High-Resolution 7T MR Imaging of the Trochlear Nerve.

BACKGROUND AND PURPOSE: The trochlear nerve has traditionally been difficult to identify on MR imaging. The advent of 7T MR imaging promises to greatly benefit visualization of small structures due to gains in the signal-to-noise ratio allowing improved spatial resolution. We investigated the utility of a clinically feasible ultra-high-resolution 7T MR imaging protocol for identification of the trochlear nerve, as well as assessment of normal trochlear nerve anatomy. MATERIALS AND METHODS: Coronal high-resolution 2D T2-weighted TSE images used in a 7T epilepsy protocol of 50 subjects at our institution were reviewed by 2 independent radiologists for visualization of the trochlear nerve at the nerve origin and cisternal, tentorial, and cavernous segments. The frequency of nerve visibility within these segments and their anatomy were documented, and disagreements were resolved by joint review. RESULTS: Of the 100 nerves reviewed in 50 subjects, at least 2 segments of the trochlear nerve from the brainstem to the cavernous sinus were identified in 100% of cases. The origins from the brainstem and cisternal segment were visible in 65% and 93% of nerves, respectively. The trochlear nerve was identified at the trochlear groove in 100% of cases and in the posterior wall of the cavernous sinus in 74% of cases. CONCLUSIONS: Coronal high-resolution 2D TSE at 7T reliably identified the trochlear nerve throughout its course and is a promising tool for imaging patients with suspected trochlear nerve pathology.

Trochlear cistern of the cavernous sinus: an anatomical study using magnetic resonance imaging.

PURPOSE: The present study aimed to explore the trochlear cistern (TC) of the cavernous sinus using magnetic resonance imaging (MRI). METHODS: Following conventional MRI examination, a total of 73 patients underwent the constructive interference steady-state (CISS) sequence in thin-sliced coronal sections. Moreover, three injected cadaver heads were dissected. RESULTS: In the cadaver specimens, the extent of the TC was difficult to identify on any dissected side. On the CISS images, the TC was identified in 98.6% on the right side and 94.5% on the left, while transmitting the trochlear nerve (TN) was identified in 83.6% on the right and 79.5% on the left. Most TNs were delineated as a single trunk, while duplication of the nerve was found in 3% of cases. The TC, commonly located inferior or inferolateral aspect of the oculomotor trigone. The size and extent of TC were highly variable. The TN location in the TC was also variable and was identified throughout the upper, middle, and lower parts of the TC. Moreover, relationships between the TC and Meckel's cave were highly variable. CONCLUSIONS: TC shows morphological variability. The coronal CISS sequence is useful for exploring TC and TN in clinical practices.

Segmental Imaging of the Trochlear Nerve: Anatomic and Pathologic Considerations.

BACKGROUND: The trochlear nerve (the fourth cranial nerve) is the only cranial nerve that arises from the dorsal aspect of the midbrain. The nerve has a lengthy course making it highly susceptible to injury. It is also the smallest cranial nerve and is often difficult to identify on neuroimaging. EVIDENCE ACQUISITION: High-resolution 3-dimensional skull base MRI allows for submillimeter isotropic acquisition and is optimal for cranial nerve evaluation. In this text, the detailed anatomy of the fourth cranial nerve applicable to imaging will be reviewed. RESULTS: Detailed anatomic knowledge of each segment of the trochlear nerve is necessary in patients with trochlear nerve palsy. A systematic approach to identification and assessment of each trochlear nerve segment is essential. Pathologic cases are provided for each segment. CONCLUSIONS: A segmental approach to high-resolution 3-dimensional MRI for the study of the trochlear nerve is suggested.

Anatomical variations and innervation patterns of the superior oblique muscle.

GOAL: The location and anatomical relationships of the superior oblique muscle make surgical intervention difficult. The aim of the present paper was therefore to supplement existing anatomical descriptions of this muscle. Its anatomical variability is particularly emphasized, including variations in muscle and tendon size and details of the innervation pattern. MATERIALS AND METHODS: The study was conducted on 78 orbits from 39 adult human cadavers of both sexes (18 males and 21 females). The roof and upper part of the medial and lateral walls of the orbit were carefully removed, which allowed the superior oblique muscle and trochlear nerve to be exposed along their entire course. Sihler's stain was applied to visualize the intramuscular distribution of the trochlear nerve. RESULTS: The length of the muscle between the origin and trochlea ranged from 37.8 to 56.5mm, the length of the tendinous expansion ranged from 16.3 to 22.8mm, and the width of the scleral insertion of the muscle's tendon ranged from 5.4 to 9.6mm. In two cadavers, accessory muscular slips connecting the levator palpebrae superioris muscle to the trochlea of the superior oblique muscle were present unilaterally. The distance from the level of the trochlea attachment to the anteriormost endings of the intramuscular branches varied from 17.2 to 21.5mm. CONCLUSIONS: The intramuscular nervous branches of the trochlear nerve form a tree-like pattern. Unexpected anatomical variations such as accessory muscular bands could be relevant during orbital imaging or surgeries.

Detailed anatomy of the trochlear nerve in the superior oblique muscle.

PURPOSE: The purpose of this study was to elucidate the detailed anatomy of the trochlear nerve in the superior oblique muscle (SOM) and the intramuscular innervation pattern using Sihler staining. METHODS: SOMs were dissected from their origin to the insertion in 28 eyes of 14 cadavers. The following distances were determined: from the SOM insertion to the trochlear, from the trochlear to the entry site of the anterior branch or posterior branch, and the widths of the main trunk and anterior and posterior branches. Sihler staining was then performed. RESULTS: The trochlear nerve traveled straight ahead medially and divided. Eighteen of 28 (64.3%) orbits showed two anterior and posterior branches, six (21.4%) showed three branches, and four (14.3%) showed no branching. The most distally located intramuscular nerve ending was observed at 62.4 ± 2.4% of the length of each muscle (35.8 mm from insertion when considering that the length of the SOM was 57.4 mm) and at 29.9 ± 3.2% of the length of each muscle (17.2 mm from the trochlear). Additionally, the length of the intramuscular arborization part was 9.4 ± 1.1% of the length of the SOM (5.4 mm when considering that the length of the SOM was 57.4 mm). Nonoverlap between two intramuscular arborizations of the nerve was detected in 20 of 28 cases (71.4%). Eight cases (28.6%) showed a definite overlap of two zones. CONCLUSIONS: This study provided a good understanding of the anatomy of the trochlear nerve in the SOM.

Análisis semántico y gramatical de los términos latinos de los ramos terminales del nervio nasociliar / Semantic and grammatical analysis of latin terms of the terminal branches of the nasociliary nerve

RESUMEN: La necesidad de unificar criterios respecto a los nombres de las estructuras anatómicas ha sido una permanente preocupación de los anatomistas del mundo, de tal manera que a partir de 1895 se inicia un proceso de estandarización y normalización de la terminología anatómica mundial. Se publica la Nomina Anatomica tratando de nominar las estructuras con un solo nombre en latín y se suprime los epónimos y homónimos. En la actualidad la Terminologia Anatomica sustituye a la Nomina Anatomica, con las mismas características, pero con la adición del término en el idioma de cada país. Sin embargo, persisten algunos errores desde la elaboración de la Nomina Anatomica y que se mantienen en Terminologia Anatomica, derivados tanto de la estructura gramatical latina, principalmente en el número y género, así como de la descripción de algunas estructuras anatómicas. Este es el caso de los ramos del nervio nasociliar, específicamente del ramo etmoidal anterior y del ramo infratroclear. Para el efecto se realizó una revisión de la descripción del nervio nasociliar y sus ramos terminales, se compararon entre sí y con los nombres que aparecen en la Terminologia Anatomica, para verificar que tanto la descripción como la construcción gramatical latina sean correctas. Se encontraron errores en la estructuración gramatical y jerárquica del ramo nasal interno, así como la supresión de los ramos palpebrales superior e inferior del nervio infratroclear, por lo que proponemos el cambio del término codificado con A14.2.01.031 a Ramus nasalis internus y la adición de los nombres Ramus palpebralis superior y Ramus palpebralis inferior.

SUMMARY: The need to unify criteria regarding the names of anatomical structures has been a permanent concern of anatomists worldwide. Therefore, and beginning in 1895 a standardization and normalization process of world anatomical terminology was initiated. The Nomina Anatomica is published in an attempt to name the structures with a single name in Latin and the eponyms and homonyms are deleted. Today the Terminologia Anatomica replaces the Nomina Anatomica, with the same characteristics, but with the addition of the term in the language of each country. Nevertheless, some errors persist from the Nomina Anatomica that remain in Terminologia Anatomica, derived from both the Latin grammatical structure, mainly in the number and gender, as well as the description of some anatomical structures. This is the case of the nasociliary nerve branches, specifically the anterior ethmoidal branch and the infratroclear branch. For this purpose, a review of the description of the nasociliary nerve and its terminal branches was made, they were compared between each other, and with the names that appear in the Terminologia Anatomica, to verify that both the description and the Latin grammatical construction are correct. Errors were found in the grammatical and hierarchical structure of the internal nasal branch, as well as the suppression of the upper and lower palpebral branches of the infratrochlear nerve. Therefore, we propose the change of the coded term with A14.2.01.031 to "Ramus nasalis internus" and the addition of the names "Ramus palpebralis superior" and "Ramus palpebralis inferior".

Innervation of Orbicularis Oculi by Trochlear Nerve: Word of Caution.

BACKGROUND: Neurosurgeons who operate in and around the pathway of the ocular nerves should have good knowledge of not only their normal anatomy but also their variations. CASE DESCRIPTION: During routine dissection of the orbits in an adult cadaver, an aberrant branch of the right trochlear nerve continued on to innervate the orbicularis oculi muscle. In this case, the trochlear nerve also provided a branch to the supratrochlear nerve. CONCLUSIONS: Surgeons who operate along the pathway of the trochlear nerve such as the cavernous sinus should be aware of such an anatomic variant in order to avoid unwanted complications such as weakness of the orbicularis oculi muscle.

The supraorbital region revisited: An anatomic exploration of the neuro-vascular bundle with regard to frontal migraine headache.

BACKGROUND: Recent findings on the pathogenesis of frontal migraine headache support, besides a central vasogenic cause, an alternative peripheral mechanism involving compressed craniofacial nerves. This is further supported by the efficiency of botulinum toxin injections as a new treatment option in frontal migraine headache patients. METHODS: The supraorbital regions of 22 alcohol-glycerine-embalmed facial halves of both sexes were dissected. Both the supratrochlear and supraorbital nerves (STN and SON, respectively) were identified, and their relationship with the corrugator supercilii muscle (CSM) was investigated by dissection and ultrasound. The course of both nerves was defined, and the interaction between the supraorbital artery (SOA) and SON was determined. RESULTS: We discovered a new possible compression point of the STN passing through the orbital septum and verified previously described compression points of both STN and SON. Osteofibrous channels used by the STN and SON were found constantly. We described the varying topography of the STN and CSM, the SON and CSM, and the SON and SOA. Further, we provide an algorithm for the ultrasound visualization of the supraorbital neurovascular bundle. CONCLUSION: Our data support the hypothesis of a peripheral mechanism for frontal migraine headache because of following potential irritation points: first, the CSM is constantly perforated by the SON and frequently by the STN; second, the topographic proximity between SOA and SON and the osteofibrous channels is used by the SON and STN; and third, the STN passes through the orbital septum.

Aberrant distribution of the trochlear nerve: A cadaveric study supported by immunohistochemistry.

The trochlear nerve is generally considered to be a purely motor nerve supplying one extraocular muscle, the superior oblique. In the current study, 28 orbits were dissected and in one orbit (3.6%), the trochlear nerve divided into two main branches. The medial branch followed the classical course, entered the superior oblique muscle and was presumed to be motor in function. However, before entering the muscle, it partially fused with the frontal nerve, and gave a bundle of nerve fibres to the frontal nerve. The lateral branch gave a communication to the frontal nerve, travelled along the lacrimal nerve, received a branch from the lacrimal nerve then penetrated the lacrimal gland. The lateral branch was presumed to be sensory. Paraffin sections from the two branches were stained using immunohistochemistry. The two branches had different nerve fibre populations and showed distinct differences in neurofilament proteins (NFP) immuno-labelling. While both branches showed intense labelling for NFP-H, the lateral branch showed no staining or faint staining for NFP-M and NFP-L respectively, but the medial branch showed moderate labelling for both the NFP-M and NFP-L. Staining for substance P, a marker for nociceptive fibres, showed intense staining in a subset of fibres in the lateral branch, but no staining in the medial branch. Calcitonin gene-related peptide labelling was evident in some axons and some Schwann cells in the medial branch but widespread, weak and fine granular in the lateral branch. These findings indicate that, in some individuals (3.6%), the trochlear nerve may contain motor and sensory fibres, suggesting inter-nuclear communication within the brainstem during embryogenesis or mixing of nerve fibres in their extra-axial pathways.

Fourth cranial nerve: surgical anatomy in the subtemporal transtentorial approach and in the pretemporal combined inter-intradural approach through the fronto-temporo-orbito-zygomatic craniotomy. A cadaveric study.

Despite the recent progress in surgical technology in the last decades, the surgical treatment of skull base lesions still remains a challenge. The purpose of this study was to assess the anatomy of the tentorial and cavernous segment of the fourth cranial nerve as it appears in two different surgical approaches to the skull base: subtemporal transtentorial approach and pretemporal fronto-orbito-zygomatic approach. Four human cadaveric fixed heads were used for the dissection. Using both sides of each cadaveric head, we made 16 dissections: 8 with subtemporal transtentorial technique and 8 with pretemporal fronto-orbito-zygomatic approach. The first segment that extends from the initial point of contact of the fourth cranial nerve with the tentorium (point Q) to its point of entry into its dural channel (point D) presents an average length of 13.5 mm with an extremely wide range and varying between 3.20 and 9.3 mm. The segment 2, which extends from point D to the point of entry into the lateral wall of the cavernous sinus, presents a lesser interindividual variability (mean 10.4 mm, range 15.1-5.9 mm). A precise knowledge of the surgical anatomy of the fourth cranial nerve and its neurovascular relationships is essential to safely approach. The recognition of some anatomical landmarks allows to treat pathologies located in regions of difficult surgical access even when there is an important subversion of the anatomy.

Topographic Relationship between the Supratrochlear Nerve and Corrugator Supercilii Muscle--Can This Anatomical Knowledge Improve the Response to Botulinum Toxin Injections in Chronic Migraine?

Chronic migraine has been related to the entrapment of the supratrochlear nerve within the corrugator supercilii muscle. Recently, research has shown that people who have undergone botulinum neurotoxin A injection in frontal regions reported disappearance or alleviation of their migraines. There have been numerous anatomical studies conducted on Caucasians revealing possible anatomical problems leading to migraine; on the other hand, relatively few anatomical studies have been conducted on Asians. Thus, the aim of the present study was to determine the topographic relationship between the supratrochlear nerve and corrugator supercilii muscle in the forehead that may be the cause of migraine. Fifty-eight hemifaces from Korean and Thai cadavers were used for this study. The supratrochlear nerve entered the corrugator supercilii muscle in every case. Type I, in which the supratrochlear nerve emerged separately from the supraorbital nerve at the medial one-third portion of the orbit, was observed in 69% (40/58) of cases. Type II, in which the supratrochlear nerve emerged from the orbit at the same location as the supraorbital nerve, was observed in 31% (18/58) of cases.

Morphological Characteristics of the Sphenoid Sinus and Endoscopic Localization of the Cavernous Sinus.

The aim of this study was to investigate the relationship between the morphological characteristics of the sphenoid sinus and endoscopic localization of the cavernous sinus (CS) using an extended endoscopic endonasal transsphenoidal approach. Thirty sides of CS in 15 adult cadaver heads were dissected to simulate the extended endoscopic endonasal transsphenoidal approach, and the morphology of the sphenoid sinus and anatomic structures of CS were observed. The opticocarotid recess (OCR), ophthalmomaxillary recess (V1V2R), and maxillomandibular recess (V2V3R) in the lateral wall of the sphenoid sinus were presented in 16 sides (53.3%), 6 sides (20%), and 4 sides (13.3%) of the 30 sides, respectively. OCR is a constant anatomic landmark in endoscopy and coincides with the anterior portion of the clinoidal triangle. The C-shaped internal carotid artery (ICA) in the lateral wall of the sphenoid sinus was presented in 11 sides (36.7%), the upper one-third of which corresponds to the middle portion of the clinoidal triangle, and the lower two-thirds of which correlates to the supratrochlear triangle, infratrochlear triangle, and ophthalmic nerve in CS, around which the medial, lateral, and anteroinferior interspaces are distributed. From a front-to-behind perspective, the C-shaped ICA consists of inferior horizontal segment, anterior vertical segment, clinoidal segment as well as partial subarachnoid segment of the ICA. OCR and C-shaped ICA in the lateral wall of the sphenoid sinus are the 2 reliable anatomic landmarks in the intraoperative location of the parasellar region of CS.

Microsurgical anatomy of the trochlear nerve.

The trochlear nerve is the cranial nerve with the longest intracranial course, but also the thinnest. It is the only nerve that arises from the dorsal surface of the brainstem and decussates in the superior medullary velum. After leaving the dorsal surface of the brainstem, it courses anterolaterally around the lateral surface of the brainstem and then passes anteriorly just beneath the free edge of the tentorium. It passes forward to enter the cavernous sinus, traverses the superior orbital fissure and terminates in the superior oblique muscle in the orbit. Because of its small diameter and its long course, the trochlear nerve can easily be injured during surgical procedures. Therefore, precise knowledge of its surgical anatomy and its neurovascular relationships is essential for approaching and removing complex lesions of the orbit and the middle and posterior fossae safely. This review describes the microsurgical anatomy of the trochlear nerve and is illustrated with pictures involving the nerve and its surrounding connective and neurovascular structures.

ANATOMICAL STUDY OF CRANIAL NERVE EMERGENCE AND SKULL FORAMINA IN THE HORSE USING MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY.

For accurate interpretation of magnetic resonance (MR) images of the equine brain, knowledge of the normal cross-sectional anatomy of the brain and associated structures (such as the cranial nerves) is essential. The purpose of this prospective cadaver study was to describe and compare MRI and computed tomography (CT) anatomy of cranial nerves' origins and associated skull foramina in a sample of five horses. All horses were presented for euthanasia for reasons unrelated to the head. Heads were collected posteuthanasia and T2-weighted MR images were obtained in the transverse, sagittal, and dorsal planes. Thin-slice MR sequences were also acquired using transverse 3D-CISS sequences that allowed mutliplanar reformatting. Transverse thin-slice CT images were acquired and multiplanar reformatting was used to create comparative images. Magnetic resonance imaging consistently allowed visualization of cranial nerves II, V, VII, VIII, and XII in all horses. The cranial nerves III, IV, and VI were identifiable as a group despite difficulties in identification of individual nerves. The group of cranial nerves IX, X, and XI were identified in 4/5 horses although the region where they exited the skull was identified in all cases. The course of nerves II and V could be followed on several slices and the main divisions of cranial nerve V could be distinguished in all cases. In conclusion, CT allowed clear visualization of the skull foramina and occasionally the nerves themselves, facilitating identification of the nerves for comparison with MRI images.

Whole courses of the oculomotor, trochlear, and abducens nerves, identified in sectioned images and surface models.

In medicine, the neuroanatomy of the oculomotor (III), trochlear (IV), and abducens nerves (VI) is learned essentially by cadaver dissection, histological specimens, and MRI. However, these methods have many limitations and it is necessary to compensate for the insufficiencies of previous methods. The aim of this research was to present sectioned images and surface models that allow the whole courses of III, IV, and VI and circumjacent structures to be observed in detail. To achieve this, the structures of whole courses of III, IV, and VI were traced on the sectioned images, and surface models of the structures were reconstructed. As a result, nucleus of III, Edinger-Westphal nucleus, nucleus of IV, and nucleus of VI and their fibers were identified on brainstem in the sectioned images. In the sectioned images, III, IV, and VI passed both sides of the cavernous sinus and entered at the orbit through the superior orbital fissure. In the sectioned images, III, IV, and VI innervated extraocular muscles in orbit. In surface models, the whole courses of III, IV, and VI and circumjacent structures could be explored freely three-dimensionally. The greatest advantage of the sectioned images was that they allowed the whole courses of III, IV, and VI and circumjacent structures to be observed as real colored in an unbroken line. In addition, the surface models allowed the stereoscopic shapes and positions of III, IV, and VI to be comprehended. The sectioned images and surface models could be applied for medical education purposes or training tools. All data generated during this study is available free of charge at anatomy.dongguk.ac.kr/cn/.

Axial scan orientation and the tibial tubercle-trochlear groove distance: error analysis and correction.

OBJECTIVE: The tibial tubercle (TT)-trochlear groove (TG) distance is an important metric in the assessment of patellofemoral dysfunction and is routinely measured on axial MRI and CT. This study examines error in measurements of the TT-TG distance related to variance in axial MRI scan orientation. SUBJECTS AND METHODS: Isotropic 3D turbo spin-echo MRI of the extended knee was performed in 12 healthy subjects. The z-axis of the scanner defines the perpendicular to a routine axial plane, and the anatomic axial plane is parallel to the knee joint. Isotropic MRI was reformatted into routine and anatomic axial planes and in axial planes simulating 5° of femoral adduction and abduction relative to the anatomic plane. A method for correcting the TT-TG distance to account for variable axial scan orientation is presented. RESULTS: Five degrees of simulated femoral abduction is associated with a mean increase in the TT-TG distance of 38% (SD = 17%), whereas 5° of simulated femoral adduction is associated with a mean decrease in the TT-TG distance of 51% (SD = 39%). The average deviation of the routine axial plane from the anatomic axial plane was 5.0° abduction (SD = 2.3°). The simplest correction method reduced the mean discrepancy in the observed TT-TG distance by 68% and 72% in simulated femoral abduction and adduction, respectively. CONCLUSION: The TT-TG distance is sensitive to small changes in femoral alignment and should be interpreted with caution if axial image acquisition is not standardized. Knowing the vertical separation of the TT from the TG facilitates a simplified correction of the TT-TG distance, which is as effective as more complex corrections.

Anatomy of the tentorial segment of the trochlear nerve in reference to its preservation during surgery for skull base lesions.

BACKGROUND: In traditional descriptions of the intracranial course of the trochlear nerve, the tentorial segment of this nerve has not been described. This segment assumes importance as it is at risk of injury during tentorial sectioning in skull base surgery. In the present study, the tentorial segment of the trochlear nerve was studied. METHODS: 30 cadaver sides were studied and the following parameters were measured: the parts and lengths of the tentorial segments of the fourth nerve; the distances between the point where the third nerve came into contact with the tentorial edge and (a) the point where fourth nerve first touched the tentorium and (b) the point where fourth nerve pierced the tentorial dura; and the transverse separation between the fourth nerve and the gasserian ganglion. RESULTS: The tentorial part of the fourth nerve was found to have two segments: segment 1-from the point where the fourth nerve first came into contact with the tentorial edge to the point where it pierced the tentorium; segment 2-from the point of tentorial piercing to the point where the fourth nerve entered the cavernous sinus. The mean distance between the third nerve and the point of piercing along the tentorial edge was 9.9 ± 2.7 mm (5.29-15.32). CONCLUSIONS: The most consistent and reliable anatomical landmark for avoiding injury to the fourth nerve was the point of contact between the third nerve and the tentorial edge. An incision 15 mm posterior to this point along the tentorial edge would avoid injury to the fourth nerve.

Supratrochlear and supraorbital nerves: an anatomical study and applications in the head and neck area.

BACKGROUND: This article elucidates the anatomical details of the course and territory of the supraorbital (SO) and supratrochlear (ST) nerves. Possible applications of the SO and ST nerves for sensory nerve transfer are also examined. METHODS: The dissection of 3 fresh cadaver heads (6 hemifaces) was performed. In each hemiface, the ST and SO nerves were identified. The following data were recorded: 1) number of branches, 2) skin boundaries, 3) communicative branches, and 4) branch length. The feasibility of specific nerve-transfer procedures was also examined. RESULTS: In 4 hemifaces the SO nerve exited from the SO notch and in 2 hemifaces from the SO foramen. The position was lateral to the midline, with a mean distance of 1.93 cm. In all dissections, a maximum of 4 SO branches (range 2-4) were identified. The ST nerve exited the orbital rim medial to the SO nerve, and lateral to the midline with a mean distance of 0.866 cm. The mean distance between the SO and ST nerves at the level of the SO rim was 1.06 cm. In 5 of 6 hemifaces, several sub-branches emerged from the main trunk of the ST nerve. In 1 hemiface the ST nerve was divided in 2 main branches. CONCLUSIONS: The data presented in the current study are in agreement with previous anatomical studies. Both ST and SO nerves can be used as sensory nerve donors in the head and neck area for numerous expanding applications.