The automatic activity of abdominal muscles during stable and unstable standing postural tasks in older adults with and without low back pain- A cross-sectional study.

BACKGROUND: The postural control and abdominal muscles' automatic activity were found to be impaired in subjects with low back pain (LBP) during static activities. However, the studies are predominantly conducted on younger adults and a limited number of studies have evaluated abdominal muscles' automatic activity during dynamic standing activities in subjects with LBP. The present study investigated the automatic activity of abdominal muscles during stable and unstable standing postural tasks in older adults with and without LBP. METHODS: Twenty subjects with and 20 subjects without LBP were included. The thickness of the transversus abdominis (TrA), internal oblique (IO), and external oblique (EO) muscles was measured during rest (in supine), static, and dynamic standing postural tasks. To estimate automatic muscle activity, each muscle's thickness during a standing task was normalized to its thickness during the rest. Standing postural tasks were performed using the Biodex Balance System. RESULTS: The mixed-model analysis of variance revealed that task dynamicity significantly affected thickness change only in the TrA muscle (P = 0.02), but the main effect for the group and the interaction were not significantly different (P > 0.05). There were no significant main effects of the group, task dynamicity, or their interaction for the IO and EO muscles (P > 0.05). During dynamic standing, only the TrA muscle in the control group showed greater thickness changes than during the static standing task (P < 0.05). CONCLUSIONS: Standing on a dynamic level increased the automatic activity of the TrA muscle in participants without LBP compared to standing on a static level. Further research is required to investigate the effects of TrA muscle training during standing on dynamic surfaces for the treatment of older adults with LBP.

A gross abdominal wall hematoma secondary to transversus abdominis plane block.

We aimed to share our experience with an abdominal wall hematoma that developed after an ultrasonography-guided TAP block performed for the palliation of chronic abdominal wall pain. Bleeding was successfully stopped with coil embolization.

Acute gastric dilatation with segmented abdominal paresis as a rare manifestation of herpes zoster: a case report and review of the literature.

BACKGROUND: Herpes zoster is a common disease that can affect men and women at any age. Sensory neuropathy is the most common complication while motor neuropathy of the abdominal muscles is rare complication appearing in ~ 0.7% of patients. Furthermore, visceral nerve involvement causing gastroparesis is an extremely rare postherpetic complication. We present an extremely rare case of acute gastric dilatation with segmented abdominal paresis as a rare manifestation of herpes zoster infection. CASE PRESENTATION: A 91-year-old Asian man was admitted to hospital with 2-day history of vomiting and left abdominal protrusion. He was previously treated for a rash on the left abdominal wall as herpes zoster infection with oral valaciclovir 2 weeks prior. On physical examination, characteristic herpes zoster rash scars and an ipsilateral abdominal bulge were observed on the left side. Computed tomography revealed no abdominal wall defect, mass, or stenosis. Remarkable distension of the stomach, asymmetrical left flank wall bulge, and a thinner abdominal wall on the left compared with the right side were shown. He was diagnosed as acute gastric dilatation owing to gastroparesis and segmental paresis of the abdominal musculature associated with herpes zoster infection. The patient showed significant improvement in symptoms and abdominal paresis within a month of conservative treatment, including nasogastric tube decompression and mosapride administration. CONCLUSION: Acute gastric dilatation with abdominal paresis is an extremely rare complication of herpes zoster infection, and to date there have been no reports in the literature. It alerts us that, when examining patients with abdominal bulge, we should be conscious of this rare pathology for the optical diagnosis, avoiding unnecessary invasive examination or surgical exploration.

External Oblique Intercostal Plane Block Versus Port-Site Infiltration for Laparoscopic Sleeve Gastrectomy: A Randomized Controlled Study.

PURPOSE: Although laparoscopic sleeve gastrectomy (LSG) is a minimally invasive surgery, postoperative pain is common. A novel block, the external oblique intercostal (EOI) block, can be used as part of multimodal analgesia for upper abdominal surgeries. The aim of our study is to investigate the effectiveness of EOI block in patients undergoing LSG. MATERIALS AND METHODS: Sixty patients were assigned into two groups either EOI or port-site infiltration (PSI). The EOI group received ultrasound-guided 30 ml 0.25% bupivacaine, while the PSI group received 5 ml of 0.25% bupivacaine at each port sites by the surgeon. Data on clinical and demographic were collected and analyzed. RESULTS: There were no statistical differences in terms of demographic details (p > 0.05). VAS scores were statistically lower during resting at PACU, 1, 2, 4, 8, and 12 h postoperatively in the EOI group than PSI group (p < 0.05), The VAS scores were also lower during active movement at PACU, 1, 2, 4, and 8 h postoperatively in the EOI group than PSI group (p < 0.05). Twenty-four-hour fentanyl consumption was lower in the EOI than in the PSI group (505.83 ± 178.56 vs. 880.83 ± 256.78 µg, respectively, p < 0.001). Rescue analgesia was higher in PSI group than EOI group (26/30 vs. 14/30, respectively, p = 0.001). CONCLUSION: EOI block can be used as a part of multimodal analgesia due to its simplicity and effective postoperative analgesia in LSG.

Bilateral Spigelian Hernias Robotic Repair: A Novel Approach to a Rare Surgical Entity.

Spigelian hernias are an uncommon protrusion defect noted between the rectus abdominis and the transversus abdominis muscles, at the semilunar line, with a low incidence of approximately 0.12% to 2% of all ventral hernias. Furthermore, the incidence of bilateral cases is noted to be even lower in the general population. They are associated with bowel incarceration and strangulation; hence surgical repair is indicated. Therapeutic alternatives for Spigelian hernias include open repair, however laparoscopic repair stands as the standard of care in these cases. Feasible and successful robotic repair has been reported, with associated advantages in terms of visualization and surgical instrument dexterity. We present the first ever reported cases of bilateral Spigelian hernias repaired using robotic approach. Two female Puerto Rican patients referred to our institution complaining of abdominal pain, where imaging studies found bilateral Spigelian hernias. In both cases, a transabdominal preperitoneal repair was performed using the Da Vinci Surgical System. Both patients were discharged home tolerating oral intake with adequate wound healing. On follow up visits, patients denied abdominal discomfort and had adequate wound healing. Robotic surgery for Spigelian hernias poses an advantage over laparoscopic repair as improved visualization, mobility, and precision in movements allow for more gentle tissue manipulation. Furthermore, this is the first evidence of safe and effective repair in the uncommon entity of bilateral cases, providing a newer alternative in the setting of such presentation.

Ultrasound imaging of core muscles activity in multiparous women with vaginal laxity: a cross-sectional study.

Vaginal laxity (VL) is a common condition among multiparous women, especially those who have delivered vaginally. Since pelvic floor muscles (PFMs) work synergistically with other core muscles, physical therapy protocols that aim to treat VL should train the PFMs in combination with other core muscles. To investigate the activity of core muscles in multiparous women with and without VL, and its relation to sexual function. An observational, cross-sectional study. The study included 100 multiparous women, who were divided into two groups according to their scores on the vaginal laxity questionnaire (VLQ). Women who scored between 1 and 3 on the VLQ were categorized as having VL (n = 48), while those who scored between 5 and 7 were placed in the control group (n = 52). The primary outcomes were PFM displacement, diaphragmatic excursion, transversus abdominis activation ratio, and lumbar multifidus thickness measured by ultrasound imaging. The secondary outcome was sexual functioning, evaluated using the Arabic female sexual function index (ArFSFI). The VL group had significantly lower PFM displacement (mean difference (MD) - 0.42; 95% confidence interval (CI) - 0.49 to - 0.33; p = 0.001), diaphragmatic excursion (MD - 2.75; 95% CI - 2.95 to - 2.55; p = 0.001), lumbar multifidus thickness (MD - 10.08; 95% CI - 14.32 to - 5.82; p = 0.02), and ArFSFI scores (MD - 9.2; 95% CI - 10.59 to - 7.81; p = 0.001) in comparison to the control group (p < 0.05). Nevertheless, the transversus abdominis activation ratio demonstrated no significant difference between the two groups (MD 0.06; 95% CI - 0.05 to 0.17; p = 0.33). Multiparous women with VL had significantly lower PFM displacement, diaphragmatic excursion, lumbar multifidus thickness, and sexual function index scores than women in the control group. The only exception was transversus abdominis activation, which did not differ significantly between the VL and control groups.

Laparoscopic assisted versus ultrasound guided transversus abdominis plane block in laparoscopic bariatric surgery: a randomized controlled trial.

BACKGROUND: Transversus abdominis plane block (TAPB) guided by laparoscopy and ultrasound showed promise in enhancing the multimodal analgesic approach following several abdominal procedures. This study aimed to compare the efficacy and safety between Laparoscopic (LAP) TAP block (LTAP) and ultrasound-guided TAP block (UTAP) block in patients undergoing LAP bariatric surgery. PATIENTS AND METHODS: This non-inferiority randomized controlled single-blind study was conducted on 120 patients with obesity scheduled for LAP bariatric surgeries. Patients were allocated into two equal groups: LTAP and UTAP, administered with 20 mL of 0.25% bupivacaine on each side. RESULTS: There was no statistically significant difference in the total morphine consumption, Visual Analogue Scale (VAS) score at all times of measurements, and time to the first rescue analgesia (p > .05) between both groups. The duration of anesthesia and duration of block performance were significantly shorter in the LTAP group than in the UTAP group (p < .001). Both groups had comparable post-operative heart rate, mean arterial pressure, adverse effects, and patient satisfaction. CONCLUSIONS: In LAP bariatric surgery, the analgesic effect of LTAP is non-inferior to UTAP, as evidenced by comparable time to first rescue analgesia and total morphine consumption with similar safety blocking through the low incidence of post-operative complications and patient satisfaction. TRIAL REGISTRATION: The study was registered in Pan African Clinical Trials Registry (PACTR) (ID: PACTR202206871825386) on June 29, 2022.

L3W3 Incisional Hernia with LOD - Robotic eTEP-TAR Repair (with video).

video width="640" height="480" controls controlsList="nodownload" poster="https://www.revistachirurgia.ro/pdfs/video/Victor_Gheorghe_Radu_L3W3_Incisional_Hernia.jpg" style="margin-top: -20px;" source src="https://www.revistachirurgia.ro/pdfs/video/Victor_Gheorghe_Radu_L3W3_Incisional_Hernia.mp4" type="video/mp4" Your browser does not support the video tag. /video Introduction: The Rives-Stoppa procedure has emerged as the preferred method for ventral hernia repair, and the principles of this technique are similarly applied in minimally invasive surgery using the eTEP (enhanced view totally extraperitoneal) approach. It appears that the eTEP approach offers excellent outcomes in terms of less post-operative pain, faster recovery, and shorter hospital stays for patients undergoing abdominal wall reconstruction (AWR). It's important to note that there are some contra-indications of this procedure. In general, laparoscopic eTEP may not be suitable for cases with large hernias and loss of domain where the working space is limited. In such cases, alternative approaches, such as using a robotic platform, may be considered to ensure an adequate working space for abdominal wall reconstruction (AWR). A robotic platform can create a working space by using the robotic arms as a "laparo-lift," enabling the AWR to be performed. Case Report: In this case, we have a 65-year-old female patient with a BMI of 28.5 who presents with a large incisional hernia with LOD. This hernia is located on the right flank and occurred after a Jalaguier incision. The CT scan provided valuable information regarding the size of the hernia, the remaining volume of the abdominal cavity, and the content of the hernia sac. Based on these radiological details, the LOD diagnosis was confirmed using the Sabbagh equation, which revealed that the hernia volume accounted for 46.47% of the total peritoneal volume. Based on the location, size of the defect, and the EHS classification for incisional hernias, the diagnosis for this case is a Complex incisional hernia of L3 right W3 with LOD. The protocol for optimization in this case involves chemo-relaxation, which refers to the injection of botulinum toxin A (BTA) into the large lateral muscles of the abdomen. This is done approximately 6 weeks before the surgery. Based on the successful reduction of the hernia during the consultation, the decision has been made to perform the Abdominal Wall Reconstruction (AWR) procedure using the robotic eTEP-TAR technique. Conclusion: The post-operative course was favorable, with the patient experiencing early active mobilization, reduced pain, and early return of bowel movement. The patient was discharged the day after the surgery.

eTEP Rives-Stoppa impact on abdominal contour: a retrospective observational and clinical quality improvement study using Ellipse 9 tool.

BACKGROUND: The eTEP Rives-Stoppa (RS) procedure, increasingly used for ventral hernia repair, has raised concerns about postoperative upper abdominal bulging. This study aims to objectively evaluate changes in the abdominal contour after eTEP RS and explore potential causes using a novel analytical tool, the Ellipse 9. METHODS: Thirty patients undergoing eTEP RS without posterior rectus sheath closure were assessed before and 3 months after surgery using CT scan images. Key measurements analyzed included the distance between linea semilunaris (X2), eccentricity over the Cord (c/a Cord), superior eccentricity (c/a Sup), Y2, and the superior perimeter of the abdomen. The Ellipse 9 tool, which provides graphical images and numerical representations, was utilized alongside patient-reported outcomes to assess perceived abdominal changes. RESULTS: The study group exhibited a trend toward a flatter abdomen with reduced distance between linea semilunaris(X2). However, 17% of patients developed upper abdominal bulging (5). Significant differences in c/a Cord, c/a Sup, Y2, and the superior perimeter of the abdomen, confirmed with Bonferroni corrections, were noted between bulging (5 patients) and non-bulging groups (25 patients). There was a notable disparity between patient perceptions and objective outcomes. CONCLUSION: The eTEP RS procedure improved abdominal contour in most patients from a selected cohort. The Ellipse 9 tool was valuable for the objective analysis of these changes. The cause of bulging post-eTEP RS is probably multifactorial. Notably, there was often a discrepancy between patient perceptions of bulging and objective clinical findings.

COMPARISON OF ABDOMINAL EXERCISES AND NEUROMUSCULAR ELECTRICAL STIMULATION ON DIASTASIS RECTI ABDOMINIS MUSCLE IN POSTNATAL FEMALES WITH CAESAREAN SECTION.

The separation of the two rectus abdominis muscles along the linea alba is termed diastasis of recti abdominis muscles (DRAM). DRAM is a common health problem in people that are both pregnant and postpartum. With a 100% frequency at gestational week 35, it is extremely frequent during pregnancy. Control and function of the trunk are greatly influenced by the musculature of the abdomen. The existence, extent, and duration of DRAM have been connected to low back and pelvic discomfort however the relationship is not conclusive. It has been proven to weaken abdominal muscles and impair their functioning in lumbo-pelvic stability. Additionally, DRAM has been linked to pelvic floor dysfunction. The mechanical control and function of the abdomen can be compromised by diastasis recti, which compromises the abdominal muscles. This study examined the impact of abdominal exercises and neuromuscular electrical stimulation on the DRAM in postnatal females who underwent Caesarean section. A total of 208 individuals, aged between 20 and 34, who had recti diastasis measuring more than 2.5 cm, underwent screening. They were split into two groups at random. Group B only received abdominal exercises, whereas Group A received NMES in addition to their activities. For a period of 12 weeks, the intervention was given to both groups three times a week. Changes have been recorded before and after the intervention. The pressure biofeedback unit, measuring tape, and vernier caliper were employed to evaluate the outcome measures of inter-recti distance, abdominal muscle strength, and waist-hip ratio, respectively. In every outcome, both groups had a highly significant (p<0.05) improvement. Furthermore, after 12 weeks, group A had improved in all measures with highly significant (p<0.05) intergroup comparisons. In comparison to MNES alone, NMES can have a more significant effect on reducing DRAM in postpartum women when paired with abdominal Exercise.

Associations Between Visceral Fat, Abdominal Muscle, and Coronary Artery Calcification: A Cross-Sectional Analysis of the Multi-Ethnic Study of Atherosclerosis.

The associations of body composition components, including muscle and adipose tissue, and markers of subclinical coronary artery disease are unclear. We examined the relation between abdominal computed tomography (CT)-derived measures of the area and density of fat and muscle with coronary artery calcification (CAC), using data from the Multi-Ethnic Study of Atherosclerosis (MESA). A total of 1,974 randomly selected MESA participants free of coronary heart disease underwent abdominal CT scans at examinations 2 or 3, with the resulting images interrogated for abdominal body composition. Using 6 cross-sectional slices spanning L2 to L5, the Medical Imaging Processing Analysis and Visualization software was used to determine abdominal muscle and fat composition using appropriate Hounsfield units ranges. CT chest scans were used to obtain CAC scores, calculated using the Agatston method and spatially weighted calcium score. Multivariable linear and logistic regression analyses were performed to assess the relation between abdominal visceral fat and muscle area and density to prevalent CAC. A total of 1,089 participants had a CAC >0, with an average CAC score of 310. In the fully adjusted model, for every 10-cm2 increase in visceral fat area, the likelihood of having a CAC greater than 0 increased by 0.60% (p <0.001). In the minimally adjusted model, abdominal muscle area was significantly associated with CAC >0, which became nonsignificant in the fully adjusted model. For the density of visceral fat, every 1-Hounsfield unit increase (less lipid-dense fat tissue), the likelihood of having a CAC score >0 decreased by 0.29% (p <0.05). No significant relation was observed between density of abdominal muscle and CAC >0. A greater area and higher lipid density of abdominal visceral fat were associated with an increased likelihood of having CAC, whereas there was no significant relation between abdominal muscle area or density and CAC. The quantity and the quality of fat have associations, with an important marker of subclinical atherosclerosis, CAC, and their significance with respect to cardiovascular outcomes, require further evaluation.

Trunk-oriented Exercises Versus Whole-body Vibration on Abdominal Thickness and Balance in Children with Duchene Muscular Dystrophy.

OBJECTIVES: Progressive proximal muscle weakening in children with Duchenne muscular dystrophy (DMD) impairs postural adjustments by impairing motor function and preventing ambulation. During daily activities, for gait and dynamic balance, certain postural modifications are required. The objective was to compare the impact of trunk-oriented exercises versus whole-body vibration on abdominal muscle thickness and balance in children with DMD. METHODS: Participants in this study were 30 boys with DMD, aged 6 to 10 years old. Children were divided into two groups (A and B) randomly. Children in group (A) underwent a prescribed regimen of physical therapy along with trunk-oriented exercises, whereas group (B) received the same regimen as group (A) together with whole-body vibration three times per week for three consecutive months. Balance and the thickness of the abdominal muscles were measured using the Biodex balance system and ultrasonography, respectively, before and after therapy. RESULTS: When compared to the pre-treatment results in both groups, the post-treatment results showed a significant difference in all measured variables (p<0.05). Post-treatment values showed that all of the measured variables significantly differed in favor of group A. CONCLUSIONS: Trunk-oriented exercises can improve abdominal thickness and balance more effectively than whole-body vibration in children with DMD. CLINICALTRIALS: gov ID: NCT05688072.

Damage Control Laparotomy and Management of the Open Abdomen.

Management of the open abdomen has been used for decades by general surgeons. Techniques have evolved over those decades to improve control of infection, fluid loss, and improve the ability to close the abdomen to avoid hernia formation. The authors explore the history, indications, and techniques of open abdomen management in multiple settings. The most important considerations in open abdomen management include the reason for leaving the abdomen open, prevention and mitigation of ongoing organ dysfunction, and eventual plans for abdominal closure.

Efficacy of transversus abdominis plane block on postoperative nausea and vomiting: a meta-analysis of randomized controlled trial.

BACKGROUND: Postoperative nausea and vomiting (PONV) is a common postoperative complication, and Transversus abdominis plane (TAP) block can provide effective analgesia for surgical operation. However, but there is not enough evidence to prove its advantage for nausea and vomiting. The objective of this meta-analysis was to evaluate the efficacy of TAP block on PONV. METHODS: Two independent researchers conducted searches for randomized controlled trials (RCTs) in PubMed, Embase, and Cochrane Central Register of Controlled Trials. We used Review Manager software for meta-analysis. RESULTS: In this meta-analysis, twenty-six trials with 1981 patients were examined. The results showed that TAP block reduced postoperative nausea (Risk Difference (RD) = -0.10, 95% confidence interval (CI): -0.15 to -0.05) compared with no TAP block. TAP block reduced the dose of fentanyl (Standardized Mean Difference (SMD) = -1.17, 95% CI: -2.07 to -0.26) and morphine (SMD = -1.12, 95% CI: -2.10 to -0.13) compared with no TAP block, when the timing of administration was before surgery (RD = -0.13, 95% CI: -0.19 to -0.07). TAP block reduced postoperative nausea when the ropivacaine dosage is ≤ 100 mg (RD = -0.13, 95% CI: -0.21 to -0.06), bupivacaine dosage ≥ 100 mg ( RD = -0.08, 95% CI: -0.13 to -0.03), and when the ropivacaine concentration was ≤ 0.375% (RD = -0.11, 95% CI: -0.18 to -0.04). TAP block significantly reduced the incidence of nausea when the types of opioid drugs in PCA is tramadol (RD = -0.13, 95% CI: -0.24 to -0.03). TAP block could reduce the VAS (SMD= -0.99, 95% CI: -1.29 to -0.70) and reduce the time of extubation (SMD = -0.71, 95% CI: -1.34 to -0.08). CONCLUSION: The meta-analysis conducted in this study revealed that TAP block could reduce the incidence of PONV, and the efficacy of TAP block may be influenced by factors such as administration time, local anesthetic dosage and concentration, types of opioid drugs in PCA.

Lumbopelvic manipulation alone versus combined with dry needling in physically active patients with patellofemoral pain syndrome: A randomized clinical trial.

INTRODUCTION: Patellofemoral pain syndrome (PFPS) is prevalent in physically active people. The multifactorial nature of PFPS necessitates multimodal treatment for this condition. The present study aimed to compare the efficacy of lumbopelvic manipulation alone versus manipulation plus dry needling in physically active patients with PFPS. METHOD: Thirty patients (18 women and 12 men) with a diagnosis of PFPS entered this randomized controlled clinical trial and were divided into two groups: lumbopelvic manipulation alone or lumbopelvic manipulation plus dry needling. The interventions were applied for 3 sessions every other day. Dry needling was performed on the quadratus lumborum and gluteus medius muscles. Pain intensity, Kujala score and side-plank time were recorded at baseline, post-intervention and 1 month after the intervention. RESULTS: The results of Friedman's test showed statistically significant differences in pain and function in participants during the study period, and post hoc tests revealed differences between the two groups in behavior of the marginal means (p < 0.001). CONCLUSION: The use of lumbopelvic manipulation plus dry needling in the quadratus lumborum and gluteus medius muscles may be more effective than manipulation alone in alleviating pain and promoting function in physically active patients with PFPS.

Ultrasound-Guided External Oblique Intercostal Plane Block for Postoperative Analgesia in Laparoscopic Sleeve Gastrectomy: A Prospective, Randomized, Controlled, Patient and Observer-Blinded Study.

PURPOSE: The external oblique intercostal plane (EOI) block is a novel block technique for anterolateral upper abdominal wall analgesia. The superficial nature of the external oblique intercostal plane allows it to be easily identified even in patients with obesity. The aim of this study was to test the hypothesis that EOI block would reduce IV morphine consumption within 24 h after laparoscopic sleeve gastrectomy. MATERIALS AND METHODS: Patients were randomly assigned to one of two groups: EOI block group and control group. The patients in the EOI block group received ultrasound-guided bilateral EOI block with a total of 40 ml 0.25% bupivacaine after anesthesia induction. The patients in the control group received no intervention. Postoperatively, all the patients were connected to an intravenous patient controlled analgesia (PCA) device containing morphine. The primary outcome of the study was IV morphine consumption in the first postoperative 24 h. RESULTS: The median [interquartile range] morphine consumption at 24 h postoperatively was significantly lower in the EOI block group than in the control group (7.5 [3.5 to 8.5] mg vs 14 [12 to 20] mg, p = 0.0001, respectively). Numerical rating scale (NRS) scores at rest and during movement were lower in the EOI block group than in the control group at 2, 6, and 12 h but were similar at 24 h. No block-related complications were observed in any patients. CONCLUSION: The results of the current study demonstrated that bilateral EOI block reduced postoperative opioid consumption and postoperative pain in patients with obesity undergoing laparoscopic sleeve gastrectomy. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT05663658.

Activin is a neural inducer of a male-specific muscle in Drosophila.

Drosophila melanogaster has a pair of male-specific muscles called the muscle of Lawrence (MOL) in abdominal segment 5 (A5) of adult flies. The MOL is produced only when its innervating motoneuron expresses FruitlessM (FruM) neural masculinizing proteins. We show that MOL induction is hampered by: (1) silencing electrical activities in the motoneuron, (2) blocking vesicular release from the motoneuron, and (3) knocking down Activin ß (Actß) in the motoneuron or knocking down Actß signaling pathway components in the myoblasts. Our timelapse live imaging of the developing neuromuscular system reveals that, upon contact with the presumptive MOL, the motoneuronal axon retracts concomitant with the progression of MOL degeneration resulting from neural silencing. We conclude that MOL formation depends on the bidirectional trophic interactions between pre- and postsynaptic cells, with motoneuron-derived Actß playing an inducing role in MOL formation.