Oncological Outcomes of Transoral Laser Microsurgery for Early Stage Glottic Cancer with Involvement of the Anterior Commissure

OBJECTIVES

To assess the value of carbon dioxide transoral laser microsurgery (CO2 TOLMS) for early-stage glottic cancer with special regard to involvement of the anterior commissure (AC).

STUDY DESIGN

Single-center retrospective cohort study.

SETTING

Grade-A tertiary hospital.

METHODS

A retrospective analysis of patients with early-stage (Tis-T2) glottic cancer who underwent CO2 TOLMS. All patients had at least 2 years of follow-up. The univariate and multivariate survival analyses were used to identify the risk factors for recurrence and the Kaplan-Meier method was used to analyze OS and DSS rates.

RESULTS

A total of 102 patients were included in the study. Eleven patients (10.78%) had recurrence. The univariate analysis showed that the recurrence was associated with the AC classification, T staging, tumor size, and tobacco use (P < .05). However, on multivariate analysis, the AC classification was the only independent risk factor for recurrence (P < .001, HR = 3.179). AC classification were distributed as follows: 59 (57.84%) AC0, 29 (28.43%) AC1, 8 (7.84%) AC2, and 6 (5.88%) AC3, 2-year/5-year OS and DSS rates were progressively reduced in the AC0, AC1, AC2, and AC3 groups (P < .001). At the same T staging, the OS rates incrementally decreased as the level of involvement of the AC became higher (P = .004).

CONCLUSION

CO2 TOLMS is an effective treatment for early-stage glottic cancer. AC involvement is an independent risk factors for recurrence and poor prognosis. The AC classification system may be better at grading the prognosis of patients with early-stage glottic cancer and has prognostic value independent of T staging.

Astrocytes of the Anterior Commissure Regulate the Axon Guidance Pathways of Newly Generated Neocortical Neurons in the Opossum Monodelphis domestica

In marsupials, upper-layer cortical neurons derived from the progenitors of the subventricular zone of the lateral ventricle (SVZ) mature morphologically and send their axons to form interhemispheric connections through the anterior commissure. In contrast, eutherians have evolved a new extra callosal pathway, the corpus callosum, that interconnects both hemispheres. In this study, we aimed to examine neurogenesis during the formation of cortical upper layers, including their morphological maturation in a marsupial species, namely the opossum (Monodelphis domestica). Furthermore, we studied how the axons of upper layers neurons pass through the anterior commissure of the opossum, which connects neocortical areas. We showed that upper-layer II/III neurons were generated within at least seven days in the opossum neocortex. Surprisingly, these neurons expressed special AT-rich sequence binding protein 2 (Satb2) and neuropilin 1 interacting protein (Nrp1), which are proteins known to be essential for the formation of the corpus callosum in eutherians. This indicates that extrinsic, but not intrinsic, cues could be key players in guiding the axons of newly generated cortical neurons in the opossum. Although oligodendrocyte precursor cells were present in the neocortex and anterior commissure, newly generated upper-layer neurons sent unmyelinated axons to the anterior commissure. We also found numerous GFAP-expressing progenitor cells in both brain structures, the neocortex and the anterior commissure. However, at P12-P17 in the opossums, a small population of astrocytes was observed only in the midline area of the anterior commissure. We postulate that in the opossum, midline astrocytes allow neocortical axons to be guided to cross the midline, as this structure resembles the glial wedge required by fibers to cross the midline area of the corpus callosum in the rodent.

Insights into morphometry and topography of corpus callosum among Indians

Corpus callosum is one of the major association fibre of brain performs an integral role of integration and communication of information between the two hemispheres. 50 formalin fixed cerebral hemispheres (25 right and 25 left) were used for the study. The longitudinal and vertical length of brain, longitudinal length and height of corpus callosum, distance of corpus callosum from various landmarks such as frontal and occipital pole, anterior commissure, lamina terminalis, and highest point on parietal pole and width of different parts of corpus callosum and height were measured. Results were analysed statistically. The results showed positive correlation between the longitudinal dimension of brain and all other parameters. Morphometric variation in size and its relation to nearby structures are seen in many neurological and psychiatric conditions such as Alzheimer's disease, Schizophrenia and bipolar disorders. Hence the present study can be used as reference by neurologist, neurosurgeons and psychiatrists.

Horizontal middle partial laryngectomy with cricothyroidopexy: an effective treatment for stage T1b glottic carcinoma

BACKGROUND

The current treatment options for T1b glottic carcinoma often lead to poor treatment outcomes or voice quality.

OBJECTIVES

This study evaluates the therapeutic efficacy of horizontal middle partial laryngectomy with cricothyroidopexy (HMPL-CTP) for stage T1b glottic carcinoma.

MATERIAL AND METHODS

A retrospective analysis was conducted on 73 patients with T1b glottic carcinoma. The patients were categorized into three groups: Group A (n = 22) underwent transoral laser microsurgery (TLMS), Group B (n = 21) received frontolateral vertical partial laryngectomy (FVPL), and Group C (n = 30) underwent HMPL-CTP. The study analyzed the 5-year overall survival rate (OS), recurrence rate, phonatory status, and incidence of laryngeal stenosis.

RESULTS

Voice quality scores varied significantly in the three groups, while the 5-year OS were similar. The local recurrence rate is higher in Group A than in the other two groups. The laryngeal stenosis rate in Group B is higher than in Groups A and C. Adhesions in the anterior commissure were observed in 18 cases in Group A and nine cases in Group C.

CONCLUSIONS AND SIGNIFICANCE

HMPL-CTP demonstrates efficacy as a treatment for stage T1b glottic carcinoma, offering favorable preservation of laryngeal function and minimal complications.

Electrophysiological Evidence for Interhemispheric Connectivity and Communication in Young Human Infants

Little is known empirically about connectivity and communication between the two hemispheres of the brain in the first year of life, and what theoretical opinion exists appears to be at variance with the meager extant anatomical evidence. To shed initial light on the question of interhemispheric connectivity and communication, this study investigated brain correlates of interhemispheric transmission of information in young human infants. We analyzed EEG data from 12 4-month-olds undergoing a face-related oddball ERP protocol. The activity in the contralateral hemisphere differed between odd-same and odd-difference trials, with the odd-different response being weaker than the response during odd-same trials. The infants' contralateral hemisphere "recognized" the odd familiar stimulus and "discriminated" the odd-different one. These findings demonstrate connectivity and communication between the two hemispheres of the brain in the first year of life and lead to a better understanding of the functional integrity of the developing human infant brain.

Oligodendrocytes Prune Axons Containing α-Synuclein Aggregates In Vivo: Lewy Neurites as Precursors of Glial Cytoplasmic Inclusions in Multiple System Atrophy?

α-Synucleinopathies are spreading neurodegenerative disorders characterized by the intracellular accumulation of insoluble aggregates populated by α-Synuclein (α-Syn) fibrils. In Parkinson's disease (PD) and dementia with Lewy bodies, intraneuronal α-Syn aggregates are referred to as Lewy bodies in the somata and as Lewy neurites in the neuronal processes. In multiple system atrophy (MSA) α-Syn aggregates are also found within mature oligodendrocytes (OLs) where they form Glial Cytoplasmic Inclusions (GCIs). However, the origin of GCIs remains enigmatic: (i) mature OLs do not express α-Syn, precluding the seeding and the buildup of inclusions and (ii) the artificial overexpression of α-Syn in OLs of transgenic mice results in a burden of soluble phosphorylated α-Syn but fails to form α-Syn fibrils. In contrast, mass spectrometry of α-Syn fibrillar aggregates from MSA patients points to the neuronal origin of the proteins intimately associated with the fibrils within the GCIs. This suggests that GCIs are preassembled in neurons and only secondarily incorporated into OLs. Interestingly, we recently isolated a synthetic human α-Syn fibril strain (1B fibrils) capable of seeding a type of neuronal inclusion observed early and specifically during MSA. Our goal was thus to investigate whether the neuronal α-Syn pathology seeded by 1B fibrils could eventually be transmitted to OLs to form GCIs in vivo. After confirming that mature OLs did not express α-Syn to detectable levels in the adult mouse brain, a series of mice received unilateral intra-striatal injections of 1B fibrils. The resulting α-Syn pathology was visualized using phospho-S129 α-Syn immunoreactivity (pSyn). We found that even though 1B fibrils were injected unilaterally, many pSyn-positive neuronal somas were present in layer V of the contralateral perirhinal cortex after 6 weeks. This suggested a fast retrograde spread of the pathology along the axons of crossing cortico-striatal neurons. We thus scrutinized the posterior limb of the anterior commissure, i.e., the myelinated interhemispheric tract containing the axons of these neurons: we indeed observed numerous pSyn-positive linear Lewy Neurites oriented parallel to the commissural axis, corresponding to axonal segments filled with aggregated α-Syn, with no obvious signs of OL α-Syn pathology at this stage. After 6 months however, the commissural Lewy neurites were no longer parallel but fragmented, curled up, sometimes squeezed in-between two consecutive OLs in interfascicular strands, or even engulfed inside OL perikarya, thus forming GCIs. We conclude that the 1B fibril strain can rapidly induce an α-Syn pathology typical of MSA in mice, in which the appearance of GCIs results from the pruning of diseased axonal segments containing aggregated α-Syn.

Differential impacts of Cntnap2 heterozygosity and Cntnap2 null homozygosity on axon and myelinated fiber development in mouse

Over the last decade, a large variety of alterations of the Contactin Associated Protein 2 (CNTNAP2) gene, encoding Caspr2, have been identified in several neuronal disorders, including neurodevelopmental disorders and peripheral neuropathies. Some of these alterations are homozygous but most are heterozygous, and one of the current challenges is to estimate to what extent they could affect the functions of Caspr2 and contribute to the development of these pathologies. Notably, it is not known whether the disruption of a single CNTNAP2 allele could be sufficient to perturb the functions of Caspr2. To get insights into this issue, we questioned whether Cntnap2 heterozygosity and Cntnap2 null homozygosity in mice could both impact, either similarly or differentially, some specific functions of Caspr2 during development and in adulthood. We focused on yet poorly explored functions of Caspr2 in axon development and myelination, and performed a morphological study from embryonic day E17.5 to adulthood of two major brain interhemispheric myelinated tracts, the anterior commissure (AC) and the corpus callosum (CC), comparing wild-type (WT), Cntnap2 ^-/- and Cntnap2 ^+/- mice. We also looked for myelinated fiber abnormalities in the sciatic nerves of mutant mice. Our work revealed that Caspr2 controls the morphology of the CC and AC throughout development, axon diameter at early developmental stages, cortical neuron intrinsic excitability at the onset of myelination, and axon diameter and myelin thickness at later developmental stages. Changes in axon diameter, myelin thickness and node of Ranvier morphology were also detected in the sciatic nerves of the mutant mice. Importantly, most of the parameters analyzed were affected in Cntnap2 ^+/- mice, either specifically, more severely, or oppositely as compared to Cntnap2 ^-/- mice. In addition, Cntnap2 ^+/- mice, but not Cntnap2 ^-/- mice, showed motor/coordination deficits in the grid-walking test. Thus, our observations show that both Cntnap2 heterozygosity and Cntnap2 null homozygosity impact axon and central and peripheral myelinated fiber development, but in a differential manner. This is a first step indicating that CNTNAP2 alterations could lead to a multiplicity of phenotypes in humans, and raising the need to evaluate the impact of Cntnap2 heterozygosity on the other neurodevelopmental functions of Caspr2.

Radiological Findings in Laryngeal Anterior Commissure Invasion: CT Scan Highlights

OBJECTIVES

Preoperative anterior commissure (AC) evaluation in glottic cancer is crucial for therapeutic decisions. Endoscopy is often inadequate to precisely detect the presence of cancer in the AC; thus, computed tomography (CT) scan could help. We investigated the relation between AC thickness on CT scan (in mm), AC involvement by cancer at histology, and radiologic signs of anterior paraglottic space (PGS) infiltration.

STUDY DESIGN

Retrospective observational study.

METHODS

An experienced radiologist retrospectively measured AC thickness and identified signs of anterior PGS infiltration on pretreatment contrast-enhanced CT scans of 80 patients with primary glottic cancer. The gold standard to define the presence of cancer in the AC was histology. The receiver operating characteristic (ROC) curves were used to determine the potential cut-off values of AC thickness (Youden index method) able to maximize both sensitivity and specificity in identifying the presence of cancer in the AC at histology and PGS infiltration on CT scan.

RESULTS

AC was significantly thicker in patients with cancer in the AC at histology (P < .001) and in patients with PGS infiltration on CT scan (P < .001). The cut-off values to discriminate the presence of cancer at histology and PGS infiltration on CT scan were 3.62 and 2.6 mm, respectively. We found a substantial agreement between anterior PGS infiltration on CT scan and the presence of cancer in the AC at histology (Cohen Kappa: P = .70).

CONCLUSION

AC thickness and radiologic signs of PGS infiltration on pretreatment CT scan could represent a method to predict the presence of cancer in the AC at histology.

LEVEL OF EVIDENCE

4 Laryngoscope, 132:2427-2433, 2022.

Prognostic and Treatment Differences Between T1a and T1b Glottic Cancer

OBJECTIVES

This study was designed to evaluate significant differences in treatment and survival outcomes between patients with T1a and T1b glottic cancer.

METHODS

Patients within the SEER Research Plus, 18 Registries dataset who were diagnosed with Stage I T1a or T1b cancer of the glottis between 2004 and 2015 were included in this study. Data prior to 2004 could not be included, as the SEER database did not distinguish between T1a and T1b glottic cancer until that year.

RESULTS

The 5-year disease-specific survival for T1a patients was significantly better than that of patients diagnosed with T1b glottic cancer. Age and year of diagnosis were also independent factors that impacted mortality. More patients who were diagnosed with T1b glottic cancer underwent external beam radiation than those diagnosed with T1a glottic cancer.

CONCLUSION

Our data shows that there are several independent factors effecting mortality including T classification, age at time of diagnosis, and year of diagnosis. T1a glottic cancers also show a significantly better prognosis compared with T1b. T1b glottic cancers are much more likely to be treated with primary radiotherapy compared with surgery.

LEVEL OF EVIDENCE

4 Laryngoscope, 2022.

Subglottic Mucosal Flap: Endoscopic Single-Stage Reconstruction for Anterior Glottic Stenosis

OBJECTIVES/HYPOTHESIS

Anterior glottic stenosis (AGS) results from surgical intervention, carcinoma, papillomatosis, congenital, or idiopathic causes. It may be present as elastic web or fibrotic scar. It impairs vocal function and glottic airway. Reconstructive options include resection and placement of a keel or glottic web-based mucosal flaps to prevent restenosis. These methods may not be sufficient for reconstructing a thick anterior scar and may require multiple interventions. The aim of the study was to describe the anterior subglottic mucosal flap (ASGMF), a one-stage, keel-free technique for AGS repair.

STUDY DESIGN

A retrospective cohort.

METHODS

Patients with AGS were operated using the ASGMF between 2017 and 2020. The stenotic segment was excised, and then an ASGMF was developed. A unilateral oblique incision was performed to allow rotation and advancement of the flap toward the contralateral vocal fold. The flap was sutured to the mucosal edge of the vocal fold to create mucosal continuity and prevent restenosis. Vocal fold length ratio (VFLR), which is between the free part and the total vocal fold length, as well as stroboscopic measures, were calculated before and after surgery.

RESULTS

Twelve patients were enrolled. Etiologies were iatrogenic, dysplasia, papillomatosis, carcinoma, and congenital. Average VFLR improved from 0.33 to 0.87 (P-value < .0001). Median amplitude and mucosal wave propagation improved from 12.3% and 9.5% to 28.6% and 22.7%, respectively (P-values = .0278, .0385). Phase symmetry improved from 24.5% to 60.9% (P-value = .0413). No complications were encountered.

CONCLUSIONS

ASGMF for AGS is an effective surgical procedure, allowing for one stage, keel-free reconstruction of the anterior commissure. ASGMF can significantly elongate the free portion of the vocal folds and improve vibratory function.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

[Feasibility and efficacy of a thyroid cartilage window technique for transoral CO₂ laser resection of early glottic cancer involving the anterior commissure]

Objective:To evaluate the feasibility and efficacy of a thyroid cartilage window resection（TCWR） technique for transoral CO₂ laser resection of early glottic cancer with involvement of the anterior commissure. Methods:Twenty-one patient who underwent a TCWR technique for transoral CO₂ laser resection early glottic carcinoma involving the anterior commissure, were retrospectively analyzed. Indices including margin status, perioperative comorbidities, voice outcomes, local control rate and recurrence free survival, were assessed. Results:All 21 patients underwent a TCWR technique for resection, the organ preservation rate and negative margin achieved 100%. The local control rate achieved 100%. For two patients with subglottic involvement（9.5%）, regional recurrence with confirmation of a positive pre-laryngeal lymph node was subsequently observed; and the 5 years recurrence free survival was 90.5%. Postoperative granulomas were detected in all 21 patients in 4 weeks postoperatively, 13 of which（61.9%） spontaneously disappeared; whereas the remaining 8 patients（38.1%） demonstrated consistent presence of granuloma more than 12 weeks and underwent an additional surgical extirpation under topical anesthesia. Despite the laryngeal web developed in all 21 patients, no dyspnea and laryngeal stenosis occurred at the time of analysis. By comparison with preoperative baseline, postoperative self-assessment voice demonstrated a significant improvement（P=0.01）, while objective voice indices were not significantly altered（P>0.05）. Conclusion:TCWR technique is a valuable means for transoral CO₂ laser resection of early glottic laryngeal cancer involving the anterior commissure, with favorable voice quality and seemingly low comorbidities, which can effectively improve the safety of the anterior resection margin.

Revisiting brain rewiring and plasticity in children born without corpus callosum

The corpus callosum is the largest white matter pathway connecting homologous structures of the two cerebral hemispheres. Remarkably, children and adults with developmental absence of the corpus callosum (callosal dysgenesis, CD) show typical interhemispheric integration, which is classically impaired in adult split-brain patients, for whom the corpus callosum is surgically severed. Tovar-Moll and colleagues (2014) proposed alternative neural pathways involved in the preservation of interhemispheric transfer. In a sample of six adults with CD, they revealed two homotopic bundles crossing the midline via the anterior and posterior commissures and connecting parietal cortices, and the microstructural properties of these aberrant bundles were associated with functional connectivity of these regions. The aberrant bundles were specific to CD and not visualised in healthy brains. We extended this study in a developmental cohort of 20 children with CD and 29 typically developing controls (TDC). The two anomalous white-matter bundles were visualised using tractography. Associations between structural properties of these bundles and their regional functional connectivity were explored. The proposed atypical bundles were observed in 30% of our CD cohort crossing via the anterior commissure, and in 30% crossing via the posterior commissure (also observed in 6.9% of TDC). However, the structural property measures of these bundles were not associated with parietal functional connectivity, bringing into question their role and implication for interhemispheric functional connectivity in CD. It is possible that very early disruption of embryological callosal development enhances neuroplasticity and facilitates the formation of these proposed alternative neural pathways, but further evidence is needed.

Simple Endoscopic Application of Laryngeal Keel Stent

This study describes a simple extraendolaryngeal technique to apply laryngeal keel in dealing with anterior commissure web/fibrosis. Standard extraendolaryngeal punctures were applied via 20-gauge needles, 30° from the skin surface, in midline through the cricothyroid and thyrohyoid membranes. These needles were used as a conduit for the passage of 2/0 Prolene threads, which were retrieved through the laryngoscope by crocodile forceps. Both laryngoscopic ends of the Prolene threads were passed through a fabricated silastic sheet (keel stent) via a 22-gauge free needle, and these ends were tied to have a secure internal knot. Steady traction was applied on the other 2 external threads until there was appropriate application of this keel stent within the vicinity of anterior commissure. Finally, these external ends were tied to have a secure external knot. A keel stent could be applied without the need for special instrumentation and with reasonable outcomes (proper healing of anterior commissure, satisfied voice outcome, and patent airway).

Redundancy circuits of the commissural pathways in human and rhesus macaque brains

It has been hypothesized that the human brain has less redundancy than animals, but the structural evidence has not been identified to confirm this claim. Here, we report three redundancy circuits of the commissural pathways in primate brains, namely the orbitofrontal, temporal, and occipital redundancy circuits of the anterior commissure and corpus callosum. Each redundancy circuit has two distinctly separated routes connecting a common pair of cortical regions. We mapped their trajectories in human and rhesus macaque brains using individual and population‐averaged tractography. The dissection results confirmed the existence of these redundancy circuits connecting the orbitofrontal lobe, amygdala, and visual cortex. The volume analysis showed a significant reduction in the orbitofrontal and occipital redundancy circuits of the human brain, whereas the temporal redundancy circuit had a substantial organizational difference between the human and rhesus macaque. Our results support the hypothesis that the human brain has less redundancy in the commissural pathways than that of the rhesus macaque brain. Further studies are needed to explore its neuropathological implications.

Application of a thyroid cartilage window technique for transoral resection of early glottic cancer involving the anterior commissure

BACKGROUND

Management of early stage glottic carcinoma involving the anterior commissure is challenging.

AIMS/OBJECTIVES

This study aimed to evaluate the efficacy of a thyroid cartilage window (TCW) technique for transoral laser resection of early glottic cancer with involvement of the anterior commissure.

MATERIAL AND METHODS

Twenty-one patient who underwent a TCW technique for transoral resection early glottic carcinoma involving the anterior commissure, were retrospectively analyzed. The technical nuances, organ preservation rate and voice outcomes, local and regional recurrence, and perioperative comorbidities, were assessed.

RESULTS

All 21 patients underwent a TCW technique for resection, both the organ preservation rate and negative margin achieved 100%. The local control rate achieved 100%, and the 5 years recurrence free survival was 90.5%. For two patients with subglottic involvement (9.5%), regional recurrence with confirmation of a positive pre-laryngeal lymph node was observed. Postoperative granuloma was detected in all 21 patients, 13 of whom spontaneously disappeared (61.9%); whereas the remaining 8 patients (38.1%) demonstrated a consistent presence of granuloma more than 12 weeks, and they accepted surgical extirpation of granuloma under surface anesthesia. The laryngeal web developed in all 21 patients, while no dyspnea and local recurrence were present. By comparison with preoperative baseline, postoperative self-assessment voice demonstrated a significant improvement (p = .01), while objective voice indices were not significantly altered (p > .05).

CONCLUSIONS AND SIGNIFICANCE

TCW technique is a valuable means for transoral resection of early glottic laryngeal cancer involving the anterior commissure, with acceptable voice quality and seemingly low comorbidities.

Neural Stem Cells Direct Axon Guidance via Their Radial Fiber Scaffold

Neural stem cells directly or indirectly generate all neurons and macroglial cells and guide migrating neurons by using a palisade-like scaffold made of their radial fibers. Here, we describe an unexpected role for the radial fiber scaffold in directing corticospinal and other axons at the junction between the striatum and globus pallidus. The maintenance of this scaffold, and consequently axon pathfinding, is dependent on the expression of an atypical RHO-GTPase, RND3/RHOE, together with its binding partner ARHGAP35/P190A, a RHO GTPase-activating protein, in the radial glia-like neural stem cells within the ventricular zone of the medial ganglionic eminence. This role is independent of RND3 and ARHGAP35 expression in corticospinal neurons, where they regulate dendritic spine formation, axon elongation, and pontine midline crossing in a FEZF2-dependent manner. The prevalence of neural stem cell scaffolds and their expression of RND3 and ARHGAP35 suggests that these observations might be broadly relevant for axon guidance and neural circuit formation.

T1b Glottic Tumor and Anterior Commissure Involvement: Is the Transoral CO2 Laser Microsurgery a Safe Option?

OBJECTIVES

Transoral CO₂ laser therapy represents the treatment of choice for early-stage laryngeal tumors. The anterior commissure involvement (ACI) is related to a worse local control and a lower rates of organ preservation. The objective of this study is to analyze the differences in survival, local control, and organ preservation in T1b glottic patients according to the presence of ACI.

METHODS

Observational prospective study in pT1b treated with transoral CO₂ laser between 2009 and 2014.

RESULTS

Forty patients (37 male and 3 female) with a mean age of 66.43 ± 8.16 years were recruited. Anterior commissure involvement was present in 70% of the patients. The 5-year specific cause survival was 91.66%, with 32.50% of local recurrences. Laryngeal preservation was 80%, being lower in the group with local recurrence (P < .000). The involvement of the anterior commissure does not influence the organ preservation (P = .548), the appearance of local recurrences (P = .391), or the survival (P = .33).

CONCLUSIONS

Transoral CO₂ laser therapy is an effective and reproducible treatment for early-stage laryngeal tumors. The results obtained are similar to previous studies, although they present discrepancies in relation to the role of the ACI. Prospective randomized trials are required focusing also on the patients' quality of life and functional outcome in order to clarify the role of the ACI and the need to implement changes in its evaluation, staging, and evolution.

A Dissectional Study of the Level of Anterior Commissure of the Larynx

PURPOSE

Precise knowledge of the level of the vocal fold as projected on the external thyroid cartilage is of critical importance for the performance of many surgical approaches. This study aims to identify the level of the anterior commissure, as well as the lengths of the vocal muscle and arytenoid cartilage in Turkish population.

MATERIALS AND METHOD

Specimens were collected after autopsy from the Council of Forensic Medicine. One hundred human larynges (52 men, 48 women; age range: 25-80 years) were dissected under a stereomicroscope. Projection of the vocal fold was analyzed in relation to the superior thyroid (A) and the inferior border of the thyroid cartilage (B). Then, the larynx was dissected parallel to the level of the vocal fold to measure the length of the vocal muscle (C) and the length of the interarytenoid space (D).

RESULTS

The mean value of the "a" was 9.15 ± 1.99 mm in male and 9.38 ± 3.43 mm in female. Mean value of the "b" was 10.54 ± 1.73 mm and 8.88 ± 1.81 mm in male and female, respectively. The mean value of the parameter corresponding the length of vocal muscle which was "c" was found 15.00 ± 3.18 mm in male and 12.88 ± 4.12 mm in female. The mean value of the interarytenoid space "d" was 8.31 ± 1.76 mm in male and 8.13 ± 1.90 mm in female. Comparing between genders, no statistical differences were observed in parameters of a, c, d, a + b, a + b/2 (P > .05). However, the difference with female and male for the parameters of b and c + d was statistically significant (P < .05).

CONCLUSION

Our results indicate that the anterior commissure projects slightly above the midline height for male and at the level to slightly below in female subjects in Turkish population.

Laser Microsurgery Versus Radiotherapy Versus Open Partial Laryngectomy for T2 Laryngeal Carcinoma: A Systematic Review of Oncological Outcomes

INTRODUCTION

The aim of the current systematic review is to update the pooled survival outcome of patients with T2 glottic carcinoma treated with either laser surgery (CO₂ transoral laser microsurgery [CO₂ TOLMS]), radiotherapy (RT), or open partial laryngectomy (OPL).

METHODS

A systematic search was performed using the MEDLINE database, Scopus, and Google scholar. The inclusion criteria were studies of patients with T2N0 glottic tumor, treated with either primary CO₂ TOLMS, definitive curative RT, or primary OPL, and with reported oncological outcome at 5 years calculated with a Kaplan-Meier or Cox regression method.

RESULTS

The results of the current review show that local control (LC) is higher with OPL 94.4%, while there are no differences in LC at 5-year posttreatment for patients treated with RT, compared to those treated with CO₂ TOLMS (respectively, 75.6% and 75.4%). Primary treatment with OPL and CO₂ TOLMS results in higher laryngeal preservation than primary treatment with RT (respectively 95.8%, 86.9%, and 82.4%).

CONCLUSION

First-line treatment with OPL and CO₂ TOLMS should be encouraged in selected T2 patients, because it results in higher laryngeal preservation and similar LC compared to primary treatment with RT. The involvement of the anterior commissure in the craniocaudal plane and T2b impaired vocal cord mobility have a poorer prognosis and LC compared to patients with T2a tumors for both CO₂ TOLMS and RT.

Experimental Demyelination of the Lateral Olfactory Tract and Anterior Commissure

Demyelination significantly affects brain function. Several experimental methods, each inducing varying levels of myelin and neuronal damage, have been developed to understand the process of myelin loss and to find new therapies to promote remyelination. The present work investigates the effect of one such method, lysolecithin administration, on the white matter tracts in the olfactory system. The olfactory forebrain contains two distinct tracts with differing developmental histories, axonal composition, and function: the lateral olfactory tract (LOT), which carries ipsilateral olfactory information from the olfactory bulb to olfactory cortex, and the anterior commissure (AC), which interconnects olfactory regions across hemispheres. The effects of lysolecithin injections were assessed in two ways: (1) the expression of myelin basic protein, a component of compacted myelin sheaths, was quantified using immunohistochemistry and (2) electron microscopy was used to obtain measurements of myelin thickness of individual axons as well as qualitative descriptions of the extent of damage to myelin and surrounding tissue. Data were collected at 7, 14, 21, and 30 days post-injection (dpi). While both the LOT and AC exhibited significant demyelination at 7 dpi and had returned to control levels by 30 dpi, the process differed between the two tracts. Remyelination occurred more rapidly in the LOT: substantial recovery was observed in the LOT by 14 dpi, but not in the AC until 21 dpi. The findings indicate that (a) the LOT and AC are indeed suitable tracts for studying lysolecithin-induced de- and remyelination and (b) experimental demyelination proceeds differently between the two tracts.

Anterior Commissure Regulates Neuronal Activity of Amygdalae and Influences Locomotor Activity, Social Interaction and Fear Memory in Mice

The two hemispheres of the vertebrate brain are connected through several commissures. Although the anterior commissure (AC) is the most conserved white matter structure in the brains of different vertebrates, its complete physiological functionality remains elusive. Since the AC is involved in the connection between two amygdalae and because amygdalae are critical for emotional behaviors and social interaction, we assessed amygdalar activity and function to investigate the physiological role of the AC. We first performed ex vivo electrophysiological recording on mouse brains to demonstrate that the AC delivers a positive signal to facilitate synaptic responses and to recruit basolateral amygdalar neurons via glutamatergic synapses. Transection was then undertaken to investigate the role of the AC in vivo. Results from in vivo optogenetic stimulation suggest that AC transection impairs mutual activation between two basolateral amygdalae. Behavioral analyses were then used to assess if AC surgical lesioning results in hyperactivity, anxiety, social reduction or learning/memory impairment, which are behavioral features associated with neuropsychiatric disorders, such as autism spectrum disorders. We found that AC transection results in higher locomotor activity, aberrant social interaction and reduced associative memory, but not anxiety. Moreover, systemic administration of D-cycloserine, a coagonist of N-methyl-D-aspartate receptor, ameliorated auditory fear memory in AC-transected mice, reinforcing our evidence that the AC potentiates the activity of basolateral amygdalae. Our study suggests that the AC regulates basolateral amygdalar activity and influences neuropsychiatry-related behaviors in mice.

A new brain CT reference line: the lower eyelid to the inner occipital base line closely parallels the Talairach-Tournoux line

Background

There is no standardized brain computed tomography (CT) reference line that can be determined on both scout and reformatted sagittal CT images. Here, a tangential line from the anterior edge of the lower eyelid to the inner table of the occipital base (LEL/O line) appears nearly parallel to the Talairach–Tournoux (T/T) line, which shows a consistent intracranial anatomical relationship among subjects, and acts as a standard reference line for magnetic resonance (MR) imaging.

Purpose

To quantitatively validate the LEL/O line as a new standard brain CT reference line.

Material and Methods

We measured: angle 1 = the LEL/O line on scout images from the LEL/O line on parasagittal CT images (n=93); and angle 2 = the LEL/O line on scout images from the T/T line on high resolution midsagittal MR images (n=97). Angles in a clockwise direction were defined as positive and were expressed as mean±SD with the 95% confidence interval (CI) of the SD. Angle 2 was measured independently by two observers and intraclass correlation coefficients (ICCs) were calculated.

Results

Angle 1 was –0.4°±1.2° (95% CI of SD 1.1°–1.5°); angle 2 was –0.4°±2.0° (95% CI of SD, 1.8°–2.4°). The ICC in the angle 2 measurement was 0.780 (P<0.001), which indicated high inter-observer reliability.

Conclusion

The LEL/O lines on scout and parasagittal CT images show practically the same gradient, and these LEL/O lines are almost parallel to the T/T line. Use of the LEL/O line either for direct scanning or reformation can minimize intra- and inter-subject variations on CT images and mismatch between CT and MR images.

Surgical Management of Anterior Glottic Webs

Congenital webs are rare and represent <5% of all congenital laryngeal anomalies. They are usually a partial laryngeal atresia rather than a true web, and present as a thick and fibrotic web with subglottic extension and associated subglottic stenosis. All patients with a congenital anterior glottic web should be evaluated for chromosome 22q11.2 deletion syndrome. Management strategies are mainly based on the severity of airway obstruction and the anatomical extension of the webs. Simple division of the web endoscopically may be adequate for rare thin webs, however, an open approach is usually warranted for thick glottic webs regardless of Cohen grades. Open repair can be either with keel placement or reconstruction of the anterior commissure.

The prognostic value of anterior commissure involvement in T1 glottic cancer: A systematic review and meta-analysis

OBJECTIVE

The anterior commissure is considered a laryngeal subsite, but it is not taken into account in the current T-staging system. The impact of anterior commissure involvement (ACI) on the oncologic outcomes of T1 glottic tumors has not been well defined and remains controversial. The aim of this study was to assess the influence of ACI in the prognosis of T1 glottic tumors.

METHODS

A systematic review and meta-analysis of observational studies was performed by including studies published up to July 2019. Studies were selected if they had investigated the local control rate (LCR) at 5 years of clinical stage I (T1 and N0) glottic squamous cell carcinoma with and without ACI. The difference in LCR at 5 years between T1 glottic tumors without and with ACI was evaluated.

RESULTS

The meta-analysis showed that the difference in LCR at 5 years between T1 glottic tumors without and with ACI is 12% (95% confidence interval: 8%-16%, p < 0,0001, I² = 34.81%).

CONCLUSIONS

Our study pointed out that the anterior commissure involvement is a negative prognostic factor in LCR at 5 years for T1 glottic tumors. Our results suggest the need to consider ACI in the T staging of glottic tumors. Laryngoscope, 130:1932-1940, 2020.

Ablation of CNTN2+ Pyramidal Neurons During Development Results in Defects in Neocortical Size and Axonal Tract Formation

Corticothalamic axons express Contactin-2 (CNTN2/TAG-1), a neuronal recognition molecule of the immunoglobulin superfamily involved in neurogenesis, neurite outgrowth, and fasciculation. TAG-1, which is expressed transiently by cortical pyramidal neurons during embryonic development, has been shown to be fundamental for axonal recognition, cellular migration, and neuronal proliferation in the developing cortex. Although Tag-1^−/− mice do not exhibit any obvious defects in the corticofugal system, the role of TAG-1+ neurons during the development of the cortex remains elusive. We have generated a mouse model expressing EGFP under the Tag-1 promoter and encompassing the coding sequence of Diptheria Toxin subunit A (DTA) under quiescence with no effect on the expression of endogenous Tag-1. We show that while the line recapitulates the expression pattern of the molecule, it highlights an extended expression in the forebrain, including multiple axonal tracts and neuronal populations, both spatially and temporally. Crossing these mice to the Emx1-Cre strain, we ablated the vast majority of TAG-1+ cortical neurons. Among the observed defects were a significantly smaller cortex, a reduction of corticothalamic axons as well as callosal and commissural defects. Such defects are common in neurodevelopmental disorders, thus this mouse could serve as a useful model to study physiological and pathophysiological cortical development.

Interhemispheric Connectivity Potentiates the Basolateral Amygdalae and Regulates Social Interaction and Memory

Impaired interhemispheric connectivity is commonly found in various psychiatric disorders, although how interhemispheric connectivity regulates brain function remains elusive. Here, we use the mouse amygdala, a brain region that is critical for social interaction and fear memory, as a model to demonstrate that contralateral connectivity intensifies the synaptic response of basolateral amygdalae (BLA) and regulates amygdala-dependent behaviors. Retrograde tracing and c-FOS expression indicate that contralateral afferents widely innervate BLA non-randomly and that some BLA neurons innervate both contralateral BLA and the ipsilateral central amygdala (CeA). Our optogenetic and electrophysiological studies further suggest that contralateral BLA input results in the synaptic facilitation of BLA neurons, thereby intensifying the responses to cortical and thalamic stimulations. Finally, pharmacological inhibition and chemogenetic disconnection demonstrate that BLA contralateral facilitation is required for social interaction and memory. Our study suggests that interhemispheric connectivity potentiates the synaptic dynamics of BLA neurons and is critical for the full activation and functionality of amygdalae.

Survival and Prognostic Factors for Outcome after Radiotherapy for T2 Glottic Carcinoma

Background: Local recurrence after radiotherapy for T2 glottic carcinoma remains an issue and identifying patients at risk for relapse is, therefore, important. This study aimed to assess the oncological outcomes and prognostic factors in a consecutive series of patients treated with radiotherapy for T2N0 glottic carcinoma. Methods: Patients with T2N0 glottic carcinoma treated with radiotherapy were included in this retrospective study. Five- and ten-year local control (LC), overall survival (OS), disease-specific survival (DSS), and laryngeal preservation (LP) rates were calculated with the Kaplan–Meier method. The impact of prognostic variables was evaluated with the log-rank test. Results: Ninety-four patients were included for analysis. LC, OS, DSS, and LP rates were 70.5, 63.7, 86.0, and 74.7%, respectively at five years and 65.8, 41.0, 75.6, and 72.4% at 10 years. In total, 46 scans were included in the analyses. Vertical involvement of the anterior commissure on imaging showed a significant impact on LC. Conclusions: In accordance with previously described surgical risk factors, we identified vertical involvement of the anterior commissure on imaging as a prognostic factor for radiation failure.

Involvement of the Anterior Commissure in Early Glottic Cancer (Tis-T2): A Review of the Literature

Background: The impact of the anterior commissure (AC) involvement on prognosis in laryngeal cancer remains a topic of discussion with inconsistent results in the literature. This review examines AC involvement as a prognostic factor in patients with early glottic cancer (Tis-T2) treated with radiotherapy or transoral laser microsurgery (TLM). Methods: A systematic literature search was performed. Due to the heterogeneity of the data, no meta-analysis was implemented. Weighted averages were calculated if the appropriate data were extractable. Results: Thirty-four studies on radiotherapy and 23 on TLM fit the inclusion criteria. The majority of studies for both radiotherapy (67.7%) and TLM (75.0%) did not report a significant impact on oncological outcomes. Weighted averages were slightly lower in patients with AC involvement. The two studies that applied a more detailed classification showed a significant impact on the amount of AC involvement. Conclusions: Binary variables (yes/no) for AC involvement lead to inconsistent results. Studies that use more detailed classifications of the AC show that there is a significant impact on the outcome. To further elucidate the role of the AC, detailed stratification of tumors involving the AC need to be investigated in further studies for both treatment modalities.

Oncological outcomes of CO2 laser cordectomies for glottic squamous cell carcinoma with respect to anterior commissure involvement and margin status

BACKGROUND AND OBJECTIVES

Controversial prognostic factors of primary CO₂ laser cordectomy are anterior commissure involvement (ACI) and status of margin.

STUDY DESIGN/MATERIALS AND METHODS

Retrospective analysis of oncological outcomes in 102 patients with early glottic cancer undergoing laser cordectomy between 2013 and 2015.

RESULTS

The T stages distribution included: 72.6% T1a, 14.7% T1b, and 12.7% T2. The ACI was diagnosed in 26 patients. The primary cordectomy was radical in 72 patients. The 2- and 5-year disease free survival (DFS) for all patients were, respectively, 83.3% and 77.3%.The 2-year DFS rates for T1a, T1b, T2 were, respectively, 91.7%, 66.7%, and 53.9% and the differences were statistically significant (P < 0.001). The 2-year DFS rates according to the ACI and free anterior commissure tumors were, respectively, 65.4% and 89.2%, and the ACI indicated worse prognosis (P = 0.057). The 2-year DFS rates according to margins status were higher for patients with close or positive margins, who had second resection (88.9%) compared with those of negative margins (80.9%) (P = 0.340). Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Cortical and Commissural Defects Upon HCF-1 Loss in Nkx2.1-Derived Embryonic Neurons and Glia

Formation of the cerebral cortex and commissures involves a complex developmental process defined by multiple molecular mechanisms governing proliferation of neuronal and glial precursors, neuronal and glial migration, and patterning events. Failure in any of these processes can lead to malformations. Here, we study the role of HCF‐1 in these processes. HCF‐1 is a conserved metazoan transcriptional co‐regulator long implicated in cell proliferation and more recently in human metabolic disorders and mental retardation. Loss of HCF‐1 in a subset of ventral telencephalic Nkx2.1‐positive progenitors leads to reduced numbers of GABAergic interneurons and glia, owing not to decreased proliferation but rather to increased apoptosis before cell migration. The loss of these cells leads to development of severe commissural and cortical defects in early postnatal mouse brains. These defects include mild and severe structural defects of the corpus callosum and anterior commissure, respectively, and increased folding of the cortex resembling polymicrogyria. Hence, in addition to its well‐established role in cell proliferation, HCF‐1 is important for organ development, here the brain.

[Advances in the treatment of anterior commissure combined with early glottic carcinoma]

Summary Early glottic laryngeal cancer usually refers to the Tis-T2 lesion without cervical lymph node and distant metastases. Radiotherapy of early glottic laryngeal cancer, CO₂ laser microsurgery, open surgery, plasma radiofrequency ablation, photodynamic therapy, biological targeting therapy have achieved good therapeutic effect. However, due to the special nature of its anatomy, it is controversial about the treatment of early glottic laryngeal cancer which involves the anterior commissure. In this article, we reviewed the conventional treatment of radiation therapy, CO₂ laser microsurgery, open surgery, plasma radiofrequency ablation.

A pan-mammalian map of interhemispheric brain connections predates the evolution of the corpus callosum

The brain of mammals differs from that of all other vertebrates, in having a six-layered neocortex that is extensively interconnected within and between hemispheres. Interhemispheric connections are conveyed through the anterior commissure in egg-laying monotremes and marsupials, whereas eutherians evolved a separate commissural tract, the corpus callosum. Although the pattern of interhemispheric connectivity via the corpus callosum is broadly shared across eutherian species, it is not known whether this pattern arose as a consequence of callosal evolution or instead corresponds to a more ancient feature of mammalian brain organization. Here we show that, despite cortical axons using an ancestral commissural route, monotremes and marsupials share features of interhemispheric connectivity with eutherians that likely predate the origin of the corpus callosum. Based on ex vivo magnetic resonance imaging and tractography, we found that connections through the anterior commissure in both fat-tailed dunnarts (Marsupialia) and duck-billed platypus (Monotremata) are spatially segregated according to cortical area topography. Moreover, cell-resolution retrograde and anterograde interhemispheric circuit mapping in dunnarts revealed several features shared with callosal circuits of eutherians. These include the layered organization of commissural neurons and terminals, a broad map of connections between similar (homotopic) regions of each hemisphere, and regions connected to different areas (heterotopic), including hyperconnected hubs along the medial and lateral borders of the cortex, such as the cingulate/motor cortex and claustrum/insula. We therefore propose that an interhemispheric connectome originated in early mammalian ancestors, predating the evolution of the corpus callosum. Because these features have been conserved throughout mammalian evolution, they likely represent key aspects of neocortical organization.

[Clinical observation of radiofrequency coblation therapy in early glottis cancer involving the anterior commissure with endoscope]

Objective: To explore clinical effect of CO₂ laser combined with radiofrequency coblation therapy on early glottis carcinoma involving the anterior commissure with endoscope.Method:The clinical data of 10 patients with early glottis cancer involving the anterior commissure who were underwent CO₂ laser and radiofrequency coblation with angled endoscope was retrospective analyzed.All patients receieved CT scan with contrast to rule out the cases with thyroid cartilage plate involvement.Result:The surgeries were performed successfully on all of the 10 patients. The pathology of the 10 patients were all squamous cell carcinoma. Surgical margins showed no residual tumor cell. There was no recurrence or metastasis with a follow-up of 6 to 48 months.Conclusion:It was an effective treatment for the CO₂ laser and radiofrequency coblation therapy in glottis cancer involving the anterior commissure with endoscope.

Prevention of laryngeal webs through endoscopic keel placement for bilateral vocal cord lesions

Transoral microresection for treatment of vocal cord lesions involving the anterior commissure may result in anterior glottic webs. In this study, we retrospectively reviewed 54 patients who underwent microsurgery for bilateral lesions involving the anterior commissure and categorized them into two groups. The keel placement and control groups received endoscopic keel placement and mitomycin C, respectively. During the follow-up of at least 1 year, the laryngeal web formation rate significantly decreased in the keel placement group compared with that in the control group (18.6% versus 54.5%, P < 0.05). Furthermore, the voice handicap index-10 scores for patients without web formation decreased in both the keel placement and control groups (P < 0.0001 and P < 0.001, respectively). A pseudomembrane covering the vocal cords was detected in 16.3% (7 of 43) cases after keel removal. A total of 100% (7 of 7) of these cases and 2.8% (1 of 36) of the other cases formed laryngeal webs (P < 0.0001). Endoscopic keel placement could be an effective method for preventing anterior glottic webs after surgery for bilateral vocal cord diseases involving the anterior commissure. The pseudomembrane observed at the time of keel removal may imply a high risk of web formation.

Spontaneous Rapid Odor Source Localization Behavior Requires Interhemispheric Communication

Navigation, finding food sources, and avoiding danger critically depend on the identification and spatial localization of airborne chemicals. When monitoring the olfactory environment, rodents spontaneously engage in active olfactory sampling behavior, also referred to as exploratory sniffing [1]. Exploratory sniffing is characterized by stereotypical high-frequency respiration, which is also reliably evoked by novel odorant stimuli [2, 3]. To study novelty-induced exploratory sniffing, we developed a novel, non-contact method for measuring respiration by infrared (IR) thermography in a behavioral paradigm in which novel and familiar stimuli are presented to head-restrained mice. We validated the method by simultaneously performing nasal pressure measurements, a commonly used invasive approach [2, 4], and confirmed highly reliable detection of inhalation onsets. We further discovered that mice actively orient their nostrils toward novel, previously unexperienced, smells. In line with the remarkable speed of olfactory processing reported previously [3, 5, 6], we find that mice initiate their response already within the first sniff after odor onset. Moreover, transecting the anterior commissure (AC) disrupted orienting, indicating that the orienting response requires interhemispheric transfer of information. This suggests that mice compare odorant information obtained from the two bilaterally symmetric nostrils to locate the source of the novel odorant. We further demonstrate that asymmetric activation of the anterior olfactory nucleus (AON) is both necessary and sufficient for eliciting orienting responses. These findings support the view that the AON plays an important role in the internostril difference comparison underlying rapid odor source localization.

Compound Heterozygous Variants in ROBO1 Cause a Neurodevelopmental Disorder With Absence of Transverse Pontine Fibers and Thinning of the Anterior Commissure and Corpus Callosum

BACKGROUND

Axonal guidance disorders are characterized by white matter tracts with an anomalous course, failure to cross the midline, or presence of anomalous white matter tracts. Diffusion tensor imaging (DTI) is a suitable noninvasive, in vivo neuroimaging tool to study axonal guidance disorders. We describe a novel disorder in a boy with compound heterozygous variants in the ROBO1 gene.

PATIENT DESCRIPTION

The child was referred at age 13 months because of developmental delay. At age nine years, he had severe intellectual disability and hyperactivity. He was nonverbal and wheelchair dependent because of spastic diplegia and ataxia. Brain magnetic resonance imaging with DTI revealed marked pontine hypoplasia, thinning of the anterior commissure and corpus callosum, and absence of the transverse pontine fibers. In addition, at the level of the pons the corticospinal tracts and medial lemnisci were not clearly separated from each other. Whole exome sequencing revealed compound heterozygous variants in the ROBO1 gene.

CONCLUSION

This child's neuroimaging phenotype (absence of the transverse pontine fibers and thinning of the anterior commissure and corpus callosum as shown by DTI) is suggestive of an axonal guidance disorder and supports a pathogenic role of the compound heterozygous variants in the ROBO1 gene.

Interhemispheric Connections between the Primary Visual Cortical Areas via the Anterior Commissure in Human Callosal Agenesis

Aim: In humans, images in the median plane of the head either fall on both nasal hemi-retinas or on both temporal hemi-retinas. Interhemispheric connections allow cortical cells to have receptive fields on opposite sides. The major interhemispheric connection, the corpus callosum, is implicated in central stereopsis and disparity detection in front of the fixation plane. Yet individuals with agenesis of the corpus callosum may show normal stereopsis and disparity vergence. We set out to study a possible interhemispheric connection between primary visual cortical areas via the anterior commissure to explain this inconsistency because of the major role of these cortical areas in elaborating 3D visual perception.

Methods: MRI, DTI and tractography of the brain of a 53-year old man with complete callosal agenesis and normal binocular single vision was undertaken. Tractography seed points were placed in both the right and the left V1 and V2. Nine individuals with both an intact corpus callosum and normal binocularity served as controls.

Results: Interhemispheric tracts through the anterior commissure linking both V1 and V2 visual cortical areas bilaterally were indeed shown in the subject with callosal agenesis. All other individuals showed interhemispheric visual connections through the corpus callosum only.

Conclusion: Callosal agenesis may result in anomalous interhemispheric connections of the primary visual areas via the anterior commissure. It is proposed here that these connections form as alternative to the normal callosal pathway and may participate in binocularity.

Complete prefrontal lobe isolation surgery for recurrent epilepsy: A case report

Epileptogenic focus resection is less effective for the treatment of frontal lobe epilepsy compared with temporal lobe epilepsy. However, there is currently a lack of effective therapeutic options for patients with frontal lobe epilepsy who are unsuitable for epileptogenic focus resection (such patients with epileptogenic foci in one frontal lobe in which the precise epileptic foci cannot be determined), or who experience recurrent epilepsy following epileptogenic focus resection. The present study reports a patient with frontal lobe epilepsy who underwent successful frontal lobe isolation surgery following a previous unsuccessful epileptogenic focus resection surgery. To ensure complete isolation of the prefrontal lobe, the surgery included division of the anterior commissure and the anterior part of the corpus callosum. The patient was followed-up for 16 months. Although the follow-up electroencephalogram presented a number of sharp waves on the affected side, the patient did not experience any seizures. The results suggest that prefrontal lobe isolation is an effective method of treating frontal lobe epilepsy, as division of the anterior commissure and the anterior part of the corpus callosum ensures disconnection of the prefrontal lobe from other regions of the brain.

The Distribution of Ki-67 and Doublecortin Immunopositive Cells in the Brains of Three Microchiropteran Species, Hipposideros fuliginosus, Triaenops persicus, and Asellia tridens

This study uses Ki-67 and doublecortin (DCX) immunohistochemistry to delineate potential neurogenic zones, migratory pathways, and terminal fields associated with adult neurogenesis in the brains of three microchiropterans. As with most mammals studied to date, the canonical subgranular and subventricular neurogenic zones were observed. Distinct labeling of newly born cells and immature neurons within the dentate gyrus of the hippocampus was observed in all species. A distinct rostral migratory stream (RMS) that appears to split around the medial aspect of the caudate nucleus was observed. These two rostral stream divisions appear to merge at the rostroventral corner of the caudate nucleus to turn and enter the olfactory bulb, where a large terminal field of immature neurons was observed. DCX immunolabeled neurons were observed mostly in the rostral neocortex, but a potential migratory stream to the neocortex was not identified. A broad swathe of newly born cells and immature neurons was found between the caudoventral division of the RMS and the piriform cortex. In addition, occasional immature neurons were observed in the amygdala and DCX-immunopositive axons were observed in the anterior commissure. While the majority of these features have been found in several mammal species, the large number of DCX immunolabeled cells found between the RMS and the piriform cortex and the presence of DCX immunostained axons in the anterior commissure are features only observed in microchiropterans and insectivores to date. In the diphyletic scenario of chiropteran evolution, these observations align the microchiropterans with the insectivores. Anat Rec, 299:1548-1560, 2016. © 2016 Wiley Periodicals, Inc.

Ten-year Survivors After Contemporary Management of Advanced 'Horseshoe' Anterior Commissure Laryngeal Cancer

BACKGROUND

Combinations of treatment modalities for locally extensive carcinomas of the larynx constitute the standard of care. Advanced 'horseshoe' anterior commissure laryngeal cancer (HACLC) is a disease entity that has not received much attention in the literature. The aims of this study were to evaluate prolonged survival in patients after standard combined therapy for HACLC and to identify clinicopathological factors influential towards an extended outcome.

PATIENTS AND METHODS

Fourteen patients (10-year survivors) with stage III or IV laryngeal cancer involving the anterior commissure and both true vocal cords were treated with total laryngectomy (and postoperative radiotherapy in 11 individuals).

RESULTS

During follow-up, ranging from 123 to 256 months, locoregional recurrent disease and distant metastasis were not observed. Complications after therapy were manageable and few. The long-term survivors were particularly difficult to characterize.

CONCLUSION

The optimal treatment for advanced HACLC has not been clarified; however, in this study, total laryngectomy and the indicated use of postoperative radiotherapy, were successful in achieving long-term disease-free survival. Predictive factors for longevity were not detected in this limited experience.

Transoral robotic surgery for early glottic carcinoma involving anterior commissure: Preliminary reports

BACKGROUND

Transoral robotic surgery (TORS) for early glottic cancer has been reported, but the issue of anterior commissure involvement has seldom been addressed. Therefore, the purpose of this study was to preliminarily report the treatment results of TORS in this disease entity.

METHODS

Eight patients with T1 and T2 glottic carcinoma with anterior commissure involvement were selected to receive TORS. The clinical parameters, including rates of adjuvant radiotherapy (RT), survivals, as well as organ and function preservation, were retrospectively analyzed.

RESULTS

TORS was successfully performed in all patients without temporary tracheostomy. There were no major complications and no patient received adjuvant RT to the larynx after surgery. With a mean follow-up of 40 months, all patients survived with their larynx preserved and no local recurrence, tracheostomy, or tube feeding dependence.

CONCLUSION

TORS is a feasible approach for selected patients with early T classification glottic carcinoma with anterior commissure involvement. The preliminary oncologic and functional outcomes are satisfactory. © 2015 Wiley Periodicals, Inc. Head Neck 38: 913-918, 2016.

Glutathione Deficit Affects the Integrity and Function of the Fimbria/Fornix and Anterior Commissure in Mice: Relevance for Schizophrenia

BACKGROUND

Structural anomalies of white matter are found in various brain regions of patients with schizophrenia and bipolar and other psychiatric disorders, but the causes at the cellular and molecular levels remain unclear. Oxidative stress and redox dysregulation have been proposed to play a role in the pathophysiology of several psychiatric conditions, but their anatomical and functional consequences are poorly understood. The aim of this study was to investigate white matter throughout the brain in a preclinical model of redox dysregulation.

METHODS

In a mouse model with impaired glutathione synthesis (Gclm KO), a state-of-the-art multimodal magnetic resonance protocol at high field (14.1 T) was used to assess longitudinally the white matter structure, prefrontal neurochemical profile, and ventricular volume. Electrophysiological recordings in the abnormal white matter tracts identified by diffusion tensor imaging were performed to characterize the functional consequences of fractional anisotropy alterations.

RESULTS

Structural alterations observed at peri-pubertal age and adulthood in Gclm KO mice were restricted to the anterior commissure and fornix-fimbria. Reduced fractional anisotropy in the anterior commissure (-7.5% ± 1.9, P<.01) and fornix-fimbria (-4.5% ± 1.3, P<.05) were accompanied by reduced conduction velocity in fast-conducting fibers of the posterior limb of the anterior commissure (-14.3% ± 5.1, P<.05) and slow-conducting fibers of the fornix-fimbria (-8.6% ± 2.6, P<.05). Ventricular enlargement was found at peri-puberty (+25% ± 8 P<.05) but not in adult Gclm KO mice.

CONCLUSIONS

Glutathione deficit in Gclm KO mice affects ventricular size and the integrity of the fornix-fimbria and anterior commissure. This suggests that redox dysregulation could contribute during neurodevelopment to the impaired white matter and ventricle enlargement observed in schizophrenia and other psychiatric disorders.

Novel experimental rabbit model of anterior glottic web formation

CONCLUSION

The rabbit model of anterior glottic web (AGW) formation using the laryngofissure technique resulted in reproducible and stable AGW formation that may facilitate research into this area.

OBJECTIVE

To introduce and validate a novel experimental animal model of AGW formation using the rabbit.

METHODS

The inner larynges of eight New Zealand white rabbits were exposed through the laryngofissure technique. The mucosa of the bilateral true vocal fold was stripped off using the bevel of a needle tip. On the basis of the laryngoscopic findings at 8 weeks postoperatively, the extent of AGW was measured, and the success of this procedure was validated. Laryngeal specimens were sampled at 8 weeks for high-speed recording and histological analysis.

RESULTS

In seven (87.5%) rabbits, laryngoscopic examination revealed the formation of a scar band involving the anterior commissure. The mean extent of AGW ratio on the left and right sides was 0.58 ± 0.073 and 0.55 ± 0.075, respectively. The symmetric formation of AGW (p = 0.655, p = 0.128) and stability of the AGW procedure (p = 0.491, left; p = 0.501, right) were statistically validated. On high-speed recording, the vocal mucosal wave was hindered by AGW formation. Histologically, fibro-connective tissue, especially collagen fiber, was observed in the anterior commissure.

EphB1 and EphB2 intracellular domains regulate the formation of the corpus callosum and anterior commissure

The two cortical hemispheres of the mammalian forebrain are interconnected by major white matter tracts, including the corpus callosum (CC) and the posterior branch of the anterior commissure (ACp), that bridge the telencephalic midline. We show here that the intracellular signaling domains of the EphB1 and EphB2 receptors are critical for formation of both the ACp and CC. We observe partial and complete agenesis of the corpus callosum, as well as highly penetrant ACp misprojection phenotypes in truncated EphB1/2 mice that lack intracellular signaling domains. Consistent with the roles for these receptors in formation of the CC and ACp, we detect expression of these receptors in multiple brain regions associated with the formation of these forebrain structures. Taken together, our findings suggest that a combination of forward and reverse EphB1/2 receptor-mediated signaling contribute to ACp and CC axon guidance.

Automatic localization of the anterior commissure, posterior commissure, and midsagittal plane in MRI scans using regression forests

Localizing the anterior and posterior commissures (AC/PC) and the midsagittal plane (MSP) is crucial in stereotactic and functional neurosurgery, human brain mapping, and medical image processing. We present a learning-based method for automatic and efficient localization of these landmarks and the plane using regression forests. Given a point in an image, we first extract a set of multiscale long-range contextual features. We then build random forests models to learn a nonlinear relationship between these features and the probability of the point being a landmark or in the plane. Three-stage coarse-to-fine models are trained for the AC, PC, and MSP separately using downsampled by 4, downsampled by 2, and the original images. Localization is performed hierarchically, starting with a rough estimation that is progressively refined. We evaluate our method using a leave-one-out approach with 100 clinical T1-weighted images and compare it to state-of-the-art methods including an atlas-based approach with six nonrigid registration algorithms and a model-based approach for the AC and PC, and a global symmetry-based approach for the MSP. Our method results in an overall error of 0.55 ±0.30 mm for AC, 0.56 ±0.28 mm for PC, 1.08(°) ±0.66 in the plane's normal direction, and 1.22 ±0.73 voxels in average distance for MSP; it performs significantly better than four registration algorithms and the model-based method for AC and PC, and the global symmetry-based method for MSP. We also evaluate the sensitivity of our method to image quality and parameter values. We show that it is robust to asymmetry, noise, and rotation. Computation time is 25 s.

Perspectives on the neural connectivity of the fornix in the human brain

The fornix is involved in the transfer of information on episodic memory as a part of the Papez circuit. Diffusion tensor imaging enables to estimate the neural connectivity of the fornix. The anterior fornical body has high connectivity with the anterior commissure, and brain areas relevant to cholinergic nuclei (septal forebrain region and brainstem) and memory function (medial temporal lobe). In the normal subjects, by contrast, the posterior fornical body has connectivity with the cerebral cortex and brainstem through the splenium of the corpus callosum. We believe that knowledge of the neural connectivity of the fornix would be helpful in investigation of the neural network associated with memory and recovery mechanisms following injury of the fornix.

Evolution and development of interhemispheric connections in the vertebrate forebrain

Axonal connections between the left and right sides of the brain are crucial for bilateral integration of lateralized sensory, motor, and associative functions. Throughout vertebrate species, forebrain commissures share a conserved developmental plan, a similar position relative to each other within the brain and similar patterns of connectivity. However, major events in the evolution of the vertebrate brain, such as the expansion of the telencephalon in tetrapods and the origin of the six-layered isocortex in mammals, resulted in the emergence and diversification of new commissural routes. These new interhemispheric connections include the pallial commissure, which appeared in the ancestors of tetrapods and connects the left and right sides of the medial pallium (hippocampus in mammals), and the corpus callosum, which is exclusive to eutherian (placental) mammals and connects both isocortical hemispheres. A comparative analysis of commissural systems in vertebrates reveals that the emergence of new commissural routes may have involved co-option of developmental mechanisms and anatomical substrates of preexistent commissural pathways. One of the embryonic regions of interest for studying these processes is the commissural plate, a portion of the early telencephalic midline that provides molecular specification and a cellular scaffold for the development of commissural axons. Further investigations into these embryonic processes in carefully selected species will provide insights not only into the mechanisms driving commissural evolution, but also regarding more general biological problems such as the role of developmental plasticity in evolutionary change.

Genetic evidence that Celsr3 and Celsr2, together with Fzd3, regulate forebrain wiring in a Vangl-independent manner

Celsr3 and Fzd3, members of "core planar cell polarity" (PCP) genes, were shown previously to control forebrain axon guidance and wiring by acting in axons and/or guidepost cells. Here, we show that Celsr2 acts redundantly with Celsr3, and that their combined mutation mimics that of Fzd3. The phenotypes generated upon inactivation of Fzd3 in different forebrain compartments are similar to those in conditional Celsr2-3 mutants, indicating that Fzd3 and Celsr2-3 act in the same population of cells. Inactivation of Celsr2-3 or Fzd3 in thalamus does not affect forebrain wiring, and joint inactivation in cortex and thalamus adds little to cortical inactivation alone in terms of thalamocortical projections. On the other hand, joint inactivation perturbs strongly the formation of the barrel field, which is unaffected upon single cortical or thalamic inactivation, indicating a role for interactions between thalamic axons and cortical neurons in cortical arealization. Unexpectedly, forebrain wiring is normal in mice defective in Vangl1 and Vangl2, showing that, contrary to epithelial PCP, axon guidance can be Vangl independent in some contexts. Our results suggest that Celsr2-3 and Fzd3 regulate axonal navigation in the forebrain by using mechanisms different from classical epithelial PCP, and require interacting partners other than Vangl1-2 that remain to be identified.

Implication of the anterior commissure in the allocation of attention to action

Our recent target article on the allocation of attention to action (herein called the AAA model; Franz, 2012) considered implicated subcortical processes and networks in people with intact corpus callosum (CC) and people without a CC due to commissurotomy or callosotomy. However, a small error in print—namely that the term “commissurotomy” was printed in place of “callosotomy” in some instances—led us to further explore whether any key functional roles have been attributed to the two primary cortical commissures (the anterior and posterior commissures) which remain intact in people with callosotomy, and if so, whether those would be relevant to our current AAA framework. Although existing evidence is sparse, here we consider the hypothesis that the anterior commissure (AC) is a remnant fiber tract which has been largely replaced with evolution of the CC (and we do not herein discuss the posterior commissure further). Indeed, a dearth of studies is available on the AC, calling the need for further research. Herein, we briefly review literature on the AC in humans and then propose a method that might be worthwhile to pursue in future studies.