Outcomes of Deep Inferior Epigastric Artery Perforator (DIEP) Flap in Indian Population-A Prospective Single-Institute Study.

Introduction Breast reconstruction has become integral part of breast cancer treatment. Deep inferior epigastric perforator (DIEP)-based flap is considered the gold standard in autologous breast reconstruction. Aims and Objectives The aim of this study was to evaluate the patient satisfaction and the incidence of complications in DIEP flaps in an Indian setup for breast reconstruction. Materials and Methods This is a prospective, nonrandomized study at a single institute-Manipal Hospitals, Old Airport Road, Bangalore. Eligible patients were women aged between 28 and 60 years with primary breast cancer requiring mastectomy and radiotherapy, who consented for DIEP flap reconstruction. Results The study includes subjects who had autologous breast reconstruction after mastectomy with DIEP flap between January 2019 and August 2021 that included 31 patients with a minimum follow-up of 2 years. Four flaps were turbocharged and 17 flaps were superdrained primarily. The average operative time for the whole procedure by adopting a two-team approach is 353.8 ± 43.793 minutes. About 94.1% patients had excellent aesthetic score results. Six patients developed mastectomy flap necrosis, one had fat necrosis that was managed conservatively, whereas one patient had donor site re-exploration for hematoma. We had no DIEP flap necrosis, seroma, flap site hematoma, or flap failure. Physical well-being module of Breast-Q indicated an average of 83 points, psychosocial well-being module indicated 80 points, whereas sexual scores reverted an average of 77 points. Among satisfaction module, aesthetic outcomes for breast showed an average of 94 points, whereas the donor site had 96 points. Satisfaction with information, surgeon, medical staff each gained more than 87 points. Conclusion Breast reconstruction with DIEP flap yields good aesthetic outcomes and quality of life in Indian population. The incidence of fat necrosis, flap and donor site complications is less over time and will enhance the patient satisfaction score further.

Development of polarization-sensitive optical coherence tomography imaging platform and metrics to quantify electrostimulation-induced peripheral nerve injury in vivo in a small animal model.

Significance: Neuromodulation devices are rapidly evolving for the treatment of neurological diseases and conditions. Injury from implantation or long-term use without obvious functional losses is often only detectable through terminal histology. New technologies are needed that assess the peripheral nervous system (PNS) under normal and diseased or injured conditions. Aim: We aim to demonstrate an imaging and stimulation platform that can elucidate the biological mechanisms and impacts of neurostimulation in the PNS and apply it to the sciatic nerve to extract imaging metrics indicating electrical overstimulation. Approach: A sciatic nerve injury model in a 15-rat cohort was observed using a newly developed imaging and stimulation platform that can detect electrical overstimulation effects with polarization-sensitive optical coherence tomography. The sciatic nerve was electrically stimulated using a custom-developed nerve holder with embedded electrodes for 1 h, followed by a 1-h recovery period, delivered at above-threshold Shannon model k -values in experimental groups: sham control (SC, n = 5 , 0.0 mA / 0 Hz ), stimulation level 1 (SL1, n = 5 , 3.4 mA / 50 Hz , and k = 2.57 ), and stimulation level 2 (SL2, n = 5 , 6.8 mA / 100 Hz , and k = 3.17 ). Results: The stimulation and imaging system successfully captured study data across the cohort. When compared to a SC after a 1-week recovery, the fascicle closest to the stimulation lead showed an average change of + 4 % / - 309 % (SL1/SL2) in phase retardation and - 79 % / - 148 % in optical attenuation relative to SC. Analysis of immunohistochemistry (IHC) shows a + 1 % / - 36 % difference in myelin pixel counts and - 13 % / + 29 % difference in axon pixel counts, and an overall increase in cell nuclei pixel count of + 20 % / + 35 % . These metrics were consistent with IHC and hematoxylin/eosin tissue section analysis. Conclusions: The poststimulation changes observed in our study are manifestations of nerve injury and repair, specifically degeneration and angiogenesis. Optical imaging metrics quantify these processes and may help evaluate the safety and efficacy of neuromodulation devices.

Improved in vivo optical coherence tomography imaging of animal peripheral nerves using a prism nerve holder.

Significance: Modern optical volumetric imaging modalities, such as optical coherence tomography (OCT), provide enormous information about the structure, function, and physiology of living tissue. Although optical imaging achieves lateral resolution on the order of the wavelength of light used, and OCT achieves axial resolution on a similar micron scale, tissue optical properties, particularly high scattering and absorption, limit light penetration to only a few millimeters. In addition, in vivo imaging modalities are susceptible to significant motion artifacts due to cardiac and respiratory function. These effects limit access to artifact-free optical measurements during peripheral neurosurgery to only a portion of the exposed nerve without further modification to the procedure. Aim: We aim to improve in vivo OCT imaging during peripheral neurosurgery in small and large animals by increasing the amount of visualized nerve volume as well as suppressing motion of the imaged area. Approach: We designed a nerve holder with embedded mirror prisms for peripheral nerve volumetric imaging as well as a specific beam steering strategy to acquire prism and direct view volumes in one session with minimal motion artifacts. Results: The axially imaged volumes from mirror prisms increased the OCT signal intensity by > 22 dB over a 1.25-mm imaging depth in tissue-mimicking phantoms. We then demonstrated the new imaging capabilities in visualizing peripheral nerves from direct and side views in living rats and minipigs using a polarization-sensitive OCT system. Prism views have shown nerve fascicles and vasculature from the bottom half of the imaged nerve which was not visible in direct view. Conclusions: We demonstrated improved OCT imaging during neurosurgery in small and large animals by combining the use of a prism nerve holder with a specifically designed beam scanning protocol. Our strategy can be applied to existing OCT imaging systems with minimal hardware modification, increasing the nerve tissue volume visualized. Enhanced imaging depth techniques may lead to a greater adoption of structural and functional optical biomarkers in preclinical and clinical medicine.

The Role of Dermal Regeneration Template in Anterior Abdominal Wall Defect after Burst Abdomen: A Case Report in Acute Graft Versus Host Disease of the Gastrointestinal Tract in Aplastic Anemia.

Acute graft-versus-host disease of the gastrointestinal tract (GI-aGVHD) is a rare condition, often requiring multiple laparotomies, ultimately leading to a burst abdomen. We report the successful use of a dermal regeneration template (DRT), combined with negative pressure wound therapy (NPWT) and skin grafts, to reconstruct the abdominal skin in an 11-year-old boy. The patient was a case of aplastic anemia, who underwent bone marrow transfers, the first of which failed and the second one was successful. He eventually developed gastrointestinal GVHD. Repeated laparotomies were done for recurrent intestinal obstruction. He also underwent resection anastomosis and end ileostomy, after which he developed an anterior abdominal wall defect due to a burst abdomen. After 12 months of management with multiple dressings, NPWT, and DRT, a stable coverage was achieved, without skin retraction. We report our experience in anterior abdominal wall reconstruction in a case of GI-aGVHD using DRT.

Temporary Extrathoracic Vacuum Therapy Splint in Chest Wall Reconstruction.

Background Paradoxical respiration is a sinister consequence of bony chest cage defects which can persist even post chest wall reconstruction. It leads to prolonged dependence on mechanical ventilation postoperatively, thereby delaying recovery. Methods Negative pressure wound therapy (NPWT) was applied in early postoperative period to a patient with chest wall defect reconstructed with folded prolene mesh and free anterolateral thigh flap. Arterial blood gas (ABG), fraction of inspired oxygen (FiO 2 ), peak end expiratory pressure (PEEP), oxygen saturation (SpO 2 ), and blood pressure (BP) readings pre and post NPWT application were compared. Results There was marked improvement in the breathing mechanics and related parameters post NPWT application over the flap. Conclusions Negative extrathoracic pressure in the form of a temporary splint can enable early weaning off the ventilator and a smoother postoperative recovery in reconstructed chest wall defects.

Sex Differences in Vagus Nerve Stimulation Effects on Rat Cardiovascular and Immune Systems.

BACKGROUND: Investigations into the benefits of vagus nerve stimulation (VNS) through pre-clinical and clinical research have led to promising findings for treating several disorders. Despite proven effectiveness of VNS on conditions such as epilepsy and depression, understanding of off-target effects and contributing factors such as sex differences can be beneficial to optimize therapy design. NEW METHODS: In this article, we assessed longitudinal effects of VNS on cardiovascular and immune systems, and studied potential sex differences using a rat model of long-term VNS. Rats were implanted with cuff electrodes around the left cervical vagus nerve for VNS, and wireless physiological monitoring devices for continuous monitoring of cardiovascular system using electrocardiogram (ECG) signals. ECG morphology and heart rate variability (HRV) features were extracted to assess cardiovascular changes resulting from VNS in short-term and long-term timescales. We also assessed VNS effects on expression of inflammatory cytokines in blood during the course of the experiment. Statistical analysis was performed to compare results between Treatment and Sham groups, and between male and female animals from Treatment and Sham groups. RESULTS: Considerable differences between male and female rats in cardiovascular effects of VNS were observed in multiple cardiovascular features. However, the effects seemed to be transient with approximately 1-h recovery after VNS. While short-term cardiovascular effects were mainly observed in male rats, females in general showed more significant long-term effects even after VNS stopped. We did not observe notable changes or sex differences in systemic cytokine levels resulting from VNS. COMPARISON WITH EXISTING METHODS: Compared to existing methods, our study design incorporated wireless physiological monitoring and systemic blood cytokine level analysis, along with long-term VNS experiments in unanesthetized rats to study sex differences. CONCLUSION: The contribution of sex differences for long-term VNS off-target effects on cardiovascular and immune systems was assessed using awake behaving rats. Although VNS did not change the concentration of inflammatory biomarkers in systemic circulation for male and female rats, we observed significant differences in cardiovascular effects of VNS characterized using ECG morphology and HRV analyses.

Vagus Nerve Stimulation Unequally Disturbs Circadian Variation of Cardiac Rhythms in Male and Female Rats.

Vagus nerve stimulation (VNS) is a neurostimulation therapy for epilepsy and severe depression and has been recently shown to be effective for other conditions. Despite its demonstrated safety and efficacy, long-term and off-target effects of VNS remain to be fully determined. One of the complications reported in epilepsy is stimulation-induced sleep abnormalities. As epilepsy itself can impact sleep quality, contribution of VNS alone in such off-target effects remain mainly unknown. In this study, we analyzed data from long-term VNS experiments in rats to characterize effects of VNS on circadian rhythms derived from heart rate and heart rate variability (HRV). We have also explored possible sex differences in long-term effects of VNS on intrinsic biological rhythms. Compared with control animals, significant VNS-induced changes in circadian rhythms were observed particularly in female rats over 24h and 6h light cycles (1PM-7PM). These findings enhance our understanding of VNS contribution and biological sex role on sleep difficulties reported by using VNS therapy.

Assessment of Functional Recovery and Subjective Donor-Site Morbidity Following Radial Forearm Flap Reconstruction in Small- to Moderate-Sized Palatal Defects.

CONTEXT: Palatal defects are encountered following tumor extirpation, trauma, or congenitally. Among the known alternatives, radial artery free forearm flap (RAFF) is a versatile flap that confers good results in head and neck reconstruction, but donor-site morbidity has been an issue of discontent among the plastic surgeons. This limitation needs to be studied further and addressed considering the unmatched quality of this tissue. AIMS: This study aims to weigh the impact of the functional edge of this flap against the unpopular donor-site morbidity on a group of patients. SETTINGS AND DESIGN: This is a retrospective analysis of recuperation of palatal function and patient concerns with the donor-site function and cosmesis on 7 consecutive patients with small-to-moderate palatal defects reconstructed with RAFF. METHODS AND MATERIALS: Postoperative recovery of speech, palatal movement, and restoration of oromaxillary interface was assessed using objective tests, such as speech intelligibility testing and articulation studies. Simultaneously, subjective donor-site function and cosmesis were assessed using Patient Scar Assessment Scale (PSAS), Upper Extremity Functional Index (UEFI), and donor limb sensory testing. RESULTS AND CONCLUSION: Mean PSAS score was 8.28/60, and UEFI score reported was 77/80, which reflect high patient satisfaction with the donor site. Nasoendoscopy shows remarkable restoration of palate anatomy. Intelligibility testing depicts near-normal speech understandability, whereas articulation studies revealed distortions post-palatal reconstruction with RAFF. Radial artery free forearm flap should be considered as the forerunner of reconstruction in palatal defects involving less than 50%.

Limb Salvage in an Extensive, Complicated Vascular Lesion of the Arm in an Infant.

When a vascular lesion involving a limb poses a hazard to the life, treatment options are excision or amputation of the limb. Although excision can be hazardous, limb salvage with vascular control is the best treatment option. We report limb salvage in an infant with an extensive infected congenital hemangioma complicated with consumptive coagulopathy.

Assessment of miniaturized ultrasound-powered implants: an in vivo study.

OBJECTIVE: Therapeutic applications of implantable active medical devices have improved the quality of patient life. Numerous on-going research in the field of neuromodulation and bioelectronic medicine are exploring the use of these implants for treating diseases and conditions. Miniaturized implantable medical devices that are wirelessly powered by ultrasound (US) can be placed close to the target sites deep inside the body for effective therapy with less invasiveness. In this study, we assessed the long-term in vivo performance of miniaturized US powered implants (UPI) using a rodent model. APPROACH: Prototype UPI devices were implanted in rodents and powered wirelessly using an unfocused US transmitter over 12 weeks, and the corresponding device output was recorded. Structural integrity of UPI before and after implantation was studied using scanning electron microscopy (SEM). We also conducted qualitative histological assessment of skin and muscle surrounding the UPI and compared it to naïve control and US exposed tissues. MAIN RESULTS: We found that it is feasible to power UPI devices wirelessly with US over long-term. The encapsulation of UPIs did not degrade over time and the tissues surrounding the UPI were comparable to both naïve control and US exposed tissues. SIGNIFICANCE: This study is the first to assess the long-term performance of miniaturized UPI devices using a rodent model over 12-weeks. The set of tests used in this study can be extended to assess other US-powered miniaturized implants.

A Study of Aesthetic and Functional Outcome Following Structural Fat Grafting for Facial Scars and Contour Deformity.

STUDY DESIGN: This is a prospective observational study of 60 consecutive cases with facial scars and contour deformity who underwent structural fat grafting. OBJECTIVES: The aim of the present article is to highlight how fat grafting helps to improve aesthetic and functional outcome in facial scars and contour deformities. It also highlights the factors that need to be considered while planning autologous fat grafting to get better aesthetic results. METHODS: This is a prospective observational study of 60 consecutive cases with facial scars and contour deformity. The study was conducted from May 2014 to April 2019 in a tertiary care hospital. All the patients were followed up for a minimum period of 1 year from the date of surgery. Assessment of post-operative aesthetic outcome, in terms of satisfaction, was done using the Visual Analogue Scale (VAS), which ranges from 1 to 10 by the patient and operative surgeon. RESULTS: The mean age was 30.8 9.8 years. Out of 60 patients, 20 patients underwent additional procedure like dermabrasion and collagen dressing to improve aesthetic outcome. Among 60 patients, 24 patients had transient edema and 10 patients had bruising at the recipient site. There were no major donor site complications except pain which was managed conservatively. Mean patient satisfaction score is 7 and mean surgeon satisfaction score is 7.25. CONCLUSION: Despite the ongoing concerns about survival and longevity of fat grafts and also unpredictability of long-term outcomes, fat grafting has become a very useful surgical tool to improve the quality of facial scars and correct contour deformity. Our series shows excellent outcome both clinically as well as from the patient satisfaction. Future research is warranted in the fields of the adipocyte derived stem cells and to expand the clinical application of fat grafting.

A Novel Way of Standardization of ICG Lymphangiography Reporting.

Background Indocyanine green (ICG) lymphangiography is being increasingly employed to assess the severity of lymphedema, locate the areas of patent linear lymphatics and dermal backflow and plan treatment. This study suggests a novel method of reporting ICG findings in extremities to enable easy understanding among surgeons and physiotherapists and avoid repeat testing when a patient visits a disparate lymphedema center or clinician. Methods A reporting protocol was developed in the lymphedema clinic of the plastic surgery department, and patients were asked to bring along the report in every subsequent review. The ICG findings were recorded on the fluorescence imaging system as well. The report was prepared by one and analyzed by two different clinicians without repeating the test on 10 consecutive patients. Results The interrater reliability of findings in the report was found to be 98.7% among the three clinicians. Conclusion The reporting system was found to be illustratable and reproducible.

A rat model for assessing the long-term safety and performance of peripheral nerve electrode arrays.

BACKGROUND: High-resolution peripheral nerve interfaces (PNIs) can provide amputees with intuitive motor control and sensory feedback. Current PNIs are limited by early device failure and suboptimal long-term stability. The present study aims to incorporate functional assessment into an in vivo test platform to assess the long-term safety and performance of PNIs for recording and stimulation. NEW METHODS: Utah electrode arrays (EA) were implanted in the rat sciatic nerve along with electromyography wires in the gastrocnemius and tibialis anterior. Cranial EEG screws were implanted in the somatosensory cortex for 12 weeks. Spontaneous neural activity was recorded using the implanted EA and stimulation-induced activity was monitored throughout the experiment. The impedance of each electrode was measured, and nerve function tests were conducted throughout the EA lifetime. Post-hoc safety assessments included scanning electron microscopy (SEM) of the EA and nerve histomorphometric analysis. RESULTS: EA recordings were stable, and stimulation with EA elicited somatosensory evoked potentials and muscle contractions. Motor and sensory function tests indicated minimal deficits. Histomorphometric analysis indicated changes in nerve microstructure. SEM indicated EA-tip fracture, while lead wire breakage primarily caused device failure. COMPARISON WITH EXISTING METHODS: We improved our prior platform with the addition of functional assessments of sensory pathways, a robust EMG array design to increase device longevity, and quantitative analysis of nerve microstructure. CONCLUSION: We present a test platform for long-term assessment of peripheral nerve interfaces for stimulation and recording. Using this platform, we demonstrate recording and stimulation with minimal impact on nerve function, while EA lead wire breakage and tip fracture could limit long-term device use.

Toward optical coherence tomography angiography-based biomarkers to assess the safety of peripheral nerve electrostimulation.

OBJECTIVE: Peripheral nerves serve as a link between the central nervous system and its targets. Altering peripheral nerve activity through targeted electrical stimulation is being investigated as a therapy for modulating end organ function. To support rapid advancement in the field, novel approaches to predict and prevent nerve injury resulting from electrical stimulation must be developed to overcome the limitations of traditional histological methods. The present study aims to develop an optical imaging-based approach for real-time assessment of peripheral nerve injury associated with electrical stimulation. APPROACH: We developed an optical coherence tomography (OCT) angiography system and a 3D printed stimulating nerve stabilizer (sNS) to assess the real-time microvascular and blood flow changes associated with electrical stimulation of peripheral nerves. We then compared the microvascular changes with established nerve function analysis and immunohistochemistry to correlate changes with nerve injury. MAIN RESULTS: Electrical stimulation of peripheral nerves has a direct influence on vessel diameter and capillary flow. The stimulation used in this study did not alter motor function significantly, but a delayed onset of mechanical allodynia at lower thresholds was observed using a sensory function test. Immunohistochemical analysis pointed to an increased number of macrophages within nerve fascicles and axon sprouting potentially related to nerve injury. SIGNIFICANCE: This study is the first to demonstrate the ability to image peripheral nerve microvasculature changes during electrical stimulation. This expands the knowledge in the field and can be used to develop potential biomarkers to predict nerve injury resulting from electrical stimulation.

Long-term in vivo performance of novel ultrasound powered implantable devices.

Neuromodulation devices have been approved for the treatment of epilepsy and seizures, with many other applications currently under research investigation. These devices rely on implanted battery powered pulse generators, that require replacement over time. Miniaturized ultrasound powered implantable devices have the potential to eliminate the need for batteries in neuromodulation devices. While these devices have been assessed in vitro, long-term in vivo assessment is required to determine device safety and performance. In this study, we developed a multi-stage long-term test platform to assess the performance of miniaturized ultrasound powered implantable devices.

Characterizing Longitudinal Changes in the Impedance Spectra of In-Vivo Peripheral Nerve Electrodes.

Characterizing the aging processes of electrodes in vivo is essential in order to elucidate the changes of the electrode⁻tissue interface and the device. However, commonly used impedance measurements at 1 kHz are insufficient for determining electrode viability, with measurements being prone to false positives. We implanted cohorts of five iridium oxide (IrOx) and six platinum (Pt) Utah arrays into the sciatic nerve of rats, and collected the electrochemical impedance spectroscopy (EIS) up to 12 weeks or until array failure. We developed a method to classify the shapes of the magnitude and phase spectra, and correlated the classifications to circuit models and electrochemical processes at the interface likely responsible. We found categories of EIS characteristic of iridium oxide tip metallization, platinum tip metallization, tip metal degradation, encapsulation degradation, and wire breakage in the lead. We also fitted the impedance spectra as features to a fine-Gaussian support vector machine (SVM) algorithm for both IrOx and Pt tipped arrays, with a prediction accuracy for categories of 95% and 99%, respectively. Together, this suggests that these simple and computationally efficient algorithms are sufficient to explain the majority of variance across a wide range of EIS data describing Utah arrays. These categories were assessed over time, providing insights into the degradation and failure mechanisms for both the electrode⁻tissue interface and wire bundle. Methods developed in this study will allow for a better understanding of how EIS can characterize the physical changes to electrodes in vivo.

Short-Time Fourier Transform Based Spike Detection of Spontaneous Peripheral Nerve Activity.

Peripheral nerve interfaces are designed to record neural activity from residual nerves in amputees. Reliable detection of neural events from these recordings dictate the performance of neuroprosthetic device control. Extraction of neural events from peripheral nerve recordings is challenging because of low signal to noise ratio (SNR), sparse spiking pattern and the presence of electromyographic signal contamination from the surrounding muscles. In this study, we developed a spike detection algorithm based on Short-time Fourier Transform (STFT) and compared its performance to simple thresholding technique using synthesized nerve recordings. To mimic peripheral nerve recordings and produce ground-truth for validation, a quasi-simulation framework is proposed to incrementally synthesize signals from physiological recordings. A detection threshold was optimized on the spectral features of simulated signals and performance evaluation was done using an independent simulated data set. Results show that the STFT based technique, compared to the simple thresholding, reduces the false detection rate even in recordings with moderately low SNR.

Extended adipofascial wrap around radial forearm flap for hard palate reconstruction.

BACKGROUND: While using radial forearm free flap in palate reconstruction, the pedicle lies in the nasal floor, constantly exposed to the nasal secretions and turbulent air current. To overcome this problem, we have designed a procedure which utilises the adipofascial extension to wrap the pedicle and nasal side of the flap. MATERIALS AND METHODS: The study was done during 2017 and 2018, 2 years' period. Totally 13 consecutive patients with defect in the palate status post-oncological resection and those in whom local flaps were not enough to cover the defect were included into the study. These patients were divided into two groups. First group in whom adipofascial extension was not used to cover the pedicle and second group in whom adipofascial extension was used to cover the pedicle. The incidence of nasal crusting, secondary haemorrage, blow out and flap necrosis were analysed and compared. RESULTS: In Group 1, we had 2 among 6 (33%) patients with secondary haemorrage. One patient had partial flap loss. On exploring, we noticed thrombosis of cephalic vein. We did not had any incidence of blow out of the pedicle. In Group 2, none of the patients had any secondary haemorrage. All flaps healed well. On doing nasal endoscopy at 6 months of follow-up, all flaps showed complete mucosalisation at the nasal side. CONCLUSION: Use of adipofascial extension while planning a radial forearm free flap to cover the nasal side of the flap and pedicle in the nasal floor helps to reduce the nasal crusting and secondary haemorrhage.

Asymmetric Sensory-Motor Regeneration of Transected Peripheral Nerves Using Molecular Guidance Cues.

Neural interfaces are designed to decode motor intent and evoke sensory precepts in amputees. In peripheral nerves, recording movement intent is challenging because motor axons are only a small fraction compared to sensory fibers and are heterogeneously mixed particularly at proximal levels. We previously reported that pain and myelinated axons regenerating through a Y-shaped nerve guide with sealed ends, can be modulated by luminar release of nerve growth factor (NGF) and neurotrophin-3 (NT-3), respectively. Here, we evaluate the differential potency of NGF, glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), pleiotrophin (PTN), and NT-3 in asymmetrically guiding the regeneration of sensory and motor neurons. We report that, in the absence of distal target organs, molecular guidance cues can mediate the growth of electrically conductive fascicles with normal microanatomy. Compared to Y-tube compartments with bovine serum albumin (BSA), GDNF and NGF increased the motor and sensory axon content, respectively. In addition, the sensory to motor ratio was significantly increased by PTN (12.7:1) when compared to a BDNF + GDNF choice. The differential content of motor and sensory axons modulated by selective guidance cues may provide a strategy to better define axon types in peripheral nerve interfaces.