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Daniel K. Resnick, Christopher H. Comey, William C. Welch, A. Julio Martinez, William W. Hoover and George B. Jacobs

✓ Toxoplasmosis and lymphoma are the two most common causes of intraparenchymal cerebral mass lesions in patients with acquired immunodeficiency syndrome (AIDS). The clinical and radiographic features of the intracranial lesions have been well described. Because of the high frequency of toxoplasmosis in the AIDS population, common therapy for patients presenting with intracranial mass lesions consists of an empirical trial of anti-Toxoplasma chemotherapy, with biopsy reserved for cases demonstrating features considered to be more consistent with lymphoma, or for lesions that do not improve despite adequate anti-Toxoplasma treatment. A similar treatment algorithm does not exist for intramedullary lesions of the spinal cord.

The authors describe a patient who presented with paraparesis resulting from an isolated thoracic intramedullary lesion. An open biopsy of the lesion revealed characteristic structures containing Toxoplasma tachyzoites. The clinical and radiographic presentation of the lesion is discussed, the available literature is reviewed, and a treatment strategy for spinal cord lesions in AIDS patients is proposed.

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Gregory J. Przybylski and William C. Welch

✓ Odontoid fractures are a common traumatic upper cervical spine injury. Treatment of Type III odontoid fractures includes skeletal traction for realignment and halo vest immobilization. The authors report an unusual case of severe atlantoaxial ligamentous disruption accompanying a traumatic Type III odontoid fracture. Five pounds of skeletal traction was associated with marked neurological deterioration from unanticipated longitudinal instability. Radiographic findings were identified that were suggestive of extensive ligamentous disruption. Recommendations for individualized patient management are given in the context of related literature.

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William C. Welch, Robert D. Rose, Jeffrey R. Balzer and George B. Jacobs

✓ The neuroanatomical structures that approximate the bony pedicles of the lumbar spine allow little room for technical error or compromise of the bone during pedicle screw insertion. Currently available neurophysiological monitoring techniques detect compromised bone and nerve root injury after it occurs. The purpose of this prospective study is to evaluate the reliability and efficacy of a unique neurophysiological monitoring technique. This technique provides immediate evaluation of pedicle cortical bone integrity in patients undergoing lumbar fusion with instrumentation by using electrified surgical instruments throughout the pedicle screw fusion procedure. Spontaneous electromyographic (EMG) activity was also monitored.

Intraoperative evoked EMG stimulation was performed using a pedicle probe and feeler as monopolar stimulators during the insertion of 164 pedicle bone screws in 32 patients. The EMG response to subthreshold stimulation intensities indicated cortical bone compromise. Immediate and conclusive feedback via evoked EMG activity using stimulating pedicle probes in appropriate muscle groups was successful in identifying pedicle cortical bone compromise in four patients. One false-negative evoked EMG study was noted but was identified via spontaneous EMG activity. Intraoperative EMG monitoring alerted the surgeon that redirection of the pedicle probe or screw was necessary to avoid nerve root irritation or injury and served as an early warning system.

Evoked EMG stimulation proved to be reliable and efficacious, especially when used in combination with spontaneous EMG. This technique may provide an added safeguard during implant placement procedures at centers where intraoperative neurophysiological monitoring is routinely performed.

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William C. Welch and Peter C. Gerszten

In recent years the general trend in spinal surgery has been one of reductionism and minimalization. A number of techniques have recently been developed that are applicable in the treatment of lumbar disc herniation and discogenic pain due to degenerative disc disease. The purpose of this manuscript is to examine two newer percutaneous disc treatment techniques, intradiscal electrothermal therapy (IDET) anuloplasty and nucleoplasty. The authors review the appropriate clinical treatment criteria, techniques, and lessons learned after performing these procedures in more than 100 patients.

The IDET involves the percutaneous insertion of a specially designed thermal resistance probe followed by controlled heating of the intervertebral disc. This may result in disc shrinkage and reduction in pain. The nucleoplasty procedure involves the percutaneous removal of disc material by using a low-temperature resister probe to disintegrate and evacuate disc material, followed by thermal treatment of adjacent residual disc material. To date, no study has been published in which investigators examine the outcomes of this procedure for the treatment of radicular leg pain and low-back pain.

Both IDET and nucleoplasty appear to be safe procedures. The IDET procedure may be an alternative to lumbar interbody fusion. Although its long-term role is being defined, this technique appears to provide intermediate-term relief of pain in a population of patients with discogenic low-back pain. Nucleoplasty may provide a percutaneous alternative to microdiscectomy in selected cases.

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Peter C. Gerszten, Cihat Ozhasoglu, Steven A. Burton, Shalom Kalnicki and William C. Welch

Object

The role of stereotactic radiosurgery for the treatment of intracranial lesions is well established. Its use for the treatment of spinal lesions has been limited by the availability of effective target-immobilizing devices. In this study the authors evaluated the CyberKnife Real-Time Image-Guided Radiosurgery System for spinal lesion treatment involving a single-fraction radiosurgical technique.

Methods

This frameless image-guided radiosurgery system uses the coupling of an orthogonal pair of x-ray cameras to a dynamically manipulated robot-mounted linear accelerator possessing six degrees of freedom, which guides the therapy beam to the target without the use of frame-based fixation. Cervical lesions were located and tracked relative to osseous skull landmarks; lower spinal lesions were tracked relative to percutaneously placed gold fiducial bone markers. Fifty-six spinal lesions in 46 consecutive patients were treated using single-fraction radiosurgery (26 cervical, 15 thoracic, and 11 lumbar, and four sacral). There were 11 benign and 45 metastatic lesions.

Tumor volume ranged from 0.3 to 168 ml (mean 26.7 ml). Thirty-one lesions had previously received external-beam radiotherapy with maximum spinal cord doses. Dose plans were calculated based on computerized tomography scans acquired using 1.25-mm slices. Tumor dose was maintained at 12 to 18 Gy to the 80% isodose line; spinal cord lesions receiving greater than 8 Gy ranged from 0 to 1.3 ml (mean 0.3 ml). All patients tolerated the procedure in an outpatient setting. No acute radiation-induced toxicity or new neurological deficits occurred during the follow-up period. Axial and radicular pain improved in all patients who were symptomatic prior to treatment.

Conclusions

Spinal stereotactic radiosurgery involving a frameless image-guided system was found to be feasible and safe. The major potential benefits of radiosurgical ablation of spinal lesions are short treatment time in an outpatient setting with rapid recovery and symptomatic response. This procedure offers a successful alternative therapeutic modality for the treatment of a variety of spinal lesions not amenable to open surgical techniques; the intervention can be performed in medically untreatable patients, lesions located in previously irradiated sites, or as an adjunct to surgery.

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William C. Welch, Kevin A. Thomas, G. Bryan Cornwall, Peter C. Gerszten, Jeffrey M. Toth, Edwin M. Nemoto and A. Simon Turner

Object. The present investigation evaluates two thicknesses of a resorbable polylactic acid (PLA) barrier film as an adhesion barrier to posterior spinal scar formation.

Methods. A readily contourable, thin film was placed directly over the dura. The thick film was placed above the lamina defect to act as a physical barrier inhibiting the prolapse of soft tissue into the epidural space. Through a combination of gross dissection with and without scar scores, quantitative analysis of collagen adjacent to the scar site, and histological evaluation, the resorbable adhesion barrier membranes were found to be effective treatment for reduction of posterior adhesions.

Conclusions. The gross dissection demonstrated that both thicknesses of resorbable PLA barrier films created a controlled dissection plane, facilitated access to the epidural space, and provided a reduction in the tissue adherent to the dura.

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Peter C. Gerszten, Cihat Ozhasoglu, Steven A. Burton, William J. Vogel, Barbara A. Atkins, Shalom Kalnicki and William C. Welch

Object

The role of stereotactic radiosurgery in the treatment of benign intracranial lesions is well established. Its role in the treatment of benign spinal lesions is more limited. Benign spinal lesions should be amenable to radiosurgical treatment similar to their intracranial counterparts. In this study the authors evaluated the effectiveness of the CyberKnife for benign spinal lesions involving a single-fraction radiosurgical technique.

Methods

The CyberKnife is a frameless radiosurgery system in which an orthogonal pair of x-ray cameras is coupled to a dynamically manipulated robot-mounted linear accelerator possessing six degrees of freedom, whereby the therapy beam is guided to the intended target without the use of frame-based fixation. Cervical spine lesions were located and tracked relative to skull osseous landmarks; lower spinal lesions were tracked relative to percutaneously placed fiducial bone markers. Fifteen patients underwent single-fraction radiosurgery (12 cervical, one thoracic, and two lumbar). Histological types included neurofibroma (five cases), paraganglioma (three cases), schwannoma (two cases), meningioma (two cases), spinal chordoma (two cases), and hemangioma (one case).

Radiation dose plans were calculated based on computerized tomography scans acquired using 1.25-mm slices. Planning treatment volume was defined as the radiographic tumor volume with no margin. The tumor dose was maintained at 12 to 20 Gy to the 80% isodose line (mean 16 Gy). Tumor volume ranged from 0.3 to 29.3 ml (mean 6.4 ml). Spinal canal volume receiving more than 8 Gy ranged from 0.0 to 0.9 ml (mean 0.2 ml). All patients tolerated the procedure in an outpatient setting. No acute radiation-induced toxicity or new neurological deficits occurred during the follow-up period. Pain improved in all patients who were symptomatic prior to treatment. No tumor progression has been documented on follow-up imaging (mean 12 months).

Conclusions

Spinal stereotactic radiosurgery was found to be feasible, safe, and effective for the treatment of benign spinal lesions. Its major potential benefits are the relatively short treatment time in an outpatient setting and the minimal risk of side effects. This new technique offers an alternative therapeutic modality for the treatment of a variety of benign spinal neoplasms in cases in which surgery cannot be performed, in cases with previously irradiated sites, and in cases involving lesions not amenable to open surgical techniques or as an adjunct to surgery.

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Peter C. Gerszten, Cihat Ozhasoglu, Steven A. Burton, William C. Welch, William J. Vogel, Barbara A. Atkins and Shalom Kalnicki

Object

The role of stereotactic radiosurgery for the treatment of intracranial lesions is well established. The experience with radiosurgery for the treatment of spinal and sacral lesions is more limited. Sacral lesions should be amenable to radiosurgical treatment similar to that used for their intracranial counterparts. The authors evaluated a single-fraction radiosurgical technique performed using the CyberKnife Real-Time Image-Guided Radiosurgery System for the treatment of the sacral lesion.

Methods

The CyberKnife is a frameless radiosurgery system based on the coupling of an orthogonal pair of x-ray cameras to a dynamically manipulated robot-mounted linear accelerator possessing six degrees of freedom, which guides the therapy beam to the intended target without the need for frame-based fixation. All sacral lesions were located and tracked for radiation delivery relative to fiducial bone markers placed percutaneously. Eighteen patients were treated with single-fraction radiosurgery. Tumor histology included one benign and 17 malignant tumors.

Dose plans were calculated based on computerized tomography scans acquired using 1.25-mm slices. Planning treatment volume was defined as the radiographically documented tumor volume with no margin. Tumor dose was maintained at 12 to 20 Gy to the 80% isodose line (mean 15 Gy). Tumor volume ranged from 23.6 to 187.4 ml (mean 90 ml). The volume of the cauda equina receiving greater than 8 Gy ranged from 0 to 1 ml (mean 0.1 ml). All patients underwent the procedure in an outpatient setting. No acute radiation toxicity or new neurological deficits occurred during the mean follow-up period of 6 months. Pain improved in all 13 patients who were symptomatic prior to treatment. No tumor progression has been documented on follow-up imaging.

Conclusions

Stereotactic radiosurgery was found to be feasible, safe, and effective for the treatment of both benign and malignant sacral lesions. The major potential benefits of radiosurgical ablation of sacral lesions are relatively short treatment time in an outpatient setting and minimal or no side effects. This new technique offers a new and important therapeutic modality for the primary treatment of a variety of sacral tumors or for lesions not amenable to open surgical techniques.

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Peter C. Gerszten, John J. Moossy, John C. Flickinger and William C. Welch

Object. The authors of clinical studies have demonstrated a significant association between the presence of extensive post—lumbar discectomy peridural scar formation and the recurrence of low-back and radicular pain. Low-dose perioperative radiotherapy has been demonstrated to inhibit peridural fibrosis after laminectomy in animal models. The present study was designed to evaluate the clinical efficacy of preoperative irradiation in patients with failed—back surgery syndrome due to peridural fibrosis who underwent reexploration and nerve root decompression.

Methods. Ten patients with symptomatic post—discectomy peridural fibrosis were randomized. Half of the patients underwent 700-cGy external-beam irradiation to the operative site 24 hours prior to reexploration and decompressive treatment of their symptomatic nerve root(s) (treatment group) and the other half underwent reexploration and decompressive treatment without preoperative irradiation (control group). All patients underwent simulated irradiation so neither patient nor surgeon was aware of the patient's group. In all patients the antiadhesion product ADCON-L was placed over the affected nerve root at the time of surgery. Clinical outcome was assessed using the American Association of Neurological Surgeons/Congress of Neurological Surgeons Joint Section Lumbar Disc Herniation Study Questionnaire at baseline, 6 weeks, 3 months, and 1 year follow up.

Five men and five women (mean age 42 years) underwent randomization and surgery. Three patients underwent reexploration at L4–5, four at L5—S1, and three at both levels. No complication was associated with irradiation, and no new neurological deficits occurred. At 1-year follow-up examination, three irradiation-treated patients were pain free and two experienced improvement. In the control group, three patients experienced improved pain relief and two were unchanged. There was a trend toward better outcome at 1 year in the radiotherapy-treated group (p = 0.056).

Conclusions. Preoperative low-dose external-beam irradiation improved clinical outcomes after reexploration and decompression of nerve roots affected by postlaminectomy peridural fibrosis causing radicular pain. The addition of preoperative irradiation may improve outcome in patients who undergo reoperation for recurrent radicular pain associated with a significant amount of peridural fibrosis, particularly now that no antiadhesion product is available for clinical use.

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Timothy C. Ryken, Kurt M. Eichholz, Peter C. Gerszten, William C. Welch, Ziya L. Gokaslan and Daniel K. Resnick

Object

Significant controversy exists over the most appropriate treatment for patients with metastatic disease of the vertebral column. Treatment options include surgical intervention, radiotherapy, or a combination of the two; nevertheless, a standard of care that yields the best survival, outcome, and quality of life has not been established. The purpose of this review was to determine the foundation in the literature of views favoring surgical intervention for spinal metastatic disease.

Methods

A search of the English-language literature published between 1964 and 2003 was performed for the subject of spinal metastatic disease. Papers were selected based on the inclusion criteria described, and evidentiary information was compiled and graded using previously described methods.

Conclusions

Although there is insufficient evidence to support a standard for surgical treatment in patients with metastatic spinal disease, the authors present guidelines and recommendations based on the evidence provided by the current literature.