Endoscopic transnasal skull base surgery: pushing the boundaries.

The endoscopic endonasal approach (EEA) has significantly evolved since its initial uses in pituitary and sinonasal surgery. The literature is filled with reports and case series demonstrating efficacy and advantages for the entire ventral skull base. With competence in 'minimally invasive' parasellar approaches, larger and more complex approaches were developed to utilize the endonasal corridor to create maximally invasive endoscopic skull base procedures. The challenges of these more complex endoscopic procedures include a long learning curve and navigating in a narrow corridor; reconstruction of defects presented new challenges and early experience revealed a significantly higher risk of cerebrospinal fluid leak. Despite these challenges, there are many benefits to the EEA including avoidance of brain and neurovascular retraction, improved visualization, a direct corridor onto many tumors and the two-surgeon approach. Most importantly, the EEA provides a midline corridor to directly access tumors, which displace critical neurovascular structures laterally, giving it an inherent advantage of minimizing any manipulation of these structures and thus decreasing their potential injury.

Surgical morbidity of the extradural anterior petrosal approach: the Lariboisière experience.

OBJECTIVE: Concerns about the approach-related morbidity of the extradural anterior petrosal approach (EAPA) have been raised, especially regarding temporal lobe and venous injuries, hearing impairment, facial nerve palsy, cerebrospinal fluid fistula, and seizures. There is lack in the literature of studies with detailed analysis of surgical complications. The authors have presented a large series of patients who were treated with EAPA, focusing on complications and their avoidance. METHODS: The authors carried out a retrospective review of patients who underwent EAPA at their institution between 2012 and 2021. They collected preoperative clinical characteristics, operative reports, operative videos, findings on neuroimaging, histological diagnosis, postoperative course, and clinical status at last follow-up. For pathologies without petrous bone invasion, the amount of petrous apex drilling was calculated and classified as low (< 70% of the volume) or high (≥ 70%). Complications were dichotomized as approach related and resection related. RESULTS: This study included 49 patients: 26 with meningiomas, 10 brainstem cavernomas, 4 chondrosarcomas, 4 chordomas, 2 schwannomas, 1 epidermoid cyst, 1 cholesterol granuloma, and 1 osteoblastoma. The most common approach-related complications were temporal lobe injury (6.1% of patients), seizures (6.1%), pseudomeningocele (6.1%), hearing impairment (4.1%), and dry eye (4.1%). Approach-related complications occurred most commonly in patients with a meningioma (p = 0.02) and Meckel's cave invasion (p = 0.02). Gross-total or near-total resection was correlated with a higher rate of tumor resection-related complications (p = 0.02) but not approach-related complications (p = 0.76). Inferior, lateral, and superior tumoral extension were not correlated with a higher rate of tumor resection-related complications. No correlation was found between high amount of petrous bone drilling and approach- or resection-related complications. CONCLUSIONS: EAPA is a challenging approach that deals with critical neurovascular structures and demands specific skills to be safely performed. Contrary to general belief, its approach-related morbidity seems to be acceptable at dedicated skull base centers. Morbidity can be lowered with careful examination of the preoperative neuroradiological workup, appropriate patient selection, and attention to technical details.

Midline Suboccipital Subtonsillar Approach in Semisitting Position for Resection of Jugular Tubercle Meningioma: 2-Dimensional Operative Video.

We present a case of a large jugular tubercle meningioma that was removed through a midline suboccipital subtonsillar approach in semisitting position. The patient is a 49-year-old woman with chronic, medication-resistant cephalgias but devoid of any subjective focal neurological deficit. On magnetic resonance imaging (MRI), an extra-axial lesion, originating from the left jugular tubercle was discovered. There was significant obliteration of the peripontine cisternal space, and compression of the adjacent pontomedullary junction; the lesion also extended into the left jugular foramen. On physical exam, an absent gag reflex was noted on the left, as well as a moderate deviation of the uvula to the contralateral side (partial Vernet's syndrome). A gross-total resection was achieved, histopathology confirmed a World Health Organization (WHO) grade I angiomatous meningioma with a low-proliferation index. The patient was discharged home 4 days after surgery with intact function of the lower cranial nerves (CN) following immediate and complete resolution of the preexisting partial CNs IX and X deficits. At 2-year follow-up, there was no indication of intradural residual or recurrence. In summary, the midline suboccipital subtonsillar approach is a simple and effective tool with limited morbidity in the armamentarium for the microsurgical management of pathologies residing in the posterior cranial fossa or the craniocervical junction. Major limitations exist for lesions extending above the internal acoustic canal or those of fibrous consistence featuring widespread adhesion to the ventral brainstem or vascular encasement. Provided the necessary anesthesiological precautions and intraoperative procedures the semisitting position is safe and effective. The link to the video can be found at: https://youtu.be/bbVXagwhDCo .

Lateral Suboccipital Approach in Semisitting Position for Resection of Vagal Schwannoma: 2-Dimensional Operative Video.

We present a case of a sizeable vagal schwannoma that was resected through a lateral suboccipital approach in semisitting position. An extra-axial lesion, occupying the left cerebellomedullary cistern and extending from the pontomedullary junction to the jugular foramen was incidentally discovered in a 40-year-old woman afflicted with secondary progressive multiple sclerosis during repeated magnetic resonance imaging ( Fig. 1 ). On physical examination, a mild deviation of the uvula to the right and a diminished gag reflex were observed. The patient was referred to our department after considerable growth of the lesion was noted and a broad interdisciplinary consensus was reached to treat the lesion surgically. A gross total resection was achieved, histopathology confirmed a WHO I schwannoma with a low proliferation index. Postoperative dysphonia resolved completely within a few weeks, there was no collateral neurological deficit and especially no functional dysphagia. At 3-year follow-up, there was no indication of residual or recurrence. This 2-dimensional video demonstrates pre- and postoperative imaging, positioning and set-up of operating room, anatomical and surgical nuances of the skull base approach, and the operative technique for microdissection of the schwannoma from the critical neurovascular structures ( Fig. 2 ). In summary, the lateral suboccipital approach in semisitting position is a powerful tool in the armamentarium for the microsurgical management of various pathologies residing in the posterior cranial fossa, especially large and vascularized schwannomas. Provided the necessary anesthesiological precautions and intraoperative procedures the semisitting position is safe and effective. The link to the video can be found at: https://youtu.be/-9o_qJGkQhg .

C1 Hemilaminectomy for Resection of Foramen Magnum Meningioma: 2-Dimensional Operative Video.

We present a case of a sizeable foramen magnum meningioma that was resected through a C1 hemilaminectomy in prone (concorde) position. The patient is a 51-year-old woman with a 3-month history of progressive paresthesia of the upper and lower extremities, followed by gait disturbance, and hand apraxia. There was no complaint of nuchal pain. On magnetic resonance imaging (MRI) a briskly enhancing extra-axial, intradural craniospinal lesion, extending from the basion of the lower clivus, over the tectorial membrane to the middle of the axis' body was discovered. There was significant transposition and compression of the medulla and corresponding focal hyperintensity on T2-weighted imaging. On physical examination, the patient was ambulatory independently, notwithstanding a pronounced spinal ataxia. There were deficits in sensation and proprioception, as well as urinary retention, but preserved function of the lower cranial nerves. In view of the profound transposition of the medulla, utilization of the corridor created by the tumor seemed feasible and we felt that a limited C1 hemilaminectomy would provide sufficient microsurgical access thus obviating a more extensive and invasive approach to the craniocervical junction. A gross-total resection was achieved; histopathology confirmed a World Health Organization (WHO) grade I angiomatous meningioma with a low-proliferation index. The patient was discharged home 3 days after surgery and her spinal ataxia resolved completely within 3 months of out-patient rehabilitation. At 3-year follow-up, there was no indication of residual or recurrence. The link to the video can be found at: https://youtu.be/WyShbfr-xi0 .

Anatomy of the Orbit.

The orbit is a paired, transversely oval, and cone-shaped osseous cavity bounded and formed by the anterior and middle cranial base as well as the viscerocranium. Its main contents are the anterior part of the visual system, globe and optic nerve, and the associated neural, vascular, muscular, glandular, and ligamentous structures required for oculomotion, lacrimation, accommodation, and sensation. A complex stream of afferent and efferent information passes through the orbit, which necessitates a direct communication with the anterior and middle cranial fossae, the pterygopalatine and infratemporal fossae, as well as the aerated adjacent frontal, sphenoidal, and maxillary sinuses and the nasal cavity. This article provides a detailed illustration and description of the microsurgical anatomy of the orbit, with a focus on the intrinsically complex spatial relationships around the annular tendon and the superior orbital fissure, the transition from cavernous sinus to the orbital apex. Sparse reference will be made to surgical approaches, their indications or limitations, since they are addressed elsewhere in this special issue. Instead, an attempt has been made to highlight anatomical structures and elucidate concepts most relevant to safe and effective transcranial, transfacial, transorbital, or transnasal surgery of orbital, periorbital, and skull base pathologies.

Seizure Risk following Open and Expanded Endoscopic Endonasal Approaches for Intradural Skull Base Tumors.

Objectives The incidence of seizures following a craniotomy for tumor removal varies between 15 and 20%. There has been increased use of endoscopic endonasal approaches (EEAs) for a variety of intracranial lesions due to its more direct approach to these pathologies. However, the incidence of postoperative seizures in this population is not well described. Methods This is a single-center, retrospective review of consecutive patients undergoing EEA or open craniotomy for resection of a cranial base tumor between July 2007 and June 2014. Patients were included if they underwent an EEA for an intradural skull base lesion. Positive cases were defined by electroencephalograms and clinical findings. Patients who underwent a craniotomy to remove extra-axial skull base tumors were analyzed in the same fashion. Results Of the 577 patients treated with an EEA for intradural tumors, 4 experienced a postoperative seizure (incidence 0.7%, 95% confidence interval [CI]: 0.002-0.02). Over the same period, 481 patients underwent a craniotomy for a skull base lesion of which 27 (5.3%, 95% CI: 0.03-0.08) experienced a seizure after surgery. The odds ratio for EEA was 0.13 (95% CI: 0.05-0.35). Both populations were different in terms of age, gender, tumor histology, and location. Conclusion This study is the largest series looking at seizure incidence after EEA for intracranial lesions. Seizures are a rare occurrence following uncomplicated endonasal approaches. This must be tempered by selection bias, as there are inherent differences in which patients are treated with either approach that influence the likelihood of seizures.

Midline Suboccipital Subtonsillar Approach with C1 Laminectomy for Resection of Foramen Magnum Meningioma: 2-Dimensional Operative Video.

We present a case of a medium-sized foramen magnum meningioma that was resected through a midline suboccipital subtonsillar approach with C1 laminectomy in prone (Concorde) position. The patient is a 77-year-old woman with a 6-month history of intermittent vertigo, moderate gait instability, and slight decline of memory. On magnetic resonance imaging (MRI) an extra-axial intradural lesion was discovered that originated from the right epicondylar region just inferior to the jugular tubercle and occupied the anterolateral aspect of the foramen magnum. There was moderate transposition and compression of the medulla at the level of the cerebellar tonsils. On physical examination the patient was ambulatory independently without motor weakness but exhibited some gait instability. The function of the lower cranial nerves was preserved. A gross-total resection was achieved, histopathology confirmed a WHO grade-I meningothelial meningioma with a low-proliferation index. The patient was discharged home 5 days after surgery, her gait instability improved significantly immediately after surgery and had resolved completely after 2 weeks of inpatient rehabilitation. There was no other neurological deficit. At 3-month follow-up MRI, there was no indication of meningioma residual or recurrence. In summary, the midline suboccipital subtonsillar approach is a powerful tool with limited morbidity in the armamentarium for the microsurgical management of a variety of pathologies residing in the posterior cranial fossa and the craniocervical junction. Oftentimes the space created by the pathology opens up corridors that can be exploited for microsurgical access to avoid more extensive surgical approaches. The link to the video can be found at: https://youtu.be/0uUxs13ze7w .

Nasopharyngeal muscle patch for the management of internal carotid artery injury in endoscopic endonasal surgery.

OBJECTIVE: Injury to the internal carotid artery (ICA) is the most critical complication of endoscopic endonasal skull base surgery. Packing with a crushed muscle graft at the injury site has been an effective management technique to control bleeding without ICA sacrifice. Obtaining the muscle graft has typically required access to another surgical site, however. To address this concern, the authors investigated the application of an endonasally harvested longus capitis muscle patch for the management of ICA injury. METHODS: One colored silicone-injected anatomical specimen was dissected to replicate the surgical access to the nasopharynx and the stepwise dissection of the longus capitis muscle in the nasopharynx. Two representative cases were selected to illustrate the application of the longus capitis muscle patch and the relevance of clinical considerations. RESULTS: A suitable muscle graft from the longus capitis muscle could be easily and quickly harvested during endoscopic endonasal skull base surgery. In the illustrative cases, the longus capitis muscle patch was successfully used for secondary prevention of pseudoaneurysm formation following primary bleeding control on the site of ICA injury. CONCLUSIONS: Nasopharyngeal harvest of a longus capitis muscle graft is a safe and practical method to manage ICA injury during endoscopic endonasal surgery.

Clinical Experience with Secondary Endoscopic Reconstruction of Clival Defects with Extracranial Pericranial Flaps.

Objectives The aim of this study is to report the clinical outcome of extracranial pericranial flaps (ePCF) used for reconstruction of clival dural defects following failure of primary repair. Design Retrospective review of skull base database. Setting Academic medical center. Participants Patients undergoing reconstruction of clival defects with ePCF following endoscopic endonasal surgery (EES). Main outcome measures Postoperative cerebrospinal fluid (CSF) leak, meningitis, and flap necrosis. Results Seven patients (five males and two females) who underwent ePCF reconstruction for clival defects following EES were included. All patients (ages 8-64 years) had a postoperative CSF leak due to a failed primary clival reconstruction (five had one, one had two, and one had three failed CSF leak repairs prior to ePCF reconstruction). Nasoseptal and inferior turbinate (lateral nasal wall) flaps were not available for secondary reconstruction due to prior surgeries. The immediate success rate of ePCF for the reconstruction of clival defects in patients with multiple flap failures was 58%. Two patients developed CSF leaks that were successfully repaired endoscopically with the addition of free tissue grafts; one patient had partial flap necrosis that required debridement; none required an additional vascularized flap. Width of the defect, length of the defect, properties of the ePCF, and age did not demonstrate significance ( p > 0.05) for adverse outcome. Conclusion An ePCF is a reconstructive option for high-risk, large clival defects when other local and regional vascularized flaps are not available or fail. ePCFs can be used for reconstruction of clival defects in all populations, including pediatric patients.

Mobilization of the Anterior Inferior Cerebellar Artery When Firmly Adherent to the Petrous Dura Mater-A Technical Nuance in Retromastoid Transmeatal Vestibular Schwannoma Surgery: 3-Dimensional Operative Video.

The anterior inferior cerebellar artery (AICA) usually runs loosely within the cerebellopontine cistern; in rare cases, however, it is firmly adherent to the petrous dura mater.1,2 Recognizing this variation is particularly important in vestibular schwannoma surgery via the retrosigmoid transmeatal approach to prevent the high morbidity associated with vascular injury. This video demonstrates a surgical technique to effectively mobilize the AICA when firmly adherent to the petrous dura mater. A 39-year-old man presented with a history of progressive right-sided hearing loss without facial weakness or other associated symptoms3. Magnetic resonance imaging (MRI) demonstrated an intracanalicular lesion, suggestive of vestibular schwannoma. During follow-up, audiometry confirmed a further slight deterioration of hearing and repeated MRI demonstrated tumor growth (T2 according to Hannover classification). Since the patient opted against radiosurgery, a retrosigmoid transmeatal approach under continuous intraoperative monitoring was performed in supine position. Following drainage of cerebrospinal fluid and exposure of the cerebellopontine cistern, the AICA was found to be firmly adherent to the petrous dura mater. Both structures were elevated conjointly and displaced medially for safe drilling of the inner auditory canal, sufficient exposure, and complete excision of the vestibular schwannoma. The patient had an excellent recovery, hearing and facial function were preserved, and no secondary neurological deficits noted.The patient consented to publication of this anonymized video.

Retrosigmoid Transmeatal Endoscope-Assisted Approach in Semi-Sitting Position for Resection of Vestibular Schwannoma: 2-D operative Video.

We present a case of a mid-sized vestibular schwannoma (T3b according to the Hannover classification) that was resected through a retrosigmoid transmeatal approach in semi-sitting position under endoscopic assistance. The patient is a 52-year-old male with acute loss of functional hearing on the right side. Audiometry confirmed a loss of up to 60 dB and lost speech discrimination, there were no associated symptoms such as tinnitus or vertigo. This 2D video demonstrates positioning, OR set-up, anatomical and surgical nuances of the skull base approach and the operative technique for microdissection of the tumor from the critical neurovascular structures, especially the facial and cochlear nerves. A gross total resection was achieved and the patient discharged home after four days with unaltered function of the facial nerve (HB I). At one year follow up there was no indication of residual or recurrence. In summary, the retrosigmoid transmeatal approach is an important and powerful tool in the armamentarium for the microsurgical management of all kinds of vestibular schwannomas. Provided the necessary anesthesiological precautions and intraoperative procedures the semi-sitting position is safe and effective. If needed, the approach can be complemented by the use of an endoscope for visualization of the distal internal auditory canal. The link to the video can be found at: https://youtu.be/pPKT4_5nIn0 .

Resection of a Petroclival Meningioma via the Endoscope-Assisted Retrosigmoid Approach: 2-D Operative Video.

We present a case of a petroclival meningioma that was resected through an endoscope-assisted retrosigmoid approach via corridors above and below the facial-vestibulocochlear nerve complex. The patient is a 61-year-old female with complaints of left-sided hypesthesia and neuralgia of the infraorbital and zygomatic region, intermittent periorbital myokymia, and a slight facial palsy (HB II). This 2D video demonstrates the operative technique, anatomical and surgical nuances of the skull base approach and microdissection of the tumor from the critical neurovascular structures. A gross total resection was achieved. The patient's facial and trigeminal symptoms resolved completely within a few weeks. At 2 year follow up there was no indication of residual or recurrence. In summary, the retrosigmoid approach with endoscopic assistance is an important and powerful tool in the armamentarium for the microsurgical management of meningiomas of the lateroventral skullbase of the posterior fossa. The link to the video can be found at: https://youtu.be/Px4XIRDoALc .

The epitrigeminal approach to the brainstem.

OBJECTIVE Surgical approaches to the ventrolateral pons pose a significant challenge. In this report, the authors describe a safe entry zone to the brainstem located just above the trigeminal entry zone which they refer to as the "epitrigeminal entry zone." METHODS The approach is presented in the context of an illustrative case of a cavernous malformation and is compared with the other commonly described approaches to the ventrolateral pons. The anatomical nuances were analyzed in detail with the aid of surgical images and video, anatomical dissections, and high-definition fiber tractography (HDFT). In addition, using the HDFT maps obtained in 77 normal subjects (154 sides), the authors performed a detailed anatomical study of the surgically relevant distances between the trigeminal entry zone and the corticospinal tracts. RESULTS The patient treated with this approach had a complete resection of his cavernous malformation, and improvement of his symptoms. With regard to the HDFT anatomical study, the average direct distance of the corticospinal tracts from the trigeminal entry zone was 12.6 mm (range 8.7-17 mm). The average vertical distance was 3.6 mm (range -2.3 to 8.7 mm). The mean distances did not differ significantly from side to side, or across any of the groups studied (right-handed, left-handed, and ambidextrous). CONCLUSIONS The epitrigeminal entry zone to the brainstem appears to be safe and effective for treating intrinsic ventrolateral pontine pathological entities. A possible advantage of this approach is increased versatility in the rostrocaudal axis, providing access both above and below the trigeminal nerve. Familiarity with the subtemporal transtentorial approach, and the reliable surgical landmark of the trigeminal entry zone, should make this a straightforward approach.

The medial wall of the cavernous sinus. Part 1: Surgical anatomy, ligaments, and surgical technique for its mobilization and/or resection.

OBJECTIVE: The medial wall of the cavernous sinus (CS) is often invaded by pituitary adenomas. Surgical mobilization and/or removal of the medial wall remains a challenge. METHODS: Endoscopic endonasal dissection was performed in 20 human cadaver heads. The configuration of the medial wall, its relationship to the internal carotid artery (ICA), and the ligamentous connections in between them were investigated in 40 CSs. RESULTS: The medial wall of the CS was confirmed to be an intact single layer of dura that is distinct from the capsule of the pituitary gland and the periosteal layer that forms the anterior wall of the CS. In 32.5% of hemispheres, the medial wall was indented by and/or well adhered to the cavernous ICA. The authors identified multiple ligamentous fibers that anchored the medial wall to other walls of the CS and/or to specific ICA segments. These parasellar ligaments were classified into 4 groups: 1) caroticoclinoid ligament, spanning from the medial wall and the middle clinoid toward the clinoid ICA segment and anterior clinoid process; 2) superior parasellar ligament, connecting the medial wall to the horizontal cavernous ICA and/or lateral wall of the CS; 3) inferior parasellar ligament, bridging the medial wall to the anterior wall of the CS or anterior surface of the short vertical segment of the cavernous ICA; and 4) posterior parasellar ligament, which anchors the medial wall to the short vertical segment of the cavernous ICA and/or the posterior carotid sulcus. The caroticoclinoid ligament and inferior parasellar ligament were present in most CSs (97.7% and 95%, respectively), while the superior and posterior parasellar ligaments were identified in approximately half of the CSs (57.5% and 45%, respectively). The caroticoclinoid ligament was the strongest and largest ligament, and it was typically assembled as a group of ligaments with a fan-like arrangement. The inferior parasellar ligament was the first to be encountered after opening the anterior wall of the CS during an interdural transcavernous approach. CONCLUSIONS: The authors introduce a classification of the parasellar ligaments and their role in anchoring the medial wall of the CS. These ligaments should be identified and transected to safely mobilize the medial wall away from the cavernous ICA during a transcavernous approach and for safe and complete resection of adenomas that selectively invade the medial wall.

Cavernous sinus compartments from the endoscopic endonasal approach: anatomical considerations and surgical relevance to adenoma surgery.

OBJECTIVE Tumors with cavernous sinus (CS) invasion represent a neurosurgical challenge. Increasing application of the endoscopic endonasal approach (EEA) requires a thorough understanding of the CS anatomy from an endonasal perspective. In this study, the authors aimed to develop a surgical anatomy-based classification of the CS and establish its utility for preoperative surgical planning and intraoperative guidance in adenoma surgery. METHODS Twenty-five colored silicon-injected human head specimens were used for endonasal and transcranial dissections of the CS. Pre- and postoperative MRI studies of 98 patients with pituitary adenoma with intraoperatively confirmed CS invasion were analyzed. RESULTS Four CS compartments are described based on their spatial relationship with the cavernous ICA: superior, posterior, inferior, and lateral. Each compartment has distinct boundaries and dural and neurovascular relationships: the superior compartment relates to the interclinoidal ligament and oculomotor nerve, the posterior compartment bears the gulfar segment of the abducens nerve and inferior hypophyseal artery, the inferior compartment contains the sympathetic nerve and distal cavernous abducens nerve, and the lateral compartment includes all cavernous cranial nerves and the inferolateral arterial trunk. Twenty-nine patients had a single compartment invaded, and 69 had multiple compartments involved. The most commonly invaded compartment was the superior (79 patients), followed by the posterior (n = 64), inferior (n = 45), and lateral (n = 23) compartments. Residual tumor rates by compartment were 79% in lateral, 17% in posterior, 14% in superior, and 11% in inferior. CONCLUSIONS The anatomy-based classification presented here complements current imaging-based classifications and may help to identify involved compartments both preoperatively and intraoperatively.

The foramen lacerum: surgical anatomy and relevance for endoscopic endonasal approaches.

OBJECTIVEThe foramen lacerum is a relevant skull base structure that has been neglected for many years. From the endoscopic endonasal perspective, the foramen lacerum is a key structure due to its location at the crossroad between the sagittal and coronal planes. The objective of this study was to provide a detailed investigation of the surgical anatomy of the foramen lacerum and its adjacent structures based on anatomical dissections and imaging studies, propose several relevant key surgical landmarks, and demonstrate the surgical technique for its full exposure with several illustrative cases.METHODSTen colored silicone-injected anatomical specimens were dissected using a transpterygoid approach to the foramen lacerum region in a stepwise manner. Five similar specimens were used for a comparative transcranial approach. The osseous anatomy was examined in 32 high-resolution multislice CT studies and 1 disarticulated skull. Representative cases were selected to illustrate the application of the findings.RESULTSThe pterygosphenoidal fissure is the synchondrosis between the lacerum process of the pterygoid bone and the floor of the sphenoid bone. It constantly converges with the posterior end of the vidian canal at a 45° angle, and its posterolateral end points directly to the lacerum foramen. The pterygoid tubercle separates the vidian canal from the pterygosphenoidal fissure, and forms the anterior wall of the lower part of the foramen lacerum. The lingual process, which forms the lateral wall of the foramen lacerum, was identified in 53 of 64 sides and featured an average height of 5 mm. The mandibular strut separates the foramen lacerum from the foramen ovale and had an average width of 5 mm.CONCLUSIONSThis study provides relevant surgical landmarks and a systematic approach to the foramen lacerum by defining anterior, medial, lateral, and inferior walls that may facilitate its safe exposure for effective removal of lesions while minimizing the risk of injury to the internal carotid artery.

Endoscopic endonasal transoculomotor triangle approach for adenomas invading the parapeduncular space: surgical anatomy, technical nuances, and case series.

OBJECTIVE: Pituitary adenomas may extend into the parapeduncular space by invading through the roof of the cavernous sinus. Currently, a transcranial approach is the preferred choice, with or without the combination of an endonasal approach. In this paper the authors present a novel surgical approach that takes advantage of the natural corridor provided by the tumor to further open the oculomotor triangle and resect tumor extension into the parapeduncular space. METHODS: Six injected specimens were used to demonstrate in detail the surgical anatomy related to the approach. Four cases in which the proposed approach was used were retrospectively reviewed. RESULTS: From a technical perspective, the first step involves accessing the superior compartment of the cavernous sinus. The interclinoid ligament should be identified and the dura forming the oculomotor triangle exposed. The oculomotor dural opening may be then extended posteriorly toward the posterior petroclinoidal ligament and inferolaterally toward the anterior petroclinoidal ligament. The oculomotor nerve should then be identified; in this series it was displaced superomedially in all 4 cases. The posterior communicating artery should also be identified to avoid its injury. In all 4 cases, the tumor invading the parapeduncular space was completely removed. There were no vascular injuries and only 1 patient had a partial oculomotor nerve palsy that completely resolved in 2 weeks. CONCLUSIONS: The endoscopic endonasal transoculomotor approach is an original alternative for removal of tumor extension into the parapeduncular space in a single procedure. The surgical corridor is increased by opening the dura of the oculomotor triangle and by working below and lateral to the cisternal segment of the oculomotor nerve.

Anatomic Considerations for Sinonasal and Ventral Skull Base Malignancy.

Malignancies of the sinonasal region and ventral skull base include a varied group of uncommon tumors that are a challenge to treat. These malignancies, with few exceptions, often present late because of their insidious growth and bland symptomatology. As with malignancies of other sites, the primary goal in surgical management is complete resection with negative margins. This presents a unique surgical challenge in that these lesions lie within a region of densely populated anatomic real estate. This fact reinforces the importance of complete preoperative work-up and a sound anatomic understanding. This article discusses key anatomic regions and their importance from an endonasal perspective.

Clinical and Imaging Evaluation of Transuncus Selective Amygdalohippocampectomy.

BACKGROUND: Various reports have described the transuncus (TU) approach as a selective route to the amygdala and hippocampus, but this approach has not yet been submitted to solid postoperative imaging analysis. The objective of this study was to evaluate the anatomy, surgical technique, postoperative imaging analysis, and outcome in a series of patients with temporal lobe epilepsy who underwent selective amigdalohippocampectomy via a TU approach. METHODS: This was a prospective study of 25 consecutive patients who underwent selective amigdalohippocampectomy through a TU approach. The temporal stem and temporal pole were evaluated through different modalities of 3-Tesla magnetic resonance imaging, including tractography of optic radiation (OR), uncinate fascicle, and inferior fronto-occipital fascicle. Visual field analysis was performed with automated perimetry. RESULTS: The mean age was 40 ± 8.21 years, and mean follow-up was 26.44 + 12.58 months. Postoperatively, 21 patients (84%) were classified as Engel I (good seizure control). Diffusion tensor imaging (DTI) data showed that 78.2% of patients had some structural damage to the temporal stem and fibers of the uncinate fascicle were identified postoperatively in only 3 patients (13.04%). The inferior fronto-occipital fascicle was identified in 18 patients (78.3%); however, subsequent DTI analysis of the remaining fibers showed them to be damaged. Integrity of the OR did not differ between these 2 groups. CONCLUSIONS: A TU approach is a feasible and efficient approach to selective amigdalohippocampectomy for surgical treatment of temporal lobe epilepsy. Postoperative DTI analysis suggests that a TU approach results in more injury to the temporal stem and its associated white matter fiber tracts than expected by previous anatomic studies; however, it was efficient in preserving OR.