Anterior Fixation of Floating Facet Fractures in the Cervical Spine: A Prospective Case Series and Biomechanical Analysis.

BACKGROUND: Unilateral fractures involving complete separation of the lateral mass from the vertebra and lamina (floating lateral mass fractures) are a unique subset of cervical spine fractures. These injuries are at significant risk for displacement without operative fixation. Posterior fixation has proven to facilitate adequate fusion. However, there are few data supporting the clinical success of single-level anterior fixation. METHODS: Biomechanical evaluation of floating lateral mass fractures and a consecutive case series of patients with rotationally unstable floating lateral mass fractures treated with anterior fixation using an integrated cage-screw device with anterior plating (ICSD) was performed. The study comprised 7 fresh human cadaver cervical spines (C2-C7), and 11 patients with floating lateral mass fractures. Segmental flexibility testing evaluating axial rotation, flexion/extension, and lateral bending was performed in a cadaveric model after 2 types of single-level anterior fixation and 1 type of 2-level posterior fixation. Eleven patients with a floating lateral mass fracture of the cervical spine underwent anterior fixation with an ICSD. Radiographs and clinical outcomes were retrospectively reviewed. RESULTS: Compared with the intact condition, posterior instrumentation significantly (P < .05) reduced range of motion (ROM) in all 3 planes; anterior fixation with cervical plate and interbody spacer significantly reduced ROM in lateral bending only; and the ICSD significantly reduced ROM in flexion/extension and lateral bending. In the clinical arm, there were no long-term complications, subsidence >2 mm, failure of fixation, reoperation, pseudoarthrosis, or listhesis at final follow-up. CONCLUSIONS: The addition of 2 screws placed through a cervical cage can improve anterior fixation in a human cadaveric model of floating lateral mass fractures. Early clinical results demonstrate a low complication rate and a high rate of healing with single-level anterior fixation using this technique.

The effect of spinal osteotomies on spinal cord tension and dural buckling: a cadaveric study.

OBJECT: The standard surgical release of a tethered cord may result in recurrent scar formation and occasionally be associated with retethering. The application of spinal shortening procedures to this challenging problem potentially can reduce tension on the retethered spinal cord while minimizing the difficulties inherent in traditional lumbosacral detethering revision. Although spinal shortening procedures have proven clinical benefit in patients with a recurrent tethered cord, it is unclear how much shortening is required to achieve adequate reduction in spinal cord tension or what impact these osteotomies have on dural buckling. METHODS: The authors calculated mean values from 4 human cadavers to evaluate the effect of 3 different spinal shortening procedures--Smith-Petersen osteotomy (SPO), pedicle subtraction osteotomy (PSO), and vertebral column resection (VCR)--on spinal cord tension and dural buckling. Three cadavers were dedicated to the measurement of spinal cord tension, and 3 other cadavers were devoted to myelography to measure dural buckling parameters. RESULTS: The SPO was associated with a maximal decrease in spinal cord tension of 16.1% from baseline and no dural buckling with any degree of closure. The PSO led to a mean maximal decrease in spinal cord tension of 63.1% from baseline at 12 mm of closure and demonstrated a direct linear relationship between dural buckling and increasing osteotomy closure. Finally, VCR closure correlated with a mean maximal decrease in spinal cord tension of 87.2% from baseline at 10 mm of closure and also showed a direct linear relationship between dural buckling and increases in osteotomy closure. CONCLUSIONS: In this cadaveric experiment, the SPO did not lead to appreciable tension reduction, while a substantial response was seen with both the PSO and VCR. The rate of tension reduction may be steeper for the VCR than the PSO. Adequate tension relief while minimizing dural buckling may be optimal with 12-16 mm of posterior osteotomy closure based on this cadaveric experiment.

Pigmented villonodular synovitis of the thoracic spine.

Pigmented villonodular synovitis (PVNS) is a proliferative lesion of the synovial membranes. Knees, hips, and other large weight-bearing joints are most commonly affected. PVNS rarely presents in the spine, in particular the thoracic segments. We present a patient with PVNS in the thoracic spine and describe its clinical presentation, radiographic findings, pathologic features, and treatment as well as providing the first comprehensive meta-analysis and review of the literature on this topic, to our knowledge. A total of 28 publications reporting 56 patients were found. The lumbar and cervical spine were most frequently involved (40% and 36% of patients, respectively) with infrequent involvement of the thoracic spine (24% of patients). PVNS affects a wide range of ages, but has a particular predilection for the thoracic spine in younger patients. The mean age in the thoracic group was 22.8 years and was significantly lower than the cervical and lumbar groups (42.4 and 48.6 years, respectively; p=0.0001). PVNS should be included in the differential diagnosis of osteodestructive lesions of the spine, especially because of its potential for local recurrence. The goal of treatment should be complete surgical excision. Although the pathogenesis is not clear, mechanical strain may play an important role, especially in cervical and lumbar PVNS. The association of thoracic lesions and younger age suggests that other factors, such as neoplasia, derangement of lipid metabolism, perturbations of humoral and cellular immunity, and other undefined patient factors, play a role in the development of thoracic PVNS.

Cytokine-mediated inflammatory reaction following posterior cervical decompression and fusion associated with recombinant human bone morphogenetic protein-2: a case study.

STUDY DESIGN: Case study with unique laboratory analysis. OBJECTIVE: To present a potentially serious adverse event that may occur in unique individuals when using recombinant human bone morphogenetic protein-2 (rhBMP-2) to augment fusion in posterior cervical spine surgery. SUMMARY OF BACKGROUND DATA: The use of rhBMP-2 to augment posterior cervical decompression and fusion has not been approved by the Food and Drug Administration but has been advocated as safe to use by case series studies and multiple authors. METHODS: A 66-year-old patient with myelopathy underwent posterior cervical decompression and fusion, using rhBMP-2 as a bone graft substitute. The patient had complete resolution of symptoms after surgery until day 6, when she experienced increasing pain and weakness. T2 magnetic resonance images revealed a high intensity fluid collection compressing the cervical cord posteriorly. Emergent decompression was performed and the patient improved until postoperative day 12 when the same clinical scenario occurred. Symptoms again improved with surgical debridement. The clear, nonsanguineous fluid was sent for a quantitative cytokine panel each time. The case is reviewed with specific reference to the evolving literature regarding rhBMP-2 use in the spine, and the findings of seroma analysis. RESULTS: The fluid analysis of the seroma fluid at the time of both debridements showed impressive elevations in inflammatory cytokines, especially IL-6 and IL-8. CONCLUSION: Acute inflammatory reactions to rhBMP-2 can occur in the posterior cervical spine and can lead to significant morbidity. Host factors, BMP-2 dosage, and carrier factors all likely play a role in these complex reactions and must be considered every time an "off label" usage of rhBMP-2 is considered. More study is clearly indicated.

Outcomes following single-treatment Gamma Knife surgery for trigeminal neuralgia with a minimum 3-year follow-up.

OBJECT: Gamma Knife surgery (GKS) has been shown to be effective in treating trigeminal neuralgia (TN). Existing studies have demonstrated success rates of 69.1-85% with median follow-up intervals of 19-60 months. However, series with uniform long-term follow-up data for all patients have been lacking. In the present study the authors examined outcomes in a series of patients with TN who underwent a single GKS treatment followed by a minimum follow-up of 36 months. They used a clinical scale that simplifies the reporting of outcome data for patients with TN. METHODS: Fifty-three consecutive patients with typical, intractable TN received a median maximum radiation dose of 80 Gy applied with a single 4-mm isocenter to the affected trigeminal nerve. Follow-up data were obtained by clinical examination and questionnaire. Outcome results were categorized into the following classes (in order of decreasing success): Class 1A, complete pain relief without medications; 1B, complete pain relief with either a decrease or no change in medications; 1C, > or = 50% pain relief without medications; 1D, > or = 50% pain relief with either a decrease or no change in medications; and Class 2, < 50% pain relief and/or increase in medications. Patients with Class 1A-1D outcome (equivalent to Barrow Neurological Institute Grades I-IIIb) were considered to have a good treatment outcome, whereas in patients with Class 2 outcome (equivalent to Barrow Neurological Institute Grades IV and V) treatment was considered to have failed. RESULTS: A good treatment outcome from initial GKS was achieved in 31 (58.5%) patients for whom the mean follow-up period was 48 months (range 36-66 months). Outcomes at last follow-up were reflected by class status: Class 1A, 32.1% of patients; 1B, 1.9%; 1C, 3.8%; 1D, 20.8%; and Class 2, 41.5%. Statistical analysis showed no difference in outcomes between patients previously treated with microvascular decompression or rhizotomy compared with patients with no previous surgical treatments. Thirty-six percent of patients reported some degree of posttreatment facial numbness. Anesthesia dolorosa did not develop in any patient. CONCLUSIONS: Despite a time-dependent deterioration in the success rate of GKS for medically intractable TN, the authors' study showed that > 50% of patients can be expected to have a good outcome based on their scoring system, with approximately 33% having an ideal outcome (pain free with no need for medications). Long-term data, as those presented here, are important when counseling patients on their treatment options.

Stereotactic radiosurgery for functional disorders.

Stereotactic radiosurgery (SRS) with the Gamma Knife and linear accelerator has revolutionized neurosurgery over the past 20 years. The most common indications for radiosurgery today are tumors and arteriovenous malformations of the brain. Functional indications such as treatment of movement disorders or intractable pain only contribute a small percentage of treated patients. Although SRS is the only noninvasive form of treatment for functional disorders, it also has some limitations: neurophysiological confirmation of the target structure is not possible, and one therefore must rely exclusively on anatomical targeting. Furthermore, lesion sizes may vary, and shielding adjacent radiosensitive neural structures may be difficult or impossible. The most common indication for functional SRS is the treatment of trigeminal neuralgia. Radiosurgical treatment for epilepsy and certain psychiatric illnesses is performed in several centers as part of strict research protocols, and radiosurgical pallidotomy or medial thalamotomy is no longer recommended due to the high risk of complications. Radiosurgical ventrolateral thalamotomy for the treatment of tremor in patients with Parkinson disease or multiple sclerosis, as well as in the treatment of essential tremor, may be indicated for a select group of patients with advanced age, significant medical conditions that preclude treatment with open surgery, or patients who must receive anticoagulation therapy. A promising new application of SRS is high-dose radiosurgery delivered to the pituitary stalk. This treatment has already been successfully performed in several centers around the world to treat severe pain in patients with end-stage cancer.

Repair of the dura mater with processed collagen devices.

BACKGROUND: We evaluated in a canine duraplasty model how specific differences in device physicomechanical properties, porosity, and crosslinking influenced the biological performance of three processed collagen dural substitutes. METHODS: Three collagen dural substitutes were studied: Dura-Guard, DuraGen, and Durepair. The initial strength, stiffness, and suture retention force were measured using standard mechanical test methods. The relative pore sizes of each device were assessed with a scanning electron microscope. Differential scanning calorimetry was used to measure their respective collagen denaturation temperatures. The biologic response and performance of the materials were evaluated via an acute (1 month) and long-term (3 and 6 months) canine bilateral duraplasty study. RESULTS: The mechanical properties of Dura-Guard and Durepair were similar to native dura. We could not quantify the mechanical properties of DuraGen because of its fragile nature. The denaturation temperature of DuraGen and Dura-Guard differed significantly from that reported for native collagens. The denaturation temperature of Durepair was comparable with the values reported for native collagens. All three materials were tolerated well by the animals. DuraGen did not maintain its structural integrity beyond 1 month. Dura-Guard and Durepair persisted for 6 months. Durepair was populated by fibroblasts and blood vessels, whereas Dura-Guard was not. CONCLUSIONS: The three dural substitutes tested were found to be safe and effective in healing surgically created defects in the dura mater. Although each of these dura substitutes are composed of collagen, differences in the collagen source and processing influenced device physicomechanical properties, porosity, and the nativity of the collagen polymer. These measured differences influenced device intraoperative handling and installation as well as the post-operative biological response, where differences in device resorption, cell penetration, vascularization, and collagen remodeling were observed.

Electrocautery-induced ignition of spark showers and self-sustained combustion of onyx ethylene-vinyl alcohol copolymer.

OBJECTIVE: Ethylene-vinyl alcohol copolymer mixed with micronized tantalum (Ta) as radiopacifier (Onyx; Micro Therapeutics Inc., Irvine, CA) has emerged as a useful liquid embolic agent for vascular malformations. We describe intraoperative ignition of Onyx-embolized tissue and undertake an in vitro investigation to reproduce and characterize this hazard. METHODS: Samples of Onyx, Ta-depleted Onyx, Ta-n-butylcyanoacrylate (Ta-NBCA), and Ta powder were exposed to monopolar and bipolar electrocautery in cut and coagulation modes at different power settings to reproduce the intraoperative findings. Recordings of sparking and combustion events were analyzed to characterize duration and relative frequency. RESULTS: Spark showers and self-sustained combustion were observed intraoperatively when an Onyx-embolized artery was coagulated with the monopolar electrocautery. Sparking covered a radius greater than 10 cm, and combustion lasted a median of 1.65 seconds (range, 0.3-12.3 s). Sparking and sustained combustion were reproduced in vitro by both cut and coagulation monopolar modes in Onyx casts and free Ta powder but not in samples of Ta-depleted Onyx or casts of Ta-NBCA. Ignition was similarly observed when using bipolar electrocautery but only at higher energy settings. CONCLUSION: Electrocautery use on tissue containing Onyx results in potentially dangerous uncontrolled sparking and combustion in a process that is Ta dependent. It is recommended that Ta-NBCA be used instead of Onyx in situations mandating the use of a liquid embolic and high-energy electrocautery, pending the development of a safer radiopacifier for use with ethylene-vinyl alcohol copolymer.

Targeting the cranial nerve: microradiosurgery for trigeminal neuralgia with CISS and 3D-flash MR imaging sequences.

OBJECT: The authors undertook a study to identify magnetic resonance (MR) imaging techniques that can be used reliably during gamma knife surgery (GKS) to identify the trigeminal nerve, surrounding vasculature, and areas of compression. METHODS: Preoperative visualization of the trigeminal nerve and surrounding vasculature as well as targeting the area of vascular compression may increase the effectiveness of GKS for trigeminal neuralgia. During the past years our gamma knife centers have researched different MR imaging sequences with regard to their ability to visualize cranial nerves and vascular structures. Constructive interference in steady-state (CISS) fusion imaging with three-dimensional gradient echo sequences (3D-Flash) was found to be of greatest value in the authors' 25 most recent patients. In 24 (96%) out of the 25 patients, the fifth cranial nerve, surrounding vessels, and areas of compression could be reliably identified using CISS/3D-Flash. The MR images were acceptable despite patients' history of microvascular decompression, radiofrequency (RF) ablation, or concomitant disease. In one of 25 patients with a history of multiple RF lesions, the visualization was inadequate due to severe trigeminal nerve atrophy. CONCLUSIONS: The CISS/3D-Flash fusion imaging has become the preferred imaging method at the authors' institutions during GKS for trigeminal neuralgia. It affords the best visualization of the trigeminal nerve, surrounding vasculature, and the precise location of vascular compression.

Cerebral vasospasm following intracranial hypotension caused by cerebrospinal fluid leak from an incidental lumbar durotomy. Case report.

The authors report on the unusual case of a patient with intracranial hypotension following an incidental durotomy complicated by an extensive but reversible cerebral vasospasm. Despite the dural tear repair and correction of the intracranial hypotension, the vasospasm ran its course. The precise mechanism of the cerebral vasospasm in this patient is unclear.

Brain-machine and brain-computer interfaces.

The idea of connecting the human brain to a computer or machine directly is not novel and its potential has been explored in science fiction. With the rapid advances in the areas of information technology, miniaturization and neurosciences there has been a surge of interest in turning fiction into reality. In this paper the authors review the current state-of-the-art of brain-computer and brain-machine interfaces including neuroprostheses. The general principles and requirements to produce a successful connection between human and artificial intelligence are outlined and the authors' preliminary experience with a prototype brain-computer interface is reported.

Transient choroid plexus cysts and benign asymmetrical ventricles: a case suggesting a possible link: case report.

OBJECTIVE AND IMPORTANCE: Brain magnetic resonance imaging scans occasionally reveal asymmetrical ventricles with no identifiable cause. A case is presented that highlights a possible connection between transient choroid plexus cysts and benign asymmetrical ventricles. CLINICAL PRESENTATION: The patient was a 2.5-week-old asymptomatic boy. Transcranial ultrasound and magnetic resonance imaging revealed the infant to have a left frontal horn choroid plexus cyst and a mildly dilated left lateral ventricle. Head circumference was at 90% of the norm for age. The neurological examination revealed nothing abnormal. Four months later, follow-up magnetic resonance imaging revealed complete resolution of the cyst with persistent ventricular asymmetry. INTERVENTION: No surgical intervention was undertaken. The lesion was assessed via x-ray. CONCLUSION: Spontaneously resolving choroid plexus cysts of infancy causing outflow obstruction of the lateral ventricle may be one of the underlying causes of benign asymmetrical ventricles.

Nasofrontal dermoid sinus cyst: report of two cases.

OBJECTIVE AND IMPORTANCE: Nasofrontal dermoid sinus cysts are rare. The embryological origin, presentation, treatment, and genetic associations of two cases of these cysts are discussed. Emphasis is placed on physical findings and the importance of addressing both the intracranial and extracranial components. CLINICAL PRESENTATION: The first patient, a 33-year-old woman, sought care for chemical meningitis. As a child, she was differentiated from her identical twin sister by a dimple on the tip of her nose. The second patient, a 34-year-old man, sought care for new-onset seizures. Since birth, he had a dimple on the tip of his nose. As a child, he had undergone resection of a nasal cyst. Imaging studies in both patients indicated a midline anterior cranial base mass within the falx and a defect in the crista galli. INTERVENTION: Both patients underwent biorbitofrontal nasal craniotomy. A bifrontal craniotomy was performed first, then removal of the orbitonasal ridge. The dermoid and involved falx were resected. The sinus tract was followed through the crista galli and resected up to the osteocartilaginous junction in the nose. The remainder of the tract was resected via a small incision through the nares. The dura was closed primarily by mobilizing the dura along the sides of the crista galli. After surgery, both patients still possessed their sense of smell. CONCLUSION: Nasofrontal dermoid sinus cysts have a unique embryological origin. A midline basal frontal dermoid associated with a dimple on the nasal surface with or without protruding hair and sebaceous discharge is the pathognomonic presentation. It is important to address both the intracranial and extracranial component surgically. Although concomitant anomalies and familial clustering have been described, most cases are spontaneous occurrences.