Clinical application of sensory protection of denervated muscle

Following proximal peripheral nerve injury, motor recovery is often poor due to prolonged muscle denervation and loss of regenerative potential. The transfer of a sensory nerve to denervated muscle results in improved functional recovery in experimental models. The authors here report the first clinical case of sensory protection. Following a total hip arthroplasty, this patient experienced a complete sciatic nerve palsy with no recovery at 3 months postsurgery and profound denervation confirmed electrodiagnostically. He underwent simultaneous neurolysis of the sciatic nerve and saphenous nerve transfers to the tibialis anterior branch of the peroneal nerve and gastrocnemius branch from the tibial nerve. He noted an early proprioceptive response. Electromyography demonstrated initially selective amelioration of denervation potentials followed by improved motor recovery in sensory protected muscles only. The patient reported clinically significant functional improvements in activities of daily living. The authors hypothesize that the presence of a sensory nerve during muscle denervation can improve functional motor recovery.     

From the Cover: Father's brain is sensitive to childcare experiences

Although contemporary socio-cultural changes dramatically increased fathers'' involvement in childrearing, little is known about the brain basis of human fatherhood, its comparability with the maternal brain, and its sensitivity to caregiving experiences. We measured parental brain response to infant stimuli using functional MRI, oxytocin, and parenting behavior in three groups of parents (n = 89) raising their firstborn infant: heterosexual primary-caregiving mothers (PC-Mothers), heterosexual secondary-caregiving fathers (SC-Fathers), and primary-caregiving homosexual fathers (PC-Fathers) rearing infants without maternal involvement. Results revealed that parenting implemented a global “parental caregiving” neural network, mainly consistent across parents, which integrated functioning of two systems: the emotional processing network including subcortical and paralimbic structures associated with vigilance, salience, reward, and motivation, and mentalizing network involving frontopolar-medial-prefrontal and temporo-parietal circuits implicated in social understanding and cognitive empathy. These networks work in concert to imbue infant care with emotional salience, attune with the infant state, and plan adequate parenting. PC-Mothers showed greater activation in emotion processing structures, correlated with oxytocin and parent-infant synchrony, whereas SC-Fathers displayed greater activation in cortical circuits, associated with oxytocin and parenting. PC-Fathers exhibited high amygdala activation similar to PC-Mothers, alongside high activation of superior temporal sulcus (STS) comparable to SC-Fathers, and functional connectivity between amygdala and STS. Among all fathers, time spent in direct childcare was linked with the degree of amygdala-STS connectivity. Findings underscore the common neural basis of maternal and paternal care, chart brain–hormone–behavior pathways that support parenthood, and specify mechanisms of brain malleability with caregiving experiences in human fathers.Throughout human history and across cultures, women have typically assumed primary caregiving responsibility for infants (1, 2). Although humans are among the few mammalian species where some male parental caregiving is relatively common, father involvement varies considerably within and across cultures, adapting to ecological conditions (1, 3). Involved fathering has been linked with children''s long-term physiological and social development and with increases in mothers'' caregiving-related hormones such as oxytocin and prolactin (3–6). In addition, animal studies demonstrated structural brain alterations in caregiving fathers (7, 8). It has been suggested that, although maternal caregiving is triggered by neurobiological processes related to pregnancy and labor, the human father''s brain, similar to other biparental mammals, adapts to the parental role through active involvement in childcare (1–3). Despite growing childcare involvement of fathers (3, 5, 6), mechanisms for human fathers'' brain adaptation to caregiving experiences remain largely unknown, and no study to our knowledge has examined the brain basis of human fatherhood when fathers assume primary responsibility for infant care.For social species with lengthy periods of dependence, parental caregiving is key to survival and relies on brain structures that maximize survival (2, 9). Animal studies have demonstrated that mammalian mothering is supported by evolutionarily ancient structures implicated in emotional processing, vigilance, motivation, and reward, which are rich in oxytocin receptors, including the amygdala, hypothalamus, nucleus accumbens, and ventral tegmental area (VTA), and that these regions are sensitive to caregiving behavior (9, 10). Imaging studies of human mothers found activation in similar areas, combined with paralimbic insula-cingulate structures that imbue infants with affective salience, ground experience in the present moment and enable maternal simulation of infant states (11–13). These structures implicate a phylogenetically ancient network of emotional processing that rapidly detects motivationally salient and survival-related cues (14) and enables parents to automatically identify and immediately respond to infant distress, thereby maximizing survival. In humans, this emotional processing network is complemented by a cortical mentalizing network of frontopolar-medial-prefrontal-temporo-parietal structures involved in social understanding, theory of mind, and cognitive empathy, including the medial prefrontal cortex (mPFC), frontopolar cortex, superior temporal sulcus (STS), and temporal poles (15). The mentalizing network plays an important role in individuals'' ability to infer mental states from behavior, is already activated during the parents'' first weeks of parenting, and enables parents to cognitively represent infant states, predict infant needs, and plan future caregiving (11–13).The few studies examining the human father''s brain showed activation in similar areas, including the STS, lateral and medial frontal regions, VTA, inferior frontal gyrus (IFG), and orbitofrontal cortex (OFC) (16, 17). Only one study compared maternal and paternal brain response to infant cues, reporting mothers'' greater amygdala activation, fathers'' greater superior-temporal and medial-frontal activation, and maternal and paternal oxytocin''s different associations with amygdala vs. cortical activation (18). Oxytocin, a nine-amino acid neuropeptide that underpins the formation of affiliative bonds (19), supports the development of human parental caregiving (20). Research has shown that maternal and paternal oxytocin levels are associated with parent–infant synchrony, which is the parent''s careful adaptation of caregiving behavior to infant''s social signals (21). However, although oxytocin levels are similar in mothers and fathers, oxytocin is differentially linked with the parent-specific repertoire, for instance, with affectionate contact in mothers and stimulatory play in fathers (5, 20).Ethological perspectives emphasize the importance of studying the neurobiology of parenting in its natural habitat and of using a behavior-based approach to test parents'' brain adaptation to ecological pressures (22). Consistent with findings in other mammals (10), studies on brain–behavior associations in human mothers describe links between mother–infant synchrony and brain activation in the mother''s subcortical regions, including the amygdala, nucleus accumebens, and hippocampus (11, 13). In contrast, the one study testing human fathers'' brain–behavior associations showed correlations with cortical activation (17). Overall, these findings suggest that distinct brain–hormone–behavior pathways may underpin maternal and paternal care; therefore, oxytocin and parenting behavior may be associated with the emotional processing network in mothers but with the socio-cognitive circuit in fathers. Furthermore, animal studies indicate that active caregiving in biparental fathers leads to greater integration of multiple brain networks involved in nurturance, learning, and motivation (7). Hence, active involvement in caregiving may possibly facilitate integration of both parenting-related networks in human fathers, particularly among those who undertake the primary caregiver role.The present study sought to examine the brain basis of human fatherhood by using a “natural experiment,” afforded for the first time in human history, to our knowledge, by contemporary socio-cultural changes. Throughout history, infants without mothers were cared for by other women (2). Current social changes enable the formation of two-father families raising children with no maternal involvement since birth (3). Such a context provides a unique setting to assess changes in the paternal brain on assuming the traditionally maternal role. Moreover, understanding mechanisms of brain adaptation to caregiving experiences in primary-caregiving fathers may shed further light on processes that refine all fathers'' responses to childcare activities.We visited the homes of two-parent families rearing their firstborn child: heterosexual mother-father couples comprising primary-caregiving mothers (PC-Mothers) and secondary-caregiving fathers (SC-Fathers) and homosexual couples comprising two primary-caregiving fathers (PC-Fathers) (SI Materials and Methods). We videotaped parent–infant interaction in the natural habitat, measured parental oxytocin, and used the videotaped parent–child interactions as stimuli for functional MRI (fMRI) to test parental brain response to infant-related cues. Five hypotheses were proposed. First, we expected activation in both subcortical areas involved in vigilance and reward and cortical circuits implicated in social understanding in all parents raising a young infant. Second, we expected greater subcortical activation in mothers, particularly in the amygdala, which has been repeatedly linked with mammalian mothering (23, 24), and greater activation in cortical socio-cognitive circuits in fathers. Third, the brain–hormone–behavior constellation underpinning maternal care was expected to center around the emotional-processing network, whereas the brain–hormone–behavior links in fathers were expected to coalesce with the socio-cognitive network. Fourth, consistent with the context-specific evolution of human fathering (1), we expected greater variability in fathers'' brain response as mediated by actual caregiving experiences. Such variability would be particularly noted among the primary-caregiving fathers raising infants without mothers and may involve functional integration of the subcortical and cortical networks subserving parenting. Finally, we expected that the pathways leading from the parent''s primary caregiving role to greater parent–infant synchrony would be mediated by parental brain activation and oxytocin levels.     

Total hip arthroplasty in patients with fibrous dysplasia: a modern update

BackgroundFibrous dysplasia (FD) results from an abnormality in lamellar bone formation and most frequently involves the proximal femur. This can lead to the development of osteoarthritis requiring total hip arthroplasty (THA). Such cases are challenging, and there is a lack of information guiding best management. As such, we devised a study assessing the outcomes and complications in patients with FD undergoing THA with modern implant technology, and we outlined our preferred surgical technique.MethodsA search of our institutional arthroplasty database was performed to identify patients who underwent THA for FD between January 2001 and July 2018 at Mount Sinai Hospital in Toronto, Canada. Data regarding implants used and the use of allograft material or metal augments or both were obtained. Complications and revision requirements were noted. Radiographic and clinical leg length discrepancies were assessed.ResultsA total of 10 hips in 9 patients who underwent THA for FD were identified. Mean follow-up time was 6.0 years (range 0.5 to 10.3 yr). The majority of patients underwent THA using uncemented femoral and acetabular components with large femoral heads on highly cross-linked polyethylene liners. Most cases (80% of hips) required allograft to the proximal femur. A single complication requiring revision was noted. In 90% of hip surgeries, the patient required transfusion of packed red blood cells. Mean radiographic and clinical leg length discrepancies were 0.9 cm (range −2.4 to 2.4 cm) and 0.9 cm (range −4 to 0 cm), respectively.ConclusionContrary to previous reports, low complication and revision rates were observed with cementless components and routine use of allograft material. The challenging nature of such cases warrants use of an experienced arthroplasty treatment team.