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Marcus D. Mazur and Andrew T. Dailey

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Gregory F. Jost and Andrew T. Dailey

Rotational occlusion of the vertebral artery (VA), or bow hunter’s syndrome, is a rare yet surgically treatable cause of vertebrobasilar insufficiency. The underlying pathology is dynamic stenosis of the VA by osteophytes, fibrous bands, or lateral disc herniation with neck rotation or extension. The authors present 2 previously unreported cases of bow hunter’s syndrome and summarize 124 cases identified in a literature review.

Both patients in the new cases were treated by VA decompression and fusion of the subaxial spine. Each had > 50% occlusion of the left VA at the point of entry into the transverse foramen with a contralateral VA that ended in the posterior inferior cerebellar artery. Analyzing data from 126 cases (the 2 new cases in addition to the previously published 124), the authors report that stenosis was noted within V1 in 4% of cases, in V2 in 58%, in V3 in 36%, and distal to C-1 in 2%. Patients presented in the 5th to 7th decade of life and were more often male than female. The stenotic area was decompressed in 85 (73%) of the 116 patients for whom the type of treatment was reported (V1, 4 [80%] of 5; V2, 52 [83%] of 63; V3/V4, 29 [60%] of 48). Less commonly, fusion or combined decompression and fusion was used (V2, 7 [11%] of 63; V3/V4, 14 [29%] of 48). Most patients reported complete resolution of symptoms.

The authors conclude that patients with bow hunter’s syndrome classically have an impaired collateral blood flow to the brainstem. This condition carries an excellent prognosis with decompression, fusion, or combined surgery, and individual patient characteristics should guide the choice of therapy.

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Frank S. Bishop, Andrew T. Dailey and Meic H. Schmidt

Charcot spinal disease is a destructive degenerative process involving the vertebrae and surrounding discs, resulting from repetitive microtrauma in patients who have decreased joint protective mechanisms due to loss of deep pain and proprioceptive sensation. The typical presentation of the disease is back pain and progressive spinal instability and deformity. The authors report an unusual case of massive Charcot spinal disease deformity in a patient presenting with increasing abdominal girth and discomfort.

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David W. Newell, Andrew T. Dailey and Stephen L. Skirboll

✓ The authors describe the use of a microanastomotic device to perform intracranial end-to-end vascular anastomoses. Direct end-to-end anastomosis was performed between the superficial temporal artery and branches of the middle cerebral artery (MCA) in three patients. Two patients had moyamoya disease, with severe proximal MCA disease, and one suffered an internal carotid artery occlusion with poor collateral flow. All patients reported a history of recent ischemic symptoms. Each anastomosis was accomplished in less than 15 minutes with technically satisfactory results. Postoperative angiographic studies demonstrated patency of the bypasses in all patients.

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Andrew T. Dailey, Guy M. McKhann II and Mitchel S. Berger

✓ Mutism following posterior fossa tumor resection in pediatric patients has been previously recognized, although its pathophysiology remains unclear. A review of the available literature reveals 33 individuals with this condition, with only a few adults documented in the population. All of these patients had large midline posterior fossa tumors.

To better understand the incidence and anatomical substrate of this syndrome, the authors reviewed a 7-year series of 110 children who underwent a posterior fossa tumor resection. During that time, nine (8.2%) of the 110 children exhibited mutism postoperatively. They ranged from 2.5 to 20 years of age (mean 8.1 years) and became mute within 12 to 48 hours of surgery. The period of mutism lasted from 1.5 to 12 weeks after onset: all children had difficulty coordinating their oral pharyngeal musculature as manifested by postoperative drooling and inability to swallow. Further analysis of these cases revealed that all children had splitting of the entire inferior vermis at surgery, as confirmed on postoperative magnetic resonance studies. Lower cranial nerve function was intact in all nine patients.

Current concepts of cerebellar physiology emphasize the importance of the cerebellum in learning and language. The syndrome described resembles a loss of learned activities, or an apraxia, of the oral and pharyngeal musculature. To avoid the apraxia, therefore, the inferior vermis must be preserved. For large midline tumors that extend to the aqueduct, a combined approach through the fourth ventricle and a midvermis split may be used to avoid injuring the inferior vermis.

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Ganesh Rao, Darrel S. Brodke, Matthew Rondina and Andrew T. Dailey

Object. To validate computerized tomography (CT) scanning as a tool to assess the accuracy of thoracic pedicle screw placement, the authors compared its accuracy with that of direct visualization in instrumented cadaveric spine specimens.

Methods. A grading scale was devised to score the placement of the pedicle screw. The grades ranged from 0 to 3 depending on the extent to which the pedicle had been violated. One hundred fifty-five pedicles were fitted with instrumentation in eight cadaveric spines. A single observer graded the appearance of the screw based on CT scans (3-mm axial sections with 1-mm overlap) and direct visualization of the specimen. The authors arrived at a Kappa value of 0.51, which suggested only moderate agreement between the two measurement techniques. Whereas CT had a positive predictive value of 95%, it had a negative predictive value of 62%.

Conclusions. The authors thus conclude that although CT scanning is the most valid tool to assess the accuracy of thoracic pedicle screw placement, it tends to overestimate the number of misplaced screws.

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Christian Bowers, Amin Amini, Andrew T. Dailey and Meic H. Schmidt

Object

The X-Stop interspinous device is designed for the treatment of patients with neurogenic intermittent claudication due to lumbar spinal stenosis. It distracts the posterior elements of adjacent vertebral bodies, unloading the intervertebral disc, limiting spinal extension, and improving central canal and neuroforaminal stenosis. In this paper, the authors reviewed the complications and failure/reoperation rates in a small series of patients and compared their results with other reported complication and failure/reoperation rates.

Methods

The medical records of all patients who underwent placement of the X-Stop device for the treatment of NIC at the authors' institution were retrospectively evaluated, and demographic information, diagnosis, and preoperative pain levels were recorded. Postoperatively, patients subjectively graded the percentage (0–100%) of improvement in pain as well as the amount of residual pain and underwent imaging at 1-, 3-, and 6-month intervals. Approximately 4 years after X-Stop placement, information on long-term outcomes was obtained from patient medical records or additional follow-up.

Results

Thirteen patients (8 men and 5 women) underwent placement of the X-Stop device. Central canal stenosis with bilateral foraminal stenosis was diagnosed in all patients: 9 (69%) of 13 had severe stenosis and 4 (31%) of 13 had moderate stenosis. Five patients (38%) also had associated Grade I spondylolisthesis. Nine patients underwent placement of the X-Stop device at the L4–5 interspinous space and 4 at both the L3–4 and L4–5 levels. The average duration of follow-up was 42.9 months (range 3–48 months). Initially, pain improved an average of 72% (range 50–100%) in these patients; however, preoperative pain returned in 77% of the patients (10 of 13). The overall complication rate was 38%, including 3 spinous process fractures (23%) and 2 instances of new-onset radiculopathy (15%). The ultimate failure rate requiring additional spinal surgery was 85% (11 of 13 patients). These complication and failure rates are much higher than those previously reported.

Conclusions

Overdistraction, poor bone density, poor patient selection, and preexistent adjacent foraminal stenosis may all be factors in the development of the aforementioned complications. Thus, careful attention should be paid preoperatively to adjacent-level disease, bone density, appropriate implant size, and optimal patient selection.

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Tobias A. Mattei and Daniel R. Fassett

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Wilson Z. Ray, Vijay M. Ravindra, Meic H. Schmidt and Andrew T. Dailey

Object

Pelvic fixation is a crucial adjunct to many lumbar fusions to avoid L5–S1 pseudarthrosis. It is useful for treatment of kyphoscoliosis, high-grade spondylolisthesis, L5–S1 pseudarthrosis, sacral tumors, lumbosacral dislocations, and osteomyelitis. The most popular method, iliac fixation, has drawbacks including hardware prominence, extensive muscle dissection, and the need for connection devices. S-2 alar iliac fixation provides a useful primary or salvage alternative. The authors describe their techniques for using stereotactic navigation for screw placement.

Methods

The O-arm Surgical Imaging System allowed for CT-quality multiplanar reconstructions of the pelvis, and registration to a StealthStation Treon provided intraoperative guidance. The authors describe their technique for performing computer-assisted S-2 alar iliac fixation for various indications in 18 patients during an 18-month period.

Results

All patients underwent successful bilateral placement of screws 80–100 mm in length. All placements were confirmed with a second multiplanar reconstruction. One screw was moved because of apparent anterior breach of the ilium. There were no immediate neurological or vascular complications due to screw placement. The screw length required additional instruments including a longer pedicle finder and tap.

Conclusions

Stereotactic guidance to navigate the placement of distal pelvic fixation with bilateral S-2 alar iliac fixation can be safely performed in patients with a variety of pathological conditions. Crossing the sacroiliac joint, choosing trajectory, and ensuring adequate screw length can all be enhanced with 3D image guidance. Long-term outcome studies are underway, specifically evaluating the sacroiliac joint.

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Michael Y. Wang, Enrico Tessitore, Neil Berrington and Andrew Dailey