A different technique for sutureless coronary bypass grafting.

Introduction: Many coronary anastomotic devices have been designed to replace manual stitching in coronary surgery; however, interestingly, none of them became widespread. Our aim was to work out an easy and fast endoluminal vessel-to-vessel stent bridge distal anastomotic technique. Materials and methods: Ten coronary arteries of eight fresh human hearts were used in this study. The anastomosis was performed with the implantation of a graft vessel into the lumen of the coronary artery by performing stent fixation. The technique is described and photo documented in detail. The durability and the conductibility of the anastomosis were examined with intraluminal endoscopy, functional streaming test, and a coloring of the vessels. Results: The anastomosis had great results in all cases. Obstruction, dissection, or dislocation of the vessels was not observable. Conclusions: This study confirmed the ex-vivo feasibility of the described technique. This method can be an easy, fast, and reliable method applied in the endoscopic distal coronary artery anastomosis surgery. The development of stents adapted to this method and the in-vivo testing of this technique are necessary for the future.

Introducing the craniocervical Y-ligament.

PURPOSE: We examined the accessory atlantoaxial ligaments and found them to be a part of a complex ligamentous structure, which we named craniocervical Y-ligament with respect to its shape. METHODS: The ligaments of the upper cervical spine were dissected in ten Thiel embalmed human cadavers. Origin and attachment of the Y-ligament were described and a detailed photo and video-documentation was carried out with the head in the neutral position, flexion, extension and rotation to study the ligament during these movements. RESULTS: The Y-ligaments were found to be paired and symmetric in all specimens. The shape of the ligament is similar to an Y, its lateral arm connecting the atlas to the axis, its medial arm connecting the occipital bone to the axis, fusing with the two main ligaments, the alar and transverse ligaments. The lateral arm of the Y-ligament was found to be analogous to the accessory atlantoaxial ligament. During cervical flexion, both arms of the Y-ligament became taut while extension made the Y-ligaments relaxed. During rotation both Y-ligaments became taut, moving in the opposite directions in the sagittal plane while following the gliding movements of the lateral masses of the atlas. CONCLUSIONS: The craniocervical Y-ligament is a complex ligamentous structure and has a constant anatomy. Because of its shape and special arrangement, it probably plays a role in limiting both atlantooccipital and atlantoaxial movements. Acknowledgement of this ligamentous structure will help understand upper cervical stability. The present study should serve as a basis for future biomechanical and radiological studies.

Primary Obstruction of the Foramen of Luschka: Anatomy, Histology, and Clinical Significance.

BACKGROUND: The foramen of Luschka is a natural aperture between the fourth ventricle and the subarachnoid space at the cerebellopontine angle. Membranous closure of this foramen is referred to as primary obstruction. Available information about this variant and its role in the development of the cysts of the posterior fossa is contradictory. METHODS: The macroscopic and histologic features of the obstructed foramina were examined in 61 formalin-fixed human brains (122 foramina). Three rhomboid lips of various sizes with lateral recess were used for comparison. Five postoperative cases of diverticulum of the foramen of Luschka were included in this study, with 1 case presented in detail to illustrate anatomic and histologic findings. RESULTS: Primary obstruction was present in 11 of 122 cases. In 1 case, an enlarged rigid pouch with a thick wall was found. The wall of the membrane in primary obstruction and the rhomboid lip were composed of an inner ependymal, a middle glial, and an outer leptomeningeal layer. CONCLUSIONS: The rhomboid lip is a remnant of the roof of the fourth ventricle. Imperforation of the foramen of Luschka results in a pouch in the cerebellopontine angle that contains choroid plexus (Bochdalek's flower basket) and communicates with the fourth ventricle. This pouch has the potential to grow to a diverticulum and cause clinical symptoms. Based on our clinical observations, detailed radiologic and surgical-anatomic criteria were proposed to support the differential diagnosis of a diverticulum of the foramen of Luschka. Treatment strategies were also suggested.

Morphometry and microsurgical anatomy of Bochdalek's flower basket and the related structures of the cerebellopontine angle.

BACKGROUND: Bochdalek's flower basket (Bfb) is the distal part of the horizontal segment of the fourth ventricle's choroid plexus protruding through the lateral aperture (foramen of Luschka). The microsurgical anatomy of the cerebellopontine angle, fourth ventricle and its inner choroid plexus is well described in the literature, but only one radiological study has investigated the Bfb so far. The goal of the present study was to give an extensive morphometric analysis of the Bfb for the first time and discuss the surgically relevant anatomical aspects. METHOD: Forty-two formalin-fixed human brains (84 cerebellopontine angles) were involved in this study. Photomicrographs with scale bars were taken in every step of dissection to perform further measurements with Fiji software. The lengths and widths of the Bfb, rhomboid lip and lateral aperture of the fourth ventricle as well as the related neurovascular and arachnoid structures were measured. The areas of two sides were compared with paired t-tests using R software. Significance level was set at p < 0.05. RESULTS: Protruding choroid plexus was present in 77 cases (91.66%). In 6 cases (7.14%), the Bfb was totally covered by the rhomboid lip, and in one case (1.19%), it was absent. The mean width of the Bfb was 6.618 mm (2-14 mm), the mean height 5.658 mm (1.5-14 mm) and mean area 25.80 mm2 (3.07-109.83 mm2). There was no statistically significant difference between the two sides (p = 0.1744). The Bfb was in contact with 20 AICAs (23.80%), 6 PICAs (7.14%) and 39 vestibulocochlear nerves (46.42%). Arachnoid trabecules, connecting the lower cranial nerves to the Bfb or rhomboid lip, were found in 57 cases (67.85%). CONCLUSIONS: The Bfb is an important landmark during various surgical procedures. Detailed morphology, dimensions and relations to the surrounding neurovascular structures are described in this study. These data are essential for surgeons operating in this region.

Endoscopic approach-routes in the posterior fossa cisterns through the retrosigmoid keyhole craniotomy: an anatomical study.

Endoscopy in cerebellopontine angle surgery is an increasingly used technique. Despite of its advantages, the shortcomings arising from the complex anatomy of the posterior fossa are still preventing its widespread use. To overcome these drawbacks, the goal of this study was to define the anatomy of different endoscopic approaches through the retrosigmoid craniotomy and their limitations by surgical windows. Anatomical dissections were performed on 25 fresh human cadavers to describe the main approach-routes. Surgical windows are spaces surrounded by neurovascular structures acting as a natural frame and providing access to deeper structures. The approach-routes are trajectories starting at the craniotomy and pointing to the lesion, passing through certain windows. Twelve different windows could be identified along four endoscopic approach-routes. The superior route provides access to the structures of the upper pons, lower mesencephalon, and the upper neurovascular complex through the suprameatal, superior cerebellar, and infratrigeminal windows. The supratentorial route leads to the basilar tip and some of the suprasellar structures via the ipsi- and contralateral oculomotor and dorsum sellae windows. The central endoscopic route provides access to the middle pons and the middle neurovascular complex through the inframeatal, AICA, and basilar windows. The inferior endoscopic route is the pathway to the medulla oblongata and the lower neurovascular complex through the accessory, hypoglossal, and foramen magnum windows. The anatomy and limitations of each surgical windows were described in detail. These informations are essential for safe application of endoscopy in posterior fossa surgery through the retrosigmoid approach.

Experimental transapical endoscopic ventricular visualization and mitral repair.

BACKGROUND: An increasing number of experimental beating heart animal studies describe simple transapical mitral valve repairs based on the direct endoscopic visualization of the left ventricle. The aim of our human cadaveric study was to develop a method for more complex transapical endoscopic procedures by on-pump heart operations. MATERIALS AND METHODS: After preparation of 20 human fresh cadavers, a standard left anterolateral minithoracotomy was performed in the fifth intercostal space and the pericardium was entered. A rigid 0 degree endoscope and the instruments were introduced through a silicon apical port. To restore the natural form of the left heart, CO2 was insufflated. To test the mitral valve competence, the left ventricle was pressure-injected with saline after each step. After transecting the chords of the A2 segment of the anterior mitral leaflet before the experimental mitral valve repair, the tendinous chord was replaced using an especially designed clip chord. The second part of the experiment consisted of a segmental excision of the P2 segment of the posterior mitral leaflet followed by a standard valvuloplasty and suture annuloplasty. RESULTS: With the help of the described transapical endoscopic mitral valve repair technique, we gained direct visual information of the coaptation line of the mitral leaflets as well as the anatomy and function of the subvalvular apparatus. Using intracardiac imaging, we could perform successful transapical complex mitral repair in each case. CONCLUSION: The minimally invasive transapical endoscopic method has the potential to offer advantages for on-pump mitral valve repair procedures even in complex mitral valve repair cases.

Comparative endoscopic anatomic description of the mitral valvular complex: a cadaveric study.

BACKGROUND: We compared the aortic, left atrial, and apical approaches to visualize the mitral valve with the goal to investigate the endoscopic anatomy and give exact step-by-step descriptions of these views. MATERIALS AND METHODS: The mitral valvular complex of human cadaveric fresh hearts was investigated from three approaches using 0, 30, and 70 degrees rigid endoscopic optics. In 30 cases after the removal of the hearts, the endoscopes were introduced directly into the aortic root through an aortotomy, left atrium through a standard atriotomy, and apex of the heart through a transmural incision. In 10 cases, the in situ visualization was performed using standard surgical approaches, such as partial upper ministernotomy, right and left minithoracotomy. The investigation was performed first with the mitral valve open, then the left ventricle was filled with saline, and the valve was closed by clamping the aorta. RESULTS: For the visualization of ventricular surfaces of the mitral leaflets and the subvalvular apparatus, the apical approach was most optimal. The aortic approach had limitations at the posterior leaflet. Using the atrial approach, we did not obtain any direct visual information about the subvalvular apparatus with the valve closed. The atrial surfaces of the leaflets were best visible using both the atrial and apical approaches with the mitral valve open. In the case of a closed valve, the apical approach did not allow for an investigation of the atrial surfaces. The aortic approach was useful to visualize the atrial surface of the posterior leaflet with an opened valve. CONCLUSION: In mitral valve repairs through the left atrium, an additional aortic or apical view could be useful to obtain functional information about the subvalvular apparatus by the sealing probe.

Applied anatomy of a minimally invasive muscle-splitting approach to posterior C1-C2 fusion: an anatomical feasibility study.

PURPOSE: To describe the applied anatomy of a minimally invasive muscle-splitting approach used to reach the posterior aspect of the C1-C2 complex. Atlantoaxial fusion using a midline posterior approach and polyaxial screw and rod system is widely used. Although minimally invasive variations of this technique have been recently reported, the complex applied anatomy of these approaches has not been described. The C1-C2 complex represents an unique challenge because of its bony and vascular anatomy. In this study, the applied anatomy and feasibility of this technique are examined on cadavers. METHODS: The microsurgical anatomy of the upper cervical spine is examined on a formalin-fixed and on a fresh cadaver. The muscle-splitting approach is performed on 12 fresh cadavers using this technique. RESULTS: The minimally invasive muscle-splitting approach is described in detail. Relevant anatomy and bony landmarks that aid screw placement in C1 and C2 could be well visualized. Using this approach, we were able to reach the lateral mass of the atlas and the inferior articular process and pars interarticularis of the axis in all of the nine cadavers. We placed mini polyaxial screws in C1 lateral mass and C2 pars interarticularis in four cadavers according to the technique described by Harms and Melcher. CONCLUSIONS: Using this approach, it was possible to reach the posterior aspect of C1 and C2; the relevant anatomy needed to perform a C1-C2 fusion could be well visualized.

Intraosseous territory of the facial artery in the maxilla and anterior mandible: implications for allotransplantation.

AIM: The aim of this anatomical study was to define the intraosseous vascular territory of the facial artery. The clinical issue is whether ipsilateral facial artery anastomosis will guarantee blood supply to the ipsi- and contralateral mandibular symphyses and maxillae in allotransplantation. MATERIAL AND METHODS: Of 10 human cadaveric heads, the left facial artery was injected with a positive contrast agent. The maxillae and mandibular symphyses were investigated with cone-beam computed tomography (CBCT). RESULTS: Each ipsilateral maxilla and mandibular bone segment showed contrast medium in the intraosseous vessels. In 50% of cases, this was also the case on the contralateral side of the maxilla and anterior mandible. CONCLUSIONS: The maxillae and the mandibular symphyses receive ipsilateral blood supply from the facial artery and, in 50% of cases, also from the contralateral facial artery. Internal maxillary artery anastomosis is not required for a vascularized maxillary bone flap. Additionally, involvement of the submental artery is not needed for a mandibular symphyseal bone flap.

Histamine and H1 -histamine receptors faster venous circulation.

The study has analysed the action of histamine in the rabbit venous system and evaluated its potential role in contraction during increased venous pressure. We have found that a great variety exists in histamine sensitivity and H(1) -histamine receptor expression in various types of rabbit veins. Veins of the extremities (saphenous vein, femoral vein, axillary vein) and abdomen (common iliac vein, inferior vena cava) responded to histamine by a prominent, concentration-dependent force generation, whereas great thoracic veins (subclavian vein, superior vena cavas, intrathoracic part of inferior vena cava) and a pelvic vein (external iliac vein) exhibited slight sensitivity to exogenous histamine. The lack of reactivity to histamine was not due to increased activity of nitric oxide synthase (NOS) or heme oxygenase-1. H(1) -histamine receptor expression of veins correlated well with the histamine-induced contractions. Voltage-dependent calcium channels mediated mainly the histamine-induced force generation of saphenous vein, whereas it did not act in the inferior vena cava. In contrast, the receptor-operated channels were not involved in this response in either vein. Tyrosine phosphorylation occurred markedly in response to histamine in the saphenous vein, but not in the inferior vena cava. Histamine induced a prominent ρ kinase activation in both vessels. Protein kinase C and mitogen-activated protein kinase (MAPK) were not implicated in the histamine-induced intracellular calcium sensitization. Importantly, transient clamping of the femoral vein in animals caused a short-term constriction, which was inhibited by H(1) -histamine receptor antagonist in vivo. Furthermore, a significantly greater histamine immunopositivity was detected in veins after stretching compared to the resting state. We conclude that histamine receptor density adapts to the actual requirements of the circulation, and histamine liberated by the venous wall during increased venous pressure contributes to the contraction of vessels, providing a force for the venous return.

[Excision of the calcified mitral valve with ultrasound scalpel]. / A meszes mitralis billentyu sebészi kimetszése ultrahangvágóval.

Mitral valve excision using ultrasound device has not been a routine procedure yet. We used an ultrasonic scalpel for the excision of the calcified mitral valves, which shorten operation time. Further, this technique permits an excision of the valve without applying traction or elevation of the valve from the level of the annulus. This method was first tested on twenty fresh porcine hearts. Subsequently, this technique was carried out with very good results in 15 consecutive patients with calcified or scarred, and distorted mitral valves. Histological samples were taken from the excised human and porcine valves. In porcine histological specimens the destructive effect of the ultrasonic scalpel was measured of an average of 0.7 mm (minimum 0.5 mms, maximum 0.8 mms). However, in the human heart, this effect was an average of 1.1 mms (minimum 0.6 mms, maximum 2.2 mms). There were no early or late complications observed in any case. The authors recommend this technique for excision of calcified mitral valves in cardiac surgery.

Surgical anatomy of the cochlea for cochlear implantation.

The anatomy of the cochlea was investigated to obtain precise data for surgical cochlear implantation. The aim of this study has been to find the optimal site for cochleostomy, to determine the course of the basal turn and to define the relationship of the cochlea to the middle ear. Our study is the first to depict the cochlea in a classical coordinate system, to compare the anatomical situation to the surgical approaches, and, consequently, to offer firm anatomical basis for minimal invasive intervention. Thirty-five macerated temporal bones of otologically healthy individuals were used to study the surgical anatomy of the cochlea. The cochlea could be divided into three portions: promontorial, muscular and geniculo-tegmental, respectively. In the promontorial part, the basal turn has a characteristic turning around its own axis which is also indicated by the shifting with the bony spiral Lamina. In addition to the basal turn, a small part of the second and third turns of the cochlea can be also revealed behind the promontory. The most superficial part of the cochlea forming the promontory is positioned behind the Jacobson's canal providing an optimal approach for cochleostomy. The geniculo-tegmental portion of the cochlea is almost as large as the promontorial part tying immediately under the tegmen tympani. This area is accessible only from the top using a transtemporal supralabyrinthine approach. The promontorial and muscular portions can be investigated from two directions: through the facial recess and through the external acoustic meatus.

Hand perfusion with 99mTc-HSA in patients expecting to undergo coronary bypass surgery: elaboration of a new complex diagnostic protocol for the safe removal of a radial artery graft.

BACKGROUND: The Allen test is used worldwide for radial artery graft removal. The postoperative examination of our patients' hand function and circulation proved that beside the transient neurological complications chronic hand circulatory disorders may arise. AIM: To develop a non-invasive method suitable for an objective evaluation of the hand's circulation to make it possible to use radial arteries safely for the revascularization of coronary arteries. METHODS: We examined 35 patients. After selective compression of the radial and ulnar arteries of both hands, we injected 400 MBq (99m)Tc-HSA intravenously and acquired 240 images, each of 1 s. After 30 s we released the ulnar artery first, and after 120 s the radial artery, too. Then computer analysis was performed. RESULTS: The patients could be divided into two groups. In the majority of them, releasing only the ulnar artery resulted in a good circulation of the fingers. It meant that the time-activity curve rapidly reached its maximum, and the activity did not change even after releasing the radial artery. In a smaller proportion of the patients the activity of the fingers increased only slowly, and did not reach a plateau even after 30 s. Following the release of the radial artery a further increase in the activity could be observed. We assume that the latter patient group is at risk of consequent circulatory disorder of the fingers after the removal of the radial artery, whereas in the former group the artery could be removed safely. CONCLUSIONS: Hand perfusion with (99m)Tc-HSA is useful in patients selected for coronary bypass operations, so we recommend the introduction of this method as a routine examination before the removal of the radial artery in patients with an abnormal Allen test.

Development of the protympanum.

The protympanum, the only opening of the tympanic cavity, has enormous significance in the pathogenesis of middle ear inflammation. In our study, we analyzed 70 macerated temporal bones stereomicroscopically to understand the development of the protympanum. Details of this embryonic process were attained using histological sections made in frontal and horizontal planes. In contrast to recent descriptions, the present work reveals that almost the entire protympanum develops from different processes of the petrous bone. The tympanic bone takes part in forming only the posterior border of the lateral wall of the protympanum. Consequently the tympanic plate, which forms the inferior half of the mandibular fossa, is formed by two anlages. The anterosuperior quarter is formed by the petrous bone and the remainder by the tympanic bone. The main structures of the medial wall of the protympanum are the carotid canal with the internal carotid artery (ICA). The carotid canal starts to develop as two laminae of the petrous bone in the 18th fetal week. In cases of incomplete closure of these laminae the carotid canal occupies dehiscences increasing the danger of injury to the ICA. The presence of the ICA is necessary for the development of the carotid canal. If the artery takes an aberrant pathway in the tympanic cavity, or is absent, there is no sign of the carotid canal.

Development and surgical anatomy of the round window niche.

The round window niche is a bony pouch of the tympanic cavity and clinically frequently explored, therefore its topography has fundamental impact on microsurgery. A total of 783 macerated and formalin-fixed temporal bones were used to study the normal anatomy of the round window and its development. The ossification of the niche starts in the 16th fetal week and is complete at birth. A process of the otic capsule, called the cartilage bar, forms the inferior wall of the round window niche. The anterior and superior walls of the niche form by intramembranous ossification, whereas the posterior and inferior walls predominantly form by enchondral ossification. The uneven growth of different walls of the round window niche can alter the shape of the entrance, which results in eight different types of niches: extremely narrow, descending tegmen, anterior septum, bony membrane, open fundus, exostosis, jugular dome and trabeculae.

Development of the anterior chordal canal.

Resent advances have led to the reexamination of the intraosseous pathway of the chorda tympani a few years ago and they stated that the nerve never enters the mandibular fossa and its exit the skull base in the sphenopetrosal fissure. In our report, 58 temporal bones were investigated after maceration and formalin fixation in order to understand the development of the anterior chordal canal. Our study revealed that the chorda tympani leaves the tympanic cavity through the tympanosquamosal fissure before formation of the anterior chordal canal of Huguier. This canal is situated parallel to and in front of the musculotubal canal and formed by the processus inferior tegminis tympani and the sphenoid bone between the second and fifth years of age. Prior to the age of 2, only the exit of the bony canal exists which is gradually followed by the appearance of a groove in the growing processus inferior tegminis tympani. The borders of the groove elevate and develop to upper and lower plates which lengthen with similar plates of the sphenoid bone, completing the anterior chordal canal by the fifth postnatal year. The entrance of the canal develops above the petrotympanic fissure and similar to the canal itself, it is also completely formed in the fifth year. In case of an incomplete development the anterior chordal canal remains partially opened laterally which might allow the head of the mandibula to effect the chorda tympani mechanically causing Costen's syndrome.

The clinical anatomy of the sinus node artery.

BACKGROUND: Our basic aim was to describe the topographic relation between the sinus node artery and the superior posterior border of the interatrial septum with regard to the sinus node dysfunction that follows the superior transseptal approach to the mitral valve. METHODS: During our study 50 human hearts without previous pathologic alterations were analyzed. The position of the sinus node and the course of the sinus node artery were investigated. For identification of the origin of the artery, selective coronary angiograms were performed. The course of sinus node artery and its topographic relation to the interatrial septum was identified by the dry dissections of the hearts. Based on histologic and dry dissected specimens the exact position of the sinus node was determined. RESULTS: We found that the sinus node artery originates from the right coronary artery in 66% of examined cases and from the left coronary artery in 34% of cases. The sinus node artery crosses the superior posterior border of the interatrial septum in 54% of cases. CONCLUSIONS: Our results were compared with clinical studies focusing the incidence of the sinus rhythm disturbance after the superior transseptal approach. The incidence of rhythm disturbance varies from 52% to 60% of cases. Comparing our morphologic and clinical results we can state that the risk for intraoperative damage to the sinus node artery during the superior transseptal approach to the mitral valve is high.

[Biportal neuroendoscopy of the prepontine cisterns]. / A praepontin ciszternák biportalis neuroendoszkópiája.

INTRODUCTION: While bi- or multiportal approaches have been adopted in different fields of surgery including abdominal and spine surgery, the uniportal access into the skull is a traditional principle in neurosurgery. In this preclinical cadaver study the authors developed combinations of biportal endoneurosurgical dissections in the prepontine subarachnoid space to test the safety of this technique. METHODS: In 34 fresh post-mortem adult human cadavers and 14 formaldehyde-fixed adult human head specimen a total of 48 biportal endoscopical dissections were carried out. 0 degree, 30 degrees, and 70 degrees lens scopes with a diameter of 1.7 and 4.2 mm and trochars with a diameter of 5.0 to 6.5 mm were used. RESULTS: Six different endoscopic routes to the prepontine region and a total of 10 different combinations of this approaches could be described. Useful and safe biportal combinations were: 1. supraorbital on both sides, 2. supraorbital combined with ipsilateral anterior subtemporal, 3. supraorbital combined with contralateral anterior subtemporal, 4. supraorbital combined with ipsilateral posterior subtemporal, 5. supraorbital combined with ipsilateral frontal interhemispheric, 6. supraorbital combined with contralateral frontal interhemispheric, 7. anterior subtemporal combined with ipsilateral frontal interhemispheric, 8. anterior subtemporal combined with contralateral frontal interhemispheric. CONCLUSION: The biportal endomicrosurgical strategy offered effective and safe dissections within the prepontine subarachnoid space.

Topographic microsurgical anatomy of the paraclinoid carotid artery.

In this publication, the authors describe the microanatomic topography of the entire paraclinoid area with respect to the paraclinoid segment of the internal carotid artery and its surrounding anatomical structures. Special attention was given to the borders of the paraclinoid area, cavernous sinus, arterial vessels, and cranial nerves passing through the region. The paraclinoid region was defined as a pyramid-formed space formed by the dural covering of the anterior clinoid process. The superior border is formed by the continuity of the anterior petroclinoid fold, anteriorly on the superior surface of the anterior clinoid process and medially in the direction of the diaphragma sellae. This dural sheet encircles the internal carotid artery and forms the so-called distal dural ring of the internal carotid artery. The medial border of the paraclinoid region is formed by the body of the sphenoid bone and the adjacent periosteal sheet. The inferior border is formed by a fibrous plate between the middle and anterior clinoid processes. This so-called proximal dural ring separates the venous compartments of the cavernous area from the paraclinoid area. The lateral border is formed by the lateral surface of the anterior clinoid process with its dural covering. The arterial supply of this region is provided by branches of the intracavernous carotid segment and the ophthalmic artery. The important nerves in close vicinity to the paraclinoidal area are the optic and the oculomotor nerves. Understanding and knowledge of the topographic anatomy of the paraclinoid area is essential for microsurgical exposure of this region.