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PubMed2005

Rotational vertebral artery syndrome: oculographic analysis of nystagmus.

In four patients with rotational vertebral artery syndrome (RVAS), the initial nystagmus was mostly downbeat, with the horizontal and torsional components beating toward the compressed vertebral artery side (n = 3) or directed away (n = 1). Three patients showed spontaneous reversal of the nystagmus and two exhibited no or markedly diminished responses on immediate retrial of head rotation (habituation). The patterns of nystagmus suggest that RVAS may result from differing mechanisms.

Aged↗
PubMedDate not supplied

Transoral exposure of the atlantoaxial region.

A broad spectrum of disease entities affects the atlantoaxial-clival region. This area is readily accessible through a transoral approach, which offers capabilities for canal decompression and fusion. A case is reported that required transoral odontoidectomy with concurrent excision of an osteophyte from the base of an ununited odontoid fracture. Operative preparation, technique, and postoperative management are described in detail. The advantage and applications of the procedure are discussed.

Axis, Cervical Vertebra↗
PubMed1984

Microscopic decompression of the anterior upper cervical spine: a case of odontoid malunion to the atlas.

For the past 20 years, the transoral approach to the upper cervical spine has been utilized for odontoid fractures, the removal of an abnormal odontoid process, decompression of basilar impression, and biopsy or resection of nasopharyngeal or metastatic tumors. The effectiveness and safety of this procedure is well documented. Use of the surgical microscope adds to the efficiency and safety of the procedure. We are reporting a case of fusion of the odontoid base to the anterior arch of the atlas. To our knowledge, this entity has not been described previously. The spinal cord was protected by an initial posterior fusion of C-1, C-2, followed in 10 days by a tracheostomy and the transoral removal of the anterior C-1 arch and the abnormal dens. Because the medical history did not reveal a source of trauma, it is supposed that the patient had malunion of the odontoid process to C-2, with subsequent migration and fusion of the dens to the C-1 arch.

Axis, Cervical Vertebra↗
PubMed1986

Use of the Philadelphia collar as an alternative to the halo vest in patients with C-2, C-3 fractures.

We analyzed retrospectively 27 individuals with C-2, C-3 fractures, 8 of whom were treated with a Philadelphia collar rather than the more commonly used halo vest. Successful fusion without neurological deficit occurred in all cases whether treatment was by Philadelphia collar (n = 8), halo apparatus (n = 16), or prolonged bed rest (n = 3). There was an increase in subluxation in 3 patients in both the Philadelphia collar group and the halo apparatus group. However, 1 of the 3 in the collar group was uncooperative and discarded his collar during treatment. If he is excluded, the subluxation rate in the Philadelphia collar group is 27%; the rate in the halo group is 19%. The Philadelphia collar seems to be an acceptable means of stabilizing the neck in C-2, C-3 fractures, but one must consider the degree of cervical movement in the collar (as detected by dynamic x-ray films), patient reliability, and patient age. The presence of subluxation did not preclude successful fusion in either the Philadelphia collar or the halo vest groups.

Adolescent↗
PubMed1986

Experience in the management of odontoid process injuries: an analysis of 128 cases.

The authors present a retrospective analysis of 128 cases of odontoid process injury treated at the University of Minnesota and affiliated hospitals between the years 1967 and 1983. Of these 128 cases, 110 were acute fractures, while 18 patients suffered from old, unstable odontoid injuries. Motor vehicle accident was the leading cause of injury, and the largest group of patients was in their second decade. Type II fractures were the most commonly encountered type of injury, and anterior subluxation was the most common displacement. Posterior subluxation, however, had the highest incidence of associated neurological deficit. Regarding treatment, the 110 acute fracture patients fell into the following groups: 16 patients died during the acute phase, 14 patients underwent early posterior cervical fusion, and 80 patients underwent a course of external skeletal fixation. The remaining 18 patients with old unstable injuries underwent posterior cervical fusion. An analysis of the results in these groups led to the elucidation of certain factors that likely are important in determining the treatment of each individual patient. These factors include age of the patient, type of odontoid fracture, direction and degree of fracture displacement, and diagnostic delay. Fracture reduction and halo immobilization are the treatments preferred for patients who are diagnosed within 1 week of injury, who are less than 65 years of age and who have anteriorly, nondisplaced, or minimally posteriorly subluxed (less than 2 mm) Type II fractures, or who have any Type III injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

New subtype of acute odontoid fractures (type IIA).

A new subtype of axis fracture, thought to be a variant of the Type II odontoid fracture, is described. High resolution, thin section computed tomography can assist in the identification of comminuted fractures at the base of the dens with associated free fracture fragments. Because these injuries are markedly unstable and cannot be suitably realigned and reduced by external means, early surgical therapy should be considered.

Acute Disease↗
PubMed1989

Diagnosis and treatment of an odontoid fracture in a patient with polyostotic fibrous dysplasia: case report.

Fibrous dysplasia of the cervical spine is rare. No prior reports have discussed odontoid fractures in the setting of fibrous dysplasia. We describe a 26-year-old man who suffered a traumatic odontoid fracture in an area of preexisting fibrous dysplasia. The patient was treated conservatively in a sterno-occipito-mandibular immobilizer brace with a good result. A review of fibrous dysplasia is presented. Alternative methods of diagnosis and treatment options in our patient are discussed.

Adult↗
PubMed2004

Microsurgical excision of a retro-odontoid disc hernia via a far-lateral approach: successful treatment of a rare cause of myelopathy: case report.

OBJECTIVE AND IMPORTANCE: Among mass lesions causing myelopathy at the craniovertebral junction, retro-odontoid intervertebral disc hernias are very rare, with only four such cases reported in the literature. CLINICAL PRESENTATION: A 77-year-old woman with this rare condition complained of motor and sensory disturbances in her extremities. Magnetic resonance imaging scans demonstrated an extradural mass lesion at the craniovertebral junction, compressing the lower medulla oblongata and the upper cervical cord posteriorly. INTERVENTION: The lesion, which was partly mucinous cartilaginous and partly fatty and fibrous, was meticulously removed via a left far-lateral approach. The lesion was not neoplastic but was determined to be composed of fibrocartilaginous tissue, consistent with disc material. Postoperatively, the patient's sensory disturbances and motor weakness improved, and magnetic resonance imaging scans demonstrated marked shrinkage of the lesion. CONCLUSION: Sagittal, T1-weighted, magnetic resonance imaging scans demonstrated a low-intensity band between the odontoid process and the body of the axis, which suggested a persistent cartilaginous band. Although upward migration of a herniated disc from the lower cervical spine and degeneration of retro-odontoid ligaments might be possible causes, a persistent cartilaginous band extending between the odontoid process and the body of the axis was considered to be the more likely origin of the retro-odontoid intervertebral disc hernia. Because the far-lateral surgical approach does not require retraction of the cervical cord and provides safe access to the lesion at the craniovertebral junction, it is a suitable surgical method for this condition.

Aged↗
PubMed2004

Cadaveric morphometric analysis for atlantal lateral mass screw placement.

OBJECTIVE: Atlantal lateral mass screws provide an alternative to C1/C2 transarticular screws and, in some cases, can obviate the need for extending a fusion to the occiput. For these reasons, C1 lateral mass screws are becoming increasingly popular. However, the critical local anatomy and unfamiliarity with this new technique can make C1 screw placement more challenging. METHODS: Morphometric analysis was performed on 74 cadaveric spines obtained from the Department of Anatomy at the Keck School of Medicine, University of Southern California. Critical measurements were determined for screw entry points, trajectories, and lengths for application of the technique described by Harms and Melcher. RESULTS: The mean height and width for screw entry on the posterior surface of the lateral mass were 3.9 and 7.3 mm, respectively. The maximum medialized screw trajectory ranged from 25 to 45 degrees (mean, 33 degrees). The mean maximal screw length to obtain bicortical purchase was 22.5 mm, and the mean minimum screw depth was 14.4 mm. Screw depths varied on the basis of the entry point, trajectory, and vertebral morphology. The overhang of the posterior arch averaged 11.4 mm (range, 6.9-17 mm). All specimens could accommodate 3.5-mm lateral mass screws bilaterally with proper preparation of the entry site. CONCLUSION: Significant variations in the morphology of C1 exist. However, the large size of the atlantal lateral mass makes screw placement forgiving. Preoperative computed tomographic scans and intraoperative fluoroscopy are useful in guiding proper screw placement. Close attention should be paid to preparation of the screw entry site.

Adult↗
PubMed2005

Nonoperative management of vertical C2 body fractures.

OBJECTIVE: To estimate the incidence and to describe the clinical results of the nonoperative management of vertical C2 body fractures. METHODS: An 8-year retrospective review of upper cervical spine injuries from the registry of a level I trauma center identified 21 patients with a vertical C2 body fracture. RESULTS: Sixteen coronally oriented Type 1 vertical C2 body fractures and 5 sagittally oriented Type 2 vertical C2 body fractures were identified. These fractures account for approximately 10% of the upper cervical spine fractures identified over this period of time. One elderly patient with a Type 1 fracture died as a result of pneumonia, and two patients with Type 2 fractures died from severe closed-head injuries. One patient had evidence of spinal cord injury. This was not related to the C2 body fracture but rather to a subaxial cervical spine injury. Of the surviving 18 patients, all were managed nonoperatively (with external orthoses) and showed evidence of fusion (union of fracture fragments) at the time of the last follow-up. CONCLUSION: Vertical C2 body fractures are not rare injuries and can account for up to 10% of upper cervical spine injuries. In general, vertical C2 body fractures are amenable to nonoperative treatment with external orthoses.

Accidents, Traffic↗
PubMed2004

Multiple points of interaction between retinoic acid and FGF signaling during embryonic axis formation.

Anteroposterior (AP) patterning of the developing CNS is crucial for both regional specification and the timing of neurogenesis. Several important factors are involved in AP patterning, including members of the WNT and FGF growth factor families, retinoic acid receptors, and HOX genes. We have examined the interactions between FGF and retinoic signaling pathways. Blockade of FGF signaling downregulates the expression of members of the RAR signaling pathway, RARalpha, RALDH2 and CYP26. Overexpression of a constitutively active RARalpha2 rescues the effects of FGF blockade on the expression of XCAD3 and HOXB9. This suggests that RARalpha2 is required as a downstream target of FGF signaling for the posterior expression of XCAD3 and HOXB9. Surprisingly, we found that posterior expression of FGFR1 and FGFR4 was dependent on the expression of RARalpha2. Anterior expression was also altered with FGFR1 expression being lost, whereas FGFR4 expression was expanded beyond its normal expression domain. RARalpha2 is required for the expression of XCAD3 and HOXB9, and for the ability of XCAD3 to induce HOXB9 expression. We conclude that RARalpha2 is required at multiple points in the posteriorization pathway, suggesting that correct AP neural patterning depends on a series of mutually interactive feedback loops among FGFs, RARs and HOX genes.

Aldehyde Dehydrogenase 1 Family↗
PubMed2006

Ets2 is necessary in trophoblast for normal embryonic anteroposterior axis development.

Although the trophoblast is necessary for the growth, viability and patterning of the mammalian embryo, understanding of its patterning role is still rudimentary. Expression of the transcription factor Ets2 is restricted to the trophoblast in early postimplantation stages and Ets2 mutants have been previously shown to have defects in trophoblast development. We show here that Ets2 is necessary in the trophoblast for fundamental aspects of anteroposterior (AP) epiblast axis initiation, including mesoderm initiation at the primitive streak, establishment of posterior character in the epiblast and appropriate spatial restriction of the anterior visceral endoderm (AVE). Most homozygous Ets2 mutants also show highly reduced development of the trophoblast with an absence of extraembryonic ectoderm (EXE) markers. Embryos in which the EXE has been physically removed before culture in vitro phenocopy the patterning defects of Ets2 mutants. These defects cannot be rescued by providing Ets2 mutants with wild-type epiblast in tetraploid aggregations. Thus, EXE-derived signals are necessary for normal embryonic patterning. Ets2 is likely to be required in the EXE downstream of epiblast signals, such as Fgf, and, in turn, helps to regulate signals from the EXE that signal back to the epiblast to promote proper primitive streak and AVE development. This study provides new insights about the genetic and cellular basis of the patterning role and development of the early trophoblast.

Animals↗
PubMed2006

The left-right axis in the mouse: from origin to morphology.

The past decade or so has seen rapid progress in our understanding of how left-right (LR) asymmetry is generated in vertebrate embryos. However, many important questions about this process remain unanswered. Although a leftward flow of extra-embryonic fluid in the node cavity (nodal flow) is likely to be the symmetry-breaking event, at least in the mouse embryo, it is not yet known how this flow functions or how the asymmetric signal generated in the node is transferred to the lateral plate. The final step in left-right patterning - translation of the asymmetric signal into morphology - is also little understood.

Amniotic Fluid↗
PubMed1996

Maternal beta-catenin establishes a 'dorsal signal' in early Xenopus embryos.

In previous work, we demonstrated that maternally encoded beta-catenin, the vertebrate homolog of armadillo, is required for formation of dorsal axial structures in early Xenopus embryos (Heasman, J., Crawford, A., Goldstone, K., Garner-Hamrick, P., Gumbiner, B., Kintner, C., Yoshida-Noro, C. and Wylie, C. (1994). Cell 79, 791-803). Here we investigated, firstly, the role(s) of beta-catenin in spatial terms, in different regions of the embryo, by injecting beta-catenin mRNA into individual blastomeres of beta-catenin-depleted embryos at the 32 cell stage. The results indicate that beta-catenin can rescue the dorsal axial structures in a non-cell-autonomous way and without changing the fates of the injected cells. This suggests that cells overexpressing beta-catenin send a 'dorsal signal' to other cells. This was confirmed by showing that beta-catenin overexpressing animal caps did not cause wild-type caps to form mesoderm, but did cause isolated beta-catenin-deficient marginal zones to form dorsal mesoderm. Furthermore beta-catenin-deficient vegetal masses treated with overexpressing caps regained their ability to act as Nieuwkoop Centers. Secondly, we studied the temporal activity of beta-catenin. We showed that zygotic transcription of beta-catenin starts after the midblastula transition (MBT), but does not rescue dorsal axial structures. We further demonstrated that the vegetal mass does not release a dorsal signal until after the onset of transcription, at the midblastula stage, suggesting that maternal beta-catenin protein is required at or before this time. Thirdly we investigated where, in relationship to other gene products known to be active in axis formation, beta-catenin is placed. We find that BVg1, bFGF, tBR (the truncated form of BMP2/4R), siamois and noggin activities are all downstream of beta-catenin, as shown by the fact that injection of their mRNAs rescues the effect of depleting maternally encoded beta-catenin. Interference with the action of glycogen synthase kinase (GSK), a vertebrate homolog of the Drosophila gene product, zeste white 3 kinase, does not rescue the effect, suggesting that it is upstream.

Animals↗
PubMed1996

Early gene expression along the animal-vegetal axis in sea urchin embryoids and grafted embryos.

The HE gene is the earliest strictly zygotic gene activated during sea urchin embryogenesis. It is transiently expressed in a radially symmetrical domain covering the animal-most two-thirds of the blastula. The border of this domain, which is orthogonal to the primordial animal-vegetal axis, is shifted towards the animal pole in Li+-treated embryos. Exogenous micromeres implanted at the animal pole of whole embryos, animal or vegetal halves do not modify the extent and localization of the HE expression domain. In grafted embryos or animal halves, the Li+ effect is not affected by the presence of ectopic micromeres at the animal pole. A Li+-induced shift of the border, similar to that seen in whole embryos, occurs in embryoids developing from animal halves isolated from 8-cell stage embryos or dissected from unfertilised eggs. Therefore, the spatial restriction of the HE gene is not controlled by the inductive cascade emanating from the micromeres and the patterning along the AV-axis revealed by Li+ does not require interactions between cells from the animal and vegetal halves. This suggests that maternal primary patterning in the sea urchin embryo is not limited to a small vegetal center but extends along the entire AV axis.

Animals↗