Atypical location of the hypoglossal nerve and its implications: a case report

Introduction

Successful surgery in the neck is dependent on reliable anatomical relationships between nerves, vessels, and muscles. These landmarks and planes are also essential to avoiding undue morbidity and mortality. Anatomic variants of the hypoglossal nerve are rare, and their incidences are unknown.

Methods

We describe a case of a hypoglossal nerve found coursing superficial to the internal jugular vein in a 52-year-old woman treated with bilateral selective neck dissection for metastatic thyroid malignancy.

Results

The vulnerable nerve was protected, and she maintained excellent speech and swallow function post-operatively.

Conclusions

The variant course of the nerve may pose higher risk for injury in neck surgery. Surgeons should be aware of the possibility of aberrant anatomy in this region and exercise extra caution to avoid nerve injury.

     

Intramuscular innervations of lower leg skeletal muscles: applications in their clinical use in functional muscular transfer

Purpose

This study aims to investigate nerve distribution patterns of human lower leg skeletal muscles using a modified Sihler’s staining method.

Methods

Sixteen lower leg from eight fresh adult cadavers were used in this study and all the skeletal muscles were dissected. The muscle specimens were classified according to Lim’s classification. The specimens were then stained by further modified Sihler’s staining technique. Data were analyzed according to research results.

Results

After the staining, we found four patterns of nerve distribution in human lower leg muscles: (1) Type 1: single nerve pattern in which the nerve branches into two either running parallel to each other or radiating in a spray pattern (such as the extensor digitorum longus, extensor hallucis longus, fibularis brevis and flexor hallucis longus). (2) Type 2: double nerve pattern, one being proximal and the other being distal (such as the extensor digitorum longus, flexor digitorum longus, flexor hallucis longus). (3) Type 3: multiple branch pattern (such as the tibialis anterior, fibularis longus, gastrocnemius, soleus, tibialis anterior and popliteus).

Conclusion

Our modified Sihler’s staining method is useful for research of large muscles and intramuscular nerves in human. These findings might provide guidance for clinicians for muscle reconstruction surgery.

     

The styloauricular muscle: clinical relevance and literature review of this rare muscle

Purpose

In humans, the styloauricularis is a rare muscle extending from the tragal cartilage of the auricle to the styloid process. When it contracts, by bearing on the styloid process, it increases the cephalo-auricular angle. It can be a landmark for the facial nerve. We report a case with bilateral presence of the styloauricularis.

Methods

Bilateral presence of the styloauricularis was discovered during routine dissection of the head and neck.

Results

In the presented case, styloauricularis muscles arose from the cartilage of the external acoustic meatus on both sides of the head, crossing halfway along the facial nerve trunk and inserting the styloid process. Both muscles were vascularized by a branch of the posterior auricular artery, and innervated by the facial nerve.

Conclusions

The ventral auricular muscle, formed by the auricular parotid and the styloauricular muscles, is a muscle that lowers and abducts the auricle in animals. There is generally considered to be no equivalent for these muscles in humans, however, this bilateral case reveals evidence to the contrary. There is a dearth of scientific literature about the styloauricularis. The study of this muscle demonstrated the usefulness of comparative anatomy in understanding its action in increasing the cephalo-auricular angle.

     

Numerical modeling of percutaneous auricular vagus nerve stimulation: a realistic 3D model to evaluate sensitivity of neural activation to electrode position

Objective

Percutaneous stimulation of the auricular branch of the vagus nerve (pVNS) by miniaturized needle electrodes in the auricle gained importance as a treatment for acute and chronic pain. The objective is to establish a realistic numerical model of pVNS and investigate the effects of stimulation waveform, electrodes’ depth, and electrodes’ position on nerve excitation threshold and the percentage of stimulated nerves.

Methods

Simulations were performed with Sim4Life. An electrostatic solver and neural tissue models were combined for electromagnetic and neural simulation. The numerical model consisted of a realistic high-resolution model of a human ear, blood vessels, nerves, and three needle electrodes.

Results

A novel 3D ear model was established, including blood vessels and nerves. The electric field distribution was extracted and evaluated. Maximum sensitivity to needles’ depth and displacement was evaluated to be 9.8 and 15.5% per 0.1 mm, respectively. Stimulation was most effective using biphasic compared to mono-phasic pulses.

Conclusion

The established model allows easy and quantitative evaluation of various stimulation setups, enabling optimization of pVNS in experimental settings. Results suggest a high sensitivity of pVNS to the electrodes’ position and depth, implying the need for precise electrode positioning. Validation of the model needs to be performed.

     

An anatomic study of the attachments on the condylar process of the mandible: muscle bundles from the temporalis

Purpose

The aim of this study was to evaluate anatomically the relationship between bone and muscles by detailed observation of the bone shape and the structure of muscles to facilitate an understanding of the function of the muscles involved in jaw movement.

Methods

36 specimens of 24 Japanese cadavers were examined. The insertion areas were marked using a radiopaque marker and examined by micro-computed tomography. For morphological observation, we used 101 condylar processes. In addition, we made histological sections in some specimens to observe the detailed attachments of the muscle.

Results

Based on the micro-CT images and dissection findings, the lateral pterygoid muscle was found to be most frequently inserted into the anterior impression and attached to the medial impression of the process. According to the histological observations, the lateral pterygoid muscle mainly inserted to the condylar process. The micro-CT images indicated that the obvious bony ridge was lateral to the pterygoid fovea on the condylar process in all specimens. The midmedial muscle bundle of the temporalis was attached to the ridge. Based on the morphological observations, the ridge was situated on the lateral area of the condylar process.

Conclusions

Since dysfunction of the temporomandibular joint is likely closely related to both the lateral pterygoid muscle and also the temporalis, further studies are necessary to evaluate the function of these muscles and consider jaw movement.

     

Neural connections between the nervus intermedius and the facial and vestibulocochlear nerves in the cerebellopontine angle: an anatomic study

Purpose

Unexpected clinical outcomes following transection of single nerves of the internal acoustic meatus have been reported. Therefore, this study aimed to investigate interneural connections between the nervus intermedius and the adjacent nerves in the cerebellopontine angle.

Methods

On 100 cadaveric sides, dissections were made of the facial/vestibulocochlear complex in the cerebellopontine angle with special attention to the nervus intermedius and potential connections between this nerve and the adjacent facial or vestibulocochlear nerves.

Results

A nervus intermedius was identified on all but ten sides. Histologically confirmed neural connections were found between the nervus intermedius and either the facial or vestibulocochlear nerves on 34 % of sides. The mean diameter of these small interconnecting nerves was 0.1 mm. The fiber orientation of these nerves was usually oblique (anteromedial or posterolateral) in nature, but 13 connections traveled anteroposteriorly. Connecting fibers were single on 81 % of sides, doubled on 16 %, and tripled on 3 %, six sides had connections both with the facial nerve anteriorly and the vestibular nerves posteriorly. On 6.5 % of sides, a connection was between the nervus intermedius and cochlear nerve. For vestibular nerve connections with the nervus intermedius, 76 % were with the superior vestibular nerve and 24 % with the inferior vestibular nerve.

Conclusions

Knowledge of the possible neural interconnections found between the nervus intermedius and surrounding nerves may prove useful to surgeons who operate in these regions so that inadvertent traction or transection is avoided. Additionally, unanticipated clinical presentations and exams following surgery may be due to such neural interconnections.

     

Anatomical study of the motor branches of the median nerve to the forearm and guidelines for selective neurectomy

Purpose

The median nerve is responsible for the motor innervation of most of the muscles usually involved in upper limb spasticity. Selective neurectomy is one of the treatments utilized to reduce spasticity. The purpose of this study was to describe the variations of the motor branches of the median nerve in the forearm and draw recommendations for an appropriate planning of selective neurectomy.

Materials and methods

The median nerve was dissected in the forearm of 20 fresh cadaver upper limbs. Measurements included number, origin, division, and entry point of each motor branch into the muscles.

Results

One branch for the pronator teres was the most common pattern. In 9/20 cases, it arose as a common trunk with other branches. A single trunk innervated the flexor carpi radialis with a common origin with other branches in 17/20 cases. Two, three or four branches innervated the flexor digitorum superficialis, the first one frequently through a common trunk with other branches. They were very difficult to identify unless insertions of pronator teres and flexor digitorum superficialis were detached. The flexor digitorum profundus received one to five branches and flexor pollicis longus one to two branches from the anterior interosseous nerve.

Conclusions

There is no regular pattern of the motor branches of the median nerve in the forearm. Our findings differ in many points from the classical literature. Because of the frequency of common trunks for different muscles, we recommend the use of peroperative electrical stimulation. Selective neurotomy of flexor digitorum superficialis is technically difficult, because the entry point of some of their terminal branches occurs just below the arch and deep to the muscle belly.

     

Reference data on muscle volumes of healthy human pelvis and lower extremity muscles: an in vivo magnetic resonance imaging feasibility study

Purpose

Muscle volumes are of crucial interest when attempting to analyze individual physical performance and disease- or age-related alterations in muscle morphology. However, very little reference data are available in the literature on pelvis and lower extremity muscle volumes originating from healthy and young individuals. Furthermore, it is of interest if representative muscle volumes, covering large anatomical regions, can be obtained using magnetic resonance imaging (MRI) in a setting similar to the clinical routine. Our objective was therefore to provide encompassing, bilateral, 3-T MRI-based datasets on muscle volumes of the pelvis and the lower limb muscles.

Methods

T1-weighted 3-T MRI records were obtained bilaterally from six young and healthy participants. Three-dimensional volumes were compiled from 28 muscles and muscle groups of each participant before the muscle volumes were computed.

Results

Muscle volumes were obtained from 28 muscles and muscle groups of the pelvis and lower extremity. Volumes were larger in male than in female participants. Volumes of the dominant and non-dominant sides were similar in both genders. The obtained results were in line with volumetric data obtained from smaller anatomical areas, thus extending the available datasets.

Conclusions

This study provides an encompassing and feasible approach to obtain data on the muscle volumes of pelvic and limb muscles of healthy, young, and physically active individuals. The respective data form a basis to determine effects of therapeutic approaches, progression of diseases, or technical applications like automated segmentation algorithms applied to different populations.

     

Coordination of intrinsic and extrinsic foot muscles during walking

Purpose

The human foot undergoes complex deformations during walking due to passive tissues and active muscles. However, based on prior recordings it is unclear if muscles that contribute to flexion/extension of the metatarsophalangeal (MTP) joints are activated synchronously to modulate joint impedance, or sequentially to perform distinct biomechanical functions. We investigated the coordination of MTP flexors and extensors with respect to each other, and to other ankle–foot muscles.

Methods

We analyzed surface electromyographic (EMG) recordings of intrinsic and extrinsic foot muscles for healthy individuals during level treadmill walking, and also during sideways and tiptoe gaits. We computed stride-averaged EMG envelopes and used the timing of peak muscle activity to assess synchronous vs. sequential coordination.

Results

We found that peak MTP flexor activity occurred significantly before peak MTP extensor activity during walking (P < 0.001). The period around stance-to-swing transition could be roughly characterized by sequential peak muscle activity from the ankle plantarflexors, MTP flexors, MTP extensors, and then ankle dorsiflexors. We found that foot muscles that activated synchronously during forward walking tended to dissociate during other locomotor tasks. For instance, extensor hallucis brevis and extensor digitorum brevis muscle activation peaks decoupled during sideways gait.

Conclusions

The sequential peak activity of MTP flexors followed by MTP extensors suggests that their biomechanical contributions may be largely separable from each other and from other extrinsic foot muscles during walking. Meanwhile, the task-specific coordination of the foot muscles during other modes of locomotion indicates a high-level of specificity in their function and control.

     

Micronized palmitoylethanolamide reduces joint pain and glial cell activation

Objective and design

Temporomandibular disorder (TMD) is a common painful condition in the temporomandibular joint (TMJ). Joint inflammation is believed to be a chief cause of pain in patients with TMD, through the release of pro-inflammatory cytokines that induce peripheral sensitization of nerve terminals followed by microglial stimulation.

Materials and subject

TMJ was induced in rats with the injection of complete Freund’s adjuvant (CFA) emulsion into the left TMJ capsule.

Treatment

The present study would assess the effects of micronized palmitoylethanolamide (m-PEA) on glial activation and trigeminal hypersensitivity.

Methods

Ten mg/kg m-PEA or corresponding vehicle was administered 1 h after CFA and mechanical allodynia and edema were evaluated at 24 and 72 h after CFA injection.

Results

CFA-injected animals showed TMJ edema and ipsilateral mechanical allodynia accompanied by a robust growth in GFAP protein-positive satellite glial cells and activation of resident macrophages in the TG. Moreover, m-PEA administration significantly reduced the degree of TMJ damage and pain, macrophage activation in TG and up-regulation of Iba1.

Conclusions

The results confirm that m-PEA could represent a novel approach for monitoring pain during trigeminal nerve sensitization.

     

Correlation of ultrasound appearance,gross anatomy,and histology of the femoral nerve at the femoral triangle

Purpose

Correlation between ultrasound appearance, gross anatomic characteristics, and histologic structure of the femoral nerve (FN) is lacking. Utilizing cadavers, we sought to characterize the anatomy of the FN, and provide a quantitative measure of its branching. We hypothesize that at the femoral crease, the FN exists as a group of nerve branches, rather than a single nerve structure, and secondarily, that this transition into many branches is apparent on ultrasonography.

Materials and methods

Nineteen preserved cadavers were investigated. Ultrasonography was sufficient to evaluate the femoral nerve in nine specimens; gross dissection was utilized in all 19. Anatomic characteristics were recorded, including distances from the inguinal ligament to femoral crease, first nerve branch, and complete arborization of the nerve. The nerves from nine specimens were excised for histologic analysis.

Results

On ultrasound, the nerve became more flattened, widened, and less discrete as it coursed distally. Branching of the nerve was apparent in 12 of 18 images, with mean distance from inguinal ligament of 3.9 (1.0) cm. However, upon dissection, major branching of the femoral nerve occurred at 3.1 (1.0) cm distal to the inguinal ligament, well proximal to the femoral crease. Histologic analysis was consistent with findings at dissection.

Conclusion

The femoral nerve arborizes into multiple branches between the inguinal ligament and the femoral crease. Initial branching is often high in the femoral triangle. As hypothesized, the FN exists as a closely associated group of nerve branches at the level of the femoral crease; however, the termination of the nerve into multiple branches is not consistently apparent on ultrasonography.

     

Anatomical study of the morphological continuity between iliotibial tract and the fibularis longus fascia

Purpose

Recent research indicates that the skeletal muscles of the human body do not function as independent actuators. Instead, they seem to be linked by connective tissue forming myofascial chains. While the existence of such meridians has been demonstrated for the ventral and the dorsal side of the body, no data are available for morphological fusion of lateral muscles. This study aimed to provide evidence for the inferior part of the lateral myofascial chain.

Methods

Fourteen legs (7 embalmed cadavers, four ♂, 86 ± 7 years) were dissected to reveal a potential myofascial continuity between the fibularis longus muscle, more detailed, its fascia, and the iliotibial tract (ITT). Three investigators judged the general existence as well as the degree and characteristics of the continuity. If an anatomical continuity was evident, strain was applied to both structures in order to evaluate the tissues’ ability for tensile transmission.

Results

An indirect connection between the iliotibial tract and the fascia of the fibularis longus muscle was found: in all examined legs, the ITT fused strongly with the crural fascia. The latter was hardly separable from the fibularis longus fascia. Application of strain to the ITT caused local movement in the crural fascia and the underlying fascia of the fibularis muscle.

Conclusions

The iliotibial tract fuses firmly with the crural fascia and the degree of continuity suggests that moderate amounts of strain might be transmitted. However, biomechanical studies precisely quantifying this tensile transmission are warranted in order to estimate the relevance of the linkage for the locomotor system.

     

Intermuscular aponeuroses between the flexor muscles of the forearm and their relationships with the ulnar nerve

Introduction

The aim of this study was to clarify the morphological characteristics of the intermuscular aponeurosis between the flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS; IMAS), and that between the FCU and flexor digitorum profundus (FDP; IMAP), and their topographic relationships with the ulnar nerve.

Materials and methods

Fifty limbs of 38 adult cadavers were studied.

Results

The IMAS extended along the deep surface of the FCU adjoining the FDS, having the appearance of a ladder, giving off “steps” that decreased in width from superficial to deep around the middle of the forearm. Its proximal part divided into two bands connected by a thin membrane, and was attached to the medial epicondyle and the tubercle (the most medial prominent part of the coronoid process of the ulna), respectively. The IMAP extended deep between the FCU and FDP from the antebrachial fascia, and its distal end was located on the posterior border of the FCU. The IMAP became broader toward its proximal part, and its proximal end was attached anterior and posterior to the tubercle and the olecranon, respectively. The ulnar nerve passed posterior to the medial epicondyle and then medial to the tubercle, and was crossed by the deep border of the IMAS at 58.3 ± 14.1 mm below the medial epicondyle.

Conclusion

The deep border of the IMAS and aberrant tendinous structure passing across the ulnar nerve, or the parts of the IMAS and IMAP passing posterior to the ulnar nerve are potential causes of ulnar nerve compression.

     

Anatomic basis and clinical application of the distally based medialis pedis flaps

Background

Soft-tissue defects of the forefoot are difficult to cover adequately, particularly, although multiple options for reconstruction are available. This study especially focused on the vascularization of the medial side of the foot and the determination of the contribution of the nutrient vessels to medialis pedis flap viability.

Methods

Thirty cadavers were available for this anatomical study. Microdissection was conducted under a microscope, and details of the course and distribution and the communication of the first plantar metatarsal artery with the fascial vascular network of the medial side of the foot were recorded. Clinically, six cases of soft-tissue defects at the forefoot region were reconstructed with distally based medialis pedis flap.

Results

The perforator of the first plantar metatarsal artery pierces in the superficial fascia of the medial aspect of the foot 2.2 ± 0.7 cm proximal to the first metatarsophalangeal joint, vascularize the skin of the medial plantar region. The anatomical study showed that the vasculature pattern could roughly be classified into two types. In terms of clinical application, all flaps completely survived, and one patient had partial loss of skin graft.

Conclusion

The perforators of the medialis pedis flap are presented constant. The forefoot region can be repaired by the distally based medialis pedis flap on the perforator of the medial plantar artery of the hallux or the first plantar metatarsal artery perforator with medial plantar vein, medial plantar cutaneous nerve and nutrient vessels.

     

Trapezius muscle activity increases during near work activity regardless of accommodation/vergence demand level

Aim

To investigate if trapezius muscle activity increases over time during visually demanding near work.

Methods

The vision task consisted of sustained focusing on a contrast-varying black and white Gabor grating. Sixty-six participants with a median age of 38 (range 19–47) fixated the grating from a distance of 65 cm (1.5 D) during four counterbalanced 7-min periods: binocularly through ?3.5 D lenses, and monocularly through ?3.5 D, 0 D and +3.5 D. Accommodation, heart rate variability and trapezius muscle activity were recorded in parallel.

Results

General estimating equation analyses showed that trapezius muscle activity increased significantly over time in all four lens conditions. A concurrent effect of accommodation response on trapezius muscle activity was observed with the minus lenses irrespective of whether incongruence between accommodation and convergence was present or not.

Conclusions

Trapezius muscle activity increased significantly over time during the near work task. The increase in muscle activity over time may be caused by an increased need of mental effort and visual attention to maintain performance during the visual tasks to counteract mental fatigue.

     

Four cases of spinal accessory nerve passing through the fenestrated internal jugular vein

Purpose

Neck dissection (ND) is an important technique for the treatment of cervical lymph node metastasis in patients with head and neck cancer. Since the introduction of functional ND (FND), various modifications have been made to reduce the adverse effects of radical ND. Recently, many investigators have documented cases of FND with preservation of the spinal accessory nerve (SAN) and/or the sternocleidomastoid muscle, which have contributed to improve the quality of life following ND. For this type of ND, special attention must be paid to identify the SAN and the internal jugular vein (IJV).

Methods

We performed 123 NDs over 2 years at the Department of Otolaryngology, Head and Neck Surgery, Kobe University Hospital. We collected data of all patients who underwent NDs by retrospectively reviewing the relevant hospital medical records and operative notes.

Results

In 4 out of 123 NDs (3.3%), an anomaly of the SAN passing through the fenestrated IJV was observed.

Conclusion

Although this anomaly is rare, head and neck surgeons should be aware of this anomalous relationship between the SAN and the IJV in order to avoid accidental injury to these structures during ND.

     

Ethical Assessment of Human Embryonic Stem Cell Research According to Turkish Muslim Scholars: First Critical Analysis and Some Reflections

Background

Turkey, with a Muslim population of officially over 99 %, is one of the few secular states in the Muslim world. Although state institutions are not based on Islamic juridical and ethical norms, the latter play a significant role in defining people’s attitudes towards controversial issues in the modern world, especially when backed by opinions of Muslim scholars living in Turkey. Accordingly, opinions of Muslim scholars undoubtedly have an important effect on bioethical decisions made by institutions and individuals.

Objective(s)

To explore the ethical positions of Muslim scholars living in Turkey and their arguments used in the ethical assessment of embryonic stem cell research; to discuss the biological-moral tensions arising in medical research on human embryos.

Design

Qualitative study.

Setting

Muslim scholars located in different parts of Turkey.

Methods

Qualitative method, involving the collection of opinions of various scholars, by means of 15 individual semi-structured interviews, evaluated using thematic qualitative analysis.

Results

Positions regarding embryonic stem cell research differ among Muslim scholars in Turkey. On the other hand, even where positions are similar, they are often supported by different arguments.

Conclusion

Despite the heterogeneity of the arguments presented, the dominant position considers embryonic stem cell research as morally acceptable.

     

New anatomo-radiological findings of the lateral pterygoid muscle

Purpose

The discrepancies in the literature regarding the anatomy of the temporomandibular joint (TMJ), particularly at the level of the lateral pterygoid muscle, led us to compare plastinated section techniques and magnetic resonance imaging (MRI) to enable the better interpretation of both, and to describe the features of the lateral pterygoid muscle and the exact location of its insertions.

Methods

A total of 24 blocks of human TMJ were used. Seven were studied by MRI, obtaining images of the oblique-sagittal, oblique-coronal, and axial planes. Four of these blocks were then cut and processed by means of the E12 plastination technique. The remaining blocks were dissected. Finally, we performed a comparative morphological analysis of the different techniques used.

Results

New aspects about the morphology and the insertions of the lateral pterygoid muscle are described. The muscle is inserted into the disc, capsule, condyle, and the pterygoid fovea, through muscle and tendon fibres that alternate, giving it the characteristic of a multipennate muscle. This insertion caudally exceeded the pterygoid fovea and descends to near the lingula of mandible. A profuse pterygoid venous plexus surrounds the whole joint complex, and also the insertion zone of the lateral pterygoid muscle.

Conclusions

We consider that the use of transparent-plastinated anatomical sections and its good correlation with MRI images (in axial and oblique-sagittal planes) led to an accurate identification of TMJ structures, especially in relation to the lateral pterygoid muscle, that is now described as a multipennate muscle.

     

The Individual,Joint, and Additive Interaction Associations of Aerobic-Based Physical Activity and Muscle Strengthening Activities on Metabolic Syndrome

Purpose

Previous research has demonstrated that physical activity and muscle strengthening activities are independently and inversely associated with metabolic syndrome. Despite a number of studies examining the individual associations, only a few studies have examined the joint associations, and to our knowledge, no previous studies have examined the potential additive interaction of performing muscle strengthening activities and aerobic-based physical activity and their association with metabolic syndrome.

Method

Using data from the 2003 to 2006 National Health and Nutrition Examination Survey (NHANES), we computed three separate multivariable logistic regression models to examine the individual, combined, and additive interaction of meeting guidelines for accelerometer-assessed physical activity and self-reported muscle strengthening activities, and their association with metabolic syndrome.

Results

We found that individuals meeting physical activity and muscle strengthening activity guidelines, respectively, were at 61 and 25 % lower odds of having metabolic syndrome. Furthermore, individuals meeting both guidelines had the lowest odds of having metabolic syndrome (70 %), in part due to the additive interaction of performing both modes of exercise.

Conclusion

In this national sample, accelerometer-assessed physical activity and muscle strengthening activities were synergistically associated with metabolic syndrome.