[Comparison of the efficacy of gasless robotic surgery through transaxillary apporach and open surgery for papillary thyroid carcinoma].

Objective: To compare the efficacy of gasless robotic surgery through transaxillary approach and open surgery for papillary thyroid carcinoma (PTC). Methods: The data of patient undergoing robotic surgery through transaxillary approach and traditional open surgery for PTC at the Sun Yat-sen Memorial Hospital, Sun Yat-sen University, from November 2016 to June 2023 were retrospectively analyzed. A 1∶1 propensity score matching (PSM) was performed to balance age, sex, extent of surgery, tumor size, capsule invasion, and multifocality. Surgical data, postoperative pathological data, complications, postoperative 2-month visual analog scale (VAS) scores for aesthetics, and follow-up data were compared between the two groups. Results: A total of 728 PTC patients were included. There were 339 patients in the robotic group, among which 262 were female (77.3%) and 77 were male (22.7%), with the age of [M (Q1, Q3)] 39 (32, 46) years and a body mass index (BMI) of 22.8 (20.7, 25.0) kg/m². Meanwhile, 389 patients were in the open group, among which 290 were female (74.6%) and 99 were male (25.4%), with the age of 47 (38, 55) years and a BMI of 23.2 (21.3, 25.5) kg/m2. Further analysis after PSM (there were 264 cases in both groups) showed that in the subtotal thyroidectomy and central neck dissection (LT+CCND) subgroup, the robotic group had longer operative time, higher blood loss, and greater drainage volume compared with the open group [100 (80, 130) min vs 60 (50, 80) min; 10 (10, 20) ml vs 10 (10, 20) ml; 103 (69, 145) ml vs 75 (57, 98) ml; all P<0.001], and the central lymph node metastasis rate was higher in the robotic group [45.6% (57/125) vs 31.8% (47/148), P=0.019]. In the total thyroidectomy and central neck dissection (TT+CCND) subgroup, the robotic group also had longer operative time, higher blood loss, and greater drainage volume compared with the open group [150 (110, 180) min vs 85 (75, 100) min; 20 (10, 20) ml vs 10 (10, 20) ml; 155 (107, 206) ml vs 90 (70, 120) ml; all P<0.001]. The incidence of chest skin numbness at 3 months postoperatively was higher in the robotic group compared with the open group (12.9% vs 0, P<0.001), while there were no statistically significant differences in other postoperative complications (all P>0.05). The VAS score at 2 months postoperatively was higher in the robotic group compared with the open group [9 (9, 9) vs 8 (7, 9), P<0.001]. Three cases of contralateral lobe recurrence occurred in the open group, while there were no case of recurrence in the robotic group. The 5-year overall survival rate was 100.0% in both the robotic and open groups, and there was no statistically significant difference in the 5-year disease-free survival rate between the robotic and open groups (100.0% vs 98.6%, P=0.068). Conclusion: Gasless robotic surgery through transaxillary approach for total thyroidectomy or lobectomy in the treatment of PTC is safe, feasible, and effective, with good cosmetic outcomes and comparable efficacy to traditional surgery.

[Value of the endoscopic diagnosis on the lesions of the skull base in postradiotherapeutic patients with nasopharyngeal carcinoma].

Objective: To evaluate the diagnostic value of the endoscopic biopsy operation to the lesions of the skull base in the patients with nasopharyngealcarcinoma after radiotherapy. Methods: From February 2006 to February 2010, 84 patients with nasopharyngeal carcinoma suffered from the lesions of the skull base after radiotherapy were included in this study. The relationship between the pathologic results of endoscopic biopsies from the skull base and the imaging results by Magnetic Resonance Imaging(MRI) was compared and discussed. The relationship between the pathologic results and more than 2-years' follow-up was also investigated. Results: There were 71 cases with clivus, 5 cases with pterygopalatine fossa and infratemporal fossa, 4 cases with parapharyngeal space, and 4 cases with cavernous sinus. The pathologic results of endoscopic biopsies indicated that 35 cases with recurrence including 30 case with poorly differentiated squamous cell carcinomas, 5 cases with cancer nests, 49 cases with non-tumor. Chi-square test showed that there was close relationship between MRI and pathologic results (P<0.05). In the patients followed up over 2 years, the pathologic results showed 28 cases with recurrence, 48 cases with non-tumor. MRI showed 36 cases with recurrence, 40 cases with non-tumor. But during follow-up, 30 cases were proved to be recurrent and 46 cases had non-tumor. However, Chi-square test showed that there was no statistically significance between the pathological results and follow-up(P=0.62). The sensitivity, specificity and diagnostic accuracy of the endoscopic diagnosis were 90.0%, 97.8% and 95.0%. Chi-square test also showed that there was no statistically significance between MRI and follow-up (P=0.24). The sensitivity, specificity and diagnostic accuracy of MRI were 80.0%, 73.9% and 76.0%. Conclusions: The endoscopic method is a specific, sensitive, safe, effective and minimally invasive in diagnosis of lesions of the skull base in postradiotherapeutic patients with nasopharyngeal carcinoma.

[Preliminary outcomes of neoadjuvant chemoimmunotherapy combined with transoral robotic surgery for locally advanced oropharyngeal squamous cell carcinoma].

Objective: To evaluate the efficacy of neoadjuvant chemoimmunotherapy (NACI) combined with transoral robotic surgery (TORS) in the treatment of locally advanced oropharyngeal squamous cell carcinoma (OPSCC). Methods: This was a retrospective study of 15 patients with locally advanced OPSCC who underwent TORS after neoadjuvant therapy (NAT) at the Department of Otolaryngology-Head and Neck Surgery of Sun Yat-sen Memorial Hospital of Sun Yat-sen University from April 2019 to February 2023. There were 12 males and 3 females, aged 31 to 74 years. Twelve cases were tonsil cancer, and 3 cases were tongue base cancer. There were 11 cases in stage Ⅲ and 4 cases in stage Ⅳ. Two patients received neoadjuvant chemotherapy and 13 patients received NACI, with 2 to 3 cycles, and all patients underwent TORS after multidisciplinary team consultation. The clinicopathological characteristics, surgical outcomes, and oncological results were summarized. Results: All surgeries were successfully completed with negative surgical margins, and no case was required conversion surgery. All patients were fed via nasogastric tubes postoperatively, with a median gastric tube stay of 7 days (range: 2-60 days). No tracheotomy was applied. There were no major complications such as postoperative bleeding. Pathological complete response (pCR) was found in 10 cases (76.9%) among the 13 patients with NACI. The follow-up time was 21 months (range: 10-47 months), and there was no death or distant metastasis. One patient with rT0N3M0 tonsil cancer had local recurrence 5 months after surgery. The 2-year overall survival and 2-year disease-free survival were respectively 100.0% and 93.3% in the 15 patients. Conclusion: NACI combined with TORS provides a safe, effective and minimally invasive treatment for patients with locally advanced oropharyngeal squamous cell carcinoma.

[Preliminary experience of gasless transoral vestibular robotic thyroidectomy].

Objective: To explore the feasibility and safety of the gasless transoral vestibular robotic thyroidectomy using skin suspension. Methods: The clinical data of 20 patients underwent gasless transoral vestibular robotic thyroidectomy in the Department of Otorhinolaryngology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University from February 2022 to May 2022 were retrospectively analyzed. Among them, 18 were females and 2 were males, aged (38.7±8.0) years old. The intraoperative blood loss, operation time, postoperative hospital stay, postoperative drainage volume, postoperative pain visual analogue scale (VAS) score, postoperative swallowing function swallowing impairment score-6 (SIS-6), postoperative aesthetic VAS score, postoperative voice handicap index-10 (VHI-10) voice quality, postoperative pathology and complications were recorded. SPSS 25.0 was used for statistical analysis of the data. Results: The operations were successfully completed without conversion to open surgery in all patients. Pathological examination showed papillary thyroid carcinoma in 18 cases, retrosternal nodular goiter in 1 case, and cystic change in goiter in 1 case. The operative time for thyroid cancer was 161.50 (152.75, 182.50) min [M (P25, P75), the same below] and the average operative time for benign thyroid diseases was 166.50 minutes. The intraoperative blood loss 25.00 (21.25, 30.00) ml. In 18 cases of thyroid cancer, the mean diameter of the tumors was (7.22±2.02) mm, and lymph nodes (6.56±2.14) were dissected in the central region, with a lymph node metastasis rate of 61.11%. The postoperative pain VAS score was 3.00 (2.25, 4.00) points at 24 hours, the mean postoperative drainage volume was (118.35±24.32) ml, the postoperative hospital stay was 3.00 (3.00, 3.75) days, the postoperative SIS-6 score was (4.90±1.58) points at 3 months, and the postoperative VHI-10 score was 7.50 (2.00, 11.00) points at 3 months. Seven patients had mild mandibular numbness, 10 patients had mild cervical numbness, and 3 patients had temporary hypothyroidism three months after surgery and 1 patient had skin flap burn, but recovered one month after surgery. All patients were satisfied with the postoperative aesthetic effects, and the postoperative aesthetic VAS score was 10.00 (10.00, 10.00). Conclusion: Gasless transoral vestibular robotic thyroidectomy using skin suspension is a safe and feasible option with good postoperative aesthetic effect, which can provide a new treatment option for some selected patients with thyroid tumors.

[Transoral robotic nasopharyngectomy for local recurrent nasopharyngeal carcinoma].

Objective: To investigate the safety, efficacy, locally control and survival results of transoral Da Vinci robotic surgery for salvage treatment of locally recurrent nasopharyngeal carcinoma. Methods: This retrospective study included 33 patients with locally recurrent nasopharyngeal carcinoma (stage rT1-2, partial rT3) underwent transoral Da Vinci robotic surgery between October 2017 and January 2020. There were 20 males and 11 females, with an average age of (47.9±10.5) years. The lesions were localized in nasopharyngeal cavity in 14 cases, with extending to parapharyngeal space in 6 cases and the floor of sphenoid sinus in 13 cases. Transnasal endoscopy was used to assist surgery if necessary. SPSS 25.0 statistical software was used for statistical analysis. Results: Transoral robotic nasopharyngectomy was successfully performed in all cases without conversion to open surgery, of which 13 cases were combined with transnasal endoscopic surgery. The average operation time was (126.2±30.0) min, ranging from 90 to 180 min. The postoperative pathological margin was R0 (31 cases) and R1 (2 cases), with no tumor residue. Complications of surgery mainly included symptoms of headache, nasal dryness and velopharyngeal insufficiency without nasopharyngeal hemorrhage. Follow-up time was from 3 to 54 months. One case had tumor recurrence 11 months after operation, 1 case had ipsilateral cervical lymph node metastasis 27 months after operation, 2 cases had distant metastasis and 1 case died of nasopharyngeal hemorrhage 3 months after operation. The 1-year, 2-year and 3-year overall survival rates were 97.0%, 96.0% and 92.9%, respectively and the local recurrence free rates were 97.0%, 95.7% and 91.7%, respectively. Conclusion: Transoral robotic nasopharyngectomy is safe and feasible for local recurrent nasopharyngeal carcinoma in selected patients, with higher local control rate and quality of life.

[Preliminary experience of robotic lateral neck dissection via combined axillary-retroauricular approach for N1b papillary thyroid carcinoma].

Objective: To evaluate the feasibility, safety, and short-term efficacy of robotic lateral neck dissection via combined axillary-retroauricular approach for N1b papillary thyroid carcinoma (PTC). Methods: Thirty patients with cT1-2N1bM0 PTC who received robotic lateral neck dissection via combined axillary-retroauricular approach were included in the Department of Otorhinolaryngology of Sun Yat-sen Memorial Hospital from December 2016 to December 2020. There were 10 males and 20 females, with a median age of 34.5 years and a median body mass index of 25.55 kg/m2. The clinical, surgical, complications, pathology and follow-up data were analysed with SPSS 25.0 software package. Results: The median operative time of 30 patients was 255.50 min, the median operative blood loss was 69.00 ml, and the median postoperative hospital stay was 6.00 days. The incidence of postoperative temporary recurrent laryngeal nerve paralysis was 3.33% (1/30), temporary hypoparathyroidism was 16.67%(5/30), temporary accessory nerve injury was 3.33% (1/30), hematoma was 3.33% (1/30) and chylous leakage was 3.33% (1/30). The median visual analogue scale (VAS) score was 8.00, and the follow-up time was 13-38 months, with a median of 25.5 months. One case showed cervical lymph node recurrence 14 months after surgery. The most recent dynamic recurrence risk stratification showed 21 patients (70.00%) had excellent responses. Conclusions: Robotic lateral neck dissection via combined axillary-retroauricular approach for unilateral cN1b PTC is safe, feasible and aesthetic. The short-term efficacy and dynamic recurrence risk stratification results of short-term follow-up are satisfactory. It can provide a surgical option for cN1b PTC patients.

[Robot-assisted transaxillary thyroidectomy: our early experience].

Objective:To evaluate the feasibility, effectiveness and safety of robot-assisted transaxillary thyroidectomy (RATT).Method: The clinical data of 66 patients undergoing RATT from November 2016 to May 2018 were prospectively collected and analyzed. The average age was (38.61±11.72) years, 57 cases were female and 9 cases were male. Preoperative fine needle aspiration biopsy revealed papillary thyroid carcinoma in 58 cases and follicular thyroid tumor in 8 cases.Result:All the patients successfully completed RATT, and there was no open operation, in which 54 cases of ipsilateral lobetomy and isthmus resection and ipsilateral central lymph node dissection, 8 cases with ipsilateral lobectomy and contralateral near-total lobectomy, and total thyroidectomy with ipsilateral central lymph node dissection and selective neck dissection combined with retroauricular approach in 4 cases. The mean operative time was (124.30±23.41) min, and the average bleeding volume was (17.73±8.28) ml. The mean diameter of thyroid papillary carcinoma was (0.71±6.22) cm, and the postoperative drainage volume was (67.57±25.11) ml. The average postoperative hospitalization time was (3.24±0.81) days. 3 cases (4.5%) had temporary laryngeal nerve palsy after operation, and 1 case (1.5%) had temporary hypocalcemia after operation, all recovered after one month. No postoperative bleeding, subcutaneous emphysema, drinking water cough and permanent hypocalcemia were observed. The average numbers of lymph node dissection in PTC patients were (6.26±4.76), of which 21 cases (36.2%) had lymph node metastasis, postoperative stage T1 54 cases, T2 4 cases, N1a 17 cases, N1b 4 cases. The follow-up time were 1-18 months. The postoperative cosmetic VAS score in January was (9.66±0.54). Ultrasound showed no residual glands in the affected thyroid gland, and there was no recurrence in the local and regional regions.Conclusion:RATT is safe and feasible with good aesthetic effect and can be used as an option for the treatment of thyroid diseases..

[Robotic nasopharyngectomy via combined approach of nose and oral for local recurrent nasopharyngeal carcinoma].

Objective:Surgery is one of the salvage treatments for recurrent nasopharyngeal carcinoma. The safety and efficacy of Da Vinci's robotic surgery was preliminarily investigated to resect recurrent nasopharyngeal cancer after one-course radiotherapy.Method:Since Oct 2017, Da Vinci surgery system was used to complete the operation of locally recurrent nasopharyngeal carcinoma including two approaches, such as trans oral with soft palate incision and trans oral and nose with soft palate suspended.Result:Ten patients underwent robotic nasopharyngectomy, The median operation time was 90 minutes, median follow-up time was 6 months, and all patients had clear resection margins. There was no residual, recurrent or cancer related death during short-term follow-up.Conclusion:Robotic nasopharyngectomy via combined approach of nose and mouth is safe, effective and has good local control.

[The significance of preservation of the supraclavicular nerve in endoscopic thyroidectomy via gasless anterior chest approach].

Objective: To evaluate the significance for the preservation of the supraclavicular nerve in endoscopic thyroidectomy via gasless anterior chest approach. Methods: We retrospectively evaluated 168 patients who underwent unilateral endoscopic thyroidectomy via gasless anterior chest approach, with preservation of the medial branch of the supraclavicular nerve in 110 patients and not in other 58 patients. Semmes-Weinstein monofilament (SWM) test and a visual analogue scale (VAS) were used to assess the recovery of sensation in anterior chest within 1-12 months postoperatively. Difference in the scores of SWM or VAS between groups was tested with Mann-Whitney U test, and the rates of SWM and VAS scores returning to normal levels in individual periods after surgery was compared with Chi-square test. Results: The preserved group showed more favorable results than the non-preserved group in both SMW and VAS scores. Compared to control group, SWM score in preserved group possessed a higher rate recovery to normal level at any period after operation, which was close to complete normality in 7-9 months postoperatively, and SWM score in non-preserved group was still partially normal in 10-12 months from surgery. Preferable results for VAS were also found in the preserved group, except no significant difference in VAS between groups in1-3 months or 10-12 months after operation. Conclusion: Preservation of the medial branch of the supraclavicular nerve in endoscopic thyroidectomy via gasless anterior chest approach can improve sensation recovery in anterior chest, thus improving postoperative quality of life of patients.

[Gasless endoscopic selective lateral neck dissection via an anterior chest approach for papillary thyroid carcinomas].

Objective: To assess the safety and curative effect of gasless endoscopic selective lateral neck dissection (GESLND) via an anterior chest approach for papillary thyroid carcinoma (PTC). Methods: Eighteen patients with PTC(T1-2N1bM0, size<3.0 cm), having GESLND via an anterior chest approach, were included from November 2008 to December 2016. Results: GESLND via an anterior chest approach was successfully performed in all 18 PTC patients (seven male and eleven female) with 83.3% of T1 and 16.7% of T2. The mean operative time of selective lateral neck dissection was 73 min (range 51-92 min). The mean of intraoperative bleeding was 61.1 ml (range 30-120 ml). No major complications occurred except one transient hypoparathyroidism. No residual thyroid glands were detected on ultrasonography and thyroglobulin was(0.73±0.16)ng/ml three months postoperatively. The median of follow-up was 54.5 months (range 6-104 months). No recurrence disease was observed in any patient on ultrasonography, computer tomography, thyroglobulin or selective iodine-131 scan during the follow-up period. The cosmetic result and functional preservation was excellent, when the assessments were performed three months postoperatively. Conclusion: GESLND via an anterior chest approach is feasible and safe for selected PTCs, with superior appearance.

Corticomotoneuronal connections in the rat: evidence from double-labeling of motoneurons and corticospinal axon arborizations.

In order to investigate the possibility of direct corticomotoneuronal (CM) connections in the rat, an anterograde-retrograde double-labeling method was developed. Phaseolus vulgaris-leucoagglutinin (PHA-L) anterograde tracing of corticospinal axons was combined with retrograde labeling of spinal motoneurons either by a conjugate of choleragen subunit B with horseradish peroxidase (CB-HRP) or by wheat germ agglutinin (WGA). The location of PHA-L injection unilaterally in the forelimb area of sensorimotor cortex and the CB-HRP or WGA injections in corresponding contralateral wrist or digit extensors or flexors were determined and matched on the basis of movement responses elicited by intracortical microstimulation. Light microscopic observation showed, in addition to the main contralateral dorsal corticospinal tract (CST), the presence of four other CST minor components in the contralateral lateral, ipsilateral ventral, and ipsilateral dorsal funiculi of the cervical spinal white matter and at the base of contralateral dorsal horn of the gray matter, respectively. PHA-L-labeled CST axonal arbors were observed from Rexed's lamina I through lamina X of contralateral spinal gray matter, most extensively in laminae VI and VII; some CST axons reached the zone of motoneuronal somata in lamina IX and a few of them also entered the lateral and occasionally the ventral funiculi, ramifying in the white matter. Between the zones of PHA-L-labeled CST axonal arbors on the one hand and CB-HRP/WGA labeled spinal motoneuronal somata with their extensive dendritic trees on the other, there was a large overlap, covering partly both the gray and the white matter. PHA-L-labeled axonal boutons (en passant or terminaux) were seen to contact the dendrites or even the somata of motoneurons in the gray matter, according to light-microscopic criteria for identification of synaptic contacts. Axodendritic CM contacts were occasionally observed in the lateral funiculus of the white matter as well. In general, only a single contact was observed between an individual PHA-L-labeled CST axon and a given retrogradely labeled motoneuron. In contrast to the common notion that direct CM connections are a specialty of primates, the present morphological data support the presence of direct CM connections also in some other mammals, such as the rat.

Improvement of the tetramethyl benzidine reaction with ammonium molybdate as a stabilizer for light and electron microscopic ligand-HRP neurohistochemistry, immunocytochemistry and double-labelling.

Ammonium heptamolybdate (AHM) was used as a stabilizing agent in the tetramethyl benzidine (TMB) reaction of choleragen subunit B conjugated horseradish peroxidase (CB-HRP) neurohistochemistry (TMB-AHM method). In comparison with Mesulam's TMB method employing sodium nitroprusside as a stabilizing agent (TMB-SNP method), the TMB-AHM procedure offers a similar sensitivity with regard to the visualization of CB-HRP labelled neurons and their extranuclear Golgi-phobic dendrites. However, it is less sensitive for the demonstration of anterogradely transported CB-HRP in axon terminals. At the nearly physiological pH value of the reaction medium (pH 6-8), it demonstrates better preservation of tissue and cell structures in the reacted sections. Under the electron microscope, the specific reaction product can be clearly distinguished and little damage of cellular and subcellular structures occurred. Preliminary application of TMB-AHM method to choleragen subunit B (CB) immunocytochemistry and double labelling technique which paired the neuronal tracing methods of HRP neurohistochemistry and CB immunocytochemistry, was also carried out with small modification.

Patterns of corticothalamic terminations following injection of Phaseolus vulgaris leucoagglutinin (PHA-L) in the sensorimotor cortex of the rat.

The morphology and spatial distribution of terminals emitted by corticothalamic axons originating from the rat motor cortex (as defined by intracortical microstimulations) were studied using Phaseolus vulgaris leucoagglutinin (PHA-L) as an anterograde tracer. After PHA-L injection in the face, forelimb or hindlimb motor cortical areas, small and densely packed boutons (about 1 micron in diameter), en passant and terminaux, were seen in the ventrolateral nucleus of the thalamus and, more sparsely, in the reticular nucleus, the nucleus ventrobasalis and the posterior nucleus of the thalamus. A separate projection with giant boutons (5-10 microns in diameter), en passant and terminaux, terminated in the posterior nucleus of the thalamus exclusively. Giant boutons originated from corticothalamic axons distinct from those providing small boutons. The corticothalamic projection originating from the motor cortex has basic organizational properties comparable to previous data obtained in the auditory and somatosensory corticothalamic projection systems.

[Ammonium molybdate as stabilizing agent in tetramethyl benzidine reaction of CB-HRP neurohistochemistry and its application to electron microscopy and immunocytochemistry].

Ammonium molybdate (AHM) was used as a stabilizing agent in the tetramethyl benzidine (TMB) reaction of choleragen subunit B conjugated horseradish peroxidase (CB-HRP) neurohistochemistry. In comparison with Mesulam's TMB method using sodium nitroprusside (SNP) as stabilizing agent, this new stabilizer offers similar sensitivity in regard to visualization of CB-HRP labelled neurons and their extranuclear Golgi-phobic dendrites. The nearly physiological pH (6-8) of the reaction medium demonstrates better preservation of tissue and cell structures of reacted sections and avoids non-specific needle-like crystal formation. Under the electron microscope, the histochemical reaction products can be clearly distinguished, without the usual shrinkage or distention of cellular and subcellular structures. This method was also applied with success to immunocytochemistry through small modifications.

Biomechanical characterization of ventricular-arterial coupling during aging: a multi-scale model study.

Left ventricular-arterial (VA) coupling has been recognized to be of great significance in understanding both the global and local mechanical performance of the circulatory system. In this study, a closed-loop multi-scale model of the human cardiovascular system is established for the purpose of studying the coupled VA hemodynamic changes during aging. Obtained results show that age-associated changes in arterial properties have some negative but relatively small influences on left ventricular (LV) mechanical performance, whereas they progressively increase LV and aortic systolic pressures, and aortic pulse pressure during aging. Wave analysis reveals that increased aortic characteristic impedance and premature wave reflection induced by arterial stiffening are two coexistent factors responsible for aortic systolic hypertension and increased aortic pulse pressure at old age. In contrast, aortic dilatation can partly counteract the negative influences of arterial stiffening. Coupled LV-systolic and arterial stiffening (a constant VA coupling index) well preserves LV mechanical performance given normal LV diastolic function during aging, but with a concomitant further elevation of LV and aortic systolic pressures. Furthermore, it is found that the states of arterial, LV-systolic and diastolic stiffness can be distinguished by investigating the sensitivity of LV-systolic pressure to various cardiac indices.

Trajectory of redirected corticospinal axons after unilateral lesion of the sensorimotor cortex in neonatal rat; a phaseolus vulgaris-leucoagglutinin (PHA-L) tracing study.

The corticospinal neurons of the rat project almost exclusively to the contralateral spinal cord. Retrograde and anterograde tracing experiments showed that only about 2-4% of the corticospinal neurons of the sensorimotor cortex project to the ipsilateral spinal cord in the normal rat. The large majority of corticospinal axons (more than 90%) travel at spinal level at the base of the contralateral dorsal funiculus; in addition a few axons run in the contralateral lateral funiculus and at the base of the dorsal horn. The undecussated axons run in the ipsilateral dorsal (about 1-2%) and ventral (about 1-2%) funiculi. The rearrangement of the corticospinal projections was studied with various tracing methods in rats subjected to unilateral lesion of the sensorimotor cortex at Postnatal Day 2 to 4. Spinal injections of the tracer WGA-HRP that were restricted to the side opposite to the cortical lesion showed a significant increase of retrogradely labeled corticospinal neurons in the intact cortex as compared to the proportion of ipsilateral projections in control experiments. This was consistent with an increased density of anterogradely labeled corticospinal terminals in the spinal cord ipsilateral to an injection of WGA-HRP in the motor cortex opposite to neonatal lesion, in comparison to normal rats. The trajectory of these "aberrant" ipsilateral corticospinal projections resulting from the neonatal lesion of the opposite sensorimotor cortex was analyzed by means of the anterograde tracer phaseolus vulgaris-leucoagglutinin (PHA-L), injected in the motor cortex. These data indicated that decussated corticospinal axons recross at spinal levels, close to their terminal zone, where they appear to ramify and terminate in the spinal gray including the motoneurons. Such recrossing axons thus represent one new possible mechanism, among other previously reported ones, contributing to the increase of ipsilateral corticospinal projections in rats subjected to neonatal cortical lesion.