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Trevor H. Worthy - One of the best experts on this subject based on the ideXlab platform.
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The phylogenetic significance of the morphology of the Syrinx, hyoid and larynx, of the southern cassowary, Casuarius casuarius (Aves, Palaeognathae).
BMC evolutionary biology, 2019Co-Authors: Phoebe Louise Mcinerney, Mike S. Y. Lee, Alice M. Clement, Trevor H. WorthyAbstract:Palaeognathae is a basal clade within Aves and include the large and flightless ratites and the smaller, volant tinamous. Although much research has been conducted on various aspects of palaeognath morphology, ecology, and evolutionary history, there are still areas which require investigation. This study aimed to fill gaps in our knowledge of the Southern Cassowary, Casuarius casuarius, for which information on the skeletal systems of the Syrinx, hyoid and larynx is lacking - despite these structures having been recognised as performing key functional roles associated with vocalisation, respiration and feeding. Previous research into the Syrinx and hyoid have also indicated these structures to be valuable for determining evolutionary relationships among neognath taxa, and thus suggest they would also be informative for palaeognath phylogenetic analyses, which still exhibits strong conflict between morphological and molecular trees. The morphology of the Syrinx, hyoid and larynx of C. casuarius is described from CT scans. The Syrinx is of the simple tracheo-bronchial Syrinx type, lacking specialised elements such as the pessulus; the hyoid is relatively short with longer ceratobranchials compared to epibranchials; and the larynx is comprised of entirely cartilaginous, standard avian anatomical elements including a concave, basin-like cricoid and fused cricoid wings. As in the larynx, both the Syrinx and hyoid lack ossification and all three structures were most similar to Dromaius. We documented substantial variation across palaeognaths in the skeletal character states of the Syrinx, hyoid, and larynx, using both the literature and novel observations (e.g. of C. casuarius). Notably, new synapomorphies linking Dinornithiformes and Tinamidae are identified, consistent with the molecular evidence for this clade. These shared morphological character traits include the ossification of the cricoid and arytenoid cartilages, and an additional cranial character, the articulation between the maxillary process of the nasal and the maxilla. Syrinx, hyoid and larynx characters of palaeognaths display greater concordance with molecular trees than do other morphological traits. These structures might therefore be less prone to homoplasy related to flightlessness and gigantism, compared to typical morphological traits emphasised in previous phylogenetic studies.
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The phylogenetic significance of the morphology of the Syrinx, hyoid and larynx, of the southern cassowary, Casuarius casuarius (Aves, Palaeognathae)
BMC Evolutionary Biology, 2019Co-Authors: Phoebe Louise Mcinerney, Mike S. Y. Lee, Alice M. Clement, Trevor H. WorthyAbstract:Background Palaeognathae is a basal clade within Aves and include the large and flightless ratites and the smaller, volant tinamous. Although much research has been conducted on various aspects of palaeognath morphology, ecology, and evolutionary history, there are still areas which require investigation. This study aimed to fill gaps in our knowledge of the Southern Cassowary, Casuarius casuarius , for which information on the skeletal systems of the Syrinx, hyoid and larynx is lacking - despite these structures having been recognised as performing key functional roles associated with vocalisation, respiration and feeding. Previous research into the Syrinx and hyoid have also indicated these structures to be valuable for determining evolutionary relationships among neognath taxa, and thus suggest they would also be informative for palaeognath phylogenetic analyses, which still exhibits strong conflict between morphological and molecular trees. Results The morphology of the Syrinx, hyoid and larynx of C. casuarius is described from CT scans. The Syrinx is of the simple tracheo-bronchial Syrinx type, lacking specialised elements such as the pessulus; the hyoid is relatively short with longer ceratobranchials compared to epibranchials; and the larynx is comprised of entirely cartilaginous, standard avian anatomical elements including a concave, basin-like cricoid and fused cricoid wings. As in the larynx, both the Syrinx and hyoid lack ossification and all three structures were most similar to Dromaius. We documented substantial variation across palaeognaths in the skeletal character states of the Syrinx, hyoid, and larynx, using both the literature and novel observations (e.g. of C. casuarius ). Notably, new synapomorphies linking Dinornithiformes and Tinamidae are identified, consistent with the molecular evidence for this clade. These shared morphological character traits include the ossification of the cricoid and arytenoid cartilages, and an additional cranial character, the articulation between the maxillary process of the nasal and the maxilla. Conclusion Syrinx, hyoid and larynx characters of palaeognaths display greater concordance with molecular trees than do other morphological traits. These structures might therefore be less prone to homoplasy related to flightlessness and gigantism, compared to typical morphological traits emphasised in previous phylogenetic studies.
Phoebe Louise Mcinerney - One of the best experts on this subject based on the ideXlab platform.
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The phylogenetic significance of the morphology of the Syrinx, hyoid and larynx, of the southern cassowary, Casuarius casuarius (Aves, Palaeognathae).
BMC evolutionary biology, 2019Co-Authors: Phoebe Louise Mcinerney, Mike S. Y. Lee, Alice M. Clement, Trevor H. WorthyAbstract:Palaeognathae is a basal clade within Aves and include the large and flightless ratites and the smaller, volant tinamous. Although much research has been conducted on various aspects of palaeognath morphology, ecology, and evolutionary history, there are still areas which require investigation. This study aimed to fill gaps in our knowledge of the Southern Cassowary, Casuarius casuarius, for which information on the skeletal systems of the Syrinx, hyoid and larynx is lacking - despite these structures having been recognised as performing key functional roles associated with vocalisation, respiration and feeding. Previous research into the Syrinx and hyoid have also indicated these structures to be valuable for determining evolutionary relationships among neognath taxa, and thus suggest they would also be informative for palaeognath phylogenetic analyses, which still exhibits strong conflict between morphological and molecular trees. The morphology of the Syrinx, hyoid and larynx of C. casuarius is described from CT scans. The Syrinx is of the simple tracheo-bronchial Syrinx type, lacking specialised elements such as the pessulus; the hyoid is relatively short with longer ceratobranchials compared to epibranchials; and the larynx is comprised of entirely cartilaginous, standard avian anatomical elements including a concave, basin-like cricoid and fused cricoid wings. As in the larynx, both the Syrinx and hyoid lack ossification and all three structures were most similar to Dromaius. We documented substantial variation across palaeognaths in the skeletal character states of the Syrinx, hyoid, and larynx, using both the literature and novel observations (e.g. of C. casuarius). Notably, new synapomorphies linking Dinornithiformes and Tinamidae are identified, consistent with the molecular evidence for this clade. These shared morphological character traits include the ossification of the cricoid and arytenoid cartilages, and an additional cranial character, the articulation between the maxillary process of the nasal and the maxilla. Syrinx, hyoid and larynx characters of palaeognaths display greater concordance with molecular trees than do other morphological traits. These structures might therefore be less prone to homoplasy related to flightlessness and gigantism, compared to typical morphological traits emphasised in previous phylogenetic studies.
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The phylogenetic significance of the morphology of the Syrinx, hyoid and larynx, of the southern cassowary, Casuarius casuarius (Aves, Palaeognathae)
BMC Evolutionary Biology, 2019Co-Authors: Phoebe Louise Mcinerney, Mike S. Y. Lee, Alice M. Clement, Trevor H. WorthyAbstract:Background Palaeognathae is a basal clade within Aves and include the large and flightless ratites and the smaller, volant tinamous. Although much research has been conducted on various aspects of palaeognath morphology, ecology, and evolutionary history, there are still areas which require investigation. This study aimed to fill gaps in our knowledge of the Southern Cassowary, Casuarius casuarius , for which information on the skeletal systems of the Syrinx, hyoid and larynx is lacking - despite these structures having been recognised as performing key functional roles associated with vocalisation, respiration and feeding. Previous research into the Syrinx and hyoid have also indicated these structures to be valuable for determining evolutionary relationships among neognath taxa, and thus suggest they would also be informative for palaeognath phylogenetic analyses, which still exhibits strong conflict between morphological and molecular trees. Results The morphology of the Syrinx, hyoid and larynx of C. casuarius is described from CT scans. The Syrinx is of the simple tracheo-bronchial Syrinx type, lacking specialised elements such as the pessulus; the hyoid is relatively short with longer ceratobranchials compared to epibranchials; and the larynx is comprised of entirely cartilaginous, standard avian anatomical elements including a concave, basin-like cricoid and fused cricoid wings. As in the larynx, both the Syrinx and hyoid lack ossification and all three structures were most similar to Dromaius. We documented substantial variation across palaeognaths in the skeletal character states of the Syrinx, hyoid, and larynx, using both the literature and novel observations (e.g. of C. casuarius ). Notably, new synapomorphies linking Dinornithiformes and Tinamidae are identified, consistent with the molecular evidence for this clade. These shared morphological character traits include the ossification of the cricoid and arytenoid cartilages, and an additional cranial character, the articulation between the maxillary process of the nasal and the maxilla. Conclusion Syrinx, hyoid and larynx characters of palaeognaths display greater concordance with molecular trees than do other morphological traits. These structures might therefore be less prone to homoplasy related to flightlessness and gigantism, compared to typical morphological traits emphasised in previous phylogenetic studies.
C D Bertram - One of the best experts on this subject based on the ideXlab platform.
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A Poroelastic Fluid/Structure- Interaction Model of Cerebrospinal Fluid Dynamics in the Cord With Syringomyelia and Adjacent Subarachnoid-Space Stenosis
2020Co-Authors: C D Bertram, Matthias HeilAbstract:An existing axisymmetric fluid/structure-interaction (FSI) model of the spinal cord, pia mater, subarachnoid space, and dura mater in the presence of syringomyelia and subarachnoid-space stenosis was modified to include porous solids. This allowed investigation of a hypothesis for Syrinx fluid ingress from cerebrospinal fluid (CSF). Gross model deformation was unchanged by the addition of porosity, but pressure oscillated more in the Syrinx and the subarachnoid space below the stenosis. The poroelastic model still exhibited elevated mean pressure in the subarachnoid space below the stenosis and in the Syrinx. With realistic cord permeability, there was slight oscillatory shunt flow bypassing the stenosis via the porous tissue over the Syrinx. Weak steady streaming flow occurred in a circuit involving craniocaudal flow through the stenosis and back via the Syrinx. Mean Syrinx volume was scarcely altered when the adjacent stenosis bisected the Syrinx, but increased slightly when the Syrinx was predominantly located caudal to the stenosis. The fluid content of the tissues over the Syrinx oscillated, absorbing most of the radial flow seeping from the subarachnoid space so that it did not reach the Syrinx. To a lesser extent, this cyclic swelling in a boundary layer of cord tissue just below the pia occurred all along the cord, representing a mechanism for exchange of interstitial fluid (ISF) and cerebrospinal fluid which could explain recent tracer findings without invoking perivascular conduits. The model demonstrates that Syrinx volume increase is possible when there is subarachnoid-space stenosis and the cord and pia are permeable
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a poroelastic fluid structure interaction model of cerebrospinal fluid dynamics in the cord with syringomyelia and adjacent subarachnoid space stenosis
Journal of Biomechanical Engineering-transactions of The Asme, 2017Co-Authors: C D Bertram, Matthias HeilAbstract:An existing axisymmetric fluid/structure-interaction (FSI) model of the spinal cord, pia mater, subarachnoid space, and dura mater in the presence of syringomyelia and subarachnoid-space stenosis was modified to include porous solids. This allowed investigation of a hypothesis for Syrinx fluid ingress from cerebrospinal fluid (CSF). Gross model deformation was unchanged by the addition of porosity, but pressure oscillated more in the Syrinx and the subarachnoid space below the stenosis. The poroelastic model still exhibited elevated mean pressure in the subarachnoid space below the stenosis and in the Syrinx. With realistic cord permeability, there was slight oscillatory shunt flow bypassing the stenosis via the porous tissue over the Syrinx. Weak steady streaming flow occurred in a circuit involving craniocaudal flow through the stenosis and back via the Syrinx. Mean Syrinx volume was scarcely altered when the adjacent stenosis bisected the Syrinx, but increased slightly when the Syrinx was predominantly located caudal to the stenosis. The fluid content of the tissues over the Syrinx oscillated, absorbing most of the radial flow seeping from the subarachnoid space so that it did not reach the Syrinx. To a lesser extent, this cyclic swelling in a boundary layer of cord tissue just below the pia occurred all along the cord, representing a mechanism for exchange of interstitial fluid (ISF) and cerebrospinal fluid which could explain recent tracer findings without invoking perivascular conduits. The model demonstrates that Syrinx volume increase is possible when there is subarachnoid-space stenosis and the cord and pia are permeable.
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evaluation by fluid structure interaction spinal cord simulation of the effects of subarachnoid space stenosis on an adjacent Syrinx
Journal of Biomechanical Engineering-transactions of The Asme, 2010Co-Authors: C D BertramAbstract:A finite-element numerical model was constructed of the spinal cord, pia mater, filum terminale, cerebrospinal fluid in the spinal subarachnoid space (SSS), and dura mater. The cord was hollowed out by a thoracic Syrinx of length 140 mm, and the SSS included a stenosis of length 30 mm opposite this Syrinx. The stenosis severity was varied from 0% to 90% by area. Pressure pulse excitation was applied to the model either at the cranial end of the SSS, simulating the effect of cranial arterial pulsation, or externally to the abdominal dura mater, simulating the effect of cough. A very short pulse was used to examine wave propagation; a pulse emulating cardiac systole was used to examine the effects of fluid displacement. Additionally, repetitive sinusoidal excitation was applied cranially. Bulk fluid flow past the stenosis gave rise to prominent longitudinal pressure dissociation ("suck") in the SSS adjacent to the Syrinx. However, this did not proportionally increase the longitudinal motion of fluid in the Syrinx. The inertia of the fluid in the SSS, together with the compliance of this space, gave a resonance capable of being excited constructively or destructively by cardiac or coughing impulses. The main effect of mild stenosis was to lower the frequency of this resonance; severe stenosis damped out to-and-fro motions after the end of the applied excitation. Syrinx fluid motion indicated the fluid momentum and thus the pressure developed when the fluid was stopped by the end of the Syrinx; however, the tearing stress in the local cord material depended also on the instantaneous local SSS pressure and was therefore not well predicted by Syrinx fluid motion. Stenosis was also shown to give rise to a one-way valve effect causing raised SSS pressure caudally and slight average cord displacement cranially. The investigation showed that previous qualitative predictions of the effects of suck neglected factors that reduced the extent of the resulting Syrinx fluid motion and of the cord tearing stress, which ultimately determines whether the Syrinx lengthens.
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a numerical investigation of waves propagating in the spinal cord and subarachnoid space in the presence of a Syrinx
Journal of Fluids and Structures, 2009Co-Authors: C D BertramAbstract:The term syringomyelia describes fluid-filled cavities in the spinal cord, which can interfere with normal nerve signal transmission. The finite-element code ADINA was used to construct an axisymmetric fluid/structure-interaction model of the tapered spinal cord and subarachnoid space (SAS), bounded by the dura mater. A Syrinx was simulated, of corresponding dimensions to one shown by magnetic resonance imaging data of a patient with syringomyelia. The model was used to investigate the clinical hypothesis that SAS pressure waves move fluid along a Syrinx and can thus lengthen it over time by tissue dissection. Simplified versions of the model were used to examine in detail the waves excited, and their reflection and refraction at sites of property discontinuity in the system. Comparison was made with wave predictions based on an analytical model, and excellent agreement was found. The results suggest that, under the circumstances modelled, pressure wave-induced motion of Syrinx fluid is unlikely to lengthen such cavities, unless the transverse tensile strength of cord tissue is even smaller than has been appreciated so far.
Lynne E Bilston - One of the best experts on this subject based on the ideXlab platform.
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chiari malformation may increase perivascular cerebrospinal fluid flow into the spinal cord a subject specific computational modelling study
Journal of Biomechanics, 2017Co-Authors: Robert A Lloyd, David F Fletcher, Elizabeth Clarke, Lynne E BilstonAbstract:Abstract Syringomyelia is associated with Chiari I malformation, although the mechanistic link is unclear. Studies have suggested that cerebrospinal fluid enters the spinal cord via the perivascular spaces, and that changes in the timing of the subarachnoid pressures may increase flow into the spinal cord. This study aims to determine how Chiari malformation and syringomyelia alter the subarachnoid space pressures and hence perivascular flow. Subject-specific models of healthy controls (N = 9), Chiari patients with (N = 7) and without (N = 8) syringomyelia, were developed from magnetic resonance imaging (MRI), to simulate the subarachnoid pressures. These pressures were input to an idealised model of the perivascular space to evaluate potential differences in perivascular flow. Peak pressures in Chiari patients without a Syrinx were higher than in controls (46% increase; p = .029) and arrived earlier in the cardiac cycle than both controls (2.58% earlier; p = .045) and Syrinx patients (2.85% earlier; p = .045). The perivascular model predicted Chiari patients without a Syrinx would have the greatest flow into the cord (p R Adj 2 = 0.85 ; p
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characteristics of csf velocity time profile in posttraumatic syringomyelia
American Journal of Neuroradiology, 2017Co-Authors: Shaokoon Cheng, Sarah J Hemley, Lynne E Bilston, Marcus A StoodleyAbstract:BACKGROUND AND PURPOSE: The development of syringomyelia has been associated with changes in CSF flow dynamics in the spinal subarachnoid space. However, differences in CSF flow velocity between patients with posttraumatic syringomyelia and healthy participants remains unclear. The aim of this work was to define differences in CSF flow above and below a Syrinx in participants with posttraumatic syringomyelia and compare the CSF flow with that in healthy controls. MATERIALS AND METHODS: Six participants with posttraumatic syringomyelia were recruited for this study. Phase-contrast MR imaging was used to measure CSF flow velocity at the base of the skull and above and below the Syrinx. Velocity magnitudes and temporal features of the CSF velocity profile were compared with those in healthy controls. RESULTS: CSF flow velocity in the spinal subarachnoid space of participants with syringomyelia was similar at different locations despite differences in Syrinx size and locations. Peak cranial and caudal velocities above and below the Syrinx were not significantly different (peak cranial velocity, P = .9; peak caudal velocity, P = 1.0), but the peak velocities were significantly lower (P < .001, P = .007) in the participants with syringomyelia compared with matched controls. Most notably, the duration of caudal flow was significantly shorter (P = .003) in the participants with syringomyelia. CONCLUSIONS: CSF flow within the posttraumatic syringomyelia group was relatively uniform along the spinal canal, but there are differences in the timing of CSF flow compared with that in matched healthy controls. This finding supports the hypothesis that Syrinx development may be associated with temporal changes in spinal CSF flow.
Richard C E Anderson - One of the best experts on this subject based on the ideXlab platform.
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radiological and clinical associations with scoliosis outcomes after posterior fossa decompression in patients with chiari malformation and Syrinx from the park reeves syringomyelia research consortium
Journal of Neurosurgery, 2020Co-Authors: Jennifer M Strahle, Rukayat Taiwo, Christine Averill, James C Torner, Chevis N Shannon, Christopher M Bonfield, Gerald F Tuite, Tammy Bethelanderson, Jordan I Gewirtz, Richard C E AndersonAbstract:OBJECTIVE In patients with Chiari malformation type I (CM-I) and a Syrinx who also have scoliosis, clinical and radiological predictors of curve regression after posterior fossa decompression are not well known. Prior reports indicate that age younger than 10 years and a curve magnitude 5°), and 16 (39%) displayed curve progression (> 5°) during the follow-up period. Younger age at the time of decompression was associated with improvement in curve magnitude; for those with curves of ≤ 35°, 17% of patients younger than 10 years of age had curve progression compared with 64% of those 10 years of age or older (p = 0.008). There was no difference by age for those with curves > 35°. Tonsil position, baseline Syrinx dimensions, and change in Syrinx size were not associated with the change in curve magnitude. There was no difference in progression after surgery in patients who were also treated with a brace compared to those who were not treated with a brace for scoliosis. CONCLUSIONS In this cohort of patients with CM-I, a Syrinx, and scoliosis, younger age at the time of decompression was associated with improvement in curve magnitude following surgery, especially in patients younger than 10 years of age with curves of ≤ 35°. Baseline tonsil position, Syrinx dimensions, frontooccipital horn ratio, and craniocervical junction morphology were not associated with changes in curve magnitude after surgery.
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radiological and clinical associations with scoliosis outcomes after posterior fossa decompression in patients with chiari malformation and Syrinx from the park reeves syringomyelia research consortium
Journal of Neurosurgery, 2020Co-Authors: Jennifer Strahle, Rukayat Taiwo, Christine Averill, James C Torner, Chevis N Shannon, Christopher M Bonfield, Gerald F Tuite, Tammy Bethelanderson, Jordan I Gewirtz, Richard C E AndersonAbstract:Objective In patients with Chiari malformation type I (CM-I) and a Syrinx who also have scoliosis, clinical and radiological predictors of curve regression after posterior fossa decompression are not well known. Prior reports indicate that age younger than 10 years and a curve magnitude Methods A large multicenter retrospective and prospective registry of pediatric patients with CM-I (tonsils ≥ 5 mm below the foramen magnum) and a Syrinx (≥ 3 mm in width) was reviewed for clinical and radiological characteristics of CM-I, Syrinx, and scoliosis (coronal curve ≥ 10°) in patients who underwent posterior fossa decompression and who also had follow-up imaging. Results Of 825 patients with CM-I and a Syrinx, 251 (30.4%) were noted to have scoliosis present at the time of diagnosis. Forty-one (16.3%) of these patients underwent posterior fossa decompression and had follow-up imaging to assess for scoliosis. Twenty-three patients (56%) were female, the mean age at time of CM-I decompression was 10.0 years, and the mean follow-up duration was 1.3 years. Nine patients (22%) had stable curves, 16 (39%) showed improvement (> 5°), and 16 (39%) displayed curve progression (> 5°) during the follow-up period. Younger age at the time of decompression was associated with improvement in curve magnitude; for those with curves of ≤ 35°, 17% of patients younger than 10 years of age had curve progression compared with 64% of those 10 years of age or older (p = 0.008). There was no difference by age for those with curves > 35°. Tonsil position, baseline Syrinx dimensions, and change in Syrinx size were not associated with the change in curve magnitude. There was no difference in progression after surgery in patients who were also treated with a brace compared to those who were not treated with a brace for scoliosis. Conclusions In this cohort of patients with CM-I, a Syrinx, and scoliosis, younger age at the time of decompression was associated with improvement in curve magnitude following surgery, especially in patients younger than 10 years of age with curves of ≤ 35°. Baseline tonsil position, Syrinx dimensions, frontooccipital horn ratio, and craniocervical junction morphology were not associated with changes in curve magnitude after surgery.
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factors associated with Syrinx size in pediatric patients treated for chiari malformation type i and syringomyelia a study from the park reeves syringomyelia research consortium
Journal of Neurosurgery, 2020Co-Authors: Christopher M Bonfield, Andrew T Hale, David P Adelson, Gregory W Albert, Philipp R Aldana, Tord D Alden, Richard C E Anderson, David F Bauer, Douglas L BrockmeyerAbstract:OBJECTIVE: Factors associated with Syrinx size in pediatric patients undergoing posterior fossa decompression (PFD) or PFD with duraplasty (PFDD) for Chiari malformation type I (CM-I) with syringomyelia (SM; CM-I+SM) are not well established. METHODS: Using the Park-Reeves Syringomyelia Research Consortium registry, the authors analyzed variables associated with Syrinx radiological outcomes in patients (< 20 years old at the time of surgery) with CM-I+SM undergoing PFD or PFDD. Syrinx resolution was defined as an anteroposterior (AP) diameter of ≤ 2 mm or ≤ 3 mm or a reduction in AP diameter of ≥ 50%. Syrinx regression or progression was defined using 1) change in Syrinx AP diameter (≥ 1 mm), or 2) change in Syrinx length (craniocaudal, ≥ 1 vertebral level). Syrinx stability was defined as a < 1-mm change in Syrinx AP diameter and no change in Syrinx length. RESULTS: The authors identified 380 patients with CM-I+SM who underwent PFD or PFDD. Cox proportional hazards modeling revealed younger age at surgery and PFDD as being independently associated with Syrinx resolution, defined as a ≤ 2-mm or ≤ 3-mm AP diameter or ≥ 50% reduction in AP diameter. Radiological Syrinx resolution was associated with improvement in headache (p < 0.005) and neck pain (p < 0.011) after PFD or PFDD. Next, PFDD (p = 0.005), scoliosis (p = 0.007), and Syrinx location across multiple spinal segments (p = 0.001) were associated with Syrinx diameter regression, whereas increased preoperative frontal-occipital horn ratio (FOHR; p = 0.007) and Syrinx location spanning multiple spinal segments (p = 0.04) were associated with Syrinx length regression. Scoliosis (HR 0.38 [95% CI 0.16-0.91], p = 0.03) and smaller Syrinx diameter (5.82 ± 3.38 vs 7.86 ± 3.05 mm; HR 0.60 [95% CI 0.34-1.03], p = 0.002) were associated with Syrinx diameter stability, whereas shorter preoperative Syrinx length (5.75 ± 4.01 vs 9.65 ± 4.31 levels; HR 0.21 [95% CI 0.12-0.38], p = 0.0001) and smaller pB-C2 distance (6.86 ± 1.27 vs 7.18 ± 1.38 mm; HR 1.44 [95% CI 1.02-2.05], p = 0.04) were associated with Syrinx length stability. Finally, younger age at surgery (8.19 ± 5.02 vs 10.29 ± 4.25 years; HR 1.89 [95% CI 1.31-3.04], p = 0.01) was associated with Syrinx diameter progression, whereas increased postoperative Syrinx diameter (6.73 ± 3.64 vs 3.97 ± 3.07 mm; HR 3.10 [95% CI 1.67-5.76], p = 0.003), was associated with Syrinx length progression. PFD versus PFDD was not associated with Syrinx progression or reoperation rate. CONCLUSIONS: These data suggest that PFDD and age are independently associated with radiological Syrinx improvement, although forthcoming results from the PFDD versus PFD randomized controlled trial (NCT02669836, clinicaltrials.gov) will best answer this question.
