Posterior Expansion Research Articles

The effects of Quaternary glaciations in Patagonia as evidenced by chloroplast DNA phylogeography of Southern beech Nothofagus obliqua

Climatic oscillations during the Quaternary strongly affected the distribution of warm-temperate tree species, which experienced local restrictions into ice-free areas and posterior expansions. To evaluate the impact of these range movements on the genetic structure of populations, we performed a phylogeographical analysis of the species Nothofagus obliqua with chloroplast DNA markers. A total of 27 populations covering the whole natural distribution range were analyzed using polymerase chain reaction-restriction fragment length polymorphism. Diversity (hT, hS), allelic richness (rg), and differentiation among populations for unordered (GST) and ordered alleles (NST) were calculated. The relationships among haplotypes were evaluated by the construction of a minimum spanning network. The spatial distribution of the genetic variation was analyzed through a Mantel test and with a nested analysis of molecular variance to differentiate between geographic regions. The screening of 11 non-coding regions allowed the identification of 14 haplotypes. A high genetic differentiation was detected (NST = 0.875 and GST = 0.824) with the existence of phylogeographic structure (p < 0.05). The distribution of the genetic variation was partially explained by the topography of the region when the populations were divided longitudinally into Coastal Mountains, Central Valley, and Andes Mountains (ϕRT = 0.093, p = 0.001). In agreement with pollen records, our results support the hypothesis of Coastal refuges since the region harbors high diversity together with older and private haplotypes. Long-lasting persistence of some Coastal populations without contribution to re-colonization is proposed. Additional refuges are also postulated along the Andes and Longitudinal Valley. Survival in multiple glacial refuges is discussed together with the possible migratory routes.

Transverse maxillary stability assisted by a transpalatal device: A retrospective pilot study of 9 cases

This retrospective pilot study assessed the transverse stability of an original surgical approach in nine patients with moderate transverse maxillary deficiency associated with a sagittal and/or vertical skeletal anomaly. During the one-stage surgical procedure, bi- or three-dimensional anomalies were corrected. Maxillary expansion was guided by a transpalatal bone-anchored device (TPD). Expansion measurements were made 1-2 months before surgery, 6 and at least 12 months after surgery. The transverse occlusion was corrected in all cases. After 12 months the gingival landmarks revealed an expansion range from -0.83 to +2.92 mm for the cuspids, +1.66 to +6.23 mm for the bicuspids and from +2.68 to +4.80 mm for the molars. For the occlusal landmarks, expansion ranged from -2.01 to +3.15 mm (cuspids), from +1.11 to +7.13 mm (bicuspids) and from +2.70 to +6.26 mm (molars). Cuspid expansion was significantly smaller than that of bicuspids and molars. This more posterior expansion was achieved through the surgical procedure. The transverse stability obtained with the aid of the bone-anchored TPD was satisfying. This preliminary study supports the principle of an original surgical approach, called 'Le Fort I--TPD', which combines a Le Fort I osteotomy with a controlled maxillary expansion.

The role of early development in mammalian limb diversification: A descriptive comparison of early limb development between the natal long‐fingered bat (Miniopterus natalensis) and the mouse (Mus musculus)

Comparative embryology expands our understanding of unique limb structures, such as that found in bats. Bat forelimb digits 2 to 5 are differentially elongated and joined by webbing, while the hindlimb digits are of similar length in many species. We compare limb development between the mouse and the Natal long-fingered bat, Miniopterus natalensis, to pinpoint the stage at which their limbs begin to differ. The bat forelimb differs from the mouse at Carollia stage (CS) 14 with the appearance of the wing membrane primordia. This difference is enhanced at CS 15 with the posterior expansion of the hand plate. The bat hindlimb begins to differ from the mouse between CS 15 and 16 when the foot plate undergoes a proximal expansion resulting in digit primordia of very similar length. Our findings support recent gene expression studies, which reveal a role for early patterning in the development of the bat limb.

Aterectomia rotacional para o tratamento da reestenose intrastent

Relatamos o caso de um paciente com reestenose de stent nao-farmacologico, secundaria a hipoexpansao da protese, decorrente de grave calcificacao da placa aterosclerotica subjacente, a qual nao foi adequadamente reconhecida na angiografia. A utilizacao do ultrassom intracoronario foi de grande importância para reconhecer o mecanismo da reestenose e orientar na escolha da estrategia intervencionista mais adequada. A aterectomia rotacional foi realizada com sucesso para debilitar o calcio peristent, permitindo a expansao posterior da protese com baloes de alta pressao.

Towards a synthetic view of axis specification mechanisms in vertebrates: insights from the dogfish

The genetic mechanisms, which control axis specification, apparently extensively diverge across vertebrates. In amphibians and teleosts, they are tightly linked to the establishment of an early dorso-ventral polarity. This polarity has no equivalent in amniotes, which unlike the former, retain a considerable plasticity for their site of axis formation until blastula stages and rely on signals secreted by extra-embryonic tissues for the establishment of their early rostro-caudal pattern. In order to better understand the links between these seemingly highly divergent mechanisms, we have used an evo-devo approach, aimed at reconstructing the gnathostome ancestral state and focussed on a chondrichthyan, the dogfish Scyliorhinus canicula. A detailed molecular characterization of the dogfish embryo at blastula and gastrula stages highlights striking similarities with all vertebrate model organisms including amniotes. It suggests the presence in the dogfish of territories homologous to the hypoblast and extra-embryonic ectoderm of the latter, which may therefore reflect the primitive condition of jawed vertebrates. In the ancestral state, these territories are specified at opposite sides of an early axis of bilateral symmetry, homologous to the dorso-ventral axis of amphibians and teleosts, and aligned with the later forming embryonic axis, from head to tail. Amniotes have diverged from this pattern through a posterior expansion of extra-embryonic ectoderm, resulting in an apparently radial symmetry at late blastula stages. These data delineate the broad outlines of the gnathostome ancestral pattern of axis specification and highlight an unexpected unity of mechanisms across jawed vertebrates. They illustrate the complementarity of comparative and genetic approaches for a comprehensive view of developmental mechanisms themselves. To cite this article: M. Coolen et al., C. R. Biologies 332 (2009).

Surgically assisted rapid maxillary expansion: long-term stability

The purpose of this study was to evaluate treatment outcomes and long-term stability in patients treated by surgically assisted rapid maxillary expansion (SARME) and to compare the results with a matched, untreated control group. The sample comprised consecutive study models from 31 subjects (17 males and 14 females) with a mean pre-treatment age of 25.9 years [standard deviation (SD) 9.6]. The mean follow-up time was 6.4 years (SD 3.3). The transverse distances between the maxillary canines and maxillary first molars were measured with digital sliding callipers before treatment (T0), after treatment (T1), and at follow-up (T2). The data were analysed with a Mann-Whitney U, Spearman's rho, and Wilcoxon signed-rank tests. At T1, all posterior crossbites were corrected and the expansions were statistically significant. At T2, despite some reduction in the transverse measurements, the posterior crossbites remained corrected. There were no statistically significant differences between the treatment and control groups at T2 regarding transverse measurements, except for the distance between the mesio-buccal cusp tips of the maxillary first molars. In the treatment group, there was no significant difference in terms of reductions in the transverse dimensions over the short- or long-term, no significant correlations between age or gender and the decrease in transverse dimensions or between the degree of anterior and posterior expansion. There were no significant correlations between the degree of expansion and subsequent post-treatment decrease. The results indicate that SARME normalizes the transverse discrepancies and is stable a mean of 6 years post-treatment. The decreases in the transverse dimensions are most pronounced during the first 3 years post-treatment.

Cranial Vault Expansion in the Management of Postshunt Craniosynostosis and Slit Ventricle Syndrome

Slit ventricle syndrome and postshunt craniosynostosis are uncommon complications after shunting procedures for congenital hydrocephalus. Slit ventricle syndrome occurs as a complication in 1 to 5 percent of patients after shunting procedures for hydrocephalus during infancy. These patients usually have had a shunt in place for years, with overdrainage of cerebrospinal fluid resulting in very small ventricles. Excessive intracranial decompression may result in ventricular collapse with the formation of slit-like ventricles and cranial vault collapse with secondary craniosynostosis. A retrospective review of 12 patients who had undergone cranial vault expansion for management of postshunt craniosynostosis and slit ventricle syndrome refractory to other treatment modalities was performed. All patients had initially been shunted for congenital hydrocephalus and subsequently underwent a mean of 4.9 shunt revisions before cranial vault expansion. All 12 patients demonstrated decreased ventricular volume, with noncompliant slit-like ventricles in nine of these patients. Five patients demonstrated pancraniosynostosis, three patients demonstrated multiple sutural fusion, and isolated sagittal synostosis occurred in two patients. Two patients appeared to have "functional" synostoses with narrowed, overlapping sutures that were not actually fused. Eleven patients underwent bilateral fronto-orbital advancement with frontotemporoparietal expansion; one patient underwent only posterior vault expansion. Seven of the 12 patients required a mean of 2.3 shunt revisions after cranial vault expansion; five patients did not require subsequent revisions. Improvement in cranial vault shape was achieved in all 12 patients, as was improvement of neurologic symptoms in nine of the 12 patients. Cranial vault expansion is a useful approach in the management of the restricted cranium associated with slit ventricle syndrome and postshunt craniosynostosis. This approach resulted in a decreased need for shunt revisions and improvement of neurologic symptoms and cranial vault shape.

Suction generation in white-spotted bamboo sharksChiloscyllium plagiosum

After the divergence of chondrichthyans and teleostomes, the structure of the feeding apparatus also diverged leading to alterations in the suction mechanism. In this study we investigated the mechanism for suction generation during feeding in white-spotted bamboo sharks, Chiloscyllium plagiosum and compared it with that in teleosts. The internal movement of cranial elements and pressure in the buccal, hyoid and pharyngeal cavities that are directly responsible for suction generation was quantified using sonomicrometry and pressure transducers. Backward stepwise multiple linear regressions were used to explore the relationship between expansion and pressure, accounting for 60-96% of the variation in pressure among capture events. The progression of anterior to posterior expansion in the buccal, hyoid and pharyngeal cavities is accompanied by the sequential onset of subambient pressure in these cavities as prey is drawn into the mouth. Gape opening triggers the onset of subambient pressure in the oropharyngeal cavities. Peak gape area coincides with peak subambient buccal pressure. Increased velocity of hyoid area expansion is primarily responsible for generating peak subambient pressure in the buccal and hyoid regions. Pharyngeal expansion appears to function as a sink to receive water influx from the mouth, much like that of compensatory suction in bidirectional aquatic feeders. Interestingly, C. plagiosum generates large suction pressures while paradoxically compressing the buccal cavity laterally, delaying the time to peak pressure. This represents a fundamental difference from the mechanism used to generate suction in teleost fishes. Interestingly, pressure in the three cavities peaks in the posterior to anterior direction. The complex shape changes that the buccal cavity undergoes indicate that, as in teleosts, unsteady flow predominates during suction feeding. Several kinematic variables function together, with great variation over long gape cycles to generate the low subambient pressures used by C. plagiosum to capture prey.

Retinoic acid controls heart anteroposterior patterning by down‐regulating Isl1 through the Fgf8 pathway

Distinct progenitor cell populations exist in cardiac mesoderm important for patterning of the heart. During heart tube formation in mouse, Tbx5 is expressed in progenitors located more laterally, whereas Isl1 and Fgf8 are expressed in progenitors located more medially. Signals that drive mesodermal progenitors into various cardiac lineages include Fgf8, which functions to induce Isl1. Studies in chick and zebrafish have shown that retinoic acid restricts the number of cardiac progenitors, but its role in mammalian cardiac development is unclear. Here, we demonstrate that Raldh2(-/-) mouse embryos lacking retinoic acid signaling exhibit a posterior expansion of the cardiac Fgf8 expression domain as well as an expansion of Isl1 expression into mesoderm lying posterior to the cardiac field. We provide evidence that retinoic acid acts specifically in the posterior-medial region of the cardiac field to establish the heart posterior boundary potentially by reducing Fgf8 expression which restricts the Isl1 domain.

Branchial arch muscle innervation by the glossopharyngeal (IX) and vagal (X) nerves in Tetraodontiformes, with special reference to muscle homologies

Branchial arch muscle innervation by the glossopharyngeal (IX) and vagal (X) nerves in 10 tetraodontiform families and five outgroup taxa was examined, with special reference to muscle homologies. Basic innervation patterns and their variations were described for all muscle elements (except gill filament muscles). In the tetraodontids Takifugu poecilonotus and Canthigaster rivulata, diodontid Diodon holocanthus, and molid Mola mola, levator externus 4 was innervated by the 3rd vagal branchial trunk (BX3) in addition to BX2, owing to strong posterior expansion of the muscle. Based on nerve innervation, migrations of the muscle attachment sites (i.e., origins and insertions) were recognized in levator internus 2 (in Mola mola), obliquus dorsalis 3 (in Ostracion immaculatus and Canthigaster rivulata), and obliquus ventralis 2 (in Stephanolepis cirrhifer), muscle topologies not necessarily being indicative of homologies. Embryonic origin of the retractor dorsalis and parallel attainment of the swimbladder muscle within the order were also discussed.

Retinoic acid deficiency alters second heart field formation

Retinoic acid (RA), the active derivative of vitamin A, has been implicated in various steps of cardiovascular development. The retinaldehyde dehydrogenase 2 (RALDH2) enzyme catalyzes the second oxidative step in RA biosynthesis and its loss of function creates a severe embryonic RA deficiency. Raldh2(-/-) knockout embryos fail to undergo heart looping and have impaired atrial and sinus venosus development. To understand the mechanism(s) producing these changes, we examined the contribution of the second heart field (SHF) to pharyngeal mesoderm, atria, and outflow tract in Raldh2(-/-) embryos. RA deficiency alters SHF gene expression in two ways. First, Raldh2(-/-) embryos exhibited a posterior expansion of anterior markers of the SHF, including Tbx1, Fgf8, and the Mlc1v-nlacZ-24/Fgf10 reporter transgene as well as of Islet1. This occurred at early somite stages, when cardiac defects became irreversible in an avian vitamin A-deficiency model, indicating that endogenous RA is required to restrict the SHF posteriorly. Explant studies showed that this expanded progenitor population cannot differentiate properly. Second, RA up-regulated cardiac Bmp expression levels at the looping stage. The contribution of the SHF to both inflow and outflow poles was perturbed under RA deficiency, creating a disorganization of the heart tube. We also investigated genetic cross-talk between Nkx2.5 and RA signaling by generating double mutant mice. Strikingly, Nkx2.5 deficiency was able to rescue molecular defects in the posterior region of the Raldh2(-/-) mutant heart, in a gene dosage-dependent manner.

Posterior skull expansion—Indications, methods complications and development

Posterior skull expansion—Indications, methods complications and development

Repression of the hindbrain developmental program by Cdx factors is required for the specification of the vertebrate spinal cord

The spinal cord is a unique vertebrate feature that originates, together with the hindbrain, from the caudal neural plate. Whereas the hindbrain subdivides into rhombomeres, the spinal cord remains unsegmented. We have identified Cdx transcription factors as key determinants of the spinal cord region in zebrafish. Loss of Cdx1a and Cdx4 functions causes posterior expansion of the hindbrain at the expense of the unsegmented spinal cord. By contrast, cdx4 overexpression in the hindbrain impairs rhombomere segmentation and patterning and induces the expression of spinal cord-specific genes. Using cell transplantation, we demonstrate that Cdx factors function directly within the neural ectoderm to specify spinal cord. Overexpression of 5' Hox genes fails to rescue hindbrain and spinal cord defects associated with cdx1a/cdx4 loss-of-function, suggesting a Hox-independent mechanism of spinal cord specification. In the absence of Cdx function, the caudal neural plate retains hindbrain characteristics and remains responsive to surrounding signals, particularly retinoic acid, in a manner similar to the native hindbrain. We propose that by preventing the posterior-most region of the neural plate from following a hindbrain developmental program, Cdx factors help determine the size of the prospective hindbrain and spinal cord territories.

34th Annual Scientific Meeting of the Association of Paediatric Anaesthetists of Great Britain and Ireland, 8?10 March 2007, Manchester. A comparison of the laryngeal mask airway with facemask and oropharyngeal airway for manual ventilation by critical care nurses in children

Introduction: The European Resuscitation Council recommends the laryngeal mask airway (LMA) for manual ventilation in adult resuscitation if the skills required for the placement of a tracheal tube are unavailable or intubation proves impossible (1). This followed concerns about the ability of inexperienced personnel to provide manual ventilation using traditional facemask and oropharyngeal airway (FM/OA). If inadequate FM/OA ventilation also occurs in children, the LMA may improve airway management during resuscitation. Methods: Local ethical approval was obtained. We trained 19 nurses, experienced in paediatric intensive care, emergency medicine or anaesthetics in the use of the LMA on manikins. They all had prior experience in FM/OA ventilation. Children undergoing elective surgery were studied. Anaesthesia was induced with propofol (3–5 mg·kg−1) or sevoflurane (8% in oxygen/nitrous oxide) followed by a continuous infusion of propofol/remifentanil to produce apnoea. Standard monitoring was applied and an ultrasound sensor placed above the xiphisternum to measure anterior posterior (AP) chest expansion. The consultant paediatric anaesthetist manually ventilated the lungs using FM/OA. The AP chest expansion achieved was defined as the gold standard. The nurse then inserted each airway device in random order and chest expansion was compared with the gold standard. A maximum of three attempts was allowed for each airway device. Prior to the study commencing adequate ventilation was defined as successful if 60% or more of the ‘gold standard’ AP chest expansion was achieved. Results: The 60 children studied had a median age of 4 years (range 7 months–8 years), and median weight of 17 kg (range 8–41 kg). Using an LMA the nurses achieved successful ventilation in 78% of children compared with 71% in the FM/OA group (P = 0.39, chi-squared test). The LMA was inserted successfully at the 1st attempt in 60%, 2nd attempt in 11% and 3rd attempt in 6% of children. Median time to first successful breath was 38 s (range 11–147 s) for the LMA and 24 s (range 15–48 s) for the FM/GA. (Figure 1). Figure 1. A cumulative frequency plot of the time to first successful ventilation using the laryngeal mask airway or face mask and oropharyngeal airway. Download figure to PowerPoint Discussion: Critical care nurses can be trained to provide successful ventilation in 78% of children using an LMA. Similar studies in adults have shown a higher proportion of successful LMA insertions than this but the proportion of children successfully ventilated using FM/OA (70%) was higher than in adult studies. This may be because FM/OA ventilation is easier in children. Time to successful ventilation was faster in the FM/OA group than the LMA group, similar to adult studies. In this group of nurses the LMA may not usefully improve the proportion of children ventilated successfully compared with FM/OA. Acknowledgements: This study received funding from the Resuscitation Council (UK). Reference 1 Baskett P. Guidelines for the advanced management of the airway and ventilation during resuscitation. A statement by the Airway and Ventilation Management of the Working Group of the European Resuscitation Council. Resuscitation 1996: 31: 201–230.

Wnt signaling is required for antero-posterior patterning of the planarian brain

Wnt signaling functions in axis formation and morphogenesis in various animals and organs. Here we report that Wnt signaling is required for proper brain patterning during planarian brain regeneration. We showed here that one of the Wnt homologues in the planarian Dugesia japonica, DjwntA, was expressed in the posterior region of the brain. When DjwntA-knockdown planarians were produced by RNAi, they could regenerate their heads at the anterior ends of the fragments, but formed ectopic eyes with irregular posterior lateral branches and brain expansion. This suggests that the Wnt signal may be involved in antero-posterior (A–P) patterning of the planarian brain, as in vertebrates. We also investigated the relationship between the DjwntA and nou-darake/FGFR signal systems, as knockdown planarians of these genes showed similar phenotypes. Double-knockdown planarians of these genes did not show any synergistic effects, suggesting that the two signal systems function independently in the process of brain regeneration, which accords with the fact that nou-darake was expressed earlier than DjwntA during brain regeneration. These observations suggest that the nou-darake/FGFR signal may be involved in brain rudiment formation during the early stage of head regeneration, and subsequently the DjwntA signal may function in A–P patterning of the brain rudiment.

Posterior Cranial Fossa Box Expansion Leads to Resolution of Symptomatic Cerebellar Ptosis Following Chiari I Malformation Repair

Chiari I malformation occurs when the cerebellar tonsils herniate downward through the foramen magnum into the upper cervical spinal canal. If the posterior fossa craniectomy during corrective surgery leads to excessive enlargement of the foramen magnum, the complication of cerebellar ptosis may result. To treat this difficult problem a posterior cranial fossa box expansion was devised and studied. Patients who developed symptomatic cerebellar ptosis (confirmed by MRI) following cranial vault decompression for Chiari I malformations underwent a posterior fossa box expansion (n=7). This procedure involved coverage of posterior aspect of the enlarged foramen magnum with a split-thickness calvarial bone graft box. The box reconstruction provided separation between the neck musculature, soft tissues from the neural tissue; prevention of cerebellar prolapse; and expansion of the posterior cranial vault. Patients had a mean of 12+/-1 months between initial suboccipital craniectomy and confirmation of symptomatic cerebellar ptosis. Mean age at the time of posterior fossa box reconstruction was 31+/-9 years (range of 14 to 44 years). Preoperative symptoms of headache (7/7, 100%), upper extremity numbness (5/7, 71%) or paresthesias (3/7, 43%), respiratory disturbance (2/7, 29%) and inability to walk (2/7, 29%) improved in all patients postoperatively. At more than 12 month follow-up 6/7 patients (86%) were both disease-free (MRI confirmation) and symptom-free. One out of seven patients had return of headache in a more mild form. Thus, in our patient group the posterior fossa box reconstruction led to resolution of symptomatic cerebellar ptosis following Chiari I malformation repair.

Efficient amplification of melanoma-specific CD8+ T cells using artificial antigen presenting complex

In vitro large amplification of tumor-specific cytotoxic T lymphocytes (CTLs) and adoptive transfer of these cells is one of the most promising approaches to treat malignant diseases in which an effective immune response is not achieved by active immunization. However, generating sufficient numbers of tumor-specific CTLs stimulated with autologous antigen presenting cells (APCs) in vitro is one of the most problematic steps in the adoptive cell transfer (ACT) therapy. To circumvent this problem, we have developed an artificial antigen presenting complex (aAPCs) using MHC class I molecules loaded with a melanoma-specific TRP-2 peptide epitope. Our results show that TRP-2-specific CD8+ T cells elicited by immunization with recombinant adenovirus expressing the mini-gene epitope are efficiently stimulated and amplified in vitro to a greater extent by aAPCs than by natural splenic APCs. These aAPC-induced CTLs recognized endogenously processed antigens present on B16F10 melanoma cells. Efficient stimulation and proliferation of antigen- specific T cells was also confirmed using ovalbumin peptide-loaded aAPCs and OT-I TCR transgenic cells. These results demonstrate that prior in vivo immunization, which increases the precursor frequency, simplifies posterior expansion of tumor- specific CD8+ T cells, and aAPCs is superior to autologous APC for in vitro amplification. This "prime and expand" regimen can be an alternative method for large amplification of rare tumor-specific CTLs and aAPCs should be a useful tool for ACT immunotherapy.

Segregation of telencephalic and eye-field identities inside the zebrafish forebrain territory is controlled by Rx3

Anteroposterior patterning of the vertebrate forebrain during gastrulation involves graded Wnt signaling, which segregates anterior fields (telencephalon and eye) from the diencephalon. How the telencephalic and retinal primordia are subsequently subdivided remains largely unknown. We demonstrate that at late gastrulation the Paired-like homeodomain transcription factor Rx3 biases cell specification choices towards the retinal fate within a population of bipotential precursors of the anterior forebrain: direct cell tracing demonstrates that retinal precursors acquire a telencephalic fate in embryos homozygous for the rx3-null allele ckh(ne2611), characterized by an enlarged telencephalon and a lack of eyes. Chimera analyses further indicate that this function of Rx3 is cell autonomous. Transfating of the eye field in the absence of Rx3 function correlates with a substantial posterior expansion of expression of the Wnt antagonist Tlc and the winged-helix transcription factor Foxg1. These results suggest that the process segregating the telencephalic and eye fields is isolated from diencephalic patterning, and is mediated by Rx3.

Neural and optical limits to visual performance in myopia

We investigated the relative importance of neural and optical limitations to visual performance in myopia. A number of visual performance measures were made on all or subsets of 121 eyes of emmetropic and myopic volunteers aged 17–35 years. These tests included visual measures that are mainly neurally limited (spatial summation out to ±30° in the horizontal visual field and resolution acuity out to ±10° in the horizontal visual field) and central ocular aberrations. We found that myopia affected the neurally limited tests, but had little effect on central higher order aberration. The critical area for spatial summation increased in the temporal visual field at 0.03 log units/dioptre of myopia. Resolution acuity decreased at approximately 0.012 log units/dioptre of myopia. Losses of visual function were slightly greater in the temporal than in the nasal visual field. The observed visual deficit in myopia can be explained by either global retinal expansion with some post-receptor loss (e.g. ganglion cell death) or a posterior polar expansion in which the point about which expansion occurs is near the centre of the previously emmetropic globe.

Expansion maxillaire assistée par distracteur tranpalatin et ostéotomie de Le Fort I d’impaction postérieure, en un seul temps

The transpalatal distractor (TPD", Surgi-Tec, Bruges, Belgium) is a bone support device whose transversal expansion effect is well known in teenagers at the end of their growth and in adults. Surgical assisted rapid palatal expansion is usually carried out before the orthodontic treatment phase. The transversal gain is mainly seen at the anterior level, and can avoid, in some cases, extraction of bicuspids. It is difficult to correct a sizeable posterior transversal deficit using this technique, and patients presenting a complex dismorphosis must go through a second surgical phase to correct the vertical and sagittal abnormalities at the end of the orthodontic preparation. We describe a clinical case of posterior transversal surgical expansion, associated with posterior impaction of the maxilla, in one stage, at the end of orthodontic preparation. The osteotomies, the positioning of the distractor and the orthodontic apparatus enable the palatal transversal expansion to be modulated as required. The advantages and limitations of this therapeutic technique are discussed.