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1.  Evaluation of pregnancy and delivery in 13 women who underwent resection of a sacrococcygeal teratoma during early childhood 
Sacrococcygeal teratoma resection often brings changes in pelvic anatomy and physiology with possible consequences for defecation, micturition and sexual function. It is unknown, whether these changes have any gynecological and obstetric sequelae. Until now four pregnancies after sacrococcygeal teratoma resection have been described and cesarean section has been suggested to be the method of choice for delivery. We evaluated the pregnancy course and mode of delivery in women previously treated for a sacrococcygeal teratoma.
The records of all patients who underwent sacrococcygeal teratoma resection after 1970 in one of the six pediatric surgical centers in the Netherlands were reviewed retrospectively. Women aged 18 years and older were eligible for participation. Patient characteristics, details about the performed operation and tumor histology were retrieved from the records. Consenting participants completed a questionnaire addressing fertility, pregnancy and delivery details.
Eighty-nine women were eligible for participation; 20 could not be traced. Informed consent was received from 41, of whom 38 returned the completed questionnaire (92.7%). Thirteen of these 38 women conceived, all but one spontaneously. In total 20 infants were born, 17 by vaginal delivery and 3 by cesarean section, in one necessitated by previous intra-abdominal surgery as a consequence of sacrococcygeal teratoma resection. Conversion to a cesarean section was never necessary. None of the 25 women without offspring reported involuntary childlessness.
There are no indications that resection of a sacrococcygeal teratoma in female patients is associated with reduced fertility: spontaneous pregnancy is possible and vaginal delivery is safe for mother and child, irrespective of the sacrococcygeal teratoma classification or tumor histology.
PMCID: PMC4271500  PMID: 25495179
Sacrococcygeal teratoma; Sequelae; Pregnancy; Vaginal delivery
2.  Revisiting corrective saccades: role of visual feedback 
Vision research  2013;89:54-64.
To clarify the role of visual feedback in the generation of corrective movements after inaccurate primary saccades, we used a visually-triggered saccade task in which we varied how long the target was visible. The target was on for only 100 ms (OFF100ms), on until the start of the primary saccade (OFFonset) or on for 2 s (ON). We found that the tolerance for the post-saccadic error was small (− 2%) with a visual signal (ON) but greater (−6%) without visual feedback (OFF100ms). Saccades with an error of −10%, however, were likely to be followed by corrective saccades regardless of whether or not visual feedback was present. Corrective saccades were generally generated earlier when visual error information was available; their latency was related to the size of the error. The LATER (Linear Approach to Threshold with Ergodic Rate) model analysis also showed a comparable small population of short latency corrective saccades irrespective of the target visibility. Finally, we found, in the absence of visual feedback, the accuracy of corrective saccades across subjects was related to the latency of the primary saccade. Our findings provide new insights into the mechanisms underlying the programming of corrective saccades: 1) the preparation of corrective saccades begins along with the preparation of the primary saccades, 2) the accuracy of corrective saccades depends on the reaction time of the primary saccades and 3) if visual feedback is available after the initiation of the primary saccade, the prepared correction can be updated.
PMCID: PMC3784029  PMID: 23891705
Primary saccade; Corrective saccade; Visual feedback; LATER model; Forward control
3.  Development and Validation of a Falls Grading Scale 
Journal of geriatric physical therapy (2001)  2013;36(2):10.1519/JPT.0b013e31825f6777.
Background and Purpose
The recording of fall events is usually subjective and imprecise, which limits clinical practice and falls-related research. We sought to develop and validate a scale to grade near-fall and fall events based on their severity represented by the use of healthcare resources, with the goal of standardizing fall reporting in the clinical and research settings.
Qualitative instrument development was based on a literature review and semi-structured interviews to assess face and content validity. We queried older individuals and healthcare professionals with expertise in the care of patients at risk of falling about clinically important differences to detect and how to optimize the scale's ease of use. To assess the scale's inter-rater reliability, we created 30 video-vignettes of falls and compared how healthcare professionals and volunteers rated each of the falls according to our grading scale.
We developed the illustrated 4-point Hopkins Falls Grading Scale (HFGS). The grades distinguish a near-fall (Grade 1) from a fall for which an individual did not receive medical attention (Grade 2), a fall associated with medical attention but not hospital admission (Grade 3), and a fall associated with hospital admission (Grade 4). Overall, the HFGS exhibited good face and content validity, and had an intraclass correlation coefficient of 0.998.
The 4-point HFGS demonstrates good face and content validity and high inter-rater reliability. We predict this tool will facilitate the standardization of falls reporting in both the clinical and research settings.
PMCID: PMC3867809  PMID: 22810170
Falls definition; falls classification; falls reporting
4.  Strong Static Magnetic Fields Elicit Swimming Behaviors Consistent with Direct Vestibular Stimulation in Adult Zebrafish 
PLoS ONE  2014;9(3):e92109.
Zebrafish (Danio rerio) offer advantages as model animals for studies of inner ear development, genetics and ototoxicity. However, traditional assessment of vestibular function in this species using the vestibulo-ocular reflex requires agar-immobilization of individual fish and specialized video, which are difficult and labor-intensive. We report that using a static magnetic field to directly stimulate the zebrafish labyrinth results in an efficient, quantitative behavioral assay in free-swimming fish. We recently observed that humans have sustained nystagmus in high strength magnetic fields, and we attributed this observation to magnetohydrodynamic forces acting on the labyrinths. Here, fish were individually introduced into the center of a vertical 11.7T magnetic field bore for 2-minute intervals, and their movements were tracked. To assess for heading preference relative to a magnetic field, fish were also placed in a horizontally oriented 4.7T magnet in infrared (IR) light. A sub-population was tested again in the magnet after gentamicin bath to ablate lateral line hair cell function. Free-swimming adult zebrafish exhibited markedly altered swimming behavior while in strong static magnetic fields, independent of vision or lateral line function. Two-thirds of fish showed increased swimming velocity or consistent looping/rolling behavior throughout exposure to a strong, vertically oriented magnetic field. Fish also demonstrated altered swimming behavior in a strong horizontally oriented field, demonstrating in most cases preferred swimming direction with respect to the field. These findings could be adapted for ‘high-throughput’ investigations of the effects of environmental manipulations as well as for changes that occur during development on vestibular function in zebrafish.
PMCID: PMC3960171  PMID: 24647586
5.  Magnetic Vestibular Stimulation in Subjects with Unilateral Labyrinthine Disorders 
We recently discovered that static magnetic fields from high-strength MRI machines induce nystagmus in all normal humans, and that a magneto-hydrodynamic Lorentz force, derived from ionic currents in the endolymph and pushing on the cupula, best explains this effect. Individuals with no labyrinthine function have no nystagmus. The influence of magnetic vestibular stimulation (MVS) in individuals with unilateral deficits in labyrinthine function is unknown and may provide insight into the mechanism of MVS. These individuals should experience MVS, but with a different pattern of nystagmus consistent with their unilateral deficit in labyrinthine function. We recorded eye movements in the static magnetic field of a 7 T MRI machine in nine individuals with unilateral labyrinthine hypofunction, as determined by head impulse testing and vestibular-evoked myogenic potentials (VEMP). Eye movements were recorded using infrared video-oculography. Static head positions were varied in pitch with the body supine, and slow-phase eye velocity (SPV) was assessed. All subjects exhibited predominantly horizontal nystagmus after entering the magnet head-first, lying supine. The SPV direction reversed when entering feet-first. Pitching chin-to-chest caused subjects to reach a null point for horizontal SPV. Right unilateral vestibular hypofunction (UVH) subjects developed slow-phase-up nystagmus and left UVH subjects, slow-phase-down nystagmus. Vertical and torsional components were consistent with superior semicircular canal excitation or inhibition, respectively, of the intact ear. These findings provide compelling support for the hypothesis that MVS is a result of a Lorentz force and suggest that the function of individual structures within the labyrinth can be assessed with MVS. As a novel method of comfortable and sustained labyrinthine stimulation, MVS can provide new insights into vestibular physiology and pathophysiology.
PMCID: PMC3952138  PMID: 24659983
vestibular; magnetic; semicircular canals; Lorentz; magneto-hydrodynamics
6.  Non-Invasive Serum Amyloid A (SAA) Measurement and Plasma Platelets for Accurate Prediction of Surgical Intervention in Severe Necrotizing Enterocolitis (NEC) 
PLoS ONE  2014;9(3):e90834.
To evaluate the value of biomarkers to detect severe NEC.
Summary Background Data
The time point of surgery in necrotizing enterocolitis (NEC) is critical. Therefore, there is a need for markers that detect severe NEC, because clinical signs of severe NEC often develop late. This study evaluated the value of biomarkers reflecting intestinal cell damage and inflammation to detect severe NEC.
29 neonates with NEC were included. Two definitions of moderate versus severe NEC were analyzed: medical NEC (n = 12) versus surgical or fatal NEC (n = 17); and Bell stage II NEC (n = 13) versus stage III NEC (n = 16). Urinary intestinal fatty acid binding protein (I-FABP), serum amyloid A (SAA), C3a and C5a, and fecal calprotectin were measured. C-reactive protein (CRP), white blood cell count (WBC) and platelet count data were measured in blood.
In both definitions of moderate versus severe NEC, urinary SAA levels were significantly higher in severe NEC. A cut-off value of 34.4 ng/ml was found in surgical NEC versus medical NEC (sensitivity, 83%; specificity, 83%; LR+, 4.88 (95% CI, 1.37–17.0); LR−, 0.20 (95% CI, 0.07–0.60)) at diagnosis of NEC and at one day prior to surgery in neonates who were operated later on. Combination of urinary SAA and platelet count increased the accuracy, with a sensitivity, 94%; specificity, 83%; LR+, 5.53 (95% CI, 1.57–20.0); and LR−, 0.07 (95% CI, 0.01–0.48).
Urinary SAA is an accurate marker in differentiating severe NEC from moderate NEC; particularly if combined with serum platelet count.
PMCID: PMC3946234  PMID: 24603723
7.  Keeping Your Head On Target 
The Journal of Neuroscience  2013;33(27):11281-11295.
The mechanisms by which the human brain controls eye movements are reasonably well understood, but those for the head less so. Here, we show that the mechanisms for keeping the head aimed at a stationary target follow strategies similar to those for holding the eyes steady on stationary targets. Specifically, we applied the neural integrator hypothesis that originally was developed for holding the eyes still in eccentric gaze positions to describe how the head is held still when turned toward an eccentric target. We found that normal humans make head movements consistent with the neural integrator hypothesis, except that additional sensory feedback is needed, from proprioceptors in the neck, to keep the head on target. We also show that the complicated patterns of head movements in patients with cervical dystonia can be predicted by deficits in a neural integrator for head motor control. These results support ideas originally developed from animal studies that suggest fundamental similarities between oculomotor and cephalomotor control, as well as a conceptual framework for cervical dystonia that departs considerably from current clinical views.
PMCID: PMC3718362  PMID: 23825431
8.  MRI shows a region-specific pattern of atrophy in spinocerebellar ataxia type 2 
Cerebellum (London, England)  2012;11(1):272-279.
In this study, we used manual delineation of high-resolution magnetic resonance imaging (MRI) to determine the spatial and temporal characteristics of the cerebellar atrophy in spinocerebellar ataxia type 2 (SCA2). Ten subjects with SCA2 were compared to ten controls. The volume of the pons, the total cerebellum, and the individual cerebellar lobules were calculated via manual delineation of structural MRI. SCA2 showed substantial global atrophy of the cerebellum. Furthermore, the degeneration was lobule-specific, selectively affecting the anterior lobe, VI, Crus I, Crus II, VIII, uvula, corpus medullare, and pons, while sparing VIIB, tonsil/paraflocculus, flocculus, declive, tuber/folium, pyramis, and nodulus. The temporal characteristics differed in each cerebellar subregion: 1) Duration of disease: Crus I, VIIB, VIII, uvula, corpus medullare, pons, and the total cerebellar volume correlated with the duration of disease; 2) Age: VI, Crus II, and flocculus correlated with age in control subjects; 3) Clinical scores: VI, Crus I, VIIB, VIII, corpus medullare, pons, and the total cerebellar volume correlated with clinical scores in SCA2. No correlations were found with the age of onset. Our extrapolated volumes at the onset of symptoms suggest that neurodegeneration may be present even during the presymptomatic stages of disease. The spatial and temporal characteristics of the cerebellar degeneration in SCA2 are region-specific. Furthermore, our findings suggest the presence of presymptomatic atrophy and a possible developmental component to the mechanisms of pathogenesis underlying SCA2. Our findings further suggest that volumetric analysis may aid in the development of a non-invasive, quantitative biomarker.
PMCID: PMC3785794  PMID: 21850525
ataxia; spinocerebellar ataxia type 2 (SCA2); magnetic resonance imaging (MRI); biomarker
9.  The Under-compensatory Roll aVOR Does Not Affect Dynamic Visual Acuity 
Rotations of the head evoke compensatory reflexive eye rotations in the orbit to stabilize images onto the fovea. In normal humans, the angular vestibulo-ocular reflex (aVOR) gain (eye/head velocity) changes depending on the head rotation plane. For pitch and yaw head rotations, the gain is near unity, but during roll head rotations, the aVOR gain is ∼0.7. The purpose of this study was to determine whether this physiological discrepancy affects dynamic visual acuity (DVA)—a functional measure of the aVOR that requires subjects to identify letters of varying acuities during head rotation. We used the scleral search coil technique to measure eye and head velocity during passive DVA testing in yaw, roll, and pitch head impulses in healthy controls and patients with unilateral vestibular hypofunction (UVH). For control subjects, the mean aVOR gain during roll impulses was significantly lower than the mean aVOR gain during yaw and pitch impulses; however, there was no difference in DVA between yaw, roll, or pitch. For subjects with UVH, only aVOR gain during head rotations toward the affected side (yaw) were asymmetric (ipsilesional, 0.32 ± 0.17, vs. contralesional, 0.95 ± 0.05), with no asymmetry during roll or pitch. Similarly, there was a large asymmetry for DVA only during yaw head rotations, with no asymmetry in roll or pitch. Interestingly, DVA during roll toward the affected ear was better than DVA during yaw toward the affected ear—even though the ipsilesional roll aVOR gain was 60 % lower. During roll, the axis of eye rotation remains nearly perpendicular to the fovea, resulting in minimal displacement between the fovea and fixation target image projected onto the back of the eye. For subjects with UVH, the DVA score during passive horizontal impulses is a better indicator of poor gaze stability than during passive roll or pitch.
PMCID: PMC3387313  PMID: 22526736
vestibulo-ocular reflex; head impulses; dynamic visual acuity; gain
10.  Disorders of Upper Limb Movements in Ataxia-Telangiectasia 
PLoS ONE  2013;8(6):e67042.
Ataxia-telangiectasia is known for cerebellar degeneration, but clinical descriptions of abnormal tone, posture, and movements suggest involvement of the network between cerebellum and basal ganglia. We quantitatively assessed the nature of upper-limb movement disorders in ataxia-telangiectasia. We used a three-axis accelerometer to assess the natural history and severity of abnormal upper-limb movements in 80 ataxia-telangiectasia and 19 healthy subjects. Recordings were made during goal-directed movements of upper limb (kinetic task), while arms were outstretched (postural task), and at rest. Almost all ataxia-telangiectasia subjects (79/80) had abnormal involuntary movements, such as rhythmic oscillations (tremor), slow drifts (dystonia or athetosis), and isolated rapid movements (dystonic jerks or myoclonus). All patients with involuntary movements had both kinetic and postural tremor, while 48 (61%) also had resting tremor. The tremor was present in transient episodes lasting several seconds during two-minute recording sessions of all three conditions. Percent time during which episodic tremor was present was greater for postural and kinetic tasks compared to rest. Resting tremor had higher frequency but smaller amplitude than postural and kinetic tremor. Rapid non-rhythmic movements were minimal during rest, but were triggered during sustained arm postures and goal directed arm movements suggesting they are best considered a form of dystonic jerks or action myoclonus. Advancing age did not correlate with the severity of involuntary limb movements. Abnormal upper-limb movements in ataxia-telangiectasia feature classic cerebellar impairment, but also suggest involvement of the network between the cerebellum and basal ganglia.
PMCID: PMC3694953  PMID: 23826191
11.  Superficially Located White Matter Structures Commonly Seen in the Human and the Macaque Brain with Diffusion Tensor Imaging 
Brain connectivity  2011;1(1):37-47.
The white matter of the brain consists of fiber tracts that connect different regions of the brain. Among these tracts, the intrahemispheric cortico-cortical connections are called association fibers. The U-fibers are short association fibers that connect adjacent gyri. These fibers were thought to work as part of the cortico-cortical networks to execute associative brain functions. However, their anatomy and functions have not been documented in detail for the human brain. In past studies, U-fibers have been characterized in the human brain with diffusion tensor imaging (DTI). However, the validity of such findings remains unclear. In this study, DTI of the macaque brain was performed, and the anatomy of U-fibers was compared with that of the human brain reported in a previous study. The macaque brain was chosen because it is the most commonly used animal model for exploring cognitive functions and the U-fibers of the macaque brain have been already identified by axonal tracing studies, which makes it an ideal system for confirming the DTI findings. Ten U-fibers found in the macaque brain were also identified in the human brain, with a similar organization and topology. The delineation of these species-conserved white matter structures may provide new options for understanding brain anatomy and function.
PMCID: PMC3569096  PMID: 22432953
association fiber; blade; diffusion tensor imaging; macaque, U-fiber; white matter
12.  Role of Cerebellum in Motion Perception and Vestibulo-ocular Reflex—Similarities and Disparities 
Cerebellum (London, England)  2013;12(1):97-107.
Vestibular velocity storage enhances the efficacy of the angular vestibulo-ocular reflex (VOR) during relatively low-frequency head rotations. This function is modulated by GABA-mediated inhibitory cerebellar projections. Velocity storage also exists in perceptual pathway and has similar functional principles as VOR. However, it is not known whether the neural substrate for perception and VOR overlap. We propose two possibilities. First, there is the same velocity storage for both VOR and perception; second, there are nonoverlapping neural networks: one might be involved in perception and the other for the VOR. We investigated these possibilities by measuring VOR and perceptual responses in healthy human subjects during whole-body, constant-velocity rotation steps about all three dimensions (yaw, pitch, and roll) before and after 10 mg of 4-aminopyridine (4-AP). 4-AP, a selective blocker of inward rectifier potassium conductance, can lead to increased synchronization and precision of Purkinje neuron discharge and possibly enhance the GABAergic action. Hence 4-AP could reduce the decay time constant of the perceived angular velocity and VOR. We found that 4-AP reduced the decay time constant, but the amount of reduction in the two processes, perception and VOR, was not the same, suggesting the possibility of nonoverlapping or partially overlapping neural substrates for VOR and perception. We also noted that, unlike the VOR, the perceived angular velocity gradually built up and plateau prior to decay. Hence, the perception pathway may have additional mechanism that changes the dynamics of perceived angular velocity beyond the velocity storage. 4-AP had no effects on the duration of build-up of perceived angular velocity, suggesting that the higher order processing of perception, beyond the velocity storage, might not occur under the influence of mechanism that could be influenced by 4-AP.
PMCID: PMC3510326  PMID: 22777507
Vestibular; Eye movements; GABA; Brainstem; Velocity storage; Cerebellum
13.  MRI Magnetic Field Stimulates Rotational Sensors of the Brain 
Current Biology  2011;21(19):1635-1640.
Vertigo in and around MRI machines has been noted for years [1, 2]. Several mechanisms have been suggested to explain these sensations [3, 4], yet without direct, objective measures, the cause is unknown. We found that all healthy human subjects lying in the static magnetic field of an MRI machine develop a robust nystagmus. Patients lacking labyrinthine function do not. Here we use the pattern of eye movements as a measure of vestibular stimulation to show that the stimulation is static (continuous, proportional to static magnetic field strength, requiring neither head movement nor dynamic change in magnetic field strength) and directional (sensitive to magnetic field polarity and head orientation). Our calculations and geometric model suggest that magnetic vestibular stimulation derives from a Lorentz force due to interaction between the magnetic field and naturally-occurring ionic currents in the labyrinthine endolymph fluid. This force pushes on the semicircular canal cupula, leading to nystagmus. We emphasize that the unique, dual role of endolymph in the delivery of both ionic current and fluid pressure, coupled with the cupula’s function as a pressure sensor, makes magnetic field induced nystagmus and vertigo possible. Such effects could confound fMRI studies of brain behavior, including resting-state brain activity.
PMCID: PMC3379966  PMID: 21945276
14.  OrbitView: Eye movement visualization software 
Journal of neuroscience methods  2011;200(2):181-184.
Measurement of eye movements often helps to diagnose ocular motor disorders in the clinic, and is also used as a research tool in ocular motor, vision and vestibular research. Eye movements, however, are usually recorded without simultaneous video recordings, making offline interpretation difficult. We developed a tool that converts the measured eye movement data into a three-dimensional (3D) movie of eye movements. Having useful functions such as slow-play, pause and exaggeration of the movements, this new software provides a research and teaching tool to aid interpretation of the recorded eye movements.
PMCID: PMC3156268  PMID: 21689683
Data visualization; Emulation of eye movements; Clinical tool; Research tool; Teaching tool
15.  The effects of ion channel blockers validate the conductance-based model of saccadic oscillations 
Conductance-based models of reciprocally inhibiting burst neurons suggest that intrinsic membrane properties and postinhibitory rebound (PIR) determine the amplitude and frequency of saccadic oscillations. Reduction of the low-threshold calcium currents (IT) in the model decreased the amplitude but increased the frequency of the simulated oscillations. Combined reduction of hyperpolarization-activated cation current (Ih) and IT in the model abolished the simulated oscillations. We measured the effects of a selective blocker of IT (ethosuximide) in healthy subjects on the amplitude and frequency of saccadic oscillations evoked by eye closure and of a nonselective blocker of Ih and IT (propronolol) in a patient with microsaccadic oscillation and limb tremor syndrome (mSOLT). Ethosuximide significantly reduced the amplitude but increased the frequency of the saccadic oscillations during eye closure in healthy subjects. Propranolol abolished saccadic oscillations in the mSOLT patient. These results support the hypothetical role of postinhibitory rebound, Ih, and IT, in generation of saccadic oscillations and determining their kinematic properties.
PMCID: PMC3431800  PMID: 21950976
burst neurons; hyperpolarization-activated cation current; low-threshold calcium current; reciprocal innervations
16.  Opsoclonus-myoclonus syndrome and exaggerated startle response associated with small-cell lung cancer 
PMCID: PMC3139745  PMID: 21452255
Opsoclonus; myoclonus; paraneoplastic; startle; oscillopsia
17.  Learning Curve of Thoracoscopic Repair of Esophageal Atresia 
World Journal of Surgery  2012;36(9):2093-2097.
Thoracoscopic repair of esophageal atresia is considered to be one of the more advanced pediatric surgical procedures, and it undoubtedly has a learning curve. This is a single-center study that was designed to determine the learning curve of thoracoscopic repair of esophageal atresia.
The study involved comparison of the first and second five-year outcomes of thoracoscopic esophageal atresia repair.
The demographics of the two groups were comparable. There was a remarkable reduction of postoperative leakage or stenosis, and recurrence of fistulae, in spite of the fact that nowadays the procedure is mainly performed by young staff members and fellows.
There is a considerable learning curve for thoracoscopic repair of esophageal atresia. Centers with the ambition to start up a program for thoracoscopic repair of esophageal atresia should do so with the guidance of experienced centers.
PMCID: PMC3414695  PMID: 22584690
18.  TMS perturbs saccade trajectories and unmasks an internal feedback controller for saccades 
When we applied a single pulse of transcranial magnetic stimulation (TMS) to any part of the human head during a saccadic eye movement, the ongoing eye velocity was reduced starting as early as 45ms after the TMS, and lasted around 32ms. The perturbation to the saccade trajectory was not due to a mechanical effect of the lid on the eye (e.g., from blinks). When the saccade involved coordinated movements of both the eyes and the lids, e.g., in vertical saccades, TMS produced a synchronized inhibition of the motor commands to both eye and lid muscles. The TMS induced perturbation of the eye trajectory did not show habituation with repetition, and was present in both pro- and anti-saccades. Despite the perturbation, the eye trajectory was corrected within the same saccade with compensatory motor commands that guided the eyes to the target. This within-saccade correction did not rely on visual input, suggesting that the brain monitored the oculomotor commands as the saccade unfolded, maintained a real time estimate of the position of the eyes, and corrected for the perturbation. TMS disrupted saccades regardless of the location of the coil on the head, suggesting that the coil discharge engages a non-habituating startle-like reflex system. This system affects ongoing motor commands upstream of the oculomotor neurons, possibly at the level of the superior colliculus or omnipause neurons. Therefore, a TMS pulse centrally perturbs saccadic motor commands, which are monitored possibly via efference copy, and are corrected via internal feedback.
PMCID: PMC3167087  PMID: 21832184
saccade accuracy; pause; TMS; startle; omnipause neuron; forward model
19.  Superficially Located White Matter Structures Commonly Seen in the Human and the Macaque Brain with Diffusion Tensor Imaging 
Brain Connectivity  2011;1(1):37-47.
The white matter of the brain consists of fiber tracts that connect different regions of the brain. Among these tracts, the intrahemispheric cortico-cortical connections are called association fibers. The U-fibers are short association fibers that connect adjacent gyri. These fibers were thought to work as part of the cortico-cortical networks to execute associative brain functions. However, their anatomy and functions have not been documented in detail for the human brain. In past studies, U-fibers have been characterized in the human brain with diffusion tensor imaging (DTI). However, the validity of such findings remains unclear. In this study, DTI of the macaque brain was performed, and the anatomy of U-fibers was compared with that of the human brain reported in a previous study. The macaque brain was chosen because it is the most commonly used animal model for exploring cognitive functions and the U-fibers of the macaque brain have been already identified by axonal tracing studies, which makes it an ideal system for confirming the DTI findings. Ten U-fibers found in the macaque brain were also identified in the human brain, with a similar organization and topology. The delineation of these species-conserved white matter structures may provide new options for understanding brain anatomy and function.
PMCID: PMC3569096  PMID: 22432953
association fiber; blade; diffusion tensor imaging; macaque, U-fiber; white matter
20.  The influence of the CO2 pneumoperitoneum on a rat model of intestinal anastomosis healing 
Surgical Endoscopy  2011;26(6):1642-1647.
The CO2 pneumoperitoneum, which is used for laparoscopic surgery, causes local and systemic effects in patients. Concern arises about what the pressurized anoxic environment of the CO2 pneumoperitoneum has on intestinal healing. Earlier experimental work showed a negative correlation between intestinal healing and the applied intra-abdominal pressure. To further elucidate this, we developed a rat model, in which enterotomy healing can be compared after open or laparoscopic surgery. Possible mechanisms of injury, such as impaired neoangiogenesis or injury through hypoxia-induced pathways were studied.
A new experimental mechanically ventilated rat model was developed. An enterotomy was made and closed via laparotomy (group I) or laparoscopy under CO2 pressures of 5 mmHg (group II) or 10 mmHg (group III). Intestinal healing was tested in vivo after 1 week by bursting-pressure analysis. The effect of the operative procedure on neoangiogenesis was tested by counting factor VIII positive vessels in biopsies of the perianastomotic granulation tissue after 1 week. Intestinal anoxia was tested by quantifying HIF-1α protein levels in intestinal biopsies, taken before the enterotomy closure.
The bursting pressures were significantly lower after laparoscopic surgery at 10 mmHg CO2 pneumoperitoneum (group III) compared with rats that had undergone open surgery (group I) or laparoscopic surgery at 5 mmHg CO2 pneumoperitoneum (group II). There was no significant quantitative difference between the three groups in the neoangiogenesis nor was there a difference in the amount of HIF-1α measured in the intestinal biopsies.
We developed a surgical model that is well fitted to study the effects of pneumoperitoneum on intestinal healing. With this model, we found further evidence of CO2 pressure-dependant hampered intestinal healing. These differences could not be explained by difference in neoangiogenesis nor local upregulation of hypoxic factors.
PMCID: PMC3351619  PMID: 22179471
Anastomosis healing; Rat model; CO2; Pneumoperitoneum; Neoangiogenesis; HIF-1 alpha
21.  Context-specific saccadic adaptation in monkeys 
Vision research  2010;50(23):2403-2410.
When environmental or sensory conditions change suddenly, the brain must be capable of learning different behavioral modes to produce accurate movements under multiple circumstances. A form of this dual-state adaptation known as “context-specific adaptation” has been widely investigated using the saccade gain adaptation paradigm in humans. In this study, we asked whether or not context-specific adaptation of saccade gain exists in monkeys and if so to explore its properties. Here, vertical eye position was used as a context cue for adaptation of horizontal saccade gain. We asked for a gain increase in one context and gain decrease in another context, and then determined if a change in the context would invoke switching between the adapted states. After training, our monkeys developed context-specific adaptation: in most cases gain-decrease adaptation could be induced, but there was little or no gain-increase adaptation. This context-specific adaptation developed gradually and switching of gains was evident on the first saccades with each change in context. Along with these results, the retention of an adaptation aftereffect overnight indicates that contextual-specific adaptation in monkeys is not a strategy, but involves a true adaptive process of reorganization in the brain. We suggest that context-specific adaptation in monkeys could be an important tool to provide insights into the mechanisms of saccade adaptation that occurs during the more natural circumstances of daily life.
PMCID: PMC2975835  PMID: 20854833
Saccade; Adaptation; Context; Motor learning; Monkey
22.  Large Genomic Deletions in CACNA1A Cause Episodic Ataxia Type 2 
Episodic ataxia (EA) syndromes are heritable diseases characterized by dramatic episodes of imbalance and incoordination. EA type 2 (EA2), the most common and the best characterized subtype, is caused by mostly nonsense, splice site, small indel, and sometimes missense mutations in CACNA1A. Direct sequencing of CACNA1A fails to identify mutations in some patients with EA2-like features, possibly due to incomplete interrogation of CACNA1A or defects in other EA genes not yet defined. Previous reports described genomic deletions between 4 and 40 kb in EA2. In 47 subjects with EA (26 with EA2-like features) who tested negative for mutations in the known EA genes, we used multiplex ligation-dependent probe amplification to analyze CACNA1A for exonic copy number variations. Breakpoints were further defined by long-range PCR. We identified distinct multi-exonic deletions in three probands with classic EA2-like features: episodes of prolonged vertigo and ataxia triggered by stress and fatigue, interictal nystagmus, with onset during infancy or early childhood. The breakpoints in all three probands are located in Alu sequences, indicating errors in homologous recombination of Alu sequences as the underlying mechanism. The smallest deletion spanned exons 39 and 40, while the largest deletion spanned 200 kb, missing all but the first three exons. One deletion involving exons 39 through 47 arose spontaneously. The search for mutations in CACNA1A appears most fruitful in EA patients with interictal nystagmus and onset early in life. The finding of large heterozygous deletions suggests haploinsufficiency as a possible pathomechanism of EA2.
PMCID: PMC3169784  PMID: 21927611
episodic ataxia; EA2; genomic rearrangement; CACNA1A; mutation
23.  Cerebellum and Ocular Motor Control 
An intact cerebellum is a prerequisite for optimal ocular motor performance. The cerebellum fine-tunes each of the subtypes of eye movements so they work together to bring and maintain images of objects of interest on the fovea. Here we review the major aspects of the contribution of the cerebellum to ocular motor control. The approach will be based on structural–functional correlation, combining the effects of lesions and the results from physiologic studies, with the emphasis on the cerebellar regions known to be most closely related to ocular motor function: (1) the flocculus/paraflocculus for high-frequency (brief) vestibular responses, sustained pursuit eye movements, and gaze holding, (2) the nodulus/ventral uvula for low-frequency (sustained) vestibular responses, and (3) the dorsal oculomotor vermis and its target in the posterior portion of the fastigial nucleus (the fastigial oculomotor region) for saccades and pursuit initiation.
PMCID: PMC3164106  PMID: 21909334
saccade; vestibular; pursuit; flocculus; paraflocculus; nodulus; vermis; fastigial
24.  The Effects and Efficacy of Antireflux Surgery in Children with Gastroesophageal Reflux Disease: A Systematic Review 
Journal of Gastrointestinal Surgery  2011;15(10):1872-1878.
Antireflux surgery (ARS) for gastroesophageal reflux disease (GERD) is one of the most frequently performed major operations in children. Many studies have described the results of ARS in children, however, with a wide difference in outcome. This study aims to systematically review the efficacy of pediatric ARS and its effects on gastroesophageal function, as measured by gastroesophageal function tests. This is the first systematic review comprising only prospective, longitudinal studies, minimizing the risk of bias.
Three electronic databases (Medline, Embase, and the Cochrane Library) were searched for prospective studies reporting on ARS in children with GERD.
In total, 17 eligible studies were identified, reporting on a total of 1,280 children. The median success rate after ARS was 86% (57–100%). The success rate in neurologically impaired children was worse in one study, but similar in another study compared to normally developed children. Different surgical techniques (total versus partial fundoplication, or laparoscopic versus open approach) showed similar reflux recurrence rates. However, less postoperative dysphagia was observed after partial fundoplication and laparoscopic ARS was associated with less pain medication and a shorter hospital stay. Complications of ARS varied from minimal postoperative complications to severe dysphagia and gas bloating. The reflux index (RI), obtained by 24-h pH monitoring (n = 8) decreased after ARS. Manometry, as done in three studies, showed no increase in lower esophageal sphincter pressure after ARS. Gastric emptying (n = 3) was reported either unchanged or accelerated after ARS. No studies reported on barium swallow x-ray, endoscopy, or multichannel intraluminal impedance monitoring before and after ARS.
ARS in children shows a good overall success rate (median 86%) in terms of complete relief of symptoms. Efficacy of ARS in neurologically impaired children may be similar to normally developed children. The outcome of ARS does not seem to be influenced by different surgical techniques, although postoperative dysphagia may occur less after partial fundoplication. However, these conclusions are bound by the lack of high-quality prospective studies on pediatric ARS. Similar studies on the effects of pediatric ARS on gastroesophageal function are also very limited. We recommend consistent use of standardized assessment tests to clarify the effects of ARS on gastroesophageal function and to identify possible risk factors for failure of ARS in children.
PMCID: PMC3179590  PMID: 21800225
Gastroesophageal reflux; Antireflux surgery; Fundoplication; Children
25.  Laparoscopic Repair of Duodenal Atresia: Revisited 
World Journal of Surgery  2011;35(8):1781-1784.
Since the initial reports of laparoscopic repair of duodenal atresia in neonates, further reports have been scant. Could this be because of unacceptable rates of complications, like anastomotic leakage, as mentioned in later reports? In the present study the laparoscopic repair of duodenal atresia in neonates is revisited.
Group 1 consisted of 22 patients with duodenal obstruction between 2000–2005 until the laparoscopic approach was abandoned. Of these 22 patients, 10 had Down syndrome and 8 had concomitant malformations. In this group 18 patients were operated laparoscopically. Four patients underwent an open procedure. Group 2 consisted of six patients that underwent operation between 2008 and February 2010.
In group 1 there were four conversions. In 14 patients the procedure could be completed laparoscopically. In five patients postoperative leakage occurred. The complication rate was found to be unacceptably high, and the laparoscopic approach was abandoned. After gaining additional experience in intracorporeal suturing and adjusting the technique, the procedure was started up again in 2008. Since then six consecutive neonates have undergone laparoscopic repair of duodenal atresia without complications.
Laparoscopic repair of duodenal atresia is one of the most demanding pediatric laparoscopic surgical procedures. After initial promising results at the beginning of the twenty-first century a relative “radio silence“ followed, apparently caused by unsatisfactory results. Only considerable adjustments in technique and extensive improvement in experience has led to acceptable outcomes more recently. Laparoscopic repair of duodenal atresia should therefore be restricted to pediatric centers with extensive experience in laparoscopic surgery and intracorporeal suturing.
PMCID: PMC3127017  PMID: 21604051

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