Adult Cadaveric Heads Research Articles

Endoscopic endonasal transclival approach to the ventral brainstem: Radiologic, anatomic feasibility and nuances, surgical limitations and future directions

The endoscopic endonasal transclival approach (EETA) is less invasive than traditional open approaches; however, there is currently limited data on the pre-operative features that may predict success of the EETA. Surgical landmarks and exposure of the EETA and expanded EETA are assessed. We retrospectively measured multiple anatomic features in 154 adult dry skulls, 22 C1 and C2 dry bone vertebrae, and 500 paranasal sinus computed tomography (CT) scans. We also dissected 13 formalin-fixed, silicone-injected adult cadaveric heads. Relevant qualitative and quantitative data were obtained with CT (n = 10) and cadaveric dissection (n = 13). They are expressed as mean (SD), as appropriate and compared with unpaired t tests. Categorical variables were compared with χ2 tests. We determined the prevalence of clival and sphenoid sinus anatomic variations and assessed potential exposure of the craniovertebral region, based on the relative position of the nasal bone tip, posterior point of the hard palate, and their relation to the position of C1 and C2. Depending on anatomic features, EETA should allow visualization of the ventral brainstem. The mean (SD) dimensions of the surgical window for EETA were 43.2 (5.1) × 18.3 (1.1) mm, in the craniocaudad and horizontal dimensions, respectively. The craniocaudad dimension enlarged to 60.2 (4.7) mm with expanded EETA. The EETA allowed satisfactory exposure for odontoid and C1 anterior arch resection (expanded EETA) in all specimens, regardless of the orientation of the palate. The combination of preoperative radiographic assessment and intraoperative considerations allows safe and effective application and facilitate selection of the most appropriate approach.

Anatomical Study of the Posterior Auricular Branch of the Facial Nerve: Application to Parotid Surgery.

The posterior auricular nerve (PAN) is the first branch of the facial nerve after it leaves the stylomastoid foramen. The literature describing the anatomy of the PAN is very sparse. Therefore, the purpose of this study was to clarify the detailed anatomical features of the PAN and consider its clinical and surgical applications. The authors examined 10 sides from 6 fresh frozen adult cadaveric Caucasian heads. The PAN was observed as the first branch of the facial nerve in all specimens. During the dissection of the PAN, the posterior auricular artery was constantly near the PAN. Moreover, the PAN was located under the investing layer of deep cervical facia covering the sternocleidomastoid and mastoid process in all specimens. The diameter of the PAN was 0.82 ± 0.21 mm (range from 0.55 to 1.21). The distance from the stylomastoid foramen to where the PAN branched from the facial nerve was 0.40 ± 1.25 mm (range from 0 to 4.35). The distance from the location of this branching point of the PAN to the entering point of the PAN to any muscles was 28.03 ± 5.51 mm (range from 19.71 to 38.75). Understanding the anatomical features of the PAN is essential for performing surgical procedures in this region.

Anatomic Study of Endoscopic Transnasal Approach to Petrous Apex

With the development of Neurosurgery technology, there has been a qualitative leap forward with the appearance of microanatomy, which makes the deep brain tumors which were hard to be achieved in the past, and effectively reduces the mortality of patients. Petrous apex is a cone-shaped part of the anteromedial part of the temporal bone, which is deep. It has been a challenging area for surgical anatomy for a long time. In this paper, fresh adult perfused cadaveric head specimens and dry adult cadaveric head specimens were taken as the experimental objects. The anterior wall of sphenoid sinus and the internal septum of sphenoid sinus were excised under neuroendoscope. The structures of the lateral wall of sphenoid sinus were identified and dissected. The lateral wall of sphenoid sinus and the bone of skull base were opened with micro drill, The meninges were exposed and cut open, and the related structures were dissected, observed and photographed. The experimental results show that it is relatively safe to operate in the range of less than 8mm, and the rock tip can be found accurately. The measurement of the bony structure of the skull base is helpful for the surgeon to judge the course of the internal carotid artery and its adjacent structure.

Anatomical Variations of the Anterior Belly of the Digastric Muscle

A routine dissection of the digastric muscle reflected that it originated by two muscle bellies namely. the anterior and posterior belly which are connected by an intermediate tendon (IT). These bellies originated from the mastoid process of the temporal bone and the digastric fossa of the mandible respectively. The digastric muscle serves as an important surgical landmark in surgical interventions involving the submental area however, accessory bellies may interfere with surgical intervention in this area. Therefore, this study aimed to document the occurrence of the anatomical variations in the anterior belly of the digastric muscle (ABDM) in a selected number of cadaveric samples. Ten bilateral adult cadaveric head and neck specimens (n = 20) were macro-dissected in order to document the morphology of the digastric muscle. The accessory bellies in the ABDM was observed in 60 % of the specimens. Unilateral and bilateral variations were observed in 20 % and 30 % of the specimens, respectively. These accessory bellies originated in the digastric fossa, ABDM, IT and hyoid bone, and inserted into the mylohyoid raphe, mylohyoid muscle and hyoid bone. In addition, an anomalous main ABDM was observed in 10 % of the specimens inserting through a transverse tendon into the hyoid bone. Variations in the digastric muscle are common especially the accessory bellies, therefore, a comprehensive understanding of these anatomical variations could be of clinical importance to the surgeons during head and neck radiological diagnosis and surgical interventions.

Microscopic anatomy study of artery of auricle for auricle replantation

Objective To provide the anatomical information for auricle replantation. Methods From March, 2016 to March, 2019, a total of 25 fresh adult cadaveric head were used, 20 of these specimens were perfused with plastic and eroded to be vascular cast mold, 5 specimens perfused with red latex for anatomy, then observed the origin, course, diameter and arteries anastomose between branches of the posterior auricular artery (PAA) and superficial temporal artery (STA). Results The main blood supply to the auricle were auricle branches of PAA and STA. The auricle branches of PAA and STA both divided into superior, intermedius and inferior branches, and distributed in the auricle posterior surface and anterior surface, respectively. The auricle branches of PAA running across ear cartilage, distributed in the anterior surface, and anastomosed with auricle branches of STA. The diameters of these branches at the initiating portion were 0.2-0.8 mm. Eighty percent of blood supply to earlobe was from the inferior branches of PAA, and 20% from the STA. Conclusion The auricle branches of PAA played an important role to the auricle replantation. The auricle branches of PAA should be the firstly selected vessle in operation, and the auricle branches of STA be the second choice. Key words: Posterior auricular artery; Superficial temporal artery; Auricle replantation; Microscopic anatomy

Adjunctive techniques to improve access of the endoscopic prelacrimal recess approach.

To determine whether adjunctive surgical techniques could improve access of instruments provided by the endoscopic prelacrimal recess approach to the anatomical boundaries of the maxillary sinus, and pterygopalatine and infratemporal fossa. Ten fresh-frozen adult cadaver heads were utilized. The anatomical areas of interest were fixed, bony boundaries of the maxillary sinus, infratemporal fossa, and pterygopalatine fossa: alveolar recess (AR), zygomatic recess (ZR), perpendicular plate of the palatine bone (PB), ascending ramus of mandible (RM), floor of the orbit medial and lateral to infraorbital nerve (M-ION and L-ION, respectively). Access to the areas were compared using standard sinus surgery instruments (straight and 45° forceps) introduced via the prelacrimal recess approach, trans-septal window and canine fossa puncture. The prelacrimal recess approach successfully provided access to the PB and M-ION in >90% of dissections when using both the straight and 45° forceps. With the straight forceps, the ability to successfully access to the AR and ZR was the lowest at 50% and 35% respectively, although improving to 75% and 60% respectively with the 45° forceps. Access to the AR, ZR, and L-ION improved significantly when the 45° forceps was introduced through the trans-septal window. Frequency of access to the RM when either instruments when introduced through the canine fossa puncture was no greater than 60% of the dissections. The addition of a small trans-septal window for instruments significantly improved access of the prelacrimal recess approach especially to the orbital floor, lateral margins of the maxillary sinus, and retromaxillary space. 4 Laryngoscope, 130: 1857-1863, 2020.

The Petroclinoid Ligament: Its Morphometrics, Relationships, Variations, and Suggestion for New Terminology.

The anatomy and definition of the petroclinoid ligament (PCL) and its relationship with the abducens nerve are variably described. The goal of this study was to clarify the anatomy of the PCL and better elucidate its relationship with the abducens nerve. Thirty-six sides from 18 fresh-frozen adult cadaveric heads were used in this study. Specimens were all Caucasian and derived from 10 males and 8 females. The mean age at death was 79 years. Dissection of the PCL and abducens nerve was performed using a surgical microscope. The anterior and posterior attachments of the PCL, and position of the abducens nerve were noted. Subsequently, the width, thickness, and length of the ligament, and diameter of the abducens nerve were measured. Thirty-one sides (86.1%) were found to have a PCL, on two sides (5.6%), the PCL was ossified, and on three sides (8.3%), the PCL was absent. The width, thickness, and length of the PCL ranged from 0.54 to 3.39, 0.07 to 0.49, and 3.27 to 17.85 mm, respectively. No PCL had an anterior attachment onto the posterior clinoid process but rather, the clivus. Therefore, based on our findings, the PCL would be better described as the petroclival ligament.

Observation of human stapes and simulated stapedial lesion based on Micro-CT scanning

Objective:The aim of this study is to understand the imaging morphology of the humerus morphology and its associated simulated lesions, and to provide information for related research. Method:Six adult cadaveric heads fixed by formaldehyde solution (12 sides of the tibia) were used. One of the cadaveric heads (two sides of the tibia) was perforated and fractured under the microscope.The remaining 5 (10 sides) were used. The humerus was used for morphological measurements of the tibia.The tibia (12 sides) was taken out, Micro-CT scan was performed, and two-dimensional and three-dimensional reconstruction were performed using software such as Mimics 17.0 software. Result:①Stapedial morphologic observation:the head,curs and footplate of the stapes and the adjacent structures can be well displayed on two dimensional structures.②Quantitative measurements and statistics: There were no significant statistic differences about the data that had been measured between the right ears and the left ears.③Micro-CT was more clearly in displaying the precise structure of human stapes and the stapedial minute lesion comparing with that of HRCT. Conclusion:Micro-CT can accurately and clearly display the structure, morphology and simulated lesions (model) of the tibia, which provides important reference materials and methods for related research.

Effects of sphenoid surgery on nasal irrigation delivery.

Nasal irrigation is an important component of medical management in chronic rhinosinusitis. Nasal irrigations facilitate topical medication of therapies and lavage of mucin. In this study we aim to compare the influence of increasing surgical sphenoid openings on the distribution, force, and clearance of nasal irrigations. A study was performed on fresh-frozen adult cadaver heads. The surgical ostium was modified on one side via a simple sphenoidotomy, a sphenoid sinusectomy (type 1), and sphenoid sinusectomy (type 3a). The nasal cavity was irrigated using a 240-mL squeeze bottle with 0.1% fluoroscein. An endoscope passed through the contralateral side through the sphenoid septum recorded the irrigation. Videos were recorded and blindly assessed. The distribution was defined as either no irrigation, less than one third of the sinus, less than or equal to two thirds of the sinus, or the complete sinus. The force was defined as minimal, minor, or major. The clearance was defined as no residual, less than one third of volume, less than or equal to two thirds of volume, and more than two thirds volume. Ordinal correlation scores were assessed using the Kendall tau-B test. Nine specimens (sphenoid sinuses) were assessed (44.4% female; age, 75.0 ± 12.7 years). The use of a sphenoid sinusectomy or larger produced better distribution (percent specimens with more than one third: 100% vs 59%, p < 0.01), more force (percent major: 83% vs 29%, p < 0.01), and better clearance (percent with one third or less remaining: 56% vs 18%, p < 0.01). Increasing sphenoid ostial size improves nasal irrigation penetration. We propose that greater sphenoid sinusectomy size allows for improved lavage and irrigation penetration. Complete removal of the anterior face appears to mitigate pooling of irrigation.

Extended Supraorbital Approach with Modified Eyebrow Incision: Technical Note

The extended supraorbital approach through a modified eyebrow incision is a minimally invasive variant of the frontotemporal or pterional approach that enriches a neurosurgeon's armamentarium for the treatment of pathologies lateral to the anterior clinoid process, by advancing laterally with frontal facial nerve branches monitoring. To demonstrate the steps of the approach, we studied 2 formalin-fixed and artery/vein silicone-injected adult cadaveric heads, and reviewed 1 of the 3 clinical cases operated on to illustrate the applicability of the approach. A 56-year-old woman presented with a history of seizures and a complaint of headache that started 2 months ago. She underwent an examination with brain magnetic resonance imaging that showed a dural-based lesion at the medial third of the lesser wing of sphenoid (which is consistent with meningioma). The patient underwent craniotomy with an extended supraorbital approach through a modified eyebrow incision that allowed Simpson grade II removal to be performed and good aesthetic outcome to be achieved. The extended supraorbital approach through a modified eyebrow incision is a minimally invasive approach that can add to a neurosurgeon's armamentarium and be used with microscopy, assisted by endoscope, or both to reach the anterior and middle cranial fossae.

Anatomical study in exposed area and operating space of extended endonasal approach to the ventral region of cranio-cervical junction

Objective To explore the scope, feasibility and indications of extended neuroendoscopic endonasal approach to reveal the region of cranial-cervical junction. Methods Ten (20 sides) intact frozen adult cadaveric heads were used to simulate the extended neuroendoscopic endonasal approach to remove the anterior tubercle of atlas, part of the atlas anterior arch, odontoid and part of the slope. In the cranial-cervical junction area, we observed the exposed range and measured the distance from the nostril to the anterior tubercle of atlas, the height and width of the anterior arch of the atlas, the distance of bilateral medial margin of occipital condyle, the distance of bilateral medial margin of the foramen lacerum, the vertical distance from the occipital condyle to the homolateral foramen lacerum, and the height, anteroposterior diameter and transverse diameter of the odontoid. Results The exposed range of the extended neuroendoscopic endonasal approach was as follows: when the lesion was located at the foramen magnum, the medial margin of the occipital condyle was the boundary of both sides, the root of the odontoid was the lower boundary, and the lower edge of the occipital bone was the upper boundary. When the lesion was located at the region of cranial-cervical junction, the upper edge of the foramen lacerum on both sides was the upper boundary, and the foramen lacerum and the outer edge of the occipital condyle were the boundaries of both sides of the bone window. By measurement, the distance from the nostril to the anterior tubercle of atlas was 8.9-9.7 cm, with an average of 9.3±0.3 cm. The height of the anterior arch of the atlas was 2.3-3.0 cm, with an average of 2.7±0.3 cm; the width was 1.5-2.0 cm, with an average of 1.8±0.2 cm; the distance of bilateral medial margin of occipital condyle was 1.5-2.0 cm, with an average of 1.8±0.2 cm; the distance of bilateral medial margin of the foramen lacerum was 2.1-2.9 cm, with an average of 2.4 ±0.3 cm; the vertical distance from the occipital condyle to the homolateral foramen lacerum was 1.6-2.2 cm, with an average of 1.9±0.3 cm; the height of the odontoid was 0.9-1.3 cm, with an average of 1.1±0.2 cm, its length was 0.8-1.3 cm, with an average of 1.1±0.2 cm; the transverse diameter of the dentate was 0.9-1.2 cm, with an average of 1.0±0.1 cm.The maximum exposed area of cranio-cervical junction was 6.4-9.8 cm2, with an average of 8.6±1.6 cm2. Conclusion The extended neuroendoscopic endonasal approach with removal of the anterior tubercle of atlas and part of the atlas anterior arch could effectively reveal the cranial-cervical junction area which is suitable for the treatment of odontoid deformity, skull base depression and atlantoaxial joint dislocation as well as resection of epidural tumors in the cranial-cervical junction and ventral and ventral midline tumors. Key words: Natural orifice endoscopic surgery; Anatomy; Cranio-cervical junction; Extended endonasal approach

A Contralateral Transfalcine Approach to the Mesial Frontoparietal Region and Cingulate Gyrus: A Cadaveric Feasibility Study

Neurosurgery for lesions located the mesial frontoparietal region and cingulate gyrus may need significant brain retraction, which may cause neural injury. Therefore, the goal of this anatomic study was to evaluate a contralateral transfalcine approach to these regions. Eight adult cadaver heads were used in this study. An 8× 8 cm craniotomy was performed, and bilateral longitudinal incisions were made into the dura mater adjacent to the superior sagittal sinus. Measurements were then taken to see how much retraction was necessary for an ipsilateral approach to the mesial frontoparietal region down to the cingulate gyrus and compared with measurements using a contralateral transfalcine approach to this same region. Ipsilateral approaches required 1.5 to 3 cm of lateral retraction (40-50°) from the midline, whereas contralateral transfalcine approaches required 0.5 to 1 cm of lateral retraction (10-20°). In comparison with the traditional ipsilateral interhemispheric approach to lesions of the mesial frontoparietal region and cingulate gyrus, the contralateral transfalcine approach was found to necessitate less hemispheric retraction and provided a better working angle. Clinical validation of this technique is now necessary.

Surgical enlargement of the nasomaxillary aperture and transnasal conchotomy of the ventral conchal sinus: Two surgical techniques to improve sinus drainage in horses.

ObjectiveTo evaluate 2 surgical techniques for establishing and/or improving paranasal sinus drainage in cadaver heads and horses with sinusitis and evaluate the feasibility of postoperative transnasal sinus endoscopy.Study designEx vivo study (equine cadaver heads) and case series.Sample populationNine adult equine cadaver heads and 8 horses with recurrent sinusitis.MethodsFor the ex vivo study, the following procedures were performed on 9 cadaver heads: preoperative and postoperative computed tomography (heads 1–6), endoscopy‐guided transnasal conchotomy of the ventral conchal sinus (TCVCS) and surgical enlargement of the nasomaxillary aperture (SENMAP) on opposite sides (heads 1–3), combined TCVCS and SENMAP on both sides (heads 4–9), evaluation of sinus drainage before and after surgery (heads 7–9), and postoperative transnasal endoscopy (heads 4–9). For the case series, 8 horses with secondary sinusitis were treated in standing position with SENMAP and/or TCVCS and postoperative transnasal endoscopy.ResultsSinonasal communications were successfully created in all cadavers and affected live horses. Transnasal endoscopy of all sinuses except the middle conchal sinus was possible in heads 4–9 and in all clinical cases. Sinus drainage was improved (P = .028) by combining techniques. Blood loss in live horses ranged from 0.5–5.5 L (1.95 ± 1.5) per horse. Sinusitis resolved in all affected horses during follow‐up of 3.2–25.5 months (13.5 ± 8.5).ConclusionTransnasal conchotomy of the ventral conchal sinus and SENMAP consistently created large sinonasal communications, facilitating sinus endoscopy and improving sinus drainage.Clinical significanceTransnasal conchotomy of the ventral conchal sinus and SENMAP are viable options to treat horses with sinusitis and anatomical obstructions of the sinonasal communications.

Supracerebellar Infratentorial and Occipital Transtentorial Approaches to the Pulvinar: Ipsilateral Versus Contralateral Corridors.

Due to the critical neurovascular structures that surround the pulvinar, deciding the best surgical approach can be challenging, with multiple options available. To analyze and compare the ipsilateral vs the contralateral version of the 2 main approaches to the cisternal pulvinar surface: paramedian supracerebellar infratentorial (PSCI) and interhemispheric occipital transtentorial (IOT). The PSCI and IOT approaches were performed on 7 formalin-fixed adult cadaveric heads to evaluate qualitatively and quantitatively the microsurgical exposure of relevant anatomic structures. We quantitatively measured the corridor distance to our target with each approach. The ipsilateral PSCI approach provided an easier access and a better exposure of the anteromedial portion of the cisternal pulvinar surface. The contralateral approach provided a wider and more accessible exposure of the posterolateral portion of the cisternal pulvinar surface. When protrusion of the posterior parahippocampal gyrus above the free edge of the tentorium was present, the contralateral PSCI approach provided an unobstructed view to both areas. The IOT approach provided a better view of the anteromedial portion of the cisternal pulvinar surface, especially with a contralateral approach. Multiple approaches to the pulvinar have been described, modified, and improved. Based on this anatomic study we believe that although the corridor distance with a contralateral approach is longer, the surgical view and access can be better. We recommend the use of a PSCI contralateral approach especially when a significant protrusion of the posterior parahippocampal gyrus is present.

An anatomical study of the lingual nerve in the lower third molar area.

The lingual nerve (LN) is a branch of the mandibular division of the trigeminal nerve, and its injury is one of the major complications during oral surgery. This study aims to investigate the anatomy of the LN in the lower third molar area. Twenty sides from ten fresh-frozen adult cadaveric Caucasian heads were examined to measure the diameter of the LN. The mean diameter of the LN was 2.20±0.37 mm (range, 1.61–2.95 mm). There were no statistically significant differences in the measurements between sexes, sides, or tooth status (dentulous or edentulous). Understanding the anatomical features of the LN is essential for performing any surgical procedure in the oral region.

An endoscopic-assisted technique for the enlarged middle cranial fossa approach to the petroclival region: an anatomic study

Objective:Through the observation and measurement of the adjacent anatomical structures exposed by the pure microscope and endoscopic-assisted technique for the enlarged middle cranial fossa approach to the petroclival region, quantitative compare the advantages of endoscopic-assisted technique and the pure microscope exposure. Method:The enlarged middle cranial fossa approach was performed on 10 cases (20 sides) fresh adult cadaveric head specimens in which the vessels were injected with colored silicone. At the end of every enlarged middle cranial fossa approachs, endoscope assisted technique was applied. The effective working areas were measured under pure microscope and endoscopic-assisted technique. Result:The distance between the trigeminal nerve root entering the pons and the upper limit of exposure to the middle of the ventral brainstem under the microscope was（15.95±0.48）mm；the distance from the initial point of the acoustic-facial bundle to the lower bound of exposure to the middle of the ventral brainstem under the microscope was（10.79±0.51）mm；The distance between the trigeminal nerve root entering the pons and the upper limit of exposure to the middle of the ventral brainstem under endoscopy was（18.88±0.36）mm；the distance from the initial point of the acoustic-facial bundle to the lower bound of exposure to the middle of the ventral brainstem under endoscopy was（14.56±0.64）mm. Conclusion:In the anatomic study of the enlarged middle cranial fossa approach to the petroclival region, the endoscopic assistance has a larger effective exposure space and flexible perspective compared with the operation under the microscope, which is helpful to accurately locate the position and size of the lesion during surgery, accurately identify the important nerves and blood vessels surrounding the lesion, so as to improve the resection rate and reduce the recurrence rate.

Dissection and observation of a large unnamed nerve in the posterior cervical triangle

To characterize the anatomical features of a large unnamed nerve in the posterior cervical triangle and clarify its relationship with the lesser occipital nerve. We dissected 31 adult formalin-fixed cadaver head and neck specimens (62 sides). The lateral cervical region, the anterior cervical region, the sternocleidomastoid region, and the occipital region were dissected to define the anatomical features of the unnamed nerve. This unnamed nerve was identified in the posterior cervical triangle in 96.8% of the specimens. The main trunk of the nerve had a diameter of about 3 mm with a length of around 10 cm. The nerve arose from the anterior branch of the second cervical nerve (C2, C2-3), entered the posterior cervical triangle at 1-3 cm above the accessory nerve, and continued to ascend along or in parallel with the posterior border of the sternocleidomastoid muscle. It passed between the attachments of the sternocleidomastoid and the trapezius to the occiput and divided into 3-5 branches, which innervated the skin area between the lesser and greater occipital nerves. We identified a large unnamed nerve in the posterior cervical triangle, for which we coined the name "long occipital nerve" based on its unique anatomical features. The discovery of this nerve can be important for local surgery and for diagnosis and treatment of related diseases.

Anatomic characteristics of supraorbital and supratrochlear nerves relevant to their use in corneal neurotization.

Corneal denervation can lead to opacification and blindness. A new treatment technique, surgical corneal neurotization, transfers healthy donor nerve, (most commonly contralateral supratrochlear or supraorbital) to the affected limbus to prevent corneal destruction and improve healing potential of the cornea following insult. We examine gross and histomorphometric anatomy of the supratrochlear and supraorbital nerves relevant to their use in corneal neurotization. For each of nine adult cadaver heads, bilateral supraorbital and supratrochlear nerves were dissected from the supraorbital rim to the anterior hairline. The following data were recorded for each nerve: exit from the orbit through a notch versus foramen; horizontal distance from midline at the supraorbital rim; and distance from orbital exit to first branching point. Samples of all left supraorbital and supratrochlear nerves were obtained at the level of the supraorbital rim and at points 3 cm and 6 cm distally for histomorphometric analysis. Myelinated axon counts were determined for each sample. Four supraorbital foramina, 14 supraorbital notches, two supratrochlear foramina, and 15 supratrochlear notches were identified. Average supraorbital and supratrochlear distances to midline were 26.5 mm and 21 mm respectively. Average myelinated axon counts for both nerves were greater at the orbital rim (supraorbital: 6018, supratrochlear: 2533) than at 6 cm distally (supraorbital: 1621, supratrochlear: 1112). Anatomic dissection shows relative close approximation of the supraorbital and supratrochlear nerves, with a high proportion of both nerves exiting the orbit through foramina. The supraorbital nerve at the orbital rim contains the greatest number of myelinated axons.

Reconstruction of anterior inferior cerebellar artery by occipital artery through extended retrosigmoid approach

Objective To explore the feasibility of occipital artery(OA) to anterior inferior cerebellar artery (AICA) through the extended retrosigmoid approach, also perform a systemic microanatomical study of OA and AICA with the exposure of extended retrosigmoid approach, find the easy way to perform the procedure. Methods From September, 2016 to January, 2017, 5 adult cadaveric heads injected with colored latex (total 10 sides) were performed the extended retrosigmoid approach, and measured the caliber of distal occipital artery (OA), the final length of the OA harvest, the reliable landmark of the OA harvest, and the distance from the flocculonodular segment of anterior inferior cerebellar artery (AICA) to the OA, the diameter of AICA flocculonodular segment branch. Whole procedure of OA to IACA bypass also be performed. Statistical analysis was performed. Results By the extended retrosigmoid approach, AICA flocculonodular segment could be easily exposure, the average diameter was 1.2 mm, the OA branch could be harvested in average was (72.3±3.3)mm in length from the occipital sulcus, and the average distance between occipital sulcus and AICA flocculonodular segment was (47.6±1.9)mm. The bypass procedure also could be performed through the proper corridor. Conclusion The Extended retrosigmoid approach is a safe and efficient way to perform the OA-AICA bypass procedure, and the procedure is easier to be performed than other surgical approaches. Key words: Occipital artery; Anterior inferior cerebellar artery; OA-AICA bypass; Extended-retrosigmoid approach; Applied anatomy

Endoscopic Anatomic Study Via Grinding Partial Petrous Ridge to the Middle Fossa in Retromastoid Keyhole Approach.

This study aimed to observe the range of exposure, indications, and feasibility of the retromastoid keyhole approach via grinding partial petrous ridge to the middle fossa. Simulated endoscopic surgeries via grinding suprameatal tubercle and petrous ridge to expose the middle fossa in retromastoid keyhole approach were performed on 8 adult cadaver heads (16 sides) fixed by formalin. The maximum exposure range in endoscope was observed. The boundaries of Parkinson triangle and the anatomic structures contained by Meckel cave and cavernous sinus (CS) lateral wall were revealed. The distances from midpoint of sigmoid sinus posterior border to every important anatomic structures in the middle fossa and the length of all sides of Parkinson triangle were measured. By using endoscope, the exposure of the cerebellopontine angle, ventrolateral brainstem, incisure of tentorium, petroclival region, and CS lateral wall were satisfactory. Many important anatomic structures in middle fossa were exposed well. The distances from midpoint of posterior border of sigmoid sinus to suprameatal tubercle, trigeminal semilunar ganglion, posterior curve segment of internal carotid artery were 34.42 ± 2.14, 54.52 ± 2.87, and 65.15 ± 3.13 mm. The lengths of all sides of Parkinson triangle were 18.97 ± 2.93, 16.23 ± 2.02, and 8.04 ± 2.34 mm. The retromastoid keyhole approach via grinding partial petrous ridge to the middle fossa by using endoscope can increase the exposure of middle fossa effectively, which is proper for most lesions in posterior cranial fossa while some parts extend to middle fossa.