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Vincent Y. Wang, Edward F. Chang and Nicholas M. Barbaro

Focal cortical dysplasia (FCD) is found in approximately one-half of patients with medically refractory epilepsy. These lesions may involve only mild disorganization of the cortex, but they may also contain abnormal neuronal elements such as balloon cells. Advances in neuroimaging have allowed better identification of these lesions, and thus more patients have become surgical candidates. Molecular biology techniques have been used to explore the genetics and pathophysiological characteristics of FCD. Data from surgical series have shown that surgery often results in significant reduction or cessation of seizures, especially if the entire lesion is resected.

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Henry E. Aryan, C. Benjamin Newman, Eric W. Nottmeier, Frank L. Acosta Jr., Vincent Y. Wang and Christopher P. Ames

Object

Stabilization of the atlantoaxial complex has proven to be very challenging. Because of the high mobility of the C1–2 motion segment, fusion rates at this level have been substantially lower than those at the subaxial spine. The set of potential surgical interventions is limited by the anatomy of this region. In 2001 Jürgen Harms described a novel technique for individual fixation of the C-1 lateral mass and the C-2 pedicle by using polyaxial screws and rods. This method has been shown to confer excellent stability in biomechanical studies. Cadaveric and radiographic analyses have indicated that it is safe with respect to osseous and vascular anatomy. Clinical outcome studies and fusion rates have been limited to small case series thus far. The authors reviewed the multicenter experience with 102 patients undergoing C1–2 fusion via the polyaxial screw/rod technique. They also describe a modification to the Harms technique.

Methods

One hundred two patients (60 female and 42 male) with an average age of 62 years were included in this analysis. The average follow-up was 16.4 months. Indications for surgery were instability at the C1–2 level, and a chronic Type II odontoid fracture was the most frequent underlying cause. All patients had evidence of instability on flexion and extension studies. All underwent posterior C-1 lateral mass to C-2 pedicle or pars screw fixation, according to the method of Harms. Thirty-nine patients also underwent distraction and placement of an allograft spacer into the C1–2 joint, the authors' modification of the Harms technique. None of the patients had supplemental sublaminar wiring.

Results

All but 2 patients with at least a 12-month follow-up had radiographic evidence of fusion or lack of motion on flexion and extension films. All patients with an allograft spacer demonstrated bridging bone across the joint space on plain x-ray films and computed tomography. The C-2 root was sacrificed bilaterally in all patients. A postoperative wound infection developed in 4 patients and was treated conservatively with antibiotics and local wound care. One patient required surgical debridement of the wound. No patient suffered a neurological injury. Unfavorable anatomy precluded the use of C-2 pedicle screws in 23 patients, and thus, they underwent placement of pars screws instead.

Conclusions

Fusion of C1–2 according to the Harms technique is a safe and effective treatment modality. It is suitable for a wide variety of fracture patterns, congenital abnormalities, or other causes of atlantoaxial instability. Modification of the Harms technique with distraction and placement of an allograft spacer in the joint space may restore C1–2 height and enhance radiographic detection of fusion by demonstrating a graft–bone interface on plain x-ray films, which is easier to visualize than the C1–2 joint.

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Vincent Y. Wang, Henry Aryan and Christopher P. Ames

✓The incidence rate of kyphosis of the cervical spine after a laminectomy can be as high as 20% after a multilevel laminectomy. The loss of the posterior tension band leads to increased load on the vertebral body and discs, leading to further degenerative changes and kyphotic deformities. The initial decompression of the spinal cord disappears as the cord is stretched over the anterior lesions. Muscle damage and facet degeneration from prior surgery contribute to additional pain, muscle spasm, and motion. Occasionally prior surgical fusion that fails to address the kyphosis or spontaneous fusion in a kyphotic position (observed more in laminectomies performed in the growing spine) can result in a challenging rigid deformity with anterior vertebral body and lateral mass facet fusion. For this fixed deformity, anterior and posterior release are often necessary for restoration of lordosis, which can result in the need for a 540° procedure. In this report the authors describe an anterior technique for simultaneous anterior and posterior lateral mass release. The vertebral artery is mobilized using this technique, allowing for its lateral retraction. The nerve roots are visualized and retracted superiorly and inferiorly. The lateral mass and facets can then be accessed anteriorly using an osteotome or drill for the release. The authors illustrate this technique in a patient who developed fixed scoliosis and kyphosis of the cervical spine after surgery for degenerative disc disease. To the authors' knowledge, this is the first report of this technique.

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Vincent Y. Wang, Adam S. Kanter and Praveen V. Mummaneni

✓Ossified ligamentum flavum (OLF) in the thoracic spine is a rare cause of myelopathy, often presenting with progressive symptomatology over an extended period of time. Surgical decompression via wide laminectomy has been the mainstay of treatment for this symptomatic disease phenomenon, but complications such as kyphotic deformity have developed due to extensive bone removal and release of the posterior tension band. The authors present a case of OLF excised via a minimally invasive microsurgical approach in which an expandable tubular retractor system was used. This approach enables complete decompression of the spinal canal while minimizing nerve, vascular, and musculoskeletal disruption, thus maintaining the native biomechanical disposition of the intact vertebral column.

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Dean Chou and Vincent Y. Wang

Lateral extracavitary and costotransversectomy approaches have been well described, and they are useful for posterior thoracic corpectomies. However, these approaches require pleural dissection and are associated with welldocumented morbidities, including hemothorax, pneumothorax, and pneumonia. But without removing the rib head, the window through which an expandable cage can be placed from a posterior approach is narrow. Thus, smaller nonexpandable mesh cages or methylmethacrylate constructs are commonly used for anterior column reconstruction. The authors describe a technique of using a “trap-door” rib-head osteotomy that avoids pleural dissection, yet allows a large expandable cage to be placed from an entirely posterior approach.

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Christopher P. Ames, Vincent Y. Wang, Vedat Deviren and Frank D. Vrionis

Management of metastatic disease is a significant challenge in modern spinal surgery. Previously, radiation therapy alone was the most commonly employed treatment. Recent data, however, suggest that surgical decompression in addition to radiation therapy improves functional recovery compared with radiation therapy alone.

Metastatic disease most commonly affects the thoracic spine. Over the past decade surgical treatment has changed significantly for thoracic disease, shifting from transthoracic resection and reconstruction to single-stage posterolateral approaches that allow transpedicular resection and reconstruction. In posterolateral approaches, patients are spared the morbidity associated with transcavitary approaches while receiving the benefit of radical resection and circumferential reconstruction in a single-stage procedure.

The authors report 3 cases in which a similar posterior transpedicular technique, adapted for the cervical spine, was used for intralesional resection of metastatic tumors of the axis.

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Vincent Y. Wang, Vedat Deviren and Christopher P. Ames

Aneurysmal bone cysts (ABCs) are rare benign tumors with a prevalence of 0.14 cases per 100,000 people. A majority of cases arise during adolescence, and there is a female predominance. This lesion accounts for 1.4% of all primary bone tumors. Aneurysmal bone cysts occur mainly in the long bones, with spinal involvement in 10–30% of cases. Cervical spine ABCs account for about one-third of spinal ABCs, and atlas involvement occurs in 1% of cases. Resection of ABCs at the atlas is difficult because of the location and the lack of proper instrumentation for reconstruction of C-1. The authors present a case of an ABC at C-1 in a child who underwent resection of the lesion and reconstruction of the lateral mass with a titanium mesh cage.

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Ricardo B. V. Fontes and Vincent C. Traynelis