The External Oblique Intercostal Block: Anatomic Evaluation and Case Series

STUDY OBJECTIVE

We report a modified block technique aimed at obtaining upper midline and lateral abdominal wall analgesia: the external oblique intercostal (EOI) block.

DESIGN

A cadaveric study and retrospective cohort study assessing the potential analgesic effect of the EOI block.

SETTING

Cadaver lab and operating room.

PATIENTS

Two unembalmed cadavers and 22 patients.

INTERVENTIONS

Bilateral ultrasound-guided EOI blocks on cadavers with 29 mL of bupivacaine 0.25% with 1 mL of India ink; single-injection or continuous EOI blocks in patients.

MEASUREMENTS

Dye spread in cadavers and loss of cutaneous sensation in patients.

MAIN RESULTS

In the cadaveric specimens, we identified consistent staining of both lateral and anterior branches of intercostal nerves from T7 to T10. We also found consistent dermatomal sensory blockade of T6-T10 at the anterior axillary line and T6-T9 at the midline in patients receiving the EOI block.

CONCLUSIONS

We demonstrate the potential mechanism of this technique with a cadaveric study that shows consistent staining of both lateral and anterior branches of intercostal nerves T7-T10. Patients who received this block exhibited consistent dermatomal sensory blockade of T6-T10 at the anterior axillary line and T6-T9 at the midline. This block can be used in multiple clinical settings for upper abdominal wall analgesia.

External Approach to Buccal Fat Excision in Facelift: Anatomy and Technique

BACKGROUND

Masculinization of the face is a common finding in facelift patients. It is attributed to deflation and decent of the midface-jowls coupled with skin laxity. Fullness is evident lateral to the jowl in a small percentage due to prominent buccal fat pad (BFP).

OBJECTIVES

The authors sought to examine the anatomy of the BFP, triangulate the prominent BFP with surgical landmarks, and describe an external approach to excise the BFP during facelift surgery.

METHODS

Eighteen cadaveric dissections were performed. Facelift flap was elevated and the prominent buccal extension of the BFP protruding through the superficial-musculo-aponeurotic-system was identified. Measurements were taken from the BFP to surgical landmarks: zygomatic arch, tragus, and gonial angle. The locations of the facial nerve, parotid duct, and vascular pedicle relative to the BFP were calculated.

RESULTS

BFP was 4.1 cm inferior to the zygomatic arch, 7.5 cm anterior the tragus, and 4.5 cm medial the gonial angle. The middle facial artery supplied the BFP on the inferior-lateral quadrant in 61% and inferior-medial quadrant in 39% of specimens . In all specimens, the parotid duct traversed the BFP superiorly, and the buccal branches of the facial nerve traversed the capsule superficially.

CONCLUSIONS

The buccal extension of the BFP can pseudoherniate in the aging face. Excision may improve lower facial contour. Measurements from facial landmarks may help surgeons identify the buccal extension of the BFP intraoperatively. The surgeon must be careful of the vascular pedicle, parotid duct, and the facial nerve. The external approach safely excises buccal fat during facelift dissection while avoiding intraoral incisions and unnecessary contamination.

LEVEL OF EVIDENCE: 4

Cervical erector spinae plane block: a cadaver study

Background

Cervical erector spinae plane (ESP) block has been described to anesthetize the brachial plexus (BP), however, the mechanism of its clinical effect remains unknown. As the prevertebral fascia encloses the phrenic nerves, BP and erector spinae muscles to form a prevertebral compartment, a local anesthetic injected in the cervical ESP could potentially spread throughout the prevertebral compartment. This study utilizes cadaveric models to evaluate the spread of ESP injections at the C6 and C7 levels to determine whether the injection can reach the BP and its surrounding structures.

Methods

For each of the five cadavers, an ESP injection posterior to the transverse process of C6 was performed on one side, and an ESP injection posterior to the transverse process of C7 was performed on the contralateral side. Injections were performed under ultrasound guidance and consisted of a 20 mL mixture of 18 mL water and 2 mL India ink. After cadaver dissection, craniocaudal and medial-lateral extent of the dye spread in relation to musculoskeletal anatomy as well as direct staining relevant nerves was recorded. The degree of dye staining was categorized as “deep,” “faint,” or “no.”

Results

The phrenic nerve was deeply stained in 1 injection and faintly stained in 2 injections. Caudally, variable staining of C8 (100%) and T1 (50%) roots were seen. Faintly staining at C4 root was only seen in one sample (10%). There was variable staining of the anterior scalene muscles (40%) anterior to the BP and the rhomboid intercostal plane caudally (30%).

Conclusions

Ultrasound-guided cervical (C6 and C7) ESP injections consistently stain the roots of the BP and dorsal rami. This study supports the notion that the cervical ESP block has the potential to provide analgesia for patients undergoing shoulder and cervical spine surgeries.

Comparing two posterior quadratus lumborum block approaches with low thoracic erector spinae plane block: an anatomic study

BACKGROUND AND OBJECTIVES

Both posterior quadratus lumborum (QL) and erector spinae plane (ESP) blocks have been described as new truncal interfascial plane blocks. Distribution of injectate is influenced by fascial anatomy; therefore, different injection sites may produce similar spread. This anatomic study was designed to test the hypothesis that a posteromedial QL block at L2 level will more closely resemble a low thoracic ESP block when compared with the posterolateral approach at L2 level.

METHODS

Left-sided ESP blocks were performed in six cadavers at T10-11. Three of these cadavers received right-sided posteromedial QL block at L2, while the other three received right-sided posterolateral QL block at L2. All injections were composed of 20 mL methylcellulose 0.5 % mixed with India ink and 10 mL of Omnipaque (Iohexol) 240 mg/mL. CT 24 hours after injection and cadaver dissection were used to evaluate injectate spread.

RESULTS

Cephalocaudal spread of injectate by CT and cadaveric dissection was highly correlated (r=0.85 [95% CI 0.51 to 0.95]). Cadaver dissection showed ESP injectate spread deep to the muscle (mean [SD]) 11.7 (2.3) levels compared with 7.3 (1.2) levels for posterolateral QL and 9.7 (1.5) for posteromedial QL (p=0.04 overall, with a statistically significant pairwise difference between ESP and posterolateral QL only). The subcostal nerve and dorsal rami were commonly involved in most blocks, but the paravertebral space and ventral rami had inconsistent involvement. The lumbocostal ligament limited cranial spread from the posterlateral QL block approach.

CONCLUSIONS

The posteromedial QL block at L2 produces more cranial spread beyond the lumbocostal ligament than the posterolateral QL block, and this spread is comparable with a low thoracic ESP block. Both posterior QL and ESP blocks show unreliable spread of injectate to the paravertebral space and ventral rami, but the dorsal rami were frequently covered.

Regurgitation and pulmonary aspiration during cardio-pulmonary resuscitation (CPR) with a laryngeal tube: A pilot crossover human cadaver study

Background

High-quality chest compressions are imperative for Cardio-Pulmonary-Resuscitation (CPR). International CPR guidelines advocate, that chest compressions should not be interrupted for ventilation once a patient’s trachea is intubated or a supraglottic-airway-device positioned. Supraglottic-airway-devices offer limited protection against pulmonary aspiration. Simultaneous chest compressions and positive pressure ventilation both increase intrathoracic pressure and potentially enhances the risk of pulmonary aspiration. The hypothesis was, that regurgitation and pulmonary aspiration is more common during continuous versus interrupted chest compressions in human cadavers ventilated with a laryngeal tube airway.

Methods

Twenty suitable cadavers were included, and were positioned supine, the stomach was emptied, 500 ml of methylene-blue-solution instilled and laryngeal tube inserted. Cadavers were randomly assigned to: 1) continuous chest compressions; or, 2) interrupted chest compressions for ventilation breaths. After 14 minutes of the initial designated CPR strategy, pulmonary aspiration was assessed with a flexible bronchoscope. The methylene-blue-solution was replaced by 500 ml barium-sulfate radiopaque suspension. 14 minutes of CPR with the second designated ventilation strategy was performed. Pulmonary aspiration was then assessed with a conventional chest X-ray.

Results

Two cadavers were excluded for technical reasons, leaving 18 cadavers for statistical analysis. Pulmonary aspiration was observed in 9 (50%) cadavers with continuous chest compressions, and 7 (39%) with interrupted chest compressions (P = 0.75).

Conclusion

Our pilot study indicate, that incidence of pulmonary aspiration is generally high in patients undergoing CPR when a laryngeal tube is used for ventilation. Our study was not powered to identify potentially important differences in regurgitation or aspiration between ongoing vs. interrupted chest compression. Our results nonetheless suggest that interrupted chest compressions might better protect against pulmonary aspiration when a laryngeal tube is used for ventilation.

National survey on anatomical sciences in medical education

The drivers for curricular change in medical education such as the addition of innovative approaches to teaching, inclusion of technology and adoption of different assessment methods are gaining momentum. In an effort to understand how these changes are impacting and being implemented in gross anatomy, microscopic anatomy, neuroanatomy/neuroscience, and embryology courses, surveys were sent out to course directors/discipline leaders at allopathic Medical Schools in the United States during the 2016-2017 academic year. Participants in the study were asked to comment on course hours, student experiences in the classroom and laboratory, amount of faculty participation, the use of peers as teachers in both the classroom and laboratory, methods used for student assessment and identification of best practices. Compared to data published from a similar survey in 2014, a number of changes were identified: (1) classroom hours in gross anatomy increased by 24% and by 29% in neuroanatomy/neuroscience; (2) laboratory hours in gross anatomy decreased by 16%, by 33% in microscopic anatomy, and by 38% in neuroanatomy/neuroscience; (3) use of virtual microscopy in microscopic anatomy teaching increased by 129%; and (4) the number of respondents reporting their discipline as part of a partially or fully integrated curriculum increased by greater than 100% for all four disciplines. Anat Sci Educ 11: 7-14. © 2017 American Association of Anatomists.

Surgical hip dislocation through a direct lateral approach: A cadaveric study of vascular danger zones

OBJECTIVE

There is limited information on the potential danger to the vascularity of the femoral head during surgical dislocation of the hip using the direct lateral approach. The objective of this study was to investigate the topographical anatomy of the medial femoral circumflex artery (MFCA), the primary source of blood supply to the femoral head, in relationship to the direct lateral approach.

METHODS

Seven unembalmed cadaver hips had dye injection into either the profunda femoris artery or the MFCA. Surgical hip dislocation was then performed through a direct lateral approach, noting the danger zones to the MFCA branches during each step of the exposure.

RESULTS

None of the MFCA branches were found to cross the anterior surgical field superficial to the capsule. The deep (main) branch of the MFCA pierced the inferior capsule at the level of the lesser trochanter after emerging posterior to iliopsoas tendon. Ascending branches up the medial femoral neck were identified at this level. The deep branch then coursed posteriorly terminating in a variable number of vessels ascending the posterior femoral neck. Dislocation of the femoral head did not stretch or alter the course of the deep branch of the MFCA.

CONCLUSION

Safe surgical hip dislocation preserving the MFCA can be performed though a direct lateral approach as long as the inferomedial portion of the anterior capsule is preserved (main branch of the MFCA pierces the capsule at this level). Extracapsular injury is possible from inadvertent dissection at the level of the lesser trochanter or aggressive retraction on the iliopsoas. The posterior capsule should be left intact and instrumentation around the posterior neck should be avoided.

Longitudinal cohort study on medical student retention of anatomical knowledge in an integrated problem-based learning curriculum

BACKGROUND

When modifying a curriculum to accommodate changes in the methods of subject matter presentation or fit within a shortened time frame, student retention of knowledge remains an important issue.

AIM

This study evaluates medical student retention of anatomical knowledge as they matriculate through an anatomy curriculum where the instruction hours are less than half of the current national average.

METHOD

Medical students completed an assessment tool developed to evaluate their baseline level of anatomical knowledge at the beginning of the first year. They then completed the instrument at the end of their 1st, 2nd, 3rd, and 4th years to assess their retention of anatomical knowledge during medical school. Data collection began in September 2010 and concluded in June 2015.

RESULTS

Results demonstrate that students began medical school with a low level of anatomical knowledge (baseline), that knowledge increased during their first year (p < 0.001), continued to increase during their second year (p < 0.001), but was over 90% maintained through years 3 and 4.

CONCLUSION

In conclusion, an anatomy course with reduced hours (∼60), using active learning methods, contextual learning, cadaver demonstrations, increased exposure to imaging, and longitudinal reinforcement can help students build a strong foundation of anatomical knowledge.

Student perceptions of an interprofessional educational experience: The importance of goal articulation

The education of future health care professionals must involve activities where interprofessional collaboration and the functioning of interdisciplinary teams are the goals and not the exceptions. This type of interprofessional education (IPE) will benefit students as they will be better able to communicate with and mobilize the skills of other health care workers, work toward common goals related to patient care, and develop a more cost-effective treatment strategy in the long term. Such an IPE program was initiated in the clinical anatomy course for physician assistant students from the University of Mount Union that was taught, in part, by medical students from the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University. Surveys of both student groups at the end of the course indicated that although this was a useful IPE experience, the value of this program as an IPE experience was not entirely appreciated by the participating students. It turned out that although the goals and importance of these types of IPE activities are clear to the faculty, they must also be made clear to all of the students.

International association for the study of lung cancer (IASLC) lymph node map: radiologic review with CT illustration

Accurate clinical or pretreatment stage classification of lung cancer leads to optimal treatment outcomes and improved prognostication. Such classification requires an accurate assessment of the clinical extent of regional lymph node metastasis. Consistent and reproducible regional lymph node designations facilitate reliable assessment of the clinical extent of regional lymph node metastasis. Regional lymph node maps, such as the Naruke lymph node map and the Mountain-Dresler modification of the American Thoracic Society lymph node map, were proposed for this purpose in the past. The most recent regional lymph node map to be published is the International Association for the Study of Lung Cancer (IASLC) lymph node map. The IASLC lymph node map supersedes all previous maps and should be used in tandem with the current seventh edition of the tumor, node, metastasis stage classification for lung cancer.

An update on the status of anatomical sciences education in United States medical schools

Curricular changes continue at United States medical schools and directors of gross anatomy, microscopic anatomy, neuroscience/neuroanatomy, and embryology courses continue to adjust and modify their offerings. Developing and supplying data related to current trends in anatomical sciences education is important if informed decisions are going to be made in a time of curricular and course revision. Thus, a survey was sent to course directors during the 2012-2013 academic years to gather information on total course hours, lecture and laboratory hours, the type of laboratory experiences, testing and competency evaluation, and the type of curricular approach used at their institution. The data gathered were compared to information obtained from previous surveys and conclusions reached were that only small or no change was observed in total course, lecture and laboratory hours in all four courses; more gross anatomy courses were part of an integrated curriculum since the previous survey; virtual microscopy with and without microscopes was the primary laboratory activity in microscopic anatomy courses; and neuroscience/neuroanatomy and embryology courses were unchanged.

A failsafe method to avoid injury to the great auricular nerve

BACKGROUND

The great auricular nerve (GAN) is the most commonly injured nerve during facelift surgery. Although rare, injury can result in long-term sequelae.

OBJECTIVES

Previous reports have described the nerve's location at the midbelly of the sternocleidomastoid muscle (SCM) or at its emergence from underneath the SCM. The purpose of our study was to identify the superior course of the great auricular nerve as it applies to facelift.

METHODS

Thirteen fresh cadavers were dissected. A vertical line through the midlobule was drawn perpendicular to the Frankfort's horizontal, acting as a reference to the course of the GAN. Transparent paper overlay tracings were then done to record each nerve's location. The distance from the bony external auditory canal (EAC) to the nerve was measured at the anterior muscle border, at the midbelly of the SCM, and as the nerve emerged from under the SCM. Branching patterns of the nerve and its relation to the external jugular vein were identified.

RESULTS

In 100% of the dissections, the superior course of the GAN fell within a 30-degree angle constructed using the vertical limb perpendicular to the Frankfurt horizontal and a second limb drawn posteriorly from the midlobule. The distance from the EAC to the nerve was 4.9 ± 1.1 cm at the anterior muscle border, 7.3 ± 1.0 cm at the midbelly of the SCM, and 9.8 ± 1.2 cm at the GAN's emergence from under the SCM. Four types of branching patterns were identified.

CONCLUSIONS

The 30-degree angle described above rapidly and accurately identifies the nerve's location.

Validation of a method for measuring medical students' critical reflections on professionalism in gross anatomy

Improving professional attitudes and behaviors requires critical self reflection. Research on reflection is necessary to understand professionalism among medical students. The aims of this prospective validation study at the Mayo Medical School and Cleveland Clinic Lerner College of Medicine were: (1) to develop and validate a new instrument for measuring reflection on professionalism, and (2) determine whether learner variables are associated with reflection on the gross anatomy experience. An instrument for assessing reflections on gross anatomy, which was comprised of 12 items structured on five-point scales, was developed. Factor analysis revealed a three-dimensional model including low reflection (four items), moderate reflection (five items), and high reflection (three items). Item mean scores ranged from 3.05 to 4.50. The overall mean for all 12 items was 3.91 (SD = 0.52). Internal consistency reliability (Cronbach's α) was satisfactory for individual factors and overall (Factor 1 α = 0.78; Factor 2 α = 0.69; Factor 3 α = 0.70; Overall α = 0.75). Simple linear regression analysis indicated that reflection scores were negatively associated with teamwork peer scores (P = 0.018). The authors report the first validated measurement of medical student reflection on professionalism in gross anatomy. Critical reflection is a recognized component of professionalism and may be important for behavior change. This instrument may be used in future research on professionalism among medical students.

A retrospective and prospective look at medical education in the United States: trends shaping anatomical sciences education

During the last decade of the 20th century and the first decade of the 21st century, curricular reform has been a popular theme. In fact, reform on the current scale has not occurred since the early 1900s, when Abraham Flexner released his landmark report 'Medical Education in the United States and Canada'. His report, suggesting major changes in how physicians were educated, became the norm and few changes occurred until the last quarter of the 20th century. During this period increased demands on medical school curriculums due to the explosion of knowledge in biomedical sciences and the pressure to add additional clinical experiences increased the momentum for curriculum reform. In 1984 an Association of American Medical Colleges (AAMC) report, 'Physicians for the Twenty-First Century: The Report of the Panel on the General Professional Education of the Physician (GPEP) and College Preparation for Medicine', discussed many items related to reforming medical education including the value of integration, increased use of active learning formats, more self-directed learning, improved communication skills and increased problem-solving activities. This was followed by a report released in 1993 entitled 'Educating Medical Students: Assessing Change in Medical Education - The Road to Implementation' (ACME-TRI), which identified educational problems by surveying medical school deans, suggested ways to deal with these issues and presented a plan of action. Recently, the Carnegie Foundation for the Advancement of Teaching released 'Education Physicians: A Call for Reform of Medical School and Residency' with additional suggestions. At this point the question that might be asked is - Where is all this going and how is it going to affect anatomy education?

Changes in anatomy instruction and USMLE performance: empirical evidence on the absence of a relationship

Anatomy instruction has evolved over the past two decades as many medical schools have undergone various types of curricular reform. To provide empirical evidence about whether or not curricular changes impact the acquisition and retention of anatomy knowledge, this study investigated the effect of variation in gross anatomy course hours, curricular approach (stand-alone versus integrated), and laboratory experience (dissection versus dissection and prosection) on USMLE Steps 1 and 2 Clinical Knowledge (CK) scores. Gross anatomy course directors at 54 United States schools provided information about their gross anatomy courses via an online survey (response rate of 42%). Survey responses were matched with USMLE scores for 6,411 examinees entering LCME-accredited schools in 2007 and taking Step 1 for the first time in 2009. Regression analyses were conducted to examine relationships between gross anatomy instructional characteristics and USMLE performance. Step 1 total scores, Step 1 gross anatomy sub-scores, and Step 2 CK scores were unrelated to instructional hours, controlling for MCAT scores. Examinees from schools with integrated curricula scored slightly lower on Steps 1 and 2 CK than those from stand-alone courses (effect sizes of 2.1 and 1.9 on score scales with SDs of 22 and 20, respectively). Examinees with dissection and prosection experience performed slightly better on Step 2 CK than examinees in courses with dissection only laboratories (effect size of 1.2). Results suggest variation in course hours is unrelated to performance on Steps 1 and 2 CK. Although differences were observed in relation to curricular approach and laboratory experience, effect sizes were small.

Student-directed fresh tissue anatomy course for physician assistants

Healthcare providers in all areas and levels of education depend on their knowledge of anatomy for daily practice. As educators, we are challenged with teaching the anatomical sciences in creative, integrated ways and often within a condensed time frame. This article describes the organization of a clinical anatomy course with a peer taught unembalmed (fresh-tissue) cadaver laboratory in the 2010 summer term of a new physician assistant program. To fit within the allotted 12 week time frame, students meet every Monday for both the classroom and laboratory component of the course. Students prepare for these sessions by reviewing a list of learning objectives and completing assigned textbook readings. Classroom sessions involve faculty presentations and are facilitated with the use of self-assessment questions and accompanying images. The afternoon laboratory sessions which follow the classroom sessions are comprised of four to five stations presented by first- and second-year medical students and a resident radiologist. End of course evaluations indicate that students felt that the course objectives were clear, achievable, and taught effectively with relevant clinical correlates.

Rewarding the resident teacher

Residents routinely make significant contributions to the education of medical students. However, little attention has been paid to rewarding these individuals for their involvement in these academic activities. This report describes a program that rewards resident teachers with an academic appointment as a Clinical Instructor. The residents participate in the laboratory portion of the anatomy program at the Cleveland Clinic Lerner College of Medicine. They prepare weekly cadaver dissections and present these dissections to the first year medical students. Guidelines developed by the anatomy faculty and approved by the appropriate committees at both the Cleveland Clinic and Case Western Reserve University establish requirements that a resident must meet to qualify for an academic appointment. Evaluation of this program indicates that it has been very successful based on medical student feedback, resident interest in gaining teaching experience, and residency directors appreciation of the opportunity for residents to gain valuable teaching experience in an academic setting.

Medical education in the anatomical sciences: the winds of change continue to blow

At most institutions, education in the anatomical sciences has undergone several changes over the last decade. To identify the changes that have occurred in gross anatomy, microscopic anatomy, neuroscience/neuroanatomy, and embryology courses, directors of these courses were asked to respond to a survey with questions pertaining to total course hours, hours of lecture, and hours of laboratory, whether the course was part of an integrated program or existed as a stand-alone course, and what type of laboratory experience occurred in the course. These data were compared to data obtained from a similar survey in 2002. Comparison between the data sets suggests several key points some of which include: decreased total hours in gross anatomy and neuroscience/neuroanatomy courses, increased use of virtual microscopy in microscopic anatomy courses, and decreased laboratory hours in embryology courses.

The use of simulation in medical education to enhance students' understanding of basic sciences

Simulation! The deans talk about its use in medical education regularly. But how can it be used to teach the basic sciences to first- and second-year medical students? This article will help answer that question by providing information about various types of simulation activities being used in medical education and examples of their application to basic science education. The next step depends on your creativity.

Nonuniform pressure generation in the optic chiasm may explain bitemporal hemianopsia

PURPOSE

To measure the pressure in the temporal and central aspects of the chiasm simultaneously during compression of the optic chiasm from below with an expanding simulated tumor.

DESIGN

Experimental study.

METHODS

Craniotomies were performed on 5 unfixed cadaveric specimens ranging in age from 49 to 89 years, and the optic chiasm was exposed. After a pediatric gauge Foley catheter was inserted into the sellar region, the temporal side of the chiasm (temporal aspect uncrossed fibers) was impaled with a 30-gauge needle connected to a pressure transducer. In like fashion, the central portion of the chiasm (crossed fibers) was impaled with another 30-gauge needle connected to a pressure transducer on a separate channel. The Foley catheter was inflated for a period of 30 seconds to 1 minute and the pressure in each channel continuously monitored. Multiple trials were performed on each of the 5 specimens.

MAIN OUTCOME MEASURE

Pressure change between the temporal and nasal aspects of the optic chiasm.

RESULTS

In all cases in which intrachiasmal pressure could be measured, higher pressures were always generated in the central aspect of the chiasm than in the temporal aspect of the chiasm. In cadaver 1, the mean central pressure was 19.75 mmHg, whereas the mean temporal pressure was 6 mmHg. In cadaver 5, the mean central pressure was 4 mmHg, whereas the mean temporal pressure was zero. Donors 70 and older demonstrated abnormally thin and frail chiasms that were unable to support a sustained pressure increase during simulated tumor expansion.

CONCLUSIONS

During deformation of the optic chiasm from below by a radially expanding mass analogous to a pituitary tumor, the central aspect of the optic chiasm consistently manifests a higher pressure than the temporal aspect. It is hypothesized that the peculiar geometry of the optic chiasm renders the crossing nasal fibers more prone to a deformation stress exerted from below. Nonuniform pressure generation between the central and temporal aspects of the chiasm results in a greater effective stress on the crossing fibers of the chiasm and may be responsible for the clinical phenomenon of bitemporal hemianopsia.

Anatomists debate the value of a teaching credential

Fewer and fewer programs are training graduate students and postdoctoral fellows in the classical anatomical disciplines. Nonetheless, there remains a need at all levels of clinical and basic science education for skilled instructors of anatomy, histology, and embryology. Two sessions at the 2006 annual meeting of the American Association of Anatomists (AAA) explored whether a system of accreditation would benefit students, institutions, and training programs. Although the value of accreditation was controversial, three challenges for the various anatomical societies emerged from these discussions: (1) To identify the skills and knowledge that should be shared among all anatomists, and the more specific skills and knowledge needed for the diverse settings in which anatomists work. (2) To address the historical inattention of institutions to the training of educators. (3) To develop strategies to lobby institutions and national organizations to support the training and work of educators in the anatomical sciences. One approach to meeting these challenges would be to develop guidelines for training programs. These guidelines would help graduate students seek the training they need, provide institutions with a benchmark to assess or develop training programs, and provide the basis for focusing lobbying efforts targeted at institutions or existing accreditation bodies.