Spinal stabilization by using crossed-screw anterior-posterior fixation after multisegmental total spondylectomy for thoracic chondrosarcoma. Case report.

The authors describe the case of a 41-year-old man with high-grade chondrosarcoma who presented with a paraspinous mass extending into three thoracic vertebrae (T10-12). Crossfixed long anterior and posterior instrumentation was placed after three complete spondylectomies (T10-12). This technique augments spinal stability with an outrigger effect by using crossfixators placed between paired dorsal rods, as well as between the anterior and posterior hardware components. This technique may be used as an alternative when multiple vertebrae or all three spinal columns are involved by radioresistant malignant tumors in patients in whom there is a relatively long life expectancy.

The management of unilateral lateral mass/facet fractures of the subaxial cervical spine: the use of magnetic resonance imaging to predict instability.

STUDY DESIGN: Retrospective review of the clinical course and cervical spine plain radiographs, computed tomography, and magnetic resonance imaging of 24 consecutive patients for a 2-year period with a unilateral lateral mass/facet fracture. OBJECTIVE: To propose a treatment algorithm for the management of unilateral lateral mass/facet fractures of the subaxial cervical spine based on ligamentous injury detected by magnetic resonance imaging. SUMMARY OF BACKGROUND DATA: There have been no previous reports of the use of magnetic resonance imaging to predict clinical instability. METHODS: A retrospective review of the clinical course of all unilateral mass/facet fractures identified over a 2-year period was conducted. All cervical spine plain radiographs, computed tomography scans, and magnetic resonance images were reviewed by a neuroradiologist blinded to the clinical course of the patient. Magnetic resonance T1-weighted and inversion recovery images were used to evaluate the integrity of the facet region, interspinous ligament, anterior longitudinal ligament, and posterior longitudinal ligament. RESULTS: Twenty-four unilateral lateral mass/facet fractures were identified. Only six initial cervical spine series demonstrated a bony abnormality at the level of the fracture. The fractures were identified by computed tomography and were almost all nondisplaced or minimally displaced. Less than half of the fractures extended ventrally to involve the transverse process or foramen transversarium or dorsally to involve the lamina. Twelve fractures were nonoperatively treated and 12 were treated surgically for stabilization. Ten patients in the operative group presented with or developed a subluxation. Nine of these patients had injury to at least three of the four ligaments evaluated by magnetic resonance imaging. In the nonoperative group, only three patients had extensive ligamentous injury at the level of the fracture. All three of these patients were lost to follow-up. CONCLUSIONS: Plain radiographs of the cervical spine lack sensitivity to detect the presence of lateral mass/ facet fractures. The appearance of the fracture on computed tomography does not indicate instability. The degree of ligamentous injury at the level of the fracture demonstrated on magnetic resonance imaging correlates with instability in this series. Operative stabilization may be indicated for unilateral lateral mass fractures that present with a subluxation or that have injury to at least three of the following ligaments: the facet region, the interspinous ligament, the anterior longitudinal ligament, and the posterior longitudinal ligament. However, before a definitive management plan can be formulated, results from this small series require further validation.

Intracranial vertebral arteriovenous fistula. Case report.

True intracranial arteriovenous fistulas are rare. The authors report a case of a direct fistula between the intracranial portion of the vertebral artery and the lateral medullary venous system. The patient initially presented with a subarachnoid hemorrhage. An open surgical approach with clip obliteration of the lesion was used. The anatomy of this lesion and its surgical management are described.

Generation and migration of cells in the developing striatum.

The development of the rat striatum was investigated using a combination of two histochemically distinguishable retrovirus vectors. Using this method, it was possible to identify clonal boundaries within the embryonic striatum and thus determine patterns of proliferation, migration, and some lineal relationships. Several novel aspects of striatal histogenesis were discovered. Striatal progenitor cells do not exhibit a stem cell pattern of division between embryonic day 15 (E15) and E19; a progenitor-progeny relationship appears to exist for ventricular zone and subventricular zone (SVZ) cells; striatal progenitors produce a variety of clone types; some SVZ cells migrate radially, and some migrate tangentially within the SVZ; and radial glia and presumptive neurons can occur in the same clone.

A recombinant retrovirus encoding alkaline phosphatase confirms clonal boundary assignment in lineage analysis of murine retina.

Recombinant retroviruses encoding the histochemically detectable enzyme beta-galactosidase have been used to investigate lineage in the vertebrate nervous system. Identification of the descendants of individual progenitors is straightforward when progeny cells are arranged in a reproducible, clustered pattern, but difficulties in interpretation arise when progeny migrate extensively and/or in an irregular pattern. To better resolve clonal boundaries, additional histochemical marker viruses that engender distinctive reaction products can be used in combination with lacZ-bearing viruses. To this end, we have created a retrovirus vector, DAP, encoding an easily assayable enzyme, human placental alkaline phosphatase. DAP was found to be at least as useful as a lacZ-encoding retrovirus (e.g., BAG) with respect to high viral titer, stability of expression, and in identification of infected cells in vivo. Moreover, it was found to be neutral with respect to postnatal rodent retinal development and offered superior staining characteristics relative to lacZ. Coinfection of rodent retina with DAP and BAG allowed an examination of the clonal nature of radial arrays of labeled retinal cells that previously had been described as products of a single infected progenitor. Of 1100 radial arrays examined for the presence of both DAP- and BAG-infected cells, only 1.2% were the result of infection with more than one virus.

Benign spinal nerve sheath tumors: their occurrence sporadically and in neurofibromatosis types 1 and 2.

Benign spinal nerve sheath tumors (neurofibromas and schwannomas) often occur on dorsal nerve roots sporadically or in neurofibromatosis types 1 and 2. These are histologically benign tumors, and distinction between them is frequently not made by clinicians. To determine if there is a correlation between the histological pattern of benign spinal nerve sheath tumors and the type of neurofibromatosis, the clinical and pathological features of these tumors (86 surgical specimens and five autopsies) in 68 patients were reviewed. The patients were classified into one of four categories: neurofibromatosis type 1, neurofibromatosis type 2, uncertain, or sporadic. The diagnostic criteria used for neurofibromatosis types 1 and 2 were established by the National Institutes of Health. Patients who did not fulfill criteria for either neurofibromatosis type 1 or 2 but who had multiple nervous system tumors or other stigmata of neurofibromatosis were designated "uncertain." Spinal nerve sheath tumors were considered sporadic in 42 cases (40 schwannomas and two neurofibromas). In the 14 patients with neurofibromatosis type 1, all spinal nerve sheath tumors were neurofibromas. In six of the seven patients with neurofibromatosis type 2, all spinal nerve sheath tumors were schwannomas. One patient with neurofibromatosis type 2 had a spinal nerve sheath schwannoma and a tumor with features of both tumor types. The authors conclude that spinal nerve sheath tumors in patients with neurofibromatosis type 1 are neurofibromas. In contrast, spinal nerve sheath tumors occurring in neurofibromatosis type 2 or sporadically are most frequently schwannomas. The distinct histological features of these tumors may reflect different pathogenetic mechanisms even though they arise at identical sites in neurofibromatosis types 1 and 2.

Correlates of survival and the Daumas-Duport grading system for astrocytomas.

In order to examine the correlation between prognosis and the histological features of nuclear atypia, mitosis, endothelial proliferation, and necrosis in supratentorial adult astrocytomas, the authors reviewed 251 such cases treated at the Massachusetts General Hospital between 1972 and 1980. One point was given for the presence of each feature. The total number of features was translated into a grade as follows: none of the four features = Grade 1 (one patient), one feature = Grade 2 (36 patients), two features = Grade 3 (33 patients), and three or four features = Grade 4 (181 patients). The period of survival was significantly associated with grade, the presence or absence of each of the four histological features, patient's age, type of operation, radiation therapy, and extent of tumor (log rank, p less than 0.05). The variables associated with grade were age (p less than 0.001) and radiation therapy (p less than 0.02). After adjustment for these variables using a Cox proportional-hazards model, the difference in overall survival time between patients in Grades 2 and 3 was not statistically significant. When comparable groups of patients were examined in terms of age or receipt of radiation therapy, the median survival times differed markedly. Patients 50 years of age or less had a median survival time of 68 months (Grade 2 tumors), 29 months (Grade 3 tumors), and 13 months (Grade 4 tumors). Patients over 50 years of age had a median survival time of 6 months (Grade 2 and 4 tumors) and 9 months (Grade 3 tumors). Those patients who had received radiation therapy had a median survival time of 68 months (Grade 2 tumors), 21 months (Grade 3 tumors), and 11 months (Grade 4 tumors). Those patients who did not receive radiation therapy had a median survival time of 1 month (Grade 2 tumors) and 2 months (Grade 3 and 4 tumors); over half of these patients died within 2 months of surgery. This grading system, originally proposed by Daumas-Duport, et al., is simple, objective, and reproducible, and correlates well with survival times. The authors recommend that astrocytomas be graded on a scale of 1 to 4, with Grade 1 reserved for the rare adult supratentorial astrocytoma with none of the four histological features.

Leptomeningeal cyst resulting from adulthood trauma: case report.

The authors report a rare sequelae of a skull fracture in an adult, a leptomeningeal cyst. A unique method for repairing this defect is described as well.