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John C. Liu, Joseph D. Ciacci and Timothy M. George

✓ Treatment of the Dandy—Walker syndrome has included placement of a ventriculoperitoneal shunt alone or in combination with a posterior fossa cystoperitoneal shunt. Complications in shunting are common and are usually related to malfunction or infection. The authors present a case in which the patient developed headaches and focal cranial nerve deficits following infection caused by a cystoperitoneal shunt. Magnetic resonance imaging showed tethering of the brainstem. A posterior fossa craniotomy with microsurgical untethering and cyst fenestration achieved two goals: improvement of the focal cranial nerve deficits and elimination of the cystoperitoneal shunt.

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Patrick C. Hsieh, John C. Liu and Michael Y. Wang

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Aaron E. Bond, John A. Jane Sr., Kenneth C. Liu and Edward H. Oldfield

OBJECT

The authors completed a prospective, institutional review board–approved study using intraoperative MRI (iMRI) in patients undergoing posterior fossa decompression (PFD) for Chiari I malformation. The purpose of the study was to examine the utility of iMRI in determining when an adequate decompression had been performed.

METHODS

Patients with symptomatic Chiari I malformations with imaging findings of obstruction of the CSF space at the foramen magnum, with or without syringomyelia, were considered candidates for surgery. All patients underwent complete T1, T2, and cine MRI studies in the supine position preoperatively as a baseline. After the patient was placed prone with the neck flexed in position for surgery, iMRI was performed. The patient then underwent a bone decompression of the foramen magnum and arch of C-1, and the MRI was repeated. If obstruction was still present, then in a stepwise fashion the patient underwent dural splitting, duraplasty, and coagulation of the tonsils, with an iMRI study performed after each step guiding the decision to proceed further.

RESULTS

Eighteen patients underwent PFD for Chiari I malformations between November 2011 and February 2013; 15 prone preincision iMRIs were performed. Fourteen of these patients (93%) demonstrated significant improvement of CSF flow through the foramen magnum dorsal to the tonsils with positioning only. This improvement was so notable that changes in CSF flow as a result of the bone decompression were difficult to discern.

CONCLUSIONS

The authors observed significant CSF flow changes when simply positioning the patient for surgery. These results put into question intraoperative flow assessments that suggest adequate decompression by PFD, whether by iMRI or intraoperative ultrasound. The use of intraoperative imaging during PFD for Chiari I malformation, whether by ultrasound or iMRI, is limited by CSF flow dynamics across the foramen magnum that change significantly when the patient is positioned for surgery.

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Brian A. O'Shaughnessy, Sean A. Salehi, Saad Ali and John C. Liu

✓ Chiari I malformation, a congenital disorder involving downward displacement of the cerebellar tonsils through the foramen magnum, is often treated surgically by performing suboccipital craniectomy and C-1 laminectomy. The authors report two cases in which fracture of the anterior atlantal arch occurred during the postoperative period following Chiari I decompression and C-1 laminectomy causing significant neck pain. The findings indicate that interruption of the integrity of the posterior arch of C-1, iatrogenically or otherwise, confers increased risk of anterior arch fracture. A C-1 fracture should therefore be considered in the differential diagnosis of posterior cervical pain in patients who have previously undergone decompression for Chiari I malformation.

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Martin H. Pham, Joshua Bakhsheshian, Patrick C. Reid, Ian A. Buchanan, Vance L. Fredrickson and John C. Liu

OBJECTIVE

Freehand placement of C2 instrumentation is technically challenging and has a learning curve due the unique anatomy of the region. This study evaluated the accuracy of C2 pedicle screws placed via the freehand technique by neurosurgical resident trainees.

METHODS

The authors retrospectively reviewed all patients treated at the LAC+USC Medical Center undergoing C2 pedicle screw placement in which the freehand technique was used over a 1-year period, from June 2016 to June 2017; all procedures were performed by neurosurgical residents. Measurements of C2 were obtained from preoperative CT scans, and breach rates were determined from coronal reconstructions on postoperative scans. Severity of breaches reflected the percentage of screw diameter beyond the cortical edge (I = < 25%; II = 26%–50%; III = 51%–75%; IV = 76%–100%).

RESULTS

Neurosurgical residents placed 40 C2 pedicle screws in 24 consecutively treated patients. All screws were placed by or under the guidance of Pham, who is a postgraduate year 7 (PGY-7) neurosurgical resident with attending staff privileges, with a PGY-2 to PGY-4 resident assistant. The authors found an average axial pedicle diameter of 5.8 mm, axial angle of 43.1°, sagittal angle of 23.0°, spinal canal diameter of 25.1 mm, and axial transverse foramen diameter of 5.9 mm. There were 17 screws placed by PGY-2 residents, 7 screws placed by PGY-4 residents, and 16 screws placed by the PGY-7 resident. The average screw length was 26.0 mm, with a screw diameter of 3.5 mm or 4.0 mm. There were 7 total breaches (17.5%), of which 4 were superior (10.0%) and 3 were lateral (7.5%). There were no medial breaches. The breaches were classified as grade I in 3 cases (42.9%), II in 3 cases (42.9%), III in 1 case (14.3%), and IV in no cases. There were 3 breaches that occurred via placement by a PGY-2 resident, 3 breaches by a PGY-4 resident, and 1 breach by the PGY-7 resident. There were no clinical sequelae due to these breaches.

CONCLUSIONS

Freehand placement of C2 pedicle screws can be done safely by neurosurgical residents in early training. When breaches occurred, they tended to be superior in location and related to screw length choice, and no breaches were found to be clinically significant. Controlled exposure to this unique anatomy is especially pertinent in the era of work-hour restrictions.

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Mario J. Cardoso, Tyler R. Koski, Aruna Ganju and John C. Liu

The surgical management of compressive cervical ossification of the posterior longitudinal ligament (OPLL) can be challenging. Traditionally, approach indications for decompression of cervical spondylotic myelopathy have been used. However, the postoperative complication profile after cervical OPLL decompression is unique and may require an alternative approach paradigm. The authors review the literature on approach-related OPLL complications and suggest a management strategy for patients with single- or multiple-segment OPLL with or without greater than 50% canal stenosis.

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Patrick Shih, Ryan J. Halpin, Aruna Ganju, John C. Liu and Tyler R. Koski

Recurrent tethered cord syndrome (TCS) can lead to significant progressive disability in adults. The diagnosis of TCS is made with a high degree of clinical suspicion. In the adult population, many patients receive inadequate care unless they are seen at a multidisciplinary clinic. Successful detethering procedures require careful intradural dissection and meticulous wound and dural closure. With multiple revision procedures, vertebral column shortening has become an appropriate alternative to surgical detethering.

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Jamal McClendon Jr., Patrick A. Sugrue, Aruna Ganju, Tyler R. Koski and John C. Liu

The management of thoracic ossification of the posterior longitudinal ligament has been studied by many spinal surgeons. Indications for operative intervention include progressive radiculopathy, myelopathy, and neurological deterioration. The ideal surgery for decompression remains highly debatable as various methods of surgical treatment of ossification of the posterior longitudinal ligament have been devised. Although numerous modifications to the 3 main approaches have been identified (anterior, posterior, or lateral), the indication for each depends on the nature of compression, the morphology of the lesion, the level of the compression, the structural alignment of the spine, and the neurological status of the patient. The authors discuss treatment techniques for thoracic ossification of the posterior longitudinal ligament, cite case examples from a single institution, and review the literature.

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Doniel Drazin, Miriam Nuño, Chirag G. Patil, Kimberly Yan, John C. Liu and Frank L. Acosta Jr.

OBJECTIVE

The objective of this study was to determine factors associated with admission to the hospital through the emergency room (ER) for patients with a primary diagnosis of low-back pain (LBP). The authors further evaluated the impact of ER admission and patient characteristics on mortality, discharge disposition, and hospital length of stay.

METHODS

The authors conducted a retrospective analysis of patients with LBP discharged from hospitals according to the Nationwide Inpatient Sample (NIS) between 1998 and 2007. Univariate comparisons of patient characteristics according to the type of admission (ER versus non-ER) were conducted. Multivariate analysis evaluated factors associated with an ER admission, risk of mortality, and nonroutine discharge.

RESULTS

According to the NIS, approximately 183,151 patients with a primary diagnosis of LBP were discharged from US hospitals between 1998 and 2007. During this period, an average of 65% of these patients were admitted through the ER, with a significant increase from 1998 (54%) to 2005 (71%). Multivariate analysis revealed that uninsured patients (OR 2.1, 95% CI 1.7–2.6, p < 0.0001) and African American patients (OR 1.5, 95% CI 1.2–1.7, p < 0.0001) were significantly more likely to be admitted through the ER than private insurance patients or Caucasian patients, respectively. Additionally, a moderate but statistically significant increase in the likelihood of ER admission was noted for patients with more preexisting comorbidities (OR 1.1, 95% CI 1.0–1.2, p < 0.001). An 11% incremental increase in the odds of admission through the ER was observed with each year increment (OR 1.1, 95% CI 1.0–1.2, p < 0.001). Highest income patients ($45,000+) were more likely to be admitted through the ER (OR 1.3, 95% CI 1.1–1.6, p = 0.007) than the lowest income cohort. While ER admission did not impact the risk of mortality (OR 0.95, 95% CI 0.60–1.51, p = 0.84), it increased the odds of a nonroutine discharge (OR 1.39, 95% CI 1.26–1.53, p < 0.0001).

CONCLUSIONS

A significant majority of patients discharged from hospitals in the US from 1998 to 2007 with a primary diagnosis of LBP were admitted through the ER, with more patients being admitted via this route each year. These patients were less likely to be discharged directly home compared with patients with LBP who were not admitted through the ER. Uninsured and African American patients with LBP were more likely to be admitted through the ER than their counterparts, as were patients with more preexisting health problems. Interestingly, patients with LBP at the highest income levels were more likely to be admitted through hospital ERs. The findings suggest that socioeconomic factors may play a role in the utilization of ER resources by patients with LBP, which in turn appears to impact at least the short-term outcome of these patients.

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John K. Stokes, Alan T. Villavicencio, Paul C. Liu, Robert S. Bray and J. Patrick Johnson

Object

Surgical treatment of atlantoaxial instability has evolved to include various posterior wiring techniques including Brooks, Gallie, and Sonntag fusions in which success rates range from 60 to 100%. The Magerl–Seemans technique in which C1–2 transarticular screws are placed results in fusion rates between 87 and 100%. This procedure is technically demanding and requires precise knowledge of the course of the vertebral arteries (VAs). The authors introduce a new C1–2 fixation procedure in which C-1 lateral mass and C-2 pedicle screws are placed that may have advantages over C1–2 transarticular screw constructs.

Methods

A standard posterior C1–2 exposure is obtained. Polyaxial C-2 pedicle screws and C-1 lateral mass screws are placed bilaterally. Rods are connected to the screws and secured using locking nuts. A cross-link is then placed. Fusion can be performed at the atlantoaxial joint by elevating the C-2 nerve root.

The technique for this procedure has been used in four cases of atlantoaxial instability at the author's institution. There have been no C-2 nerve root– or VA-related injuries. No cases of construct failure have been observed in the short-term follow up period.

Conclusions

Atlantoaxial lateral mass and axial pedicle screw fixation offers an alternative means of achieving atlantoaxial fusion. The technique is less demanding than that required for transarticular screw placement and may avoid the potential complication of VA injury. The cross-linked construct is theoretically stable in flexion, extension, and rotation. Laminectomy or fracture of the posterior elements does not preclude use of this fixation procedure.