¿Afecta el dolor al volumen local del cerebro? Aportaciones desde un modelo clínico de dolor agudo

Background/Objective:To study pain-brain morphometry associations as a function of post-surgery stages (anesthesia, pain and analgesia) in an acute pain model. Method:Impacted mandible third molar were extracted. Before surgery, an anatomical T1 scan was obtained. Regional brain volumen and subcortical nuclei shapes were obtained. Statistical analyses were done using multiple regression, being pain scores the predictors and voxel volumes, subcortical nuclei volumes and subcortical nuclei shapes, the outcomes. Results:Pain was significantly larger at pain than at anesthesia and analgesia stages, and was higher during anesthesia than during analgesia. Pain intensity was related to grey matter in several cortical (Insula, Mid Frontal and Temporal Gyruses, Precuneus, Anterior Cingulate), and subcortical nuclei (Hippocampus, Thalamus, Putamen, Amygdala), depending of the post-surgical stage. A larger number of brain areas showed significance at pain that at anesthesia and analgesia stages. Conclusions:The relationships of regional brain volumes and subcortical nuclei shapes with pain scores seemed to be unsteady, as they changed with the patient’s actual pain stage.Antecedentes/Objetivo: Se trata de determinar la asociación entre dolor percibido y morfometría cerebral en tres etapas postquirúrgicas (anestesia, dolor y analgesia), en un modelo de dolor agudo. Método: Se obtuvo una imagen cerebral estructural de alta resolución y posteriormente se extrajeron los terceros molares mandibulares impactados. Se realizó un análisis morfométrico para determinar volumen cerebral y forma de núcleos subcorticales. Se realizaron análisis de regresión múltiple, siendo la intensidad del dolor el predictor, y el volumen y la forma de los núcleos subcorticales, medidos pre-cirugía, las variables dependientes.Resultados:El dolor experimentado fue mayor en la etapa de dolor que en las de anestesia y analgesia, y mayor en anestesia que en analgesia. El dolor se asoció con el volumen de materiagris en áreas corticales (insula, giros frontal medial y temporal, precuneus y cingulado anterior) y subcorticales (hipocampo, tálamo, putamen y amígdala). El número de áreas asociadasal dolor experimentado fue mayor en la etapa de dolor que en las de anestesia y analgesia. Conclusiones: La relación entre volumen cerebral regional y forma de núcleos subcorticales con la intensidad del dolor no es fijo, sino que varía en función de la etapa post-quirúrgica (magnitud del dolor).This investigation was partially supported by Research Groups #CTS-138, #CTS-176 and #CTS-1028. (Junta de Andalucía, Spain)

Face Motor Cortex Neuroplasticity Associated with Alterations in the Oral Environment of the Adult Rat

Neuroplastic changes in motor representations within the primary motor cortex (M1) have been described after peripheral manipulations and implicated in motor learning and adaptation processes. It is unclear whether dental manipulations, which may result in altered oral sensorimotor functions, are associated with analogous changes within face-M1. This project applied intracortical microstimulation (ICMS) and recordings of evoked muscle electromyographic (EMG) activity to test if changes occur in the ICMS-defined motor representations of tongue-protrusion (genioglossus, GG) and jaw-opening (anterior-digastric, AD) muscles within face-M1 and adjacent face primary somatosensory cortex (face-S1) following trimming or extraction of the rat’s right mandibular incisor, or a change in diet consistency. ICMS mapping was carried out in anaesthetised adult male rats. Consistent with previous findings, AD and GG had extensive motor representations showing considerable overlap in naïve and sham control rats. AD and GG motor representations were also found within face-S1. Left and right AD (LAD, RAD) had significantly larger representations with shorter onset latency of ICMS-evoked EMG responses within contralateral face-M1. A change in diet consistency for 2-3 weeks was not associated with significant changes in AD and GG motor representations within face-M1. Compared to control rats, iii incisor trimming out of occlusion for a period of 1 week resulted, 1 day later, in a significantly longer GG onset latency in ipsilateral than in contralateral face-M1; 1 week later, despite a regain of normal occlusion, GG and GG/AD overlapping representations were significantly larger and the centre of gravity (at AP 4.0) was significantly deeper in contralateral than in ipsilateral face-M1. Incisor extraction was associated, 1 week later, with significantly larger RAD and RAD/GG overlapping representations and a lateral shift of LAD and RAD centre of gravity. Extraction also induced significant changes in AD and GG motor representations within the contralateral face-S1. These novel findings indicate that face-M1 can undergo neuroplastic changes in association with intraoral manipulations and also suggest similar neuroplastic capabilities for face-S1 motor outputs. These findings contribute to our understanding of the role of face-M1 and face-S1 in sensorimotor adaptations to an altered oral state and provide the basis for several future studies.Ph

Impaired bone healing at tooth extraction sites in CD24-deficient mice: A pilot study

<div><p>Aim</p><p>To use a micro-computed tomography (micro-CT) to quantify bone healing at maxillary first molar extraction sites, and test the hypothesis that bone healing is impaired in <i>CD24</i>-knockout mice as compared with wild-type C57BL/6J mice.</p><p>Materials and methods</p><p>Under ketamine-xylazine general anaesthesia, mice had either extraction of the right maxillary first molar tooth or sham operation. Mice were sacrificed 1 (n = 12/group), 2 (n = 6/group) or 4 (n = 6/group) weeks postoperatively. The right maxillae was disected. Micro-CT was used to quantify differences in bone microstructural features at extrction sites, between <i>CD24</i>-knockout mice and wild-type mice.</p><p>Results</p><p><i>CD24</i>-Knockout mice displayed impaired bone healing at extraction sites that was manifested as decreased trabecular bone density, and decreased number and thickness of trabeculae.</p><p>Conclusions</p><p>This pilot study suggests that CD24 plays an important role in extraction socket bone healing and may be used as a novel biomarker of bone quality and potential therapeutic target to improve bone healing and density following alveolar bone injury.</p></div

Study groups and number of animals per group.

<p>Study groups and number of animals per group.</p

Bone healing parameters at 4-weeks.

<p><b>A</b>. Trabecular thickness; <b>B</b>. Trabecular separation; <b>C</b>. Trabecular number; <b>D</b>. Bone surface/Bone volume. In wild type <i>C57BL</i>/6J mice, as compared with <i>CD24</i>-knockout mice, the bone surface was significantly smoother (p = 0.017); the trabeculae were significantly thicker (p = 0.035) and there was less bone marrow space (p = 0.014).</p