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Andrew Jea, Keyne K. Johnson, William E. Whitehead and Thomas G. Luerssen

The use of spinal instrumentation to stabilize the occipitocervical junction in pediatric patients has increased and evolved in recent years. Wiring techniques have now given way to screw-rod or screw-plate techniques with or without postoperative external immobilization. Although C-2 translaminar screws have been used in these constructs, subaxial translaminar screws have not, to date, been described in either the pediatric or adult patient populations.

The authors describe the feasibility of translaminar screw placement in the C-3 lamina. Rigid fixation with translaminar screws offers an alternative to subaxial fixation with lateral mass screws, allowing for formation of biomechanically sound spinal constructs and minimizing potential neurovascular morbidity. Their use requires careful analysis of preoperative imaging studies, intact posterior elements, and avoidance of violation of the inner laminar wall.

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

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 ≥ 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.

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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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Daniel K. Fahim, Katherine Relyea, Vikram V. Nayar, Benjamin D. Fox, William E. Whitehead, Daniel J. Curry, Thomas G. Luerssen and Andrew Jea

The authors describe the novel use of a table-mounted tubular retractor system (MetRx) originally designed for minimally invasive spine surgery, in the resection of an intraventricular arteriovenous malformation (AVM) in a 12-year-old child. The tubular retractor system may have several advantages over traditional Greenberg or Leyla retractors in selected intracranial procedures. In our case, the low-profile 4 × 22–mm tube and fixed table attachment offered excellent exposure of the trigone of the lateral ventricle where the choroidal AVM was located and from which it was completely resected. Immediate postoperative cerebral angiography confirmed that the entire AVM had been resected. The patient suffered no new neurological deficits as a result of the retractor system or the exposure that it afforded. Although the good clinical results of a single case cannot be directly compared with those obtained using other open techniques of intracranial surgery in larger series, microendoscopic surgery of the brain is an alternative to the other techniques and may be recommended as a time-saving, trauma-reducing procedure with the potential to improve postoperative outcomes.

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Joshua J. Chern, Katherine Relyea, Jane C. Edmond, William E. Whitehead, Daniel J. Curry, Thomas G. Luerssen and Andrew Jea

Selective downward gaze paralysis has not previously been described as a complication after posterior fossa operations in children. The authors found downgaze palsy to be a transient complication after resection of large pediatric posterior fossa midline tumors reaching the aqueduct of Sylvius. They reviewed the cases of 2 children with large posterior fossa midline tumors who underwent resection via an inferior transventricular approach. They developed a hypothetical scheme to account for downward gaze paralysis based on anatomy and insight gained from experimental studies.

The authors describe potential risk factors for developing transient selective downward gaze paralysis with the hope of making more pediatric neurosurgeons aware of this complication following removal of lesions around the mesencephalic periaqueductal gray matter. Recognition and understanding of downward gaze palsy after posterior fossa surgery should improve preoperative counseling and promote postoperative family coping.

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John C. Wellons III, Chevis N. Shannon, Abhaya V. Kulkarni, Tamara D. Simon, Jay Riva-Cambrin, William E. Whitehead, W. Jerry Oakes, James M. Drake, Thomas G. Luerssen, Marion L. Walker, John R. W. Kestle and for the Hydrocephalus Clinical Research Network

Object

The purpose of this study was to define the incidence of permanent shunt placement and infection in patients who have undergone the 2 most commonly performed temporizing procedures for posthemorrhagic hydrocephalus (PHH) of prematurity: ventriculosubgaleal (VSG) shunt placement and ventricular reservoir placement for intermittent tapping.

Methods

The 4 centers of the Hydrocephalus Clinical Research Network participated in a retrospective chart review of infants with PHH who underwent treatment at each institution between 2001 and 2006. Patients were included if they had received a diagnosis of Grade 3 or 4 intraventricular hemorrhage, weighed < 1500 g at birth, and had received surgical intervention. The authors determined the incidence of conversion from a temporizing device to a permanent shunt, the incidence of CSF infection during temporization, and the 6-month CSF infection rate after permanent shunt placement.

Results

Thirty-one (86%) of 36 patients who received VSG shunts and 61 (69%) of 88 patients who received ventricular reservoirs received permanent CSF diversion with a shunt (p = 0.05). Five patients (14%) in the VSG shunt group had CSF infections during temporization, compared with 11 patients (13%) in the ventricular reservoir group (p = 0.83). The 6-month incidence of permanent shunt infection in the VSG shunt group was 16% (5 of 31), compared with 12% (7 of 61) in the reservoir placement group (p = 0.65). For the first 6 months after permanent shunt placement, infants with no preceding temporizing procedure had an infection rate of 5% (1 of 20 infants) and those who had undergone a temporizing procedure had an infection rate of 13% (12 of 92; p = 0.45).

Conclusions

The use of intermittent tapping of ventricular reservoirs in this population appears to lead to a lower incidence of permanent shunt placement than the use of VSG shunts. The incidence of infection during temporization and for the initial 6 months after conversion appears comparable for both groups. The apparent difference identified in this pilot study requires confirmation in a more rigorous study.

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Andrew Jea, Ernesto Coscarella, Murali Chintagumpala, Meena Bhattacharjee, William E. Whitehead, Daniel J. Curry and Thomas G. Luerssen

Multiple metastatic brain tumors and multifocal primary brain tumors of a single histological type have been published in the adult and pediatric literature. However, the simultaneous occurrence of multiple primary brain tumors with different cell types is rare. Even more rare is the pediatric presentation of multiple primary brain tumors with different cell types.

The authors describe the case of an 8-year-old boy who presented with a 2-week history of progressive headache, nausea and vomiting, and imbalance. Brain MR imaging demonstrated a heterogeneously enhancing mixed solid/cystic mass of the left cerebellar hemisphere and a larger, midline, more homogeneously enhancing lesion of the superior vermis. Spinal MR imaging was unremarkable.

The patient underwent a suboccipital craniotomy and subsequent gross-total resection of both mass lesions. Pathological examination revealed the left cerebellar and superior vermian lesions to be a juvenile pilocytic astrocytoma and a medulloblastoma, respectively. The patient did well in the immediate postoperative period, was discharged home, and underwent neurooncological follow-up.

To the best of the authors' knowledge, they describe the first known pediatric case in which a medulloblastoma and a juvenile pilocytic astrocytoma presented as synchronous primary brain tumors. They review the literature on multiple primary brain tumors with different histological characteristics and rehash potential mechanisms for their development.

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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, Benjamin D. Fox, Daniel H. Fulkerson, Sasidhar Yallampalli, Anna Illner, William E. Whitehead, Daniel J. Curry, Thomas G. Luerssen and Andrew Jea

Posterior reversible encephalopathy syndrome (PRES) has been described in the setting of malignant hypertension, renal disease, eclampsia, and immunosuppression. In addition, a single case of intraoperative (posterior fossa craniotomy) PRES has been reported; however, this case occurred in an adult.

The authors present a clinically and radiographically documented case of intraoperative PRES complicating the resection of a posterior fossa tumor in a 6-year-old child. During tumor resection, untoward force was used to circumferentially dissect the tumor, and excessive manipulation of the brainstem led to severe hypertension for a 10-minute period. An immediate postoperative MR image was obtained to rule out residual tumor, but instead the image showed findings consistent with PRES. Moreover, the patient's postoperative clinical findings were consistent with PRES.

Aggressive postoperative management of blood pressure and the institution of anticonvulsant therapy were undertaken. The patient made a good recovery; however, he required a temporary tracheostomy and tube feedings for prolonged lower cranial nerve dysfunction.

Posterior reversible encephalopathy syndrome can occur as a result of severe hypertension during surgery, even among young children. With prompt treatment, the patient in the featured case experienced significant clinical and radiographic recovery.