Pediatric spinal cord injury in infant piglets: description of a new large animal model and review of the literature.

OBJECTIVE: To develop a new, clinically relevant large animal model of pediatric spinal cord injury (SCI) and compare the clinical and experimental features of pediatric SCI. METHODS: Infant piglets (3-5 weeks old) underwent contusive SCI by controlled cortical impactor at T7. Severe complete SCI was induced in 6 piglets, defined as SCI with no spontaneous return of sensorimotor function. Eight piglets received incomplete SCI, which was followed by partial recovery. Somatosensory evoked potentials, magnetic resonance imaging, neurobehavioral function, and histopathology were measured during a 28-day survival period. RESULTS: Mean SCI volume (defined as volume of necrotic tissue) was larger after complete compared with incomplete SCI (387 +/- 29 vs 77 +/- 38 mm3, respectively, P < 0.001). No functional recovery occurred after complete SCI. After incomplete SCI, piglets initially had an absence of lower extremity sensorimotor function, urinary and stool retention, and little to no rectal tone. Sensory responses recovered first (1-2 days after injury), followed by spontaneous voiding, lower extremity motor responses, regular bowel movements, and repetitive flexion-extension of the lower extremities when crawling. No piglet recovered spontaneous walking, although 4 of 8 animals with incomplete injuries were able to bear weight by 28 days. In vivo magnetic resonance imaging was performed safely, yielded high-resolution images of tissue injury, and correlated closely with injury volume seen on histopathology, which included intramedullary hemorrhage, cellular inflammation, necrosis, and apoptosis. CONCLUSION: Piglets performed well as a reproducible model of traumatic pediatric SCI in a large animal with chronic survival and utilizing multiple outcome measures, including evoked potentials, magnetic resonance imaging, functional outcome scores, and histopathology.

An anatomical study of the lumbosacral plexus as related to the minimally invasive transpsoas approach to the lumbar spine.

OBJECT: Minimally invasive anterolateral approaches to the lumbar spine are options for the treatment of a number of adult degenerative spinal disorders. Nerve injuries during these surgeries, although rare, can be devastating complications. With an increasing number of spine surgeons utilizing minimal access retroperitoneal surgery to treat lumbar problems, the frequency of complications associated with this approach will likely increase. The authors sought to better understand the location of the lumbar contribution of the lumbosacral plexus relative to the disc spaces encountered when performing the minimally invasive transpsoas approach, also known as extreme lateral interbody fusion or direct lateral interbody fusion. METHODS: Three fresh cadavers were placed lateral, and a total of 3 dissections of the lumbar contribution of the lumbosacral plexus were performed. Radiopaque soldering wire was then laid along the anterior margin of the nerve fibers and the exiting femoral nerve. Markers were placed at the disc spaces and lateral fluoroscopy was used to measure the location of the lumbar plexus along each respective disc space in the lumbar spine (L1-2, L2-3, L3-4, and L4-5). RESULTS: The lumbosacral plexus was found lying within the substance of the psoas muscle between the junction of the transverse process and vertebral body and exited along the medial edge of the psoas distally. The lumbosacral plexus was most dorsally positioned at the posterior endplate of L1-2. A general trend of progressive ventral migration of the plexus on the disc space was noted at L2-3, L3-4, and L4-5. Average ratios were calculated at each level (location of the plexus from the dorsal endplate to total disc length) and were 0 (L1-2), 0.11 (L2-3), 0.18 (L3-4), and 0.28 (L4-5). CONCLUSIONS: This anatomical study suggests that positioning the dilator and/or retractor in a posterior position of the disc space may result in nerve injury to the lumbosacral plexus, especially at the L4-5 level. The risk of injuring inherent nerve branches directed to the psoas muscle as well as injury to the genitofemoral nerve do still exist.

Clinical feasibility of minimally invasive cervical laminoplasty.

Minimally invasive approaches to the cervical spine for lateral disc herniation or foraminal stenosis have recently been described. Lower rates of blood loss, decreased narcotic dependence, and less tissue destruction as well as shorter hospital stays are all advantages of utilizing these techniques. These observations can also be realized with a minimal access approach to cervical laminoplasty. Multiple levels of the cervical spine can be treated from a posterior approach with the potential to decrease the incidences of postoperative axial neck pain and kyphotic deformity. In this report the authors present a concise history of the open laminoplasty technique, provide data from previous cadaveric studies (6 cases) along with recent clinical experience for minimally invasive laminoplasty, and describe the advantages and challenges of this novel procedure.

Acute neurological deficit after minor trauma in an infant with achondroplasia and cervicomedullary compression. Case report and review of the literature.

Cervicomedullary compression at the foramen magnum in patients with achondroplasia can be associated with apnea, neurological deficits, and sudden death. Decompressive operations are often performed in symptomatic patients. In asymptomatic patients, the indications for prophylactic decompression are controversial. The authors present the case of a previously neurologically intact 4-month-old girl with achondroplasia who presented with severe hemiparesis after a low-velocity motor vehicle accident. Imaging studies demonstrated osseous compression of the medulla and upper cervical spinal cord with associated parenchymal signal changes. To the authors' knowledge this is the first reported case of a new neurological deficit after a minor trauma in this patient population. The authors review the relevant literature, focusing on the indications for cervicomedullary decompression in infants with achondroplasia. They propose that asymptomatic patients with achondroplasia and osseous compression at the foramen magnum should be offered prophy-lactic surgery if T2-weighted magnetic resonance imaging signal changes in the spinal cord are observed. Prophylactic surgery can be considered an option in patients whose imaging studies do not show signal changes in the spinal cord but demonstrate significant osseous compression and absence of visible subarachnoid spaces.

Pneumocephalus in a patient with a ventriculoperitoneal shunt after percutaneous gastrojejunostomy catheter placement: case report.

BACKGROUND: Percutaneous gastrostomy and/or jejunostomy associated with ventriculoperitoneal (VP) shunting in critically ill neurosurgical patients is not an uncommon combination. Massive intraventricular pneumocephalus has not been previously reported as a complication of percutaneous gastrostomy and/or jejunostomy placement in a patient with a VP shunt. A case is presented here where we believe such a complication occurred. CASE DESCRIPTION: Our patient is a 68-year-old woman who experienced a subarachnoid hemorrhage from a right anterior choroidal aneurysm rupture. The patient underwent endovascular coiling. The patient developed a communicating hydrocephalus and eventually necessitated a VP shunt. Two weeks after shunt placement, our patient had a fluoroscopic percutaneous gastrostomy and/or jejunostomy catheter placed. A computed tomographic scan of the brain obtained after feeding tube placement for a change in mental status revealed a significant amount of air in the lateral ventricles. The patient was managed expectantly over the next several days with slow clinical and radiographic improvement. CONCLUSIONS: The etiology for the increased intraventricular pneumocephalus is believed to be retrograde leakage of air into the ventricles via the VP shunt during insufflation of the abdomen for percutaneous placement of a gastrojejunostomy feeding tube.

Occiput to thoracic fusion after surgical resection of desmoid tumor.

BACKGROUND: Desmoid tumors are rare clinical entities that cause significant morbidity based on their locally aggressive nature. Complete resection with wide margins is the standard of care; however, when arising in the neck, resection is limited due to proximity of the lesion to critical structures. CASE DESCRIPTION: We describe a complete resection of a desmoid tumor requiring extensive resection of cervical extensor musculature. We were able to achieve a total resection of a cervical desmoid tumor with no evidence of recurrence at follow-up. CONCLUSIONS: Complete resection of desmoid tumors is the standard of care. In this case, we felt that complete resection would lead to iatrogenic instability; therefore, an occiput to thoracic fusion was performed at the time of the resection.

The use of modest systemic hypothermia after iatrogenic spinal cord injury during surgery.

Iatrogenic spinal cord injury (SCI) is an uncommon (0%-3%), yet devastating, complication of spine surgery. Recent evidence based on small clinical studies indicates that modest hypothermia is a feasible treatment option for severe SCI. We extended this treatment modality to patients with devastating iatrogenic SCI. We conducted a retrospective case series of five male patients (cervical trauma--1, cervical degenerative--2, thoracic trauma--1, and thoracic scoliosis--1) with an age range of 16-51 years (average age of 46 years) with intraoperative motor-evoked potential/somatosensory-evoked potential loss secondary to catastrophic events during the spinal operation associated with new SCI. Modest hypothermia was instituted immediately postsurgery for 24 hours. Four patients also received methylprednisolone. Preoperative American Spinal Injury Association (ASIA) scores were D (n=3) and E (n=2), while immediate postoperative scores were A (n=1), B (n=1), C (n=2), and D (n=1). Immediate postoperative MRI revealed new cord signal change in three patients. Two patients required subsequent surgery. ASIA scores at last follow-up were C (n=1), D (n=3), and E (n=1) with an improvement of 1-2 grades per patient. Adverse events such as pulmonary embolism, deep venous thrombosis, coagulopathy, or infection were not observed. Hypothermia is a feasible treatment option for patients with iatrogenic SCI. While hypothermia has not been proven to improve outcomes in these situations, aggressive medical management, including cooling, resulted in better-than-expected outcomes in this small cohort.

Outcomes in pediatric patients with Chiari malformation Type I followed up without surgery.

OBJECT: The natural history of untreated Chiari malformation Type I (CM-I) is poorly defined. The object of this study was to investigate outcomes in pediatric patients with CM-I who were followed up without surgical intervention. METHODS: The authors retrospectively reviewed 124 cases involving patients with CM-I who presented between July 1999 and July 2008 and were followed up without surgery. The patients ranged in age from 0.9 to 19.8 years (mean 7 years). The duration of follow-up ranged from 1.0 to 8.6 years (mean 2.83 years). Imaging findings, symptoms, and findings on neurological examinations were noted at presentation and for the duration of follow-up. RESULTS: The mean extent of tonsillar herniation at presentation was 8.35 mm (range 5-22 mm). Seven patients had a syrinx at presentation. The syrinx size did not change in these patients on follow-up imaging studies. No new syrinxes developed in the remaining patients who underwent subsequent imaging. The total number of patients with presenting symptoms was 81. Of those 81 patients, 67 demonstrated symptoms that were not typical of CM-I. Of the 14 patients with symptoms attributed to CM-I, 9 had symptoms that were not severe or frequent enough to warrant surgery, and surgery was recommended in the remaining 5 patients. Chiari malformation Type I was also diagnosed in 43 asymptomatic patients who had imaging studies performed for various reasons. No new neurological deficits were noted in any patient for the duration of follow-up. CONCLUSIONS: The majority of patients with CM-I who are followed up without surgery do not progress clinically or radiologically. Longer follow-up of this cohort will be required to determine if symptoms or new neurological findings develop over the course of many years.

Neurologic findings of craniovertebral junction disease.

In this review, we explain the origins of central cord syndrome and Bell's cruciate paralysis and the intricate detail of neural pathways located in this region and their influence on motor and sensory function. Although lesion studies and tract tracing studies on primates over the past 50 years refute the theory of a somatotopically organized corticospinal tract, this concept continues to pervade many neuroanatomic texts. We categorized the various pathologies of the craniovertebral junction and their unique neurologic presentations. New developments in the fields of neuroscience of spinal tract lesioning are also discussed.

Treatment of a persistent iatrogenic cerebrospinal fluid-pleural fistula with a cadaveric dural-pleural graft.

BACKGROUND CONTEXT: A cerebrospinal fluid (CSF)-pleural fistula is a unique condition with which all spine surgeons need to be familiar, particularly those who use anterolateral approaches to the thoracic region. When direct suturing of the dural defect is not possible, techniques for indirect repair must be considered. PURPOSE: To report a novel technique for repair of a thoracic CSF-pleural fistula with a cadaveric dural-pleural graft after failure of initial treatment with Duragen (Integra, Plainsboro, NJ) and fibrin glue. STUDY DESIGN/SETTING: Case report/University of Miami/Jackson Memorial Medical Center. METHODS: The case of a 65-year-old female is presented. RESULTS: The patient represented 5 weeks after the initial operation (left-sided thoracotomy, partial T10-T11 corpectomy and removal of an intradural calcified disc) with dyspnea and severe positional headaches. Imaging of the brain revealed a subdural hematoma and magnetic resonance imaging of the thoracic region demonstrated a pseudomeningocele surrounding the postsurgical bed. She underwent a revision thoracotomy and CSF-pleural fistula repair. We addressed the dural opening indirectly by suturing a piece of cadaveric dural allograft to the thickened pleura, after Duragen and fibrin glue were placed over the dural defect. A lumbar drain and a chest tube were also placed. At 12 weeks post-op, the subdural hematoma had completely resolved and her chest X-rays demonstrated a significant decrease in the CSF-pleural collection. CONCLUSION: Anterolateral thoracic disc surgery poses a great challenge to the spine surgeon but can provide the most direct way of decompressing the spinal cord as a result of ventral pathology. Some of the most difficult aspects of dealing with a CSF leak in this area relates to 1) the relative complexity of suturing the dura directly as it is at a considerable distance from the operating surgeon; 2) the manner in which the contralateral dura slopes away and is hidden from view; and 3) the relatively negative intrathoracic pressure, which encourages the persistent flow of CSF from the intradural to the pleural cavity. We speculate that with open thoracic surgery and the creation of a large potential space with an open dural defect, this technique provided an additional barrier against the formation of a CSF-pleural fistula. Using this technique, we intentionally create a pseudomeningocele into the corpectomy defect that is contained within the confines of our dural-pleural graft.

A comprehensive review of the safety profile of bone morphogenetic protein in spine surgery.

WE REVIEW OUR current understanding of the development and potential clinical applications of bone morphogenetic protein (BMP) in spine surgery. We also review the evidence for adverse events associated with the use of BMP and suggest potential reasons for these events and means of complication avoidance. Bone morphogenetic protein 2 (rhBMP-2) is approved by the Food and Drug Administration for anterior lumbar interbody fusion; rhBMP-7, on the other hand, is approved for long bone defects and has received a humanitarian device exemption for revision posterolateral lumbar operations and recalcitrant long bone unions. Nevertheless, "off-label" use in various spinal procedures has been reported and is increasing in frequency. Specific guidelines for rhBMP-2 and rhBMP-7 use are lacking because of the limited availability of randomized controlled clinical trials and its diverse use in many spinal applications. Mechanisms of delivery, carrier type, graft position, surgical location, and variations in BMP concentration may differ from one surgery to the next. Adverse events linked to either rhBMP-2 or rhBMP-7 use include ectopic bone formation, bone resorption or remodeling at the graft site, hematoma, neck swelling, and painful seroma. Other potential theoretical concerns include carcinogenicity and teratogenic effects. In this review, we provide the reader with a historical perspective on BMP, current and past research to support its use in spinal procedures, and a critical analysis of the complications reported thus far.

Minimally invasive anterolateral approaches for the treatment of back pain and adult degenerative deformity.

Minimally invasive and interbody and instrumented fusion techniques are increasingly being used for the treatment of adult degenerative disc disease, stenosis, and deformity of the lumbar spine. Advocates of minimal access spinal approaches list certain advantages over open procedures, including decreased postoperative pain and narcotic requirements, shorter hospital stays, less blood loss, and smaller incisions. The minimally invasive anterolateral approach allows access to the lumbar spine through the retroperitoneal space. We report on the short-term clinical and radiographic outcomes in four patients with mid to high lumbar coronal deformities treated at our institution with the anterolateral transpsoas minimally invasive approach. The primary presentation of these patients was back and leg pain. All patients showed improvement in their preoperative symptoms and solid arthrodesis at 6 months. Independent nonbiased patient pain analysis was also performed. Mean follow-up was 10 months (standard deviation, 1.4 mo), and mean hospital stay was 3.5 days (standard deviation, 1.9 d). One patient had additional posterior segmental instrumentation placed. Mean Cobb angles in the coronal plane were 28.5 degrees preoperatively and 18.3 degrees postoperatively (P < 0.05). We also present a historical perspective on retroperitoneal spine surgery, a regional anatomic description of the lumbosacral plexus and surrounding structures, and a description of the surgical technique as related to treatment of lumbar deformity.

Ventriculoatrial shunt catheter displacement in a child with partial anomalous pulmonary venous return: case report.

Ventriculoatrial (VA) shunts remain the most used alternative to ventriculoperitoneal shunts in infants with hydrocephalus. The authors report a case of an acute VA shunt malfunction as a result of distal catheter displacement in an 18-month-old girl with partial anomalous pulmonary venous return. The child presented with respiratory compromise, and a chest radiograph revealed a lung infiltrate and normal position of the distal shunt catheter tip. Computed tomography demonstrated stable ventricle size in comparison with previous studies. As the patient's respiratory distress progressed, she required intubation, mechanical ventilation with high airway pressures and inspired oxygen concentrations, muscle relaxants, and sedation. A routine morning chest radiograph several days after admission revealed displacement of the distal catheter into the left innominate vein. Later that day the child's pupils were noted to be large and unreactive and a distal shunt malfunction was diagnosed. Complications of VA shunts and the presumed mechanism by which the catheter became displaced are discussed.

Structure of Mycobacterium tuberculosis methionine sulfoxide reductase A in complex with protein-bound methionine.

Peptide methionine sulfoxide reductase (MsrA) repairs oxidative damage to methionine residues arising from reactive oxygen species and reactive nitrogen intermediates. MsrA activity is found in a wide variety of organisms, and it is implicated as one of the primary defenses against oxidative stress. Disruption of the gene encoding MsrA in several pathogenic bacteria responsible for infections in humans results in the loss of their ability to colonize host cells. Here, we present the X-ray crystal structure of MsrA from the pathogenic bacterium Mycobacterium tuberculosis refined to 1.5 A resolution. In contrast to the three catalytic cysteine residues found in previously characterized MsrA structures, M. tuberculosis MsrA represents a class containing only two functional cysteine residues. The structure reveals a methionine residue of one MsrA molecule bound at the active site of a neighboring molecule in the crystal lattice and thus serves as an excellent model for protein-bound methionine sulfoxide recognition and repair.