treated with axial and subaxial translaminar screws. This series shows that axial and subaxial translaminar screw fixation is a viable option for upper cervical spinal fusion in children. The technique is safe and results in adequate fixation with high fusion rates and minimal complications.

Routine use of recombinant human bone morphogenetic protein-2 in posterior fusions of the pediatric spine: safety profile and efficacy in the early postoperative period.

BACKGROUND:Previous studies using recombinant human bone morphogenetic protein-2 (rhBMP-2) in the adult lumbar spine have shown consistently good results. There have been no pediatric case series. OBJECTIVE:To determine the safety and efficacy of rhBMP-2 use in posterior instrumented fusions of the pediatric population. METHODS:A retrospective review of 19 consecutive pediatric patients who underwent posterior occiptocervical, cervical, thoracic, lumbar, or lumbosacral spine fusion from October 1, 2007, to June 30, 2008, at Texas Childrens Hospital was performed. The average age was approximately 12 years old (range, 9 months to 20 years). The minimum follow-up was 17 months (average of 19 months, range: 17–25 months), with computed tomography (CT) evaluation and grading of fusion by an independent radiologist at 3 months after surgery. RESULTS:The average CT grade was 3, indicating bilateral bridging bone. No pseudoarthroses or loss of correction was identified clinically or radiographically at 3 months and latest follow-up. There was one complication of bony overgrowth and restenosis of the spinal canal necessitating reoperation, and two superficial wound infections. There were no deep wound infections. CONCLUSION:Early outcomes using rhBMP-2 in the pediatric population show that it is a safe and efficacious adjunct to posterior spine fusions of the occipitocervical, cervical, thoracic, lumbar, and lumbosacral spine. It dependably results in the development of stable bridging bone at 3 months after surgery with good maintenance of correction and stability in long-term follow-up. Lessons learned from the case of unexpected bony overgrowth are discussed.

Neurosurgical emergency transfers to academic centers in Cook County: a prospective multicenter study.

OBJECTIVEThe absence of surgical subspecialty emergency care in the United States is a growing public health concern. Neurosurgery is a field lacking coverage in many areas of the country; however, this is generally thought to be of greater concern in rural areas. Because of decreasing numbers of neurosurgeons, medical malpractice, and liability concerns, neurosurgery coverage is becoming a public health crisis in urban areas. Our objective was to quantify neurosurgical emergency transfers to academic medical centers in Cook County, IL, including patient demographics, reasons for transfer, time lapse in transfer, and effects on patient condition. methodsData on neurosurgery emergency transfers was gathered prospectively by all five of the academic neurosurgery departments in Cook County, IL, over a 2-month period. Patient demographics devoid of identifiers, diagnosis, transfer origin, time lapse of transfer, and patient condition at the time of transfer and at the receiving hospital were recorded. RESULTSTwo-hundred thirty emergent neurosurgical transfers occurred during the study period. The most common diagnoses were parenchymal intracerebral hemorrhage (33%) and subarachnoid hemorrhage (28%). Sixty-six percent of neurosurgical transfers to academic medical facilities originated at hospitals without full-time neurosurgery coverage. The mean time to transfer for all patients was 5 hours 10 minutes (standard deviation, 3 h 42 min; range, 1–20 h 12 min). A decline in Glasgow Coma Scale score was seen in 29 patients. A shortage of neurosurgical intensive care unit beds occurred on 55% of the days in the study. Only 19% of the emergency cases were related to cranial trauma, and only 3% of transfers came from Level 1 trauma centers. CONCLUSIONA combination of factors has led to decreases in availability of neurosurgical coverage in Cook County community hospital emergency departments. This has placed an increased burden on neurosurgical departments at academic centers, and, in some cases, delays led to a decline in patient condition. Eighty-one percent of the cases were not related to cranial trauma; thus, acute care trauma surgeons would be of little use. Coordinated efforts among local governments, medical centers, and emergency medical services to regionalize subspecialty services will be necessary to manage this problem.

Publication patterns of oral and poster presentations at the annual meetings of the Congress of Neurological Surgeons and the American Association of Neurological Surgeons

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.

Computed tomography morphometric analysis for axial and subaxial translaminar screw placement in the pediatric cervical spine

OBJECT The management of upper cervical spinal instability in children continues to represent a technical challenge. Traditionally, a number of wiring techniques followed by halo orthosis have been applied; however, they have been associated with a high rate of nonunion and poor tolerance for the halo. Alternatively, C1-2 transarticular screws and C-2 pars/pedicle screws allow more rigid fixation, but their placement is technically demanding and associated with vertebral artery injuries. Recently, C-2 translaminar screws have been added to the armamentarium of the pediatric spine surgeon as a technically simple and biomechanically efficient means of fixation. However, the use of subaxial translaminar screws have not been described in the general pediatric population. There are no published data that describe the anatomical considerations and potential limitations of this technique in the pediatric population. METHODS The cervical vertebrae of 69 pediatric patients were studied on CT scans. Laminar height and thickness were measured. Statistical analysis was performed using unpaired Student t-tests (p<0.05) and linear regression analysis. RESULTS The mean laminar heights at C-2, C-3, C-4, C-5, C-6, and C-7, respectively, were 9.76+/-2.22 mm, 8.22+/-2.24 mm, 8.09+/-2.38 mm, 8.51+/-2.34 mm, 9.30+/-2.54 mm, and 11.65+/-2.65 mm. Mean laminar thickness at C-2, C-3, C-4, C-5, C-6, and C-7, respectively, were 5.07+/-1.07 mm, 2.67+/-0.79 mm, 2.18+/-0.73 mm, 2.04+/-0.60 mm, 2.52 +/- 0.66 mm, and 3.84+/-0.96 mm. In 50.7% of C-2 laminae, the anatomy could accept at least 1 translaminar screw (laminar thickness>or=4 mm). CONCLUSIONS Overall, the anatomy in 30.4% of patients younger than 16 years old could accept bilateral C-2 translaminar screws. However, the anatomy of the subaxial cervical spine only rarely could accept translaminar screws. This study establishes anatomical guidelines to allow for accurate and safe screw selection and insertion. Preoperative planning with thin-cut CT and sagittal reconstruction is essential for safe screw placement using this technique.

Intraoperative monitoring of motor evoked potentials in very young children.

OBJECT Neurophysiological monitoring of motor evoked potentials (MEPs) during complex spine procedures may reduce the risk of injury by providing feedback to the operating surgeon. While this tool is a well-established surgical adjunct in adults, clinical data in children are sparse. The purpose of this study was to determine the reliability and safety of MEP monitoring in a group of children younger than 3 years of age undergoing neurosurgical spine procedures. METHODS A total of 10 consecutive spinal procedures in 10 children younger than 3 years of age (range 5-31 months, mean 16.8 months) were analyzed between January 1, 2008, and May 1, 2010. Motor evoked potentials were elicited by transcranial electric stimulation. A standardized anesthesia protocol for monitoring consisted of a titrated propofol drip combined with bolus dosing of fentanyl or sufentanil. RESULTS Motor evoked potentials were documented at the beginning and end of the procedure in all 10 patients. A mean baseline stimulation threshold of 533 ± 124 V (range 321-746 V) was used. Six patients maintained MEP signals ≥ 50% of baseline amplitude throughout the surgery. There was a greater than 50% decrease in intraoperative MEP amplitude in at least 1 extremity in 4 patients. Two of these patients returned to baseline status by the end of the case. Two patients had a persistent decrement or variability in MEP signals at the end of the procedure; this correlated with postoperative weakness. There were no complications related to the technique of monitoring MEPs. CONCLUSIONS A transcranial electric stimulation protocol monitoring corticospinal motor pathways during neurosurgical procedures in children younger than 3 years of age was reliably and safely implemented. A persistent intraoperative decrease of greater than 50% in this small series of 10 pediatric patients younger than 3 years of age predicted a postoperative neurological deficit. The authors advocate routine monitoring of MEPs in this pediatric age group undergoing neurosurgical spine procedures.